Resistivity inversion in 2-D anisotropic media: numerical experiments
NASA Astrophysics Data System (ADS)
Wiese, Timothy; Greenhalgh, Stewart; Zhou, Bing; Greenhalgh, Mark; Marescot, Laurent
2015-04-01
Many rocks and layered/fractured sequences have a clearly expressed electrical anisotropy although it is rare in practice to incorporate anisotropy into resistivity inversion. In this contribution, we present a series of 2.5-D synthetic inversion experiments for various electrode configurations and 2-D anisotropic models. We examine and compare the image reconstructions obtained using the correct anisotropic inversion code with those obtained using the false but widely used isotropic assumption. Superior reconstruction in terms of reduced data misfit, true anomaly shape and position, and anisotropic background parameters were obtained when the correct anisotropic assumption was employed for medium to high coefficients of anisotropy. However, for low coefficient values the isotropic assumption produced better-quality results. When an erroneous isotropic inversion is performed on medium to high level anisotropic data, the images are dominated by patterns of banded artefacts and high data misfits. Various pole-pole, pole-dipole and dipole-dipole data sets were investigated and evaluated for the accuracy of the inversion result. The eigenvalue spectra of the pseudo-Hessian matrix and the formal resolution matrix were also computed to determine the information content and goodness of the results. We also present a data selection strategy based on high sensitivity measurements which drastically reduces the number of data to be inverted but still produces comparable results to that of the comprehensive data set. Inversion was carried out using transversely isotropic model parameters described in two different co-ordinate frames for the conductivity tensor, namely Cartesian versus natural or eigenframe. The Cartesian frame provided a more stable inversion product. This can be simply explained from inspection of the eigenspectra of the pseudo-Hessian matrix for the two model descriptions.
ELRIS2D: A MATLAB Package for the 2D Inversion of DC Resistivity/IP Data
NASA Astrophysics Data System (ADS)
Akca, Irfan
2016-04-01
ELRIS2D is an open source code written in MATLAB for the two-dimensional inversion of direct current resistivity (DCR) and time domain induced polarization (IP) data. The user interface of the program is designed for functionality and ease of use. All available settings of the program can be reached from the main window. The subsurface is discre-tized using a hybrid mesh generated by the combination of structured and unstructured meshes, which reduces the computational cost of the whole inversion procedure. The inversion routine is based on the smoothness constrained least squares method. In order to verify the program, responses of two test models and field data sets were inverted. The models inverted from the synthetic data sets are consistent with the original test models in both DC resistivity and IP cases. A field data set acquired in an archaeological site is also used for the verification of outcomes of the program in comparison with the excavation results.
2-D Joint Structural Inversion of Cross-hole Electrical Resistance and Ground Penetrating Radar Data
NASA Astrophysics Data System (ADS)
Bouchedda, Abderrezak; Chouteau, Michel; Giroux, Bernard
2010-05-01
We present a joint structural inversion algorithm for cross-hole electrical resistance tomography (ERT) and cross-hole radar travel time tomography (RTT). The algorithm proceeds by combining the exchange of structural information and a regularization method that consists of imposing an L1-norm penalty in the wavelet domain. The minimization of the L1-norm penalty is carried out using an iterative soft-thresholding algorithm. The thresholds are estimated by maximizing a structural similarity criterion, which is a function of the two (ERT and RTT) inverted models. To solve this optimization subproblem, we used the simultaneous perturbation stochastic approach. Besides, the regularization in the wavelet basis allows for the possibility of sharp discontinuities superimposed on a smoothly varying background. Hence the structural information is extracted from each model using a Canny edge detector. The detected edge is used to construct a weighting matrix that is applied to alter the smoothness matrix constraint. To validate our methodology and its implementation, responses from two models were modelled. Experiments demonstrate that the proposed approach improves the spatial resolution and quantitative estimation of physical parameters. In addition, in comparison with joint structural inversion with only the exchange of structural information, our method avoids undesirable bias introduced by the exchange of structural information when the boundaries are near each other. Finally, the proposed algorithm will be applied to real data in the near future to evaluate its performance.
NASA Astrophysics Data System (ADS)
Rosas Carbajal, Marina; Linde, Niklas; Kalscheurer, Thomas; Vrugt, Jasper
2013-04-01
Stochastic inversions based on Markov chain Monte Carlo (MCMC) methods help to characterize the inherent non-uniqueness of non-linear inverse problems. By stating the inverse problem as an inference problem, the emphasis is placed on sampling the posterior probability density function (PDF) of the model parameters, which comprise all possible models that explain the data and satisfy a priori information. The drawback is that for non-linear problems involving many model parameters, MCMC algorithms may take great time to converge. This is why most geophysical applications based on MCMC rely on 1D assumptions. We present here the first fully 2D MCMC inversion of radio magnetotelluric (RMT) and electrical resistivity tomography (ERT) data, using up to 300 model parameters. We demonstrate that stochastic inversion of high-dimensional problems necessitates prior constraints on the model structure to yield meaningful results. In particular, we focus on two popular types of regularization: smoothly varying model parameters and compact anomalies. To do so, we invert not only for the PDF of each model parameter, but also for two hyper-parameters: the variance of the data errors and a trade-off between data fit and model structure. The derived model uncertainties are compared with deterministic most-squares inversions and we analyze how these uncertainties evolve when jointly inverting RMT and ERT data. Finally, we present a field application to characterize the geometry of an aquifer in Sweden. The numerical examples illustrate that model regularization not only decreases the uncertainty of the model parameters, but also accelerates the convergence of the MCMC algorithm. A drawback is that the regularization may lead to posterior PDFs that do not contain features in the true model that are insensitive to data. We also find that joint inversion of different types of geophysical data helps to better constrain the subsurface models. Results of the field data inversions are in
Irreversibility-inversions in 2D turbulence
NASA Astrophysics Data System (ADS)
Bragg, Andrew; de Lillo, Filippo; Boffetta, Guido
2016-11-01
We consider a recent theoretical prediction that for inertial particles in 2D turbulence, the nature of the irreversibility of their pair dispersion inverts when the particle inertia exceeds a certain value. In particular, when the particle Stokes number, St , is below a certain value, the forward-in-time (FIT) dispersion should be faster than the backward-in-time (BIT) dispersion, but for St above this value, this should invert so that BIT becomes faster than FIT dispersion. This non-trivial behavior arises because of the competition between two physically distinct irreversibility mechanisms that operate in different regimes of St . In 3D turbulence, both mechanisms act to produce faster BIT than FIT dispersion, but in 2D, the two mechanisms have opposite effects because of the inverse energy cascade in the turbulent velocity field. We supplement the qualitative argument given by Bragg et al. by deriving quantitative predictions of this effect in the short-time dispersion limit. These predictions are then confirmed by results of inertial particle dispersion in a direct numerical simulation of 2D turbulence.
Efficient 2d full waveform inversion using Fortran coarray
NASA Astrophysics Data System (ADS)
Ryu, Donghyun; Kim, ahreum; Ha, Wansoo
2016-04-01
We developed a time-domain seismic inversion program using the coarray feature of the Fortran 2008 standard to parallelize the algorithm. We converted a 2d acoustic parallel full waveform inversion program with Message Passing Interface (MPI) to a coarray program and examined performance of the two inversion programs. The results show that the speed of the waveform inversion program using the coarray is slightly faster than that of the MPI version. The standard coarray lacks features for collective communication; however, it can be improved in following standards since it is introduced recently. The parallel algorithm can be applied for 3D seismic data processing.
Image Appraisal for 2D and 3D Electromagnetic Inversion
Alumbaugh, D.L.; Newman, G.A.
1999-01-28
Linearized methods are presented for appraising image resolution and parameter accuracy in images generated with two and three dimensional non-linear electromagnetic inversion schemes. When direct matrix inversion is employed, the model resolution and posterior model covariance matrices can be directly calculated. A method to examine how the horizontal and vertical resolution varies spatially within the electromagnetic property image is developed by examining the columns of the model resolution matrix. Plotting the square root of the diagonal of the model covariance matrix yields an estimate of how errors in the inversion process such as data noise and incorrect a priori assumptions about the imaged model map into parameter error. This type of image is shown to be useful in analyzing spatial variations in the image sensitivity to the data. A method is analyzed for statistically estimating the model covariance matrix when the conjugate gradient method is employed rather than a direct inversion technique (for example in 3D inversion). A method for calculating individual columns of the model resolution matrix using the conjugate gradient method is also developed. Examples of the image analysis techniques are provided on 2D and 3D synthetic cross well EM data sets, as well as a field data set collected at the Lost Hills Oil Field in Central California.
2D Inversion of DCR and Time Domain IP data: an example from ore exploration
NASA Astrophysics Data System (ADS)
Adrian, J.; Tezkan, B.
2015-12-01
Ore deposits often appear as disseminated sulfidic materials. Exploring these deposits with the Direct Current Resistivity (DCR) method alone is challenging because the resistivity signatures caused by disseminated material is often hard to detect. The Time-domain Induced Polarization (TDIP) method, on the other hand, is qualified to detect areas with disseminated sulfidic ores due to large electrode polarization effects which result in large chargeability anomalies. By employing both methods we gain information about both, the resistivity and the chargeability distribution of the subsurface.On the poster we present the current state of the development of a 2D smoothness constraint inversion algorithm for DCR and TDIP data. The implemented forward algorithm uses a Finite Element approach with an unstructured mesh. The model parameters resistivity and chargeability are connected by either a simple conductivity pertubation approach or a complex conductivity approach.As a case study, the 2D inversion results of DCR/TDIP and RMT data obtained during a survey on a sulfidic copper ore deposit in Turkey are presented. The presence of an ore deposit is indicated by areas with low resistivity and significantly high chargeability in the inversion models.This work is part of the BMBF/TUEBITAK funded project ``Two-dimensional joint interpretation of Radiomagnetotellurics (RMT), Direct Current Resistivity (DCR) and Induced Polarization (IP) data: an example from ore exploration''.
Sensitivity of 2-D complex resistivity measurements to subsurface anisotropy
NASA Astrophysics Data System (ADS)
Kenkel, J.; Kemna, A.
2016-11-01
In general, the complex electrical resistivity in the subsurface is anisotropic. Despite this, algorithms for the tomographic inversion of complex resistivity data commonly assume isotropy, mainly due to the lack of anisotropic modelling and inversion schemes, potentially leading to artifacts in the inversion results in the presence of anisotropy. The development of an effective anisotropic complex resistivity inversion algorithm which utilizes the gradient information of some cost function benefits from understanding the characteristics of the problem's sensitivities, i.e., the partial derivative of impedance data with respect to the complex conductivities in the different spatial directions, as well as with respect to the different ratios of complex conductivities, i.e., the different anisotropy ratios. We here derive expressions for these sensitivities and, based on a 2.5-D finite-element modelling algorithm, we compute and discuss sensitivity distributions as well as measurement response curves of typical surface and cross-borehole measurement configurations for 2-D subsurface anisotropic complex resistivity distributions. Depending on the electrode layout and measurement configuration, the sensitivity with respect to the conductivity in a particular direction shows a unique pattern, while for other directions sensitivity patterns are qualitatively similar. These sensitivity characteristics translate into important equivalences between impedance responses of local anisotropic and isotropic anomalies, for both magnitude and phase. Accordingly, with collinear surface arrays only the complex conductivity in the direction of the electrode layout can be unambiguously resolved, and with cross-borehole arrays only the conductivity in the vertical direction, provided an in-hole current injection is used. Nevertheless, anisotropy ratios involving these resolvable conductivity components are likewise detectable. The distinct shape of the measurement response curves
Sensitivity of 2-D complex resistivity measurements to subsurface anisotropy
NASA Astrophysics Data System (ADS)
Kenkel, J.; Kemna, A.
2017-02-01
In general, the complex electrical resistivity in the subsurface is anisotropic. Despite this, algorithms for the tomographic inversion of complex resistivity data commonly assume isotropy, mainly due to the lack of anisotropic modelling and inversion schemes, potentially leading to artefacts in the inversion results in the presence of anisotropy. The development of an effective anisotropic complex resistivity inversion algorithm which utilizes the gradient information of some cost function benefits from understanding the characteristics of the problem's sensitivities, that is, the partial derivative of the impedance forward response with respect to the complex conductivities in the different spatial directions, as well as with respect to the different ratios of complex conductivities, that is, the different anisotropy ratios. We here derive expressions for these sensitivities and, based on a 2.5-D finite-element modelling algorithm, we compute and discuss sensitivity distributions as well as measurement response curves of typical surface and cross-borehole measurement configurations for 2-D subsurface anisotropic complex resistivity distributions. Depending on the electrode layout and measurement configuration, the sensitivity with respect to the conductivity in a particular direction shows a unique pattern, while for other directions sensitivity patterns are qualitatively similar. These sensitivity characteristics translate into important equivalences between impedance responses of local anisotropic and isotropic anomalies, for both magnitude and phase. Accordingly, with collinear surface arrays only the complex conductivity in the direction of the electrode layout can be unambiguously resolved, and with cross-borehole arrays only the conductivity in the vertical direction, provided an in-hole current injection is used. Nevertheless, anisotropy ratios involving these resolvable conductivity components are likewise detectable. The distinct shape of the measurement
Full-waveform inversion in 2D VTI media
NASA Astrophysics Data System (ADS)
Kamath, Nishant
Full-waveform inversion (FWI) is a technique designed to produce a high-resolution model of the subsurface by using information contained in entire seismic waveforms. This thesis presents a methodology for FWI in elastic VTI (transversely isotropic with a vertical axis of symmetry) media and discusses synthetic results for heterogeneous VTI models. First, I develop FWI for multicomponent data from a horizontally layered VTI model. The reflectivity method, which permits computation of only PP reflections or a combination of PP and PSV events, is employed to model the data. The Gauss-Newton technique is used to invert for the interval Thomsen parameters, while keeping the densities fixed at the correct values. Eigenvalue/eigenvector decompostion of the Hessian matrix helps analyze the sensitivity of the objective function to the model parameters. Whereas PP data alone are generally sufficient to constrain all four Thomsen parameters even for conventional spreads, including PS reflections provides better constraints, especially for the deeper part of the model. Next, I derive the gradients of the FWI objective function with respect to the stiffness coefficients of arbitrarily anisotropic media by employing the adjoint-state method. From these expressions, it is straightforward to compute the gradients for parameters of 2D heterogeneous VTI media. FWI is implemented in the time domain with the steepest-descent method used to iteratively update the model. The algorithm is tested on transmitted multicomponent data generated for Gaussian anomalies in Thomsen parameters embedded in homogeneous VTI media. To test the sensitivity of the objective function to different model parameters, I derive an an- alytic expression for the Frechet kernel of FWI for arbitrary anisotropic symmetry by using the Born approximation and asymptotic Green's functions. The amplitude of the kernel, which represents the radiation pattern of a secondary source (that source describes a perturbation
NASA Astrophysics Data System (ADS)
Ariani, Elsi; Srigutomo, Wahyu
2016-08-01
One-dimensional (1D) and two-dimensional (2D) magnetotelluric data inversion were conducted to reveal the subsurface resistivity structure beneath the eastern part of a volcano in Central Java, Indonesia. Fifteen magnetotelluric sounding data spanning two lines of investigation were inverted using Occam's inversion scheme. The result depict that there are extensively conductive layer (2-10 ohm meter) below the volcanic overburden. This conductive layer is interpreted as the clay cap resulted from thermal alteration. A higher resistivity layer (10-80 ohm meter) underlies the clay cap and is interpreted as the reservoir whose top boundaries vary between 1000 m above and 2000 m below sea level.
NASA Astrophysics Data System (ADS)
Ray, Anandaroop; Key, Kerry; Bodin, Thomas; Myer, David; Constable, Steven
2014-12-01
We apply a reversible-jump Markov chain Monte Carlo method to sample the Bayesian posterior model probability density function of 2-D seafloor resistivity as constrained by marine controlled source electromagnetic data. This density function of earth models conveys information on which parts of the model space are illuminated by the data. Whereas conventional gradient-based inversion approaches require subjective regularization choices to stabilize this highly non-linear and non-unique inverse problem and provide only a single solution with no model uncertainty information, the method we use entirely avoids model regularization. The result of our approach is an ensemble of models that can be visualized and queried to provide meaningful information about the sensitivity of the data to the subsurface, and the level of resolution of model parameters. We represent models in 2-D using a Voronoi cell parametrization. To make the 2-D problem practical, we use a source-receiver common midpoint approximation with 1-D forward modelling. Our algorithm is transdimensional and self-parametrizing where the number of resistivity cells within a 2-D depth section is variable, as are their positions and geometries. Two synthetic studies demonstrate the algorithm's use in the appraisal of a thin, segmented, resistive reservoir which makes for a challenging exploration target. As a demonstration example, we apply our method to survey data collected over the Scarborough gas field on the Northwest Australian shelf.
Hydrates in the California Borderlands: 2D CSEM inversion results from towed and seafloor arrays
NASA Astrophysics Data System (ADS)
Kannberg, P. K.; Constable, S.; Key, K.
2013-12-01
Methane hydrate, an ice-like solid clathrate of methane and water, forms in shallow continental slope sediments, and is both a potential energy source and geologic hazard. Traditionally, methane hydrate presence is inferred from a seismically detected bathymetry tracking velocity inversion, known as the bottom-simulating reflector (BSR). However the BSR is an indicator of free gas at the base of the hydrate stability zone, and not an indicator of hydrate. As such, seismic methods are limited in their capacity to identify and quantify hydrate presence and concentration. Controlled source electromagnetic (CSEM) methods are sensitive to, and are able to directly detect, the presence of electrically resistive methane hydrate and free gas. Additionally, because shallow resistors can mimic deeper resistors in seafloor instruments, understanding the shallow sediment structure can inform deeper crustal modeling. We conducted two CSEM surveys in the San Nicolas Basin, located 150km west of San Diego where a BSR was identified from legacy seismics. Both surveys were conducted using a deep-towed EM transmitter followed by 4 towed 3-axis electric field receivers spaced every 200 m from 400-1000 m behind the transmitter. Either a half-hertz or quarter-hertz modified square wave was transmitted on a 200 ampere, 100 m dipole that was flown between 50 and 100m above the seafloor. The short transmitter-receiver offset allows resolution of shallow structure (less than 1km below seafloor), while the longer transmitter-seafloor receiver resolves deeper structure. Between the two surveys, 27 seafloor receivers were deployed and ~150km of lines were towed, including 5 transects of the basin coincident with legacy seismic lines, and a short-offset repeatability study. Initial 1D modeling showed the presence of a resistor coincident with the BSR. Further 2D inversions using the MARE2DEM inversion program were run for the towed array. These inversions show a 4 ohm-m resistor in the central
Efficiency of Pareto joint inversion of 2D geophysical data using global optimization methods
NASA Astrophysics Data System (ADS)
Miernik, Katarzyna; Bogacz, Adrian; Kozubal, Adam; Danek, Tomasz; Wojdyła, Marek
2016-04-01
Pareto joint inversion of two or more sets of data is a promising new tool of modern geophysical exploration. In the first stage of our investigation we created software enabling execution of forward solvers of two geophysical methods (2D magnetotelluric and gravity) as well as inversion with possibility of constraining solution with seismic data. In the algorithm solving MT forward solver Helmholtz's equations, finite element method and Dirichlet's boundary conditions were applied. Gravity forward solver was based on Talwani's algorithm. To limit dimensionality of solution space we decided to describe model as sets of polygons, using Sharp Boundary Interface (SBI) approach. The main inversion engine was created using Particle Swarm Optimization (PSO) algorithm adapted to handle two or more target functions and to prevent acceptance of solutions which are non - realistic or incompatible with Pareto scheme. Each inversion run generates single Pareto solution, which can be added to Pareto Front. The PSO inversion engine was parallelized using OpenMP standard, what enabled execution code for practically unlimited amount of threads at once. Thereby computing time of inversion process was significantly decreased. Furthermore, computing efficiency increases with number of PSO iterations. In this contribution we analyze the efficiency of created software solution taking under consideration details of chosen global optimization engine used as a main joint minimization engine. Additionally we study the scale of possible decrease of computational time caused by different methods of parallelization applied for both forward solvers and inversion algorithm. All tests were done for 2D magnetotelluric and gravity data based on real geological media. Obtained results show that even for relatively simple mid end computational infrastructure proposed solution of inversion problem can be applied in practice and used for real life problems of geophysical inversion and interpretation.
Resolving spectral information from time domain induced polarization data through 2-D inversion
NASA Astrophysics Data System (ADS)
Fiandaca, Gianluca; Ramm, James; Binley, Andrew; Gazoty, Aurélie; Christiansen, Anders Vest; Auken, Esben
2013-02-01
Field-based time domain (TD) induced polarization (IP) surveys are usually modelled by taking into account only the integral chargeability, thus disregarding spectral content. Furthermore, the effect of the transmitted waveform is commonly neglected, biasing inversion results. Given these limitations of conventional approaches, a new 2-D inversion algorithm has been developed using the full voltage decay of the IP response, together with an accurate description of the transmitter waveform and receiver transfer function. This allows reconstruction of the spectral information contained in the TD decay series. The inversion algorithm is based around a 2-D complex conductivity kernel that is computed over a range of frequencies and converted to the TD through a fast Hankel transform. Two key points in the implementation ensure that computation times are minimized. First, the speed of the Jacobian computation, time transformed from frequency domain through the same transformation adopted for the forward response is optimized. Secondly, the reduction of the number of frequencies where the forward response and Jacobian are calculated: cubic splines are used to interpolate the responses to the frequency sampling necessary in the fast Hankel transform. These features, together with parallel computation, ensure inversion times comparable with those of direct current algorithms. The algorithm has been developed in a laterally constrained inversion scheme, and handles both smooth and layered inversions; the latter being helpful in sedimentary environments, where quasi-layered models often represent the actual geology more accurately than smooth minimum-structure models. In the layered inversion approach, a general method to derive the thickness derivative from the complex conductivity Jacobian is also proposed. One synthetic example of layered inversion and one field example of smooth inversion show the capability of the algorithm and illustrates a complete uncertainty
Simultaneous elastic parameter inversion in 2-D/3-D TTI medium combined later arrival times
NASA Astrophysics Data System (ADS)
Bai, Chao-ying; Wang, Tao; Yang, Shang-bei; Li, Xing-wang; Huang, Guo-jiao
2016-04-01
Traditional traveltime inversion for anisotropic medium is, in general, based on a "weak" assumption in the anisotropic property, which simplifies both the forward part (ray tracing is performed once only) and the inversion part (a linear inversion solver is possible). But for some real applications, a general (both "weak" and "strong") anisotropic medium should be considered. In such cases, one has to develop a ray tracing algorithm to handle with the general (including "strong") anisotropic medium and also to design a non-linear inversion solver for later tomography. Meanwhile, it is constructive to investigate how much the tomographic resolution can be improved by introducing the later arrivals. For this motivation, we incorporated our newly developed ray tracing algorithm (multistage irregular shortest-path method) for general anisotropic media with a non-linear inversion solver (a damped minimum norm, constrained least squares problem with a conjugate gradient approach) to formulate a non-linear inversion solver for anisotropic medium. This anisotropic traveltime inversion procedure is able to combine the later (reflected) arrival times. Both 2-D/3-D synthetic inversion experiments and comparison tests show that (1) the proposed anisotropic traveltime inversion scheme is able to recover the high contrast anomalies and (2) it is possible to improve the tomographic resolution by introducing the later (reflected) arrivals, but not as expected in the isotropic medium, because the different velocity (qP, qSV and qSH) sensitivities (or derivatives) respective to the different elastic parameters are not the same but are also dependent on the inclination angle.
NASA Astrophysics Data System (ADS)
Randeria, Mohit; Banerjee, Sumilan; Rowland, James
2015-09-01
Most theoretical studies of chiral magnetism, and the resulting spin textures, have focused on 3D systems with broken bulk inversion symmetry, where skyrmions are stabilized by easy-axis anisotropy. In this talk I will describe our results on 2D and quasi-2D systems with broken surface inversion, where we find [1] that skyrmion crystals are much more stable than in 3D, especially for the case of easy-plane anisotropy. These results are of particular interest for thin films, surfaces, and oxide interfaces [2], where broken surface-inversion symmetry and Rashba spin-orbit coupling naturally lead to both the chiral Dzyaloshinskii-Moriya (DM) interaction and to easy-plane compass anisotropy. I will then turn to systems that break both bulk and surface inversion, resulting in two distinct DM terms arising from Dresselhaus and Rashba spin-orbit coupling. I will describe [3] the evolution of the skyrmion structure and of the phase diagram as a function of the ratio of Dresselhaus and Rashba terms, which can be tuned by varying film thickness and strain. [1] S. Banerjee, J. Rowland, O. Erten, and M. Randeria, PRX 4, 031045 (2014). [2] S. Banerjee, O. Erten, and M. Randeria, Nature Phys. 9, 626 (2013). [3] J. Rowland, S. Banerjee and M. Randeria, (unpublished).
2D Seismic Imaging of Elastic Parameters by Frequency Domain Full Waveform Inversion
NASA Astrophysics Data System (ADS)
Brossier, R.; Virieux, J.; Operto, S.
2008-12-01
Thanks to recent advances in parallel computing, full waveform inversion is today a tractable seismic imaging method to reconstruct physical parameters of the earth interior at different scales ranging from the near- surface to the deep crust. We present a massively parallel 2D frequency-domain full-waveform algorithm for imaging visco-elastic media from multi-component seismic data. The forward problem (i.e. the resolution of the frequency-domain 2D PSV elastodynamics equations) is based on low-order Discontinuous Galerkin (DG) method (P0 and/or P1 interpolations). Thanks to triangular unstructured meshes, the DG method allows accurate modeling of both body waves and surface waves in case of complex topography for a discretization of 10 to 15 cells per shear wavelength. The frequency-domain DG system is solved efficiently for multiple sources with the parallel direct solver MUMPS. The local inversion procedure (i.e. minimization of residuals between observed and computed data) is based on the adjoint-state method which allows to efficiently compute the gradient of the objective function. Applying the inversion hierarchically from the low frequencies to the higher ones defines a multiresolution imaging strategy which helps convergence towards the global minimum. In place of expensive Newton algorithm, the combined use of the diagonal terms of the approximate Hessian matrix and optimization algorithms based on quasi-Newton methods (Conjugate Gradient, LBFGS, ...) allows to improve the convergence of the iterative inversion. The distribution of forward problem solutions over processors driven by a mesh partitioning performed by METIS allows to apply most of the inversion in parallel. We shall present the main features of the parallel modeling/inversion algorithm, assess its scalability and illustrate its performances with realistic synthetic case studies.
MARE2DEM: a 2-D inversion code for controlled-source electromagnetic and magnetotelluric data
NASA Astrophysics Data System (ADS)
Key, Kerry
2016-10-01
This work presents MARE2DEM, a freely available code for 2-D anisotropic inversion of magnetotelluric (MT) data and frequency-domain controlled-source electromagnetic (CSEM) data from onshore and offshore surveys. MARE2DEM parametrizes the inverse model using a grid of arbitrarily shaped polygons, where unstructured triangular or quadrilateral grids are typically used due to their ease of construction. Unstructured grids provide significantly more geometric flexibility and parameter efficiency than the structured rectangular grids commonly used by most other inversion codes. Transmitter and receiver components located on topographic slopes can be tilted parallel to the boundary so that the simulated electromagnetic fields accurately reproduce the real survey geometry. The forward solution is implemented with a goal-oriented adaptive finite-element method that automatically generates and refines unstructured triangular element grids that conform to the inversion parameter grid, ensuring accurate responses as the model conductivity changes. This dual-grid approach is significantly more efficient than the conventional use of a single grid for both the forward and inverse meshes since the more detailed finite-element meshes required for accurate responses do not increase the memory requirements of the inverse problem. Forward solutions are computed in parallel with a highly efficient scaling by partitioning the data into smaller independent modeling tasks consisting of subsets of the input frequencies, transmitters and receivers. Non-linear inversion is carried out with a new Occam inversion approach that requires fewer forward calls. Dense matrix operations are optimized for memory and parallel scalability using the ScaLAPACK parallel library. Free parameters can be bounded using a new non-linear transformation that leaves the transformed parameters nearly the same as the original parameters within the bounds, thereby reducing non-linear smoothing effects. Data
Skyrmions in quasi-2D chiral magnets with broken bulk and surface inversion symmetry
NASA Astrophysics Data System (ADS)
Rowland, James; Banerjee, Sumilan; Randeria, Mohit
2015-03-01
Most theoretical studies of skyrmions have focused on chiral magnets with broken bulk inversion symmetry, stabilized by easy-axis anisotropy. Recently, we considered 2D systems with broken surface inversion and showed that skyrmion crystals are more stable than in 3D, pointing out the importance of easy-plane anisotropy. In the present work we investigate quasi-2D systems which break both bulk and surface inversion symmetry. The Landau-Ginzburg free energy functional thus contains two Dzyloshinskii-Moriya terms of strength DD and DR arising from Dresselhaus and Rashba spin-orbit coupling respectively. We trace the evolution of the phase diagram as DD /DR is varied, and find that skyrmions are increasingly destabilized with respect to the cone phase as DD increases relative to DR. We find an evolution from vortex-like skyrmions in the pure Dresselhaus limit to hedgehog-like skyrmions in the pure Rashba limit. We discuss the relevance of these results to existing experiments and the prospects of tuning the ratio of Dresselhaus and Rashba spin-orbit coupling via film thickness and strain. Supported by NSF DMR-1410364 (J.R. and M.R.) and DOE-BES DE-SC0005035 (S.B.)
Pareto Joint Inversion of 2D Magnetotelluric and Gravity Data — Towards Practical Applications
NASA Astrophysics Data System (ADS)
Miernik, Katarzyna; Bogacz, Adrian; Kozubal, Adam; Danek, Tomasz; Wojdyła, Marek
2016-10-01
In this paper, a Pareto inversion based global optimization approach, to obtain results of joint inversion of two types of geophysical data sets, is formulated. 2D magnetotelluric and gravity data were used for tests, but presented solution is flexible enough to be used for combination of any kind of two or more target functions, as long as misfits can be calculated and forward problems solved. To minimize dimensionality of the solution, space and introduce straightforward regularization Sharp Boundary Interface (SBI) method was applied. As a main optimization engine, Particle Swarm Optimization (PSO) was used. Synthetic examples based on a real geological model were used to test proposed approach and show its usefulness in practical applications.
NASA Astrophysics Data System (ADS)
Li, Jinghe; Song, Linping; Liu, Qing Huo
2016-02-01
A simultaneous multiple frequency contrast source inversion (CSI) method is applied to reconstructing hydrocarbon reservoir targets in a complex multilayered medium in two dimensions. It simulates the effects of a salt dome sedimentary formation in the context of reservoir monitoring. In this method, the stabilized biconjugate-gradient fast Fourier transform (BCGS-FFT) algorithm is applied as a fast solver for the 2D volume integral equation for the forward computation. The inversion technique with CSI combines the efficient FFT algorithm to speed up the matrix-vector multiplication and the stable convergence of the simultaneous multiple frequency CSI in the iteration process. As a result, this method is capable of making quantitative conductivity image reconstruction effectively for large-scale electromagnetic oil exploration problems, including the vertical electromagnetic profiling (VEP) survey investigated here. A number of numerical examples have been demonstrated to validate the effectiveness and capacity of the simultaneous multiple frequency CSI method for a limited array view in VEP.
The inversion of 2D NMR relaxometry data using L1 regularization
NASA Astrophysics Data System (ADS)
Zhou, Xiaolong; Su, Guanqun; Wang, Lijia; Nie, Shengdong; Ge, Xinmin
2017-02-01
NMR relaxometry has been used as a powerful tool to study molecular dynamics. Many algorithms have been developed for the inversion of 2D NMR relaxometry data. Unlike traditional algorithms implementing L2 regularization, high order Tikhonov regularization or iterative regularization, L1 penalty term is involved to constrain the sparsity of resultant spectra in this paper. Then fast iterative shrinkage-thresholding algorithm (FISTA) is proposed to solve the L1 regularization problem. The effectiveness, noise vulnerability and practical utility of the proposed algorithm are analyzed by simulations and experiments. The results demonstrate that the proposed algorithm has a more excellent capability to reveal narrow peaks than traditional inversion algorithms. The L1 regularization implemented by our algorithm can be a useful complementary to the existing algorithms.
NASA Astrophysics Data System (ADS)
Neyamadpour, Ahmad; Taib, Samsudin; Wan Abdullah, W. A. T.
2009-11-01
MATLAB is a high-level matrix/array language with control flow statements and functions. MATLAB has several useful toolboxes to solve complex problems in various fields of science, such as geophysics. In geophysics, the inversion of 2D DC resistivity imaging data is complex due to its non-linearity, especially for high resistivity contrast regions. In this paper, we investigate the applicability of MATLAB to design, train and test a newly developed artificial neural network in inverting 2D DC resistivity imaging data. We used resilient propagation to train the network. The model used to produce synthetic data is a homogeneous medium of 100 Ω m resistivity with an embedded anomalous body of 1000 Ω m. The location of the anomalous body was moved to different positions within the homogeneous model mesh elements. The synthetic data were generated using a finite element forward modeling code by means of the RES2DMOD. The network was trained using 21 datasets and tested on another 16 synthetic datasets, as well as on real field data. In field data acquisition, the cable covers 120 m between the first and the last take-out, with a 3 m x-spacing. Three different electrode spacings were measured, which gave a dataset of 330 data points. The interpreted result shows that the trained network was able to invert 2D electrical resistivity imaging data obtained by a Wenner-Schlumberger configuration rapidly and accurately.
Deep structure of Eastern part of Bandung Basin based on 2D resistivity structure
NASA Astrophysics Data System (ADS)
Harja, Asep
2013-09-01
Bandung basin is an intramontane basin located in West Java, extending from west to east along 35 km and north to south along 15 km distance, with elevation of 660-680 m. The plain in the eastern part is the basin center with lake deposit as primary sediment filling the basin. Investigation of the subsurface structure and thickness of the basin is the main topic in this research. Beside the deeper structure of the basin, the shallow structure is also very important to be revealed since human activities are concentrated in this part. The latter is supposed to explain phenomenon related to the flood and drought that frequently occur in the area. Controlled-source audio-frequency magneto telluric (CSAMT) is a highly effective electromagnetic (EM) method to deploy in this area. Its robustness toward electromagnetic noises related to human and industrial activities particularly in the eastern part of the basin is the strong point of this method. It uses a grounded horizontal electric dipole as artificial source of electromagnetic signal that ensures data with a high signal to noise (S/N) ratio. This method is capable to map subsurface resistivity structure with high sensitivity to resistivity contras and deeper penetration. 1D inversion scheme was used to the far-field component of CSAMT data (plane wave assumption) in order to obtain resistivity cross-sections that are more suitable with the basin's structure complexity. The results show that until the depth of more than 200 m, no high resistivity structure is found. This unlikely indicated the presence of volcanic rocks beneath the area. The subsurface resistivity distribution is dominated by tens of Om, indicating that the basement comprises deep marine sediment. In addition, clay lens are also indicated in the resulting resistivity structure. Based on 2D view of resistivity cross-sections based 1D inverted and 2D inversion, it is found that a low resistivity elongation extends in southeast-northwest direction at
2D resistivity method in delineating subsurface problems in urban area
NASA Astrophysics Data System (ADS)
Nordiana, M. M.; Saad, Rosli; Teh Saufia, A. H. A.; Azwin, I. N.; Ali, Nisa'; Hidayah, Noer El
2013-05-01
2D resistivity is carried out to detect spread saturated zone and subsurface problems cause by the presence of underground river, which resulted from selected urban area at Selangor, Malaysia. Six 2D resistivity survey lines with minimum 5 m electrode spacing were executed using Pole-dipole array. Borehole was carried out at multiple locations in the study area. Subsequently, the borehole was used to verify the 2D resistivity results. Interpretation of 2D resistivity data showed a low resistivity value (< 40 ohm-m), which appears to be a zone that is fully saturated with sandy silt and this could be an influence factor the increasing water level because sandy silt is highly permeable in nature. The borehole, support the results of 2D resistivity method relating a saturated zone in the survey area. There is a good correlation between the 2D resistivity investigations and the results of borehole records.
Electrical resistivity tomography applied to a complex lava dome: 2D and 3D models comparison
NASA Astrophysics Data System (ADS)
Portal, Angélie; Fargier, Yannick; Lénat, Jean-François; Labazuy, Philippe
2015-04-01
The study of volcanic domes growth (e.g. St. Helens, Unzen, Montserrat) shows that it is often characterized by a succession of extrusion phases, dome explosions and collapse events. Lava dome eruptive activity may last from days to decades. Therefore, their internal structure, at the end of the eruption, is complex and includes massive extrusions and lava lobes, talus and pyroclastic deposits as well as hydrothermal alteration. The electrical resistivity tomography (ERT) method, initially developed for environmental and engineering exploration, is now commonly used for volcano structure imaging. Because a large range of resistivity values is often observed in volcanic environments, the method is well suited to study the internal structure of volcanic edifices. We performed an ERT survey on an 11ka years old trachytic lava dome, the Puy de Dôme volcano (French Massif Central). The analysis of a recent high resolution DEM (LiDAR 0.5 m), as well as other geophysical data, strongly suggest that the Puy de Dôme is a composite dome. 11 ERT profiles have been carried out, both at the scale of the entire dome (base diameter of ~2 km and height of 400 m) on the one hand, and at a smaller scale on the summit part on the other hand. Each profile is composed of 64 electrodes. Three different electrode spacing have been used depending on the study area (35 m for the entire dome, 10 m and 5 m for its summit part). Some profiles were performed with half-length roll-along acquisitions, in order to keep a good trade-off between depth of investigation and resolution. Both Wenner-alpha and Wenner-Schlumberger protocols were used. 2-D models of the electrical resistivity distribution were computed using RES2DINV software. In order to constrain inversion models interpretation, the depth of investigation (DOI) method was applied to those results. It aims to compute a sensitivity index on inversion results, illustrating how the data influence the model and constraining models
A 2D inverse problem of predicting boiling heat transfer in a long fin
NASA Astrophysics Data System (ADS)
Orzechowski, Tadeusz
2016-10-01
A method for the determination of local values of the heat transfer coefficient on non-isothermal surfaces was analyzed on the example of a long smooth-surfaced fin made of aluminium. On the basis of the experimental data, two cases were taken into consideration: one-dimensional model for Bi < 0.1 and two-dimensional model for thicker elements. In the case when the drop in temperature over the thickness could be omitted, the rejected local values of heat fluxes were calculated from the integral of the equation describing temperature distribution on the fin. The corresponding boiling curve was plotted on the basis of temperature gradient distribution as a function of superheat. For thicker specimens, where Bi > 0.1, the problem was modelled using a 2-D heat conduction equation, for which the boundary conditions were posed on the surface observed with a thermovision camera. The ill-conditioned inverse problem was solved using a method of heat polynomials, which required validation.
An analytical approach to estimate the number of small scatterers in 2D inverse scattering problems
NASA Astrophysics Data System (ADS)
Fazli, Roohallah; Nakhkash, Mansor
2012-07-01
This paper presents an analytical method to estimate the location and number of actual small targets in 2D inverse scattering problems. This method is motivated from the exact maximum likelihood estimation of signal parameters in white Gaussian noise for the linear data model. In the first stage, the method uses the MUSIC algorithm to acquire all possible target locations and in the next stage, it employs an analytical formula that works as a spatial filter to determine which target locations are associated to the actual ones. The ability of the method is examined for both the Born and multiple scattering cases and for the cases of well-resolved and non-resolved targets. Many numerical simulations using both the coincident and non-coincident arrays demonstrate that the proposed method can detect the number of actual targets even in the case of very noisy data and when the targets are closely located. Using the experimental microwave data sets, we further show that this method is successful in specifying the number of small inclusions.
NASA Astrophysics Data System (ADS)
Martinho, E.; Almeida, F.
2006-04-01
Aiming at defining a valid spatial contamination model, resistivity and induced polarization (IP) measurements were used to investigate contamination plumes in the vicinity of two municipal landfills (Ovar and Ílhavo). Previous geophysical surveys and underground water samples confirmed the contamination. However 2D resistivity/IP surveys enabled in obtaining a more accurate spatial model. The Ovar survey consisted of two profiles with nine Wenner soundings each; the Ílhavo survey was carried out along two individual lines using a Wenner standard pseudo-section. In both situations, negative IP values were found associated with positive IP values, which can be explained mainly by 2D or 3D geometric effects caused by the presence of the conductive plumes. The data were modelled using a 2D inversion program (RES2DINV) and the resulting resistivity and chargeability distributions were displayed as pseudo-sections. The resistivity and chargeability pseudo-sections define the contamination plumes and the sedimentary structure. These case studies illustrate the advantages of 2D resistivity/IP surveys for the mapping of shape and dimension of contamination associated with landfills.
Modeling Coastal Salinity in Quasi 2D and 3D Using a DUALEM-421 and Inversion Software.
Davies, Gareth; Huang, Jingyi; Monteiro Santos, Fernando Acacio; Triantafilis, John
2015-01-01
Rising sea levels, owing to climate change, are a threat to fresh water coastal aquifers. This is because saline intrusions are caused by increases and intensification of medium-large scale influences including sea level rise, wave climate, tidal cycles, and shifts in beach morphology. Methods are therefore required to understand the dynamics of these interactions. While traditional borehole and galvanic contact resistivity (GCR) techniques have been successful they are time-consuming. Alternatively, frequency-domain electromagnetic (FEM) induction is potentially useful as physical contact with the ground is not required. A DUALEM-421 and EM4Soil inversion software package are used to develop a quasi two- (2D) and quasi three-dimensional (3D) electromagnetic conductivity images (EMCI) across Long Reef Beach located north of Sydney Harbour, New South Wales, Australia. The quasi 2D models discern: the dry sand (<10 mS/m) associated with the incipient dune; sand with fresh water (10 to 20 mS/m); mixing of fresh and saline water (20 to 500 mS/m), and; saline sand of varying moisture (more than 500 mS/m). The quasi 3D EMCIs generated for low and high tides suggest that daily tidal cycles do not have a significant effect on local groundwater salinity. Instead, the saline intrusion is most likely influenced by medium-large scale drivers including local wave climate and morphology along this wave-dominated beach. Further research is required to elucidate the influence of spring-neap tidal cycles, contrasting beach morphological states and sea level rise.
Burgess, Ian B; Aizenberg, Joanna; Lončar, Marko
2013-12-01
Structural hierarchy and complex 3D architecture are characteristics of biological photonic designs that are challenging to reproduce in synthetic materials. Top-down lithography allows for designer patterning of arbitrary shapes, but is largely restricted to planar 2D structures. Self-assembly techniques facilitate easy fabrication of 3D photonic crystals, but controllable defect-integration is difficult. In this paper we combine the advantages of top-down and bottom-up fabrication, developing two techniques to deposit 2D-lithographically-patterned planar layers on top of or in between inverse-opal 3D photonic crystals and creating hierarchical structures that resemble the architecture of the bright green wing scales of the butterfly, Parides sesostris. These fabrication procedures, combining advantages of both top-down and bottom-up fabrication, may prove useful in the development of omnidirectional coloration elements and 3D-2D photonic crystal devices.
NASA Astrophysics Data System (ADS)
Portal, Angélie; Fargier, Yannick; Lénat, Jean-François; Labazuy, Philippe
2016-04-01
The electrical resistivity tomography (ERT) method, initially developed for environmental and engineering exploration, is now commonly used for geological structures imaging. Such structures can present complex characteristics that conventional 2D inversion processes cannot perfectly integrate. Here we present a new 3D inversion algorithm named EResI, firstly developed for levee investigation, and presently applied to the study of a complex lava dome (the Puy de Dôme volcano, France). EResI algorithm is based on a conventional regularized Gauss-Newton inversion scheme and a 3D non-structured discretization of the model (double grid method based on tetrahedrons). This discretization allows to accurately model the topography of investigated structure (without a mesh deformation procedure) and also permits a precise location of the electrodes. Moreover, we demonstrate that a complete 3D unstructured discretization limits the number of inversion cells and is better adapted to the resolution capacity of tomography than a structured discretization. This study shows that a 3D inversion with a non-structured parametrization has some advantages compared to classical 2D inversions. The first advantage comes from the fact that a 2D inversion leads to artefacts due to 3D effects (3D topography, 3D internal resistivity). The second advantage comes from the fact that the capacity to experimentally align electrodes along an axis (for 2D surveys) depends on the constrains on the field (topography...). In this case, a 2D assumption induced by 2.5D inversion software prevents its capacity to model electrodes outside this axis leading to artefacts in the inversion result. The last limitation comes from the use of mesh deformation techniques used to accurately model the topography in 2D softwares. This technique used for structured discretization (Res2dinv) is prohibed for strong topography (>60 %) and leads to a small computational errors. A wide geophysical survey was carried out
Chuang, Hsun-Jen; Chamlagain, Bhim; Koehler, Michael; Perera, Meeghage Madusanka; Yan, Jiaqiang; Mandrus, David; Tománek, David; Zhou, Zhixian
2016-03-09
We report a new strategy for fabricating 2D/2D low-resistance ohmic contacts for a variety of transition metal dichalcogenides (TMDs) using van der Waals assembly of substitutionally doped TMDs as drain/source contacts and TMDs with no intentional doping as channel materials. We demonstrate that few-layer WSe2 field-effect transistors (FETs) with 2D/2D contacts exhibit low contact resistances of ∼0.3 kΩ μm, high on/off ratios up to >10(9), and high drive currents exceeding 320 μA μm(-1). These favorable characteristics are combined with a two-terminal field-effect hole mobility μFE ≈ 2 × 10(2) cm(2) V(-1) s(-1) at room temperature, which increases to >2 × 10(3) cm(2) V(-1) s(-1) at cryogenic temperatures. We observe a similar performance also in MoS2 and MoSe2 FETs with 2D/2D drain and source contacts. The 2D/2D low-resistance ohmic contacts presented here represent a new device paradigm that overcomes a significant bottleneck in the performance of TMDs and a wide variety of other 2D materials as the channel materials in postsilicon electronics.
Chuang, Hsun -Jen; Chamlagain, Bhim; Koehler, Michael; ...
2016-02-04
Here, we report a new strategy for fabricating 2D/2D low-resistance ohmic contacts for a variety of transition metal dichalcogenides (TMDs) using van der Waals assembly of substitutionally doped TMDs as drain/source contacts and TMDs with no intentional doping as channel materials. We demonstrate that few-layer WSe2 field-effect transistors (FETs) with 2D/2D contacts exhibit low contact resistances of ~0.3 kΩ μm, high on/off ratios up to >109, and high drive currents exceeding 320 μA μm–1. These favorable characteristics are combined with a two-terminal field-effect hole mobility μFE ≈ 2 × 102 cm2 V–1 s–1 at room temperature, which increases to >2more » × 103 cm2 V–1 s–1 at cryogenic temperatures. We observe a similar performance also in MoS2 and MoSe2 FETs with 2D/2D drain and source contacts. The 2D/2D low-resistance ohmic contacts presented here represent a new device paradigm that overcomes a significant bottleneck in the performance of TMDs and a wide variety of other 2D materials as the channel materials in postsilicon electronics.« less
Numerical solution of 2D-vector tomography problem using the method of approximate inverse
NASA Astrophysics Data System (ADS)
Svetov, Ivan; Maltseva, Svetlana; Polyakova, Anna
2016-08-01
We propose a numerical solution of reconstruction problem of a two-dimensional vector field in a unit disk from the known values of the longitudinal and transverse ray transforms. The algorithm is based on the method of approximate inverse. Numerical simulations confirm that the proposed method yields good results of reconstruction of vector fields.
2D Heterostructure coatings of hBN-MoS2 layers for corrosion resistance
NASA Astrophysics Data System (ADS)
Vandana, Sajith; Kochat, Vidya; Lee, Jonghoon; Varshney, Vikas; Yazdi, Sadegh; Shen, Jianfeng; Kosolwattana, Suppanat; Vinod, Soumya; Vajtai, Robert; Roy, Ajit K.; Sekhar Tiwary, Chandra; Ajayan, P. M.
2017-02-01
Heterostructures of atomically thin 2D materials could have improved physical, mechanical and chemical properties as compared to its individual components. Here we report, the effect of heterostructure coatings of hBN and MoS2 on the corrosion behavior as compared to coatings employing the individual 2D layer compositions. The poor corrosion resistance of MoS2 (widely used as wear resistant coating) can be improved by incorporating hBN sheets. Depending on the atomic stacking of the 2D sheets, we can further engineer the corrosion resistance properties of these coatings. A detailed spectroscopy and microscopy analysis has been used to characterize the different combinations of layered coatings. Detailed DFT based calculation reveals that the effect on the electrical properties due to atomic stacking is one of the major reasons for the improvement seen in corrosion resistance.
NASA Astrophysics Data System (ADS)
Geiermann, Johannes; Schill, Eva
2010-07-01
With the aim of investigating the possibilities of magnetotelluric methods for the exploration of potential Enhanced Geothermal System (EGS) sites in the Upper Rhine valley, a 2-D magnetotelluric (MT) survey has been carried out on a 13 km long profile across the thermal anomaly in the area of the geothermal power plant of Soultz-sous-Forêts in the winter 2007/08. Despite strong artificial noise, processing using remote referencing and Sutarno phase consistent smoothing revealed significant results from 10 out of 16 sites. Indication for 1-D structures was found in the shortest periods, 2-D effects in the periods up to 40 s, and 3-D effects in the long period range. Since 3-D effects were found in the longer periods, 2-D inversion was carried out for periods smaller than 40 s. The results of the inversion are consistent with the geology of the geothermal site and distinguish well the sediments from the granitic basement including the structures given by the faults. A conductive anomaly with a resistivity of about 3 Ωm has been found at a depth down to 2000 m in the area of the Soultz and Kutzenhausen faults, which is attributed to geothermal processes.
A multiple-scale Pascal polynomial for 2D Stokes and inverse Cauchy-Stokes problems
NASA Astrophysics Data System (ADS)
Liu, Chein-Shan; Young, D. L.
2016-05-01
The polynomial expansion method is a useful tool for solving both the direct and inverse Stokes problems, which together with the pointwise collocation technique is easy to derive the algebraic equations for satisfying the Stokes differential equations and the specified boundary conditions. In this paper we propose two novel numerical algorithms, based on a third-first order system and a third-third order system, to solve the direct and the inverse Cauchy problems in Stokes flows by developing a multiple-scale Pascal polynomial method, of which the scales are determined a priori by the collocation points. To assess the performance through numerical experiments, we find that the multiple-scale Pascal polynomial expansion method (MSPEM) is accurate and stable against large noise.
NASA Astrophysics Data System (ADS)
Monnier, J.; Couderc, F.; Dartus, D.; Larnier, K.; Madec, R.; Vila, J.-P.
2016-11-01
The 2D shallow water equations adequately model some geophysical flows with wet-dry fronts (e.g. flood plain or tidal flows); nevertheless deriving accurate, robust and conservative numerical schemes for dynamic wet-dry fronts over complex topographies remains a challenge. Furthermore for these flows, data are generally complex, multi-scale and uncertain. Robust variational inverse algorithms, providing sensitivity maps and data assimilation processes may contribute to breakthrough shallow wet-dry front dynamics modelling. The present study aims at deriving an accurate, positive and stable finite volume scheme in presence of dynamic wet-dry fronts, and some corresponding inverse computational algorithms (variational approach). The schemes and algorithms are assessed on classical and original benchmarks plus a real flood plain test case (Lèze river, France). Original sensitivity maps with respect to the (friction, topography) pair are performed and discussed. The identification of inflow discharges (time series) or friction coefficients (spatially distributed parameters) demonstrate the algorithms efficiency.
Investigating the resolution of resistivity arrays using inverse theory
Beard, L.P.; Tripp, A.C.
1994-09-01
We used a fast 2-D minimum structure inverse solution to examine the ability of different resistivity arrays to resolve structures given noisy synthetic data. We found that the resistivity models obtained from it inversion of the dipole-dipole data were usually very similar to the estimated models from pole-dipole data, and both were superior to estimated models from pole-pole data. This is because noisy dipole-dipole or pole-dipole data define geoelectric structures much more precisely than an equivalent set of noisy pole-pole data. One structure where the dipole-dipole array appeared decidedly superior was the prism beneath a conductive overburden. The final estimated models from he pole-pole data were more poorly resolved than the final models from the other arrays. Our results show that the pole-pole data is a poor choice if vertical resolution of a geoelectdc structure is crucial. Furthermore, if pole-pole data contains even a fraction of a percent of noise, the uwsforrr ation of such data through superposition to equivalent data of other array types is virtually impossible, and significant information is lost.
Three-dimensional induced polarization data inversion for complex resistivity
Commer, M.; Newman, G.A.; Williams, K.H.; Hubbard, S.S.
2011-03-15
The conductive and capacitive material properties of the subsurface can be quantified through the frequency-dependent complex resistivity. However, the routine three-dimensional (3D) interpretation of voluminous induced polarization (IP) data sets still poses a challenge due to large computational demands and solution nonuniqueness. We have developed a flexible methodology for 3D (spectral) IP data inversion. Our inversion algorithm is adapted from a frequency-domain electromagnetic (EM) inversion method primarily developed for large-scale hydrocarbon and geothermal energy exploration purposes. The method has proven to be efficient by implementing the nonlinear conjugate gradient method with hierarchical parallelism and by using an optimal finite-difference forward modeling mesh design scheme. The method allows for a large range of survey scales, providing a tool for both exploration and environmental applications. We experimented with an image focusing technique to improve the poor depth resolution of surface data sets with small survey spreads. The algorithm's underlying forward modeling operator properly accounts for EM coupling effects; thus, traditionally used EM coupling correction procedures are not needed. The methodology was applied to both synthetic and field data. We tested the benefit of directly inverting EM coupling contaminated data using a synthetic large-scale exploration data set. Afterward, we further tested the monitoring capability of our method by inverting time-lapse data from an environmental remediation experiment near Rifle, Colorado. Similar trends observed in both our solution and another 2D inversion were in accordance with previous findings about the IP effects due to subsurface microbial activity.
2-D magnetotelluric inversion of the central part of Paraná Basin
NASA Astrophysics Data System (ADS)
Santos, E. B.; Santos, H. B.; Vitorello, I.; Pádua, M. B.
2013-12-01
The Paraná Basin is a large sedimentary basin in central-eastern South America that extends through Brazil, Paraguay, Uruguay and Argentina. Evolved completely over the South American continental crust, this Paleozoic basin is filled with sedimentary and volcanic rocks deposited from the Silurian to the Cretaceous, when a significant basaltic effusion covered almost the entire area of the basin. A series of superposed sedimentary and volcanic rock layers were laid down under the influence of different tectonic settings, probably originated from distant collisional dynamics of continental boards that led to the amalgamation of Gondwanaland. The current boundaries of the basin can be the result of issuing erosional or of tectonic origin, such as the building up of large arches and faults. To evaluate the deep structural architecture of the lithosphere under a sedimentary basin is a great challenge, requiring the integration of different geophysical and geological studies. In this paper, we present the resulting Paraná Basin lithospheric model, obtained from processing and inversion of broadband and long-period magnetotelluric soundings along an E-W profile across the central part of the basin, complemented by a qualitative joint interpretation of gravimetric data, in order to obtain a more precise geoelectric model of the deep structure of the region.
Brunthaler, G; Prinz, A; Bauer, G; Pudalov, V M
2001-08-27
The temperature and density dependence of the phase coherence time tau(phi) in high-mobility silicon inversion layers was determined from the magnetoresistivity due to weak localization. The upper temperature limit for single-electron quantum interference effects was delineated by comparing tau(phi) with the momentum relaxation time tau. A comparison between the density dependence of the borders for quantum interference effects and the strong resistivity drop reveals that these effects are not related to each other. As the strong resistivity drop occurs in the Drude regime, the apparent metallic behavior cannot be caused by quantum coherent effects.
Albrecht, Daniel S.; Skosnik, Patrick D.; Vollmer, Jennifer M.; Brumbaugh, Margaret S.; Perry, Kevin M.; Mock, Bruce H.; Zheng, Qi-Huang; Federici, Lauren A.; Patton, Elizabeth A.; Herring, Christine M.; Yoder, Karmen K.
2012-01-01
BACKGROUND Although the incidence of cannabis abuse/dependence in Americans is rising, the neurobiology of cannabis addiction is not well understood. Imaging studies have demonstrated deficits in striatal D2/D3 receptor availability in several substance-dependent populations. However, this has not been studied in currently-using chronic cannabis users. OBJECTIVE The purpose of this study was to compare striatal D2/D3 receptor availability between currently-using chronic cannabis users and healthy controls. METHODS Eighteen right-handed males age 18–34 were studied. Ten subjects were chronic cannabis users; eight were demographically matched controls. Subjects underwent a [11C] raclopride (RAC) PET scan. Striatal RAC binding potential (BPND) was calculated on a voxel-wise basis. Prior to scanning, urine samples were obtained from cannabis users for quantification of urine Δ-9-tetrahydrocannabinol (THC) and THC metabolites (11-nor-Δ-9-THC-9-carboxylic acid; THC-COOH and 11-hydroxy-THC;OH-THC). Results There were no differences in D2/D3 receptor availability between cannabis users and controls. Voxel-wise analyses revealed that RAC BPND values were negatively associated with both urine levels of cannabis metabolites and self-report of recent cannabis consumption. CONCLUSIONS In this sample, current cannabis use was not associated with deficits in striatal D2/D3 receptor availability. There was an inverse relationship between chronic cannabis use and striatal RAC BPND. Additional studies are needed to identify the neurochemical consequences of chronic cannabis use on the dopamine system. PMID:22909787
NASA Astrophysics Data System (ADS)
Maurya, P. K.; Rønde, V. K.; Fiandaca, G.; Balbarini, N.; Auken, E.; Bjerg, P. L.; Christiansen, A. V.
2017-03-01
Leaching of organic and inorganic contamination from landfills is a serious environmental problem as surface water and aquifers are affected. In order to assess these risks and investigate the migration of leachate from the landfill, 2D and large scale 3D electrical resistivity tomography were used at a heavily contaminated landfill in Grindsted, Denmark. The inverted 2D profiles describe both the variations along the groundwater flow as well as the plume extension across the flow directions. The 3D inversion model shows the variability in the low resistivity anomaly pattern corresponding to differences in the ionic strength of the landfill leachate. Chemical data from boreholes agree well with the observations indicating a leachate plume which gradually sinks and increases in size while migrating from the landfill in the groundwater flow direction. Overall results show that the resistivity method has been very successful in delineating the landfill leachate plume and that good correlation exists between the resistivity model and leachate ionic strength.
An inversion method of 2D NMR relaxation spectra in low fields based on LSQR and L-curve
NASA Astrophysics Data System (ADS)
Su, Guanqun; Zhou, Xiaolong; Wang, Lijia; Wang, Yuanjun; Nie, Shengdong
2016-04-01
The low-field nuclear magnetic resonance (NMR) inversion method based on traditional least-squares QR decomposition (LSQR) always produces some oscillating spectra. Moreover, the solution obtained by traditional LSQR algorithm often cannot reflect the true distribution of all the components. Hence, a good solution requires some manual intervention, for especially low signal-to-noise ratio (SNR) data. An approach based on the LSQR algorithm and L-curve is presented to solve this problem. The L-curve method is applied to obtain an improved initial optimal solution by balancing the residual and the complexity of the solutions instead of manually adjusting the smoothing parameters. First, the traditional LSQR algorithm is used on 2D NMR T1-T2 data to obtain its resultant spectra and corresponding residuals, whose norms are utilized to plot the L-curve. Second, the corner of the L-curve as the initial optimal solution for the non-negative constraint is located. Finally, a 2D map is corrected and calculated iteratively based on the initial optimal solution. The proposed approach is tested on both simulated and measured data. The results show that this algorithm is robust, accurate and promising for the NMR analysis.
NASA Astrophysics Data System (ADS)
Bignardi, S.; Mantovani, A.; Abu Zeid, N.
2016-08-01
OpenHVSR is a computer program developed in the Matlab environment, designed for the simultaneous modeling and inversion of large Horizontal-to-Vertical Spectral Ratio (HVSR or H/V) datasets in order to construct 2D/3D subsurface models (topography included). The program is designed to provide a high level of interactive experience to the user and still to be of intuitive use. It implements several effective and established tools already present in the code ModelHVSR by Herak (2008), and many novel features such as: -confidence evaluation on lateral heterogeneity -evaluation of frequency dependent single parameter impact on the misfit function -relaxation of Vp/Vs bounds to allow for water table inclusion -a new cost function formulation which include a slope dependent term for fast matching of peaks, which greatly enhances convergence in case of low quality HVSR curves inversion -capability for the user of editing the subsurface model at any time during the inversion and capability to test the changes before acceptance. In what follows, we shall present many features of the program and we shall show its capabilities on both simulated and real data. We aim to supply a powerful tool to the scientific and professional community capable of handling large sets of HSVR curves, to retrieve the most from their microtremor data within a reduced amount of time and allowing the experienced scientist the necessary flexibility to integrate into the model their own geological knowledge of the sites under investigation. This is especially desirable now that microtremor testing has become routinely used. After testing the code over different datasets, both simulated and real, we finally decided to make it available in an open source format. The program is available by contacting the authors.
High-resistance liquid-crystal lens array for rotatable 2D/3D autostereoscopic display.
Chang, Yu-Cheng; Jen, Tai-Hsiang; Ting, Chih-Hung; Huang, Yi-Pai
2014-02-10
A 2D/3D switchable and rotatable autostereoscopic display using a high-resistance liquid-crystal (Hi-R LC) lens array is investigated in this paper. Using high-resistance layers in an LC cell, a gradient electric-field distribution can be formed, which can provide a better lens-like shape of the refractive-index distribution. The advantages of the Hi-R LC lens array are its 2D/3D switchability, rotatability (in the horizontal and vertical directions), low driving voltage (~2 volts) and fast response (~0.6 second). In addition, the Hi-R LC lens array requires only a very simple fabrication process.
Groundwater Exploration Using 2-D Resistivity Imaging Technique in Marang, Terengganu, Malaysia
NASA Astrophysics Data System (ADS)
Kadri, Muhammad; Nawawi, M. N. M.
2010-07-01
Surface water is critically important in supplying water to streams and wetlands, and in providing water for irrigation, manufacturing, electricity power and other uses and it is an important source of water supply especially in various regions in Malaysia and it become ever more important with an increasing population. However groundwater can be an alternative source of water to the ever increasing population. Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of lithologic water formations. This would provide alternative freshwater source. In order to determine the existence of usable groundwater for agriculture purposes in Marang Terengganu, 2-D resistivity imaging technique was utilized. Three lines were surveyed at the site. The 2-D resistivity imaging technique utilized the Pole -dipole array because of relatively good horizontal coverage but it has significantly higher signal strength. The total length of the survey lines is 400 meters. Three lines were surveyed for groundwater delineation purpose. At Marang, the survey site shows the existence of groundwater. The maximum depth of investigations for the surveys is 125 meters. In general the results show that the subsurface is made up of sand and clay (resistivity value of less 100 ohm-m) and sandstone with resistivity of more than 2000 ohm-m in all the sections. This zone can be a source of groundwater.
Groundwater exploration using 2D Resistivity Imaging in Pagoh, Johor, Malaysia
NASA Astrophysics Data System (ADS)
Kadri, Muhammad; Nawawi, M. N. M.
2010-12-01
Groundwater is a very important component of water resources in nature. Since the demand of groundwater increases with population growth, it is necessary to explore groundwater more intensively. In Malaysia only less than 2% of the present water used is developed from groundwater. In order to determine the existence of usable groundwater for irrigation and drinking purposes in Pagoh, 2D resistivity imaging technique was utilized. The 2-D resistivity imaging technique utilized the Wenner—Schlumberger electrode array configuration because this array is moderately sensitive to both horizontal and vertical structures. Three lines were surveyed for groundwater delineation purpose The length for each survey lines are 400 meters. At Pagoh, the survey site shows the existence of groundwater. It is indicated by the resistivity values about 10-100 ohm-m. The maximum depth of investigation survey is 77 meters. In general the results show that the subsurface is made up of alluvium and clay and the high resistivity values of more than 1000 ohm-m near the surface is due laterite and the end of the depth can be interpreted as mixture of weathered material or bedrock.
1985-01-01
Bridge Kelvin Resistor, the Contact End Resistor, and the Transmission pletely by its sheet resistance . We shall concentrate here on semiconduc- Line...Tap Resistor. For each particular structure, a wniversal set of curves tar to metal contacts. Since the metal sheet resistance is much lower than is...derived that allows accurate determination of V,, given the geometry Of diffusion sheet resistance , metal is considered to be an equipotential the
3D Inversion of complex resistivity data: Case study on Mineral Exploration Site.
NASA Astrophysics Data System (ADS)
Son, Jeong-Sul; Kim, Jung-ho; Park, Sam-gyu; Park, My-Kyung
2016-04-01
Complex resistivity (CR) method is a frequency domain induced polarization (IP) method. It is also known as Spectral IP (SIP) method, if wider frequencies are used in data acquisition and interpretation. Although it takes more times than conventional time domain IP method, its data quality is more stable because its data acquisition which measures amplitude and phase is done when the source current is being injected. Our research group has been studying the modeling and inversion algorithms of complex resistivity (CR) method since several years ago and recently applied developed algorithms to various real field application. Due to tough terrain in our country, Profile survey and 2D interpretation were generally used. But to get more precise interpretation, three dimensional modeling and inversion algorithm is required. We developed three dimensional inversion algorithm for this purpose. In the inversion, we adopt the method of adaptive lagraingian multiplier which is automatically set based on the size of error misfit and model regularization norm. It was applied on the real data acquired for mineral exploration sites. CR data was acquired with the Zeta system, manufactured by Zonge Co. In the inversion, only the lower frequency data is used considering its quality and developed 3D inversion algorithm was applied to the acquired data set. Its results were compared to those of time domain IP data conducted at the same site. Resistivity image sections of CR and conventional resistivity method were almost identical. Phase anomalies were well matched with chargeability anomalies and the mining history of the test site. Each anomalies were well discriminated in 3D interpretation than those of 2D. From those experiments, we know that CR method was very effective for the mineral exploration.
Li, Hua; Thériault, Jolaine; Rousselle, Bruno; Subramanian, Balaji; Robichaud, Jacques; Djaoued, Yahia
2014-02-28
A 'dynamic hard-template' infiltration strategy for crack-free large-area synthesis of 2D WO3 inverse opal (IO) films on ITO substrates using a wide range of sizes of sacrificial PS spheres is reported. Thus prepared WO3 IO films were successfully used as an active electrode in the fabrication of an electrochromic device.
Miñán, A; Schilardi, P L; Fernández Lorenzo de Mele, M
2016-04-01
Biofilms formed on implanted devices are difficult to eradicate. Adhesion mechanism, high bacterial density, aggregation, induction of persisters and stressed bacteria are some of the factors considered when the antimicrobial resistance of these biofilms is analyzed. The aim of this work was to provide an alternative approach to the understanding of this issue by using a specially designed experimental set up that includes the use of microstructured (MS) surfaces (potential inhibitors of bacterial aggregation) in combination with antimicrobial agents (streptomycin and levofloxacin) against Staphylococcusaureus attached cells. Biofilms formed on smooth surfaces were used as plain controls (biofilmed-PC) characterized by the formation of dense 2D bacterial aggregates. Results showed bacterial persistence when streptomycin or levofloxacin were applied to PC-biofilms. The antimicrobial activity of both antibiotics was enhanced when bacteria were attached on MS, where single cells or small aggregates were observed. Thus, dense 2D aggregates of bacteria seem to be crucial as a required previous stage to develop the antimicrobial resistance.
NASA Astrophysics Data System (ADS)
Realpe Campaña, Julian David; Porsani, Jorge Luís; Bortolozo, Cassiano Antonio; Serejo de Oliveira, Gabriela; Monteiro dos Santos, Fernando Acácio
2017-03-01
Results of a TEM profile by using the fixed-loop array and an analysis of the induced magnetic field are presented in this work performed in the northwest region of São Paulo State, Brazil, Paraná Basin. The objectives of this research were to map the sedimentary and crystalline aquifers in the area and analyzing the behavior of the magnetic field by observation of magnetic profiles. TEM measurements in the three spatial components were taken to create magnetic profiles of the induced (secondary) magnetic field. The TEM data were acquired using a fixed transmitter loop of 200 m × 200 m and a 3D coil receiver moving along a profile line of 1000 m. Magnetic profiles of dBz, dBx and dBy components showed symmetrical spatial behavior related with loop geometry. z-component showed a behavior probably related to superparamagnetic effect (SPM). dBz data was used to perform individual 1D inversion for each position and to generate an interpolated pseudo-2D geoelectric profile. The results showed two low resistivity zones: the first shallow, between 10 m and 70 m deep, probably related to the Adamantina Formation (sedimentary aquifer). The second between 200 m and 300 m depth, probably related to a fractured zone filled with water or clay inside the basalt layer of the Serra Geral Formation (crystalline aquifer). These results agree with the well logs information available in the studied region.
Large resistive 2D Micromegas with genetic multiplexing and some imaging applications
NASA Astrophysics Data System (ADS)
Bouteille, S.; Attié, D.; Baron, P.; Calvet, D.; Magnier, P.; Mandjavidze, I.; Procureur, S.; Riallot, M.
2016-10-01
The performance of the first large resistive Micromegas detectors with 2D readout and genetic multiplexing is presented. These detectors have a 50 × 50cm2 active area and are equipped with 1024 strips both in X- and Y-directions. The same genetic multiplexing pattern is applied on both coordinates, resulting in the compression of signals on 2 × 61 readout channels. Four such detectors have been built at CERN, and extensively tested with cosmics. The resistive strip film allows for very high gain operation, compensating for the charge spread on the 2 dimensions as well as the S / N loss due to the huge, 1 nF input capacitance. This film also creates a significantly different signal shape in the X- and Y-coordinates due to the charge evacuation along the resistive strips. All in all a detection efficiency above 95% is achieved with a 1 cm drift gap. Though not yet optimal, the measured 300 μm spatial resolution allows for very precise imaging in the field of muon tomography, and some applications of these detectors are presented.
NASA Astrophysics Data System (ADS)
Schaa, R.; Gross, L.; du Plessis, J.
2016-04-01
We present a general finite-element solver, escript, tailored to solve geophysical forward and inverse modeling problems in terms of partial differential equations (PDEs) with suitable boundary conditions. Escript’s abstract interface allows geoscientists to focus on solving the actual problem without being experts in numerical modeling. General-purpose finite element solvers have found wide use especially in engineering fields and find increasing application in the geophysical disciplines as these offer a single interface to tackle different geophysical problems. These solvers are useful for data interpretation and for research, but can also be a useful tool in educational settings. This paper serves as an introduction into PDE-based modeling with escript where we demonstrate in detail how escript is used to solve two different forward modeling problems from applied geophysics (3D DC resistivity and 2D magnetotellurics). Based on these two different cases, other geophysical modeling work can easily be realized. The escript package is implemented as a Python library and allows the solution of coupled, linear or non-linear, time-dependent PDEs. Parallel execution for both shared and distributed memory architectures is supported and can be used without modifications to the scripts.
Joint Inversion of Vp, Vs, and Resistivity at SAFOD
NASA Astrophysics Data System (ADS)
Bennington, N. L.; Zhang, H.; Thurber, C. H.; Bedrosian, P. A.
2010-12-01
Seismic and resistivity models at SAFOD have been derived from separate inversions that show significant spatial similarity between the main model features. Previous work [Zhang et al., 2009] used cluster analysis to make lithologic inferences from trends in the seismic and resistivity models. We have taken this one step further by developing a joint inversion scheme that uses the cross-gradient penalty function to achieve structurally similar Vp, Vs, and resistivity images that adequately fit the seismic and magnetotelluric MT data without forcing model similarity where none exists. The new inversion code, tomoDDMT, merges the seismic inversion code tomoDD [Zhang and Thurber, 2003] and the MT inversion code Occam2DMT [Constable et al., 1987; deGroot-Hedlin and Constable, 1990]. We are exploring the utility of the cross-gradients penalty function in improving models of fault-zone structure at SAFOD on the San Andreas Fault in the Parkfield, California area. Two different sets of end-member starting models are being tested. One set is the separately inverted Vp, Vs, and resistivity models. The other set consists of simple, geologically based block models developed from borehole information at the SAFOD drill site and a simplified version of features seen in geophysical models at Parkfield. For both starting models, our preliminary results indicate that the inversion produces a converging solution with resistivity, seismic, and cross-gradient misfits decreasing over successive iterations. We also compare the jointly inverted Vp, Vs, and resistivity models to borehole information from SAFOD to provide a "ground truth" comparison.
NASA Astrophysics Data System (ADS)
Gao, J.; Zhang, H.
2015-12-01
Near surface geophysical exploration for the purpose of engineering design or construction For this reason, geophysical imaging demands a higher resolution and a better quantitative interpretation. Seismic travel time tomography and direct current resistivity tomography are two main methods for the near surface survey. Because of the limited coverage of observation system and the complex physical relationship between physical parameters and observations, individual geophysical method suffers issues of non-uniqueness and resolution limitation to some degree. We have developed a joint inversion method to combine seismic travel time tomography and full channel resistivity tomography. For the full channel resistivity survey, it uses two electrodes for power supply and all the other electrodes for recording. Compared with the traditional resistivity method, it collects more data and has a better model converge. Our joint inversion strategy relies on the structure constraint enforced through minimizing cross gradients between seismic velocity and resistivity models (Gallardo, 2003). For resistivity tomography, sensitivity kernels are obtained through the adjoint method by solving the electrostatic field equation with the finite-difference method. For seismic travel time tomography, ray paths and travel times are calculated using the fast marching method. We have tested our joint inversion method for a 2D cross-hole problem where two small zones with high and low velocity/resistivity anomalies. Seismic/electrical sources/receivers are installed in two boreholes. For separate seismic inversion, the smearing effect is evident and two anomaly zones are distorted and misplaced. For separate electric resistivity inversion, although two anomaly zones are positioned correctly their values are not accurate. By joint inversion, two velocity anomaly zones are clearly imaged and the smearing effect is greatly reduced. In comparison, for the resistivity model, the two anomaly zones
Residual resistance of 2D and 3D structures and Joule heat release.
Gurevich, V L; Kozub, V I
2011-06-22
We consider a residual resistance and Joule heat release in 2D nanostructures as well as in ordinary 3D conductors. We assume that elastic scattering of conduction electrons by lattice defects is predominant. Within a rather intricate situation in such systems we discuss in detail two cases. (1) The elastic scattering alone (i.e. without regard of inelastic mechanisms of scattering) leads to a transition of the mechanical energy (stored by the electrons under the action of an electric field) into heat in a traditional way. This process can be described by the Boltzmann equation where it is possible to do the configuration averaging over defect positions in the electron-impurity collision term. The corresponding conditions are usually met in metals. (2) The elastic scattering can be considered with the help of the standard electron-impurity collision integral only in combination with some additional averaging procedure (possibly including inelastic scattering or some mechanisms of electron wavefunction phase destruction). This situation is typical for degenerate semiconductors with a high concentration of dopants and conduction electrons. Quite often, heat release can be observed via transfer of heat to the lattice, i.e. via inelastic processes of electron-phonon collisions and can take place at distances much larger than the size of the device. However, a direct heating of the electron system can be registered too by, for instance, local measurements of the current noise or direct measurement of an electron distribution function.
NASA Astrophysics Data System (ADS)
Yang, X.; Zhu, P.; Gu, Y.; Xu, Z.
2015-12-01
Small scale heterogeneities of subsurface medium can be characterized conveniently and effectively using a few simple random medium parameters (RMP), such as autocorrelation length, angle and roughness factor, etc. The estimation of these parameters is significant in both oil reservoir prediction and metallic mine exploration. Poor accuracy and low stability existed in current estimation approaches limit the application of random medium theory in seismic exploration. This study focuses on improving the accuracy and stability of RMP estimation from post-stacked seismic data and its application in the seismic inversion. Experiment and theory analysis indicate that, although the autocorrelation of random medium is related to those of corresponding post-stacked seismic data, the relationship is obviously affected by the seismic dominant frequency, the autocorrelation length, roughness factor and so on. Also the error of calculation of autocorrelation in the case of finite and discrete model decreases the accuracy. In order to improve the precision of estimation of RMP, we design two improved approaches. Firstly, we apply region growing algorithm, which often used in image processing, to reduce the influence of noise in the autocorrelation calculated by the power spectrum method. Secondly, the orientation of autocorrelation is used as a new constraint in the estimation algorithm. The numerical experiments proved that it is feasible. In addition, in post-stack seismic inversion of random medium, the estimated RMP may be used to constrain inverse procedure and to construct the initial model. The experiment results indicate that taking inversed model as random medium and using relatively accurate estimated RMP to construct initial model can get better inversion result, which contained more details conformed to the actual underground medium.
NASA Astrophysics Data System (ADS)
Rizzuti, G.; Gisolf, A.
2017-03-01
We study a reconstruction algorithm for the general inverse scattering problem based on the estimate of not only medium properties, as in more conventional approaches, but also wavefields propagating inside the computational domain. This extended set of unknowns is justified as a way to prevent local minimum stagnation, which is a common issue for standard methods. At each iteration of the algorithm, (i) the model parameters are obtained by solution of a convex problem, formulated from a special bilinear relationship of the data with respect to properties and wavefields (where the wavefield is kept fixed), and (ii) a better estimate of the wavefield is calculated, based on the previously reconstructed properties. The resulting scheme is computationally convenient since step (i) can greatly benefit from parallelization and the wavefield update (ii) requires modeling only in the known background model, which can be sped up considerably by factorization-based direct methods. The inversion method is successfully tested on synthetic elastic datasets.
Lin, Lin; Yang, Chao; Lu, Jiangfeng; Ying, Lexing; E, Weinan
2009-09-25
We present an efficient parallel algorithm and its implementation for computing the diagonal of $H^-1$ where $H$ is a 2D Kohn-Sham Hamiltonian discretized on a rectangular domain using a standard second order finite difference scheme. This type of calculation can be used to obtain an accurate approximation to the diagonal of a Fermi-Dirac function of $H$ through a recently developed pole-expansion technique \\cite{LinLuYingE2009}. The diagonal elements are needed in electronic structure calculations for quantum mechanical systems \\citeHohenbergKohn1964, KohnSham 1965,DreizlerGross1990. We show how elimination tree is used to organize the parallel computation and how synchronization overhead is reduced by passing data level by level along this tree using the technique of local buffers and relative indices. We analyze the performance of our implementation by examining its load balance and communication overhead. We show that our implementation exhibits an excellent weak scaling on a large-scale high performance distributed parallel machine. When compared with standard approach for evaluating the diagonal a Fermi-Dirac function of a Kohn-Sham Hamiltonian associated a 2D electron quantum dot, the new pole-expansion technique that uses our algorithm to compute the diagonal of $(H-z_i I)^-1$ for a small number of poles $z_i$ is much faster, especially when the quantum dot contains many electrons.
NASA Astrophysics Data System (ADS)
Pérez-Corona, M.; García, J. A.; Taller, G.; Polgár, D.; Bustos, E.; Plank, Z.
2016-02-01
The purpose of geophysical electrical surveys is to determine the subsurface resistivity distribution by making measurements on the ground surface. From these measurements, the true resistivity of the subsurface can be estimated. The ground resistivity is related to various geological parameters, such as the mineral and fluid content, porosity and degree of water saturation in the rock. Electrical resistivity surveys have been used for many decades in hydrogeological, mining and geotechnical investigations. More recently, they have been used for environmental surveys. To obtain a more accurate subsurface model than is possible with a simple 1-D model, a more complex model must be used. In a 2-D model, the resistivity values are allowed to vary in one horizontal direction (usually referred to as the x direction) but are assumed to be constant in the other horizontal (the y) direction. A more realistic model would be a fully 3-D model where the resistivity values are allowed to change in all three directions. In this research, a simulation of the cone penetration test and 2D imaging resistivity are used as tools to simulate the distribution of hydrocarbons in soil.
NASA Astrophysics Data System (ADS)
Schmoldt, J.; Jones, A. G.; Muller, M. R.; Kiyan, D.; Hogg, C.; Rosell, O.
2010-12-01
Two-dimensional (2D) inversions of magnetotelluric (MT) data are presently far more commonly used than three-dimensional (3D) inversions as they still significantly outperform 3D inversions in terms of speed, thus allowing for much better resolution of the subsurface through a larger feasible number of grid cells. The suitability of 2D inversion needs thereby to be tested for cases where the electric resistivity structure of the subsurface is potentially 3D to some extent. One particular case of a 3D subsurface structure consists of lateral interfaces with varying orientations at crustal and mantle depths. Such a case might emerge, for instance, where crustal faulting, originating from present day tectonics, is situated above a mantle where structures are dominated by earlier or current plate tectonic processes. Those plate tectonic processes could comprise continental collision from an oblique direction, or lattice preferred orientation in the lithosphere-asthenosphere transition zone due to an oblique relative motion between lithosphere and asthenosphere. Whereas recovery of crustal structures can usually be achieved in a straightforward manner by confining the modelled frequency range to the crustal depths, deriving mantle structures is more challenging. Different approaches for this case have been investigated here using synthetic model studies as well as inversion of a real MT dataset collected in southern Spain as part of the PICASSO fieldwork campaign. The PICASSO project intends to enhance knowledge about the geological setting of the Alboran Domain beneath the western Mediterranean Sea and its surrounding regions, and through that knowledge to understand processes related to continent-continent collision. The Iberian Peninsula is the focus of the first phase of DIAS’s PICASSO efforts, and comprised a magnetotelluric profile crossing the Tajo Basin and Betics Cordillera. Analyses of MT responses and seismic tomography data indicate varying geologic strike
Resistance to change varies inversely with reinforcement context.
Grace, Randolph C; Arantes, Joana; Berg, Mark E
2012-07-01
We report two experiments which test whether resistance to prefeeding and satiation for a variable-interval (VI) schedule that delivers a constant rate of reinforcement varies inversely with the reinforcement rate for an alternative schedule. In Experiment 1, eight pigeons responded in a multiple schedule in which the red key was always associated with a VI 90-s schedule and the green key with either a richer (VI 18s) or leaner (VI 540s) schedule in different conditions. After baseline training in each condition, prefeeding test sessions were conducted in which 10g, 20g, 30g, 40g, and 50g food were provided one-hour prior to test. Additional baseline training was given between each test session. In Experiment 2, two groups of pigeons responded in a multiple schedule similar to Experiment 1. After baseline training, pigeons were exposed to a 5-h satiation test session in which the VI 90-s schedule was available continuously. Test sessions were conducted when pigeons were maintained at 85%, 95%, and 85% of their body weights in an ABA design. Results of both experiments showed that responding in the VI 90-s schedule that alternated with a leaner schedule during baseline was more resistant to prefeeding and satiation. These data rule out alternative explanations for results of previous studies, and confirm that resistance to change varies inversely with reinforcement context.
NASA Astrophysics Data System (ADS)
Dagnino, D.; Sallarès, V.; Biescas, B.; Ranero, C. R.
2016-08-01
This work demonstrates the feasibility of 2-D time-domain, adjoint-state acoustic full-waveform inversion (FWI) to retrieve high-resolution models of ocean physical parameters such as sound speed, temperature and salinity. The proposed method is first described and then applied to prestack multichannel seismic (MCS) data acquired in the Gulf of Cadiz (SW Iberia) in 2007 in the framework of the Geophysical Oceanography project. The inversion strategy flow includes specifically designed data preconditioning for acoustic noise reduction, followed by the inversion of sound speed in the shotgather domain. We show that the final sound speed model has a horizontal resolution of ˜ 70 m, which is two orders of magnitude better than that of the initial model constructed with coincident eXpendable Bathy Thermograph (XBT) data, and close to the theoretical resolution of O(λ). Temperature (T) and salinity (S) are retrieved with the same lateral resolution as sound speed by combining the inverted sound speed model with the thermodynamic equation of seawater and a local, depth-dependent T-S relation derived from regional conductivity-temperature-depth (CTD) measurements of the National Oceanic and Atmospheric Administration (NOAA) database. The comparison of the inverted T and S models with XBT and CTD casts deployed simultaneously to the MCS acquisition shows that the thermohaline contrasts are resolved with an accuracy of 0.18oC for temperature and 0.08 PSU for salinity. The combination of oceanographic and MCS data into a common, pseudo-automatic inversion scheme allows to quantitatively resolve submeso-scale features that ought to be incorporated into larger-scale ocean models of oceans structure and circulation.
Chuang, Hsun -Jen; Chamlagain, Bhim; Koehler, Michael; Perera, Meeghage Madusanka; Yan, Jiaqiang; Mandrus, David; Tomanek, David; Zhou, Zhixian
2016-02-04
Here, we report a new strategy for fabricating 2D/2D low-resistance ohmic contacts for a variety of transition metal dichalcogenides (TMDs) using van der Waals assembly of substitutionally doped TMDs as drain/source contacts and TMDs with no intentional doping as channel materials. We demonstrate that few-layer WSe_{2} field-effect transistors (FETs) with 2D/2D contacts exhibit low contact resistances of ~0.3 kΩ μm, high on/off ratios up to >10^{9}, and high drive currents exceeding 320 μA μm^{–1}. These favorable characteristics are combined with a two-terminal field-effect hole mobility μ_{FE} ≈ 2 × 10^{2} cm^{2} V^{–1} s^{–1} at room temperature, which increases to >2 × 10^{3} cm^{2} V^{–1} s^{–1} at cryogenic temperatures. We observe a similar performance also in MoS_{2} and MoSe_{2} FETs with 2D/2D drain and source contacts. The 2D/2D low-resistance ohmic contacts presented here represent a new device paradigm that overcomes a significant bottleneck in the performance of TMDs and a wide variety of other 2D materials as the channel materials in postsilicon electronics.
NASA Astrophysics Data System (ADS)
Mashayekhi, Parisa; Ghorbani-Dashtaki, Shoja; Mosaddeghi, Mohammad Reza; Shirani, Hossein; Nodoushan, Ali Reza Mohammadi
2016-04-01
In this study, HYDRUS-2D/3D was used to simulate ponded infiltration through double-ring infiltrometers into a hypothetical loamy soil profile. Twelve scenarios of inverse modelling (divided into three groups) were considered for estimation of Mualem-van Genuchten hydraulic parameters. In the first group, simulation was carried out solely using cumulative infiltration data. In the second group, cumulative infiltration data plus water content at h = -330 cm (field capacity) were used as inputs. In the third group, cumulative infiltration data plus water contents at h = -330 cm (field capacity) and h = -15 000 cm (permanent wilting point) were used simultaneously as predictors. The results showed that numerical inverse modelling of the double-ring infiltrometer data provided a reliable alternative method for determining soil hydraulic parameters. The results also indicated that by reducing the number of hydraulic parameters involved in the optimization process, the simulation error is reduced. The best one in infiltration simulation which parameters α, n, and Ks were optimized using the infiltration data and field capacity as inputs. Including field capacity as additional data was important for better optimization/definition of soil hydraulic functions, but using field capacity and permanent wilting point simultaneously as additional data increased the simulation error.
NASA Astrophysics Data System (ADS)
Fernández-Martínez, J. L.; Fernández-Alvarez, J. P.; Pedruelo-González, L. M.
2008-03-01
A MATLAB ®-based computer code that analyses the traveltime distribution and performs quality analysis at the pre-inversion stage for 2D transmission experiments is presented. The core tools of this approach are the so-called mean traveltime curves. For any general recording geometry, the user may select any pair of subsets of contiguous sources and receivers. The portion of the domain swept by the implied rays defines a zone of analysis, and for each source (receiver) the outcoming (incoming) ray fan is named a source (receiver) gather. The empirical mean traveltime curves are constructed, for each zone, by assigning the average and the standard deviation of the traveltimes in the gathers to the positions of the sources (receivers). The theoretical expressions assume isotropic homogeneous velocity inside each zone. The empirical counterparts use the observed traveltimes and make no assumptions. Isotropic velocity in each zone is inferred by least-squares fitting of the empirical mean traveltime curves. The user may refine the analysis considering different zones (multi-zone analysis). Initially the whole domain is modelled as a single zone. The procedure compares empirical versus theoretical curves. In addition, residuals can be plotted using source-receiver positions as plane coordinates. The results are used to unravel the possible presence of anomalous gathers, heterogeneities, anisotropies, etc. Depending on the kind of anomalies, velocity estimation and mean time residuals are different in the source and receiver gather curves. This software helps to grasp a better understanding of the data variability before the inversion and provides to the geophysicist an approximate zonal isotropic model and a range of velocity variation that can be used in the inverse problem as a priori information (regularization term). Its use is described through tutorial examples. A guided user interface leads the user through the algorithm steps.
Baker, Theresa; Nerle, Sujata; Pritchard, Justin; Zhao, Boyang; Rivera, Victor M.
2015-01-01
Although targeted therapies have revolutionized cancer treatment, overcoming acquired resistance remains a major clinical challenge. EZH2 inhibitors (EZH2i), EPZ-6438 and GSK126, are currently in the early stages of clinical evaluation and the first encouraging signs of efficacy have recently emerged in the clinic. To anticipate mechanisms of resistance to EZH2i, we used a forward genetic platform combining a mutagenesis screen with next generation sequencing technology and identified a hotspot of secondary mutations in the EZH2 D1 domain (Y111 and I109). Y111D mutation within the WT or A677G EZH2 allele conferred robust resistance to both EPZ-6438 and GSK126, but it only drove a partial resistance within the Y641F allele. EZH2 mutants required histone methyltransferase (HMT) catalytic activity and the polycomb repressive complex 2 (PRC2) components, SUZ12 and EED, to drive drug resistance. Furthermore, D1 domain mutations not only blocked the ability of EZH2i to bind to WT and A677G mutant, but also abrogated drug binding to the Y641F mutant. These data provide the first cellular validation of the mechanistic model underpinning the oncogenic function of WT and mutant EZH2. Importantly, our findings suggest that acquired-resistance to EZH2i may arise in WT and mutant EZH2 patients through a single mutation that remains targetable by second generation EZH2i. PMID:26360609
Tuning and simulating a 193-nm resist for 2D applications
NASA Astrophysics Data System (ADS)
Howard, William B.; Wiaux, Vincent; Ercken, Monique; Bui, Bang; Byers, Jeff D.; Pochkowski, Mike
2002-07-01
For some applications, the usefulness of lithography simulation results depends strongly on the matching between experimental conditions and the simulation input parameters. If this matching is optimized and other sources of error are minimized, then the lithography model can be used to explain printed wafer experimental results. Further, simulation can be useful in predicting the results or in choosing the correct set of experiments. In this paper, PROLITH and ProDATA AutoTune were used to systematically vary simulation input parameters to match measured results on printed wafers used in a 193 nm process. The validity of the simulation parameters was then checked using 3D simulation compared to 2D top-down SEM images. The quality of matching was evaluated using the 1D metrics of average gate CD and Line End Shortening (LES). To ensure the most accurate simulation, a new approach was taken to create a compound mask from GDSII contextual information surrounding an accurate SEM image of the reticle region of interest. Corrections were made to account for all metrology offsets.
Detection of metallic and plastic landmines using the GPR and 2-D resistivity techniques
NASA Astrophysics Data System (ADS)
Metwaly, M.
2007-12-01
Low and non-metallic landmines are one of the most difficult subsurface targets to be detected using several geophysical techniques. Ground penetrating radar (GPR) performance at different field sites shows great success in detecting metallic landmines. However significant limitations are taking place in the case of low and non-metallic landmines. Electrical resistivity imaging (ERI) technique is tested to be an alternative or confirmation technique for detecting the metallic and non-metallic landmines in suspicious cleared areas. The electrical resistivity responses using forward modeling for metallic and non-metallic landmines buried in dry and wet environments utilizing the common electrode configurations have been achieved. Roughly all the utilized electrode arrays can establish the buried metallic and plastic mines correctly in dry and wet soil. The accuracy differs from one array to the other based on the relative resistivity contrast to the host soil and the subsurface distribution of current and potential lines as well as the amplitude of the noises in the data. The ERI technique proved to be fast and effective tool for detecting the non-metallic mines especially in the conductive environment whereas the performances of the other metal detector (MD) and GPR techniques show great limitation.
NASA Astrophysics Data System (ADS)
Hoshi, Toru; Matsuno, Ryosuke; Sawaguchi, Takashi; Konno, Tomohiro; Takai, Madoka; Ishihara, Kazuhiko
2008-11-01
To prepare the biocompatible surface, a phosphorylcholine (PC) group was introduced on this hydroxyl group generated by surface hydrolysis on the polymer composite composed of polyethylene (PE) and poly (vinyl acetate) (PVAc) prepared by supercritical carbon dioxide. Two different procedures such as two-dimensional (2D) modification and three-dimensional (3D) modification were applied to obtain the steady biocompatible surface. 2D modification was that PC groups were directly anchored on the surface of the polymer composite. 3D modification was that phospholipid polymer was grafted from the surface of the polymer composite by surface-initiated atom transfer radical polymerization (SI-ATRP) of 2-methacryloyloxyethyl phosphorylcholine (MPC). The surfaces were characterized by X-ray photoelectron spectroscopy, dynamic water contact angle measurements, and atomic force microscope. The effects of the poly(MPC) chain length on the protein adsorption resistivity were investigated. The protein adsorption on the polymer composite surface with PC groups modified by 2D or 3D modification was significantly reduced as compared with that on the unmodified PE. Further, the amount of protein adsorbed on the 3D modified surface that is poly(MPC)-grafted surface decreased with an increase in the chain length of the poly(MPC). The surface with an arbitrary structure and the characteristic can be constructed by using 2D and 3D modification. We conclude that the polymer composites of PE/PVAc with PC groups on the surface are useful for fabricating biomedical devices due to their good mechanical and surface properties.
NASA Astrophysics Data System (ADS)
Sourbier, F.; Operto, S.; Virieux, J.
2006-12-01
We present a distributed-memory parallel algorithm for 2D visco-acoustic full-waveform inversion of wide-angle seismic data. Our code is written in fortran90 and use MPI for parallelism. The algorithm was applied to real wide-angle data set recorded by 100 OBSs with a 1-km spacing in the eastern-Nankai trough (Japan) to image the deep structure of the subduction zone. Full-waveform inversion is applied sequentially to discrete frequencies by proceeding from the low to the high frequencies. The inverse problem is solved with a classic gradient method. Full-waveform modeling is performed with a frequency-domain finite-difference method. In the frequency-domain, solving the wave equation requires resolution of a large unsymmetric system of linear equations. We use the massively parallel direct solver MUMPS (http://www.enseeiht.fr/irit/apo/MUMPS) for distributed-memory computer to solve this system. The MUMPS solver is based on a multifrontal method for the parallel factorization. The MUMPS algorithm is subdivided in 3 main steps: a symbolic analysis step that performs re-ordering of the matrix coefficients to minimize the fill-in of the matrix during the subsequent factorization and an estimation of the assembly tree of the matrix. Second, the factorization is performed with dynamic scheduling to accomodate numerical pivoting and provides the LU factors distributed over all the processors. Third, the resolution is performed for multiple sources. To compute the gradient of the cost function, 2 simulations per shot are required (one to compute the forward wavefield and one to back-propagate residuals). The multi-source resolutions can be performed in parallel with MUMPS. In the end, each processor stores in core a sub-domain of all the solutions. These distributed solutions can be exploited to compute in parallel the gradient of the cost function. Since the gradient of the cost function is a weighted stack of the shot and residual solutions of MUMPS, each processor
2D Resistive Magnetohydrodynamics Calculations with an Arbitrary Lagrange Eulerian Code
NASA Astrophysics Data System (ADS)
Rousculp, C. L.; Gianakon, T. A.; Lipnikov, K. N.; Nelson, E. M.
2015-11-01
Single fluid resistive MHD is useful for modeling Z-pinch configurations in cylindrical geometry. One such example is thin walled liners for shock physics or HEDP experiments driven by capacitor banks such as the LANL's PHELIX or Sandia-Z. MHD is also useful for modeling high-explosive-driven flux compression generators (FCGs) and their high-current switches. The resistive MHD in our arbitrary Lagrange Eulerian (ALE) code operates in one and two dimensions in both Cartesian and cylindrical geometry. It is implemented as a time-step split operator, which consists of, ideal MHD connected to the explicit hydro momentum and energy equations and a second order mimetic discretization solver for implicit solution of the magnetic diffusion equation. In a staggered grid scheme, a single-component of cell-centered magnetic flux is conserved in the Lagrangian frame exactly, while magnetic forces are accumulated at the nodes. Total energy is conserved to round off. Total flux is conserved under the ALE relaxation and remap. The diffusion solver consistently computes Ohmic heating. Both Neumann and Dirichlet boundary conditions are available with coupling to external circuit models. Example calculations will be shown.
Luo, Y.; Xia, J.; Liu, J.; Xu, Y.; Liu, Q.
2008-01-01
Multichannel Analysis of Surface Waves utilizes a multichannel recording system to estimate near-surface shear (S)-wave velocities from high-frequency Rayleigh waves. A pseudo-2D S-wave velocity (vS) section is constructed by aligning 1D models at the midpoint of each receiver spread and using a spatial interpolation scheme. The horizontal resolution of the section is therefore most influenced by the receiver spread length and the source interval. The receiver spread length sets the theoretical lower limit and any vS structure with its lateral dimension smaller than this length will not be properly resolved in the final vS section. A source interval smaller than the spread length will not improve the horizontal resolution because spatial smearing has already been introduced by the receiver spread. In this paper, we first analyze the horizontal resolution of a pair of synthetic traces. Resolution analysis shows that (1) a pair of traces with a smaller receiver spacing achieves higher horizontal resolution of inverted S-wave velocities but results in a larger relative error; (2) the relative error of the phase velocity at a high frequency is smaller than at a low frequency; and (3) a relative error of the inverted S-wave velocity is affected by the signal-to-noise ratio of data. These results provide us with a guideline to balance the trade-off between receiver spacing (horizontal resolution) and accuracy of the inverted S-wave velocity. We then present a scheme to generate a pseudo-2D S-wave velocity section with high horizontal resolution using multichannel records by inverting high-frequency surface-wave dispersion curves calculated through cross-correlation combined with a phase-shift scanning method. This method chooses only a pair of consecutive traces within a shot gather to calculate a dispersion curve. We finally invert surface-wave dispersion curves of synthetic and real-world data. Inversion results of both synthetic and real-world data demonstrate that
2D Time-lapse Resistivity Monitoring of an Organic Produced Gas Plume in a Landfill using ERT.
NASA Astrophysics Data System (ADS)
Amaral, N. D.; Mendonça, C. A.; Doherty, R.
2014-12-01
This project has the objective to study a landfill located on the margins of Tietê River, in São Paulo, Brazil, using the electroresistivity tomography method (ERT). Due to huge organic matter concentrations in the São Paulo Basin quaternary sediments, there is subsurface depth related biogas accumulation (CH4 and CO2), induced by anaerobic degradation of the organic matter. 2D resistivity sections were obtained from a test area since March 2012, a total of 7 databases, being the last one dated from October 2013. The studied line has the length of 56m, the electrode interval is of 2m. In addition, there are two boreholes along the line (one with 3 electrodes and the other one with 2) in order to improve data quality and precision. The boreholes also have a multi-level sampling system that indicates the fluid (gas or water) presence in relation to depth. With our results it was possible to map the gas plume position and its area of extension in the sections as it is a positive resistivity anomaly, with the gas level having approximately 5m depth. With the time-lapse analysis (Matlab script) between the obtained 2D resistivity sections from the site, it was possible to map how the biogas volume and position change in the landfill in relation to time. Our preliminary results show a preferential gas pathway through the subsurface studied area. A consistent relation between the gas depth and obtained microbiological data from archea and bacteria population was also observed.
NASA Astrophysics Data System (ADS)
Escalona, A.; Sena, A.; Mann, P.
2003-12-01
We have reprocessed and reinterpreted more than 10,000 km of "Gulfrex" multi-channel 2D seismic reflection lines collected by Gulf Oil Corporation in 1972 along the northern margin of South America (offshore Venezuela and Trinidad). These digital data were donated to the University of Texas Institute for Geophysics and represent the largest single, digital reflection survey of the region. Reprocessing of these data included: format correction, filtering, post-stack multiple suppression, and fk migration. Reprocessed data were loaded and interpreted on a workstation. The data straddle a 2,000,000 km2 zone of Paleocene-Recent, time-transgressive, oblique collision between the Caribbean arc system and the passive continental margin of northern South America. Free-air, satellite gravity data shows the remarkable 1000-km-scale continuity of four basement ridges between the uncollided part of the Caribbean arc system (NS-trending Lesser Antilles arc) and the EW-trending collisional area north of Venezuela. The basement ridges involved in the Venezuelan collisional zone include: 1) Aruba-Bonaire-Curacao ridge that can be traced as a continuous feature to the Aves ridge remnant arc of the Lesser Antilles; 2) the partially inverted Blanquilla-Bonaire basin that can be traced into the Grenada back-arc basin; 3) Margarita-Los Testigos platform that can be traced to the Lesser Antilles volcanic arc; and 4) foreland basins and fold-thrust belts of eastern Venezuela (Serrania del Interior and Maturin basin) that can be traced to the Tobago forearc basin and Barbados accretionary prism. Gulfrex data document the progressive change of basinal fault systems from NS-striking normal faults formed in extensional, Lesser Antilles intra-arc settings to rotated and inverted, NE and EW-striking normal faults deformed in the collisional area north of Venezuela. Age of initial shortening of basinal areas and inversion of normal faults setting does not follow the simple, expected pattern of
ERIC Educational Resources Information Center
Brown, Malcolm
2009-01-01
Inversions are fascinating phenomena. They are reversals of the normal or expected order. They occur across a wide variety of contexts. What do inversions have to do with learning spaces? The author suggests that they are a useful metaphor for the process that is unfolding in higher education with respect to education. On the basis of…
Highly crystalline 2D superconductors
NASA Astrophysics Data System (ADS)
Saito, Yu; Nojima, Tsutomu; Iwasa, Yoshihiro
2016-12-01
Recent advances in materials fabrication have enabled the manufacturing of ordered 2D electron systems, such as heterogeneous interfaces, atomic layers grown by molecular beam epitaxy, exfoliated thin flakes and field-effect devices. These 2D electron systems are highly crystalline, and some of them, despite their single-layer thickness, exhibit a sheet resistance more than an order of magnitude lower than that of conventional amorphous or granular thin films. In this Review, we explore recent developments in the field of highly crystalline 2D superconductors and highlight the unprecedented physical properties of these systems. In particular, we explore the quantum metallic state (or possible metallic ground state), the quantum Griffiths phase observed in out-of-plane magnetic fields and the superconducting state maintained in anomalously large in-plane magnetic fields. These phenomena are examined in the context of weakened disorder and/or broken spatial inversion symmetry. We conclude with a discussion of how these unconventional properties make highly crystalline 2D systems promising platforms for the exploration of new quantum physics and high-temperature superconductors.
Breslin, Susan; O'Driscoll, Lorraine
2016-01-01
Solid tumours naturally grow in 3D wherein the spatial arrangement of cells affects how they interact with each other. This suggests that 3D cell culture may mimic the natural in vivo setting better than traditional monolayer (2D) cell culture, where cells are grown attached to plastic. Here, using HER2-positive breast cancer cell lines as models (BT474, HCC1954, EFM192A), the effects of culturing cells in 3D using the poly-HEMA method compared to 2D cultures were assessed in terms of cellular viability, response/resistance to anti-cancer drugs, protein expression and enzyme activity. Scanning electron microscopy showed the morphology of cells in 3D to be substantially different to those cultured in 2D. Cell viability in 3D cells was substantially lower than that of cells in 2D cultures, while 3D cultures were more resistant to the effects of HER-targeted (neratinib) and classical chemotherapy (docetaxel) drugs. Expression of proteins involved in cell survival, transporters associated with drug resistance and drug targets were increased in 3D cultures. Finally, activity of drug metabolising enzyme CYP3A4 was substantially increased in 3D compared to 2D cultures. Together this data indicates that the biological information represented by 3D and 2D cell cultures is substantially different i.e. 3D cell cultures demonstrate higher innate resistance to anti-cancer drugs compared to 2D cultures, which may be facilitated by the altered receptor proteins, drug transporters and metabolising enzyme activity. This highlights the importance of considering 3D in addition to 2D culture methods in pre-clinical studies of both newer targeted and more traditional anti-cancer drugs. PMID:27304190
Breslin, Susan; O'Driscoll, Lorraine
2016-07-19
Solid tumours naturally grow in 3D wherein the spatial arrangement of cells affects how they interact with each other. This suggests that 3D cell culture may mimic the natural in vivo setting better than traditional monolayer (2D) cell culture, where cells are grown attached to plastic. Here, using HER2-positive breast cancer cell lines as models (BT474, HCC1954, EFM192A), the effects of culturing cells in 3D using the poly-HEMA method compared to 2D cultures were assessed in terms of cellular viability, response/resistance to anti-cancer drugs, protein expression and enzyme activity. Scanning electron microscopy showed the morphology of cells in 3D to be substantially different to those cultured in 2D. Cell viability in 3D cells was substantially lower than that of cells in 2D cultures, while 3D cultures were more resistant to the effects of HER-targeted (neratinib) and classical chemotherapy (docetaxel) drugs. Expression of proteins involved in cell survival, transporters associated with drug resistance and drug targets were increased in 3D cultures. Finally, activity of drug metabolising enzyme CYP3A4 was substantially increased in 3D compared to 2D cultures. Together this data indicates that the biological information represented by 3D and 2D cell cultures is substantially different i.e. 3D cell cultures demonstrate higher innate resistance to anti-cancer drugs compared to 2D cultures, which may be facilitated by the altered receptor proteins, drug transporters and metabolising enzyme activity. This highlights the importance of considering 3D in addition to 2D culture methods in pre-clinical studies of both newer targeted and more traditional anti-cancer drugs.
Rodriguez, Brian D.; Sweetkind, Donald S.
2015-01-01
The 3-D inversion was generally able to reproduce the gross resistivity structure of the “known” model, but the simulated conductive volcanic composite unit horizons were often too shallow when compared to the “known” model. Additionally, the chosen computation parameters such as station spacing appear to have resulted in computational artifacts that are difficult to interpret but could potentially be removed with further refinements of the 3-D resistivity inversion modeling technique.
Brooke, B D; Hunt, R H; Chandre, F; Carnevale, P; Coetzee, M
2002-07-01
Anopheles gambiae Giles has been implicated as a major vector of malaria in Africa. A number of paracentric chromosomal inversions have been observed as polymorphisms in wild and laboratory populations of this species. These polymorphisms have been used to demonstrate the existence of five reproductive units in West African populations that are currently described as incipient species. They have also been correlated with various behavioral characteristics such as adaptation to aridity and feeding preference and have been associated with insecticide resistance. Two paracentric inversions namely 2La and 2Rb are highly ubiquitous in the wild and laboratory populations sampled. Both inversions are easily conserved during laboratory colonization of wild material and one shows significant positive heterosis with respect to Hardy-Weinberg proportions. Inversion 2La has previously been associated with dieldrin resistance and inversion 2Rb shows an association with DDT resistance based on this study. The stability and maintenance of these inversions as polymorphisms provides an explanation for the transmission and continued presence of DDT and dieldrin resistance in a laboratory strain of An. gambiae in the absence of insecticide selection pressure. This effect may also be operational in wild populations. Stable inversion polymorphism also provides a possible mechanism for the continual inheritance of suitable genetic factors that otherwise compromise the fitness of genetically modified malaria vector mosquitoes.
The Ritual Dimensions of Resistance: Clowning and Symbolic Inversion.
ERIC Educational Resources Information Center
McLaren, Peter L.
1985-01-01
Draws upon recent fieldwork in a Catholic junior high school to focus on the ritualized behavior of the "class clown," who resists instruction. Calls upon resistance theorists to strive for more conceptual precision in their articulation of the symbolic dimension of transgressive student behavior by utilizing a more multidisciplinary…
NASA Astrophysics Data System (ADS)
Jia, Z.; Zhang, G.; Jiang, G.
2015-12-01
Electrical resistivity tomography (ERT) with borehole-to-surface array employed for mineral explorations in Abag Banner, Inner Mongolia, China. Before the ERT method conducted, the drilling data has been originally measured. By the drilling data, a rough model has been established. The ERT survey line was installed in north-south direction which is perpendicular to the strike direction of mineral vein according the drilling data. In order to study the effect of the drilling data on the inversion resolution, a synthetic resistivity model is carried out. The anomalous body consists of 11 conductivity blocks. We assumed that the drilling data sets are measured from four boreholes. Then, the traditional resistivity inversion and the drilling data constrained resistivity inversion are employed, and the two subsurface resistivity maps obtained. From the maps, the inverted resistivity map by the drilling data constrained resistivity inversion has a better resolution and can describe the anomalous body well, however, the one from the traditional resistivity inversion cannot reveal the subsurface resistivity distribution especially to the depth. By the same way, we conducted traditional resistivity inversion and the drilling data constrained resistivity inversion of field study ERT data, two subsurface resistivity maps obtained. Compared with two resistivity maps, the one from drilling data constrained resistivity inversion have a better resolution, what is more, the maps describe the behaviour of the mineral vein well.
2.5D complex resistivity modeling and inversion using unstructured grids
NASA Astrophysics Data System (ADS)
Xu, Kaijun; Sun, Jie
2016-04-01
The characteristic of complex resistivity on rock and ore has been recognized by people for a long time. Generally we have used the Cole-Cole Model(CCM) to describe complex resistivity. It has been proved that the electrical anomaly of geologic body can be quantitative estimated by CCM parameters such as direct resistivity(ρ0), chargeability(m), time constant(τ) and frequency dependence(c). Thus it is very important to obtain the complex parameters of geologic body. It is difficult to approximate complex structures and terrain using traditional rectangular grid. In order to enhance the numerical accuracy and rationality of modeling and inversion, we use an adaptive finite-element algorithm for forward modeling of the frequency-domain 2.5D complex resistivity and implement the conjugate gradient algorithm in the inversion of 2.5D complex resistivity. An adaptive finite element method is applied for solving the 2.5D complex resistivity forward modeling of horizontal electric dipole source. First of all, the CCM is introduced into the Maxwell's equations to calculate the complex resistivity electromagnetic fields. Next, the pseudo delta function is used to distribute electric dipole source. Then the electromagnetic fields can be expressed in terms of the primary fields caused by layered structure and the secondary fields caused by inhomogeneities anomalous conductivity. At last, we calculated the electromagnetic fields response of complex geoelectric structures such as anticline, syncline, fault. The modeling results show that adaptive finite-element methods can automatically improve mesh generation and simulate complex geoelectric models using unstructured grids. The 2.5D complex resistivity invertion is implemented based the conjugate gradient algorithm.The conjugate gradient algorithm doesn't need to compute the sensitivity matrix but directly computes the sensitivity matrix or its transpose multiplying vector. In addition, the inversion target zones are
NASA Astrophysics Data System (ADS)
Li, Gang; Li, Yuguo
2017-01-01
We present a joint inversion method for the transmitter navigation and the seafloor resistivity for frequency domain marine controlled-source electromagnetic (CSEM) data. The inversion approach is based on the modified BFGS scheme, which has an advantage that one can update the Hessian matrix by using the BFGS scheme rather than computing the Hessian matrix itself during the inversion process. The partial derivatives of the electromagnetic field responses with respect to both the seafloor resistivity and the transmitter navigation parameters including the azimuth, dip and horizontal positions of the transmitter antenna are analytically calculated. We invert for both the navigation parameters of the towed dipole source (including antenna azimuth, dip, and horizontal positions) and seafloor resistivity by using the whole range of data instead of the near-field data (usually source-receiver offset <1 km). An eigenparameter analysis shows that seafloor resistivities and transmitter navigation parameters can be independently resolved, and a better reconstruction can be obtained with multiple frequency data. The inversions of both the synthetical and field data sets indicate that our inversion method can simultaneously reconstruct seafloor resistivity structures and transmitter navigation parameters.
Cai, Xiaohui; Lu, Xuzhang; Jia, Zhuxia; Zhang, Xiuwen; Han, Wenmin; Rong, Xiao; Ma, Lingdi; Zhou, Min; Chen, Baoan
2015-11-01
Leukemic cells can survive after chemotherapy by acquisition of multidrug resistance genes, but other phenotypes related to escape from immune recognition remain elusive. Adriamycin-resistant K562/AO2 cells are less susceptible to elimination by NK cells compared with wild type K562 cells due to lower expression of NKG2D ligands. Treatment of K562/AO2 cells with STAT3 inhibitor VII resulted in reduced expression of multidrug resistance gene P-glycoprotein, and up-regulation of NKG2D ligands on K562/AO2 cells. Meanwhile, K562/AO2 cells treated with STAT3 inhibitor proliferated less and were more susceptible to killing by NK cells than untreated K562/AO2 cells. The enhanced cytotoxicity of NK cells against K562/AO2 cells was partly blocked by treatment of NK cells with anti-NKG2D antibodies. These data suggest that STAT3 contributes to NK cell recognition by modulating NKG2D ligands in K562/AO2 cells, which may a mechanism by which cells survive and cause relapse of leukemia.
NASA Astrophysics Data System (ADS)
Nenna, Vanessa; Pidlisecky, Adam; Knight, Rosemary
2011-10-01
We apply an extended Kalman filter (EKF) approach to inversion of time-lapse electrical resistivity imaging (ERI) field data. The EKF is a method of time series signal processing that incorporates both a state evolution model, describing changes in the physical system, and an observation model, incorporating the physics of the electrical resistivity measurement. We test the feasibility of using an EKF approach to inverting ERI data collected with 2-D surface array geometries. As a first test, we invert synthetic data generated using a simulated recharge event and water saturation distributions converted to electrical conductivity values using an Archie's law relationship. In the synthetic example we demonstrate the impact that the noise structure of the state evolution and the regularization weight have on EKF-estimated model parameters and errors. We then apply the method to inversion of field data collected to monitor changes in electrical conductivity beneath a recharge pond that is part of an aquifer storage and recovery project in northern California. Using lines of electrodes buried at a depth of 0.25 m when the base of the pond is dry, we monitor the wetting front associated with the diversion of stormflow runoff to the pond. Using field data, we demonstrate that by oversampling in time, we are able to apply the so-called random walk model for the state evolution and to build the model of observation noise directly from collected data. EKF-estimated values track changes in conductivity associated with both increasing water content in subsurface sediments and changes in the properties of the pore water, showing the method is a feasible approach for inversion of time-lapse ERI field data.
2008-09-01
nonunique properties of inversion methods, we may often find a solution for one data type, but we must acknowledge that, although it can predict behavior...of density prisms and a suite of 1D fundamental mode group velocities. (a) A single cell with its input geographic coordinate system . (b) For a...H. K., H. Kanamori, P. C. Jennings, and C. Kissling (Eds.) (2002). International Handbook of Earthquake and Engineering Seismology (CD-ROM
Ottaviani, R A; Ashton-Miller, J A; Kothari, S U; Wojtys, E M
1995-01-01
To determine if the height of a basketball shoe alters the maximal inversion and eversion moment that can be actively resisted by the ankle in the frontal plane, we tested 20 healthy, young adult men with no recent ankle injuries. Subjects underwent unipedal functional ankle strength testing under weightbearing conditions at 0 degrees, 16 degrees, and 32 degrees of ankle plantar flexion using a specially designed testing apparatus. Testing was performed with the subject wearing either a low- or a three quarter-top basketball shoe. Shoe height did not significantly affect an individual's ability to actively resist an eversion moment at any angle of ankle plantar flexion. However, tests at 0 degrees of ankle plantar flexion demonstrated that the three quarter-top basketball shoe we tested significantly increased the maximal resistance to an inversion moment by 29.4%. At 16 degrees of ankle plantar flexion, inversion resistance was also significantly improved by 20.4%. These results show that athletic shoe height can significantly increase the active resistance to an inversion moment in moderate ankle plantar flexion. The findings apply to a neutral foot position in the frontal plane, an orientation equivalent to the early phase of a potential ankle sprain.
Al-Menshed, Firas H; Thabit, Jassim M
2017-01-10
2D imaging technique was applied in (8) transects near a pit of contaminated water near contaminated well southeast of Karbala city, Iraq. Each transect was 30 m long with 1 m electrode spacing. Data acquisition was fulfilled by using Wenner electrode array. The resistivity of water-contaminated zone is found less than 3Ω.m and the top dry zone recorded relatively high resistivity (more than 170Ω.m). It is found that the greatest amount of seepage was found moving towards northeast direction coincided with groundwater movement direction, whereas there was no movement towards northwest and southeast directions and restricted on the closest areas to the pit location. The outcomes suggested that the 2D imaging technique is a successful and powerful tool in separating contaminated zone from clear one and in detecting underground seepage depth and moving direction.
NASA Astrophysics Data System (ADS)
Zhai, Cuili; Zhang, Ting
2016-09-01
In this article, we consider the global existence and uniqueness of the solution to the 2D incompressible non-resistive MHD system with non-equilibrium background magnetic field. Our result implies that a strong enough non-equilibrium background magnetic field will guarantee the stability of the nonlinear MHD system. Beside the classical energy method, the interpolation inequalities and the algebraic structure of the equations coming from the incompressibility of the fluid are crucial in our arguments.
Ogbomo, Henry; Michaelis, Martin; Klassert, Denise; Doerr, Hans Wilhelm; Cinatl, Jindrich
2008-01-01
Prolonged treatment of leukemic cells with chemotherapeutic agents frequently results in development of drug resistance. Moreover, selection of drug-resistant cell populations may be associated with changes in malignant properties such as proliferation rate, invasiveness, and immunogenicity. In the present study, the sensitivity of cytarabine (1-β-d-arabinofuranosylcytosine, araC)-resistant and parental human leukemic cell lines (T-lymphoid H9 and acute T-lymphoblastic leukemia Molt-4) to natural killer (NK) cell-mediated killing was investigated. The results obtained demonstrate that araC-resistant H9 and Molt-4 (H9rARAC100 and Molt-4rARAC100) cell lines are more sensitive to NK cell-mediated lysis than their respective parental cell lines. This increased sensitivity was associated with a higher surface expression of ligands for the NK cell-activating receptor NKG2D, notably UL16 binding protein-2 (ULBP-2) and ULBP-3 in H9rARAC100 and Molt-4rARAC100 cell lines. Blocking ULBP-2 and ULBP-3 or NKG2D with monoclonal antibody completely abrogated NK cell lysis. Constitutive phosphorylated extracellular signal-regulated kinase (ERK) but not pAKT was higher in araC-resistant cells than in parental cell lines. Inhibition of ERK using ERK inhibitor PD98059 decreased both ULBP-2/ULBP-3 expression and NK cell cytotoxicity. Furthermore, overexpression of constitutively active ERK in H9 parental cells resulted in increased ULBP-2/ULBP-3 expression and enhanced NK cell lysis. These results demonstrate that increased sensitivity of araC-resistant leukemic cells to NK cell lysis is caused by higher NKG2D ligand expression, resulting from more active ERK signaling pathway. PMID:19048119
Large scale 3-D modeling by integration of resistivity models and borehole data through inversion
NASA Astrophysics Data System (ADS)
Foged, N.; Marker, P. A.; Christansen, A. V.; Bauer-Gottwein, P.; Jørgensen, F.; Høyer, A.-S.; Auken, E.
2014-02-01
We present an automatic method for parameterization of a 3-D model of the subsurface, integrating lithological information from boreholes with resistivity models through an inverse optimization, with the objective of further detailing for geological models or as direct input to groundwater models. The parameter of interest is the clay fraction, expressed as the relative length of clay-units in a depth interval. The clay fraction is obtained from lithological logs and the clay fraction from the resistivity is obtained by establishing a simple petrophysical relationship, a translator function, between resistivity and the clay fraction. Through inversion we use the lithological data and the resistivity data to determine the optimum spatially distributed translator function. Applying the translator function we get a 3-D clay fraction model, which holds information from the resistivity dataset and the borehole dataset in one variable. Finally, we use k means clustering to generate a 3-D model of the subsurface structures. We apply the concept to the Norsminde survey in Denmark integrating approximately 700 boreholes and more than 100 000 resistivity models from an airborne survey in the parameterization of the 3-D model covering 156 km2. The final five-cluster 3-D model differentiates between clay materials and different high resistive materials from information held in resistivity model and borehole observations respectively.
Large-scale 3-D modeling by integration of resistivity models and borehole data through inversion
NASA Astrophysics Data System (ADS)
Foged, N.; Marker, P. A.; Christansen, A. V.; Bauer-Gottwein, P.; Jørgensen, F.; Høyer, A.-S.; Auken, E.
2014-11-01
We present an automatic method for parameterization of a 3-D model of the subsurface, integrating lithological information from boreholes with resistivity models through an inverse optimization, with the objective of further detailing of geological models, or as direct input into groundwater models. The parameter of interest is the clay fraction, expressed as the relative length of clay units in a depth interval. The clay fraction is obtained from lithological logs and the clay fraction from the resistivity is obtained by establishing a simple petrophysical relationship, a translator function, between resistivity and the clay fraction. Through inversion we use the lithological data and the resistivity data to determine the optimum spatially distributed translator function. Applying the translator function we get a 3-D clay fraction model, which holds information from the resistivity data set and the borehole data set in one variable. Finally, we use k-means clustering to generate a 3-D model of the subsurface structures. We apply the procedure to the Norsminde survey in Denmark, integrating approximately 700 boreholes and more than 100 000 resistivity models from an airborne survey in the parameterization of the 3-D model covering 156 km2. The final five-cluster 3-D model differentiates between clay materials and different high-resistivity materials from information held in the resistivity model and borehole observations, respectively.
Parallelized Three-Dimensional Resistivity Inversion Using Finite Elements And Adjoint State Methods
NASA Astrophysics Data System (ADS)
Schaa, Ralf; Gross, Lutz; Du Plessis, Jaco
2015-04-01
The resistivity method is one of the oldest geophysical exploration methods, which employs one pair of electrodes to inject current into the ground and one or more pairs of electrodes to measure the electrical potential difference. The potential difference is a non-linear function of the subsurface resistivity distribution described by an elliptic partial differential equation (PDE) of the Poisson type. Inversion of measured potentials solves for the subsurface resistivity represented by PDE coefficients. With increasing advances in multichannel resistivity acquisition systems (systems with more than 60 channels and full waveform recording are now emerging), inversion software require efficient storage and solver algorithms. We developed the finite element solver Escript, which provides a user-friendly programming environment in Python to solve large-scale PDE-based problems (see https://launchpad.net/escript-finley). Using finite elements, highly irregular shaped geology and topography can readily be taken into account. For the 3D resistivity problem, we have implemented the secondary potential approach, where the PDE is decomposed into a primary potential caused by the source current and the secondary potential caused by changes in subsurface resistivity. The primary potential is calculated analytically, and the boundary value problem for the secondary potential is solved using nodal finite elements. This approach removes the singularity caused by the source currents and provides more accurate 3D resistivity models. To solve the inversion problem we apply a 'first optimize then discretize' approach using the quasi-Newton scheme in form of the limited-memory Broyden-Fletcher-Goldfarb-Shanno (L-BFGS) method (see Gross & Kemp 2013). The evaluation of the cost function requires the solution of the secondary potential PDE for each source current and the solution of the corresponding adjoint-state PDE for the cost function gradients with respect to the subsurface
He, Jing-Jing; Guo, Yan-Dong; Yan, Xiao-Hong
2017-01-01
Motivated by the fabrication of layered two-dimensional material C2N-h2D [Nat. Commun. 6, 6486 (2015)], we cut the single-layer C2N-h2D into a zigzag nanoribbon and perform a theoretical study. The results indicate that the band structure changes from semiconducting to metallic and a negative differential resistance effect occurs in the I-V curve. Interestingly, the current can be reduced to zero and this insulator-like state can be maintained as the bias increases. We find this unique property is originated from a peculiar band morphology, with only two subbands appearing around the Fermi level while others being far away. Furthermore the width and symmetry of the zigzag C2N-h2D nanoribbon can be used to tune the transport properties, such as cut-off bias and the maximum current. We also explore the electron transport property of an aperiodic model composed of two nanoribbons with different widths and obtain the same conclusion. This mechanism can be extended to other systems, e.g., hybrid BCN nanoribbons. Our discoveries suggest that the zigzag C2N-h2D nanoribbon has great potential in nanoelectronics applications. PMID:28382947
NASA Astrophysics Data System (ADS)
Xiang, S.; Zhang, H.
2015-12-01
2D wide-angle seismic reflection/refraction survey has been widely used to investigate crustal structure and Moho topography. Similarly gravity survey is also very important in the study of local and regional earth features. Seismic survey is sensitive to the seismic velocity parameters and interface variations. For gravity survey, it is sensitive to density parameters of the medium but the resolution along the vertical direction is relatively poor. In this study, we have developed a strategy to jointly invert for seismic velocity model, density model and interface positions using the gravity observations and seismic arrival times from different phases. For the joint inversion of seismic and gravity data, it often relies on the empirical relationship between seismic velocity and density. In comparison, our joint inversion strategy also includes the cross-gradient based structure constraint for seismic velocity and density models in addition to the empirical relationship between them. The objective function for the joint inversion includes data misfit terms for seismic travel times and gravity observations, the cross-gradient constraint, the smoothness terms for two models, and the data misfit term between predicted gravity data based on density model converted from velocity model using the empirical relationship. Each term has its respective weight. We have applied the new joint inversion method to the Riwoqe-Yushu-Maduo profile in northwest China. The profile crosses through the Qiangtang block and Bayan Har block from southwest to northeast, respectively. The 2010 Ms 7.1 Yushu earthquake is located on the profile, around the Ganzi-Yushu fault zone. The joint inversion produces the velocity and density models that are similar in structure and at the same time fit their respective data sets well. Compared to separate seismic inversion using seismic travel times, the joint inversion with gravity data gives a velocity model that better delineates the fault zones. Low
NASA Astrophysics Data System (ADS)
Liu, B.; Li, S. C.; Nie, L. C.; Wang, J.; L, X.; Zhang, Q. S.
2012-12-01
Traditional inversion method is the most commonly used procedure for three-dimensional (3D) resistivity inversion, which usually takes the linearization of the problem and accomplish it by iterations. However, its accuracy is often dependent on the initial model, which can make the inversion trapped in local optima, even cause a bad result. Non-linear method is a feasible way to eliminate the dependence on the initial model. However, for large problems such as 3D resistivity inversion with inversion parameters exceeding a thousand, main challenges of non-linear method are premature and quite low search efficiency. To deal with these problems, we present an improved Genetic Algorithm (GA) method. In the improved GA method, smooth constraint and inequality constraint are both applied on the object function, by which the degree of non-uniqueness and ill-conditioning is decreased. Some measures are adopted from others by reference to maintain the diversity and stability of GA, e.g. real-coded method, and the adaptive adjustment of crossover and mutation probabilities. Then a generation method of approximately uniform initial population is proposed in this paper, with which uniformly distributed initial generation can be produced and the dependence on initial model can be eliminated. Further, a mutation direction control method is presented based on the joint algorithm, in which the linearization method is embedded in GA. The update vector produced by linearization method is used as mutation increment to maintain a better search direction compared with the traditional GA with non-controlled mutation operation. By this method, the mutation direction is optimized and the search efficiency is improved greatly. The performance of improved GA is evaluated by comparing with traditional inversion results in synthetic example or with drilling columnar sections in practical example. The synthetic and practical examples illustrate that with the improved GA method we can eliminate
Radiation-induced resistance oscillations in a 2D hole gas: a demonstration of a universal effect
NASA Astrophysics Data System (ADS)
Iñarrea, Jesús; Platero, Gloria
2015-09-01
We report on a theoretical study about the microwave-induced resistance oscillations and zero resistance states when dealing with p-type semiconductors and holes instead of electrons. We consider a high-mobility two-dimensional hole gas hosted in a pure Ge/SiGe quantum well. Similarly to electrons we obtain radiation-induced resistance oscillations and zero resistance states. We analytically deduce a universal expression for the irradiated magnetoresistance, explaining the origin of the minima positions and their 1/4 cycle phase shift. The outcome is that these phenomena are universal and only depend on radiation and cyclotron frequencies. We also study the possibility of having simultaneously two different carriers driven by radiation: light and heavy holes. As a result the calculated magnetoresistance reveals an interference profile due to the different effective masses of the two types of carriers.
Inversion 2La is associated with enhanced desiccation resistance in Anopheles gambiae
Gray, Emilie M; Rocca, Kyle AC; Costantini, Carlo; Besansky, Nora J
2009-01-01
Background Anopheles gambiae, the principal vector of malignant malaria in Africa, occupies a wide range of habitats. Environmental flexibility may be conferred by a number of chromosomal inversions non-randomly associated with aridity, including 2La. The purpose of this study was to determine the physiological mechanisms associated with the 2La inversion that may result in the preferential survival of its carriers in hygrically-stressful environments. Methods Two homokaryotypic populations of A. gambiae (inverted 2La and standard 2L+a) were created from a parental laboratory colony polymorphic for 2La and standard for all other known inversions. Desiccation resistance, water, energy and dry mass of adult females of both populations were compared at several ages and following acclimation to a more arid environment. Results Females carrying 2La were significantly more resistant to desiccation than 2L+a females at emergence and four days post-emergence, for different reasons. Teneral 2La females had lower rates of water loss than their 2L+a counterparts, while at four days, 2La females had higher initial water content. No differences in desiccation resistance were found at eight days, with or without acclimation. However, acclimation resulted in both populations significantly reducing their rates of water loss and increasing their desiccation resistance. Acclimation had contrasting effects on the body characteristics of the two populations: 2La females boosted their glycogen stores and decreased lipids, whereas 2La females did the contrary. Conclusion Variation in rates of water loss and response to acclimation are associated with alternative arrangements of the 2La inversion. Understanding the mechanisms underlying these traits will help explain how inversion polymorphisms permit exploitation of a heterogeneous environment by this disease vector. PMID:19772577
Three dimensional modeling and inversion of Borehole-surface Electrical Resistivity Data
NASA Astrophysics Data System (ADS)
Zhang, Y.; Liu, D.; Liu, Y.; Qin, M.
2013-12-01
After a long time of exploration, many oil fields have stepped into the high water-cut period. It is sorely needed to determining the oil-water distribution and water flooding front. Borehole-surface electrical resistivity tomography (BSERT) system is a low-cost measurement with wide measuring scope and small influence on the reservoir. So it is gaining more and more application in detecting water flooding areas and evaluating residual oil distribution in oil fields. In BSERT system, current is connected with the steel casing of the observation well. The current flows along the long casing and transmits to the surface through inhomogeneous layers. Then received electric potential difference data on the surface can be used to inverse the deep subsurface resistivity distribution. This study presents the 3D modeling and inversion method of electrical resistivity data. In an extensive literature, the steel casing is treated as a transmission line current source with infinite small radius and constant current density. However, in practical multi-layered formations with different resistivity, the current density along the casing is not constant. In this study, the steel casing is modeled by a 2.5e-7 ohm-m physical volume that the casing occupies in the finite element mesh. Radius of the casing can be set to a little bigger than the true radius, and this helps reduce the element number and computation time. The current supply point is set on the center of the top surface of the physical volume. The homogeneous formation modeling result shows the same precision as the transmission line current source model. The multi-layered formation modeling result shows that the current density along the casing is high in the low-resistivity layer, and low in the high-resistivity layer. These results are more reasonable. Moreover, the deviated and horizontal well can be simulated as simple as the vertical well using this modeling method. Based on this forward modeling method, the
NASA Astrophysics Data System (ADS)
Noh, H.; Tsui, D. C.; Shayegan, M.; Yoon, Jongsoo
2000-03-01
We report on measurements of anisotropic in-plane magneto-resistance of the 2D hole system (2DHS) in a GaAs/AlGaAs (311)A heterostructure, which exhibits both zero-field and in-plane field induced metal-insulator transitions. For high hole densities, when the direction of B field is changed relative to the current(I), which is always kept in the high mobility direction, the resistivity with B allel I is larger at low field, while the resistivity with B ⊥ I becomes larger at high field. This behavior is consistent with recent measurements(S. J. Papadakis et al.), cond-mat/9911239. on a quantum well system. That the resistivity at high field is larger for B ⊥ I than for B allel I is also consistent with a recent theoretical argument(S. Das Sarma and E. H. Hwang, cond-mat/9909452.), though the difference is smaller than that from the theory. As the density is lowered, the resistivity with B allel I gets larger at high field, and it eventually becomes greater than that with B ⊥ I at all field ranges measured. This change in anisotropy has not been seen in previous measurements. The critical field B_c, beyond which the metallic phase becomes insulating, is also different for two different directions of B, while the change in I-V characteristics across Bc remains the same.
Peripheral cannabinoid-1 receptor inverse agonism reduces obesity by reversing leptin resistance.
Tam, Joseph; Cinar, Resat; Liu, Jie; Godlewski, Grzegorz; Wesley, Daniel; Jourdan, Tony; Szanda, Gergő; Mukhopadhyay, Bani; Chedester, Lee; Liow, Jeih-San; Innis, Robert B; Cheng, Kejun; Rice, Kenner C; Deschamps, Jeffrey R; Chorvat, Robert J; McElroy, John F; Kunos, George
2012-08-08
Obesity-related leptin resistance manifests in loss of leptin's ability to reduce appetite and increase energy expenditure. Obesity is also associated with increased activity of the endocannabinoid system, and CB(1) receptor (CB(1)R) inverse agonists reduce body weight and the associated metabolic complications, although adverse neuropsychiatric effects halted their therapeutic development. Here we show that in mice with diet-induced obesity (DIO), the peripherally restricted CB(1)R inverse agonist JD5037 is equieffective with its brain-penetrant parent compound in reducing appetite, body weight, hepatic steatosis, and insulin resistance, even though it does not occupy central CB(1)R or induce related behaviors. Appetite and weight reduction by JD5037 are mediated by resensitizing DIO mice to endogenous leptin through reversing the hyperleptinemia by decreasing leptin expression and secretion by adipocytes and increasing leptin clearance via the kidney. Thus, inverse agonism at peripheral CB(1)R not only improves cardiometabolic risk in obesity but has antiobesity effects by reversing leptin resistance.
NASA Astrophysics Data System (ADS)
Besson, Arlène; Seger, Maud; Richard, Guy; Nicoullaud, Bernard; Giot, Guillaume; Cousin, Isabelle
2010-05-01
The soil structure is complex, heterogeneous, space and time scale dependent, submitted to the climate, biological activity and human practices. For instance, in agricultural context, when soil management practices aim at developing desirable soil conditions for a seedbed and establishing specific surface configuration for planting, drainage or harvesting operations, they can also induce soil structural disturbances, as compaction resulting on in-field wheel traffic. These intense soil degradations have a drastic impact on soil functioning and plant growth but are not absolutely irreversible. Indeed, earthworm's activity, root growth and climate improve the soil structure by cracking, by developing voids, channels, by a progressive fragmentation and disaggregation of the initial dense matrix. Despite this natural structural resilience process of soils is well known, its empirical evidence at the macroscopic scale remains challenging. This requires a well detailed characterization of structural components in space and time. The objective of this study was to monitor the structural changes of a loamy tilled layer initially compacted locally by wheel traffic. In the field, two zones were analysed: (1) a bare soil in view of describing mainly the impact of the climate on the soil structure and (2) a cultivated soil in view of describing the cumulative effect of the climate and root growth on the soil structure. For both, the non destructive and exhaustive method of Electrical Resistivity Tomography (ERT) has been used to monitor the structural changes from April to August, i.e. during the complete growing season. In addition, the interpretation of ERT was comforted by several visual descriptions of soil structure, realized on soil pits dug at the same location than the ERT profiles and by bulk density measurements from soil samples. Due to their high impact on electrical resistivity, water content and soil temperature were also monitored during the experiment. The
NASA Astrophysics Data System (ADS)
Kellerer-Pirklbauer, Andreas
2015-04-01
Mountain permafrost covers some 2000 km² of the Austrian Alps which is less than 2.5% of the national territory. Delineating the altitudinal lower limit of permafrost in the mountains of Austria is difficult due the complex topography, the rather sparseness of field verification data and the lack of long-term permafrost monitoring data. Such monitoring data should cover different slope aspects, different elevations, different substrates and different mountain regions of Austria. In this study it was attempted to delineate the lower limit of permafrost at two study sites in the Tauern Range, Austria, applying two-dimensional geoelectrical resistivity tomography (ERT). In addition, multi-annual ground temperature data collected by miniature temperature datalogger (MDT) were used to validate the results. At the study site Hochreichart (maximum elevation 2416 m asl), located in the Seckauer Tauern Range, 14 ERT profiles (lengths 48-196 m; electrode spacing 2, 2.5 or 4 m) were measured at elevations between 1805 and 2416 m asl. Measurements were carried out at two cirques (Reichart, Schöneben) and at the summit plateau of Hochreichart. Results at this site indicate that permafrost lenses are detectable at elevations down to c.1900 m asl at radiation-sheltered sites. Furthermore, at the summit plateau permafrost only occurs as rather small lenses. The ERT-based permafrost pattern is generally confirmed by the MTD data with negative mean annual ground temperature values at only a few monitoring sites. However, the possibility of air-filled cavities causing higher resistive zones faking permafrost existence cannot be excluded because coarse-grained sediments (i.e. relict rock glaciers and autochthonous block fields) are widespread at this study site. At the second study site Kögele Cirque (maximum elevation 3030 m asl) located in the Schober Mountains 12 ERT profiles (lengths 48 m; electrode spacing 2 m) were measured at elevations between 2631 and 2740 m asl. Spatially
A hybrid method for inversion of 3D DC resistivity logging measurements.
Gajda-Zagórska, Ewa; Schaefer, Robert; Smołka, Maciej; Paszyński, Maciej; Pardo, David
This paper focuses on the application of hp hierarchic genetic strategy (hp-HGS) for solution of a challenging problem, the inversion of 3D direct current (DC) resistivity logging measurements. The problem under consideration has been formulated as the global optimization one, for which the objective function (misfit between computed and reference data) exhibits multiple minima. In this paper, we consider the extension of the hp-HGS strategy, namely we couple the hp-HGS algorithm with a gradient based optimization method for a local search. Forward simulations are performed with a self-adaptive hp finite element method, hp-FEM. The computational cost of misfit evaluation by hp-FEM depends strongly on the assumed accuracy. This accuracy is adapted to the tree of populations generated by the hp-HGS algorithm, which makes the global phase significantly cheaper. Moreover, tree structure of demes as well as branch reduction and conditional sprouting mechanism reduces the number of expensive local searches up to the number of minima to be recognized. The common (direct and inverse) accuracy control, crucial for the hp-HGS efficiency, has been motivated by precise mathematical considerations. Numerical results demonstrate the suitability of the proposed method for the inversion of 3D DC resistivity logging measurements.
Adipose tissue α-linolenic acid is inversely associated with insulin resistance in adults1
Sabaté, Joan
2016-01-01
Background: There is emerging evidence of the beneficial effects of n–3 (ω-3) fatty acids (FAs) on cardiometabolic risk factors. Nevertheless, not much is known about the association between adipose tissue α-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) and insulin resistance. Objective: We determined the association between adipose tissue n–3 FAs (total n–3 FAs, ALA, and EPA plus DHA) and insulin resistance in healthy adults. Design: In this cross-sectional study, multivariable analyses were used to assess the association between adipose tissue FAs (ALA, EPA plus DHA, and total n–3 FAs) and the homeostasis model assessment of insulin resistance (HOMA-IR) in a subset of adult participants (n = 716; mean age: 58 y) from the Adventist Health Study-2 (AHS-2) cohort. Results: Compared with the lowest tertile, the third tertile (β = −0.13; 95% CI: −0.24, −0.01) of adipose tissue ALA was inversely associated with the HOMA-IR. When stratified by waist circumference, ALA continued to be inversely associated [third tertile: β = −0.17 (95% CI: −0.31, −0.02)] with the HOMA-IR in subjects with a waist circumference ≤88 cm in women or ≤102 cm in men but not in those with a larger waist circumference. No significant association was noted between adipose tissue EPA plus DHA and HOMA-IR. Conclusions: Higher adipose tissue ALA was inversely associated with insulin resistance in this cohort of healthy adult men and women. This finding appears to be more pronounced in individuals with a normal waist circumference. PMID:26912497
2D semiconductor optoelectronics
NASA Astrophysics Data System (ADS)
Novoselov, Kostya
The advent of graphene and related 2D materials has recently led to a new technology: heterostructures based on these atomically thin crystals. The paradigm proved itself extremely versatile and led to rapid demonstration of tunnelling diodes with negative differential resistance, tunnelling transistors, photovoltaic devices, etc. By taking the complexity and functionality of such van der Waals heterostructures to the next level we introduce quantum wells engineered with one atomic plane precision. Light emission from such quantum wells, quantum dots and polaritonic effects will be discussed.
Control of wire heating with resistively guided fast electrons through an inverse conical taper
Robinson, A. P. L. Schmitz, H.; Green, J. S.; Booth, N.; Ridgers, C. P.; Pasley, J.
2015-04-15
The heating of a solid wire embedded in a solid substrate (of lower Z material) with relativistic electrons generated by ultra-intense laser irradiation is considered. Previously, it has been noted that the initial angular distribution of the fast electrons is a highly important factor in the efficacy of the heating [Robinson et al., Phys. Plasmas 20, 122701 (2013)]. We show that, using 3D numerical simulations, the addition of an inverse conical taper at the front of wire can considerably improve the heating of the wire due to the reduction of angular spread of the fast electrons which is caused by transport through the inverse conical taper [Robinson et al., “Guiding of laser-generated fast electrons by exploiting the resistivity-gradients around a conical guide element,” Plasma Phys. Controlled Fusion (to be published)].
Kura, Nura Umar; Ramli, Mohammad Firuz; Ibrahim, Shaharin; Sulaiman, Wan Nor Azmin; Zaudi, Muhammad Amar; Aris, Ahmad Zaharin
2014-01-01
The existing knowledge regarding seawater intrusion and particularly upconing, in which both problems are linked to pumping, entirely relies on theoretical assumptions. Therefore, in this paper, an attempt is made to capture the effects of pumping on seawater intrusion and upconing using 2D resistivity measurement. For this work, two positions, one perpendicular and the other parallel to the sea, were chosen as profile line for resistivity measurement in the coastal area near the pumping wells of Kapas Island, Malaysia. Subsequently, water was pumped out of two pumping wells simultaneously for about five straight hours. Then, immediately after the pumping stopped, resistivity measurements were taken along the two stationed profile lines. This was followed by additional measurements after four and eight hours. The results showed an upconing with low resistivity of about 1-10 Ωm just beneath the pumping well along the first profile line that was taken just after the pumping stopped. The resistivity image also shows an intrusion of saline water (water enriched with diluted salt) from the sea coming towards the pumping well with resistivity values ranging between 10 and 25 Ωm. The subsequent measurements show the recovery of freshwater in the aquifer and how the saline water is gradually diluted or pushed out of the aquifer. Similarly the line parallel to the sea (L2) reveals almost the same result as the first line. However, in the second and third measurements, there were some significant variations which were contrary to the expectation that the freshwater may completely flush out the saline water from the aquifer. These two time series lines show that as the areas with the lowest resistivity (1 Ωm) shrink with time, the low resistivity (10 Ωm) tends to take over almost the entire area implying that the freshwater-saltwater equilibrium zone has already been altered. These results have clearly enhanced our current understanding and add more scientific
Ramli, Mohammad Firuz; Ibrahim, Shaharin; Sulaiman, Wan Nor Azmin; Aris, Ahmad Zaharin
2014-01-01
The existing knowledge regarding seawater intrusion and particularly upconing, in which both problems are linked to pumping, entirely relies on theoretical assumptions. Therefore, in this paper, an attempt is made to capture the effects of pumping on seawater intrusion and upconing using 2D resistivity measurement. For this work, two positions, one perpendicular and the other parallel to the sea, were chosen as profile line for resistivity measurement in the coastal area near the pumping wells of Kapas Island, Malaysia. Subsequently, water was pumped out of two pumping wells simultaneously for about five straight hours. Then, immediately after the pumping stopped, resistivity measurements were taken along the two stationed profile lines. This was followed by additional measurements after four and eight hours. The results showed an upconing with low resistivity of about 1–10 Ωm just beneath the pumping well along the first profile line that was taken just after the pumping stopped. The resistivity image also shows an intrusion of saline water (water enriched with diluted salt) from the sea coming towards the pumping well with resistivity values ranging between 10 and 25 Ωm. The subsequent measurements show the recovery of freshwater in the aquifer and how the saline water is gradually diluted or pushed out of the aquifer. Similarly the line parallel to the sea (L2) reveals almost the same result as the first line. However, in the second and third measurements, there were some significant variations which were contrary to the expectation that the freshwater may completely flush out the saline water from the aquifer. These two time series lines show that as the areas with the lowest resistivity (1 Ωm) shrink with time, the low resistivity (10 Ωm) tends to take over almost the entire area implying that the freshwater-saltwater equilibrium zone has already been altered. These results have clearly enhanced our current understanding and add more scientific
Lincet, Hubert; Guével, Blandine; Pineau, Charles; Allouche, Stéphane; Lemoisson, Edwige; Poulain, Laurent; Gauduchon, Pascal
2012-02-02
Ovarian cancer is the fifth most frequent cause of cancer death in women. Emergence of chemoresistance in the course of treatments with platinum drugs is in part responsible for therapeutic failures. In order to improve the understanding of the complex mechanisms involved in acquired platinum chemoresistance, we decided to compare the basal protein expression profile of the platinum-sensitive cell line OAW42 and that of its resistant counterpart OAW42-R by a proteomic approach. Reversed-phase HPLC pre-fractionated extracts from both cell lines were subjected to 2D-DIGE coupled to mass spectrometry (MS). Forty eight differentially expressed proteins were identified, 39 being up-regulated and 19 down-regulated in OAW42-R versus OAW42 cells. From the current knowledge on biological activities of most differentially expressed proteins, it can be inferred that the acquisition of resistance was associated with a global reorganization of biochemical pathways favoring the production of precursors for biosynthesis, and with the mobilization of macromolecule quality control mechanisms, preserving RNA and protein integrity under damage-inducing conditions.
NASA Astrophysics Data System (ADS)
Papadakis, S. J.; de Poortere, E. P.; Shayegan, M.; Winkler, R.
2000-03-01
We report experiments on (311)A GaAs 2D holes at 0.3 - 1.4 K with an in-plane magnetic field B. The density range (1.3 × 10^10 < p < 6.6 × 10^10 cm-2) is such that the temperature dependence of the resistivity is metallic-like at B = 0. In all cases the system displays positive magnetoresistance whose details depend on the relative orientations of B and the crystal axes as well as of B and the current (I) direction.(S. J. Papadakis et al.), cond-mat/9911239. We observe a feature in the magnetoresistance, associated with a spin-subband de-population, whose B-position changes when the field direction is changed from [bar233] to [01bar1]. Near this feature, there is a critical field BT beyond which the behavior changes to insulating. B_T, too, changes when the orientation of B relative to the crystal axes is changed. Changing the direction of I with respect to B also affects the positions of these features, but to a much smaller degree. The data are consistent with the idea that two spin-subbands with different populations are necessary for the existence of the B = 0 metallic behavior, and are also a clear demonstration of the anisotropy of the band structure of GaAs 2D holes grown on (311)A substrates.
2D superconductivity by ionic gating
NASA Astrophysics Data System (ADS)
Iwasa, Yoshi
2D superconductivity is attracting a renewed interest due to the discoveries of new highly crystalline 2D superconductors in the past decade. Superconductivity at the oxide interfaces triggered by LaAlO3/SrTiO3 has become one of the promising routes for creation of new 2D superconductors. Also, the MBE grown metallic monolayers including FeSe are also offering a new platform of 2D superconductors. In the last two years, there appear a variety of monolayer/bilayer superconductors fabricated by CVD or mechanical exfoliation. Among these, electric field induced superconductivity by electric double layer transistor (EDLT) is a unique platform of 2D superconductivity, because of its ability of high density charge accumulation, and also because of the versatility in terms of materials, stemming from oxides to organics and layered chalcogenides. In this presentation, the following issues of electric filed induced superconductivity will be addressed; (1) Tunable carrier density, (2) Weak pinning, (3) Absence of inversion symmetry. (1) Since the sheet carrier density is quasi-continuously tunable from 0 to the order of 1014 cm-2, one is able to establish an electronic phase diagram of superconductivity, which will be compared with that of bulk superconductors. (2) The thickness of superconductivity can be estimated as 2 - 10 nm, dependent on materials, and is much smaller than the in-plane coherence length. Such a thin but low resistance at normal state results in extremely weak pinning beyond the dirty Boson model in the amorphous metallic films. (3) Due to the electric filed, the inversion symmetry is inherently broken in EDLT. This feature appears in the enhancement of Pauli limit of the upper critical field for the in-plane magnetic fields. In transition metal dichalcogenide with a substantial spin-orbit interactions, we were able to confirm the stabilization of Cooper pair due to its spin-valley locking. This work has been supported by Grant-in-Aid for Specially
Wallin, Erin L.; Johnson, Timothy C.; Greenwood, William J.; Zachara, John M.
2013-03-29
The Hanford 300 Area is located adjacent to the Columbia River in south-central Washington State, USA, and was a former site for nuclear fuel processing operations. Waste disposal practices resulted in persistent unsaturated zone and groundwater contamination, the primary contaminant of concern being uranium. Uranium behavior at the site is intimately linked with river stage driven groundwater-river water exchange such that understanding the nature of river water intrusion into the 300 Area is critical for predicting uranium desorption and transport. In this paper we use time-lapse electrical resistivity tomography (ERT) to image the inland intrusion of river during high stage conditions. We demonstrate a modified time-lapse inversion approach, whereby the transient water table elevation is explicitly modeled by removing regularization constraints across the water table boundary. This implementation was critical for producing meaningful imaging results. We inverted approximately 1200 data sets (400 per line over 3 lines) using high performance computing resources to produce a time-lapse sequence of changes in bulk conductivity caused by river water intrusion during the 2011 spring runoff cycle over approximately 125 days. The resulting time series for each mesh element was then analyzed using common time series analysis to reveal the timing and location of river water intrusion beneath each line. The results reveal non-uniform flows characterized by preferred flow zones where river water enters and exits quickly with stage increase and decrease, and low permeability zones with broader bulk conductivity ‘break through’ curves and longer river water residence times. The time-lapse ERT inversion approach removes the deleterious effects of changing water table elevation and enables remote and spatial continuous groundwater-river water exchange monitoring using surface based ERT arrays under conditions where groundwater and river water conductivity are in contrast.
Stefan, Christopher P.; Koehler, Jeffrey W.; Minogue, Timothy D.
2016-01-01
Antibiotic resistance (AR) is an epidemic of increasing magnitude requiring rapid identification and profiling for appropriate and timely therapeutic measures and containment strategies. In this context, ciprofloxacin is part of the first-line of countermeasures against numerous high consequence bacteria. Significant resistance can occur via single nucleotide polymorphisms (SNP) and deletions within ciprofloxacin targeted genes. Ideally, use of ciprofloxacin would be prefaced with AR determination to avoid overuse or misuse of the antibiotic. Here, we describe the development and evaluation of a panel of 44 single-stranded molecular inversion probes (MIPs) coupled to next-generation sequencing (NGS) for the detection of genetic variants known to confer ciprofloxacin resistance in Bacillus anthracis, Yersinia pestis, and Francisella tularensis. Sequencing results demonstrate MIPs capture and amplify targeted regions of interest at significant levels of coverage. Depending on the genetic variant, limits of detection (LOD) for high-throughput pooled sequencing ranged from approximately 300–1800 input genome copies. LODs increased 10-fold in the presence of contaminating human genome DNA. In addition, we show that MIPs can be used as an enrichment step with high resolution melt (HRM) real-time PCR which is a sensitive assay with a rapid time-to-answer. Overall, this technology is a multiplexable upfront enrichment applicable with multiple downstream molecular assays for the detection of targeted genetic regions. PMID:27174456
Lehikoinen, A.; Huttunen, J.M.J.; Finsterle, S.; Kowalsky, M.B.; Kaipio, J.P.
2009-08-01
We propose an approach for imaging the dynamics of complex hydrological processes. The evolution of electrically conductive fluids in porous media is imaged using time-lapse electrical resistance tomography. The related dynamic inversion problem is solved using Bayesian filtering techniques, that is, it is formulated as a sequential state estimation problem in which the target is an evolving posterior probability density of the system state. The dynamical inversion framework is based on the state space representation of the system, which involves the construction of a stochastic evolution model and an observation model. The observation model used in this paper consists of the complete electrode model for ERT, with Archie's law relating saturations to electrical conductivity. The evolution model is an approximate model for simulating flow through partially saturated porous media. Unavoidable modeling and approximation errors in both the observation and evolution models are considered by computing approximate statistics for these errors. These models are then included in the construction of the posterior probability density of the estimated system state. This approximation error method allows the use of approximate - and therefore computationally efficient - observation and evolution models in the Bayesian filtering. We consider a synthetic example and show that the incorporation of an explicit model for the model uncertainties in the state space representation can yield better estimates than a frame-by-frame imaging approach.
NASA Astrophysics Data System (ADS)
Lane, J. W.; Day-Lewis, F. D.; Loke, M. H.; White, E. A.
2005-12-01
Water-borne continuous resistivity profiling (CRP), also called marine or streaming resistivity, increasingly is used to support hydrogeophysical studies in freshwater and saltwater environments. CRP can provide resistivity tomograms for delineation of focused ground-water discharge, identification of sediment types, and mapping the near-shore freshwater/saltwater interface. Data collection, performed with a boat-towed electrode streamer, is commonly fast and relatively straightforward. In contrast, data processing and interpretation are potentially time consuming and subject to pitfalls. Data analysis is difficult due to the underdetermined nature of the tomographic inverse problem and the poorly understood resolution of tomograms, which is a function of the measurement physics, survey geometry, measurement error, and inverse problem parameterization and regularization. CRP data analysis in particular is complicated by noise in the data, sources of which include water leaking into the electrode cable, inefficient data collection geometry, and electrode obstruction by vegetation in the water column. Preliminary modeling has shown that, as in other types of geotomography, inversions of CRP data tend to overpredict the extent of and underpredict the magnitude of resistivity anomalies. Previous work also has shown that the water layer has a strong effect on the measured apparent resistivity values as it commonly has a much lower resistivity than the subsurface. Here we use synthetic examples and inverted field data sets to (1) assess the ability of CRP to resolve hydrogeophysical targets of interest for a range of water depths and salinities; and (2) examine the effects of CRP streamer noise on inverted resistivity sections. Our results show that inversion and interpretation of CRP data should be guided by hydrologic insight, available data for bathymetry and water layer resistivity, and a reliable model of measurement errors.
NASA Astrophysics Data System (ADS)
Demirci, İsmail; Candansayar, Mehmet Emin; Vafidis, Antonis; Soupios, Pantelis
2017-04-01
Direct current resistivity, radio-magnetotelluric and seismic refraction methods are widely used in the identification of near surface structures with collected data generally being interpreted separately. In recent decades, the use of joint inversion algorithms in geosciences has become widespread to identify near surface structures. However, there is no developed joint inversion algorithm using direct current resistivity, radio-magnetotelluric and seismic refraction methods. In this study, we developed a new two-dimensional joint inversion algorithm for direct current resistivity, radio-magnetotelluric and seismic refraction data based on a cross gradient approach. In addition, we proposed a new data weighting matrix to stabilize the convergence behavior of the joint inversion algorithms. We used synthetic data to show the advantage of the algorithm. The developed joint inversion algorithm found resistivity and velocity models that are better than the individual inversion of each data set. We also tested an algorithm with the field data collected in the Bafra Plain (Samsun, Turkey) to investigate saltwater intrusion. In comparing the field data inversion results with the sounding log, it can be seen that the developed joint inversion algorithm with the proposed data weighting matrix recovered the resistivity and velocity model better than the individual inversion and classical joint inversion of each data set. Our results showed that a more unique hydrogeological scenario might be obtained, especially in highly conductive media, with the joint usage of these methods.
NASA Astrophysics Data System (ADS)
Oware, E. K.; Moysey, S. M.
2013-12-01
Traditional Tikhonov regularization is independent of the physical mechanisms driving state variables targeted by geophysical imaging systems. Hence, Proper Orthogonal Decomposition (POD) based inversion was previously introduced to include physics-based a priori information in constraining the imaging problem. The POD approach uses training data to extract a set of basis vectors that can be used within a basis-constrained inversion algorithm, where the training data are selected to represent possible distributions of a state variable that are consistent with the prevalent driving physical processes. For resistivity imaging of groundwater solutes the POD inversion approach involves Monte Carlo simulation of flow and transport in order to generate a training dataset, thereby intrinsically capturing the perceived physics of the underlying processes driving the subsurface electrical resistivity distribution in a non-parametric fashion. A key element of the POD technique presented previously involves the alignment of the Center of Mass (CoM) of all concentration training images at the true CoM of the solute plume being imaged, prior to extracting the POD basis patterns. The constructed basis was then used for constraining the data inversion procedure. This contribution seeks to study the robustness of the technique under varying degrees of uncertainty in the estimation of the true concentration CoM. We also present a novel strategy for automatically localizing the CoM of the training dataset as an integral component of the data inversion step. We use a 2D synthetic transport study in heterogeneous media as a test case for demonstrating the performance of POD-based inversion for different error scenarios. To assess the retrieval error associated with inaccurate basis CoM, the CoM for the basis was varied by shifting it as a percentage (10, 25, 75, and 100 %) of the width (i.e., second spatial moment) of the true plume in the horizontal, diagonal, and vertical directions
Re-Inversion of Surface Electrical Resistivity Tomography Data from the Hanford Site B-Complex
Johnson, Timothy C.; Wellman, Dawn M.
2013-05-01
This report documents the three-dimensional (3D) inversion results of surface electrical resistivity tomography (ERT) data collected over the Hanford Site B-Complex. The data were collected in order to image the subsurface distribution of electrically conductive vadose zone contamination resulting from both planned releases of contamination into subsurface infiltration galleries (cribs, trenches, and tile fields), as well as unplanned releases from the B, BX, and BY tank farms and/or associated facilities. Electrically conductive contaminants are those which increase the ionic strength of pore fluids compared to native conditions, which comprise most types of solutes released into the subsurface B-Complex. The ERT data were collected and originally inverted as described in detail in report RPP-34690 Rev 0., 2007, which readers should refer to for a detailed description of data collection and waste disposal history. Although the ERT imaging results presented in that report successfully delineated the footprint of vadose zone contamination in areas outside of the tank farms, imaging resolution was not optimized due to the inability of available inversion codes to optimally process the massive ERT data set collected at the site. Recognizing these limitations and the potential for enhanced ERT characterization and time-lapse imaging at contaminated sites, a joint effort was initiated in 2007 by the U.S. Department of Energy – Office of Science (DOE-SC), with later support by the Office of Environmental Management (DOE-EM), and the U.S. Department of Defense (DOD), to develop a high-performance distributed memory parallel 3D ERT inversion code capable of optimally processing large ERT data sets. The culmination of this effort was the development of E4D (Johnson et al., 2010,2012) In 2012, under the Deep Vadose Zone Applied Field Research Initiative (DVZ-AFRI), the U.S. Department of Energy – Richland Operations Office (DOE-RL) and CH2M Hill Plateau Remediation
NASA Astrophysics Data System (ADS)
Usui, Yoshiya; Ogawa, Yasuo; Aizawa, Koki; Kanda, Wataru; Hashimoto, Takeshi; Koyama, Takao; Yamaya, Yusuke; Kagiyama, Tsuneomi
2017-03-01
Asama Volcano is an andesitic composite volcano and one of the most active volcanoes in Japan. In order to reveal electrical resistivity structure beneath the volcano accurately, we performed a 3-D inversion of dense magnetotelluric survey data. In order to prevent misinterpretation of the subsurface resistivity due to the steep topography around Asama Volcano, we used an unstructured tetrahedral mesh to represent the topography. Furthermore, we reduced the calculation time by transforming the inverse problem from the model space into the data space. Comparison of the new data-space method to the original model-space method showed that the calculation time required to update the model parameters was reduced as a result of the transformation, whereas the resistivity structure obtained remained unchanged. In the subsurface resistivity structure around Asama Volcano that was estimated from the inversion, resistive bodies were discovered to be located under the old eruption centres. In particular, under the 24 ka collapse caldera to the west of the presently active crater, a spherical resistive body was found to exist in isolation. In addition, there was a widespread conductive layer below the resistive surface layer. By comparison with previous hydrological and geochemical studies, the conductive layer was interpreted as being a high-water-content layer and an overlying layer rich in altered clay minerals. Because the western part of the volcanic conduit was considered to be the resistive area, which is inferred to consist of unfractured rocks with lower permeability than their surroundings, it would appear that the area obstructs the westward flow of the hydrothermal fluid beneath the summit, thereby contributing to higher concentrations of SO42- and Cl- in the spring water at the northern and eastern feet as well as the uneven location of a diffuse CO2 anomaly.
NASA Astrophysics Data System (ADS)
Hermans, Thomas; Nguyen, Frédéric
2015-04-01
Electrical resistivity tomography (ERT) has become a popular imaging methodology in a broad range of applications given its large sensitivity to subsurface parameters and its relative simplicity to implement. More particularly, time-lapse ERT is now increasingly used for monitoring purposes in many contexts such as water content, permafrost, landslide, seawater intrusion, solute transport or heat transport experiments. Specific inversion schemes have been developed for time-lapse data sets. However, in contrast with static inversions for which many techniques including geostatistical, minimum support or structural inversion are commonly applied, most of the methodologies for time-lapse inversion still rely on non-physically based spatial and/or temporal smoothing of the parameters or parameter changes. In this work, we propose a time-lapse ERT inversion scheme based on the difference inversion scheme. We replace the standard smoothness-constraint regularization operator by the parameter change covariance matrix. The objective function can be expressed as ψdiff(Δm ) = ||Wd [d - d0 + f(m0)- f(m )]||2 + λ ||||C-Δ0m.5Δm ||||2 where Wd is the data weighting matrix, d and d0 are the data sets corresponding to the considered time-step and to the background, f() is the forward operator, m and m0 are the models corresponding to the considered time-step and to the background, Δm is the parameter change (resistivity), CΔm is the parameter change covariance matrix and λ the regularization parameter. This operator takes into account the correlation between changes in resistivity at different locations through a variogram computed using independent data (e.g., electromagnetic logs). It may vary for subsequent time-steps if the correlation length is time-dependent. The methodology is first validated and compared to the standard smoothness-constraint inversion using a synthetic benchmark simulating the injection of a conductive tracer into a homogeneous aquifer inducing
De Donno, Giorgio; Cardarelli, Ettore
2017-01-01
In this paper, we present a new code for the modelling and inversion of resistivity and chargeability data using a priori information to improve the accuracy of the reconstructed model for landfill. When a priori information is available in the study area, we can insert them by means of inequality constraints on the whole model or on a single layer or assigning weighting factors for enhancing anomalies elongated in the horizontal or vertical directions. However, when we have to face a multilayered scenario with numerous resistive to conductive transitions (the case of controlled landfills), the effective thickness of the layers can be biased. The presented code includes a model-tuning scheme, which is applied after the inversion of field data, where the inversion of the synthetic data is performed based on an initial guess, and the absolute difference between the field and synthetic inverted models is minimized. The reliability of the proposed approach has been supported in two real-world examples; we were able to identify an unauthorized landfill and to reconstruct the geometrical and physical layout of an old waste dump. The combined analysis of the resistivity and chargeability (normalised) models help us to remove ambiguity due to the presence of the waste mass. Nevertheless, the presence of certain layers can remain hidden without using a priori information, as demonstrated by a comparison of the constrained inversion with a standard inversion. The robustness of the above-cited method (using a priori information in combination with model tuning) has been validated with the cross-section from the construction plans, where the reconstructed model is in agreement with the original design.
Timothy C. Johnson; Roeof J. Versteeg; Andy Ward; Frederick D. Day-Lewis; Andre Revil
2010-09-01
Electrical geophysical methods have found wide use in the growing discipline of hydrogeophysics, both for characterizing the electrical properties of the subsurface, and for monitoring subsurface processes in terms of the spatiotemporal changes in subsurface conductivity, chargeability, and source currents they govern. Current multichannel and multielectrode data collections systems are able to collect large amounts of data in relatively short periods of time. However, practitioners are often unable to fully utilize these large data sets and the information they contain due to the processing limitations of standard desktop computers. This limitation can be addressed by utilizing the storage and processing capabilities of high-performance parallel computing environments. We present a parallel distributed-memory forward and inverse modeling algorithm for analyzing resistivity and time-domain induced polarization data. The primary components of the parallel computations include distributed computation of the pole solutions in forward mode, distributed storage and computation of the Jacobian matrix in inverse mode, and parallel execution of the inverse equation solver. We demonstrate the corresponding parallel code for three efforts: (1) resistivity characterization of the Hanford 300 Area Integrated Field Research Challenge site in Hanford, WA; (2) resistivity characterization of a volcanic island in the southern Tyrrhenian Sea in Italy; and (3) resistivity and IP monitoring of biostimulation at a superfund site in Brandywine, MD. Inverse analysis of each of these data sets would be limited (or impossible) in a standard serial computing environment which underscores the need for high-performance computing to fully utilize the potential of electrical geophysical methods in hydrogeophysical applications.
NASA Astrophysics Data System (ADS)
Fernández-López, Sheila; Carrera, Jesús; Ledo, Juanjo; Queralt, Pilar; Luquot, Linda; Martínez, Laura; Bellmunt, Fabián
2016-04-01
Seawater intrusion in aquifers is a complex phenomenon that can be characterized with the help of electric resistivity tomography (ERT) because of the low resistivity of seawater, which underlies the freshwater floating on top. The problem is complex because of the need for joint inversion of electrical and hydraulic (density dependent flow) data. Here we present an adjoint-state algorithm to treat electrical data. This method is a common technique to obtain derivatives of an objective function, depending on potentials with respect to model parameters. The main advantages of it are its simplicity in stationary problems and the reduction of computational cost respect others methodologies. The relationship between the concentration of chlorides and the resistivity values of the field is well known. Also, these resistivities are related to the values of potentials measured using ERT. Taking this into account, it will be possible to define the different resistivities zones from the field data of potential distribution using the basis of inverse problem. In this case, the studied zone is situated in Argentona (Baix Maresme, Catalonia), where the values of chlorides obtained in some wells of the zone are too high. The adjoint-state method will be used to invert the measured data using a new finite element code in C ++ language developed in an open-source framework called Kratos. Finally, the information obtained numerically with our code will be checked with the information obtained with other codes.
NASA Astrophysics Data System (ADS)
Liu, Y.; Li, T.; Zhu, C.; Zhang, R.; Wu, Y.
2015-12-01
Three-dimensional (3-D) electromagnetic (EM) forward modelling and inversion continues to be an important issue for the correct interpretation of EM data.To this end,approximate solutions have been developed that allow the construction of relatively fast forward modelling and inversion schemes.We have developed an improved quasi-linear approximation which is more appropriate in solving the linear equation for greatly shortening calculation time.We achieved this by using green's function properties.Then we introduced the improved quasi-linear approximation to spectral induced polarization (SIP) to tackle the problem of the resolution and the efficiency.The localized quasi-linear (LQL) approximation theory is appropriate for multisource array-type surveys assuming that the normal field is slowly varying within the inhomogeneity domain.However,the normal field of attenuates severely which dose not satisfy the assumption of the LQL approximation.As a consenquence,the imaginary part is not accurate when LQL approximation is adopted for the simulation.The improved quasi-linear approximation provide a new approach with the same resolution of QL approximation and much less calculation time.We have also constructed three-dimensional SIP forward modeling based on improved quasi-linear approximation method.It only takes 0.8s for forward modeling when inhomogeneity domain is divided into 2000 blocks.Beyond that, we have introduced the Cole-Cole model to the algorithm and complete the three-dimensional complex resistivity conjugate gradient inversion with parameter restraint.The model trial results show that this method can obtain good inversion results in physical parameters such as zero frequency resistivity, polarization.The results demonstrate the stability and the efficiency of the improved quasi-linear approximation and the method may be a practical solution for3-D EM forward modelling and inversion of SIP.
NASA Astrophysics Data System (ADS)
Liu, Renqiang; Duan, Yonggang; Tan, Fengqi; Wang, Guochang; Qin, Jianhua; Neupane, Bhupati
2015-10-01
An accurate inversion of original reservoir resistivity is an important problem for waterflood development in oilfields in the middle-late development period. This paper describes the theoretical model of original resistivity recovery for a conglomerate reservoir established by petrophysical models, based on the stratigraphic model of reservoir vertical invasion of the conglomerate reservoir of an oilfield. Likewise two influencing factors of the resistivity change with a water-flooded reservoir were analyzed. The first one is the clay volume decrease due to an injected water wash argillaceous particle and the reservoir resistivity changes are influenced by it, and the other is to inject water to displace crude oil in the pore space leading to the increase of the water-bearing volume. Moreover the conductive ions of the injected water and the original formation water exchange and balance because of their salinity difference, and the reservoir resistivity changes are also influenced by them. Through the analysis of the above influential factors based on the fine identification of conglomerate lithologies the inversion models of three variables, including changes in the amount of clay, the resistivity of the irreducible water and the increase of the water bearing volume, were established by core analysis data, production performance and well logging curves information, and accurately recovered the original reservoir resistivity of the conglomerate. The original oil saturation of the reservoir was calculated according to multiple linear regression models. Finally, the produced index is defined as the difference of the original oil saturation and current oil saturation to the original oil saturation ratio, and it eliminates the effects of conglomerate lithologies and heterogeneity for the quantitative evaluation of flooded layers by the use of the principle of relative value. Compared with traditional flooding sensitive parameters which are oil saturation and water
Takamuku, Shinya; Gomi, Hiroaki
2015-07-22
How our central nervous system (CNS) learns and exploits relationships between force and motion is a fundamental issue in computational neuroscience. While several lines of evidence have suggested that the CNS predicts motion states and signals from motor commands for control and perception (forward dynamics), it remains controversial whether it also performs the 'inverse' computation, i.e. the estimation of force from motion (inverse dynamics). Here, we show that the resistive sensation we experience while moving a delayed cursor, perceived purely from the change in visual motion, provides evidence of the inverse computation. To clearly specify the computational process underlying the sensation, we systematically varied the visual feedback and examined its effect on the strength of the sensation. In contrast to the prevailing theory that sensory prediction errors modulate our perception, the sensation did not correlate with errors in cursor motion due to the delay. Instead, it correlated with the amount of exposure to the forward acceleration of the cursor. This indicates that the delayed cursor is interpreted as a mechanical load, and the sensation represents its visually implied reaction force. Namely, the CNS automatically computes inverse dynamics, using visually detected motions, to monitor the dynamic forces involved in our actions.
Chen, Yingying; Stabryla, Lisa; Wei, Na
2016-01-29
Development of acetic acid-resistant Saccharomyces cerevisiae is important for economically viable production of biofuels from lignocellulosic biomass, but the goal remains a critical challenge due to limited information on effective genetic perturbation targets for improving acetic acid resistance in the yeast. This study employed a genomic-library-based inverse metabolic engineering approach to successfully identify a novel gene target, WHI2 (encoding a cytoplasmatic globular scaffold protein), which elicited improved acetic acid resistance in S. cerevisiae. Overexpression of WHI2 significantly improved glucose and/or xylose fermentation under acetic acid stress in engineered yeast. The WHI2-overexpressing strain had 5-times-higher specific ethanol productivity than the control in glucose fermentation with acetic acid. Analysis of the expression of WHI2 gene products (including protein and transcript) determined that acetic acid induced endogenous expression of Whi2 in S. cerevisiae. Meanwhile, the whi2Δ mutant strain had substantially higher susceptibility to acetic acid than the wild type, suggesting the important role of Whi2 in the acetic acid response in S. cerevisiae. Additionally, overexpression of WHI2 and of a cognate phosphatase gene, PSR1, had a synergistic effect in improving acetic acid resistance, suggesting that Whi2 might function in combination with Psr1 to elicit the acetic acid resistance mechanism. These results improve our understanding of the yeast response to acetic acid stress and provide a new strategy to breed acetic acid-resistant yeast strains for renewable biofuel production.
Chen, Yingying; Stabryla, Lisa
2016-01-01
Development of acetic acid-resistant Saccharomyces cerevisiae is important for economically viable production of biofuels from lignocellulosic biomass, but the goal remains a critical challenge due to limited information on effective genetic perturbation targets for improving acetic acid resistance in the yeast. This study employed a genomic-library-based inverse metabolic engineering approach to successfully identify a novel gene target, WHI2 (encoding a cytoplasmatic globular scaffold protein), which elicited improved acetic acid resistance in S. cerevisiae. Overexpression of WHI2 significantly improved glucose and/or xylose fermentation under acetic acid stress in engineered yeast. The WHI2-overexpressing strain had 5-times-higher specific ethanol productivity than the control in glucose fermentation with acetic acid. Analysis of the expression of WHI2 gene products (including protein and transcript) determined that acetic acid induced endogenous expression of Whi2 in S. cerevisiae. Meanwhile, the whi2Δ mutant strain had substantially higher susceptibility to acetic acid than the wild type, suggesting the important role of Whi2 in the acetic acid response in S. cerevisiae. Additionally, overexpression of WHI2 and of a cognate phosphatase gene, PSR1, had a synergistic effect in improving acetic acid resistance, suggesting that Whi2 might function in combination with Psr1 to elicit the acetic acid resistance mechanism. These results improve our understanding of the yeast response to acetic acid stress and provide a new strategy to breed acetic acid-resistant yeast strains for renewable biofuel production. PMID:26826231
NASA Astrophysics Data System (ADS)
Singh, U. K.; Tiwari, R. K.; Singh, S. B.
2005-02-01
This paper deals with the application of artificial neural networks (ANN) technique for the study of a case history using 1-D inversion of vertical electrical resistivity sounding (VES) data from the Puga valley, Kashmir, India. The study area is important for its rich geothermal resources as well as from the tectonic point of view as it is located near the collision boundary of the Indo-Asian crustal plates. In order to understand the resistivity structure and layer thicknesses, we used here three-layer feedforward neural networks to model and predict measured VES data. Three algorithms, e.g. back-propagation (BP), adaptive back-propagation (ABP) and Levenberg-Marquardt algorithm (LMA) were applied to the synthetic as well as real VES field data and efficiency of supervised training network are compared. Analyses suggest that LMA is computationally faster and give results, which are comparatively more accurate and consistent than BP and ABP. The results obtained using the ANN inversions are remarkably correlated with the available borehole litho-logs. The feasibility study suggests that ANN methods offer an excellent complementary tool for the direct detection of layered resistivity structure.
NASA Astrophysics Data System (ADS)
Favetto, Alicia; Pomposiello, Cristina; López de Luchi, Mónica G.; Booker, John
2008-11-01
Magnetotelluric data were obtained along a 450 km, almost west-east profile at approximately 31.5° S, which extends from La Rioja to Santa Fé provinces in central Argentina. The profile crosses two main crustal domains that were juxtaposed during the Early-Middle Cambrian Pampean Orogeny: the Pampean terrane to the west and the Río de la Plata craton to the east. The electrical resistivity structure of the crustal domains together with their boundary is presented. Through dimensionality analysis of the data, it was demonstrated that regional-scale electrical structures are mainly two-dimensional with a strike direction oriented parallel to the surface geological strike. The resistivity model shows a subvertical limit approximately along the eastern border of the Sierra Chica de Córdoba. To the east, the shallower structure is the Chaco-Paranense basin extending to a depth of 6 km with resistivities between 1 and 30 Ohm-m, whereas below the basin the ca 2.1-2.3 Ga Río de la Plata craton shows resistivities in a range of 300-10,000 Ohm-m. The Pampean terrane presents a 6 km layer with a resistivity higher than 10,000 Ohm-m whereas below this layer the resistivity values range from 50 to 200 Ohm-m. Based on both the geological information and the magnetotelluric results, the sharp lateral discontinuity observed in the resistivity model to the east of the Sierras de Córdoba is conjectured to represent the boundary between the Río de la Plata craton and the Pampean terrane which may correspond to the Early Cambrian suture.
NASA Astrophysics Data System (ADS)
Abderrezak, Bouchedda; Bernard, Giroux; Michel, Allard
2017-02-01
The magnetometric resistivity (MMR) method consists of measuring the variation of magnetostatic field associated to current density variations. It is based on the principle that direct current flow between two electrodes takes the path of least resistance through the earth. Consequently, conductive or relatively conductive ore bodies such as massive, semi-massive to disseminated sulphides are preferentially energized, which increases the current density in their vicinity. MMR is more efficient than electromagnetic methods in the case of weak conductivity contrasts. To improve the signal to noise ratio the magnetic field can be measured in boreholes rather than on the surface. Down-hole magnetometric resistivity measurements have been conducted in Tobermalug prospect in County Limerick, Ireland. The survey was used as an alternative to down-hole electromagnetic to delineate subhorizontal zinc/lead mineralization lenses that can be poorly conductive. Two survey areas were investigated, DHMMR1 and DHMMR2. Interpretation is based on the regularized least-squares inversion of MMR data, in which the MMR forward problem is solved with a finite volume discretization of the electrostatic and magnetostatic equations. Inversion of synthetic data generated over two conductive horizontal discs model shows that conductive structures are well positioned but their extensions is biased along current electrodes orientation. Inversion of the field data allowed localizing a few conductive elongated targets. At DHMMR1, the conductivity is weaker and seems to be associated to disseminated mineralization. DHMMR2 contains a higher conductivity and more elongated target. It appears to be associated to semi-massive sulphides.
NASA Astrophysics Data System (ADS)
Lotsch, Bettina V.
2015-07-01
Graphene's legacy has become an integral part of today's condensed matter science and has equipped a whole generation of scientists with an armory of concepts and techniques that open up new perspectives for the postgraphene area. In particular, the judicious combination of 2D building blocks into vertical heterostructures has recently been identified as a promising route to rationally engineer complex multilayer systems and artificial solids with intriguing properties. The present review highlights recent developments in the rapidly emerging field of 2D nanoarchitectonics from a materials chemistry perspective, with a focus on the types of heterostructures available, their assembly strategies, and their emerging properties. This overview is intended to bridge the gap between two major—yet largely disjunct—developments in 2D heterostructures, which are firmly rooted in solid-state chemistry or physics. Although the underlying types of heterostructures differ with respect to their dimensions, layer alignment, and interfacial quality, there is common ground, and future synergies between the various assembly strategies are to be expected.
Takamuku, Shinya; Gomi, Hiroaki
2015-01-01
How our central nervous system (CNS) learns and exploits relationships between force and motion is a fundamental issue in computational neuroscience. While several lines of evidence have suggested that the CNS predicts motion states and signals from motor commands for control and perception (forward dynamics), it remains controversial whether it also performs the ‘inverse’ computation, i.e. the estimation of force from motion (inverse dynamics). Here, we show that the resistive sensation we experience while moving a delayed cursor, perceived purely from the change in visual motion, provides evidence of the inverse computation. To clearly specify the computational process underlying the sensation, we systematically varied the visual feedback and examined its effect on the strength of the sensation. In contrast to the prevailing theory that sensory prediction errors modulate our perception, the sensation did not correlate with errors in cursor motion due to the delay. Instead, it correlated with the amount of exposure to the forward acceleration of the cursor. This indicates that the delayed cursor is interpreted as a mechanical load, and the sensation represents its visually implied reaction force. Namely, the CNS automatically computes inverse dynamics, using visually detected motions, to monitor the dynamic forces involved in our actions. PMID:26156766
Akhter, Gulraiz; Farid, Asim; Ahmad, Zulfiqar
2012-01-01
Velocity and density measured in a well are crucial for synthetic seismic generation which is, in turn, a key to interpreting real seismic amplitude in terms of lithology, porosity and fluid content. Investigations made in the water wells usually consist of spontaneous potential, resistivity long and short normal, point resistivity and gamma ray logs. The sonic logs are not available because these are usually run in the wells drilled for hydrocarbons. To generate the synthetic seismograms, sonic and density logs are required, which are useful to precisely mark the lithology contacts and formation tops. An attempt has been made to interpret the subsurface soil of the aquifer system by means of resistivity to seismic inversion. For this purpose, resistivity logs and surface resistivity sounding were used and the resistivity logs were converted to sonic logs whereas surface resistivity sounding data transformed into seismic curves. The converted sonic logs and the surface seismic curves were then used to generate synthetic seismograms. With the utilization of these synthetic seismograms, pseudo-seismic sections have been developed. Subsurface lithologies encountered in wells exhibit different velocities and densities. The reflection patterns were marked by using amplitude standout, character and coherence. These pseudo-seismic sections were later tied to well synthetics and lithologs. In this way, a lithology section was created for the alluvial fill. The cross-section suggested that the eastern portion of the studied area mainly consisted of sandy fill and the western portion constituted clayey part. This can be attributed to the depositional environment by the Indus and the Kabul Rivers.
Four-dimensional inversion of resistivity monitoring data through Lp norm minimizations
NASA Astrophysics Data System (ADS)
Kim, Jung-Ho; Supper, Robert; Tsourlos, Panagiotis; Yi, Myeong-Jong
2013-12-01
A new 4-D inversion algorithm is developed so that any data misfits and model roughness in the space and time domains can be selectively minimized, in terms of either the L1 norm or the L2 norm. This study is motivated by the experience that a 4-D inversion adopting full L2 norm minimization may sometimes result in a model that is too smoothly varying with time. It is further encouraged by the realization that a particular criterion of either L1 or L2 norm cannot be universally optimal for accurately reconstructing the subsurface condition. In addition, we try to overcome difficulties of jointly choosing two optimal regularization parameters in space and time domains. To achieve this, we devise automatic determination methods, not only of the Lagrangian multipliers for the space-domain smoothness constraint, but also of the regularization parameter for penalizing the model roughness along the time axis. Both kinds of regularization parameters are actively updated at each iteration, according to variations in data misfit and model roughness. We conducted inversion experiments using synthetic and field monitoring data to test the proposed algorithms, and further to compare the performance of L1 and L2 norm minimizations. Both the synthetic and field data experiments demonstrated that the proposed automatic determination method produced ground changes that were more similar to the true changes than those of approaches using pre-determined parameter values. Inversion experiments showed that L1 norm minimization of the time-domain roughness could reduce the problem of overly smooth model changes when the subsurface changes are locally confined, but that the L2 norm approach would be more reasonable when the changes are expected to be widespread.
NASA Astrophysics Data System (ADS)
Günther, T.; Müller-Petke, M.
2012-09-01
For reliably predicting the impact of climate changes on salt/freshwater systems below barrier islands, a long-term hydraulic modelling is inevitable. As input we need the parameters porosity, salinity and hydraulic conductivity at the catchment scale, preferably non-invasively acquired with geophysical methods. We present a methodology to retrieve the searched parameters and a lithological interpretation by the joint analysis of magnetic resonance soundings (MRS) and vertical electric soundings (VES). Both data sets are jointly inverted for resistivity, water content and decay time using a joint inversion scheme. Coupling is accomplished by common layer thicknesses. We show the results of three soundings measured on the eastern part of the North Sea island of Borkum. Pumping test data is used to calibrate the petrophysical relationship for the local conditions in order to estimate permeability from nuclear magnetic resonance (NMR) data. Salinity is retrieved from water content and resistivity using a modified Archie equation calibrated by local samples. As a result we are able to predict porosity, salinity and hydraulic conductivities of the aquifers, including their uncertainties. The joint inversion significantly improves the reliability of the results. Verification is given by comparison with a borehole. A sounding in the flooding area demonstrates that only the combined inversion provides a correct subsurface model. Thanks to the joint application, we are able to distinguish fluid conductivity from lithology and provide reliable hydraulic parameters as shown by uncertainty analysis. These findings can finally be used to build groundwater flow models for simulating climate changes. This includes the improved geometry and lithological attribution, and also the parameters and their uncertainties.
NASA Astrophysics Data System (ADS)
Diaz Montiel, Paulina
Carbon Fiber Reinforced Polymer (CFRP) materials are used in aerospace structures due to their superior mechanical properties and reduced weight. Non-destructive evaluation (NDE) techniques are needed for such materials to detect and measure intra-ply matrix cracking and inter-ply delamination damage without harming or altering their initial configuration. The aim of NDE techniques is to use the composite material as a sensor itself, and to use its intrinsic material properties as measure of damage. Previous literature has shown that CFRP composites are electrically conductive in the fibers direction, and that the fiber-to-fiber contact due to waviness provides electrical conduction in the direction normal to the fibers. When matrix cracking or delamination defects are introduced in the composite, they break the fiber contact network, and this increases the local resistivity of the material. The Electrical Resistance Tomography (ERT) provides a NDE technique that uses these inherent changes in conductive properties of the composite to map its internal damage state. As opposed to other NDE methods, this technique allows the in-situ monitoring and detection on damage, which is particularly desirable for large and complex aerospace structures. This research investigates efficient numerical modeling techniques for inverse identification of delamination damage location and size in composite laminates using ERT based NDE. Identification of damage in composites requires solving the inverse problem that minimizes the difference between the model predicted and the measured change in resistance at specified electrode locations. The direct use of numerical finite element models of the laminate in the inverse identification is computationally expensive and it requires the development of accurate surrogate models. The use of Response Surfaces and Kriging approximations for single-response surrogate modeling is investigated in this work. Since the electrical resistance changes
Ward, Stanley H.
1989-01-01
Multiple arrays of electric or magnetic transmitters and receivers are used in a borehole geophysical procedure to obtain a multiplicity of redundant data suitable for processing into a resistivity or induced polarization model of a subsurface region of the earth.
NASA Astrophysics Data System (ADS)
Meqbel, Naser M.; Egbert, Gary D.; Wannamaker, Philip E.; Kelbert, Anna; Schultz, Adam
2014-09-01
Long period (10-20,000 s) magnetotelluric (MT) data are being acquired across the continental USA on a quasi-regular grid of ˜70 km spacing as an electromagnetic component of the National Science Foundation EarthScope/USArray Program. These data are sensitive to fluids, melts, and other orogenic indicators, and thus provide a valuable complement to other components of EarthScope. We present and interpret results of 3-D MT data inversion from 325 sites acquired from 2006-2011 to provide a regional scale view of electrical resistivity from the middle crust to nearly the mantle transition zone, covering an area from NW Washington to NW Colorado. Beneath the active extensional subprovinces in the south-central region, on average we see a resistive upper crust, and then extensive areas of low resistivity in the lower crust and uppermost mantle. Further below, much of the upper half of the upper mantle appears moderately resistive, then subsequently the lower upper mantle becomes moderately conductive. This column suggests a dynamic process of moderately hydrated and fertile deeper upper mantle upwelling during extension, intersection of that material with the damp solidus causing dehydration and melting, and upward exodus of generated mafic melts to pond and exsolve saline fluids near Moho levels. Lithosphere here is very thin. To the east and northeast, thick sections of resistive lithosphere are imaged under the Wyoming and Medicine Hat Cratons. These are punctuated with numerous electrically conductive sutures presumably containing graphitic or sulfide-bearing meta-sediments deeply underthrust and emplaced during ancient collisions. Below Cascadia, the subducting Juan de Fuca and Gorda lithosphere appears highly resistive. Suspected oceanic lithosphere relicts in the central NW part of the model domain also are resistive, including the accreted “Siletzia” terrane beneath the Coast Ranges and Columbia Embayment, and the seismically fast “slab curtain” beneath
Rapid approximate inversion of airborne TEM
NASA Astrophysics Data System (ADS)
Fullagar, Peter K.; Pears, Glenn A.; Reid, James E.; Schaa, Ralf
2015-11-01
Rapid interpretation of large airborne transient electromagnetic (ATEM) datasets is highly desirable for timely decision-making in exploration. Full solution 3D inversion of entire airborne electromagnetic (AEM) surveys is often still not feasible on current day PCs. Therefore, two algorithms to perform rapid approximate 3D interpretation of AEM have been developed. The loss of rigour may be of little consequence if the objective of the AEM survey is regional reconnaissance. Data coverage is often quasi-2D rather than truly 3D in such cases, belying the need for `exact' 3D inversion. Incorporation of geological constraints reduces the non-uniqueness of 3D AEM inversion. Integrated interpretation can be achieved most readily when inversion is applied to a geological model, attributed with lithology as well as conductivity. Geological models also offer several practical advantages over pure property models during inversion. In particular, they permit adjustment of geological boundaries. In addition, optimal conductivities can be determined for homogeneous units. Both algorithms described here can operate on geological models; however, they can also perform `unconstrained' inversion if the geological context is unknown. VPem1D performs 1D inversion at each ATEM data location above a 3D model. Interpretation of cover thickness is a natural application; this is illustrated via application to Spectrem data from central Australia. VPem3D performs 3D inversion on time-integrated (resistive limit) data. Conversion to resistive limits delivers a massive increase in speed since the TEM inverse problem reduces to a quasi-magnetic problem. The time evolution of the decay is lost during the conversion, but the information can be largely recovered by constructing a starting model from conductivity depth images (CDIs) or 1D inversions combined with geological constraints if available. The efficacy of the approach is demonstrated on Spectrem data from Brazil. Both separately and in
Ward, S.H.
1989-10-17
Multiple arrays of electric or magnetic transmitters and receivers are used in a borehole geophysical procedure to obtain a multiplicity of redundant data suitable for processing into a resistivity or induced polarization model of a subsurface region of the earth. 30 figs.
2016-07-06
detection of genetic variants known to confer ciprofloxacin resistance in Bacillus anthracis, Yersinia pestis, and Francisella tularensis. Sequencing...results demonstrate MIPs capture and amplify targeted regions of interest at significant levels of coverage. Depending on the genetic variant...multiple downstream molecular assays for the detection of targeted genetic regions. TR-16-130 DISTRIBUTION STATEMENT A: Approved for public release
NASA Astrophysics Data System (ADS)
Günther, T.; Müller-Petke, M.
2012-03-01
In order to do hydraulic modelling for simulating the salt-/fresh water dynamics, the parameters porosity, salinity and hydraulic conductivity are needed. We present a methodology retrieve them by the joint analysis of magnetic resonance (MRS) and and vertical electric (VES) soundings. Both data sets are jointly inverted for resistivity, water content and decay time using a block discretization. We show the results of three soundings measured in the east part of the CLIWAT pilot area Borkum. Pumping test data is used to calibrate the petrophysical relationship for the local conditions. As a result we are able to predict porosity, salinity and hydraulic conductivities of the aquifers including their uncertainty. The joint inversion significantly improves the reliability of the results, which can be shown by comparison with a borehole. By a sounding in the flooding area we demonstrate that only the combined inversion leads to a correct subsurface model. Thanks to the joint application we are able to distinguish fluid conductivity from lithology and provide reliable hydraulic parameters.
NASA Astrophysics Data System (ADS)
Alvarado-Leaños, J. J.; Ordonez-Miranda, J.; Alvarado-Gil, J. J.
2013-09-01
In this work, considering that all the thermal properties of a sample depend on the position, it is shown that the Fourier heat transport equation can be written in terms of just the square of the thermal effusivity, by introducing the thermal resistance as a new variable. The conditions, in which analytical solutions of this equation can be obtained, are discussed. Based on these results, an inversion method is proposed to retrieve the profile of the thermal property profiles, if the surface temperature is provided. The method requires the assumption of a local thermal-effusivity profile, such that the temperature profile can be analytically obtained, to generate a global thermal-effusivity profile, which is independent of the initial assumed profile. Applying this method to a pair of simple but representative cases of one-dimensional layered systems, the accuracy and stability of the method is verified. In particular, the noise sensitivity is investigated by carrying out the inversion procedure with white Gaussian noise added to the simulated experimental data. The proposed approach could be useful for the development of methodologies to interpret experimental data and to retrieve the in-depth variations of thermal properties of materials.
Effects of anisotropy on the two-dimensional inversion procedure
NASA Astrophysics Data System (ADS)
Heise, Wiebke; Pous, Jaume
2001-12-01
In this paper we show some of the effects that appear in magnetotelluric measurements over 2-D anisotropic structures, and propose a procedure to recover the anisotropy using 2-D inversion algorithms for isotropic models. First, we see how anisotropy affects the usual interpretation steps: dimensionality analysis and 2-D inversion. Two models containing general 2-D azimuthal anisotropic features were chosen to illustrate this approach: an anisotropic block and an anisotropic layer, both forming part of general 2-D models. In addition, a third model with dipping anisotropy was studied. For each model we examined the influence of various anisotropy strikes and resistivity contrasts on the dimensionality analysis and on the behaviour of the induction arrows. We found that, when the anisotropy ratio is higher than five, even if the strike is frequency-dependent it is possible to decide on a direction close to the direction of anisotropy. Then, if the data are rotated to this angle, a 2-D inversion reproduces the anisotropy reasonably well by means of macro-anisotropy. This strategy was tested on field data where anisotropy had been previously recognized.
NASA Astrophysics Data System (ADS)
Meqbel, N. M.; Egbert, G. D.; Wannamaker, P. E.; Kelbert, A.; Schultz, A.
2013-12-01
Long period (10-20,000 s) magnetotelluric (MT) data are being acquired across the continental USA on a quasi-regular grid of ~70 km spacing as an electromagnetic component of the National Science Foundation EarthScope/USArray Program. These data are sensitive to fluids, melts, and other orogenic indicators, and thus provide a valuable complement to other components of EarthScope. We present and interpret results of 3-D MT data inversion from 325 sites acquired from 2006-2011 to provide a regional scale view of electrical resistivity from the middle crust to nearly the mantle transition zone, covering an area from NW Washington to NW Colorado. Extensive areas of low resistivity are imaged in the lower crust and uppermost mantle beneath the extensional provinces, most plausibly explained by underplated, hybridized magmas and associated exsolved highly saline fluids. These pervasive low resistivities show aligned or 'streaky' textures roughly parallel to seismic fast-axes, possibly reflecting widespread flow induced alignment of melt in this area. Thick sections of resistive lithosphere imaged in the eastern and northeastern part of the domain coincide spatially with the Wyoming and Medicine Hat Cratons. Sutures bounding these cratonic blocks are electrically conductive most likely due to meta-sediments emplaced during ancient collisions. Below the Cascadia forearc, the subducting Juan de Fuca and Gorda lithosphere appears highly resistive. Other resistive zones in the NW part of the domain may denote relict oceanic lithosphere: the accreted 'Siletzia' terrane beneath the Coast Ranges and Columbia Embayment, and the seismically fast 'slab curtain' beneath eastern Idaho interpreted by others as stranded Farallon lithosphere. Quasi-horizontal patches of low resistivity in the deep crust beneath the Cascade volcanic arc and fore-arc likely represent fluids evolved from breakdown of hydrous minerals in the down-going slab. In the backarc, low resistivities concentrate in
NASA Astrophysics Data System (ADS)
Truchly, M.; Plecenik, T.; Zhitlukhina, E.; Belogolovskii, M.; Dvoranova, M.; Kus, P.; Plecenik, A.
2016-11-01
We have studied a bipolar resistive switching phenomenon in c-axis oriented normal-state YBa2Cu3O7-c (YBCO) thin films at room temperature by scanning spreading resistance microscopy (SSRM) and scanning tunneling microscopy (STM) techniques. The most striking experimental finding has been the opposite (in contrast to the previous room and low-temperature data for planar metal counter-electrode-YBCO bilayers) voltage-bias polarity of the switching effect in all SSRM and a number of STM measurements. We have assumed that the hysteretic phenomena in current-voltage characteristics of YBCO-based contacts can be explained by migration of oxygen-vacancy defects and, as a result, by the formation or dissolution of more or less conductive regions near the metal-YBCO interface. To support our interpretation of the macroscopic resistive switching phenomenon, a minimalist model that describes radical modifications of the oxygen-vacancy effective charge in terms of a charge-wind effect was proposed. It was shown theoretically that due to the momentum exchange between current carriers (holes in the YBCO compound) and activated oxygen ions, the direction in which oxygen vacancies are moving is defined by the balance between the direct electrostatic force on them and that caused by the current-carrier flow.
NASA Astrophysics Data System (ADS)
Nguyen, Frédéric; Hermans, Thomas
2015-04-01
Inversion of time-lapse resistivity data allows obtaining 'snapshots' of changes occurring in monitored systems for applications such as aquifer storage, geothermal heat exchange, site remediation or tracer tests. Based on these snapshots, one can infer qualitative information on the location and morphology of changes occurring in the subsurface but also quantitative estimates on the degree of changes in certain property such as temperature or total dissolved solid content. Analysis of these changes can provide direct insight into flow and transport and associated processes and controlling parameters. However, the reliability of the analysis is dependent on survey geometry, measurement schemes, data error, and regularization. Survey design parameters may be optimized prior to the monitoring survey. Regularization, on the other hand, may be chosen depending on available information collected during the monitoring. Common approaches consider smoothing model changes both in space and time but it is often needed to obtain a sharp temporal anomaly, for example in fractured aquifers. We here propose to use the alternative regularization approach based on minimum gradient support (MGS) (Zhdanov, 2002) for time-lapse surveys which will focus the changes in tomograms snapshots. MGS will limit the occurrences of changes in electrical resistivity but will also restrict the variations of these changes inside the different zones. A commonly encountered difficulty by practitioners in this type of regularization is the choice of an additional parameter, the so-called β, required to define the MGS functional. To the best of our knowledge, there is no commonly accepted or standard methodology to optimize the MGS parameter β. The inversion algorithm used in this study is CRTomo (Kemna 2000). It uses a Gauss-Newton scheme to iteratively minimize an objective function which consists of a data misfit functional and a model constraint functional. A univariate line search is performed
Buitrago-Lopez, Adriana; van den Hooven, Edith H; Rueda-Clausen, Christian F; Serrano, Norma; Ruiz, Alvaro J; Pereira, Mark A; Mueller, Noel T
2015-01-01
Background Low socioeconomic status (SES) has been associated with higher risk of cardiometabolic diseases in developed societies, but investigation of SES and cardiometabolic risk in children in less economically developed populations is sparse. We aimed to examine associations among SES and cardiometabolic risk factors in Colombian children. Methods We used data from a population-based study of 1282 children aged 6–10 years from Bucaramanga, Colombia. SES was classified according to household wealth, living conditions and access to public utilities. Anthropometric and biochemical parameters were measured at a clinic visit. Cardiometabolic risk factors were analysed continuously using linear regression and as binary outcomes—according to established paediatric cut points—using logistic regression to calculate OR and 95% CIs. Results Mean age of the children was 8.4 (SD 1.4) and 51.1% of the sample were boys. Odds of overweight/obesity, abdominal obesity and insulin resistance were greater among higher SES. Compared with the lowest SES stratum, children in the highest SES had higher odds of overweight/obesity (OR=3.25, 95% CI 1.89 to 5.57), abdominal obesity (OR=2.74, 95% CI 1.41 to 5.31) and insulin resistance (OR=2.60, 95% CI 1.81 to 3.71). In contrast, children in the highest SES had lower odds of hypertriglyceridaemia (triglycerides ≥90th centile; OR=0.28, 95% CI 0.14 to 0.54) and low (≤10th centile) high-density lipoprotein (HDL) cholesterol (OR=0.35, 95% CI 0.15 to 0.78). Conclusions In Colombian children, SES is directly associated with obesity and insulin resistance, but inversely associated with dyslipidaemia (hypertriglyceridaemia and low HDL cholesterol). Our findings highlight the need to analyse cardiometabolic risk factors separately in children and to carefully consider a population's level of economic development when studying their social determinants of cardiometabolic disease. PMID:25691273
NASA Astrophysics Data System (ADS)
Silva, Pablo G.
2010-05-01
The ancient roman city of Baelo Claudia has been subject of several papers on earthquake environmental effects (EEE) and well as earthquake archaeological effects (EAE). During the field training course on archaeoseismology and palaeoseismology conducted in September 2009 (INQUA-IGCP567 Workshop) held at Baelo Claudia, four Electric Resistivity Tomography (ERT) profiles were carried out, by the teams of the Salamanca University (Spain), RWTH Aachen University (Germany) and the Geological Survey of Spain (IGME). ERT surveys were developed in the eastern side of the ancient roman Forum across the unexcavated sector of the archaeological site heading on the 1st Century AD Isis Temple. Each ERT profile was constituted by a 48 multielectrode array with spacing of 2 m resulting in a total length of investigation of around 384 m. ERT lines were separated 10 m each other resulting in a total research area of 3840 m2 to a mean investigation depth of 16 m. The selected survey configurations were Pole-Dipole and Wenner in order to get detailed information about lateral resistivity contrasts, but with a reasonable depth of investigation. The resulting 2D resistivity pseudosections clearly display deformations of the buried roman pavements which propagated in depth within the pre-roman clayey substratum of the Bolonia Bay area.. 3D modelling of the 2D pseudosections indicates that the observed deformations are related to near-surface landsliding, being possible to calculate the minimum volume of mobilized material. ERT 3D imaging allow to refine previous GPR surveys conducted at this same area and to get a subsurface picture of ground deformations caused by repeated earthquakes during the 1st and 3rd Centuries AD. Preliminary calculated volume for the mobilized materials affecting the foundations of the Isis Temple and Forum clearly points to a minimum ESI-07 VIII Intensity validating previous research in the zone. This study has been supported by the Spanish Research Projects
Rodriguez, Brian D.
2017-03-31
This report summarizes the results of three-dimensional (3-D) resistivity inversion simulations that were performed to account for local 3-D distortion of the electric field in the presence of 3-D regional structure, without any a priori information on the actual 3-D distribution of the known subsurface geology. The methodology used a 3-D geologic model to create a 3-D resistivity forward (“known”) model that depicted the subsurface resistivity structure expected for the input geologic configuration. The calculated magnetotelluric response of the modeled resistivity structure was assumed to represent observed magnetotelluric data and was subsequently used as input into a 3-D resistivity inverse model that used an iterative 3-D algorithm to estimate 3-D distortions without any a priori geologic information. A publicly available inversion code, WSINV3DMT, was used for all of the simulated inversions, initially using the default parameters, and subsequently using adjusted inversion parameters. A semiautomatic approach of accounting for the static shift using various selections of the highest frequencies and initial models was also tested. The resulting 3-D resistivity inversion simulation was compared to the “known” model and the results evaluated. The inversion approach that produced the lowest misfit to the various local 3-D distortions was an inversion that employed an initial model volume resistivity that was nearest to the maximum resistivities in the near-surface layer.
Orsatti, Fábio L; Nahas, Eliana A P; Orsatti, Cláudio L; de Oliveira, Erick P; Nahas-Neto, Jorge; da Mota, Gustavo R; Burini, Roberto C
2012-08-01
The aim of this study was to evaluate alterations in trunk adiposity (TA) over 9 months of resistance training (RT) and associate these changes with the hypertrophy of muscle mass (MM) in postmenopausal women (PW). The investigation used a sample that consisted of 22 PW (44-69 years old). The group was subjected to RT (60-80% of 1 repetition maximum) for the total body 3 d · wk(-1). Body composition (dual-energy x-ray absorptiometry) and plasma levels of insulin-like growth factor-1 (IGF-1), follicle-stimulating hormone, E2 (Immulite system), and interleukin-6 (IL-6; enzyme-linked immunosorbent assay) were assessed at the beginning and end of the experiment. After RT, only women who acquired up to 5% TA gained MM, whereas women who acquired >5% TA exhibited increased IL-6 and no MM gain (p < 0.05). The ΔMM was negatively associated with time of menopause (r = -0.45, p < 0.05) and positively associated with baseline IGF-1 (r = 0.47, p < 0.05). Only ΔLE (leg extension) was negatively associated with baseline IL-6 (p < 0.05). Trunk adiposity growth (ΔTF, kilograms) was positively correlated with changes in IL-6 (r = 0.68, p < 0.05). The MM gain was negatively correlated with ΔTF (r = -0.63, p < 0.05) and changes in IL-6 (r = -0.73, p < 0.05). After adjusting all of the confounding variables, only baseline IGF-1 (positively) and changes in IL-6 (negatively) influenced MM, and only the increase in TA influenced IL-6. Our study suggests that increased levels of TA during RT increase IL-6 concentrations, which is a significant negative predictor of MM gain in PW.
Commer, Michael; Helwig, Stefan, L.; Hordt, Andreas; Scholl,Carsten; Tezkan, Bulent
2006-06-14
Three long-offset transient electromagnetic (LOTEM) surveyswerecarried out at the active volcano Merapi in Central Java (Indonesia)during the years 1998, 2000, and 2001. The measurements focused on thegeneral resistivity structure of the volcanic edifice at depths of 0.5-2km and the further investigation of a southside anomaly. The measurementswere insufficient for a full 3D inversion scheme, which could enable theimaging of finely discretized resistivity distributions. Therefore, astable, damped least-squares joint-inversion approach is used to optimize3D models with a limited number of parameters. The mode ls feature therealistic simulation of topography, a layered background structure, andadditional coarse 3D blocks representing conductivity anomalies.Twenty-eight LOTEM transients, comprising both horizontal and verticalcomponents of the magnetic induction time derivative, were analyzed. Inview of the few unknowns, we were able to achieve reasonable data fits.The inversion results indicate an upwelling conductor below the summit,suggesting hydrothermal activity in the central volcanic complex. Ashallow conductor due to a magma-filled chamber, at depths down to 1 kmbelow the summit, suggested by earlier seismic studies, is not indicatedby the inversion results. In conjunction with an anomalous-density model,derived from arecent gravity study, our inversion results provideinformation about the southern geological structure resulting from amajor sector collapse during the Middle Merapi period. The density modelallows to assess a porosity range andthus an estimated vertical salinityprofile to explain the high conductivities on a larger scale, extendingbeyond the foothills of Merapi.
E-2D Advanced Hawkeye Aircraft (E-2D AHE)
2015-12-01
Selected Acquisition Report (SAR) RCS: DD-A&T(Q&A)823-364 E-2D Advanced Hawkeye Aircraft (E-2D AHE) As of FY 2017 President’s Budget Defense...Office Estimate RDT&E - Research, Development, Test, and Evaluation SAR - Selected Acquisition Report SCP - Service Cost Position TBD - To Be Determined
Liese, Angela D; Nichols, Michele; Sun, Xuezheng; D'Agostino, Ralph B; Haffner, Steven M
2009-08-01
OBJECTIVE The Dietary Approaches to Stop Hypertension (DASH) diet has been widely promoted; however, little is known about its impact on type 2 diabetes. RESEARCH DESIGN AND METHODS We evaluated the association of the DASH diet with incidence of type 2 diabetes among 862 participants of the Insulin Resistance Atherosclerosis Study (IRAS) who completed a 1-year food frequency questionnaire at baseline. Type 2 diabetes odds ratios (ORs) were estimated at tertiles of the DASH score. RESULTS An inverse association was observed in whites (tertile 2 vs. tertile 1, OR 0.66 [95% CI 0.29-1.48]) that became significant for the most extreme contrast (tertile 3 vs. tertile 1, 0.31 [0.13-0.75]), with adjustment for covariates. No association was observed in blacks or Hispanics (tertile 2 vs. tertile 1, 1.16 [0.61-2.18 ]; tertile 3 vs. tertile 1, 1.34 [0.70-2.58 ]). CONCLUSIONS Adherence to the DASH dietary pattern, which is rich in vegetables, fruit, and low-fat dairy products, may have the potential to prevent type 2 diabetes.
NASA Astrophysics Data System (ADS)
Kalscheuer, Thomas; Pedersen, Laust B.; Siripunvaraporn, Weerachai
2008-11-01
Electromagnetic surface measurements with the radiomagnetotelluric (RMT) method in the frequency range between 10 and 300kHz are typically interpreted in the quasi-static approximation, that is, assuming displacement currents are negligible. In this paper, the dielectric effect of displacement currents on RMT responses over resistive subsurface models is studied with a 2-D forward and inverse scheme that can operate both in the quasi-static approximation and including displacement currents. Forward computations of simple models exemplify how responses that allow for displacement currents deviate from responses computed in the quasi-static approximation. The differences become most obvious for highly resistive subsurface models of about 3000Ωm and more and at high frequencies. For such cases, the apparent resistivities and phases of the transverse magnetic (TM) and transverse electric (TE) modes are significantly smaller than in the quasi-static approximation. Along profiles traversing 2-D subsurface models, sign reversals in the real part of the vertical magnetic transfer function (VMT) are often more pronounced than in the quasi-static approximation. On both sides of such sign reversals, the responses computed including displacement currents are larger than typical measurement errors. The 2-D inversion of synthetic data computed including displacement currents demonstrates that serious misinterpretations in the form of artefacts in inverse models can be made if displacement currents are neglected during the inversion. Hence, the inclusion of the dielectric effect is a crucial improvement over existing quasi-static 2-D inverse schemes. Synthetic data from a 2-D model with constant dielectric permittivity and a conductive block buried in a highly resistive layer, which in turn is underlain by a conductive layer, are inverted. In the quasi-static inverse model, the depth to the conductive structures is overestimated, artefactual resistors appear on both sides of the
New generation transistor technologies enabled by 2D crystals
NASA Astrophysics Data System (ADS)
Jena, D.
2013-05-01
The discovery of graphene opened the door to 2D crystal materials. The lack of a bandgap in 2D graphene makes it unsuitable for electronic switching transistors in the conventional field-effect sense, though possible techniques exploiting the unique bandstructure and nanostructures are being explored. The transition metal dichalcogenides have 2D crystal semiconductors, which are well-suited for electronic switching. We experimentally demonstrate field effect transistors with current saturation and carrier inversion made from layered 2D crystal semiconductors such as MoS2, WS2, and the related family. We also evaluate the feasibility of such semiconducting 2D crystals for tunneling field effect transistors for low-power digital logic. The article summarizes the current state of new generation transistor technologies either proposed, or demonstrated, with a commentary on the challenges and prospects moving forward.
Time-Lapse Joint Inversion of Cross-Well DC Resistivity and Seismic Data: A Numerical Investigation
Time-lapse joint inversion of geophysical data is required to image the evolution of oil reservoirs during production and enhanced oil recovery, CO2 sequestration, geothermal fields during production, and to monitor the evolution of contaminant plumes. Joint inversion schemes red...
Optoelectronics with 2D semiconductors
NASA Astrophysics Data System (ADS)
Mueller, Thomas
2015-03-01
Two-dimensional (2D) atomic crystals, such as graphene and layered transition-metal dichalcogenides, are currently receiving a lot of attention for applications in electronics and optoelectronics. In this talk, I will review our research activities on electrically driven light emission, photovoltaic energy conversion and photodetection in 2D semiconductors. In particular, WSe2 monolayer p-n junctions formed by electrostatic doping using a pair of split gate electrodes, type-II heterojunctions based on MoS2/WSe2 and MoS2/phosphorene van der Waals stacks, 2D multi-junction solar cells, and 3D/2D semiconductor interfaces will be presented. Upon optical illumination, conversion of light into electrical energy occurs in these devices. If an electrical current is driven, efficient electroluminescence is obtained. I will present measurements of the electrical characteristics, the optical properties, and the gate voltage dependence of the device response. In the second part of my talk, I will discuss photoconductivity studies of MoS2 field-effect transistors. We identify photovoltaic and photoconductive effects, which both show strong photoconductive gain. A model will be presented that reproduces our experimental findings, such as the dependence on optical power and gate voltage. We envision that the efficient photon conversion and light emission, combined with the advantages of 2D semiconductors, such as flexibility, high mechanical stability and low costs of production, could lead to new optoelectronic technologies.
SEM signal emulation for 2D patterns
NASA Astrophysics Data System (ADS)
Sukhov, Evgenii; Muelders, Thomas; Klostermann, Ulrich; Gao, Weimin; Braylovska, Mariya
2016-03-01
The application of accurate and predictive physical resist simulation is seen as one important use model for fast and efficient exploration of new patterning technology options, especially if fully qualified OPC models are not yet available at an early pre-production stage. The methodology of using a top-down CD-SEM metrology to extract the 3D resist profile information, such as the critical dimension (CD) at various resist heights, has to be associated with a series of presumptions which may introduce such small, but systematic CD errors. Ideally, the metrology effects should be carefully minimized during measurement process, or if possible be taken into account through proper metrology modeling. In this paper we discuss the application of a fast SEM signal emulation describing the SEM image formation. The algorithm is applied to simulated resist 3D profiles and produces emulated SEM image results for 1D and 2D patterns. It allows estimating resist simulation quality by comparing CDs which were extracted from the emulated and from the measured SEM images. Moreover, SEM emulation is applied for resist model calibration to capture subtle error signatures through dose and defocus. Finally, it should be noted that our SEM emulation methodology is based on the approximation of physical phenomena which are taking place in real SEM image formation. This approximation allows achieving better speed performance compared to a fully physical model.
NASA Astrophysics Data System (ADS)
Tønning, Erik; Polders, Daniel; Callaghan, Paul T.; Engelsen, Søren B.
2007-09-01
This paper demonstrates how the multi-linear PARAFAC model can with advantage be used to decompose 2D diffusion-relaxation correlation NMR spectra prior to 2D-Laplace inversion to the T2- D domain. The decomposition is advantageous for better interpretation of the complex correlation maps as well as for the quantification of extracted T2- D components. To demonstrate the new method seventeen mixtures of wheat flour, starch, gluten, oil and water were prepared and measured with a 300 MHz nuclear magnetic resonance (NMR) spectrometer using a pulsed gradient stimulated echo (PGSTE) pulse sequence followed by a Carr-Purcell-Meiboom-Gill (CPMG) pulse echo train. By varying the gradient strength, 2D diffusion-relaxation data were recorded for each sample. From these double exponentially decaying relaxation data the PARAFAC algorithm extracted two unique diffusion-relaxation components, explaining 99.8% of the variation in the data set. These two components were subsequently transformed to the T2- D domain using 2D-inverse Laplace transformation and quantitatively assigned to the oil and water components of the samples. The oil component was one distinct distribution with peak intensity at D = 3 × 10 -12 m 2 s -1 and T2 = 180 ms. The water component consisted of two broad populations of water molecules with diffusion coefficients and relaxation times centered around correlation pairs: D = 10 -9 m 2 s -1, T2 = 10 ms and D = 3 × 10 -13 m 2 s -1, T2 = 13 ms. Small spurious peaks observed in the inverse Laplace transformation of original complex data were effectively filtered by the PARAFAC decomposition and thus considered artefacts from the complex Laplace transformation. The oil-to-water ratio determined by PARAFAC followed by 2D-Laplace inversion was perfectly correlated with known oil-to-water ratio of the samples. The new method of using PARAFAC prior to the 2D-Laplace inversion proved to have superior potential in analysis of diffusion-relaxation spectra, as it
Sevrin, A.
1993-06-01
After reviewing some aspects of gravity in two dimensions, I show that non-trivial embeddings of sl(2) in a semi-simple (super) Lie algebra give rise to a very large class of extensions of 2D gravity. The induced action is constructed as a gauged WZW model and an exact expression for the effective action is given.
In situ fluid typing and quantification with 1D and 2D NMR logging.
Sun, Boqin
2007-05-01
In situ nuclear magnetic resonance (NMR) fluid typing has recently gained momentum due to data acquisition and inversion algorithm enhancement of NMR logging tools. T(2) distributions derived from NMR logging contain information on bulk fluids and pore size distributions. However, the accuracy of fluid typing is greatly overshadowed by the overlap between T(2) peaks arising from different fluids with similar apparent T(2) relaxation times. Nevertheless, the shapes of T(2) distributions from different fluid components are often different and can be predetermined. Inversion with predetermined T(2) distributions allows us to perform fluid component decomposition to yield individual fluid volume ratios. Another effective method for in situ fluid typing is two-dimensional (2D) NMR logging, which results in proton population distribution as a function of T(2) relaxation time and fluid diffusion coefficient (or T(1) relaxation time). Since diffusion coefficients (or T(1) relaxation time) for different fluid components can be very different, it is relatively easy to separate oil (especially heavy oil) from water signal in a 2D NMR map and to perform accurate fluid typing. Combining NMR logging with resistivity and/or neutron/density logs provides a third method for in situ fluid typing. We shall describe these techniques with field examples.
Graphene suspensions for 2D printing
NASA Astrophysics Data System (ADS)
Soots, R. A.; Yakimchuk, E. A.; Nebogatikova, N. A.; Kotin, I. A.; Antonova, I. V.
2016-04-01
It is shown that, by processing a graphite suspension in ethanol or water by ultrasound and centrifuging, it is possible to obtain particles with thicknesses within 1-6 nm and, in the most interesting cases, 1-1.5 nm. Analogous treatment of a graphite suspension in organic solvent yields eventually thicker particles (up to 6-10 nm thick) even upon long-term treatment. Using the proposed ink based on graphene and aqueous ethanol with ethylcellulose and terpineol additives for 2D printing, thin (~5 nm thick) films with sheet resistance upon annealing ~30 MΩ/□ were obtained. With the ink based on aqueous graphene suspension, the sheet resistance was ~5-12 kΩ/□ for 6- to 15-nm-thick layers with a carrier mobility of ~30-50 cm2/(V s).
Radiative heat transfer in 2D Dirac materials.
Rodriguez-López, Pablo; Tse, Wang-Kong; Dalvit, Diego A R
2015-06-03
We compute the radiative heat transfer between two sheets of 2D Dirac materials, including topological Chern insulators and graphene, within the framework of the local approximation for the optical response of these materials. In this approximation, which neglects spatial dispersion, we derive both numerically and analytically the short-distance asymptotic of the near-field heat transfer in these systems, and show that it scales as the inverse of the distance between the two sheets. Finally, we discuss the limitations to the validity of this scaling law imposed by spatial dispersion in 2D Dirac materials.
Radiative heat transfer in 2D Dirac materials
Rodriguez-López, Pablo; Tse, Wang -Kong; Dalvit, Diego A. R.
2015-05-12
We compute the radiative heat transfer between two sheets of 2D Dirac materials, including topological Chern insulators and graphene, within the framework of the local approximation for the optical response of these materials. In this approximation, which neglects spatial dispersion, we derive both numerically and analytically the short-distance asymptotic of the near-field heat transfer in these systems, and show that it scales as the inverse of the distance between the two sheets. In conclusion, we discuss the limitations to the validity of this scaling law imposed by spatial dispersion in 2D Dirac materials.
Song, SuJin; Paik, Hee-Young; Song, YoonJu
2012-12-01
We investigated the association between dietary patterns and insulin resistance in the 3871 healthy Korean adults from the 2007 to 2008 Korea National Health and Nutrition Examination Survey. The whole grains and beans pattern was associated with lower prevalence of insulin resistance (OR for highest quintile=0.80, 95% CI=0.61-1.03, P for trend=0.013).
Strain-induced Fermi contour anisotropy of GaAs (311)A 2D holes
NASA Astrophysics Data System (ADS)
Shabani, Javad; Shayegan, Mansour; Winkler, Roland
2008-03-01
There is considerable current interest in electronic properties of two-dimensional (2D) carriers whose energy bands are spin-split at finite values of in-plane wave vector, thanks to the spin-orbit interaction and the lack of inversion symmetry. We report experimental and theoretical results revealing that the spin-subband Fermi contours of the heavy and light heavy-holes (HHh and HHl) can be tuned in high mobility GaAs (311)A 2D hole systems via the application of symmetry-breaking in-plane strain. Our calculations show that the HHl spin-subband Fermi contour is circular but the HHh spin-subband Fermi contour is distorted. Experimentally, we probe the Fermi contour anisotropy by measuring the magneto-resistance commensurability peaks induced by square arrays of antidots. When the spin splitting is sufficiently large, the magneto-resistance trace exhibits two peaks, providing clear evidence for spin-resolved ballistic transport. The experimental results are in good agreement with the calculations, and confirm that the majority spin-subband (HHh) has a severely distorted Fermi contour whose anisotropy can be tuned with strain while Fermi contour of the minority spin-subband (HHl) remains nearly isotropic.
2D ERT imaging of tracer dispersion in laboratory experiments
NASA Astrophysics Data System (ADS)
Lekmine, G.; Pessel, M.; Auradou, H.
2009-12-01
Electrical resistivity tomography applied in cross-borehole is a method often used to follow the invasion process of pollutants. The aim of this work is to test experimentally the electrode arrays and inversion processes used to obtain a spatial representation of tracer propagation in porous media. Experiments were conducted in a plexiglass container with glass beads of 166 microns in diameter. The height of the container is 275 mm, its width 85 mm and its thickness 10 mm. 21 electrodes, equally spaced, are placed along each of the lateral sides of the porous medium : these electrodes are used to perform the electrical measurements. The device is lightened from behind and a video camera records the fluid propagation. The tracer (i.e the pollutant) is a water solution containing a known amount of dye together with NaCl (0.5g/l up to 1.5g/l). The medium is first saturated by a water solution containing a slight concentration of NaCl so that its density is smaller than the tracer’s. An upward flow is first established, the denser fluid is injected at the bottom and over the full width of the medium. In this way, the flow is stabilized by gravity avoiding the development of unstable fingers. Still, the fluids are miscible and a mixing front develops during the flow: in the present study, the interest is to estimate the 2D tracer front dispersion by both optical and electrical imaging. The comparison of the two techniques allows to study the ability of the inversion process to quantify the solute transport. A sensitivity analysis is led in order to determine the best measurement sequence to monitor the tracer’s front evolution through the entire volume of the medium. Hence, each time step is constituted by the same 190 transverse dipole-dipole set of lasting 5 minutes between the first and the last measurement. At the laboratory scale, the experimental design affects the measurements through edges effects: most of these artefacts can be partially suppressed by using
NASA Astrophysics Data System (ADS)
Zhang, Zhi-Yong; Tan, Han-Dong; Wang, Kun-Peng; Lin, Chang-Hong; Zhang, Bin; Xie, Mao-Bi
2016-03-01
Traditional two-dimensional (2D) complex resistivity forward modeling is based on Poisson's equation but spectral induced polarization (SIP) data are the coproducts of the induced polarization (IP) and the electromagnetic induction (EMI) effects. This is especially true under high frequencies, where the EMI effect can exceed the IP effect. 2D inversion that only considers the IP effect reduces the reliability of the inversion data. In this paper, we derive differential equations using Maxwell's equations. With the introduction of the Cole-Cole model, we use the finite-element method to conduct 2D SIP forward modeling that considers the EMI and IP effects simultaneously. The data-space Occam method, in which different constraints to the model smoothness and parametric boundaries are introduced, is then used to simultaneously obtain the four parameters of the Cole—Cole model using multi-array electric field data. This approach not only improves the stability of the inversion but also significantly reduces the solution ambiguity. To improve the computational efficiency, message passing interface programming was used to accelerate the 2D SIP forward modeling and inversion. Synthetic datasets were tested using both serial and parallel algorithms, and the tests suggest that the proposed parallel algorithm is robust and efficient.
2D quasiperiodic plasmonic crystals
Bauer, Christina; Kobiela, Georg; Giessen, Harald
2012-01-01
Nanophotonic structures with irregular symmetry, such as quasiperiodic plasmonic crystals, have gained an increasing amount of attention, in particular as potential candidates to enhance the absorption of solar cells in an angular insensitive fashion. To examine the photonic bandstructure of such systems that determines their optical properties, it is necessary to measure and model normal and oblique light interaction with plasmonic crystals. We determine the different propagation vectors and consider the interaction of all possible waveguide modes and particle plasmons in a 2D metallic photonic quasicrystal, in conjunction with the dispersion relations of a slab waveguide. Using a Fano model, we calculate the optical properties for normal and inclined light incidence. Comparing measurements of a quasiperiodic lattice to the modelled spectra for angle of incidence variation in both azimuthal and polar direction of the sample gives excellent agreement and confirms the predictive power of our model. PMID:23209871
NASA Astrophysics Data System (ADS)
Schaibley, John R.; Yu, Hongyi; Clark, Genevieve; Rivera, Pasqual; Ross, Jason S.; Seyler, Kyle L.; Yao, Wang; Xu, Xiaodong
2016-11-01
Semiconductor technology is currently based on the manipulation of electronic charge; however, electrons have additional degrees of freedom, such as spin and valley, that can be used to encode and process information. Over the past several decades, there has been significant progress in manipulating electron spin for semiconductor spintronic devices, motivated by potential spin-based information processing and storage applications. However, experimental progress towards manipulating the valley degree of freedom for potential valleytronic devices has been limited until very recently. We review the latest advances in valleytronics, which have largely been enabled by the isolation of 2D materials (such as graphene and semiconducting transition metal dichalcogenides) that host an easily accessible electronic valley degree of freedom, allowing for dynamic control.
Georgi, Howard; Kats, Yevgeny
2008-09-26
We discuss what can be learned about unparticle physics by studying simple quantum field theories in one space and one time dimension. We argue that the exactly soluble 2D theory of a massless fermion coupled to a massive vector boson, the Sommerfield model, is an interesting analog of a Banks-Zaks model, approaching a free theory at high energies and a scale-invariant theory with nontrivial anomalous dimensions at low energies. We construct a toy standard model coupling to the fermions in the Sommerfield model and study how the transition from unparticle behavior at low energies to free particle behavior at high energies manifests itself in interactions with the toy standard model particles.
Rodríguez, Ana; Shimada, Takehiko; Cervera, Magdalena; Redondo, Ana; Alquézar, Berta; Rodrigo, María Jesús; Zacarías, Lorenzo; Palou, Lluís; López, María M; Peña, Leandro
2015-01-01
Volatile organic compounds (VOCs) are secondary metabolites acting as a language for the communication of plants with the environment. In orange fruits, the monoterpene D-limonene accumulates at very high levels in oil glands from the peel. Drastic down-regulation of D-limonene synthase gene expression in the peel of transgenic oranges harboring a D-limonene synthase transgene in antisense (AS) configuration altered the monoterpene profile in oil glands, mainly resulting in reduced accumulation of D-limonene. This led to fruit resistance against Penicillium digitatum (Pd), Xanthomonas citri subsp. citri (Xcc) and other specialized pathogens. Here, we analyze resistance to pathogens in independent AS and empty vector (EV) lines, which have low, medium or high D-limonene concentrations and show that the level of resistance is inversely related to the accumulation of D-limonene in orange peels, thus explaining the need of high D-limonene accumulation in mature oranges in nature for the efficient attraction of specialized microorganism frugivores. PMID:26023857
Rodríguez, Ana; Shimada, Takehiko; Cervera, Magdalena; Redondo, Ana; Alquézar, Berta; Rodrigo, María Jesús; Zacarías, Lorenzo; Palou, Lluís; López, María M; Peña, Leandro
2015-01-01
Volatile organic compounds (VOCs) are secondary metabolites acting as a language for the communication of plants with the environment. In orange fruits, the monoterpene D-limonene accumulates at very high levels in oil glands from the peel. Drastic down-regulation of D-limonene synthase gene expression in the peel of transgenic oranges harboring a D-limonene synthase transgene in antisense (AS) configuration altered the monoterpene profile in oil glands, mainly resulting in reduced accumulation of D-limonene. This led to fruit resistance against Penicillium digitatum (Pd), Xanthomonas citri subsp. citri (Xcc) and other specialized pathogens. Here, we analyze resistance to pathogens in independent AS and empty vector (EV) lines, which have low, medium or high D-limonene concentrations and show that the level of resistance is inversely related to the accumulation of D-limonene in orange peels, thus explaining the need of high D-limonene accumulation in mature oranges in nature for the efficient attraction of specialized microorganism frugivores.
Quantum coherence selective 2D Raman–2D electronic spectroscopy
Spencer, Austin P.; Hutson, William O.; Harel, Elad
2017-01-01
Electronic and vibrational correlations report on the dynamics and structure of molecular species, yet revealing these correlations experimentally has proved extremely challenging. Here, we demonstrate a method that probes correlations between states within the vibrational and electronic manifold with quantum coherence selectivity. Specifically, we measure a fully coherent four-dimensional spectrum which simultaneously encodes vibrational–vibrational, electronic–vibrational and electronic–electronic interactions. By combining near-impulsive resonant and non-resonant excitation, the desired fifth-order signal of a complex organic molecule in solution is measured free of unwanted lower-order contamination. A critical feature of this method is electronic and vibrational frequency resolution, enabling isolation and assignment of individual quantum coherence pathways. The vibronic structure of the system is then revealed within an otherwise broad and featureless 2D electronic spectrum. This method is suited for studying elusive quantum effects in which electronic transitions strongly couple to phonons and vibrations, such as energy transfer in photosynthetic pigment–protein complexes. PMID:28281541
Quantum coherence selective 2D Raman-2D electronic spectroscopy
NASA Astrophysics Data System (ADS)
Spencer, Austin P.; Hutson, William O.; Harel, Elad
2017-03-01
Electronic and vibrational correlations report on the dynamics and structure of molecular species, yet revealing these correlations experimentally has proved extremely challenging. Here, we demonstrate a method that probes correlations between states within the vibrational and electronic manifold with quantum coherence selectivity. Specifically, we measure a fully coherent four-dimensional spectrum which simultaneously encodes vibrational-vibrational, electronic-vibrational and electronic-electronic interactions. By combining near-impulsive resonant and non-resonant excitation, the desired fifth-order signal of a complex organic molecule in solution is measured free of unwanted lower-order contamination. A critical feature of this method is electronic and vibrational frequency resolution, enabling isolation and assignment of individual quantum coherence pathways. The vibronic structure of the system is then revealed within an otherwise broad and featureless 2D electronic spectrum. This method is suited for studying elusive quantum effects in which electronic transitions strongly couple to phonons and vibrations, such as energy transfer in photosynthetic pigment-protein complexes.
Quantum coherence selective 2D Raman-2D electronic spectroscopy.
Spencer, Austin P; Hutson, William O; Harel, Elad
2017-03-10
Electronic and vibrational correlations report on the dynamics and structure of molecular species, yet revealing these correlations experimentally has proved extremely challenging. Here, we demonstrate a method that probes correlations between states within the vibrational and electronic manifold with quantum coherence selectivity. Specifically, we measure a fully coherent four-dimensional spectrum which simultaneously encodes vibrational-vibrational, electronic-vibrational and electronic-electronic interactions. By combining near-impulsive resonant and non-resonant excitation, the desired fifth-order signal of a complex organic molecule in solution is measured free of unwanted lower-order contamination. A critical feature of this method is electronic and vibrational frequency resolution, enabling isolation and assignment of individual quantum coherence pathways. The vibronic structure of the system is then revealed within an otherwise broad and featureless 2D electronic spectrum. This method is suited for studying elusive quantum effects in which electronic transitions strongly couple to phonons and vibrations, such as energy transfer in photosynthetic pigment-protein complexes.
Sparse radar imaging using 2D compressed sensing
NASA Astrophysics Data System (ADS)
Hou, Qingkai; Liu, Yang; Chen, Zengping; Su, Shaoying
2014-10-01
Radar imaging is an ill-posed linear inverse problem and compressed sensing (CS) has been proved to have tremendous potential in this field. This paper surveys the theory of radar imaging and a conclusion is drawn that the processing of ISAR imaging can be denoted mathematically as a problem of 2D sparse decomposition. Based on CS, we propose a novel measuring strategy for ISAR imaging radar and utilize random sub-sampling in both range and azimuth dimensions, which will reduce the amount of sampling data tremendously. In order to handle 2D reconstructing problem, the ordinary solution is converting the 2D problem into 1D by Kronecker product, which will increase the size of dictionary and computational cost sharply. In this paper, we introduce the 2D-SL0 algorithm into the reconstruction of imaging. It is proved that 2D-SL0 can achieve equivalent result as other 1D reconstructing methods, but the computational complexity and memory usage is reduced significantly. Moreover, we will state the results of simulating experiments and prove the effectiveness and feasibility of our method.
Alkerwi, Ala'a; Sauvageot, Nicolas; Crichton, Georgina E; Elias, Merrill F; Stranges, Saverio
2016-05-01
This study examined the association of chocolate consumption with insulin resistance and serum liver enzymes in a national sample of adults in Luxembourg. A random sample of 1153 individuals, aged 18-69 years, was recruited to participate in the cross-sectional Observation of Cardiovascular Risk Factors in Luxembourg study. Chocolate consumption (g/d) was obtained from a semi-quantitative FFQ. Blood glucose and insulin levels were used for the homoeostasis model assessment of insulin resistance (HOMA-IR). Hepatic biomarkers such as serum γ-glutamyl-transpeptidase (γ-GT), serum aspartate transaminase and serum alanine transaminase (ALT) (mg/l) were assessed using standard laboratory assays. Chocolate consumers (81·8 %) were more likely to be younger, physically active, affluent people with higher education levels and fewer chronic co-morbidities. After excluding subjects taking antidiabetic medications, higher chocolate consumption was associated with lower HOMA-IR (β=-0·16, P=0·004), serum insulin levels (β=-0·16, P=0·003) and γ-GT (β=-0·12, P=0·009) and ALT (β=-0·09, P=0·004), after adjustment for age, sex, education, lifestyle and dietary confounding factors, including intakes of fruits and vegetables, alcohol, polyphenol-rich coffee and tea. This study reports an independent inverse relationship between daily chocolate consumption and levels of insulin, HOMA-IR and liver enzymes in adults, suggesting that chocolate consumption may improve liver enzymes and protect against insulin resistance, a well-established risk factor for cardiometabolic disorders. Further observational prospective research and well-designed randomised-controlled studies are needed to confirm this cross-sectional relationship and to comprehend the role and mechanisms that different types of chocolate may play in insulin resistance and cardiometabolic disorders.
Dirken, J J; Vlaanderen, W
1994-01-01
Inversion of the uterus is a rare complication of childbirth. A primigravida aged 21 and a multigravida aged 32, hospitalized as emergency cases because of inversion of the uterus with major blood loss, were treated with infusion of liquids (to combat shock), repositioning of the uterus under anaesthesia and prevention of reinversion by uterine tonics. Inversion of the uterus should be part of the differential diagnosis in every case of fluxus post partum.
Metrology for graphene and 2D materials
NASA Astrophysics Data System (ADS)
Pollard, Andrew J.
2016-09-01
The application of graphene, a one atom-thick honeycomb lattice of carbon atoms with superlative properties, such as electrical conductivity, thermal conductivity and strength, has already shown that it can be used to benefit metrology itself as a new quantum standard for resistance. However, there are many application areas where graphene and other 2D materials, such as molybdenum disulphide (MoS2) and hexagonal boron nitride (h-BN), may be disruptive, areas such as flexible electronics, nanocomposites, sensing and energy storage. Applying metrology to the area of graphene is now critical to enable the new, emerging global graphene commercial world and bridge the gap between academia and industry. Measurement capabilities and expertise in a wide range of scientific areas are required to address this challenge. The combined and complementary approach of varied characterisation methods for structural, chemical, electrical and other properties, will allow the real-world issues of commercialising graphene and other 2D materials to be addressed. Here, examples of metrology challenges that have been overcome through a multi-technique or new approach are discussed. Firstly, the structural characterisation of defects in both graphene and MoS2 via Raman spectroscopy is described, and how nanoscale mapping of vacancy defects in graphene is also possible using tip-enhanced Raman spectroscopy (TERS). Furthermore, the chemical characterisation and removal of polymer residue on chemical vapour deposition (CVD) grown graphene via secondary ion mass spectrometry (SIMS) is detailed, as well as the chemical characterisation of iron films used to grow large domain single-layer h-BN through CVD growth, revealing how contamination of the substrate itself plays a role in the resulting h-BN layer. In addition, the role of international standardisation in this area is described, outlining the current work ongoing in both the International Organization of Standardization (ISO) and the
NKG2D ligands as therapeutic targets
Spear, Paul; Wu, Ming-Ru; Sentman, Marie-Louise; Sentman, Charles L.
2013-01-01
The Natural Killer Group 2D (NKG2D) receptor plays an important role in protecting the host from infections and cancer. By recognizing ligands induced on infected or tumor cells, NKG2D modulates lymphocyte activation and promotes immunity to eliminate ligand-expressing cells. Because these ligands are not widely expressed on healthy adult tissue, NKG2D ligands may present a useful target for immunotherapeutic approaches in cancer. Novel therapies targeting NKG2D ligands for the treatment of cancer have shown preclinical success and are poised to enter into clinical trials. In this review, the NKG2D receptor and its ligands are discussed in the context of cancer, infection, and autoimmunity. In addition, therapies targeting NKG2D ligands in cancer are also reviewed. PMID:23833565
Corona-Meraz, Fernanda-Isadora; Navarro-Hernández, Rosa-Elena; Ruíz-Quezada, Sandra-Luz; Madrigal-Ruíz, Perla-Monserrat; Castro-Albarrán, Jorge; Chavarría-Ávila, Efraín; Guzmán-Ornelas, Milton-Omar; Gómez-Bañuelos, Eduardo; Petri, Marcelo-Herón; Ramírez-Cedano, Joel-Isidro; Aguilar-Aldrete, María-Elena; Ríos-Ibarra, Clara; Vázquez-Del Mercado, Mónica
2016-01-01
Background. In obesity there is a subclinical chronic low-grade inflammatory response where insulin resistance (IR) may develop. Chemerin is secreted in white adipose tissue and promotes low-grade inflammatory process, where it expressed CMKLR1 receptor. The role of chemerin and CMKLR1 in inflammatory process secondary to obesity is not defined yet. Methods. Cross-sectional study with 134 individuals classified as with and without obesity by body mass index (BMI) and IR. Body fat storage measurements and metabolic and inflammatory markers were measured by routine methods. Soluble chemerin and basal levels of insulin by ELISA and relative expression of CMKLR1 were evaluated with qPCR and 2−ΔΔCT method. Results. Differences (P < 0.05) were observed between obesity and lean individuals in body fat storage measurements and metabolic-inflammatory markers. Both CMKLR1 expression and chemerin levels were increased in obesity without IR. Soluble chemerin levels correlate with adiposity and metabolic markers (r = 8.8% to 38.5%), P < 0.05. Conclusion. The increment of CMKLR1 expression was associated with insulin production. Increased serum levels of chemerin in obesity were observed, favoring a dysmetabolic response. The results observed in this study suggest that both chemerin and CMKLR1 have opposite expression in the context of low-grade inflammatory response manifested in the development of IR. PMID:27239101
Structural Complexity and Phonon Physics in 2D Arsenenes.
Carrete, Jesús; Gallego, Luis J; Mingo, Natalio
2017-03-15
In the quest for stable 2D arsenic phases, four different structures have been recently claimed to be stable. We show that, due to phonon contributions, the relative stability of those structures differs from previous reports and depends crucially on temperature. We also show that one of those four phases is in fact mechanically unstable. Furthermore, our results challenge the common assumption of an inverse correlation between structural complexity and thermal conductivity. Instead, a richer picture emerges from our results, showing how harmonic interactions, anharmonicity, and symmetries all play a role in modulating thermal conduction in arsenenes. More generally, our conclusions highlight how vibrational properties are an essential element to be carefully taken into account in theoretical searches for new 2D materials.
Development of 2D SIP Data Processing Software for a Metallic Mineral Deposit Exploration
NASA Astrophysics Data System (ADS)
PARK, M.; Kim, K. S.; Seo, H. K.; Son, J.; Park, S.; Kim, C.; Kim, J. H.
2015-12-01
algorithm, we could get more reliable inversion result for the time-domain IP data. Therefore, it is expected the SIP method should be more popular if the developed 2D SIP processing software is widely used.
Improvement of electrical resistivity tomography for leachate injection monitoring
Clement, R.; Descloitres, M.; Guenther, T.; Oxarango, L.; Morra, C.
2010-03-15
Leachate recirculation is a key process in the scope of operating municipal waste landfills as bioreactors, which aims to increase the moisture content to optimize the biodegradation in landfills. Given that liquid flows exhibit a complex behaviour in very heterogeneous porous media, in situ monitoring methods are required. Surface time-lapse electrical resistivity tomography (ERT) is usually proposed. Using numerical modelling with typical 2D and 3D injection plume patterns and 2D and 3D inversion codes, we show that wrong changes of resistivity can be calculated at depth if standard parameters are used for time-lapse ERT inversion. Major artefacts typically exhibit significant increases of resistivity (more than +30%) which can be misinterpreted as gas migration within the waste. In order to eliminate these artefacts, we tested an advanced time-lapse ERT procedure that includes (i) two advanced inversion tools and (ii) two alternative array geometries. The first advanced tool uses invariant regions in the model. The second advanced tool uses an inversion with a 'minimum length' constraint. The alternative arrays focus on (i) a pole-dipole array (2D case), and (ii) a star array (3D case). The results show that these two advanced inversion tools and the two alternative arrays remove almost completely the artefacts within +/-5% both for 2D and 3D situations. As a field application, time-lapse ERT is applied using the star array during a 3D leachate injection in a non-hazardous municipal waste landfill. To evaluate the robustness of the two advanced tools, a synthetic model including both true decrease and increase of resistivity is built. The advanced time-lapse ERT procedure eliminates unwanted artefacts, while keeping a satisfactory image of true resistivity variations. This study demonstrates that significant and robust improvements can be obtained for time-lapse ERT monitoring of leachate recirculation in waste landfills.
Development of the Borehole 2-D Seismic Tomography Software Using MATLAB
NASA Astrophysics Data System (ADS)
Nugraha, A. D.; Syahputra, A.; Fatkhan, F.; Sule, R.; Hendriyana, A.
2011-12-01
We developed 2-D borehole seismic tomography software that we called "EARTHMAX-2D TOMOGRAPHY" to image subsurface physical properties including P-wave and S-wave velocities between two boreholes. We used Graphic User Interface (GUI) facilities of MATLAB programming language to create the software. In this software, we used travel time of seismic waves from source to receiver by using pseudo bending ray tracing method as input for tomography inversion. We can also set up a model parameterization, initial velocity model, ray tracing processes, conduct borehole seismic tomography inversion, and finally visualize the inversion results. The LSQR method was applied to solve of tomography inversion solution. We provided the Checkerboard Test Resolution (CTR) to evaluate the model resolution of the tomography inversion. As validation of this developed software, we tested it for geotechnical purposes. We then conducted data acquisition in the "ITB X-field" that is located on ITB campus. We used two boreholes that have a depth of 39 meters. Seismic wave sources were generated by impulse generator and sparker and then they were recorded by borehole hydrophone string type 3. Later on, we analyzed and picked seismic arrival time as input for tomography inversion. As results, we can image the estimated weathering layer, sediment layer, and basement rock in the field depicted by seismic wave structures. More detailed information about the developed software will be presented. Keywords: borehole, tomography, earthmax-2D, inversion
Quantitative 2D liquid-state NMR.
Giraudeau, Patrick
2014-06-01
Two-dimensional (2D) liquid-state NMR has a very high potential to simultaneously determine the absolute concentration of small molecules in complex mixtures, thanks to its capacity to separate overlapping resonances. However, it suffers from two main drawbacks that probably explain its relatively late development. First, the 2D NMR signal is strongly molecule-dependent and site-dependent; second, the long duration of 2D NMR experiments prevents its general use for high-throughput quantitative applications and affects its quantitative performance. Fortunately, the last 10 years has witnessed an increasing number of contributions where quantitative approaches based on 2D NMR were developed and applied to solve real analytical issues. This review aims at presenting these recent efforts to reach a high trueness and precision in quantitative measurements by 2D NMR. After highlighting the interest of 2D NMR for quantitative analysis, the different strategies to determine the absolute concentrations from 2D NMR spectra are described and illustrated by recent applications. The last part of the manuscript concerns the recent development of fast quantitative 2D NMR approaches, aiming at reducing the experiment duration while preserving - or even increasing - the analytical performance. We hope that this comprehensive review will help readers to apprehend the current landscape of quantitative 2D NMR, as well as the perspectives that may arise from it.
NASA Astrophysics Data System (ADS)
Meqbel, Naser; Weckmann, Ute; Muñoz, Gerard; Ritter, Oliver
2016-12-01
We report on a study to explore the deep electrical conductivity structure of the Dead Sea Basin (DSB) using magnetotelluric (MT) data collected along a transect across the DSB where the left lateral strike-slip Dead Sea transform (DST) fault splits into two fault strands forming one of the largest pull-apart basins of the world. A very pronounced feature of our 2-D inversion model is a deep, subvertical conductive zone beneath the DSB. The conductor extends through the entire crust and is sandwiched between highly resistive structures associated with Precambrian rocks of the basin flanks. The high electrical conductivity could be attributed to fluids released by dehydration of the uppermost mantle beneath the DSB, possibly in combination with fluids released by mid- to low-grade metamorphism in the lower crust and generation of hydrous minerals in the middle crust through retrograde metamorphism. Similar high conductivity zones associated with fluids have been reported from other large fault systems. The presence of fluids and hydrous minerals in the middle and lower crust could explain the required low friction coefficient of the DST along the eastern boundary of the DSB and the high subsidence rate of basin sediments. 3-D inversion models confirm the existence of a subvertical high conductivity structure underneath the DSB but its expression is far less pronounced. Instead, the 3-D inversion model suggests a deepening of the conductive DSB sediments off-profile towards the south, reaching a maximum depth of approximately 12 km, which is consistent with other geophysical observations. At shallower levels, the 3-D inversion model reveals salt diapirism as an upwelling of highly resistive structures, localized underneath the Al-Lisan Peninsula. The 3-D model furthermore contains an E-W elongated conductive structure to the northeast of the DSB. More MT data with better spatial coverage are required, however, to fully constrain the robustness of the above
NASA Astrophysics Data System (ADS)
Minami, T.; Toh, H.; Oshiman, N.
2010-12-01
The San-in region of SW Japan is classified as an area of high seismicity/volcanic activity, and thus many magneto-telluric (MT) and seismic observations have been conducted. Below this region, the Philippine Sea plate and the Pacific Sea plate are subducting into shallow and deep parts respectively, which makes the subsurface electrical structures very complicated. For example, Adakite rocks from Mt. Daisen, which is the biggest volcano made in the Quaternary, appeared penetrating the alkari rocks of theTertiary(Kimura et al., 2003) In addition the epicenters shallower than 30km in this region was broad planely in the west of Daisen and along about a east-west line in the east of Daisen (Shiozaki et al., 2003). In the San-in region, such seismic/volcanic properties have been studied only using land surveys. However, the studies based on land surveys are not enough to understand the epicenter distributions and where the edge of Philippine Sea plate reaches now, because Mt. Daisen and the distributed epicenters are located near the coastline. Our group, therefore, started seafloor electromagnetic (EM) observations off the San-in region in 2006. As a result, we have obtained seafloor EM data at 10 sites to date. In this study, we compared the accuracy of EM responses calculated by different two-dimensional (2-D) FEM codes using triangular and rectangular elements in order to make a new 2-D inversion code available along sea-land array. That’s why because there are few 2-D MT inversion codes available in a region with coastline. We used Ogawa and Uchida’s (1996) code for rectangular elements and Utada’s (1987) code for triangular ones. We worked on a bathymetry with a constant inclination between the land-sea boundary whose horizontal-to-vertical ratio is 25 up to 4km depth. Using this bathymetry, we conducted 2-D transverse magnetic (TM) forward modeling for both elements and compared the apparent resistivities and phases of MT impedances. As for triangular
Annotated Bibliography of EDGE2D Use
J.D. Strachan and G. Corrigan
2005-06-24
This annotated bibliography is intended to help EDGE2D users, and particularly new users, find existing published literature that has used EDGE2D. Our idea is that a person can find existing studies which may relate to his intended use, as well as gain ideas about other possible applications by scanning the attached tables.
Staring 2-D hadamard transform spectral imager
Gentry, Stephen M.; Wehlburg, Christine M.; Wehlburg, Joseph C.; Smith, Mark W.; Smith, Jody L.
2006-02-07
A staring imaging system inputs a 2D spatial image containing multi-frequency spectral information. This image is encoded in one dimension of the image with a cyclic Hadamarid S-matrix. The resulting image is detecting with a spatial 2D detector; and a computer applies a Hadamard transform to recover the encoded image.
NASA Astrophysics Data System (ADS)
Kasprzak, Marek; Traczyk, Andrzej
2014-06-01
In urbanized areas, particularly in lowland terrains and floors of large river valleys, the natural land configuration is often hard to recognize due to a long history of human activity. Accordingly, archaeological works in cities, which supply knowledge on settlement conditions, are usually accompanied by geological and geomophological research. Lately, data from light detection and ranging (LiDAR) have become a valuable source of information on urban land configuration. Geophysical methods are also becoming increasingly popular in background studies. The paper presents a method of using and linking these sources of spatial information about landforms in such areas. The main aim is to identify to what extent these complementary sources of data and the proposed method can be used in such a specific environment to reconstruct natural, buried terrain morphology. The city of Wrocław in Central Europe serves as an example. To this end geomorphometric studies were conducted with the use of digital elevation models (DEMs) based on LiDAR scanning and derivated land-surface parameters—SAGA Wetness Index, Channel Network Base Level and Altitude above Channel Network. The study also involved determining morphological edges and measurements of the meanders of the Odra, as well as expanding information on the spatial distribution of alluvia and the structure of slope breaks. To this end, geophysical measurements were conducted using the Two-Dimensional Electrical Resistivity Tomography method. Additionally, five typical sequences of man-made ground present within the perimeter of the city were distinguished. As a result, a map of the main landforms of Wrocław is presented. Finally, we argue that although high resolution DEM and derivate land-surface parameters are very useful in terrain analysis, places with thick man-made ground or strongly levelled areas must be recognized by geoarchaeological excavations or geological bore holes. The geophysical survey is useful to
MT2DInvMatlab—A program in MATLAB and FORTRAN for two-dimensional magnetotelluric inversion
NASA Astrophysics Data System (ADS)
Lee, Seong Kon; Kim, Hee Joon; Song, Yoonho; Lee, Choon-Ki
2009-08-01
MT2DInvMatlab is an open-source MATLAB® software package for two-dimensional (2D) inversion of magnetotelluric (MT) data; it is written in mixed languages of MATLAB and FORTRAN. MT2DInvMatlab uses the finite element method (FEM) to compute 2D MT model responses, and smoothness-constrained least-squares inversion with a spatially variable regularization parameter algorithm to stabilize the inversion process and provide a high-resolution optimal earth model. It is also able to include terrain effects in inversion by incorporating topography into a forward model. This program runs under the MATLAB environment so that users can utilize the existing general interface of MATLAB, while some specific functions are written in FORTRAN 90 to speed up computation and reuse pre-existing FORTRAN code in the MATLAB environment with minimal modification. This program has been tested using synthetic models, including one with variable topography, and on field data. The results were assessed by comparing inverse models obtained with MT2DInvMatlab and with a non-linear conjugate gradient (NLCG) algorithm. In both tests the new inversion software reconstructs the subsurface resistivity structure very closely and provides an improvement in both resolution and stability.
2007-06-05
tive to the AMF, [1] and [5] discovered that multi-channel and two-dimensional parametric estimation approaches could (1) reduce the computational...dimensional (2-D) parametric estimation using the 2-D least-squares-based lattice algorithm [4]. The specifics of the inverse are found in the next...non- parametric estimation techniques • Least square error (LSE) vs mean square error (MSE) • Primarily multi-channel (M-C) structures; also try 2-D
ATM-dependent phosphorylation of MEF2D promotes neuronal survival after DNA damage.
Chan, Shing Fai; Sances, Sam; Brill, Laurence M; Okamoto, Shu-Ichi; Zaidi, Rameez; McKercher, Scott R; Akhtar, Mohd W; Nakanishi, Nobuki; Lipton, Stuart A
2014-03-26
Mutations in the ataxia telangiectasia mutated (ATM) gene, which encodes a kinase critical for the normal DNA damage response, cause the neurodegenerative disorder ataxia-telangiectasia (AT). The substrates of ATM in the brain are poorly understood. Here we demonstrate that ATM phosphorylates and activates the transcription factor myocyte enhancer factor 2D (MEF2D), which plays a critical role in promoting survival of cerebellar granule cells. ATM associates with MEF2D after DNA damage and phosphorylates the transcription factor at four ATM consensus sites. Knockdown of endogenous MEF2D with a short-hairpin RNA (shRNA) increases sensitivity to etoposide-induced DNA damage and neuronal cell death. Interestingly, substitution of endogenous MEF2D with an shRNA-resistant phosphomimetic MEF2D mutant protects cerebellar granule cells from cell death after DNA damage, whereas an shRNA-resistant nonphosphorylatable MEF2D mutant does not. In vivo, cerebella in Mef2d knock-out mice manifest increased susceptibility to DNA damage. Together, our results show that MEF2D is a substrate for phosphorylation by ATM, thus promoting survival in response to DNA damage. Moreover, dysregulation of the ATM-MEF2D pathway may contribute to neurodegeneration in AT.
NASA Astrophysics Data System (ADS)
Lekmine, G.; Auradou, H.; Pessel, M.; Rayner, J. L.
2017-04-01
Cross-borehole ERT imaging was tested to quantify the average velocity and transport parameters of tracer plumes in saturated porous media. Seven tracer tests were performed at different flow rates and monitored by either a vertical or horizontal dipole-dipole ERT sequence. These sequences were tested to reconstruct the shape and temporally follow the spread of the tracer plumes through a background regularization procedure. Data sets were inverted with the same inversion parameters and 2D model sections of resistivity ratios were converted to tracer concentrations. Both array types provided an accurate estimation of the average pore velocity vz. The total mass Mtot recovered was always overestimated by the horizontal dipole-dipole and underestimated by the vertical dipole-dipole. The vertical dipole-dipole was however reliable to quantify the longitudinal dispersivity λz, while the horizontal dipole-dipole returned better estimation for the transverse component λx. λ and Mtot were mainly influenced by the 2D distribution of the cumulated electrical sensitivity and the Shadow Effects induced by the third dimension. The size reduction of the edge of the plume was also related to the inability of the inversion process to reconstruct sharp resistivity contrasts at the interface. Smoothing was counterbalanced by a non-realistic rise of the ERT concentrations around the centre of mass returning overpredicted total masses. A sensitivity analysis on the cementation factor m and the porosity ϕ demonstrated that a change in one of these parameters by 8% involved non negligible variations by 30 and 40% of the dispersion coefficients and mass recovery.
Differential patterns of 2D location versus depth decoding along the visual hierarchy.
Finlayson, Nonie J; Zhang, Xiaoli; Golomb, Julie D
2017-02-15
Visual information is initially represented as 2D images on the retina, but our brains are able to transform this input to perceive our rich 3D environment. While many studies have explored 2D spatial representations or depth perception in isolation, it remains unknown if or how these processes interact in human visual cortex. Here we used functional MRI and multi-voxel pattern analysis to investigate the relationship between 2D location and position-in-depth information. We stimulated different 3D locations in a blocked design: each location was defined by horizontal, vertical, and depth position. Participants remained fixated at the center of the screen while passively viewing the peripheral stimuli with red/green anaglyph glasses. Our results revealed a widespread, systematic transition throughout visual cortex. As expected, 2D location information (horizontal and vertical) could be strongly decoded in early visual areas, with reduced decoding higher along the visual hierarchy, consistent with known changes in receptive field sizes. Critically, we found that the decoding of position-in-depth information tracked inversely with the 2D location pattern, with the magnitude of depth decoding gradually increasing from intermediate to higher visual and category regions. Representations of 2D location information became increasingly location-tolerant in later areas, where depth information was also tolerant to changes in 2D location. We propose that spatial representations gradually transition from 2D-dominant to balanced 3D (2D and depth) along the visual hierarchy.
Ginsparg, P.
1991-01-01
These are introductory lectures for a general audience that give an overview of the subject of matrix models and their application to random surfaces, 2d gravity, and string theory. They are intentionally 1.5 years out of date.
Ginsparg, P.
1991-12-31
These are introductory lectures for a general audience that give an overview of the subject of matrix models and their application to random surfaces, 2d gravity, and string theory. They are intentionally 1.5 years out of date.
Brittle damage models in DYNA2D
Faux, D.R.
1997-09-01
DYNA2D is an explicit Lagrangian finite element code used to model dynamic events where stress wave interactions influence the overall response of the system. DYNA2D is often used to model penetration problems involving ductile-to-ductile impacts; however, with the advent of the use of ceramics in the armor-anti-armor community and the need to model damage to laser optics components, good brittle damage models are now needed in DYNA2D. This report will detail the implementation of four brittle damage models in DYNA2D, three scalar damage models and one tensor damage model. These new brittle damage models are then used to predict experimental results from three distinctly different glass damage problems.
NASA Astrophysics Data System (ADS)
Dekker, T.; de Zwart, S. T.; Willemsen, O. H.; Hiddink, M. G. H.; IJzerman, W. L.
2006-02-01
A prerequisite for a wide market acceptance of 3D displays is the ability to switch between 3D and full resolution 2D. In this paper we present a robust and cost effective concept for an auto-stereoscopic switchable 2D/3D display. The display is based on an LCD panel, equipped with switchable LC-filled lenticular lenses. We will discuss 3D image quality, with the focus on display uniformity. We show that slanting the lenticulars in combination with a good lens design can minimize non-uniformities in our 20" 2D/3D monitors. Furthermore, we introduce fractional viewing systems as a very robust concept to further improve uniformity in the case slanting the lenticulars and optimizing the lens design are not sufficient. We will discuss measurements and numerical simulations of the key optical characteristics of this display. Finally, we discuss 2D image quality, the switching characteristics and the residual lens effect.
2-d Finite Element Code Postprocessor
Sanford, L. A.; Hallquist, J. O.
1996-07-15
ORION is an interactive program that serves as a postprocessor for the analysis programs NIKE2D, DYNA2D, TOPAZ2D, and CHEMICAL TOPAZ2D. ORION reads binary plot files generated by the two-dimensional finite element codes currently used by the Methods Development Group at LLNL. Contour and color fringe plots of a large number of quantities may be displayed on meshes consisting of triangular and quadrilateral elements. ORION can compute strain measures, interface pressures along slide lines, reaction forces along constrained boundaries, and momentum. ORION has been applied to study the response of two-dimensional solids and structures undergoing finite deformations under a wide variety of large deformation transient dynamic and static problems and heat transfer analyses.
Chemical Approaches to 2D Materials.
Samorì, Paolo; Palermo, Vincenzo; Feng, Xinliang
2016-08-01
Chemistry plays an ever-increasing role in the production, functionalization, processing and applications of graphene and other 2D materials. This special issue highlights a selection of enlightening chemical approaches to 2D materials, which nicely reflect the breadth of the field and convey the excitement of the individuals involved in it, who are trying to translate graphene and related materials from the laboratory into a real, high-impact technology.
Measurements of Effective Schottky Barrier in Inverse Extraordinary Optoconductance Structures
NASA Astrophysics Data System (ADS)
Tran, L. C.; Werner, F. M.; Solin, S. A.; Gilbertson, Adam; Cohen, L. F.
2013-03-01
Individually addressable optical sensors with dimensions as low as 250nm, fabricated from metal semiconductor hybrid structures (MSH) of AuTi-GaAs Schottky interfaces, display a transition from resistance decreasing with intensity in micron-scale sensors (Extraordinary Optoconductance, EOC) to resistance increasing with intensity in nano-scale sensors (Inverse Extraordinary Optoconductance I-EOC). I-EOC is attributed to a ballistic to diffusive crossover with the introduction of photo-induced carriers and gives rise to resistance changes of up to 9462% in 250nm devices. We characterize the photo-dependence of the effective Schottky barrier in EOC/I-EOC structures by the open circuit voltage and reverse bias resistance. Under illumination by a 5 mW, 632.8 nm HeNe laser, the barrier is negligible and the Ti-GaAs interface becomes Ohmic. Comparing the behavior of two devices, one with leads exposed, another with leads covered by an opaque epoxy, the variation in Voc with the position of the laser can be attributed to a photovoltaic effect of the lead metal and bulk GaAs. The resistance is unaffected by the photovoltaic offset of the leads, as indicated by the radial symmetry of 2-D resistance maps obtained by rastering a laser across EOC/IEOC devices. SAS has a financial interest in PixelEXX, a start-up company whose mission is to market imaging arrays.
2D Time-lapse Seismic Tomography Using An Active Time Constraint (ATC) Approach
We propose a 2D seismic time-lapse inversion approach to image the evolution of seismic velocities over time and space. The forward modeling is based on solving the eikonal equation using a second-order fast marching method. The wave-paths are represented by Fresnel volumes rathe...
2D-2D tunneling field-effect transistors using WSe2/SnSe2 heterostructures
NASA Astrophysics Data System (ADS)
Roy, Tania; Tosun, Mahmut; Hettick, Mark; Ahn, Geun Ho; Hu, Chenming; Javey, Ali
2016-02-01
Two-dimensional materials present a versatile platform for developing steep transistors due to their uniform thickness and sharp band edges. We demonstrate 2D-2D tunneling in a WSe2/SnSe2 van der Waals vertical heterojunction device, where WSe2 is used as the gate controlled p-layer and SnSe2 is the degenerately n-type layer. The van der Waals gap facilitates the regulation of band alignment at the heterojunction, without the necessity of a tunneling barrier. ZrO2 is used as the gate dielectric, allowing the scaling of gate oxide to improve device subthreshold swing. Efficient gate control and clean interfaces yield a subthreshold swing of ˜100 mV/dec for >2 decades of drain current at room temperature, hitherto unobserved in 2D-2D tunneling devices. The subthreshold swing is independent of temperature, which is a clear signature of band-to-band tunneling at the heterojunction. A maximum switching ratio ION/IOFF of 107 is obtained. Negative differential resistance in the forward bias characteristics is observed at 77 K. This work bodes well for the possibilities of two-dimensional materials for the realization of energy-efficient future-generation electronics.
2D FEM Heat Transfer & E&M Field Code
1992-04-02
TOPAZ and TOPAZ2D are two-dimensional implicit finite element computer codes for heat transfer analysis. TOPAZ2D can also be used to solve electrostatic and magnetostatic problems. The programs solve for the steady-state or transient temperature or electrostatic and magnetostatic potential field on two-dimensional planar or axisymmetric geometries. Material properties may be temperature or potential-dependent and either isotropic or orthotropic. A variety of time and temperature-dependent boundary conditions can be specified including temperature, flux, convection, and radiation. By implementing the user subroutine feature, users can model chemical reaction kinetics and allow for any type of functional representation of boundary conditions and internal heat generation. The programs can solve problems of diffuse and specular band radiation in an enclosure coupled with conduction in the material surrounding the enclosure. Additional features include thermal contact resistance across an interface, bulk fluids, phase change, and energy balances.
NASA Astrophysics Data System (ADS)
Sergienko, Olga
2013-04-01
Since Doug MacAyeal's pioneering studies of the ice-stream basal traction optimizations by control methods, inversions for unknown parameters (e.g., basal traction, accumulation patterns, etc) have become a hallmark of the present-day ice-sheet modeling. The common feature of such inversion exercises is a direct relationship between optimized parameters and observations used in the optimization procedure. For instance, in the standard optimization for basal traction by the control method, ice-stream surface velocities constitute the control data. The optimized basal traction parameters explicitly appear in the momentum equations for the ice-stream velocities (compared to the control data). The inversion for basal traction is carried out by minimization of the cost (or objective, misfit) function that includes the momentum equations facilitated by the Lagrange multipliers. Here, we build upon this idea, and demonstrate how to optimize for parameters indirectly related to observed data using a suite of nested constraints (like Russian dolls) with additional sets of Lagrange multipliers in the cost function. This method opens the opportunity to use data from a variety of sources and types (e.g., velocities, radar layers, surface elevation changes, etc.) in the same optimization process.
Hicks, H.R.; Dory, R.A.; Holmes, J.A.
1983-01-01
We illustrate in some detail a 2D inverse-equilibrium solver that was constructed to analyze tokamak configurations and stellarators (the latter in the context of the average method). To ensure that the method is suitable not only to determine equilibria, but also to provide appropriately represented data for existing stability codes, it is important to be able to control the Jacobian, tilde J is identical to delta(R,Z)/delta(rho, theta). The form chosen is tilde J = J/sub 0/(rho)R/sup l/rho where rho is a flux surface label, and l is an integer. The initial implementation is for a fixed conducting-wall boundary, but the technique can be extended to a free-boundary model.
NASA Technical Reports Server (NTRS)
Ostro, Steven J.; Connelly, Robert
1987-01-01
One of the most fundamental physical properties of any asteroid is its shape. Lightcurves provide the only source of shape information for most asteroids. Unfortunately, the functional form of a lightcurve is determined by the viewing/illumination geometry and the asteroid's light scattering characteristics as well as its shape, and in general it is impossible to determine an asteroid's shape from lightcurves. A technique called convex-profile inversion (CPI) that obtains a convex profile, P, from any lightcurve is introduced. If certain ideal conditions are satisfied, then P is an estimator for the asteroid's mean cross section, C, a convex set defined as the average of all cross sections C(z) cut by planes a distance z above the asteroids's equatorial plane. C is therefore a 2-D average of the asteroid's 3-D shape.
Orthotropic Piezoelectricity in 2D Nanocellulose
NASA Astrophysics Data System (ADS)
García, Y.; Ruiz-Blanco, Yasser B.; Marrero-Ponce, Yovani; Sotomayor-Torres, C. M.
2016-10-01
The control of electromechanical responses within bonding regions is essential to face frontier challenges in nanotechnologies, such as molecular electronics and biotechnology. Here, we present Iβ-nanocellulose as a potentially new orthotropic 2D piezoelectric crystal. The predicted in-layer piezoelectricity is originated on a sui-generis hydrogen bonds pattern. Upon this fact and by using a combination of ab-initio and ad-hoc models, we introduce a description of electrical profiles along chemical bonds. Such developments lead to obtain a rationale for modelling the extended piezoelectric effect originated within bond scales. The order of magnitude estimated for the 2D Iβ-nanocellulose piezoelectric response, ~pm V‑1, ranks this material at the level of currently used piezoelectric energy generators and new artificial 2D designs. Such finding would be crucial for developing alternative materials to drive emerging nanotechnologies.
Orthotropic Piezoelectricity in 2D Nanocellulose
García, Y.; Ruiz-Blanco, Yasser B.; Marrero-Ponce, Yovani; Sotomayor-Torres, C. M.
2016-01-01
The control of electromechanical responses within bonding regions is essential to face frontier challenges in nanotechnologies, such as molecular electronics and biotechnology. Here, we present Iβ-nanocellulose as a potentially new orthotropic 2D piezoelectric crystal. The predicted in-layer piezoelectricity is originated on a sui-generis hydrogen bonds pattern. Upon this fact and by using a combination of ab-initio and ad-hoc models, we introduce a description of electrical profiles along chemical bonds. Such developments lead to obtain a rationale for modelling the extended piezoelectric effect originated within bond scales. The order of magnitude estimated for the 2D Iβ-nanocellulose piezoelectric response, ~pm V−1, ranks this material at the level of currently used piezoelectric energy generators and new artificial 2D designs. Such finding would be crucial for developing alternative materials to drive emerging nanotechnologies. PMID:27708364
Orthotropic Piezoelectricity in 2D Nanocellulose.
García, Y; Ruiz-Blanco, Yasser B; Marrero-Ponce, Yovani; Sotomayor-Torres, C M
2016-10-06
The control of electromechanical responses within bonding regions is essential to face frontier challenges in nanotechnologies, such as molecular electronics and biotechnology. Here, we present Iβ-nanocellulose as a potentially new orthotropic 2D piezoelectric crystal. The predicted in-layer piezoelectricity is originated on a sui-generis hydrogen bonds pattern. Upon this fact and by using a combination of ab-initio and ad-hoc models, we introduce a description of electrical profiles along chemical bonds. Such developments lead to obtain a rationale for modelling the extended piezoelectric effect originated within bond scales. The order of magnitude estimated for the 2D Iβ-nanocellulose piezoelectric response, ~pm V(-1), ranks this material at the level of currently used piezoelectric energy generators and new artificial 2D designs. Such finding would be crucial for developing alternative materials to drive emerging nanotechnologies.
2D microwave imaging reflectometer electronics
Spear, A. G.; Domier, C. W. Hu, X.; Muscatello, C. M.; Ren, X.; Luhmann, N. C.; Tobias, B. J.
2014-11-15
A 2D microwave imaging reflectometer system has been developed to visualize electron density fluctuations on the DIII-D tokamak. Simultaneously illuminated at four probe frequencies, large aperture optics image reflections from four density-dependent cutoff surfaces in the plasma over an extended region of the DIII-D plasma. Localized density fluctuations in the vicinity of the plasma cutoff surfaces modulate the plasma reflections, yielding a 2D image of electron density fluctuations. Details are presented of the receiver down conversion electronics that generate the in-phase (I) and quadrature (Q) reflectometer signals from which 2D density fluctuation data are obtained. Also presented are details on the control system and backplane used to manage the electronics as well as an introduction to the computer based control program.
Large Area Synthesis of 2D Materials
NASA Astrophysics Data System (ADS)
Vogel, Eric
Transition metal dichalcogenides (TMDs) have generated significant interest for numerous applications including sensors, flexible electronics, heterostructures and optoelectronics due to their interesting, thickness-dependent properties. Despite recent progress, the synthesis of high-quality and highly uniform TMDs on a large scale is still a challenge. In this talk, synthesis routes for WSe2 and MoS2 that achieve monolayer thickness uniformity across large area substrates with electrical properties equivalent to geological crystals will be described. Controlled doping of 2D semiconductors is also critically required. However, methods established for conventional semiconductors, such as ion implantation, are not easily applicable to 2D materials because of their atomically thin structure. Redox-active molecular dopants will be demonstrated which provide large changes in carrier density and workfunction through the choice of dopant, treatment time, and the solution concentration. Finally, several applications of these large-area, uniform 2D materials will be described including heterostructures, biosensors and strain sensors.
2D microwave imaging reflectometer electronics.
Spear, A G; Domier, C W; Hu, X; Muscatello, C M; Ren, X; Tobias, B J; Luhmann, N C
2014-11-01
A 2D microwave imaging reflectometer system has been developed to visualize electron density fluctuations on the DIII-D tokamak. Simultaneously illuminated at four probe frequencies, large aperture optics image reflections from four density-dependent cutoff surfaces in the plasma over an extended region of the DIII-D plasma. Localized density fluctuations in the vicinity of the plasma cutoff surfaces modulate the plasma reflections, yielding a 2D image of electron density fluctuations. Details are presented of the receiver down conversion electronics that generate the in-phase (I) and quadrature (Q) reflectometer signals from which 2D density fluctuation data are obtained. Also presented are details on the control system and backplane used to manage the electronics as well as an introduction to the computer based control program.
Assessing 2D electrophoretic mobility spectroscopy (2D MOSY) for analytical applications.
Fang, Yuan; Yushmanov, Pavel V; Furó, István
2016-12-08
Electrophoretic displacement of charged entity phase modulates the spectrum acquired in electrophoretic NMR experiments, and this modulation can be presented via 2D FT as 2D mobility spectroscopy (MOSY) spectra. We compare in various mixed solutions the chemical selectivity provided by 2D MOSY spectra with that provided by 2D diffusion-ordered spectroscopy (DOSY) spectra and demonstrate, under the conditions explored, a superior performance of the former method. 2D MOSY compares also favourably with closely related LC-NMR methods. The shape of 2D MOSY spectra in complex mixtures is strongly modulated by the pH of the sample, a feature that has potential for areas such as in drug discovery and metabolomics. Copyright © 2016 The Authors. Magnetic Resonance in Chemistry published by John Wiley & Sons Ltd. StartCopTextCopyright © 2016 The Authors. Magnetic Resonance in Chemistry published by John Wiley & Sons Ltd.
Calculating tissue shear modulus and pressure by 2D Log-Elastographic methods
McLaughlin, Joyce R; Zhang, Ning; Manduca, Armando
2010-01-01
Shear modulus imaging, often called elastography, enables detection and characterization of tissue abnormalities. In this paper the data is two displacement components obtained from successive MR or ultrasound data sets acquired while the tissue is excited mechanically. A 2D plane strain elastic model is assumed to govern the 2D displacement, u. The shear modulus, μ, is unknown and whether or not the first Lamé parameter, λ, is known the pressure p = λ∇ · u which is present in the plane strain model cannot be measured and is unreliably computed from measured data and can be shown to be an order one quantity in the units kPa. So here we present a 2D Log-Elastographic inverse algorithm that: (1) simultaneously reconstructs the shear modulus, μ, and p, which together satisfy a first order partial differential equation system, with the goal of imaging μ; (2) controls potential exponential growth in the numerical error; and (3) reliably reconstructs the quantity p in the inverse algorithm as compared to the same quantity computed with a forward algorithm. This work generalizes the Log-Elastographic algorithm in [20] which uses one displacement component, is derived assuming the component satisfies the wave equation, and is tested on synthetic data computed with the wave equation model. The 2D Log-Elastographic algorithm is tested on 2D synthetic data and 2D in-vivo data from Mayo Clinic. We also exhibit examples to show that the 2D Log-Elastographic algorithm improves the quality of the recovered images as compared to the Log-Elastographic and Direct Inversion algorithms. PMID:21822349
Fast, accurate 2D-MR relaxation exchange spectroscopy (REXSY): Beyond compressed sensing
NASA Astrophysics Data System (ADS)
Bai, Ruiliang; Benjamini, Dan; Cheng, Jian; Basser, Peter J.
2016-10-01
Previously, we showed that compressive or compressed sensing (CS) can be used to reduce significantly the data required to obtain 2D-NMR relaxation and diffusion spectra when they are sparse or well localized. In some cases, an order of magnitude fewer uniformly sampled data were required to reconstruct 2D-MR spectra of comparable quality. Nonetheless, this acceleration may still not be sufficient to make 2D-MR spectroscopy practicable for many important applications, such as studying time-varying exchange processes in swelling gels or drying paints, in living tissue in response to various biological or biochemical challenges, and particularly for in vivo MRI applications. A recently introduced framework, marginal distributions constrained optimization (MADCO), tremendously accelerates such 2D acquisitions by using a priori obtained 1D marginal distribution as powerful constraints when 2D spectra are reconstructed. Here we exploit one important intrinsic property of the 2D-MR relaxation exchange spectra: the fact that the 1D marginal distributions of each 2D-MR relaxation exchange spectrum in both dimensions are equal and can be rapidly estimated from a single Carr-Purcell-Meiboom-Gill (CPMG) or inversion recovery prepared CPMG measurement. We extend the MADCO framework by further proposing to use the 1D marginal distributions to inform the subsequent 2D data-sampling scheme, concentrating measurements where spectral peaks are present and reducing them where they are not. In this way we achieve compression or acceleration that is an order of magnitude greater than that in our previous CS method while providing data in reconstructed 2D-MR spectral maps of comparable quality, demonstrated using several simulated and real 2D T2 - T2 experimental data. This method, which can be called "informed compressed sensing," is extendable to other 2D- and even ND-MR exchange spectroscopy.
2D Distributed Sensing Via TDR
2007-11-02
plate VEGF CompositeSensor Experimental Setup Air 279 mm 61 78 VARTM profile: slope RTM profile: rectangle 22 1 Jul 2003© 2003 University of Delaware...2003 University of Delaware All rights reserved Vision: Non-contact 2D sensing ü VARTM setup constructed within TL can be sensed by its EM field: 2D...300.0 mm/ns. 1 2 1 Jul 2003© 2003 University of Delaware All rights reserved Model Validation “ RTM Flow” TDR Response to 139 mm VEGC
Inkjet printing of 2D layered materials.
Li, Jiantong; Lemme, Max C; Östling, Mikael
2014-11-10
Inkjet printing of 2D layered materials, such as graphene and MoS2, has attracted great interests for emerging electronics. However, incompatible rheology, low concentration, severe aggregation and toxicity of solvents constitute critical challenges which hamper the manufacturing efficiency and product quality. Here, we introduce a simple and general technology concept (distillation-assisted solvent exchange) to efficiently overcome these challenges. By implementing the concept, we have demonstrated excellent jetting performance, ideal printing patterns and a variety of promising applications for inkjet printing of 2D layered materials.
NASA Astrophysics Data System (ADS)
Revil, A.
2015-12-01
Geological expertise and petrophysical relationships can be brought together to provide prior information while inverting multiple geophysical datasets. The merging of such information can result in more realistic solution in the distribution of the model parameters, reducing ipse facto the non-uniqueness of the inverse problem. We consider two level of heterogeneities: facies, described by facies boundaries and heteroegenities inside each facies determined by a correlogram. In this presentation, we pose the geophysical inverse problem in terms of Gaussian random fields with mean functions controlled by petrophysical relationships and covariance functions controlled by a prior geological cross-section, including the definition of spatial boundaries for the geological facies. The petrophysical relationship problem is formulated as a regression problem upon each facies. The inversion of the geophysical data is performed in a Bayesian framework. We demonstrate the usefulness of this strategy using a first synthetic case for which we perform a joint inversion of gravity and galvanometric resistivity data with the stations located at the ground surface. The joint inversion is used to recover the density and resistivity distributions of the subsurface. In a second step, we consider the possibility that the facies boundaries are deformable and their shapes are inverted as well. We use the level set approach to perform such deformation preserving prior topological properties of the facies throughout the inversion. With the help of prior facies petrophysical relationships and topological characteristic of each facies, we make posterior inference about multiple geophysical tomograms based on their corresponding geophysical data misfits. The method is applied to a second synthetic case showing that we can recover the heterogeneities inside the facies, the mean values for the petrophysical properties, and, to some extent, the facies boundaries using the 2D joint inversion of
Oxidation of Survival Factor MEF2D in Neuronal Death and Parkinson's Disease
Gao, Li; She, Hua; Li, Wenming; Zeng, Jin; Zhu, Jinqiu; Jones, Dean P.
2014-01-01
Abstract Aims: Dysfunction of myocyte enhancer factor 2D (MEF2D), a key survival protein and transcription factor, underlies the pathogenic loss of dopaminergic (DA) neurons in Parkinson's disease (PD). Both genetic factors and neurotoxins associated with PD impair MEF2D function in vitro and in animal models of PD. We investigated whether distinct stress conditions target MEF2D via converging mechanisms. Results: We showed that exposure of a DA neuronal cell line to 6-hyroxydopamine (6-OHDA), which causes PD in animals models, led to direct oxidative modifications of MEF2D. Oxidized MEF2D bound to heat-shock cognate protein 70 kDa, the key regulator for chaperone-mediated autophagy (CMA), at a higher affinity. Oxidative stress also increased the level of lysosomal-associated membrane protein 2A (LAMP2A), the rate-limiting receptor for CMA substrate flux, and stimulated CMA activity. These changes resulted in accelerated degradation of MEF2D. Importantly, 6-OHDA induced MEF2D oxidation and increased LAMP2A in the substantia nigra pars compacta region of the mouse brain. Consistently, the levels of oxidized MEF2D were much higher in postmortem PD brains compared with the controls. Functionally, reducing the levels of either MEF2D or LAMP2A exacerbated 6-OHDA-induced death of the DA neuronal cell line. Expression of an MEF2D mutant that is resistant to oxidative modification protected cells from 6-OHDA-induced death. Innovation: This study showed that oxidization of survival protein MEF2D is one of the pathogenic mechanisms involved in oxidative stress-induced DA neuronal death. Conclusion: Oxidation of survival factor MEF2D inhibits its function, underlies oxidative stress-induced neurotoxicity, and may be a part of the PD pathogenic process. Antioxid. Redox Signal. 20, 2936–2948. PMID:24219011
Inverse heat conduction problems
NASA Astrophysics Data System (ADS)
Orlande, Helcio Rangel Barreto
We present the solution of the following inverse problems: (1) Inverse Problem of Estimating Interface Conductance Between Periodically Contacting Surfaces; (2) Inverse Problem of Estimating Interface Conductance During Solidification via Conjugate Gradient Method; (3) Determination of the Reaction Function in a Reaction-Diffusion Parabolic Problem; and (4) Simultaneous Estimation of Thermal Diffusivity and Relaxation Time with Hyperbolic Heat Conduction Model. Also, we present the solution of a direct problem entitled: Transient Thermal Constriction Resistance in a Finite Heat Flux Tube. The Conjugate Gradient Method with Adjoint Equation was used in chapters 1-3. The more general function estimation approach was treated in these chapters. In chapter 1, we solve the inverse problem of estimating the timewise variation of the interface conductance between periodically contacting solids, under quasi-steady-state conditions. The present method is found to be more accurate than the B-Spline approach for situations involving small periods, which are the most difficult on which to perform the inverse analysis. In chapter 2, we estimate the timewise variation of the interface conductance between casting and mold during the solidification of aluminum. The experimental apparatus used in this study is described. In chapter 3, we present the estimation of the reaction function in a one dimensional parabolic problem. A comparison of the present function estimation approach with the parameter estimation technique, wing B-Splines to approximate the reaction function, revealed that the use of function estimation reduces the computer time requirements. In chapter 4 we present a finite difference solution for the transient constriction resistance in a cylinder of finite length with a circular contact surface. A numerical grid generation scheme was used to concentrate grid points in the regions of high temperature gradients in order to reduce discretization errors. In chapter 6, we
Parallel Stitching of 2D Materials.
Ling, Xi; Lin, Yuxuan; Ma, Qiong; Wang, Ziqiang; Song, Yi; Yu, Lili; Huang, Shengxi; Fang, Wenjing; Zhang, Xu; Hsu, Allen L; Bie, Yaqing; Lee, Yi-Hsien; Zhu, Yimei; Wu, Lijun; Li, Ju; Jarillo-Herrero, Pablo; Dresselhaus, Mildred; Palacios, Tomás; Kong, Jing
2016-03-23
Diverse parallel stitched 2D heterostructures, including metal-semiconductor, semiconductor-semiconductor, and insulator-semiconductor, are synthesized directly through selective "sowing" of aromatic molecules as the seeds in the chemical vapor deposition (CVD) method. The methodology enables the large-scale fabrication of lateral heterostructures, which offers tremendous potential for its application in integrated circuits.
Beckett, Phil
2012-01-01
The technique of two-dimensional (2D) gel electrophoresis is a powerful tool for separating complex mixtures of proteins, but since its inception in the mid 1970s, it acquired the stigma of being a very difficult application to master and was generally used to its best effect by experts. The introduction of commercially available immobilized pH gradients in the early 1990s provided enhanced reproducibility and easier protocols, leading to a pronounced increase in popularity of the technique. However gel-to-gel variation was still difficult to control without the use of technical replicates. In the mid 1990s (at the same time as the birth of "proteomics"), the concept of multiplexing fluorescently labeled proteins for 2D gel separation was realized by Jon Minden's group and has led to the ability to design experiments to virtually eliminate gel-to-gel variation, resulting in biological replicates being used for statistical analysis with the ability to detect very small changes in relative protein abundance. This technology is referred to as 2D difference gel electrophoresis (2D DIGE).
Parallel stitching of 2D materials
Ling, Xi; Wu, Lijun; Lin, Yuxuan; ...
2016-01-27
Diverse parallel stitched 2D heterostructures, including metal–semiconductor, semiconductor–semiconductor, and insulator–semiconductor, are synthesized directly through selective “sowing” of aromatic molecules as the seeds in the chemical vapor deposition (CVD) method. Lastly, the methodology enables the large-scale fabrication of lateral heterostructures, which offers tremendous potential for its application in integrated circuits.
Comparison of different sets of array configurations for multichannel 2D ERT acquisition
NASA Astrophysics Data System (ADS)
Martorana, R.; Capizzi, P.; D'Alessandro, A.; Luzio, D.
2017-02-01
Traditional electrode arrays such Wenner-Schlumberger or dipole-dipole are still widely used thanks to their well-known properties but the array configurations are generally not optimized for multi-channel resistivity measures. Synthetic datasets relating to four different arrays, dipole-dipole (DD), pole-dipole (PD), Wenner-Schlumberger (WS) and a modified version of multiple gradient (MG), have been made for a systematic comparison between 2D resistivity models and their inverted images. Different sets of array configurations generated from simple combinations of geometric parameters (potential dipole lengths and dipole separation factors) were tested with synthetic and field data sets, even considering the influence of errors and the acquisition velocity. The purpose is to establish array configurations capable to provide reliable results but, at the same time, not involving excessive survey costs, even linked to the acquiring time and therefore to the number of current dipoles used. For DD, PD and WS arrays a progression of different datasets were considered increasing the number of current dipoles trying to get about the same amount of measures. A multi-coverage MG array configuration is proposed by increasing the lateral coverage and so the number of current dipoles. Noise simulating errors both on the electrode positions and on the electric potential was added. The array configurations have been tested on field data acquired in the landfill site of Bellolampo (Palermo, Italy), to detect and locate the leachate plumes and to identify the HDPE bottom of the landfill. The inversion results were compared using a quantitative analysis of data misfit, relative model resolution and model misfit. The results show that the trends of the first two parameters are linked on the array configuration and that a cumulative analysis of these parameters can help to choose the best array configuration in order to obtain a good resolution and reliability of a survey, according
Microwave Imaging with Infrared 2-D Lock-in Amplifier
NASA Astrophysics Data System (ADS)
Chiyo, Noritaka; Arai, Mizuki; Tanaka, Yasuhiro; Nishikata, Atsuhiro; Maeno, Takashi
We have developed a 3-D electromagnetic field measurement system using 2-D lock-in amplifier. This system uses an amplitude modulated electromagnetic wave source to heat a resistive screen. A very small change of temperature on a screen illuminated with the modulated electromagnetic wave is measured using an infrared thermograph camera. In this paper, we attempted to apply our system to microwave imaging. By placing conductor patches in front of the resistive screen and illuminating with microwave, the shape of each conductor was clearly observed as the temperature difference image of the screen. In this way, the conductor pattern inside the non-contact type IC card could be visualized. Moreover, we could observe the temperature difference image reflecting the shape of a Konnyaku (a gelatinous food made from devil's-tonge starch) or a dried fishbone, both as non-conducting material resembling human body. These results proved that our method is applicable to microwave see-through imaging.
Screening and transport in 2D semiconductor systems at low temperatures.
Das Sarma, S; Hwang, E H
2015-11-17
Low temperature carrier transport properties in 2D semiconductor systems can be theoretically well-understood within RPA-Boltzmann theory as being limited by scattering from screened Coulomb disorder arising from random quenched charged impurities in the environment. In this work, we derive a number of analytical formula, supported by realistic numerical calculations, for the relevant density, mobility, and temperature range where 2D transport should manifest strong intrinsic (i.e., arising purely from electronic effects) metallic temperature dependence in different semiconductor materials arising entirely from the 2D screening properties, thus providing an explanation for why the strong temperature dependence of the 2D resistivity can only be observed in high-quality and low-disorder 2D samples and also why some high-quality 2D materials manifest much weaker metallicity than other materials. We also discuss effects of interaction and disorder on the 2D screening properties in this context as well as compare 2D and 3D screening functions to comment why such a strong intrinsic temperature dependence arising from screening cannot occur in 3D metallic carrier transport. Experimentally verifiable predictions are made about the quantitative magnitude of the maximum possible low-temperature metallicity in 2D systems and the scaling behavior of the temperature scale controlling the quantum to classical crossover.
Screening and transport in 2D semiconductor systems at low temperatures
Das Sarma, S.; Hwang, E. H.
2015-01-01
Low temperature carrier transport properties in 2D semiconductor systems can be theoretically well-understood within RPA-Boltzmann theory as being limited by scattering from screened Coulomb disorder arising from random quenched charged impurities in the environment. In this work, we derive a number of analytical formula, supported by realistic numerical calculations, for the relevant density, mobility, and temperature range where 2D transport should manifest strong intrinsic (i.e., arising purely from electronic effects) metallic temperature dependence in different semiconductor materials arising entirely from the 2D screening properties, thus providing an explanation for why the strong temperature dependence of the 2D resistivity can only be observed in high-quality and low-disorder 2D samples and also why some high-quality 2D materials manifest much weaker metallicity than other materials. We also discuss effects of interaction and disorder on the 2D screening properties in this context as well as compare 2D and 3D screening functions to comment why such a strong intrinsic temperature dependence arising from screening cannot occur in 3D metallic carrier transport. Experimentally verifiable predictions are made about the quantitative magnitude of the maximum possible low-temperature metallicity in 2D systems and the scaling behavior of the temperature scale controlling the quantum to classical crossover. PMID:26572738
Application of 2D Non-Graphene Materials and 2D Oxide Nanostructures for Biosensing Technology
Shavanova, Kateryna; Bakakina, Yulia; Burkova, Inna; Shtepliuk, Ivan; Viter, Roman; Ubelis, Arnolds; Beni, Valerio; Starodub, Nickolaj; Yakimova, Rositsa; Khranovskyy, Volodymyr
2016-01-01
The discovery of graphene and its unique properties has inspired researchers to try to invent other two-dimensional (2D) materials. After considerable research effort, a distinct “beyond graphene” domain has been established, comprising the library of non-graphene 2D materials. It is significant that some 2D non-graphene materials possess solid advantages over their predecessor, such as having a direct band gap, and therefore are highly promising for a number of applications. These applications are not limited to nano- and opto-electronics, but have a strong potential in biosensing technologies, as one example. However, since most of the 2D non-graphene materials have been newly discovered, most of the research efforts are concentrated on material synthesis and the investigation of the properties of the material. Applications of 2D non-graphene materials are still at the embryonic stage, and the integration of 2D non-graphene materials into devices is scarcely reported. However, in recent years, numerous reports have blossomed about 2D material-based biosensors, evidencing the growing potential of 2D non-graphene materials for biosensing applications. This review highlights the recent progress in research on the potential of using 2D non-graphene materials and similar oxide nanostructures for different types of biosensors (optical and electrochemical). A wide range of biological targets, such as glucose, dopamine, cortisol, DNA, IgG, bisphenol, ascorbic acid, cytochrome and estradiol, has been reported to be successfully detected by biosensors with transducers made of 2D non-graphene materials. PMID:26861346
Application of 2D Non-Graphene Materials and 2D Oxide Nanostructures for Biosensing Technology.
Shavanova, Kateryna; Bakakina, Yulia; Burkova, Inna; Shtepliuk, Ivan; Viter, Roman; Ubelis, Arnolds; Beni, Valerio; Starodub, Nickolaj; Yakimova, Rositsa; Khranovskyy, Volodymyr
2016-02-06
The discovery of graphene and its unique properties has inspired researchers to try to invent other two-dimensional (2D) materials. After considerable research effort, a distinct "beyond graphene" domain has been established, comprising the library of non-graphene 2D materials. It is significant that some 2D non-graphene materials possess solid advantages over their predecessor, such as having a direct band gap, and therefore are highly promising for a number of applications. These applications are not limited to nano- and opto-electronics, but have a strong potential in biosensing technologies, as one example. However, since most of the 2D non-graphene materials have been newly discovered, most of the research efforts are concentrated on material synthesis and the investigation of the properties of the material. Applications of 2D non-graphene materials are still at the embryonic stage, and the integration of 2D non-graphene materials into devices is scarcely reported. However, in recent years, numerous reports have blossomed about 2D material-based biosensors, evidencing the growing potential of 2D non-graphene materials for biosensing applications. This review highlights the recent progress in research on the potential of using 2D non-graphene materials and similar oxide nanostructures for different types of biosensors (optical and electrochemical). A wide range of biological targets, such as glucose, dopamine, cortisol, DNA, IgG, bisphenol, ascorbic acid, cytochrome and estradiol, has been reported to be successfully detected by biosensors with transducers made of 2D non-graphene materials.
Höfer, Peter; Schosser, Alexandra; Calati, Raffaella; Serretti, Alessandro; Massat, Isabelle; Kocabas, Neslihan Aygun; Konstantinidis, Anastasios; Linotte, Sylvie; Mendlewicz, Julien; Souery, Daniel; Zohar, Joseph; Juven-Wetzler, Alzbeta; Montgomery, Stuart; Kasper, Siegfried
2013-08-01
Recently published data have reported associations between cytochrome P450 metabolizer status and suicidality. The aim of our study was to investigate the role of genetic polymorphisms of the cytochrome P450 genes on suicide risk and/or a personal history of suicide attempts. Two hundred forty-three major depressive disorder patients were collected in the context of a European multicentre resistant depression study and treated with antidepressants at adequate doses for at least 4 weeks. Suicidality was assessed using the Mini International Neuropsychiatric Interview and the Hamilton Rating Scale for Depression (HAM-D). Treatment response was defined as HAM-D ≤ 17 and remission as HAM-D ≤ 7 after 4 weeks of treatment with antidepressants at adequate dose. Genotyping was performed for all relevant variations of the CYP1A2 gene (*1A, *1F, *1C, *1 J, *1 K), the CYP2C9 gene (*2, *3), the CYP2C19 gene (*2, *17) and the CYP2D6 gene (*3, *4, *5, *6, *9, *19, *XN). No association between both suicide risk and personal history of suicide attempts, and the above mentioned metabolic profiles were found after multiple testing corrections. In conclusion, the investigated cytochrome gene polymorphisms do not seem to be associated with suicide risk and/or a personal history of suicide attempts, though methodological and sample size limitations do not allow definitive conclusions.
NASA Astrophysics Data System (ADS)
Atzemoglou, A.; Tsourlos, P.
2012-02-01
A large-scale vertical electrical sounding (VES) survey was applied at the basin of Sarantaporon, Elassona in order to study the tectonic and hydrogeological setting of the area. A large number of VES was obtained on a near-regular grid and data were initially processed with 1D inversion algorithm. Since some of the dense measured soundings were collinear, it was possible to combine 1D sounding data and produce 2D data sets which were interpreted using a fully 2D inversion algorithm. 2D geoelectrical models were in very good agreement with the existing drilling information of the area. 2D interpretation results were combined to produce pseudo-3D geoelectrical images of the subsurface. Resulting geoelectrical interpretations are in very good agreement with the existing geological information and reveal a relatively detailed picture of the basin's lithology. Further, the results allowed us to obtain new, and verify existing, structural information regarding the studied area. Overall, it is concluded that 2D interpretation of 1D VES measurements can produce improved subsurface geophysical images and presents a potential useful tool for larger scale geological investigations especially in the case of reprocessing existing VES data sets.
Compatible embedding for 2D shape animation.
Baxter, William V; Barla, Pascal; Anjyo, Ken-Ichi
2009-01-01
We present new algorithms for the compatible embedding of 2D shapes. Such embeddings offer a convenient way to interpolate shapes having complex, detailed features. Compared to existing techniques, our approach requires less user input, and is faster, more robust, and simpler to implement, making it ideal for interactive use in practical applications. Our new approach consists of three parts. First, our boundary matching algorithm locates salient features using the perceptually motivated principles of scale-space and uses these as automatic correspondences to guide an elastic curve matching algorithm. Second, we simplify boundaries while maintaining their parametric correspondence and the embedding of the original shapes. Finally, we extend the mapping to shapes' interiors via a new compatible triangulation algorithm. The combination of our algorithms allows us to demonstrate 2D shape interpolation with instant feedback. The proposed algorithms exhibit a combination of simplicity, speed, and accuracy that has not been achieved in previous work.
Schottky diodes from 2D germanane
NASA Astrophysics Data System (ADS)
Sahoo, Nanda Gopal; Esteves, Richard J.; Punetha, Vinay Deep; Pestov, Dmitry; Arachchige, Indika U.; McLeskey, James T.
2016-07-01
We report on the fabrication and characterization of a Schottky diode made using 2D germanane (hydrogenated germanene). When compared to germanium, the 2D structure has higher electron mobility, an optimal band-gap, and exceptional stability making germanane an outstanding candidate for a variety of opto-electronic devices. One-atom-thick sheets of hydrogenated puckered germanium atoms have been synthesized from a CaGe2 framework via intercalation and characterized by XRD, Raman, and FTIR techniques. The material was then used to fabricate Schottky diodes by suspending the germanane in benzonitrile and drop-casting it onto interdigitated metal electrodes. The devices demonstrate significant rectifying behavior and the outstanding potential of this material.
Extrinsic Cation Selectivity of 2D Membranes
2017-01-01
From a systematic study of the concentration driven diffusion of positive and negative ions across porous 2D membranes of graphene and hexagonal boron nitride (h-BN), we prove their cation selectivity. Using the current–voltage characteristics of graphene and h-BN monolayers separating reservoirs of different salt concentrations, we calculate the reversal potential as a measure of selectivity. We tune the Debye screening length by exchanging the salt concentrations and demonstrate that negative surface charge gives rise to cation selectivity. Surprisingly, h-BN and graphene membranes show similar characteristics, strongly suggesting a common origin of selectivity in aqueous solvents. For the first time, we demonstrate that the cation flux can be increased by using ozone to create additional pores in graphene while maintaining excellent selectivity. We discuss opportunities to exploit our scalable method to use 2D membranes for applications including osmotic power conversion. PMID:28157333
Static & Dynamic Response of 2D Solids
Lin, Jerry
1996-07-15
NIKE2D is an implicit finite-element code for analyzing the finite deformation, static and dynamic response of two-dimensional, axisymmetric, plane strain, and plane stress solids. The code is fully vectorized and available on several computing platforms. A number of material models are incorporated to simulate a wide range of material behavior including elasto-placicity, anisotropy, creep, thermal effects, and rate dependence. Slideline algorithms model gaps and sliding along material interfaces, including interface friction, penetration and single surface contact. Interactive-graphics and rezoning is included for analyses with large mesh distortions. In addition to quasi-Newton and arc-length procedures, adaptive algorithms can be defined to solve the implicit equations using the solution language ISLAND. Each of these capabilities and more make NIKE2D a robust analysis tool.
Explicit 2-D Hydrodynamic FEM Program
Lin, Jerry
1996-08-07
DYNA2D* is a vectorized, explicit, two-dimensional, axisymmetric and plane strain finite element program for analyzing the large deformation dynamic and hydrodynamic response of inelastic solids. DYNA2D* contains 13 material models and 9 equations of state (EOS) to cover a wide range of material behavior. The material models implemented in all machine versions are: elastic, orthotropic elastic, kinematic/isotropic elastic plasticity, thermoelastoplastic, soil and crushable foam, linear viscoelastic, rubber, high explosive burn, isotropic elastic-plastic, temperature-dependent elastic-plastic. The isotropic and temperature-dependent elastic-plastic models determine only the deviatoric stresses. Pressure is determined by one of 9 equations of state including linear polynomial, JWL high explosive, Sack Tuesday high explosive, Gruneisen, ratio of polynomials, linear polynomial with energy deposition, ignition and growth of reaction in HE, tabulated compaction, and tabulated.
Intersections, ideals, and inversion
Vasco, D.W.
1998-10-01
Techniques from computational algebra provide a framework for treating large classes of inverse problems. In particular, the discretization of many types of integral equations and of partial differential equations with undetermined coefficients lead to systems of polynomial equations. The structure of the solution set of such equations may be examined using algebraic techniques.. For example, the existence and dimensionality of the solution set may be determined. Furthermore, it is possible to bound the total number of solutions. The approach is illustrated by a numerical application to the inverse problem associated with the Helmholtz equation. The algebraic methods are used in the inversion of a set of transverse electric (TE) mode magnetotelluric data from Antarctica. The existence of solutions is demonstrated and the number of solutions is found to be finite, bounded from above at 50. The best fitting structure is dominantly onedimensional with a low crustal resistivity of about 2 ohm-m. Such a low value is compatible with studies suggesting lower surface wave velocities than found in typical stable cratons.
Quasiparticle interference in unconventional 2D systems
NASA Astrophysics Data System (ADS)
Chen, Lan; Cheng, Peng; Wu, Kehui
2017-03-01
At present, research of 2D systems mainly focuses on two kinds of materials: graphene-like materials and transition-metal dichalcogenides (TMDs). Both of them host unconventional 2D electronic properties: pseudospin and the associated chirality of electrons in graphene-like materials, and spin-valley-coupled electronic structures in the TMDs. These exotic electronic properties have attracted tremendous interest for possible applications in nanodevices in the future. Investigation on the quasiparticle interference (QPI) in 2D systems is an effective way to uncover these properties. In this review, we will begin with a brief introduction to 2D systems, including their atomic structures and electronic bands. Then, we will discuss the formation of Friedel oscillation due to QPI in constant energy contours of electron bands, and show the basic concept of Fourier-transform scanning tunneling microscopy/spectroscopy (FT-STM/STS), which can resolve Friedel oscillation patterns in real space and consequently obtain the QPI patterns in reciprocal space. In the next two parts, we will summarize some pivotal results in the investigation of QPI in graphene and silicene, in which systems the low-energy quasiparticles are described by the massless Dirac equation. The FT-STM experiments show there are two different interference channels (intervalley and intravalley scattering) and backscattering suppression, which associate with the Dirac cones and the chirality of quasiparticles. The monolayer and bilayer graphene on different substrates (SiC and metal surfaces), and the monolayer and multilayer silicene on a Ag(1 1 1) surface will be addressed. The fifth part will introduce the FT-STM research on QPI in TMDs (monolayer and bilayer of WSe2), which allow us to infer the spin texture of both conduction and valence bands, and present spin-valley coupling by tracking allowed and forbidden scattering channels.
Compact 2-D graphical representation of DNA
NASA Astrophysics Data System (ADS)
Randić, Milan; Vračko, Marjan; Zupan, Jure; Novič, Marjana
2003-05-01
We present a novel 2-D graphical representation for DNA sequences which has an important advantage over the existing graphical representations of DNA in being very compact. It is based on: (1) use of binary labels for the four nucleic acid bases, and (2) use of the 'worm' curve as template on which binary codes are placed. The approach is illustrated on DNA sequences of the first exon of human β-globin and gorilla β-globin.
2D Metals by Repeated Size Reduction.
Liu, Hanwen; Tang, Hao; Fang, Minghao; Si, Wenjie; Zhang, Qinghua; Huang, Zhaohui; Gu, Lin; Pan, Wei; Yao, Jie; Nan, Cewen; Wu, Hui
2016-10-01
A general and convenient strategy for manufacturing freestanding metal nanolayers is developed on large scale. By the simple process of repeatedly folding and calendering stacked metal sheets followed by chemical etching, free-standing 2D metal (e.g., Ag, Au, Fe, Cu, and Ni) nanosheets are obtained with thicknesses as small as 1 nm and with sizes of the order of several micrometers.
Realistic and efficient 2D crack simulation
NASA Astrophysics Data System (ADS)
Yadegar, Jacob; Liu, Xiaoqing; Singh, Abhishek
2010-04-01
Although numerical algorithms for 2D crack simulation have been studied in Modeling and Simulation (M&S) and computer graphics for decades, realism and computational efficiency are still major challenges. In this paper, we introduce a high-fidelity, scalable, adaptive and efficient/runtime 2D crack/fracture simulation system by applying the mathematically elegant Peano-Cesaro triangular meshing/remeshing technique to model the generation of shards/fragments. The recursive fractal sweep associated with the Peano-Cesaro triangulation provides efficient local multi-resolution refinement to any level-of-detail. The generated binary decomposition tree also provides efficient neighbor retrieval mechanism used for mesh element splitting and merging with minimal memory requirements essential for realistic 2D fragment formation. Upon load impact/contact/penetration, a number of factors including impact angle, impact energy, and material properties are all taken into account to produce the criteria of crack initialization, propagation, and termination leading to realistic fractal-like rubble/fragments formation. The aforementioned parameters are used as variables of probabilistic models of cracks/shards formation, making the proposed solution highly adaptive by allowing machine learning mechanisms learn the optimal values for the variables/parameters based on prior benchmark data generated by off-line physics based simulation solutions that produce accurate fractures/shards though at highly non-real time paste. Crack/fracture simulation has been conducted on various load impacts with different initial locations at various impulse scales. The simulation results demonstrate that the proposed system has the capability to realistically and efficiently simulate 2D crack phenomena (such as window shattering and shards generation) with diverse potentials in military and civil M&S applications such as training and mission planning.
Engineering light outcoupling in 2D materials.
Lien, Der-Hsien; Kang, Jeong Seuk; Amani, Matin; Chen, Kevin; Tosun, Mahmut; Wang, Hsin-Ping; Roy, Tania; Eggleston, Michael S; Wu, Ming C; Dubey, Madan; Lee, Si-Chen; He, Jr-Hau; Javey, Ali
2015-02-11
When light is incident on 2D transition metal dichalcogenides (TMDCs), it engages in multiple reflections within underlying substrates, producing interferences that lead to enhancement or attenuation of the incoming and outgoing strength of light. Here, we report a simple method to engineer the light outcoupling in semiconducting TMDCs by modulating their dielectric surroundings. We show that by modulating the thicknesses of underlying substrates and capping layers, the interference caused by substrate can significantly enhance the light absorption and emission of WSe2, resulting in a ∼11 times increase in Raman signal and a ∼30 times increase in the photoluminescence (PL) intensity of WSe2. On the basis of the interference model, we also propose a strategy to control the photonic and optoelectronic properties of thin-layer WSe2. This work demonstrates the utilization of outcoupling engineering in 2D materials and offers a new route toward the realization of novel optoelectronic devices, such as 2D LEDs and solar cells.
2-D nonlinear IIR-filters for image processing - An exploratory analysis
NASA Technical Reports Server (NTRS)
Bauer, P. H.; Sartori, M.
1991-01-01
A new nonlinear IIR filter structure is introduced and its deterministic properties are analyzed. It is shown to be better suited for image processing applications than its linear shift-invariant counterpart. The new structure is obtained from causality inversion of a 2D quarterplane causal linear filter with respect to the two directions of propagation. It is demonstrated, that by using this design, a nonlinear 2D lowpass filter can be constructed, which is capable of effectively suppressing Gaussian or impulse noise without destroying important image information.
Interfacing graphene and related 2D materials with the 3D world.
Tománek, David
2015-04-10
An important prerequisite to translating the exceptional intrinsic performance of 2D materials such as graphene and transition metal dichalcogenides into useful devices precludes their successful integration within the current 3D technology. This review provides theoretical insight into nontrivial issues arising from interfacing 2D materials with 3D systems including epitaxy and ways to accommodate lattice mismatch, the key role of contact resistance and the effect of defects in electrical and thermal transport.
2D Crystal Semiconductors New Materials for GHz-THz Devices
2015-10-02
frequency operation. 4) Identify methods to improve carrier transport in 2D Crystal semiconductors. 5) Compare FETs made from naturally occuring and... chemically synthesized 2D Crystal semic???ductors. 6) Elucidate the effect of contact resistance, and gauge the challenges for GHz-THz electronics by... chemical doping, which involved replac- ing a small number of atoms of the 3-D semiconductor by those with higher or lower valence. The next advance
Multirate-based fast parallel algorithms for 2-D DHT-based real-valued discrete Gabor transform.
Tao, Liang; Kwan, Hon Keung
2012-07-01
Novel algorithms for the multirate and fast parallel implementation of the 2-D discrete Hartley transform (DHT)-based real-valued discrete Gabor transform (RDGT) and its inverse transform are presented in this paper. A 2-D multirate-based analysis convolver bank is designed for the 2-D RDGT, and a 2-D multirate-based synthesis convolver bank is designed for the 2-D inverse RDGT. The parallel channels in each of the two convolver banks have a unified structure and can apply the 2-D fast DHT algorithm to speed up their computations. The computational complexity of each parallel channel is low and is independent of the Gabor oversampling rate. All the 2-D RDGT coefficients of an image are computed in parallel during the analysis process and can be reconstructed in parallel during the synthesis process. The computational complexity and time of the proposed parallel algorithms are analyzed and compared with those of the existing fastest algorithms for 2-D discrete Gabor transforms. The results indicate that the proposed algorithms are the fastest, which make them attractive for real-time image processing.
NASA Astrophysics Data System (ADS)
Nath, Saurabh; Mukherjee, Anish; Chatterjee, Souvick; Ganguly, Ranjan; Sen, Swarnendu; Mukhopadhyay, Achintya; Boreyko, Jonathan
2014-11-01
We have observed that capillarity forces may cause floatation in a few non-intuitive configurations. These may be divided into 2 categories: i) floatation of heavier liquid droplets on lighter immiscible ones and ii) fully submerged floatation of lighter liquid droplets in a heavier immiscible medium. We call these counter-intuitive because of the inverse floatation configuration. For case (i) we have identified and studied in detail the several factors affecting the shape and maximum volume of the floating drop. We used water and vegetable oil combinations as test fluids and established the relation between Bond Number and maximum volume contained in a floating drop (in the order of μL). For case (ii), we injected vegetable oil drop-wise into a pool of water. The fully submerged configuration of the drop is not stable and a slight perturbation to the system causes the droplet to burst and float in partially submerged condition. Temporal variation of a characteristic length of the droplet is analyzed using MATLAB image processing. The constraint of small Bond Number establishes the assumption of lubrication regime in the thin gap. A brief theoretical formulation also shows the temporal variation of the gap thickness. Jadavpur University, Jagadis Bose Centre of Excellence, Virginia Tech.
Ishizuka, Tomoko; Hatano, Kouta; Murotani, Tomotaka; Yamatodani, Atsushi
2008-04-09
Leptin is a key signal linking peripheral adiposity levels to the regulation of energy homeostasis in the brain. The injection of leptin decreases body weight and food intake in lean rodents; however, in a rodent model of high fat diet-induced obesity (DIO), the exogenous leptin cannot improve adiposity. This ineffectiveness is known as leptin resistance, and the factors downstream of leptin signaling have received attention as viable targets in the treatment of obesity. We previously reported that the histaminergic system is one of the targets of leptin. In the present study, the effect of an H(3)-receptor inverse agonist on hypothalamic histamine release and energy intake was investigated in normal and DIO mice. Leptin (1.3 mg/kg, i.p.) significantly increased hypothalamic histamine release and reduced 12 h-energy intake in normal mice, but had no such effects in DIO mice. In contrast, clobenpropit (5 mg/kg, i.p.), an H(3)-inverse agonist, elicited a significant increase in histamine release in both types of mice. Clobenpropit did not reduce 12 h-energy intake; however, it decreased 3 h-energy intake in both types of mice. These results suggest that lack of the activation of the histaminergic system partly contributes to obesity in DIO mice and direct activation of the histaminergic system circumvents leptin resistance.
Constrained and joint inversion on unstructured meshes
NASA Astrophysics Data System (ADS)
Doetsch, J.; Jordi, C.; Rieckh, V.; Guenther, T.; Schmelzbach, C.
2015-12-01
Unstructured meshes allow for inclusion of arbitrary surface topography, complex acquisition geometry and undulating geological interfaces in the inversion of geophysical data. This flexibility opens new opportunities for coupling different geophysical and hydrological data sets in constrained and joint inversions. For example, incorporating geological interfaces that have been derived from high-resolution geophysical data (e.g., ground penetrating radar) can add geological constraints to inversions of electrical resistivity data. These constraints can be critical for a hydrogeological interpretation of the inversion results. For time-lapse inversions of geophysical data, constraints can be derived from hydrological point measurements in boreholes, but it is difficult to include these hard constraints in the inversion of electrical resistivity monitoring data. Especially mesh density and the regularization footprint around the hydrological point measurements are important for an improved inversion compared to the unconstrained case. With the help of synthetic and field examples, we analyze how regularization and coupling operators should be chosen for time-lapse inversions constrained by point measurements and for joint inversions of geophysical data in order to take full advantage of the flexibility of unstructured meshes. For the case of constraining to point measurements, it is important to choose a regularization operator that extends beyond the neighboring cells and the uncertainty in the point measurements needs to be accounted for. For joint inversion, the choice of the regularization depends on the expected subsurface heterogeneity and the cell size of the parameter mesh.
Nutter, C.
1981-04-01
MAG2D is an interactive computer program used for modeling 2-1/2-dimensional magnetic data. A forward algorithm is used to give the theoretical attraction of magnetic intensity at a station due to a perturbing body given by the initial model. The resultant model can then be adjusted for a better fit by a combination of manual adjustment, one-dimensional automatic search, and Marquardt inversion. MAG2D has an interactive data management system for data manipulation and display built around subroutines to do a forward problem, a one-dimensional direct search and an inversion. These subroutines were originally separate batch-mode programs.
Periodically sheared 2D Yukawa systems
Kovács, Anikó Zsuzsa; Hartmann, Peter; Donkó, Zoltán
2015-10-15
We present non-equilibrium molecular dynamics simulation studies on the dynamic (complex) shear viscosity of a 2D Yukawa system. We have identified a non-monotonic frequency dependence of the viscosity at high frequencies and shear rates, an energy absorption maximum (local resonance) at the Einstein frequency of the system at medium shear rates, an enhanced collective wave activity, when the excitation is near the plateau frequency of the longitudinal wave dispersion, and the emergence of significant configurational anisotropy at small frequencies and high shear rates.
ENERGY LANDSCAPE OF 2D FLUID FORMS
Y. JIANG; ET AL
2000-04-01
The equilibrium states of 2D non-coarsening fluid foams, which consist of bubbles with fixed areas, correspond to local minima of the total perimeter. (1) The authors find an approximate value of the global minimum, and determine directly from an image how far a foam is from its ground state. (2) For (small) area disorder, small bubbles tend to sort inwards and large bubbles outwards. (3) Topological charges of the same sign repel while charges of opposite sign attract. (4) They discuss boundary conditions and the uniqueness of the pattern for fixed topology.
Codon Constraints on Closed 2D Shapes,
2014-09-26
19843$ CODON CONSTRAINTS ON CLOSED 2D SHAPES Go Whitman Richards "I Donald D. Hoffman’ D T 18 Abstract: Codons are simple primitives for describing plane...RSONAL AUT"ORtIS) Richards, Whitman & Hoffman, Donald D. 13&. TYPE OF REPORT 13b. TIME COVERED N/A P8 AT F RRrT t~r. Ago..D,) is, PlE COUNT Reprint...outlines, if figure and ground are ignored. Later, we will address the problem of indexing identical codon descriptors that have different figure
Electrical resistivity borehole measurements: application to an urban tunnel site
NASA Astrophysics Data System (ADS)
Denis, A.; Marache, A.; Obellianne, T.; Breysse, D.
2002-06-01
This paper shows how it is possible to use wells drilled during geotechnical pre-investigation of a tunneling site to obtain a 2-D image of the resistivity close to a tunnel boring machine. An experimental apparatus is presented which makes it possible to perform single and borehole-to-borehole electrical measurements independent of the geological and hydrogeological context, which can be activated at any moment during the building of the tunnel. This apparatus is first demonstrated through its use on a test site. Numerical simulations and data inversion are used to analyse the experimental results. Finally, electrical resistivity tomography and single-borehole measurements on a tunneling site are presented. Experimental results show the viability of the apparatus and the efficiency of the inverse algorithm, and also highlight the limitations of the electrical resistivity tomography as a tool for geotechnical investigation in urban areas.
Wave-equation dispersion inversion
NASA Astrophysics Data System (ADS)
Li, Jing; Feng, Zongcai; Schuster, Gerard
2017-03-01
We present the theory for wave-equation inversion of dispersion curves, where the misfit function is the sum of the squared differences between the wavenumbers along the predicted and observed dispersion curves. The dispersion curves are obtained from Rayleigh waves recorded by vertical-component geophones. Similar to wave-equation traveltime tomography, the complicated surface wave arrivals in traces are skeletonized as simpler data, namely the picked dispersion curves in the phase-velocity and frequency domains. Solutions to the elastic wave equation and an iterative optimization method are then used to invert these curves for 2-D or 3-D S-wave velocity models. This procedure, denoted as wave-equation dispersion inversion (WD), does not require the assumption of a layered model and is significantly less prone to the cycle-skipping problems of full waveform inversion. The synthetic and field data examples demonstrate that WD can approximately reconstruct the S-wave velocity distributions in laterally heterogeneous media if the dispersion curves can be identified and picked. The WD method is easily extended to anisotropic data and the inversion of dispersion curves associated with Love waves.
2D Quantum Mechanical Study of Nanoscale MOSFETs
NASA Technical Reports Server (NTRS)
Svizhenko, Alexei; Anantram, M. P.; Govindan, T. R.; Biegel, B.; Kwak, Dochan (Technical Monitor)
2000-01-01
With the onset of quantum confinement in the inversion layer in nanoscale MOSFETs, behavior of the resonant level inevitably determines all device characteristics. While most classical device simulators take quantization into account in some simplified manner, the important details of electrostatics are missing. Our work addresses this shortcoming and provides: (a) a framework to quantitatively explore device physics issues such as the source-drain and gate leakage currents, DIBL, and threshold voltage shift due to quantization, and b) a means of benchmarking quantum corrections to semiclassical models (such as density-gradient and quantum-corrected MEDICI). We have developed physical approximations and computer code capable of realistically simulating 2-D nanoscale transistors, using the non-equilibrium Green's function (NEGF) method. This is the most accurate full quantum model yet applied to 2-D device simulation. Open boundary conditions and oxide tunneling are treated on an equal footing. Electrons in the ellipsoids of the conduction band are treated within the anisotropic effective mass approximation. We present the results of our simulations of MIT 25, 50 and 90 nm "well-tempered" MOSFETs and compare them to those of classical and quantum corrected models. The important feature of quantum model is smaller slope of Id-Vg curve and consequently higher threshold voltage. Surprisingly, the self-consistent potential profile shows lower injection barrier in the channel in quantum case. These results are qualitatively consistent with ID Schroedinger-Poisson calculations. The effect of gate length on gate-oxide leakage and subthreshold current has been studied. The shorter gate length device has an order of magnitude smaller current at zero gate bias than the longer gate length device without a significant trade-off in on-current. This should be a device design consideration.
2D Quantum Transport Modeling in Nanoscale MOSFETs
NASA Technical Reports Server (NTRS)
Svizhenko, Alexei; Anantram, M. P.; Govindan, T. R.; Biegel, Bryan
2001-01-01
With the onset of quantum confinement in the inversion layer in nanoscale MOSFETs, behavior of the resonant level inevitably determines all device characteristics. While most classical device simulators take quantization into account in some simplified manner, the important details of electrostatics are missing. Our work addresses this shortcoming and provides: (a) a framework to quantitatively explore device physics issues such as the source-drain and gate leakage currents, DIBL, and threshold voltage shift due to quantization, and b) a means of benchmarking quantum corrections to semiclassical models (such as density- gradient and quantum-corrected MEDICI). We have developed physical approximations and computer code capable of realistically simulating 2-D nanoscale transistors, using the non-equilibrium Green's function (NEGF) method. This is the most accurate full quantum model yet applied to 2-D device simulation. Open boundary conditions, oxide tunneling and phase-breaking scattering are treated on equal footing. Electrons in the ellipsoids of the conduction band are treated within the anisotropic effective mass approximation. Quantum simulations are focused on MIT 25, 50 and 90 nm "well- tempered" MOSFETs and compared to classical and quantum corrected models. The important feature of quantum model is smaller slope of Id-Vg curve and consequently higher threshold voltage. These results are quantitatively consistent with I D Schroedinger-Poisson calculations. The effect of gate length on gate-oxide leakage and sub-threshold current has been studied. The shorter gate length device has an order of magnitude smaller current at zero gate bias than the longer gate length device without a significant trade-off in on-current. This should be a device design consideration.
Remarks on thermalization in 2D CFT
NASA Astrophysics Data System (ADS)
de Boer, Jan; Engelhardt, Dalit
2016-12-01
We revisit certain aspects of thermalization in 2D conformal field theory (CFT). In particular, we consider similarities and differences between the time dependence of correlation functions in various states in rational and non-rational CFTs. We also consider the distinction between global and local thermalization and explain how states obtained by acting with a diffeomorphism on the ground state can appear locally thermal, and we review why the time-dependent expectation value of the energy-momentum tensor is generally a poor diagnostic of global thermalization. Since all 2D CFTs have an infinite set of commuting conserved charges, generic initial states might be expected to give rise to a generalized Gibbs ensemble rather than a pure thermal ensemble at late times. We construct the holographic dual of the generalized Gibbs ensemble and show that, to leading order, it is still described by a Banados-Teitelboim-Zanelli black hole. The extra conserved charges, while rendering c <1 theories essentially integrable, therefore seem to have little effect on large-c conformal field theories.
Microwave Assisted 2D Materials Exfoliation
NASA Astrophysics Data System (ADS)
Wang, Yanbin
Two-dimensional materials have emerged as extremely important materials with applications ranging from energy and environmental science to electronics and biology. Here we report our discovery of a universal, ultrafast, green, solvo-thermal technology for producing excellent-quality, few-layered nanosheets in liquid phase from well-known 2D materials such as such hexagonal boron nitride (h-BN), graphite, and MoS2. We start by mixing the uniform bulk-layered material with a common organic solvent that matches its surface energy to reduce the van der Waals attractive interactions between the layers; next, the solutions are heated in a commercial microwave oven to overcome the energy barrier between bulk and few-layers states. We discovered the minutes-long rapid exfoliation process is highly temperature dependent, which requires precise thermal management to obtain high-quality inks. We hypothesize a possible mechanism of this proposed solvo-thermal process; our theory confirms the basis of this novel technique for exfoliation of high-quality, layered 2D materials by using an as yet unknown role of the solvent.
Thermoelectric properties of inverse opals
NASA Astrophysics Data System (ADS)
Mahan, G. D.; Poilvert, N.; Crespi, V. H.
2016-02-01
Rayleigh's method [Philos. Mag. Ser. 5 34, 481 (1892)] is used to solve for the classical thermoelectric equations in inverse opals. His theory predicts that in an inverse opal, with periodic holes, the Seebeck coefficient and the figure of merit are identical to that of the bulk material. We also provide a major revision to Rayleigh's method, in using the electrochemical potential as an important variable, instead of the electrostatic potential. We also show that in some cases, the thermal boundary resistance is important in the effective thermal conductivity.
2D and 3D Numerical Simulations of Flux Cancellation
NASA Technical Reports Server (NTRS)
Karpen, Judith T.; DeVore, C.; Antiochos, S. K.; Linton, M. G.
2009-01-01
Cancellation of magnetic flux in the solar photosphere and chromosphere has been linked observationally and theoretically to a broad range of solar activity, from filament channel formation to CME initiation. Because this phenomenon is typically measured at only a single layer in the atmosphere, in the radial (line of sight) component of the magnetic field, the actual processes behind this observational signature are ambiguous. It is clear that reconnection is involved in some way, but the location of the reconnection sites and associated connectivity changes remain uncertain in most cases. We are using numerical modeling to demystify flux cancellation, beginning with the simplest possible configuration: a subphotospheric Lundquist flux tube surrounded by a potential field, immersed in a gravitationally stratified atmosphere, spanning many orders of magnitude in plasma beta. In this system, cancellation is driven slowly by a 2-cell circulation pattern imposed in the convection zone, such that the tops of the cells are located around the beta=1 level (i.e., the photosphere) and the flows converge and form a downdraft at the polarity inversion line; note however that no flow is imposed along the neutral line. We will present the results of 2D and 3D MHD-AMR simulations of flux cancellation, in which the flux at the photosphere begins in either an unsheared or sheared state. In all cases, a low-lying flux rope is formed by reconnection at the polarity inversion line within a few thousand seconds. The flux rope remains stable and does not rise, however, in contrast to models which do not include the presence of significant mass loading.
A hierarchically porous anatase TiO2 coated-WO3 2D IO bilayer film and its photochromic properties.
Li, Hua; Wu, Huazhong; Xiao, Jiajia; Su, Yanli; Robichaud, Jacques; Brüning, Ralf; Djaoued, Yahia
2016-01-18
A hierarchically porous anatase TiO2 coated-WO3 2D inverse opal (IO) bilayer film was fabricated on ITO glass using a layer by layer route with a hierarchically porous TiO2 top layer and an ordered super-macroporous WO3 2D IO bottom layer. This novel TiO2 coated-WO3 2D IO bilayer film was evaluated for photochromic applications.
Adaptation through chromosomal inversions in Anopheles
Ayala, Diego; Ullastres, Anna; González, Josefa
2014-01-01
Chromosomal inversions have been repeatedly involved in local adaptation in a large number of animals and plants. The ecological and behavioral plasticity of Anopheles species—human malaria vectors—is mirrored by high amounts of polymorphic inversions. The adaptive significance of chromosomal inversions has been consistently attested by strong and significant correlations between their frequencies and a number of phenotypic traits. Here, we provide an extensive literature review of the different adaptive traits associated with chromosomal inversions in the genus Anopheles. Traits having important consequences for the success of present and future vector control measures, such as insecticide resistance and behavioral changes, are discussed. PMID:24904633
2-D and 3-D Magnetic Inversion Studies in the South Atlantic
1988-01-01
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2-D or not 2-D, that is the question: A Northern California test
Mayeda, K; Malagnini, L; Phillips, W S; Walter, W R; Dreger, D
2005-06-06
Reliable estimates of the seismic source spectrum are necessary for accurate magnitude, yield, and energy estimation. In particular, how seismic radiated energy scales with increasing earthquake size has been the focus of recent debate within the community and has direct implications on earthquake source physics studies as well as hazard mitigation. The 1-D coda methodology of Mayeda et al. has provided the lowest variance estimate of the source spectrum when compared against traditional approaches that use direct S-waves, thus making it ideal for networks that have sparse station distribution. The 1-D coda methodology has been mostly confined to regions of approximately uniform complexity. For larger, more geophysically complicated regions, 2-D path corrections may be required. The complicated tectonics of the northern California region coupled with high quality broadband seismic data provides for an ideal ''apples-to-apples'' test of 1-D and 2-D path assumptions on direct waves and their coda. Using the same station and event distribution, we compared 1-D and 2-D path corrections and observed the following results: (1) 1-D coda results reduced the amplitude variance relative to direct S-waves by roughly a factor of 8 (800%); (2) Applying a 2-D correction to the coda resulted in up to 40% variance reduction from the 1-D coda results; (3) 2-D direct S-wave results, though better than 1-D direct waves, were significantly worse than the 1-D coda. We found that coda-based moment-rate source spectra derived from the 2-D approach were essentially identical to those from the 1-D approach for frequencies less than {approx}0.7-Hz, however for the high frequencies (0.7{le} f {le} 8.0-Hz), the 2-D approach resulted in inter-station scatter that was generally 10-30% smaller. For complex regions where data are plentiful, a 2-D approach can significantly improve upon the simple 1-D assumption. In regions where only 1-D coda correction is available it is still preferable over 2
2D Numerical MHD Models of Solar Explosive Events
NASA Astrophysics Data System (ADS)
Roussev, I.
2001-10-01
Observations of the Sun reveal a great variety of dynamic phenomena interpretable as a manifestation of magnetic reconnection. These range from small-scale 'Explosive events' seen in the 'quiet' Sun, through violent flares observed in active regions. The high degree of complexity of the magnetic field inferred from observations may locally produce a fruitful environment for the process of magnetic reconnection to take place. Explosive events are associated with regions undergoing magnetic flux cancellation. This thesis presents a 2-dimensional (2D) numerical study devoted to explore the idea that the salient spectral signatures seen in explosive events are most probably caused by bi-directional outflow jets as a results of an ongoing magnetic reconnection. In order to provide qualitative results needed for the better physical interpretation of solar explosive events, several models intended to represent a 'quiet' Sun transition of solar explosive events, several models intended to represent a 'quiet' Sun transition region undergoing magnetic reconnection are examined, in both unstratified and gravitationally stratified atmospheres. The magnetic reconnection is initiated in an ad hoc manner, and the dynamic evolution is followed by numerically solving the equations of 2D dissipative magnetohydrodynamics (MHD), including the effects of field-aligned thermal conduction, radiative losses, volumetric heating, and anomalous resistivity.
NASA Astrophysics Data System (ADS)
Benjamini, Dan; Basser, Peter J.
2016-10-01
Measuring multidimensional (e.g., 2D) relaxation spectra in NMR and MRI clinical applications is a holy grail of the porous media and biomedical MR communities. The main bottleneck is the inversion of Fredholm integrals of the first kind, an ill-conditioned problem requiring large amounts of data to stabilize a solution. We suggest a novel experimental design and processing framework to accelerate and improve the reconstruction of such 2D spectra that uses a priori information from the 1D projections of spectra, or marginal distributions. These 1D marginal distributions provide powerful constraints when 2D spectra are reconstructed, and their estimation requires an order of magnitude less data than a conventional 2D approach. This marginal distributions constrained optimization (MADCO) methodology is demonstrated here with a polyvinylpyrrolidone-water phantom that has 3 distinct peaks in the 2D D-T1 space. The stability, sensitivity to experimental parameters, and accuracy of this new approach are compared with conventional methods by serially subsampling the full data set. While the conventional, unconstrained approach performed poorly, the new method had proven to be highly accurate and robust, only requiring a fraction of the data. Additionally, synthetic T1 -T2 data are presented to explore the effects of noise on the estimations, and the performance of the proposed method with a smooth and realistic 2D spectrum. The proposed framework is quite general and can also be used with a variety of 2D MRI experiments (D-T2,T1 -T2, D -D, etc.), making these potentially feasible for preclinical and even clinical applications for the first time.
TOPAZ2D heat transfer code users manual and thermal property data base
Shapiro, A.B.; Edwards, A.L.
1990-05-01
TOPAZ2D is a two dimensional implicit finite element computer code for heat transfer analysis. This user's manual provides information on the structure of a TOPAZ2D input file. Also included is a material thermal property data base. This manual is supplemented with The TOPAZ2D Theoretical Manual and the TOPAZ2D Verification Manual. TOPAZ2D has been implemented on the CRAY, SUN, and VAX computers. TOPAZ2D can be used to solve for the steady state or transient temperature field on two dimensional planar or axisymmetric geometries. Material properties may be temperature dependent and either isotropic or orthotropic. A variety of time and temperature dependent boundary conditions can be specified including temperature, flux, convection, and radiation. Time or temperature dependent internal heat generation can be defined locally be element or globally by material. TOPAZ2D can solve problems of diffuse and specular band radiation in an enclosure coupled with conduction in material surrounding the enclosure. Additional features include thermally controlled reactive chemical mixtures, thermal contact resistance across an interface, bulk fluid flow, phase change, and energy balances. Thermal stresses can be calculated using the solid mechanics code NIKE2D which reads the temperature state data calculated by TOPAZ2D. A three dimensional version of the code, TOPAZ3D is available. The material thermal property data base, Chapter 4, included in this manual was originally published in 1969 by Art Edwards for use with his TRUMP finite difference heat transfer code. The format of the data has been altered to be compatible with TOPAZ2D. Bob Bailey is responsible for adding the high explosive thermal property data.
Transition to turbulence: 2D directed percolation
NASA Astrophysics Data System (ADS)
Chantry, Matthew; Tuckerman, Laurette; Barkley, Dwight
2016-11-01
The transition to turbulence in simple shear flows has been studied for well over a century, yet in the last few years has seen major leaps forward. In pipe flow, this transition shows the hallmarks of (1 + 1) D directed percolation, a universality class of continuous phase transitions. In spanwisely confined Taylor-Couette flow the same class is found, suggesting the phenomenon is generic to shear flows. However in plane Couette flow the largest simulations and experiments to-date find evidence for a discrete transition. Here we study a planar shear flow, called Waleffe flow, devoid of walls yet showing the fundamentals of planar transition to turbulence. Working with a quasi-2D yet Navier-Stokes derived model of this flow we are able to attack the (2 + 1) D transition problem. Going beyond the system sizes previously possible we find all of the required scalings of directed percolation and thus establish planar shears flow in this class.
2D quantum gravity from quantum entanglement.
Gliozzi, F
2011-01-21
In quantum systems with many degrees of freedom the replica method is a useful tool to study the entanglement of arbitrary spatial regions. We apply it in a way that allows them to backreact. As a consequence, they become dynamical subsystems whose position, form, and extension are determined by their interaction with the whole system. We analyze, in particular, quantum spin chains described at criticality by a conformal field theory. Its coupling to the Gibbs' ensemble of all possible subsystems is relevant and drives the system into a new fixed point which is argued to be that of the 2D quantum gravity coupled to this system. Numerical experiments on the critical Ising model show that the new critical exponents agree with those predicted by the formula of Knizhnik, Polyakov, and Zamolodchikov.
Simulation of Yeast Cooperation in 2D.
Wang, M; Huang, Y; Wu, Z
2016-03-01
Evolution of cooperation has been an active research area in evolutionary biology in decades. An important type of cooperation is developed from group selection, when individuals form spatial groups to prevent them from foreign invasions. In this paper, we study the evolution of cooperation in a mixed population of cooperating and cheating yeast strains in 2D with the interactions among the yeast cells restricted to their small neighborhoods. We conduct a computer simulation based on a game theoretic model and show that cooperation is increased when the interactions are spatially restricted, whether the game is of a prisoner's dilemma, snow drifting, or mutual benefit type. We study the evolution of homogeneous groups of cooperators or cheaters and describe the conditions for them to sustain or expand in an opponent population. We show that under certain spatial restrictions, cooperator groups are able to sustain and expand as group sizes become large, while cheater groups fail to expand and keep them from collapse.
2D Electrostatic Actuation of Microshutter Arrays
NASA Technical Reports Server (NTRS)
Burns, Devin E.; Oh, Lance H.; Li, Mary J.; Jones, Justin S.; Kelly, Daniel P.; Zheng, Yun; Kutyrev, Alexander S.; Moseley, Samuel H.
2015-01-01
An electrostatically actuated microshutter array consisting of rotational microshutters (shutters that rotate about a torsion bar) were designed and fabricated through the use of models and experiments. Design iterations focused on minimizing the torsional stiffness of the microshutters, while maintaining their structural integrity. Mechanical and electromechanical test systems were constructed to measure the static and dynamic behavior of the microshutters. The torsional stiffness was reduced by a factor of four over initial designs without sacrificing durability. Analysis of the resonant behavior of the microshutter arrays demonstrates that the first resonant mode is a torsional mode occurring around 3000 Hz. At low vacuum pressures, this resonant mode can be used to significantly reduce the drive voltage necessary for actuation requiring as little as 25V. 2D electrostatic latching and addressing was demonstrated using both a resonant and pulsed addressing scheme.
Canard configured aircraft with 2-D nozzle
NASA Technical Reports Server (NTRS)
Child, R. D.; Henderson, W. P.
1978-01-01
A closely-coupled canard fighter with vectorable two-dimensional nozzle was designed for enhanced transonic maneuvering. The HiMAT maneuver goal of a sustained 8g turn at a free-stream Mach number of 0.9 and 30,000 feet was the primary design consideration. The aerodynamic design process was initiated with a linear theory optimization minimizing the zero percent suction drag including jet effects and refined with three-dimensional nonlinear potential flow techniques. Allowances were made for mutual interference and viscous effects. The design process to arrive at the resultant configuration is described, and the design of a powered 2-D nozzle model to be tested in the LRC 16-foot Propulsion Wind Tunnel is shown.
Numerical Evaluation of 2D Ground States
NASA Astrophysics Data System (ADS)
Kolkovska, Natalia
2016-02-01
A ground state is defined as the positive radial solution of the multidimensional nonlinear problem
Gil, Bomi; Hwang, Eo-Jin; Lee, Song; Jang, Jinhee; Jung, So-Lyung; Ahn, Kook-Jin; Kim, Bum-soo
2016-01-01
Introduction To compare the diagnostic accuracy of contrast-enhanced 3D(dimensional) T1-weighted sampling perfection with application-optimized contrasts by using different flip angle evolutions (T1-SPACE), 2D fluid attenuated inversion recovery (FLAIR) images and 2D contrast-enhanced T1-weighted image in detection of leptomeningeal metastasis except for invasive procedures such as a CSF tapping. Materials and Methods Three groups of patients were included retrospectively for 9 months (from 2013-04-01 to 2013-12-31). Group 1 patients with positive malignant cells in CSF cytology (n = 22); group 2, stroke patients with steno-occlusion in ICA or MCA (n = 16); and group 3, patients with negative results on MRI, whose symptom were dizziness or headache (n = 25). A total of 63 sets of MR images are separately collected and randomly arranged: (1) CE 3D T1-SPACE; (2) 2D FLAIR; and (3) CE T1-GRE using a 3-Tesla MR system. A faculty neuroradiologist with 8-year-experience and another 2nd grade trainee in radiology reviewed each MR image- blinded by the results of CSF cytology and coded their observations as positives or negatives of leptomeningeal metastasis. The CSF cytology result was considered as a gold standard. Sensitivity and specificity of each MR images were calculated. Diagnostic accuracy was compared using a McNemar’s test. A Cohen's kappa analysis was performed to assess inter-observer agreements. Results Diagnostic accuracy was not different between 3D T1-SPACE and CSF cytology by both raters. However, the accuracy test of 2D FLAIR and 2D contrast-enhanced T1-weighted GRE was inconsistent by the two raters. The Kappa statistic results were 0.657 (3D T1-SPACE), 0.420 (2D FLAIR), and 0.160 (2D contrast-enhanced T1-weighted GRE). The 3D T1-SPACE images showed the highest inter-observer agreements between the raters. Conclusions Compared to 2D FLAIR and 2D contrast-enhanced T1-weighted GRE, contrast-enhanced 3D T1 SPACE showed a better detection rate of
AVO migration and inversion: Are they commutable?
Beydoun, W.B.; Jin, S.; Hanitzsch, C.
1994-12-31
With the increasing ambition of characterizing hydrocarbon traps in more subtle or complex reservoirs, Amplitude Variation with Offset (AVO) techniques are becoming a valuable seismic tool for quantitative seismic discrimination of lithologies and fluids. One of the biggest remaining challenges is to acquire and process the data in an amplitude preserved fashion and in multi-dimensional geology. This study is a component of this puzzle, and attempts to address the following processing question: what are the benefits of prestack migration before AVO inversion (process 1) versus performing an AVO inversion followed by a poststack migration (process 2)? The comparison is done on a 2-D synthetic model which is valid for process 2. The technique used for process 1 is the prestack depth AVO migration/inversion described in the text which estimates reflectivities and incidence angles in multi-dimensions from the data prior to AVO inversion. Process 2 results are derived using a commercial seismic processing software package.
Collins, Gillian; Armstrong, Eileen; McNulty, David; O'Hanlon, Sally; Geaney, Hugh; O'Dwyer, Colm
2016-01-01
This perspective reviews recent advances in inverse opal structures, how they have been developed, studied and applied as catalysts, catalyst support materials, as electrode materials for batteries, water splitting applications, solar-to-fuel conversion and electrochromics, and finally as photonic photocatalysts and photoelectrocatalysts. Throughout, we detail some of the salient optical characteristics that underpin recent results and form the basis for light-matter interactions that span electrochemical energy conversion systems as well as photocatalytic systems. Strategies for using 2D as well as 3D structures, ordered macroporous materials such as inverse opals are summarized and recent work on plasmonic-photonic coupling in metal nanoparticle-infiltrated wide band gap inverse opals for enhanced photoelectrochemistry are provided.
Collins, Gillian; Armstrong, Eileen; McNulty, David; O’Hanlon, Sally; Geaney, Hugh; O’Dwyer, Colm
2016-01-01
Abstract This perspective reviews recent advances in inverse opal structures, how they have been developed, studied and applied as catalysts, catalyst support materials, as electrode materials for batteries, water splitting applications, solar-to-fuel conversion and electrochromics, and finally as photonic photocatalysts and photoelectrocatalysts. Throughout, we detail some of the salient optical characteristics that underpin recent results and form the basis for light-matter interactions that span electrochemical energy conversion systems as well as photocatalytic systems. Strategies for using 2D as well as 3D structures, ordered macroporous materials such as inverse opals are summarized and recent work on plasmonic–photonic coupling in metal nanoparticle-infiltrated wide band gap inverse opals for enhanced photoelectrochemistry are provided. PMID:27877904
Duality Between Spin Networks and the 2D Ising Model
NASA Astrophysics Data System (ADS)
Bonzom, Valentin; Costantino, Francesco; Livine, Etera R.
2016-06-01
The goal of this paper is to exhibit a deep relation between the partition function of the Ising model on a planar trivalent graph and the generating series of the spin network evaluations on the same graph. We provide respectively a fermionic and a bosonic Gaussian integral formulation for each of these functions and we show that they are the inverse of each other (up to some explicit constants) by exhibiting a supersymmetry relating the two formulations. We investigate three aspects and applications of this duality. First, we propose higher order supersymmetric theories that couple the geometry of the spin networks to the Ising model and for which supersymmetric localization still holds. Secondly, after interpreting the generating function of spin network evaluations as the projection of a coherent state of loop quantum gravity onto the flat connection state, we find the probability distribution induced by that coherent state on the edge spins and study its stationary phase approximation. It is found that the stationary points correspond to the critical values of the couplings of the 2D Ising model, at least for isoradial graphs. Third, we analyze the mapping of the correlations of the Ising model to spin network observables, and describe the phase transition on those observables on the hexagonal lattice. This opens the door to many new possibilities, especially for the study of the coarse-graining and continuum limit of spin networks in the context of quantum gravity.
CAST2D: A finite element computer code for casting process modeling
Shapiro, A.B.; Hallquist, J.O.
1991-10-01
CAST2D is a coupled thermal-stress finite element computer code for casting process modeling. This code can be used to predict the final shape and stress state of cast parts. CAST2D couples the heat transfer code TOPAZ2D and solid mechanics code NIKE2D. CAST2D has the following features in addition to all the features contained in the TOPAZ2D and NIKE2D codes: (1) a general purpose thermal-mechanical interface algorithm (i.e., slide line) that calculates the thermal contact resistance across the part-mold interface as a function of interface pressure and gap opening; (2) a new phase change algorithm, the delta function method, that is a robust method for materials undergoing isothermal phase change; (3) a constitutive model that transitions between fluid behavior and solid behavior, and accounts for material volume change on phase change; and (4) a modified plot file data base that allows plotting of thermal variables (e.g., temperature, heat flux) on the deformed geometry. Although the code is specialized for casting modeling, it can be used for other thermal stress problems (e.g., metal forming).
Uncertainty and Bayesian Inversion of Marine CSEM data: From Despair to Optimism
NASA Astrophysics Data System (ADS)
Ray, A.; Key, K. W.
2012-12-01
distributions from all inverted models containing similar layer depths to those observed in a collocated seismic model, or we could incorporate depth and resistivity constraints from a nearby well-log to learn which anomalous features would be required in the rest of the model space. It is even possible to pull out ensembles of models that satisfy a given model norm such as minimizing a measure of roughness. The RJ-MCMC method also presents a tantalizing possibility for extension to 2D and 3D Bayesian inversion of CSEM data in the future, as it tackles the problem of objective model selection, which could ease the computational burden of evaluating forward models with many parameters.
Complex Resistivity 3D Imaging for Ground Reinforcement Site
NASA Astrophysics Data System (ADS)
Son, J.; Kim, J.; Park, S.
2012-12-01
Induced polarization (IP) method is used for mineral exploration and generally classified into two categories, time and frequency domain method. IP method in frequency domain measures amplitude and absolute phase to the transmitted currents, and is often called spectral induced polarization (SIP) when measurement is made for the wide-band frequencies. Our research group has been studying the modeling and inversion algorithms of complex resistivity method since several years ago and recently started to apply this method for various field applications. We already completed the development of 2/3D modeling and inversion program and developing another algorithm to use wide-band data altogether. Until now complex resistivity (CR) method was mainly used for the surface or tomographic survey of mineral exploration. Through the experience, we can find that the resistivity section from CR method is very similar with that of conventional resistivity method. Interpretation of the phase section is generally well matched with the geological information of survey area. But because most of survey area has very touch and complex terrain, 2D survey and interpretation are used generally. In this study, the case study of 3D CR survey conducted for the site where ground reinforcement was done to prevent the subsidence will be introduced. Data was acquired with the Zeta system, the complex resistivity measurement system produced by Zonge Co. using 8 frequencies from 0.125 to 16 Hz. 2D survey was conducted for total 6 lines with 5 m dipole spacing and 20 electrodes. Line length is 95 meter for every line. Among these 8 frequency data, data below 1 Hz was used considering its quality. With the 6 line data, 3D inversion was conducted. Firstly 2D interpretation was made with acquired data and its results were compared with those of resistivity survey. Resulting resistivity image sections of CR and resistivity method were very similar. Anomalies in phase image section showed good agreement
The advantages of logarithmically scaled data for electromagnetic inversion
NASA Astrophysics Data System (ADS)
Wheelock, Brent; Constable, Steven; Key, Kerry
2015-06-01
Non-linear inversion algorithms traverse a data misfit space over multiple iterations of trial models in search of either a global minimum or some target misfit contour. The success of the algorithm in reaching that objective depends upon the smoothness and predictability of the misfit space. For any given observation, there is no absolute form a datum must take, and therefore no absolute definition for the misfit space; in fact, there are many alternatives. However, not all misfit spaces are equal in terms of promoting the success of inversion. In this work, we appraise three common forms that complex data take in electromagnetic geophysical methods: real and imaginary components, a power of amplitude and phase, and logarithmic amplitude and phase. We find that the optimal form is logarithmic amplitude and phase. Single-parameter misfit curves of log-amplitude and phase data for both magnetotelluric and controlled-source electromagnetic methods are the smoothest of the three data forms and do not exhibit flattening at low model resistivities. Synthetic, multiparameter, 2-D inversions illustrate that log-amplitude and phase is the most robust data form, converging to the target misfit contour in the fewest steps regardless of starting model and the amount of noise added to the data; inversions using the other two data forms run slower or fail under various starting models and proportions of noise. It is observed that inversion with log-amplitude and phase data is nearly two times faster in converging to a solution than with other data types. We also assess the statistical consequences of transforming data in the ways discussed in this paper. With the exception of real and imaginary components, which are assumed to be Gaussian, all other data types do not produce an expected mean-squared misfit value of 1.00 at the true model (a common assumption) as the errors in the complex data become large. We recommend that real and imaginary data with errors larger than 10 per
Improved SOLA Inversions of MDI Data
NASA Astrophysics Data System (ADS)
Larsen, R. M.; Christensen-Dalsgaard, J.; Kosovichev, A. G.; Schou, J.
We present a new version of 2d-SOLA, where the target functions have been modified to match the behavior of the mode kernels near the rotation axis and to minimize near-surface contributions. Inversion of artificial data show that these modifications significantly improve the effective resolution near the pole, which allows us to assess the reliability of the high-latitude features seen by other inversion methods. Most importantly, our new inversions seem to confirm the detection of a submerged polar jet previously seen in the 2d-RLS inversions reported by Schou et al. 1998. A test of the robustness of the improved method is carried out by inverting artificial data from the MDI Hare and Hounds exercise. We analyze the averaging kernels and error propagation of the method, and also describe the error-correlation between different points in the solution, the latter being a potential source of spurious features in the solutions as pointed out by Howe and Thompson, 1996. So far, helioseismic datasets given in the form of a-coefficients have been inverted under the assumption that the errors in different a-coefficients are uncorrelated. The MDI peak-bagging procedure, however, does produce estimates of the error-correlation between a-coefficients within the same multiplet. Here we investigate the effect of including this knowledge in the inversions.
Zocchi, Maria Raffaella; Camodeca, Caterina; Nuti, Elisa; Rossello, Armando; Venè, Roberta; Tosetti, Francesca; Dapino, Irene; Costa, Delfina; Musso, Alessandra; Poggi, Alessandro
2016-01-01
ABSTRACT Hodgkin lymphoma (HL) resistant to conventional therapies is increasing, making of interest the search for new schemes of treatment. Members of the “A Disintegrin And Metalloproteases” (ADAMs) family, mainly ADAM10 or ADAM17, have been proposed as therapeutic targets in solid tumors and some ADAMs inhibitors have been shown to exert antitumor effects. We have previously described an overexpression of ADAM10 in HL, together with increased release of NKG2D ligands (NKG2D-L) and reduced activation of effector T lymphocytes with anti-lymphoma capacity. Aim of the present work was to verify whether inhibition of ADAM10 in HL cells could restore the triggering of NKG2D-dependent anti-lymphoma T cell response. As no selective ADAM10 blockers have been reported so far, we synthesized the two hydroxamate compounds LT4 and MN8 with selectivity for ADAM10 over metalloproteases (MMPs), LT4 showing higher specificity for ADAM10 over ADAM17. We show that (i) HL lymph nodes (LN) and cultured HL cells express high levels of the mature active membrane form of ADAM10; (ii) ADAM10 is the major sheddase for the NKG2D-L in HL cells; (iii) the new LT4 and MN8 compounds strongly reduce the shedding of NKG2D-L by HL cell lines and enhance the binding of NKG2D receptor; (iv) of note, these new ADAM10 inhibitors increase the sensitivity of HL cell lines to NKG2D-dependent cell killing exerted by natural killer and γδ T cells. Overall, the biologic activity of LT4 and MN8 appears to be more potent than that of the commercial inhibitor GI254023X. PMID:27467923
Zocchi, Maria Raffaella; Camodeca, Caterina; Nuti, Elisa; Rossello, Armando; Venè, Roberta; Tosetti, Francesca; Dapino, Irene; Costa, Delfina; Musso, Alessandra; Poggi, Alessandro
2016-05-01
Hodgkin lymphoma (HL) resistant to conventional therapies is increasing, making of interest the search for new schemes of treatment. Members of the "A Disintegrin And Metalloproteases" (ADAMs) family, mainly ADAM10 or ADAM17, have been proposed as therapeutic targets in solid tumors and some ADAMs inhibitors have been shown to exert antitumor effects. We have previously described an overexpression of ADAM10 in HL, together with increased release of NKG2D ligands (NKG2D-L) and reduced activation of effector T lymphocytes with anti-lymphoma capacity. Aim of the present work was to verify whether inhibition of ADAM10 in HL cells could restore the triggering of NKG2D-dependent anti-lymphoma T cell response. As no selective ADAM10 blockers have been reported so far, we synthesized the two hydroxamate compounds LT4 and MN8 with selectivity for ADAM10 over metalloproteases (MMPs), LT4 showing higher specificity for ADAM10 over ADAM17. We show that (i) HL lymph nodes (LN) and cultured HL cells express high levels of the mature active membrane form of ADAM10; (ii) ADAM10 is the major sheddase for the NKG2D-L in HL cells; (iii) the new LT4 and MN8 compounds strongly reduce the shedding of NKG2D-L by HL cell lines and enhance the binding of NKG2D receptor; (iv) of note, these new ADAM10 inhibitors increase the sensitivity of HL cell lines to NKG2D-dependent cell killing exerted by natural killer and γδ T cells. Overall, the biologic activity of LT4 and MN8 appears to be more potent than that of the commercial inhibitor GI254023X.
Persistence Measures for 2d Soap Froth
NASA Astrophysics Data System (ADS)
Feng, Y.; Ruskin, H. J.; Zhu, B.
Soap froths as typical disordered cellular structures, exhibiting spatial and temporal evolution, have been studied through their distributions and topological properties. Recently, persistence measures, which permit representation of the froth as a two-phase system, have been introduced to study froth dynamics at different length scales. Several aspects of the dynamics may be considered and cluster persistence has been observed through froth experiment. Using a direct simulation method, we have investigated persistent properties in 2D froth both by monitoring the persistence of survivor cells, a topologically independent measure, and in terms of cluster persistence. It appears that the area fraction behavior for both survivor and cluster persistence is similar for Voronoi froth and uniform froth (with defects). Survivor and cluster persistent fractions are also similar for a uniform froth, particularly when geometries are constrained, but differences observed for the Voronoi case appear to be attributable to the strong topological dependency inherent in cluster persistence. Survivor persistence, on the other hand, depends on the number rather than size and position of remaining bubbles and does not exhibit the characteristic decay to zero.
Competing coexisting phases in 2D water
NASA Astrophysics Data System (ADS)
Zanotti, Jean-Marc; Judeinstein, Patrick; Dalla-Bernardina, Simona; Creff, Gaëlle; Brubach, Jean-Blaise; Roy, Pascale; Bonetti, Marco; Ollivier, Jacques; Sakellariou, Dimitrios; Bellissent-Funel, Marie-Claire
2016-05-01
The properties of bulk water come from a delicate balance of interactions on length scales encompassing several orders of magnitudes: i) the Hydrogen Bond (HBond) at the molecular scale and ii) the extension of this HBond network up to the macroscopic level. Here, we address the physics of water when the three dimensional extension of the HBond network is frustrated, so that the water molecules are forced to organize in only two dimensions. We account for the large scale fluctuating HBond network by an analytical mean-field percolation model. This approach provides a coherent interpretation of the different events experimentally (calorimetry, neutron, NMR, near and far infra-red spectroscopies) detected in interfacial water at 160, 220 and 250 K. Starting from an amorphous state of water at low temperature, these transitions are respectively interpreted as the onset of creation of transient low density patches of 4-HBonded molecules at 160 K, the percolation of these domains at 220 K and finally the total invasion of the surface by them at 250 K. The source of this surprising behaviour in 2D is the frustration of the natural bulk tetrahedral local geometry and the underlying very significant increase in entropy of the interfacial water molecules.
Competing coexisting phases in 2D water
Zanotti, Jean-Marc; Judeinstein, Patrick; Dalla-Bernardina, Simona; Creff, Gaëlle; Brubach, Jean-Blaise; Roy, Pascale; Bonetti, Marco; Ollivier, Jacques; Sakellariou, Dimitrios; Bellissent-Funel, Marie-Claire
2016-01-01
The properties of bulk water come from a delicate balance of interactions on length scales encompassing several orders of magnitudes: i) the Hydrogen Bond (HBond) at the molecular scale and ii) the extension of this HBond network up to the macroscopic level. Here, we address the physics of water when the three dimensional extension of the HBond network is frustrated, so that the water molecules are forced to organize in only two dimensions. We account for the large scale fluctuating HBond network by an analytical mean-field percolation model. This approach provides a coherent interpretation of the different events experimentally (calorimetry, neutron, NMR, near and far infra-red spectroscopies) detected in interfacial water at 160, 220 and 250 K. Starting from an amorphous state of water at low temperature, these transitions are respectively interpreted as the onset of creation of transient low density patches of 4-HBonded molecules at 160 K, the percolation of these domains at 220 K and finally the total invasion of the surface by them at 250 K. The source of this surprising behaviour in 2D is the frustration of the natural bulk tetrahedral local geometry and the underlying very significant increase in entropy of the interfacial water molecules. PMID:27185018
Ishola, Kehinde S; Nawawi, Mohd Nm; Abdullah, Khiruddin; Sabri, Ali Idriss Aboubakar; Adiat, Kola Abdulnafiu
2014-01-01
This study attempts to combine the results of geophysical images obtained from three commonly used electrode configurations using an image processing technique in order to assess their capabilities to reproduce two-dimensional (2-D) resistivity models. All the inverse resistivity models were processed using the PCI Geomatica software package commonly used for remote sensing data sets. Preprocessing of the 2-D inverse models was carried out to facilitate further processing and statistical analyses. Four Raster layers were created, three of these layers were used for the input images and the fourth layer was used as the output of the combined images. The data sets were merged using basic statistical approach. Interpreted results show that all images resolved and reconstructed the essential features of the models. An assessment of the accuracy of the images for the four geologic models was performed using four criteria: the mean absolute error and mean percentage absolute error, resistivity values of the reconstructed blocks and their displacements from the true models. Generally, the blocks of the images of maximum approach give the least estimated errors. Also, the displacement of the reconstructed blocks from the true blocks is the least and the reconstructed resistivities of the blocks are closer to the true blocks than any other combined used. Thus, it is corroborated that when inverse resistivity models are combined, most reliable and detailed information about the geologic models is obtained than using individual data sets.
NASA Astrophysics Data System (ADS)
Cheng, Chingyun; Kangara, Jayampathi; Arakelyan, Ilya; Thomas, John
2016-05-01
We tune the dimensionality of a strongly interacting degenerate 6 Li Fermi gas from 2D to quasi-2D, by adjusting the radial confinement of pancake-shaped clouds to control the radial chemical potential. In the 2D regime with weak radial confinement, the measured pair binding energies are in agreement with 2D-BCS mean field theory, which predicts dimer pairing energies in the many-body regime. In the qausi-2D regime obtained with increased radial confinement, the measured pairing energy deviates significantly from 2D-BCS theory. In contrast to the pairing energy, the measured radii of the cloud profiles are not fit by 2D-BCS theory in either the 2D or quasi-2D regimes, but are fit in both regimes by a beyond mean field polaron-model of the free energy. Supported by DOE, ARO, NSF, and AFOSR.
Graph-Based Transform for 2D Piecewise Smooth Signals With Random Discontinuity Locations.
Zhang, Dong; Liang, Jie
2017-04-01
The graph-based block transform recently emerged as an effective tool for compressing some special signals such as depth images in 3D videos. However, in existing methods, overheads are required to describe the graph of the block, from which the decoder has to calculate the transform via time-consuming eigendecomposition. To address these problems, in this paper, we aim to develop a single graph-based transform for a class of 2D piecewise smooth signals with similar discontinuity patterns. We first consider the deterministic case with a known discontinuity location in each row. We propose a 2D first-order autoregression (2D AR1) model and a 2D graph for this type of signals. We show that the closed-form expression of the inverse of a biased Laplacian matrix of the proposed 2D graph is exactly the covariance matrix of the proposed 2D AR1 model. Therefore, the optimal transform for the signal are the eigenvectors of the proposed graph Laplacian. Next, we show that similar results hold in the random case, where the locations of the discontinuities in different rows are randomly distributed within a confined region, and we derive the closed-form expression of the corresponding optimal 2D graph Laplacian. The theory developed in this paper can be used to design both pre-computed transforms and signal-dependent transforms with low complexities. Finally, depth image coding experiments demonstrate that our methods can achieve similar performance to the state-of-the-art method, but our complexity is much lower.
NASA Astrophysics Data System (ADS)
Hamdi, H.; Qausar, A. M.; Srigutomo, W.
2016-08-01
Controlled source audio-frequency magnetotellurics (CSAMT) is a frequency-domain electromagnetic sounding technique which uses a fixed grounded dipole as an artificial signal source. Measurement of CSAMT with finite distance between transmitter and receiver caused a complex wave. The shifted of the electric field due to the static effect caused elevated resistivity curve up or down and affects the result of measurement. The objective of this study was to obtain data that have been corrected for source and static effects as to have the same characteristic as MT data which are assumed to exhibit plane wave properties. Corrected CSAMT data were inverted to reveal subsurface resistivity model. Source effect correction method was applied to eliminate the effect of the signal source and static effect was corrected by using spatial filtering technique. Inversion method that used in this study is the Occam's 2D Inversion. The results of inversion produces smooth models with a small misfit value, it means the model can describe subsurface conditions well. Based on the result of inversion was predicted measurement area is rock that has high permeability values with rich hot fluid.
Spin splitting in 2D monochalcogenide semiconductors.
Do, Dat T; Mahanti, Subhendra D; Lai, Chih Wei
2015-11-24
We report ab initio calculations of the spin splitting of the uppermost valence band (UVB) and the lowermost conduction band (LCB) in bulk and atomically thin GaS, GaSe, GaTe, and InSe. These layered monochalcogenides appear in four major polytypes depending on the stacking order, except for the monoclinic GaTe. Bulk and few-layer ε-and γ -type, and odd-number β-type GaS, GaSe, and InSe crystals are noncentrosymmetric. The spin splittings of the UVB and the LCB near the Γ-point in the Brillouin zone are finite, but still smaller than those in a zinc-blende semiconductor such as GaAs. On the other hand, the spin splitting is zero in centrosymmetric bulk and even-number few-layer β-type GaS, GaSe, and InSe, owing to the constraint of spatial inversion symmetry. By contrast, GaTe exhibits zero spin splitting because it is centrosymmetric down to a single layer. In these monochalcogenide semiconductors, the separation of the non-degenerate conduction and valence bands from adjacent bands results in the suppression of Elliot-Yafet spin relaxation mechanism. Therefore, the electron- and hole-spin relaxation times in these systems with zero or minimal spin splittings are expected to exceed those in GaAs when the D'yakonov-Perel' spin relaxation mechanism is also suppressed.
Spin splitting in 2D monochalcogenide semiconductors
Do, Dat T.; Mahanti, Subhendra D.; Lai, Chih Wei
2015-01-01
We report ab initio calculations of the spin splitting of the uppermost valence band (UVB) and the lowermost conduction band (LCB) in bulk and atomically thin GaS, GaSe, GaTe, and InSe. These layered monochalcogenides appear in four major polytypes depending on the stacking order, except for the monoclinic GaTe. Bulk and few-layer ε-and γ -type, and odd-number β-type GaS, GaSe, and InSe crystals are noncentrosymmetric. The spin splittings of the UVB and the LCB near the Γ-point in the Brillouin zone are finite, but still smaller than those in a zinc-blende semiconductor such as GaAs. On the other hand, the spin splitting is zero in centrosymmetric bulk and even-number few-layer β-type GaS, GaSe, and InSe, owing to the constraint of spatial inversion symmetry. By contrast, GaTe exhibits zero spin splitting because it is centrosymmetric down to a single layer. In these monochalcogenide semiconductors, the separation of the non-degenerate conduction and valence bands from adjacent bands results in the suppression of Elliot-Yafet spin relaxation mechanism. Therefore, the electron- and hole-spin relaxation times in these systems with zero or minimal spin splittings are expected to exceed those in GaAs when the D’yakonov-Perel’ spin relaxation mechanism is also suppressed. PMID:26596907
Spin splitting in 2D monochalcogenide semiconductors
NASA Astrophysics Data System (ADS)
Do, Dat T.; Mahanti, Subhendra D.; Lai, Chih Wei
2015-11-01
We report ab initio calculations of the spin splitting of the uppermost valence band (UVB) and the lowermost conduction band (LCB) in bulk and atomically thin GaS, GaSe, GaTe, and InSe. These layered monochalcogenides appear in four major polytypes depending on the stacking order, except for the monoclinic GaTe. Bulk and few-layer ε-and γ -type, and odd-number β-type GaS, GaSe, and InSe crystals are noncentrosymmetric. The spin splittings of the UVB and the LCB near the Γ-point in the Brillouin zone are finite, but still smaller than those in a zinc-blende semiconductor such as GaAs. On the other hand, the spin splitting is zero in centrosymmetric bulk and even-number few-layer β-type GaS, GaSe, and InSe, owing to the constraint of spatial inversion symmetry. By contrast, GaTe exhibits zero spin splitting because it is centrosymmetric down to a single layer. In these monochalcogenide semiconductors, the separation of the non-degenerate conduction and valence bands from adjacent bands results in the suppression of Elliot-Yafet spin relaxation mechanism. Therefore, the electron- and hole-spin relaxation times in these systems with zero or minimal spin splittings are expected to exceed those in GaAs when the D’yakonov-Perel’ spin relaxation mechanism is also suppressed.
2D discrete Fourier transform on sliding windows.
Park, Chun-Su
2015-03-01
Discrete Fourier transform (DFT) is the most widely used method for determining the frequency spectra of digital signals. In this paper, a 2D sliding DFT (2D SDFT) algorithm is proposed for fast implementation of the DFT on 2D sliding windows. The proposed 2D SDFT algorithm directly computes the DFT bins of the current window using the precalculated bins of the previous window. Since the proposed algorithm is designed to accelerate the sliding transform process of a 2D input signal, it can be directly applied to computer vision and image processing applications. The theoretical analysis shows that the computational requirement of the proposed 2D SDFT algorithm is the lowest among existing 2D DFT algorithms. Moreover, the output of the 2D SDFT is mathematically equivalent to that of the traditional DFT at all pixel positions.
Chmelík, M; Kukurová, I Just; Gruber, S; Krššák, M; Valkovič, L; Trattnig, S; Bogner, W
2013-05-01
A fully adiabatic phosphorus (31P) two-dimensional (2D) chemical shift spectroscopic imaging sequence with reduced chemical shift displacement error for 7 T, based on 1D-image-selected in vivo spectroscopy, combined with 2D-chemical shift spectroscopic imaging selection, was developed. Slice-selective excitation was achieved by a spatially selective broadband GOIA-W(16,4) inversion pulse with an interleaved subtraction scheme before nonselective adiabatic excitation, and followed by 2D phase encoding. The use of GOIA-W(16,4) pulses (bandwidth 4.3-21.6 kHz for 10-50 mm slices) reduced the chemical shift displacement error in the slice direction ∼1.5-7.7 fold, compared to conventional 2D-chemical shift spectroscopic imaging with Sinc3 selective pulses (2.8 kHz). This reduction was experimentally demonstrated with measurements of an MR spectroscopy localization phantom and with experimental evaluation of pulse profiles. In vivo experiments in clinically acceptable measurement times were demonstrated in the calf muscle (nominal voxel volume, 5.65 ml in 6 min 53 s), brain (10 ml, 6 min 32 s), and liver (8.33 ml, 8 min 14 s) of healthy volunteers at 7 T. High reproducibility was found in the calf muscle at 7 T. In combination with adiabatic excitation, this sequence is insensitive to the B1 inhomogeneities associated with surface coils. This sequence, which is termed GOIA-1D-ISIS/2D-CSI (goISICS), has the potential to be applied in both clinical research and in the clinical routine.
Katsagoni, Christina N; Papatheodoridis, George V; Papageorgiou, Maria-Vasiliki; Ioannidou, Panagiota; Deutsch, Melanie; Alexopoulou, Alexandra; Papadopoulos, Nikolaos; Fragopoulou, Elisabeth; Kontogianni, Meropi D
2017-03-01
Several lifestyle habits have been described as risk factors for nonalcoholic fatty liver disease (NAFLD). Given that both healthy and unhealthy habits tend to cluster, the aim of this study was to identify lifestyle patterns and explore their potential associations with clinical characteristics of individuals with NAFLD. One hundred and thirty-six consecutive patients with ultrasound-proven NAFLD were included. Diet and physical activity level were assessed through appropriate questionnaires. Habitual night sleep hours and duration of midday naps were recorded. Optimal sleep duration was defined as sleep hours ≥ 7 and ≤ 9 h/day. Lifestyle patterns were identified using principal component analysis. Eight components were derived explaining 67% of total variation of lifestyle characteristics. Lifestyle pattern 3, namely high consumption of low-fat dairy products, vegetables, fish, and optimal sleep duration was negatively associated with insulin resistance (β = -1.66, P = 0.008) and liver stiffness (β = -1.62, P = 0.05) after controlling for age, sex, body mass index, energy intake, smoking habits, adiponectin, and tumor necrosis factor-α. Lifestyle pattern 1, namely high consumption of full-fat dairy products, refined cereals, potatoes, red meat, and high television viewing time was positively associated with insulin resistance (β = 1.66, P = 0.005), although this association was weakened after adjusting for adiponectin and tumor necrosis factor-α. A "healthy diet-optimal sleep" lifestyle pattern was beneficially associated with insulin resistance and liver stiffness in NAFLD patients independent of body weight status and energy intake.
MAGNUM2D. Radionuclide Transport Porous Media
Langford, D.W.; Baca, R.G.
1989-03-01
MAGNUM2D was developed to analyze thermally driven fluid motion in the deep basalts below the Paco Basin at the Westinghouse Hanford Site. Has been used in the Basalt Waste Isolation Project to simulate nonisothermal groundwater flow in a heterogeneous anisotropic medium and heat transport in a water/rock system near a high level nuclear waste repository. Allows three representations of the hydrogeologic system: an equivalent porous continuum, a system of discrete, unfilled, and interconnecting fractures separated by impervious rock mass, and a low permeability porous continuum with several discrete, unfilled fractures traversing the medium. The calculations assume local thermodynamic equilibrium between the rock and groundwater, nonisothermal Darcian flow in the continuum portions of the rock, and nonisothermal Poiseuille flow in discrete unfilled fractures. In addition, the code accounts for thermal loading within the elements, zero normal gradient and fixed boundary conditions for both temperature and hydraulic head, and simulation of the temperature and flow independently. The Q2DGEOM preprocessor was developed to generate, modify, plot and verify quadratic two dimensional finite element geometries. The BCGEN preprocessor generates the boundary conditions for head and temperature and ICGEN generates the initial conditions. The GRIDDER postprocessor interpolates nonregularly spaced nodal flow and temperature data onto a regular rectangular grid. CONTOUR plots and labels contour lines for a function of two variables and PARAM plots cross sections and time histories for a function of time and one or two spatial variables. NPRINT generates data tables that display the data along horizontal or vertical cross sections. VELPLT differentiates the hydraulic head and buoyancy data and plots the velocity vectors. The PATH postprocessor plots flow paths and computes the corresponding travel times.
MAGNUM2D. Radionuclide Transport Porous Media
Langford, D.W.; Baca, R.G.
1988-08-01
MAGNUM2D was developed to analyze thermally driven fluid motion in the deep basalts below the Paco Basin at the Westinghouse Hanford Site. Has been used in the Basalt Waste Isolation Project to simulate nonisothermal groundwater flow in a heterogeneous anisotropic medium and heat transport in a water/rock system near a high level nuclear waste repository. Allows three representations of the hydrogeologic system: an equivalent porous continuum, a system of discrete, unfilled, and interconnecting fractures separated by impervious rock mass, and a low permeability porous continuum with several discrete, unfilled fractures traversing the medium. The calculation assumes local thermodynamic equilibrium between the rock and groundwater, nonisothermal Darcian flow in the continuum portions of the rock, and nonisothermal Poiseuille flow in discrete unfilled fractures. In addition, the code accounts for thermal loading within the elements, zero normal gradient and fixed boundary conditions for both temperature and hydraulic head, and simulation of the temperature and flow independently. The Q2DGEOM preprocessor was developed to generate, modify, plot and verify quadratic two dimensional finite element geometries. The BCGEN preprocessor generates the boundary conditions for head and temperature and ICGEN generates the initial conditions. The GRIDDER postprocessor interpolates nonregularly spaced nodal flow and temperature data onto a regular rectangular grid. CONTOUR plots and labels contour lines for a function of two variables and PARAM plots cross sections and time histories for a function of time and one or two spatial variables. NPRINT generates data tables that display the data along horizontal or vertical cross sections. VELPLT differentiates the hydraulic head and buoyancy data and plots the velocity vectors. The PATH postprocessor plots flow paths and computes the corresponding travel times.
NASA Astrophysics Data System (ADS)
Beka, Thomas I.; Smirnov, Maxim; Birkelund, Yngve; Senger, Kim; Bergh, Steffen G.
2016-08-01
Broadband (0.001-1000 s) magnetotelluric (MT) data along a crooked profile collected to investigate the geothermal potential on Spitsbergen could not be fully explained by two-dimensional (2D) models; hence we interpret the data with three-dimensional (3D) inversion herein. To better accommodate 3D features and nearby off profile resistivity structures, the full MT impedance tensor data together with the tipper were inverted. As a model control, a detailed bathymetry is systematically incorporated in the inversion. Our results from testing different inversion settings emphasised that appropriately choosing and tuning the starting model, data error floor and the model regularization together are crucial to obtain optimum benefit from MT field data. Through the 3D inversion, we reproduced out of quadrant impedance components and obtained an overall satisfactory data fit (RMS = 1.05). The final 3D resistivity model displays a complex geology of the near surface region (< 1.5 km), which suggests fractures, localized and regional fault systems and igneous intrusions in the Mesozoic platform cover deposits. The Billefjorden fault zone is revealed as a consistent and deep rooted (> 2 km) conductive anomaly, confirming the regional nature of the fault. The fault zone is positioned between two uplifted basement blocks (> 1000 Ωm) of presumably pre-Devonian (Caledonian) metamorphic rocks, and the fault may have been responsible for deformation in the overlying Paleozoic-Mesozoic unit. Upper crustal conductive anomalies (< 10 Ωm) below the Paleozoic-Mesozoic succession in the western part of the 3D model are interpreted as part of a Devonian basin fill. These conductors are laterally and vertically bounded by resistive rocks, suggesting a conducive environment for deep geothermal heat storage. Having this scenario in an area of a known high heat-flow, deep faults and a thinned lithosphere makes the hypothesis on finding a technologically exploitable geothermal resource
Generates 2D Input for DYNA NIKE & TOPAZ
Hallquist, J. O.; Sanford, Larry
1996-07-15
MAZE is an interactive program that serves as an input and two-dimensional mesh generator for DYNA2D, NIKE2D, TOPAZ2D, and CHEMICAL TOPAZ2D. MAZE also generates a basic template for ISLAND input. MAZE has been applied to the generation of input data to study the response of two-dimensional solids and structures undergoing finite deformations under a wide variety of large deformation transient dynamic and static problems and heat transfer analyses.
MAZE96. Generates 2D Input for DYNA NIKE & TOPAZ
Sanford, L.; Hallquist, J.O.
1992-02-24
MAZE is an interactive program that serves as an input and two-dimensional mesh generator for DYNA2D, NIKE2D, TOPAZ2D, and CHEMICAL TOPAZ2D. MAZE also generates a basic template for ISLAND input. MAZE has been applied to the generation of input data to study the response of two-dimensional solids and structures undergoing finite deformations under a wide variety of large deformation transient dynamic and static problems and heat transfer analyses.
NIKE2D96. Static & Dynamic Response of 2D Solids
Raboin, P.; Engelmann, B.; Halquist, J.O.
1992-01-24
NIKE2D is an implicit finite-element code for analyzing the finite deformation, static and dynamic response of two-dimensional, axisymmetric, plane strain, and plane stress solids. The code is fully vectorized and available on several computing platforms. A number of material models are incorporated to simulate a wide range of material behavior including elasto-placicity, anisotropy, creep, thermal effects, and rate dependence. Slideline algorithms model gaps and sliding along material interfaces, including interface friction, penetration and single surface contact. Interactive-graphics and rezoning is included for analyses with large mesh distortions. In addition to quasi-Newton and arc-length procedures, adaptive algorithms can be defined to solve the implicit equations using the solution language ISLAND. Each of these capabilities and more make NIKE2D a robust analysis tool.
H.K. Park, N.C. Luhmann, Jr, A.J.H. Donné, C.W. Domier, T. Munsat, M.J. Van de Pol, and the TEXTOR Team
2007-11-26
Two dimensional (2-D) images of electron temperature fluctuations with high temporal and spatial resolution have been employed to study the sawtooth oscillation (m/n=1/1 mode) in Toroidal EXperiment for Technology Oriented Research (TEXTOR) tokamak plasmas. 2-D imaging data revealed new physics which were not available in previous studies based on the 1-D electron temperature measurement and X-ray tomography. Review of the physics of the sawtooth oscillation is given by comparative studies with prominent theoretical models suggest that a new physics paradigm is needed to describe the reconnection physics of the sawtooth oscillation. The new insights are: A pressure driven instability (not a ballooning mode) leads to the X-point reconnection process. The reconnection process is identified as a random 3-D local reconnection process with a helical structure. The reconnection time scale is similar for different types of sawtooth oscillation ("kink" and tearing type) and is significantly faster than the resistive time scale. Heat flow from the core to the outside of the inversion radius during the reconnection process is highly collective rather than stochastic.
Ramig, Keith; Subramaniam, Gopal; Karimi, Sasan; Szalda, David J; Ko, Allen; Lam, Aaron; Li, Jeffrey; Coaderaj, Ani; Cavdar, Leyla; Bogdan, Lukasz; Kwon, Kitae; Greer, Edyta M
2016-04-15
A series of 2,4-disubstituted 1H-1-benzazepines, 2a-d, 4, and 6, were studied, varying both the substituents at C2 and C4 and at the nitrogen atom. The conformational inversion (ring-flip) and nitrogen-atom inversion (N-inversion) energetics were studied by variable-temperature NMR spectroscopy and computations. The steric bulk of the nitrogen-atom substituent was found to affect both the conformation of the azepine ring and the geometry around the nitrogen atom. Also affected were the Gibbs free energy barriers for the ring-flip and the N-inversion. When the nitrogen-atom substituent was alkyl, as in 2a-c, the geometry of the nitrogen atom was nearly planar and the azepine ring was highly puckered; the result was a relatively high-energy barrier to ring-flip and a low barrier to N-inversion. Conversely, when the nitrogen-atom substituent was a hydrogen atom, as in 2d, 4, and 6, the nitrogen atom was significantly pyramidalized and the azepine ring was less puckered; the result here was a relatively high energy barrier to N-inversion and a low barrier to ring-flip. In these N-unsubstituted compounds, it was found computationally that the lowest-energy stereodynamic process was ring-flip coupled with N-inversion, as N-inversion alone had a much higher energy barrier.
Wan, Tsai-Wen; Khokhlova, Olga E; Iwao, Yasuhisa; Higuchi, Wataru; Hung, Wei-Chun; Reva, Ivan V; Singur, Olga A; Gostev, Vladimir V; Sidorenko, Sergey V; Peryanova, Olga V; Salmina, Alla B; Reva, Galina V; Teng, Lee-Jene; Yamamoto, Tatsuo
2016-01-01
ST8/SCCmecIV community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has been a common threat, with large USA300 epidemics in the United States. The global geographical structure of ST8/SCCmecIV has not yet been fully elucidated. We herein determined the complete circular genome sequence of ST8/SCCmecIVc strain OC8 from Siberian Russia. We found that 36.0% of the genome was inverted relative to USA300. Two IS256, oppositely oriented, at IS256-enriched hot spots were implicated with the one-megabase genomic inversion (MbIN) and vSaβ split. The behavior of IS256 was flexible: its insertion site (att) sequences on the genome and junction sequences of extrachromosomal circular DNA were all divergent, albeit with fixed sizes. A similar multi-IS256 system was detected, even in prevalent ST239 healthcare-associated MRSA in Russia, suggesting IS256's strong transmission potential and advantage in evolution. Regarding epidemiology, all ST8/SCCmecIVc strains from European, Siberian, and Far Eastern Russia, examined had MbIN, and geographical expansion accompanied divergent spa types and resistance to fluoroquinolones, chloramphenicol, and often rifampicin. Russia ST8/SCCmecIVc has been associated with life-threatening infections such as pneumonia and sepsis in both community and hospital settings. Regarding virulence, the OC8 genome carried a series of toxin and immune evasion genes, a truncated giant surface protein gene, and IS256 insertion adjacent to a pan-regulatory gene. These results suggest that unique single ST8/spa1(t008)/SCCmecIVc CA-MRSA (clade, Russia ST8-IVc) emerged in Russia, and this was followed by large geographical expansion, with MbIN as an epidemiological marker, and fluoroquinolone resistance, multiple virulence factors, and possibly a multi-IS256 system as selective advantages.
Pouliot, Yves; Lamarche, Benoît; Beaulieu, Jean-François; Hould, Frédéric S.; Richard, Denis; Tchernof, André; Levy, Emile
2016-01-01
Context Lactoferrin (Lf) is an important protein found on mucosal surfaces, within neutrophils and various cells, and in biological fluids. It displays multiple functions, including iron-binding as well as antimicrobial, immunomodulatory and anti-inflammatory activities. Although Lf ingestion has been suggested to cause adiposity reduction in murine models and humans, its relationship with insulin resistance (IR) has not been studied thoroughly. Objective To establish the association between circulating Lf levels, glucose status and blood lipid/lipoprotein profile. Methods Two independent cohorts were examined: lean to moderately obese women admitted for gynecological surgery (n = 53) and severely obese subjects undergoing biliopancreatic diversion (n = 62). Results Although body mass index (BMI) and total body fat mass were negatively associated with Lf, IR (assessed by the HOMA-IR index) was positively and independently associated with plasma Lf concentrations of the first cohort of lean to moderately obese women. These observations were validated in the second cohort in view of the positive correlation between plasma Lf concentrations and the HOMA-IR index, but without a significant association with the body mass index (BMI) of severely obese subjects. In subsamples of severely obese subjects matched for sex, age and BMI, but with either relatively low (1.89 ± 0.73) or high (13.77 ± 8.81) IR states (according to HOMA-IR), higher plasma Lf levels were noted in insulin-resistant vs insulin-sensitive subjects (P<0.05). Finally, Lf levels were significantly higher in lean to moderately obese women than in severely obese subjects (P<0.05). Conclusion Our findings revealed that plasma Lf levels are strongly associated with IR independently of total adiposity, which suggests an intriguing Lf regulation mechanism in conditions of obesity and IR. PMID:27902700
2D Potential theory using complex functions and conformal mapping
NASA Astrophysics Data System (ADS)
Le Maire, Pauline; Munschy, Marc
2016-04-01
For infinitely horizontally extended bodies, functions that describe potential and field equations (gravity and magnetics) outside bodies are 2D and harmonic. The consequence of this property is that potential and field equations can be written as complex analytic functions. We define these complex functions whose real part is the commonly used real function and imaginary part is its Hilbert transform. Using data or synthetic cases the transformation is easily performed in the Fourier domain by setting to zero all values for negative frequencies. Written as complex functions of the complex variable, equations of potential and field in gravity and magnetics for different kinds of geometries are simple and correspond to powers of the inverse of the distance. For example, it is easily shown that for a tilted dyke, the dip and the apparent inclination have the same effect on the function and consequently that it is not possible, with data, to compute one of both values without knowing the other. Conformal mapping is an original way to display potential field functions. Considering that the complex variable corresponds to the real axis, complex potential field functions resume to a limaçon, a curve formed by the path of the point fixed to a circle when that circle rolls around the outside of another circle. For example, the point corresponding to the maximum distance to the origin of the complex magnetic field due to a cylinder, corresponds to the maximum of the analytic signal as defined by Nabighan in 1972 and its phase corresponds to the apparent inclination. Several applications are shown in different geological contexts using aeromagnetic data.
Sparse CSEM inversion driven by seismic coherence
NASA Astrophysics Data System (ADS)
Guo, Zhenwei; Dong, Hefeng; Kristensen, Åge
2016-12-01
Marine controlled source electromagnetic (CSEM) data inversion for hydrocarbon exploration is often challenging due to high computational cost, physical memory requirement and low resolution of the obtained resistivity map. This paper aims to enhance both the speed and resolution of CSEM inversion by introducing structural geological information in the inversion algorithm. A coarse mesh is generated for Occam’s inversion, where the parameters are fewer than in the fine regular mesh. This sparse mesh is defined as a coherence-based irregular (IC) sparse mesh, which is based on vertices extracted from available geological information. Inversion results on synthetic data illustrate that the IC sparse mesh has a smaller inversion computational cost compared to the regular dense (RD) mesh. It also has a higher resolution than with a regular sparse (RS) mesh for the same number of estimated parameters. In order to study how the IC sparse mesh reduces the computational time, four different meshes are generated for Occam’s inversion. As a result, an IC sparse mesh can reduce the computational cost while it keeps the resolution as good as a fine regular mesh. The IC sparse mesh reduces the computational cost of the matrix operation for model updates. When the number of estimated parameters reduces to a limited value, the computational cost is independent of the number of parameters. For a testing model with two resistive layers, the inversion result using an IC sparse mesh has higher resolution in both horizontal and vertical directions. Overall, the model representing significant geological information in the IC mesh can improve the resolution of the resistivity models obtained from inversion of CSEM data.
CYP2D7 Sequence Variation Interferes with TaqMan CYP2D6*15 and *35 Genotyping
Riffel, Amanda K.; Dehghani, Mehdi; Hartshorne, Toinette; Floyd, Kristen C.; Leeder, J. Steven; Rosenblatt, Kevin P.; Gaedigk, Andrea
2016-01-01
TaqMan™ genotyping assays are widely used to genotype CYP2D6, which encodes a major drug metabolizing enzyme. Assay design for CYP2D6 can be challenging owing to the presence of two pseudogenes, CYP2D7 and CYP2D8, structural and copy number variation and numerous single nucleotide polymorphisms (SNPs) some of which reflect the wild-type sequence of the CYP2D7 pseudogene. The aim of this study was to identify the mechanism causing false-positive CYP2D6*15 calls and remediate those by redesigning and validating alternative TaqMan genotype assays. Among 13,866 DNA samples genotyped by the CompanionDx® lab on the OpenArray platform, 70 samples were identified as heterozygotes for 137Tins, the key SNP of CYP2D6*15. However, only 15 samples were confirmed when tested with the Luminex xTAG CYP2D6 Kit and sequencing of CYP2D6-specific long range (XL)-PCR products. Genotype and gene resequencing of CYP2D6 and CYP2D7-specific XL-PCR products revealed a CC>GT dinucleotide SNP in exon 1 of CYP2D7 that reverts the sequence to CYP2D6 and allows a TaqMan assay PCR primer to bind. Because CYP2D7 also carries a Tins, a false-positive mutation signal is generated. This CYP2D7 SNP was also responsible for generating false-positive signals for rs769258 (CYP2D6*35) which is also located in exon 1. Although alternative CYP2D6*15 and *35 assays resolved the issue, we discovered a novel CYP2D6*15 subvariant in one sample that carries additional SNPs preventing detection with the alternate assay. The frequency of CYP2D6*15 was 0.1% in this ethnically diverse U.S. population sample. In addition, we also discovered linkage between the CYP2D7 CC>GT dinucleotide SNP and the 77G>A (rs28371696) SNP of CYP2D6*43. The frequency of this tentatively functional allele was 0.2%. Taken together, these findings emphasize that regardless of how careful genotyping assays are designed and evaluated before being commercially marketed, rare or unknown SNPs underneath primer and/or probe regions can impact
CYP2D7 Sequence Variation Interferes with TaqMan CYP2D6 (*) 15 and (*) 35 Genotyping.
Riffel, Amanda K; Dehghani, Mehdi; Hartshorne, Toinette; Floyd, Kristen C; Leeder, J Steven; Rosenblatt, Kevin P; Gaedigk, Andrea
2015-01-01
TaqMan™ genotyping assays are widely used to genotype CYP2D6, which encodes a major drug metabolizing enzyme. Assay design for CYP2D6 can be challenging owing to the presence of two pseudogenes, CYP2D7 and CYP2D8, structural and copy number variation and numerous single nucleotide polymorphisms (SNPs) some of which reflect the wild-type sequence of the CYP2D7 pseudogene. The aim of this study was to identify the mechanism causing false-positive CYP2D6 (*) 15 calls and remediate those by redesigning and validating alternative TaqMan genotype assays. Among 13,866 DNA samples genotyped by the CompanionDx® lab on the OpenArray platform, 70 samples were identified as heterozygotes for 137Tins, the key SNP of CYP2D6 (*) 15. However, only 15 samples were confirmed when tested with the Luminex xTAG CYP2D6 Kit and sequencing of CYP2D6-specific long range (XL)-PCR products. Genotype and gene resequencing of CYP2D6 and CYP2D7-specific XL-PCR products revealed a CC>GT dinucleotide SNP in exon 1 of CYP2D7 that reverts the sequence to CYP2D6 and allows a TaqMan assay PCR primer to bind. Because CYP2D7 also carries a Tins, a false-positive mutation signal is generated. This CYP2D7 SNP was also responsible for generating false-positive signals for rs769258 (CYP2D6 (*) 35) which is also located in exon 1. Although alternative CYP2D6 (*) 15 and (*) 35 assays resolved the issue, we discovered a novel CYP2D6 (*) 15 subvariant in one sample that carries additional SNPs preventing detection with the alternate assay. The frequency of CYP2D6 (*) 15 was 0.1% in this ethnically diverse U.S. population sample. In addition, we also discovered linkage between the CYP2D7 CC>GT dinucleotide SNP and the 77G>A (rs28371696) SNP of CYP2D6 (*) 43. The frequency of this tentatively functional allele was 0.2%. Taken together, these findings emphasize that regardless of how careful genotyping assays are designed and evaluated before being commercially marketed, rare or unknown SNPs underneath primer
Locative Inversion in Cantonese.
ERIC Educational Resources Information Center
Mok, Sui-Sang
This study investigates the phenomenon of "Locative Inversion" in Cantonese. The term "Locative Inversion" indicates that the locative phrase (LP) syntactic process in Cantonese and the appears at the sentence-initial position and its logical subject occurs postverbally. It is demonstrated that this Locative Inversion is a…
The Xis2d protein of CTnDOT binds to the intergenic region between the mob and tra operons
Hopp, Crystal M.; Gardner, Jeffrey F.; Salyers, Abigail A.
2015-01-01
CTnDOT is a 65kbp integrative and conjugative element (ICE) that carries genes encoding both tetracycline and erythromycin resistances. The Excision operon of this element encodes Xis2c, Xis2d, and Exc proteins involved in the excision of CTnDOT from host chromosomes. These proteins are also required in the complex transcriptional regulation of the divergently transcribed transfer (tra) and mobilization (mob) operons of CTnDOT. Transcription of the tra operon is positively regulated by Xis2c and Xis2d, whereas, transcription of the mob operon is positively regulated by Xis2d and Exc. Xis2d is the only protein that is involved in the excision reaction, as well as the transcriptional regulation of both the mob and tra operons. This paper helps establish how Xis2d binds the DNA in the mob and tra region. Unlike other excisionase proteins, Xis2d binds a region of dyad symmetry. The binding site is located in the intergenic region between the mob and tra promoters, and once bound Xis2d induces a bend in the DNA. Xis2d binding to this region could be the preliminary step for the activation of both operons. Then the other proteins, like Exc, can interact with Xis2d and form higher order complexes. PMID:26212728
Residual lens effects in 2D mode of auto-stereoscopic lenticular-based switchable 2D/3D displays
NASA Astrophysics Data System (ADS)
Sluijter, M.; IJzerman, W. L.; de Boer, D. K. G.; de Zwart, S. T.
2006-04-01
We discuss residual lens effects in multi-view switchable auto-stereoscopic lenticular-based 2D/3D displays. With the introduction of a switchable lenticular, it is possible to switch between a 2D mode and a 3D mode. The 2D mode displays conventional content, whereas the 3D mode provides the sensation of depth to the viewer. The uniformity of a display in the 2D mode is quantified by the quality parameter modulation depth. In order to reduce the modulation depth in the 2D mode, birefringent lens plates are investigated analytically and numerically, by ray tracing. We can conclude that the modulation depth in the 2D mode can be substantially decreased by using birefringent lens plates with a perfect index match between lens material and lens plate. Birefringent lens plates do not disturb the 3D performance of a switchable 2D/3D display.
Differential CYP 2D6 metabolism alters primaquine pharmacokinetics.
Potter, Brittney M J; Xie, Lisa H; Vuong, Chau; Zhang, Jing; Zhang, Ping; Duan, Dehui; Luong, Thu-Lan T; Bandara Herath, H M T; Dhammika Nanayakkara, N P; Tekwani, Babu L; Walker, Larry A; Nolan, Christina K; Sciotti, Richard J; Zottig, Victor E; Smith, Philip L; Paris, Robert M; Read, Lisa T; Li, Qigui; Pybus, Brandon S; Sousa, Jason C; Reichard, Gregory A; Marcsisin, Sean R
2015-04-01
Primaquine (PQ) metabolism by the cytochrome P450 (CYP) 2D family of enzymes is required for antimalarial activity in both humans (2D6) and mice (2D). Human CYP 2D6 is highly polymorphic, and decreased CYP 2D6 enzyme activity has been linked to decreased PQ antimalarial activity. Despite the importance of CYP 2D metabolism in PQ efficacy, the exact role that these enzymes play in PQ metabolism and pharmacokinetics has not been extensively studied in vivo. In this study, a series of PQ pharmacokinetic experiments were conducted in mice with differential CYP 2D metabolism characteristics, including wild-type (WT), CYP 2D knockout (KO), and humanized CYP 2D6 (KO/knock-in [KO/KI]) mice. Plasma and liver pharmacokinetic profiles from a single PQ dose (20 mg/kg of body weight) differed significantly among the strains for PQ and carboxy-PQ. Additionally, due to the suspected role of phenolic metabolites in PQ efficacy, these were probed using reference standards. Levels of phenolic metabolites were highest in mice capable of metabolizing CYP 2D6 substrates (WT and KO/KI 2D6 mice). PQ phenolic metabolites were present in different quantities in the two strains, illustrating species-specific differences in PQ metabolism between the human and mouse enzymes. Taking the data together, this report furthers understanding of PQ pharmacokinetics in the context of differential CYP 2D metabolism and has important implications for PQ administration in humans with different levels of CYP 2D6 enzyme activity.
Synthesis and characterization of 2D molybdenum carbide (MXene)
Halim, Joseph; Kota, Sankalp; Lukatskaya, Maria R.; ...
2016-02-17
Large scale synthesis and delamination of 2D Mo2CT x (where T is a surface termination group) has been achieved by selectively etching gallium from the recently discovered nanolaminated, ternary transition metal carbide Mo2Ga2C. Different synthesis and delamination routes result in different flake morphologies. The resistivity of free-standing Mo2CT x films increases by an order of magnitude as the temperature is reduced from 300 to 10 K, suggesting semiconductor-like behavior of this MXene, in contrast to Ti3C2T x which exhibits metallic behavior. At 10 K, the magnetoresistance is positive. Additionally, changes in electronic transport are observed upon annealing of the films.more » When 2 μm thick films are tested as electrodes in supercapacitors, capacitances as high as 700 F cm–3 in a 1 m sulfuric acid electrolyte and high capacity retention for at least 10,000 cycles at 10 A g–1 are obtained. Free-standing Mo2CT x films, with ≈8 wt% carbon nanotubes, perform well when tested as an electrode material for Li-ions, especially at high rates. In conclusion, at 20 and 131 C cycling rates, stable reversible capacities of 250 and 76 mAh g–1, respectively, are achieved for over 1000 cycles.« less
Mechanical characterization of 2D, 2D stitched, and 3D braided/RTM materials
NASA Technical Reports Server (NTRS)
Deaton, Jerry W.; Kullerd, Susan M.; Portanova, Marc A.
1993-01-01
Braided composite materials have potential for application in aircraft structures. Fuselage frames, floor beams, wing spars, and stiffeners are examples where braided composites could find application if cost effective processing and damage tolerance requirements are met. Another important consideration for braided composites relates to their mechanical properties and how they compare to the properties of composites produced by other textile composite processes being proposed for these applications. Unfortunately, mechanical property data for braided composites do not appear extensively in the literature. Data are presented in this paper on the mechanical characterization of 2D triaxial braid, 2D triaxial braid plus stitching, and 3D (through-the-thickness) braid composite materials. The braided preforms all had the same graphite tow size and the same nominal braid architectures, (+/- 30 deg/0 deg), and were resin transfer molded (RTM) using the same mold for each of two different resin systems. Static data are presented for notched and unnotched tension, notched and unnotched compression, and compression after impact strengths at room temperature. In addition, some static results, after environmental conditioning, are included. Baseline tension and compression fatigue results are also presented, but only for the 3D braided composite material with one of the resin systems.
Design and implementation of a 2-D endoscopic optical fiber scanner
NASA Astrophysics Data System (ADS)
Liu, Zhihai; Fu, Ling; Gao, Fei; Zhang, Xiongbo
2008-12-01
We have designed a small type of endoscopic 2D fiber scanner probe to incorporate OCT with endoscopy imaging. The new probe consists with two piezoelectric ceramics plated with electrode, a conductive thin-film with non-inverse piezoelectric effect and a piece of nude fiber with coating layers removed. To accomplish the scanning, the only thing need to be done is to drive the two piezoelectric ceramic sheets which provides simpler structure and at the same time minimizes the probe effectively. Here we have obtained some preliminary results and verified the feasibility of the program.
Fabrication of 2D and 3D photonic structures using laser lithography
NASA Astrophysics Data System (ADS)
Gaso, P.; Jandura, D.; Pudis, D.
2016-12-01
In this paper we demonstrate possibilities of three-dimensional (3D) printing technology based on two photon polymerization. We used three-dimensional dip-in direct-laser-writing (DLW) optical lithography to fabricate 2D and 3D optical structures for optoelectronics and for optical sensing applications. DLW lithography allows us use a non conventional way how to couple light into the waveguide structure. We prepared ring resonator and we investigated its transmission spectral characteristic. We present 3D inverse opal structure from its design to printing and scanning electron microscope (SEM) imaging. Finally, SEM images of some prepared photonic crystal structures were performed.
NASA Astrophysics Data System (ADS)
Huisman, J. A.; Rings, J.; Vrugt, J. A.; Sorg, J.; Vereecken, H.
2010-01-01
SummaryCoupled hydrogeophysical inversion aims to improve the use of geophysical data for hydrological model parameterization. Several numerical studies have illustrated the feasibility and advantages of a coupled approach. However, there is still a lack of studies that apply the coupled inversion approach to actual field data. In this paper, we test the feasibility of coupled hydrogeophysical inversion for determining the hydraulic properties of a model dike using measurements of electrical resistance tomography (ERT). Our analysis uses a two-dimensional (2D) finite element hydrological model (HYDRUS-2D) coupled to a 2.5D finite element electrical resistivity code (CRMOD), and includes explicit recognition of parameter uncertainty by using a Bayesian and multiple criteria framework with the DREAM and AMALGAM population based search algorithms. To benchmark our inversion results, soil hydraulic properties determined from ERT data are compared with those separately obtained from detailed in situ soil water content measurements using Time Domain Reflectometry (TDR). Our most important results are as follows. (1) TDR and ERT data theoretically contain sufficient information to resolve most of the soil hydraulic properties, (2) the DREAM-derived posterior distributions of the hydraulic parameters are quite similar when estimated separately using TDR and ERT measurements for model calibration, (3) among all parameters, the saturated hydraulic conductivity of the dike material is best constrained, (4) the saturation exponent of the petrophysical model is well defined, and matches independently measured values, (5) measured ERT data sufficiently constrain model predictions of water table dynamics within the model dike. This finding demonstrates an innate ability of ERT data to provide accurate hydrogeophysical parameterizations for flooding events, which is of particular relevance to dike management, and (6) the AMALGAM-derived Pareto front demonstrates trade-off in the
Computational Screening of 2D Materials for Photocatalysis.
Singh, Arunima K; Mathew, Kiran; Zhuang, Houlong L; Hennig, Richard G
2015-03-19
Two-dimensional (2D) materials exhibit a range of extraordinary electronic, optical, and mechanical properties different from their bulk counterparts with potential applications for 2D materials emerging in energy storage and conversion technologies. In this Perspective, we summarize the recent developments in the field of solar water splitting using 2D materials and review a computational screening approach to rapidly and efficiently discover more 2D materials that possess properties suitable for solar water splitting. Computational tools based on density-functional theory can predict the intrinsic properties of potential photocatalyst such as their electronic properties, optical absorbance, and solubility in aqueous solutions. Computational tools enable the exploration of possible routes to enhance the photocatalytic activity of 2D materials by use of mechanical strain, bias potential, doping, and pH. We discuss future research directions and needed method developments for the computational design and optimization of 2D materials for photocatalysis.
NASA Astrophysics Data System (ADS)
Dlugosch, Raphael; Günther, Thomas; Müller-Petke, Mike; Yaramanci, Ugur
2014-05-01
We present recent studies on the characterization of shallow aquifers using Nuclear Magnetic Resonance (NMR). NMR can help to gather detailed information about the water content and pore size related NMR relaxation time, of porous and water saturated material. The field application of surface NMR uses large wire loops placed at the surface of the Earth allows imaging the subsurface down to around hundred meters. First, a sophisticated inversion scheme is presented to simultaneously determine the two-dimensional (2D) distribution of the water content and the NMR relaxation time (T2*) in the subsurface from a surface NMR survey. The outstanding features of the new inversion scheme are its robustness to noisy data and the potential to distinguish aquifers of different lithology due to their specific NMR relaxation time. The successful application of the inversion scheme is demonstrated on two field cases both characterized by channel structures in the glacial sediments of Northern Germany. Second, we revise the prediction of hydraulic conductivity from NMR measurements for coarse-grained and unconsolidated sediments, commonly found in shallow aquifers. The presented Kozeny-Godefroy model replaces the empirical factors in known relations with physical, structural, and intrinsic NMR parameters. It additionally accounts for bulk water relaxation and is not limited to fast diffusion conditions. This improves the prediction of the hydraulic conductivity for clay-free sediments with grain sizes larger than medium sand. The model is validated by laboratory measurements on glass beads and sand samples. Combining the new inversion scheme and petrophysical model allows 2D imaging of the hydraulic conductivity in the subsurface from a surface NMR survey.
Synthetic Covalent and Non-Covalent 2D Materials.
Boott, Charlotte E; Nazemi, Ali; Manners, Ian
2015-11-16
The creation of synthetic 2D materials represents an attractive challenge that is ultimately driven by their prospective uses in, for example, electronics, biomedicine, catalysis, sensing, and as membranes for separation and filtration. This Review illustrates some recent advances in this diverse field with a focus on covalent and non-covalent 2D polymers and frameworks, and self-assembled 2D materials derived from nanoparticles, homopolymers, and block copolymers.
Magnetotelluric inversion via reverse time migration algorithm of seismic data
Ha, Taeyoung . E-mail: tyha@math.snu.ac.kr; Shin, Changsoo . E-mail: css@model.snu.ac.kr
2007-07-01
We propose a new algorithm for two-dimensional magnetotelluric (MT) inversion. Our algorithm is an MT inversion based on the steepest descent method, borrowed from the backpropagation technique of seismic inversion or reverse time migration, introduced in the middle 1980s by Lailly and Tarantola. The steepest descent direction can be calculated efficiently by using the symmetry of numerical Green's function derived from a mixed finite element method proposed by Nedelec for Maxwell's equation, without calculating the Jacobian matrix explicitly. We construct three different objective functions by taking the logarithm of the complex apparent resistivity as introduced in the recent waveform inversion algorithm by Shin and Min. These objective functions can be naturally separated into amplitude inversion, phase inversion and simultaneous inversion. We demonstrate our algorithm by showing three inversion results for synthetic data.
Magnetotelluric inversion via reverse time migration algorithm of seismic data
NASA Astrophysics Data System (ADS)
Ha, Taeyoung; Shin, Changsoo
2007-07-01
We propose a new algorithm for two-dimensional magnetotelluric (MT) inversion. Our algorithm is an MT inversion based on the steepest descent method, borrowed from the backpropagation technique of seismic inversion or reverse time migration, introduced in the middle 1980s by Lailly and Tarantola. The steepest descent direction can be calculated efficiently by using the symmetry of numerical Green's function derived from a mixed finite element method proposed by Nédélec for Maxwell's equation, without calculating the Jacobian matrix explicitly. We construct three different objective functions by taking the logarithm of the complex apparent resistivity as introduced in the recent waveform inversion algorithm by Shin and Min. These objective functions can be naturally separated into amplitude inversion, phase inversion and simultaneous inversion. We demonstrate our algorithm by showing three inversion results for synthetic data.
Baron, A; Montagne, A; Cassé, F; Launay, S; Maubert, E; Ali, C; Vivien, D
2010-05-01
Although the molecular bases of its actions remain debated, tissue-type plasminogen activator (tPA) is a paradoxical brain protease, as it favours some learning/memory processes, but increases excitotoxic neuronal death. Here, we show that, in cultured cortical neurons, tPA selectively promotes NR2D-containing N-methyl-D-aspartate receptor (NMDAR)-dependent activation. We show that tPA-mediated signalling and neurotoxicity through the NMDAR are blocked by co-application of an NR2D antagonist (phenanthrene derivative (2S(*), 3R(*))-1-(phenanthrene-2-carbonyl)piperazine-2,3-dicarboxylic acid, PPDA) or knockdown of neuronal NR2D expression. In sharp contrast with cortical neurons, hippocampal neurons do not exhibit NR2D both in vitro and in vivo and are consequently resistant to tPA-promoted NMDAR-mediated neurotoxicity. Moreover, we have shown that activation of synaptic NMDAR prevents further tPA-dependent NMDAR-mediated neurotoxicity and sensitivity to PPDA. This study shows that the earlier described pro-neurotoxic effect of tPA is mediated by NR2D-containing NMDAR-dependent extracellular signal-regulated kinase activation, a deleterious effect prevented by synaptic pre-activation.
Quasi 2D Materials: Raman Nanometrology and Thermal Management Applications
NASA Astrophysics Data System (ADS)
Shahil, Khan Mohammad Farhan
Quasi two-dimensional (2D) materials obtained by the "graphene-like" exfoliation attracted tremendous attention. Such materials revealed unique electronic, thermal and optical properties, which can be potentially used in electronics, thermal management and energy conversion. This dissertation research addresses two separate but synergetic problems: (i) preparation and optical characterization of quasi-2D films of the bismuth-telluride (Bi 2Te3) family of materials, which demonstrate both thermoelectric and topological insulator properties; and (ii) investigation of thermal properties of composite materials prepared with graphene and few-layer graphene (FLG). The first part of dissertation reports properties of the exfoliated few-quintuple layers of Bi2Te3, Bi2Se3 and Sb 2Te3. Both non-resonant and resonant Raman scattering spectra have been investigated. It was found that the crystal symmetry breaking in few-quintuple films results in appearance of A1u-symmetry Raman peaks, which are not active in the bulk crystals. The scattering spectra measured under the 633-nm wavelength excitation reveals a number of resonant features, which could be used for analysis of the electronic and phonon processes in these materials. The obtained results help to understand the physical mechanisms of Raman scattering in the few-quintuple-thick films and can be used for nanometrology of topological insulator films on various substrates. The second part of the dissertation is dedicated to investigation of properties of composite materials prepared with graphene and FLG. It was found that the optimized mixture of graphene and multilayer graphene---produced by the high-yield inexpensive liquid-phase-exfoliation technique---can lead to an extremely strong enhancement of the cross-plane thermal conductivity K of the composite. The "laser flash" measurements revealed a record-high enhancement of K by 2300 % in the graphene-based polymer at the filler loading fraction f =10 vol. %. It was
Epitaxial 2D SnSe2/ 2D WSe2 van der Waals Heterostructures.
Aretouli, Kleopatra Emmanouil; Tsoutsou, Dimitra; Tsipas, Polychronis; Marquez-Velasco, Jose; Aminalragia Giamini, Sigiava; Kelaidis, Nicolaos; Psycharis, Vassilis; Dimoulas, Athanasios
2016-09-07
van der Waals heterostructures of 2D semiconductor materials can be used to realize a number of (opto)electronic devices including tunneling field effect devices (TFETs). It is shown in this work that high quality SnSe2/WSe2 vdW heterostructure can be grown by molecular beam epitaxy on AlN(0001)/Si(111) substrates using a Bi2Se3 buffer layer. A valence band offset of 0.8 eV matches the energy gap of SnSe2 in such a way that the VB edge of WSe2 and the CB edge of SnSe2 are lined up, making this materials combination suitable for (nearly) broken gap TFETs.
NASA Astrophysics Data System (ADS)
Chen, Xiangbin; Yan, Jiayong
2016-08-01
Two parallel NW-trending magnetotelluric (MT) profiles were placed perpendicularly to the main structures of the Anqing-Guichi ore district, one of the seven ore districts in the middle-lower Yangtze River metallogenic belt of eastern China. In October-December 2013, the MT data acquisition was carried out at 117 sites with 0.5-1 km site spacing. The MT data has a good quality in the frequency range between 320 and 0.01 Hz. The dimensionality analysis and 2D resistivity inversion results indicate that: (1) the deep of the ore district with three-dimensional structural characteristics, but two-dimensional structural characteristics for shallow; (2) there is a clear correlation between resistivity and the main geological units of the ore district, as well as correlation with mapped surface faults; (3) the Gandan deep fault (GDF) and Jiangnan deep fault (JNF) extend from the surface to 10 km deep, with dip of NW45°, and dip angles larger than 60°. A series of NE-trending acidic intrusive rocks were controlled by the GDF.
NASA Astrophysics Data System (ADS)
Magarill, L. I.; Entin, M. V.
2016-12-01
The electron absorption and the edge photocurrent of a 2D topological insulator are studied for transitions between edge states to 2D states. The circular polarized light is found to produce the edge photocurrent, the direction of which is determined by light polarization and edge orientation. It is shown that the edge-state current is found to exceed the 2D current owing to the topological protection of the edge states.
2-D MHD numerical simulations of EML plasma armatures with ablation
NASA Astrophysics Data System (ADS)
Boynton, G. C.; Huerta, M. A.; Thio, Y. C.
1993-01-01
We use a 2-D) resistive MHD code to simulate an EML plasma armature. The energy equation includes Ohmic heating, radiation heat transport and the ideal gas equation of state, allowing for variable ionization using the Saha equations. We calculate rail ablation taking into account the flow of heat into the interior of the rails. Our simulations show the development of internal convective flows and secondary arcs. We use an explicit Flux Corrected Transport algorithm to advance all quantities in time.
MEERSCHAERT, MARK M.; STRAKA, PETER
2013-01-01
The inverse stable subordinator provides a probability model for time-fractional differential equations, and leads to explicit solution formulae. This paper reviews properties of the inverse stable subordinator, and applications to a variety of problems in mathematics and physics. Several different governing equations for the inverse stable subordinator have been proposed in the literature. This paper also shows how these equations can be reconciled. PMID:25045216
Energy Efficiency of D2D Multi-User Cooperation.
Zhang, Zufan; Wang, Lu; Zhang, Jie
2017-03-28
The Device-to-Device (D2D) communication system is an important part of heterogeneous networks. It has great potential to improve spectrum efficiency, throughput and energy efficiency cooperation of multiple D2D users with the advantage of direct communication. When cooperating, D2D users expend extraordinary energy to relay data to other D2D users. Hence, the remaining energy of D2D users determines the life of the system. This paper proposes a cooperation scheme for multiple D2D users who reuse the orthogonal spectrum and are interested in the same data by aiming to solve the energy problem of D2D users. Considering both energy availability and the Signal to Noise Ratio (SNR) of each D2D user, the Kuhn-Munkres algorithm is introduced in the cooperation scheme to solve relay selection problems. Thus, the cooperation issue is transformed into a maximum weighted matching (MWM) problem. In order to enhance energy efficiency without the deterioration of Quality of Service (QoS), the link outage probability is derived according to the Shannon Equation by considering the data rate and delay. The simulation studies the relationships among the number of cooperative users, the length of shared data, the number of data packets and energy efficiency.
Integrating Mobile Multimedia into Textbooks: 2D Barcodes
ERIC Educational Resources Information Center
Uluyol, Celebi; Agca, R. Kagan
2012-01-01
The major goal of this study was to empirically compare text-plus-mobile phone learning using an integrated 2D barcode tag in a printed text with three other conditions described in multimedia learning theory. The method examined in the study involved modifications of the instructional material such that: a 2D barcode was used near the text, the…
Efficient Visible Quasi-2D Perovskite Light-Emitting Diodes.
Byun, Jinwoo; Cho, Himchan; Wolf, Christoph; Jang, Mi; Sadhanala, Aditya; Friend, Richard H; Yang, Hoichang; Lee, Tae-Woo
2016-09-01
Efficient quasi-2D-structure perovskite light-emitting diodes (4.90 cd A(-1) ) are demonstrated by mixing a 3D-structured perovskite material (methyl ammonium lead bromide) and a 2D-structured perovskite material (phenylethyl ammonium lead bromide), which can be ascribed to better film uniformity, enhanced exciton confinement, and reduced trap density.
Adaptation algorithms for 2-D feedforward neural networks.
Kaczorek, T
1995-01-01
The generalized weight adaptation algorithms presented by J.G. Kuschewski et al. (1993) and by S.H. Zak and H.J. Sira-Ramirez (1990) are extended for 2-D madaline and 2-D two-layer feedforward neural nets (FNNs).
Regulation of ligands for the NKG2D activating receptor
Raulet, David H.; Gasser, Stephan; Gowen, Benjamin G.; Deng, Weiwen; Jung, Heiyoun
2014-01-01
NKG2D is an activating receptor expressed by all NK cells and subsets of T cells. It serves as a major recognition receptor for detection and elimination of transformed and infected cells and participates in the genesis of several inflammatory diseases. The ligands for NKG2D are self-proteins that are induced by pathways that are active in certain pathophysiological states. NKG2D ligands are regulated transcriptionally, at the level of mRNA and protein stability, and by cleavage from the cell surface. In some cases, ligand induction can be attributed to pathways that are activated specifically in cancer cells or infected cells. We review the numerous pathways that have been implicated in the regulation of NKG2D ligands, discuss the pathologic states in which those pathways are likely to act, and attempt to synthesize the findings into general schemes of NKG2D ligand regulation in NK cell responses to cancer and infection. PMID:23298206
2D materials and van der Waals heterostructures.
Novoselov, K S; Mishchenko, A; Carvalho, A; Castro Neto, A H
2016-07-29
The physics of two-dimensional (2D) materials and heterostructures based on such crystals has been developing extremely fast. With these new materials, truly 2D physics has begun to appear (for instance, the absence of long-range order, 2D excitons, commensurate-incommensurate transition, etc.). Novel heterostructure devices--such as tunneling transistors, resonant tunneling diodes, and light-emitting diodes--are also starting to emerge. Composed from individual 2D crystals, such devices use the properties of those materials to create functionalities that are not accessible in other heterostructures. Here we review the properties of novel 2D crystals and examine how their properties are used in new heterostructure devices.
Estrogen-Induced Cholestasis Leads to Repressed CYP2D6 Expression in CYP2D6-Humanized Mice.
Pan, Xian; Jeong, Hyunyoung
2015-07-01
Cholestasis activates bile acid receptor farnesoid X receptor (FXR) and subsequently enhances hepatic expression of small heterodimer partner (SHP). We previously demonstrated that SHP represses the transactivation of cytochrome P450 2D6 (CYP2D6) promoter by hepatocyte nuclear factor (HNF) 4α. In this study, we investigated the effects of estrogen-induced cholestasis on CYP2D6 expression. Estrogen-induced cholestasis occurs in subjects receiving estrogen for contraception or hormone replacement, or in susceptible women during pregnancy. In CYP2D6-humanized transgenic (Tg-CYP2D6) mice, cholestasis triggered by administration of 17α-ethinylestradiol (EE2) at a high dose led to 2- to 3-fold decreases in CYP2D6 expression. This was accompanied by increased hepatic SHP expression and subsequent decreases in the recruitment of HNF4α to CYP2D6 promoter. Interestingly, estrogen-induced cholestasis also led to increased recruitment of estrogen receptor (ER) α, but not that of FXR, to Shp promoter, suggesting a predominant role of ERα in transcriptional regulation of SHP in estrogen-induced cholestasis. EE2 at a low dose (that does not cause cholestasis) also increased SHP (by ∼ 50%) and decreased CYP2D6 expression (by 1.5-fold) in Tg-CYP2D6 mice, the magnitude of differences being much smaller than that shown in EE2-induced cholestasis. Taken together, our data indicate that EE2-induced cholestasis increases SHP and represses CYP2D6 expression in Tg-CYP2D6 mice in part through ERα transactivation of Shp promoter.
Synthesis and characterization of 2D molybdenum carbide (MXene)
Halim, Joseph; Kota, Sankalp; Lukatskaya, Maria R.; Naguib, Michael; Zhao, Meng -Qiang; Moon, Eun Ju; Pitock, Jeremy; Nanda, Jagjit; May, Steven J.; Gogotsi, Yury; Barsoum, Michel W.
2016-02-17
Large scale synthesis and delamination of 2D Mo_{2}CT _{x} (where T is a surface termination group) has been achieved by selectively etching gallium from the recently discovered nanolaminated, ternary transition metal carbide Mo_{2}Ga_{2}C. Different synthesis and delamination routes result in different flake morphologies. The resistivity of free-standing Mo_{2}CT _{x} films increases by an order of magnitude as the temperature is reduced from 300 to 10 K, suggesting semiconductor-like behavior of this MXene, in contrast to Ti_{3}C_{2}T _{x} which exhibits metallic behavior. At 10 K, the magnetoresistance is positive. Additionally, changes in electronic transport are observed upon annealing of the films. When 2 μm thick films are tested as electrodes in supercapacitors, capacitances as high as 700 F cm^{–3} in a 1 m sulfuric acid electrolyte and high capacity retention for at least 10,000 cycles at 10 A g^{–1} are obtained. Free-standing Mo_{2}CT _{x} films, with ≈8 wt% carbon nanotubes, perform well when tested as an electrode material for Li-ions, especially at high rates. In conclusion, at 20 and 131 C cycling rates, stable reversible capacities of 250 and 76 mAh g^{–1}, respectively, are achieved for over 1000 cycles.
Force Fluctuations in a 2D Granular Drag Experiment
NASA Astrophysics Data System (ADS)
Geng, Junfei; Behringer, R. P.
2002-11-01
We study fluctuations in the drag force experienced by an object slowly moving through a 2D granular material consisting of bidisperse disks. Slow drag experiments provide a useful way to understand the nature of stress propagation, fluctuations, and slow dynamics in granular materials. Unlike in a liquid, the drag force in a granular material is largely due to the resistance of inhomogeneous and anisotropic ``force chains'', and thus exhibits strong fluctuations. Experiments were carried out in an apparatus similar in spirit to the one by Albert et al.(R. Albert, M.A. Pfeifer, A.L. Barabasi and P. Schiffer, Phys. Rev. Lett. 82), 205 (1999). and we varied the rotation rate (ω=6.3× 10-6 ˜ 8.7× 10-4Hz), the object size (0.744, 0.876, 1.250,1.610,1.930 cm), and the packing fraction of the system. We observed a weak dependence of the mean force on the medium velocity, a rate-invariant power spectrum decaying as ω-2 for large ω (a remarkable resemblance to results by Miller et al.(B. Miller, C. O'Hern and R.P. Behringer, Phys. Rev. Lett. 77), 3110 (1996).), an exponential distribution of avalanche sizes, and a well defined ``Stress Chain Force Constant''. We also show that a simple model adapted after Kahng. et al.(B. Kahng, I. Albert, P. Schiffer and A.L. Barabasi, Phys. Rev. E. 64), 051303 (2001). reproduces many of experimental observations.
NASA Astrophysics Data System (ADS)
Aizebeokhai, Ahzegbobor P.; Oyeyemi, Kehinde D.
2014-12-01
The use of most conventional electrode configurations in electrical resistivity survey is often time consuming and labour intensive, especially when using manual data acquisition systems. Often, data acquisition teams tend to reduce data density so as to speed up field operation thereby reducing the survey cost; but this could significantly degrade the quality and resolution of the inverse models. In the present work, the potential of using the multiple-gradient array, a non-conventional electrode configuration, for practical cost effective and rapid subsurface resistivity and induced polarization mapping was evaluated. The array was used to conduct 2D resistivity and time-domain induced polarization imaging along two traverses in a study site at Ota, southwestern Nigeria. The subsurface was characterised and the main aquifer delineated using the inverse resistivity and chargeability images obtained. The performance of the multiple-gradient array was evaluated by correlating the 2D resistivity and chargeability images with those of the conventional Wenner array as well as the result of some soundings conducted along the same traverses using Schlumberger array. The multiple-gradient array has been found to have the advantage of measurement logistics and improved image resolution over the Wenner array.
Inversion of airborne tensor VLF data using integral equations
NASA Astrophysics Data System (ADS)
Kamm, Jochen; Pedersen, Laust B.
2014-08-01
The Geological Survey of Sweden has been collecting airborne tensor very low frequency data (VLF) over several decades, covering large parts of the country. The data has been an invaluable source of information for identifying conductive structures that can among other things be related to water-filled fault zones, wet sediments that fill valleys or ore mineralizations. Because the method only uses two differently polarized plane waves of very similar frequency, vertical resolution is low and interpretation is in most cases limited to maps that are directly derived from the data. Occasionally, 2-D inversion is carried out along selected profiles. In this paper, we present for the first time a 3-D inversion for tensor VLF data in order to further increase the usefulness of the data set. The inversion is performed using a non-linear conjugate gradient scheme (Polak-Ribière) with an inexact line-search. The gradient is obtained by an algebraic adjoint method that requires one additional forward calculation involving the adjoint system matrix. The forward modelling is based on integral equations with an analytic formulation of the half-space Green's tensor. It avoids typically required Hankel transforms and is particularly amenable to singularity removal prior to the numerical integration over the volume elements. The system is solved iteratively, thus avoiding construction and storage of the dense system matrix. By using fast 3-D Fourier transforms on nested grids, subsequently farther away interactions are represented with less detail and therefore with less computational effort, enabling us to bridge the gap between the relatively short wavelengths of the fields (tens of metres) and the large model dimensions (several square kilometres). We find that the approximation of the fields can be off by several per cent, yet the transfer functions in the air are practically unaffected. We verify our code using synthetic calculations from well-established 2-D methods, and
Xie, Donghao; Ji, Ding-Kun; Zhang, Yue; Cao, Jun; Zheng, Hu; Liu, Lin; Zang, Yi; Li, Jia; Chen, Guo-Rong; James, Tony D; He, Xiao-Peng
2016-08-04
Here we demonstrate that 2D MoS2 can enhance the receptor-targeting and imaging ability of a fluorophore-labelled ligand. The 2D MoS2 has an enhanced working concentration range when compared with graphene oxide, resulting in the improved imaging of both cell and tissue samples.
2-D Coda and Direct Wave Attenuation Tomography in Northern Italy
Morasca, P; Mayeda, K; Gok, R; Phillips, W S; Malagnini, L
2007-10-17
A 1-D coda method was proposed by Mayeda et al. (2003) in order to obtain stable seismic source moment-rate spectra using narrowband coda envelope measurements. That study took advantage of the averaging nature of coda waves to derive stable amplitude measurements taking into account all propagation, site, and Sto-coda transfer function effects. Recently this methodology was applied to micro earthquake data sets from three sub-regions of northern Italy (i.e., western Alps, northern Apennines and eastern Alps). Since the study regions were small, ranging between local-to-near-regional distances, the simple 1-D path assumptions used in the coda method worked very well. The lateral complexity of this region would suggest, however, that a 2-D path correction might provide even better results if the datasets were combined, especially when paths traverse larger distances and complicated regions. The structural heterogeneity of northern Italy makes the region ideal to test the extent to which coda variance can be reduced further by using a 2-D Q tomography technique. The approach we use has been developed by Phillips et al. (2005) and is an extension of previous amplitude ratio techniques to remove source effects from the inversion. The method requires some assumptions such as isotropic source radiation which is generally true for coda waves. Our results are compared against direct Swave inversions for 1/Q and results from both share very similar attenuation features that coincide with known geologic structures. We compare our results with those derived from direct waves as well as some recent results from northern California obtained by Mayeda et al. (2005) which tested the same tomographic methodology applied in this study to invert for 1/Q. We find that 2-D coda path corrections for this region significantly improve upon the 1-D corrections, in contrast to California where only a marginal improvement was observed. We attribute this difference to stronger lateral
Prediction of a strain-tunable 2D Topological Dirac semimetal in monolayers of black phosphorus
NASA Astrophysics Data System (ADS)
Zhang, Xiuwen; Liu, Qihang; Zunger, Alex; Theory Team
2015-03-01
N-dimensional Topological Nonmetals (TNM) such as N = 2D HgTe/CdTe quantum wells or N = 3D Bi2Se3 have a finite (often tiny) band gap between occupied and unoccupied bands, and show conductive Dirac cones in their N-1 dimensional geometric boundaries. On the other hand, examples of topological semimetals (TSM) are known for 3D solids (Cd3As2) where they have Dirac cones in the 3D system itself. Using density functional calculation of bands and the topological invariant Z2 we predict the existence of 2D topological Dirac semimetal in few monolayers of strain tuned black phosphorus (BP), with Dirac cones induced by band inversion. The band structures of few monolayers and bulk crystal of BP under a few percent biaxial and uniaxial strains were calculated using state-of-art electronic structure methods. The critical strain of the transition to TSM was found to decrease as the layer thickness increases. We will discuss the protection of the Dirac cones by the crystalline symmetry in the 2D TSM and the manipulation of crystalline symmetry, which induces further topological phase transitions. Supported by the NSF-DMREF-13-34170.
ERIC Educational Resources Information Center
Bedard, Catherine; Belin, Pascal
2004-01-01
Voice is the carrier of speech but is also an ''auditory face'' rich in information on the speaker's identity and affective state. Three experiments explored the possibility of a ''voice inversion effect,'' by analogy to the classical ''face inversion effect,'' which could support the hypothesis of a voice-specific module. Experiment 1 consisted…
Teaching about Inverse Functions
ERIC Educational Resources Information Center
Esty, Warren
2005-01-01
In their sections on inverses most precalculus texts emphasize an algorithm for finding f [superscript -1] given f. However, inspection of precalculus and calculus texts shows that students will never again use the algorithm, which suggests the textbook emphasis may be misplaced. Inverses appear primarily when equations need to be solved, which…
Dewpoint temperature inversions analyzed
NASA Technical Reports Server (NTRS)
Ashby, W. C.; Bogner, M. A.; Moses, H.
1969-01-01
Dewpoint temperature inversion, with regard to other simultaneous meteorological conditions, was examined to establish the influence of meteorological variables on the variation of dewpoint temperature with height. This report covers instrumentation and available data, all the climatological features of dewpoint inversions, and specific special cases.
Antiproliferative action of menadione and 1,25(OH)2D3 on breast cancer cells.
Marchionatti, Ana M; Picotto, Gabriela; Narvaez, Carmen J; Welsh, Joellen; Tolosa de Talamoni, Nori G
2009-02-01
Calcitriol or 1,25(OH)(2)D(3) is a negative growth regulator of MCF-7 breast cancer cells. The growth arrest is due to apoptosis activation, which involves mitochondrial disruption. This effect is blunted in vitamin D resistant cells (MCF-7(DRes) cells). Menadione (MEN), a glutathione (GSH)-depleting compound, may potentiate antitumoral effects of anticancer drugs. The aim of this study was to investigate whether MEN enhances cellular responsiveness of MCF-7 cells to 1,25(OH)(2)D(3). Cells were cultured and treated with different concentrations of 1,25(OH)(2)D(3)+/-MEN or vehicle for 96 h. GSH levels and the activity of antioxidant enzymes were determined by spectrophotometry and ROS production by flow cytometry. Both drugs decreased growth and enhanced ROS in MCF-7 cells, obtaining the maximal effects when 1,25(OH)(2)D(3) was combined with MEN (P<0.01 vs. Control and vs. each compound alone). MCF-7(DRes) cells were not responsive to 1,25(OH)(2)D(3), but the cell proliferation was slightly inhibited by the combined treatment. Calcitriol and MEN separately enhanced antioxidant enzyme activities, but when they were used in combination, the effect was more pronounced (P<0.05 vs. Control and vs. each compound alone). MEN, calcitriol and the combined treatment decreased GSH levels (P<0.05 vs. Control). The data indicate that MEN potentiates the effect of 1,25(OH)(2)D(3) on growth arrest in MCF-7 cells by oxidative stress and increases the activities of antioxidant enzymes, probably as a compensatory mechanism.
Efficient 2D MRI relaxometry using compressed sensing
NASA Astrophysics Data System (ADS)
Bai, Ruiliang; Cloninger, Alexander; Czaja, Wojciech; Basser, Peter J.
2015-06-01
Potential applications of 2D relaxation spectrum NMR and MRI to characterize complex water dynamics (e.g., compartmental exchange) in biology and other disciplines have increased in recent years. However, the large amount of data and long MR acquisition times required for conventional 2D MR relaxometry limits its applicability for in vivo preclinical and clinical MRI. We present a new MR pipeline for 2D relaxometry that incorporates compressed sensing (CS) as a means to vastly reduce the amount of 2D relaxation data needed for material and tissue characterization without compromising data quality. Unlike the conventional CS reconstruction in the Fourier space (k-space), the proposed CS algorithm is directly applied onto the Laplace space (the joint 2D relaxation data) without compressing k-space to reduce the amount of data required for 2D relaxation spectra. This framework is validated using synthetic data, with NMR data acquired in a well-characterized urea/water phantom, and on fixed porcine spinal cord tissue. The quality of the CS-reconstructed spectra was comparable to that of the conventional 2D relaxation spectra, as assessed using global correlation, local contrast between peaks, peak amplitude and relaxation parameters, etc. This result brings this important type of contrast closer to being realized in preclinical, clinical, and other applications.
2D vs. 3D mammography observer study
NASA Astrophysics Data System (ADS)
Fernandez, James Reza F.; Hovanessian-Larsen, Linda; Liu, Brent
2011-03-01
Breast cancer is the most common type of non-skin cancer in women. 2D mammography is a screening tool to aid in the early detection of breast cancer, but has diagnostic limitations of overlapping tissues, especially in dense breasts. 3D mammography has the potential to improve detection outcomes by increasing specificity, and a new 3D screening tool with a 3D display for mammography aims to improve performance and efficiency as compared to 2D mammography. An observer study using a mammography phantom was performed to compare traditional 2D mammography with this ne 3D mammography technique. In comparing 3D and 2D mammography there was no difference in calcification detection, and mass detection was better in 2D as compared to 3D. There was a significant decrease in reading time for masses, calcifications, and normals in 3D compared to 2D, however, as well as more favorable confidence levels in reading normal cases. Given the limitations of the mammography phantom used, however, a clearer picture in comparing 3D and 2D mammography may be better acquired with the incorporation of human studies in the future.
Wei, Hongjiang; Zhang, Yuyao; Gibbs, Eric; Chen, Nan-Kuei; Wang, Nian; Liu, Chunlei
2017-04-01
Quantitative susceptibility mapping (QSM) measures tissue magnetic susceptibility and typically relies on time-consuming three-dimensional (3D) gradient-echo (GRE) MRI. Recent studies have shown that two-dimensional (2D) multi-slice gradient-echo echo-planar imaging (GRE-EPI), which is commonly used in functional MRI (fMRI) and other dynamic imaging techniques, can also be used to produce data suitable for QSM with much shorter scan times. However, the production of high-quality QSM maps is difficult because data obtained by 2D multi-slice scans often have phase inconsistencies across adjacent slices and strong susceptibility field gradients near air-tissue interfaces. To address these challenges in 2D EPI-based QSM studies, we present a new data processing procedure that integrates 2D and 3D phase processing. First, 2D Laplacian-based phase unwrapping and 2D background phase removal are performed to reduce phase inconsistencies between slices and remove in-plane harmonic components of the background phase. This is followed by 3D background phase removal for the through-plane harmonic components. The proposed phase processing was evaluated with 2D EPI data obtained from healthy volunteers, and compared against conventional 3D phase processing using the same 2D EPI datasets. Our QSM results were also compared with QSM values from time-consuming 3D GRE data, which were taken as ground truth. The experimental results show that this new 2D EPI-based QSM technique can produce quantitative susceptibility measures that are comparable with those of 3D GRE-based QSM across different brain regions (e.g. subcortical iron-rich gray matter, cortical gray and white matter). This new 2D EPI QSM reconstruction method is implemented within STI Suite, which is a comprehensive shareware for susceptibility imaging and quantification. Copyright © 2016 John Wiley & Sons, Ltd.
NKG2D receptor and its ligands in host defense
Lanier, Lewis L.
2015-01-01
NKG2D is an activating receptor expressed on the surface of natural killer (NK) cells, CD8+ T cells, and subsets of CD4+ T cells, iNKT cells, and γδ T cells. In humans NKG2D transmits signals by its association with the DAP10 adapter subunit and in mice alternatively spliced isoforms transmit signals either using DAP10 or DAP12 adapter subunits. Although NKG2D is encoded by a highly conserved gene (KLRK1) with limited polymorphism, the receptor recognizes an extensive repertoire of ligands, encoded by at least 8 genes in humans (MICA, MICB, RAET1E, RAET1G, RAET1H, RAET1I, RAET1L, and RAET1N), some with extensive allelic polymorphism. Expression of the NKG2D ligands is tightly regulated at the level of transcription, translation, and post-translation. In general healthy adult tissues do not express NKG2D glycoproteins on the cell surface, but these ligands can be induced by hyper-proliferation and transformation, as well as when cells are infected by pathogens. Thus, the NKG2D pathway serves a mechanism for the immune system to detect and eliminate cells that have undergone “stress”. Viruses and tumor cells have devised numerous strategies to evade detection by the NKG2D surveillance system and diversification of the NKG2D ligand genes likely has been driven by selective pressures imposed by pathogens. NKG2D provides an attractive target for therapeutics in the treatment of infectious diseases, cancer, and autoimmune diseases. PMID:26041808
NKG2D Receptor and Its Ligands in Host Defense.
Lanier, Lewis L
2015-06-01
NKG2D is an activating receptor expressed on the surface of natural killer (NK) cells, CD8(+) T cells, and subsets of CD4(+) T cells, invariant NKT cells (iNKT), and γδ T cells. In humans, NKG2D transmits signals by its association with the DAP10 adapter subunit, and in mice alternatively spliced isoforms transmit signals either using DAP10 or DAP12 adapter subunits. Although NKG2D is encoded by a highly conserved gene (KLRK1) with limited polymorphism, the receptor recognizes an extensive repertoire of ligands, encoded by at least eight genes in humans (MICA, MICB, RAET1E, RAET1G, RAET1H, RAET1I, RAET1L, and RAET1N), some with extensive allelic polymorphism. Expression of the NKG2D ligands is tightly regulated at the level of transcription, translation, and posttranslation. In general, healthy adult tissues do not express NKG2D glycoproteins on the cell surface, but these ligands can be induced by hyperproliferation and transformation, as well as when cells are infected by pathogens. Thus, the NKG2D pathway serves as a mechanism for the immune system to detect and eliminate cells that have undergone "stress." Viruses and tumor cells have devised numerous strategies to evade detection by the NKG2D surveillance system, and diversification of the NKG2D ligand genes likely has been driven by selective pressures imposed by pathogens. NKG2D provides an attractive target for therapeutics in the treatment of infectious diseases, cancer, and autoimmune diseases.
2-D Versus 3-D Magnetotelluric Data Interpretation
NASA Astrophysics Data System (ADS)
Ledo, Juanjo
2005-09-01
In recent years, the number of publications dealing with the mathematical and physical 3-D aspects of the magnetotelluric method has increased drastically. However, field experiments on a grid are often impractical and surveys are frequently restricted to single or widely separated profiles. So, in many cases we find ourselves with the following question: is the applicability of the 2-D hypothesis valid to extract geoelectric and geological information from real 3-D environments? The aim of this paper is to explore a few instructive but general situations to understand the basics of a 2-D interpretation of 3-D magnetotelluric data and to determine which data subset (TE-mode or TM-mode) is best for obtaining the electrical conductivity distribution of the subsurface using 2-D techniques. A review of the mathematical and physical fundamentals of the electromagnetic fields generated by a simple 3-D structure allows us to prioritise the choice of modes in a 2-D interpretation of responses influenced by 3-D structures. This analysis is corroborated by numerical results from synthetic models and by real data acquired by other authors. One important result of this analysis is that the mode most unaffected by 3-D effects depends on the position of the 3-D structure with respect to the regional 2-D strike direction. When the 3-D body is normal to the regional strike, the TE-mode is affected mainly by galvanic effects, while the TM-mode is affected by galvanic and inductive effects. In this case, a 2-D interpretation of the TM-mode is prone to error. When the 3-D body is parallel to the regional 2-D strike the TE-mode is affected by galvanic and inductive effects and the TM-mode is affected mainly by galvanic effects, making it more suitable for 2-D interpretation. In general, a wise 2-D interpretation of 3-D magnetotelluric data can be a guide to a reasonable geological interpretation.
Recent advances in 2D materials for photocatalysis.
Luo, Bin; Liu, Gang; Wang, Lianzhou
2016-04-07
Two-dimensional (2D) materials have attracted increasing attention for photocatalytic applications because of their unique thickness dependent physical and chemical properties. This review gives a brief overview of the recent developments concerning the chemical synthesis and structural design of 2D materials at the nanoscale and their applications in photocatalytic areas. In particular, recent progress on the emerging strategies for tailoring 2D material-based photocatalysts to improve their photo-activity including elemental doping, heterostructure design and functional architecture assembly is discussed.
Comparison of 2D and 3D gamma analyses
Pulliam, Kiley B.; Huang, Jessie Y.; Howell, Rebecca M.; Followill, David; Kry, Stephen F.; Bosca, Ryan; O’Daniel, Jennifer
2014-02-15
Purpose: As clinics begin to use 3D metrics for intensity-modulated radiation therapy (IMRT) quality assurance, it must be noted that these metrics will often produce results different from those produced by their 2D counterparts. 3D and 2D gamma analyses would be expected to produce different values, in part because of the different search space available. In the present investigation, the authors compared the results of 2D and 3D gamma analysis (where both datasets were generated in the same manner) for clinical treatment plans. Methods: Fifty IMRT plans were selected from the authors’ clinical database, and recalculated using Monte Carlo. Treatment planning system-calculated (“evaluated dose distributions”) and Monte Carlo-recalculated (“reference dose distributions”) dose distributions were compared using 2D and 3D gamma analysis. This analysis was performed using a variety of dose-difference (5%, 3%, 2%, and 1%) and distance-to-agreement (5, 3, 2, and 1 mm) acceptance criteria, low-dose thresholds (5%, 10%, and 15% of the prescription dose), and data grid sizes (1.0, 1.5, and 3.0 mm). Each comparison was evaluated to determine the average 2D and 3D gamma, lower 95th percentile gamma value, and percentage of pixels passing gamma. Results: The average gamma, lower 95th percentile gamma value, and percentage of passing pixels for each acceptance criterion demonstrated better agreement for 3D than for 2D analysis for every plan comparison. The average difference in the percentage of passing pixels between the 2D and 3D analyses with no low-dose threshold ranged from 0.9% to 2.1%. Similarly, using a low-dose threshold resulted in a difference between the mean 2D and 3D results, ranging from 0.8% to 1.5%. The authors observed no appreciable differences in gamma with changes in the data density (constant difference: 0.8% for 2D vs 3D). Conclusions: The authors found that 3D gamma analysis resulted in up to 2.9% more pixels passing than 2D analysis. It must
Gordeev, M I; Burlak, V A
1991-02-01
Insensibility of larvae with different chromosomal inversions to the toxins of Bacillus thuringiensis subsp. israelensis (Bti) was examined. It has been shown that larvae with inversion combinations XL0(XL1)2R0-3R0-3L0 had greater variability after treatment with Bti than larvae with inversions XL1(XL2)2R1-3R1-3L1(3L0). The former inversion combinations were previously shown to dominate in the south of the species area and to be supported by K-selection. The latter inversion combinations form "northest" karyotypes and are supported by r-selection. It is obvious that genetic effects of treatments with Bti depend on the population's structure and the directions of natural selection. The decrease in the level of heterozygotes after treatment of larvae with Bti reflects destruction of the system of genetic homeostasis in the natural populations of A. messeae.
Time-resolved diffusion tomographic 2D and 3D imaging in highly scattering turbid media
NASA Technical Reports Server (NTRS)
Alfano, Robert R. (Inventor); Cai, Wei (Inventor); Liu, Feng (Inventor); Lax, Melvin (Inventor); Das, Bidyut B. (Inventor)
1999-01-01
A method for imaging objects in highly scattering turbid media. According to one embodiment of the invention, the method involves using a plurality of intersecting source/detectors sets and time-resolving equipment to generate a plurality of time-resolved intensity curves for the diffusive component of light emergent from the medium. For each of the curves, the intensities at a plurality of times are then inputted into the following inverse reconstruction algorithm to form an image of the medium: ##EQU1## wherein W is a matrix relating output at source and detector positions r.sub.s and r.sub.d, at time t, to position r, .LAMBDA. is a regularization matrix, chosen for convenience to be diagonal, but selected in a way related to the ratio of the noise,
Time-resolved diffusion tomographic 2D and 3D imaging in highly scattering turbid media
NASA Technical Reports Server (NTRS)
Alfano, Robert R. (Inventor); Cai, Wei (Inventor); Gayen, Swapan K. (Inventor)
2000-01-01
A method for imaging objects in highly scattering turbid media. According to one embodiment of the invention, the method involves using a plurality of intersecting source/detectors sets and time-resolving equipment to generate a plurality of time-resolved intensity curves for the diffusive component of light emergent from the medium. For each of the curves, the intensities at a plurality of times are then inputted into the following inverse reconstruction algorithm to form an image of the medium: wherein W is a matrix relating output at source and detector positions r.sub.s and r.sub.d, at time t, to position r, .LAMBDA. is a regularization matrix, chosen for convenience to be diagonal, but selected in a way related to the ratio of the noise,
Function representation with circle inversion map systems
NASA Astrophysics Data System (ADS)
Boreland, Bryson; Kunze, Herb
2017-01-01
The fractals literature develops the now well-known concept of local iterated function systems (using affine maps) with grey-level maps (LIFSM) as an approach to function representation in terms of the associated fixed point of the so-called fractal transform. While originally explored as a method to achieve signal (and 2-D image) compression, more recent work has explored various aspects of signal and image processing using this machinery. In this paper, we develop a similar framework for function representation using circle inversion map systems. Given a circle C with centre õ and radius r, inversion with respect to C transforms the point p˜ to the point p˜', such that p˜ and p˜' lie on the same radial half-line from õ and d(õ, p˜)d(õ, p˜') = r2, where d is Euclidean distance. We demonstrate the results with an example.
Double resonance rotational spectroscopy of CH2D+
NASA Astrophysics Data System (ADS)
Töpfer, Matthias; Jusko, Pavol; Schlemmer, Stephan; Asvany, Oskar
2016-09-01
Context. Deuterated forms of CH are thought to be responsible for deuterium enrichment in lukewarm astronomical environments. There is no unambiguous detection of CH2D+ in space to date. Aims: Four submillimetre rotational lines of CH2D+ are documented in the literature. Our aim is to present a complete dataset of highly resolved rotational lines, including millimetre (mm) lines needed for a potential detection. Methods: We used a low-temperature ion trap and applied a novel IR-mm-wave double resonance method to measure the rotational lines of CH2D+. Results: We measured 21 low-lying (J ≤ 4) rotational transitions of CH2D+ between 23 GHz and 1.1 THz with accuracies close to 2 ppb.
Recovering 3D particle size distributions from 2D sections
NASA Astrophysics Data System (ADS)
Cuzzi, Jeffrey N.; Olson, Daniel M.
2017-03-01
We discuss different ways to convert observed, apparent particle size distributions from 2D sections (thin sections, SEM maps on planar surfaces, etc.) into true 3D particle size distributions. We give a simple, flexible, and practical method to do this; show which of these techniques gives the most faithful conversions; and provide (online) short computer codes to calculate both 2D-3D recoveries and simulations of 2D observations by random sectioning. The most important systematic bias of 2D sectioning, from the standpoint of most chondrite studies, is an overestimate of the abundance of the larger particles. We show that fairly good recoveries can be achieved from observed size distributions containing 100-300 individual measurements of apparent particle diameter.
Phonon thermal conduction in novel 2D materials
NASA Astrophysics Data System (ADS)
Xu, Xiangfan; Chen, Jie; Li, Baowen
2016-12-01
Recently, there has been increasing interest in phonon thermal transport in low-dimensional materials, due to the crucial importance of dissipating and managing heat in micro- and nano-electronic devices. Significant progress has been achieved for one-dimensional (1D) systems, both theoretically and experimentally. However, the study of heat conduction in two-dimensional (2D) systems is still in its infancy due to the limited availability of 2D materials and the technical challenges of fabricating suspended samples that are suitable for thermal measurements. In this review, we outline different experimental techniques and theoretical approaches for phonon thermal transport in 2D materials, discuss the problems and challenges of phonon thermal transport measurements and provide a comparison between existing experimental data. Special attention will be given to the effects of size, dimensionality, anisotropy and mode contributions in novel 2D systems, including graphene, boron nitride, MoS2, black phosphorous and silicene.
Recent developments in 2D layered inorganic nanomaterials for sensing
NASA Astrophysics Data System (ADS)
Kannan, Padmanathan Karthick; Late, Dattatray J.; Morgan, Hywel; Rout, Chandra Sekhar
2015-08-01
Two dimensional layered inorganic nanomaterials (2D-LINs) have recently attracted huge interest because of their unique thickness dependent physical and chemical properties and potential technological applications. The properties of these layered materials can be tuned via both physical and chemical processes. Some 2D layered inorganic nanomaterials like MoS2, WS2 and SnS2 have been recently developed and employed in various applications, including new sensors because of their layer-dependent electrical properties. This article presents a comprehensive overview of recent developments in the application of 2D layered inorganic nanomaterials as sensors. Some of the salient features of 2D materials for different sensing applications are discussed, including gas sensing, electrochemical sensing, SERS and biosensing, SERS sensing and photodetection. The working principles of the sensors are also discussed together with examples.
Phonon thermal conduction in novel 2D materials.
Xu, Xiangfan; Chen, Jie; Li, Baowen
2016-12-07
Recently, there has been increasing interest in phonon thermal transport in low-dimensional materials, due to the crucial importance of dissipating and managing heat in micro- and nano-electronic devices. Significant progress has been achieved for one-dimensional (1D) systems, both theoretically and experimentally. However, the study of heat conduction in two-dimensional (2D) systems is still in its infancy due to the limited availability of 2D materials and the technical challenges of fabricating suspended samples that are suitable for thermal measurements. In this review, we outline different experimental techniques and theoretical approaches for phonon thermal transport in 2D materials, discuss the problems and challenges of phonon thermal transport measurements and provide a comparison between existing experimental data. Special attention will be given to the effects of size, dimensionality, anisotropy and mode contributions in novel 2D systems, including graphene, boron nitride, MoS2, black phosphorous and silicene.
Exact Solution of Ising Model in 2d Shortcut Network
NASA Astrophysics Data System (ADS)
Shanker, O.
We give the exact solution to the Ising model in the shortcut network in the 2D limit. The solution is found by mapping the model to the square lattice model with Brascamp and Kunz boundary conditions.
Technical Review of the UNET2D Hydraulic Model
Perkins, William A.; Richmond, Marshall C.
2009-05-18
The Kansas City District of the US Army Corps of Engineers is engaged in a broad range of river management projects that require knowledge of spatially-varied hydraulic conditions such as velocities and water surface elevations. This information is needed to design new structures, improve existing operations, and assess aquatic habitat. Two-dimensional (2D) depth-averaged numerical hydraulic models are a common tool that can be used to provide velocity and depth information. Kansas City District is currently using a specific 2D model, UNET2D, that has been developed to meet the needs of their river engineering applications. This report documents a tech- nical review of UNET2D.
Reconstruction-based 3D/2D image registration.
Tomazevic, Dejan; Likar, Bostjan; Pernus, Franjo
2005-01-01
In this paper we present a novel 3D/2D registration method, where first, a 3D image is reconstructed from a few 2D X-ray images and next, the preoperative 3D image is brought into the best possible spatial correspondence with the reconstructed image by optimizing a similarity measure. Because the quality of the reconstructed image is generally low, we introduce a novel asymmetric mutual information similarity measure, which is able to cope with low image quality as well as with different imaging modalities. The novel 3D/2D registration method has been evaluated using standardized evaluation methodology and publicly available 3D CT, 3DRX, and MR and 2D X-ray images of two spine phantoms, for which gold standard registrations were known. In terms of robustness, reliability and capture range the proposed method outperformed the gradient-based method and the method based on digitally reconstructed radiographs (DRRs).
Alloyed 2D Metal-Semiconductor Atomic Layer Junctions.
Kim, Ah Ra; Kim, Yonghun; Nam, Jaewook; Chung, Hee-Suk; Kim, Dong Jae; Kwon, Jung-Dae; Park, Sang Won; Park, Jucheol; Choi, Sun Young; Lee, Byoung Hun; Park, Ji Hyeon; Lee, Kyu Hwan; Kim, Dong-Ho; Choi, Sung Mook; Ajayan, Pulickel M; Hahm, Myung Gwan; Cho, Byungjin
2016-03-09
Heterostructures of compositionally and electronically variant two-dimensional (2D) atomic layers are viable building blocks for ultrathin optoelectronic devices. We show that the composition of interfacial transition region between semiconducting WSe2 atomic layer channels and metallic NbSe2 contact layers can be engineered through interfacial doping with Nb atoms. WxNb1-xSe2 interfacial regions considerably lower the potential barrier height of the junction, significantly improving the performance of the corresponding WSe2-based field-effect transistor devices. The creation of such alloyed 2D junctions between dissimilar atomic layer domains could be the most important factor in controlling the electronic properties of 2D junctions and the design and fabrication of 2D atomic layer devices.
Dominant 2D magnetic turbulence in the solar wind
NASA Technical Reports Server (NTRS)
Bieber, John W.; Wanner, Wolfgang; Matthaeus, William H.
1995-01-01
There have been recent suggestions that solar wind magnetic turbulence may be a composite of slab geometry (wavevector aligned with the mean magnetic field) and 2D geometry (wavevectors perpendicular to the mean field). We report results of two new tests of this hypothesis using Helios measurements of inertial ranged magnetic spectra in the solar wind. The first test is based upon a characteristic difference between perpendicular and parallel reduced power spectra which is expected for the 2D component but not for the slab component. The second test examines the dependence of power spectrum density upon the magnetic field angle (i.e., the angle between the mean magnetic field and the radial direction), a relationship which is expected to be in opposite directions for the slab and 2D components. Both tests support the presence of a dominant (approximately 85 percent by energy) 2D component in solar wind magnetic turbulence.
Studying Zeolite Catalysts with a 2D Model System
Boscoboinik, Anibal
2016-12-07
Anibal Boscoboinik, a materials scientist at Brookhaven’s Center for Functional Nanomaterials, discusses the surface-science tools and 2D model system he uses to study catalysis in nanoporous zeolites, which catalyze reactions in many industrial processes.
ORION96. 2-d Finite Element Code Postprocessor
Sanford, L.A.; Hallquist, J.O.
1992-02-02
ORION is an interactive program that serves as a postprocessor for the analysis programs NIKE2D, DYNA2D, TOPAZ2D, and CHEMICAL TOPAZ2D. ORION reads binary plot files generated by the two-dimensional finite element codes currently used by the Methods Development Group at LLNL. Contour and color fringe plots of a large number of quantities may be displayed on meshes consisting of triangular and quadrilateral elements. ORION can compute strain measures, interface pressures along slide lines, reaction forces along constrained boundaries, and momentum. ORION has been applied to study the response of two-dimensional solids and structures undergoing finite deformations under a wide variety of large deformation transient dynamic and static problems and heat transfer analyses.
Emerging and potential opportunities for 2D flexible nanoelectronics
NASA Astrophysics Data System (ADS)
Zhu, Weinan; Park, Saungeun; Akinwande, Deji
2016-05-01
The last 10 years have seen the emergence of two-dimensional (2D) nanomaterials such as graphene, transition metal dichalcogenides (TMDs), and black phosphorus (BP) among the growing portfolio of layered van der Waals thin films. Graphene, the prototypical 2D material has advanced rapidly in device, circuit and system studies that has resulted in commercial large-area applications. In this work, we provide a perspective of the emerging and potential translational applications of 2D materials including semiconductors, semimetals, and insulators that comprise the basic material set for diverse nanosystems. Applications include RF transceivers, smart systems, the so-called internet of things, and neurotechnology. We will review the DC and RF electronic performance of graphene and BP thin film transistors. 2D materials at sub-um channel length have so far enabled cut-off frequencies from baseband to 100GHz suitable for low-power RF and sub-THz concepts.
Anisotropic 2D Materials for Tunable Hyperbolic Plasmonics.
Nemilentsau, Andrei; Low, Tony; Hanson, George
2016-02-12
Motivated by the recent emergence of a new class of anisotropic 2D materials, we examine their electromagnetic modes and demonstrate that a broad class of the materials can host highly directional hyperbolic plasmons. Their propagation direction can be manipulated on the spot by gate doping, enabling hyperbolic beam reflection, refraction, and bending. The realization of these natural 2D hyperbolic media opens up a new avenue in dynamic control of hyperbolic plasmons not possible in the 3D version.
RNA folding pathways and kinetics using 2D energy landscapes.
Senter, Evan; Dotu, Ivan; Clote, Peter
2015-01-01
RNA folding pathways play an important role in various biological processes, such as (i) the hok/sok (host-killing/suppression of killing) system in E. coli to check for sufficient plasmid copy number, (ii) the conformational switch in spliced leader (SL) RNA from Leptomonas collosoma, which controls trans splicing of a portion of the '5 exon, and (iii) riboswitches--portions of the 5' untranslated region of messenger RNA that regulate genes by allostery. Since RNA folding pathways are determined by the energy landscape, we describe a novel algorithm, FFTbor2D, which computes the 2D projection of the energy landscape for a given RNA sequence. Given two metastable secondary structures A, B for a given RNA sequence, FFTbor2D computes the Boltzmann probability p(x, y) = Z(x,y)/Z that a secondary structure has base pair distance x from A and distance y from B. Using polynomial interpolationwith the fast Fourier transform,we compute p(x, y) in O(n(5)) time and O(n(2)) space, which is an improvement over an earlier method, which runs in O(n(7)) time and O(n(4)) space. FFTbor2D has potential applications in synthetic biology, where one might wish to design bistable switches having target metastable structures A, B with favorable pathway kinetics. By inverting the transition probability matrix determined from FFTbor2D output, we show that L. collosoma spliced leader RNA has larger mean first passage time from A to B on the 2D energy landscape, than 97.145% of 20,000 sequences, each having metastable structures A, B. Source code and binaries are freely available for download at http://bioinformatics.bc.edu/clotelab/FFTbor2D. The program FFTbor2D is implemented in C++, with optional OpenMP parallelization primitives.
Supported and Free-Standing 2D Semimetals
2015-01-15
of this effort on focusing on rare- earth arsenides (RE-A), although not a van der Waals 2D solid, nonetheless, exhibits substantial 2D quantum size...this effort on focusing on rare- earth arsenides (RE- A), although not a van der Waals 20 solid, nonetheless, exhibits substantial 20 quantum size...Brongersma and S.R. Bank, "Rare- earth monopnictide alloys for tunable, epitaxial metals" in preparation. iii. S. Rahimi, E. M. Krivoy, J. Lee, M. E
Application of 2-D graphical representation of DNA sequence
NASA Astrophysics Data System (ADS)
Liao, Bo; Tan, Mingshu; Ding, Kequan
2005-10-01
Recently, we proposed a 2-D graphical representation of DNA sequence [Bo Liao, A 2-D graphical representation of DNA sequence, Chem. Phys. Lett. 401 (2005) 196-199]. Based on this representation, we consider properties of mutations and compute the similarities among 11 mitochondrial sequences belonging to different species. The elements of the similarity matrix are used to construct phylogenic tree. Unlike most existing phylogeny construction methods, the proposed method does not require multiple alignment.
phase_space_cosmo_fisher: Fisher matrix 2D contours
NASA Astrophysics Data System (ADS)
Stark, Alejo
2016-11-01
phase_space_cosmo_fisher produces Fisher matrix 2D contours from which the constraints on cosmological parameters can be derived. Given a specified redshift array and cosmological case, 2D marginalized contours of cosmological parameters are generated; the code can also plot the derivatives used in the Fisher matrix. In addition, this package can generate 3D plots of qH^2 and other cosmological quantities as a function of redshift and cosmology.
A simultaneous 2D/3D autostereo workstation
NASA Astrophysics Data System (ADS)
Chau, Dennis; McGinnis, Bradley; Talandis, Jonas; Leigh, Jason; Peterka, Tom; Knoll, Aaron; Sumer, Aslihan; Papka, Michael; Jellinek, Julius
2012-03-01
We present a novel immersive workstation environment that scientists can use for 3D data exploration and as their everyday 2D computer monitor. Our implementation is based on an autostereoscopic dynamic parallax barrier 2D/3D display, interactive input devices, and a software infrastructure that allows client/server software modules to couple the workstation to scientists' visualization applications. This paper describes the hardware construction and calibration, software components, and a demonstration of our system in nanoscale materials science exploration.
Phylogenetic tree construction based on 2D graphical representation
NASA Astrophysics Data System (ADS)
Liao, Bo; Shan, Xinzhou; Zhu, Wen; Li, Renfa
2006-04-01
A new approach based on the two-dimensional (2D) graphical representation of the whole genome sequence [Bo Liao, Chem. Phys. Lett., 401(2005) 196.] is proposed to analyze the phylogenetic relationships of genomes. The evolutionary distances are obtained through measuring the differences among the 2D curves. The fuzzy theory is used to construct phylogenetic tree. The phylogenetic relationships of H5N1 avian influenza virus illustrate the utility of our approach.
Long ranged interactions in computer simulations and for quasi-2D systems
NASA Astrophysics Data System (ADS)
Mazars, Martial
2011-03-01
Taking correctly into account long ranged interactions in molecular simulations of molecular models based on classical atomistic representations are essential to obtain reliable results on model systems and in simulations of biological systems. A lot of numerical methods have been developed to this end; the most important of them are reviewed in this paper. Particular attention is paid to the analytical relations between the methods, this allows comparisons on efficiency and accuracy between them and also to proceed to precise implementations of these techniques. While most of the methods have been developed for Coulomb interactions, we give also some analytical details to apply these methods to screened Coulomb (Yukawa interactions), inverse power law and dipolar interactions. Particular types of systems, the quasi-2D systems, are also considered in this paper. Quasi-2D systems represent a large class of physical systems where the spatial extension in one direction of the space is very small by comparison to the other two. These representations are very useful to describe the properties of interfaces, surfaces, fluids confined in slab geometry, etc. In computer simulations, these systems are studied with partial periodic boundary conditions: periodic boundary conditions are taken in directions where spatial extensions are large and some other boundary conditions are taken in directions with smaller extensions. In this review, we describe also the numerical methods developed to handle long ranged interactions in numerical simulations of quasi-2D systems. The properties of quasi-2D systems depend strongly on interactions between components; more specifically electrostatic and magnetic interactions and interactions with external fields are of particular interest in these systems.
Regulation of NKG2D ligand gene expression.
Eagle, Robert A; Traherne, James A; Ashiru, Omodele; Wills, Mark R; Trowsdale, John
2006-03-01
The activating immunoreceptor NKG2D has seven known host ligands encoded by the MHC class I chain-related MIC and ULBP/RAET genes. Why there is such diversity of NKG2D ligands is not known but one hypothesis is that they are differentially expressed in different tissues in response to different stresses. To explore this, we compared expression patterns and promoters of NKG2D ligand genes. ULBP/RAET genes were transcribed independent of each other in a panel of cell lines. ULBP/RAET gene expression was upregulated on infection with human cytomegalovirus; however, a clinical strain, Toledo, induced expression more slowly than did a laboratory strain, AD169. ULBP4/RAET1E was not induced by infection with either strain. To investigate the mechanisms behind the similarities and differences in NKG2D ligand gene expression a comparative sequence analysis of NKG2D ligand gene putative promoter regions was conducted. Sequence alignments demonstrated that there was significant sequence diversity; however, one region of high similarity between most of the genes is evident. This region contains a number of potential transcription factor binding sites, including those involved in shock responses and sites for retinoic acid-induced factors. Promoters of some NKG2D ligand genes are polymorphic and several sequence alterations in these alleles abolished putative transcription factor binding.
CYP2D6 variability in populations from Venezuela.
Moreno, Nancy; Flores-Angulo, Carlos; Villegas, Cecilia; Mora, Yuselin
2016-12-01
CYP2D6 is an important cytochrome P450 enzyme that plays an important role in the metabolism of about 25% of currently prescribed drugs. The presence of polymorphisms in the CYP2D6 gene may modulate enzyme level and activity, thereby affecting individual responses to pharmacological treatments. The most prevalent diseases in the admixed population from Venezuela are cardiovascular and cancer, whereas viral, bacterial and parasitic diseases, particularly malaria, are prevalent in Amerindian populations; in the treatment of these diseases, several drugs that are metabolized by CYP2D6 are used. In this work, we reviewed the data on CYP2D6 variability and predicted metabolizer phenotypes, in healthy volunteers of two admixed and five Amerindian populations from Venezuela. The Venezuelan population is very heterogeneous as a result of the genetic admixture of three major ethnical components: Europeans, Africans and Amerindians. There are noticeable inter-regional and inter-population differences in the process of mixing of this population. Hitherto, there are few published studies in Venezuela on CYP2D6; therefore, it is necessary to increase research in this regard, in particular to develop studies with a larger sample size. There is a considerable amount of work remaining before CYP2D6 is integrated into clinical practice in Venezuela.
2D microscopic model of graphene fracture properties
NASA Astrophysics Data System (ADS)
Hess, Peter
2015-05-01
An analytical two-dimensional (2D) microscopic fracture model based on Morse-type interaction is derived containing no adjustable parameter. From the 2D Young’s moduli and 2D intrinsic strengths of graphene measured by nanoindentation based on biaxial tension and calculated by density functional theory for uniaxial tension the widely unknown breaking force, line or edge energy, surface energy, fracture toughness, and strain energy release rate were determined. The simulated line energy agrees well with ab initio calculations and the fracture toughness of perfect graphene sheets is in good agreement with molecular dynamics simulations and the fracture toughness evaluated for defective graphene using the Griffith relation. Similarly, the estimated critical strain energy release rate agrees well with result of various theoretical approaches based on the J-integral and surface energy. The 2D microscopic model, connecting 2D and three-dimensional mechanical properties in a consistent way, provides a versatile relationship to easily access all relevant fracture properties of pristine 2D solids.
Second to fourth digit ratio (2D:4D) and concentrations of circulating sex hormones in adulthood
2011-01-01
Background The second to fourth digit ratio (2D:4D) is used as a marker of prenatal sex hormone exposure. The objective of this study was to examine whether circulating concentrations of sex hormones and SHBG measured in adulthood was associated with 2D:4D. Methods This analysis was based on a random sample from the Melbourne Collaborative Cohort Study. The sample consisted of of 1036 men and 620 post-menopausal women aged between 39 and 70 at the time of blood draw. Concentrations of circulating sex hormones were measured from plasma collected at baseline (1990-1994), while digit length was measured from hand photocopies taken during a recent follow-up (2003-2009). The outcome measures were circulating concentrations of testosterone, oestradiol, dehydroepiandrosterone sulphate, androstenedione, Sex Hormone Binding Globulin, androstenediol glucoronide for men only and oestrone sulphate for women only. Free testosterone and oestradiol were estimated using standard formulae derived empirically. Predicted geometric mean hormone concentrations (for tertiles of 2D:4D) and conditional correlation coefficients (for continuous 2D:4D) were obtained using mixed effects linear regression models. Results No strong associations were observed between 2D:4D measures and circulating concentrations of hormones for men or women. For males, right 2D:4D was weakly inversely associated with circulating testosterone (predicted geometric mean testosterone was 15.9 and 15.0 nmol/L for the lowest and highest tertiles of male right 2D:4D respectively (P-trend = 0.04). There was a similar weak association between male right 2D:4D and the ratio of testosterone to oestradiol. These associations were not evident in analyses of continuous 2D:4D. Conclusions There were no strong associations between any adult circulating concentration of sex hormone or SHGB and 2D:4D. These results contribute to the growing body of evidence indicating that 2D:4D is unrelated to adult sex hormone concentrations
2D Hexagonal Boron Nitride (2D-hBN) Explored for the Electrochemical Sensing of Dopamine.
Khan, Aamar F; Brownson, Dale A C; Randviir, Edward P; Smith, Graham C; Banks, Craig E
2016-10-04
Crystalline 2D hexagonal boron nitride (2D-hBN) nanosheets are explored as a potential electrocatalyst toward the electroanalytical sensing of dopamine (DA). The 2D-hBN nanosheets are electrically wired via a drop-casting modification process onto a range of commercially available carbon supporting electrodes, including glassy carbon (GC), boron-doped diamond (BDD), and screen-printed graphitic electrodes (SPEs). 2D-hBN has not previously been explored toward the electrochemical detection/electrochemical sensing of DA. We critically evaluate the potential electrocatalytic performance of 2D-hBN modified electrodes, the effect of supporting carbon electrode platforms, and the effect of "mass coverage" (which is commonly neglected in the 2D material literature) toward the detection of DA. The response of 2D-hBN modified electrodes is found to be largely dependent upon the interaction between 2D-hBN and the underlying supporting electrode material. For example, in the case of SPEs, modification with 2D-hBN (324 ng) improves the electrochemical response, decreasing the electrochemical oxidation potential of DA by ∼90 mV compared to an unmodified SPE. Conversely, modification of a GC electrode with 2D-hBN (324 ng) resulted in an increased oxidation potential of DA by ∼80 mV when compared to the unmodified electrode. We explore the underlying mechanisms of the aforementioned examples and infer that electrode surface interactions and roughness factors are critical considerations. 2D-hBN is utilized toward the sensing of DA in the presence of the common interferents ascorbic acid (AA) and uric acid (UA). 2D-hBN is found to be an effective electrocatalyst in the simultaneous detection of DA and UA at both pH 5.0 and 7.4. The peak separations/resolution between DA and UA increases by ∼70 and 50 mV (at pH 5.0 and 7.4, respectively, when utilizing 108 ng of 2D-hBN) compared to unmodified SPEs, with a particularly favorable response evident in pH 5.0, giving rise to a
Fluidic behaviours in a 2D folded-graphene aerogel monolith
NASA Astrophysics Data System (ADS)
Xu, Xiang; Zhang, Qiangqiang; Yu, Yikang; Yang, Kaichun; He, Qiuyu; Chen, Weizhe; Li, Hui; Qiao, Yu
2015-10-01
Conduction of pressurized water through two-dimensional (2D) layers in monolithic folded-graphene aerogels (FGA) is investigated experimentally. The synthesized FGA has a regular layered structure with a uniform d-spacing around 20 nm. Compared with one-dimensional nanofluidics in carbon nanotube arrays that have a similar characteristic length scale, the conduction pressure of FGA is much lower by nearly 2/3. The reduction in pressure may be attributed to the more energetically favourable molecular configurations in the 2D nanoenvironment, associated with the relaxation of lateral constraints of water molecules. The water conduction pressure through FGA rises exponentially with the sample thickness, due to the interlayer resistance. This finding may find wide applications in nanotransportation, nanofiltration, and nanofluidic energy management.
Thermal Conductivity and Thermopower near the 2D Metal-Insulator transition, Final Technical Report
Sarachik, Myriam P.
2015-02-20
STUDIES OF STRONGLY-INTERACTING 2D ELECTRON SYSTEMS – There is a great deal of current interest in the properties of systems in which the interaction between electrons (their potential energy) is large compared to their kinetic energy. We have investigated an apparent, unexpected metal-insulator transition inferred from the behavior of the temperature-dependence of the resistivity; moreover, detailed analysis of the behavior of the magnetoresistance suggests that the electrons’ effective mass diverges, supporting this scenario. Whether this is a true phase transition or crossover behavior has been strenuously debated over the past 20 years. Our measurements have now shown that the thermoelectric power of these 2D materials diverges at a finite density, providing clear evidence that this is, in fact, a phase transition to a new low-density phase which may be a precursor or a direct transition to the long sought-after electronic crystal predicted by Eugene Wigner in 1934.
NASA Astrophysics Data System (ADS)
Yin, Yaotian; Unsworth, Martyn; Liddell, Mitch; Pana, Dinu; Craven, James A.
2014-10-01
Three magnetotelluric (MT) profiles in northwestern Canada cross the central and western segments of Great Slave Lake shear zone (GSLsz), a continental scale strike-slip structure active during the Slave-Rae collision in the Proterozoic. Dimensionality analysis indicates that (i) the resistivity structure is approximately 2-D with a geoelectric strike direction close to the dominant geological strike of N45°E and that (ii) electrical anisotropy may be present in the crust beneath the two southernmost profiles. Isotropic and anisotropic 2-D inversion and isotropic 3-D inversions show different resistivity structures on different segments of the shear zone. The GSLsz is imaged as a high resistivity zone (>5000 Ω m) that is at least 20 km wide and extends to a depth of at least 50 km on the northern profile. On the southern two profiles, the resistive zone is confined to the upper crust and pierces an east-dipping crustal conductor. Inversions show that this dipping conductor may be anisotropic, likely caused by conductive materials filling a network of fractures with a preferred spatial orientation. These conductive regions would have been disrupted by strike-slip, ductile deformation on the GSLsz that formed granulite to greenschist facies mylonite belts. The pre-dominantly granulite facies mylonites are resistive and explain why the GSLsz appears as a resistive structure piercing the east-dipping anisotropic layer. The absence of a dipping anisotropic/conductive layer on the northern MT profile, located on the central segment of the GSLsz, is consistent with the lack of subduction at this location as predicted by geological and tectonic models.
The inverse electroencephalography pipeline
NASA Astrophysics Data System (ADS)
Weinstein, David Michael
The inverse electroencephalography (EEG) problem is defined as determining which regions of the brain are active based on remote measurements recorded with scalp EEG electrodes. An accurate solution to this problem would benefit both fundamental neuroscience research and clinical neuroscience applications. However, constructing accurate patient-specific inverse EEG solutions requires complex modeling, simulation, and visualization algorithms, and to date only a few systems have been developed that provide such capabilities. In this dissertation, a computational system for generating and investigating patient-specific inverse EEG solutions is introduced, and the requirements for each stage of this Inverse EEG Pipeline are defined and discussed. While the requirements of many of the stages are satisfied with existing algorithms, others have motivated research into novel modeling and simulation methods. The principal technical results of this work include novel surface-based volume modeling techniques, an efficient construction for the EEG lead field, and the Open Source release of the Inverse EEG Pipeline software for use by the bioelectric field research community. In this work, the Inverse EEG Pipeline is applied to three research problems in neurology: comparing focal and distributed source imaging algorithms; separating measurements into independent activation components for multifocal epilepsy; and localizing the cortical activity that produces the P300 effect in schizophrenia.
NASA Astrophysics Data System (ADS)
Chen, R.; Zhao, X.; Yao, H.; He, X.; Zeng, P.; Chang, F.; Yang, Y.; Zhang, X.; Xi, X.; He, L.
2015-12-01
Induced polarization (IP) is a powerful tool in metalliferous ore exploration. However, there are many sources, such as clay and graphite, which can generate IP anomaly. Spectral induced polarization (SIP) measures IP response on a wide frequency range. This method provides a way to discriminate IP response generated by metalliferous ore or other objects. The best way to explore metalliferous ore is 3D SIP exploration. However, if we consider the exploration cost and efficiency, we can use SIP profiling to find an anomaly, and then use 2D/3D SIP sounding to characterize the anomaly. Based on above idea, we used a large-scale distributed SIP measurement system which can realize 800 sounding sites in one direction at the same time. This system can be used for SIP profiling, 2D/3D SIP sounding with high efficiency, high resolution, and large depth of investigation (> 1000 m). Qiushuwan copper - molybdenum deposit is located in Nanyang city, Henan province, China. It is only a middle-size deposit although over 100 holes were drilled and over 40 years of exploration were spent because of very complex geological setting. We made SIP measurement over 100 rock and ore samples to discriminate IP responses of ore and rock containing graphite. Then we carried out 7 lines of 2D SIP exploration with the depth of investigation great than 1000 m. The minimum electode spacing for potential difference is only 20 m. And we increase the spacing of current electodes at linear scale. This acquisition setting ensures high density data acquired and high quality data acquisition. Modeling and inversion result proves that we can get underground information with high resolution by our method. Our result shows that there exists a strong SIP response related to ore body in depth > 300 m. Pseudo-3D inversion of five 2D SIP sounding lines shows the location and size of IP anomaly. The new drillings based our result found a big copper-molybdenum ore body in new position with depth > 300 m and
NASA Astrophysics Data System (ADS)
Farzamian, Mohammad; Monteiro Santos, Fernando A.; Khalil, Mohamed A.
2015-10-01
Hydraulic conductivity is an important soil property when determining the potential for water movement in topsoil and in spite of its importance; soil hydraulic conductivity remains one of the most difficult of soil properties to assess. Laboratory methods have limitations due to the size of the samples and taking undisturbed soil samples is usually difficult in sandy soil and in-situ methods are required to estimate hydraulic conductivity. This study was conducted to estimate saturated hydraulic conductivity in unsaturated sandstone using the ground surface electrical resistivity tomography (ERT). The site is characterized by a deep Arenosol soil with high permeability and a low water retention capacity located at the Semora-Correia, the east of Lisbon. Eight ERT snapshots were collected during a water injection test to produce a sequence of 2D resistivity images. Time-lapse ERT data were inverted using independent data inversion, the difference inversion and simultaneous space-time inversion methods. Afterward, using an in-situ approach resistivity variation models were converted to water content images. By comparing first and second spatial moments of water movement images inferred from the ERT method with unsaturated flow simulation predicted from a numerical solution of Richards' equation, the range of saturated hydraulic conductivity is estimated to be in 0.5-0.7 (cm/min). The evaluation of ERT approach was made using a synthetic test. The results of synthetic test showed that the estimated parameters were significantly influenced by the ERT inversion method and an overprediction of spatial moments and consequently saturated hydraulic conductivity was observed in all inversion methods; however the resistivity models obtained by simultaneous space-time inversion method was more successful in water movement monitoring.
McGilvray, Roger W; Eagle, Robert A; Rolland, Phil; Jafferji, Insiya; Trowsdale, John; Durrant, Lindy G
2010-09-01
The human activating immune receptor, NKG2D, binds to a diverse array of cellular ligands of the MIC and unique long 16 (UL16)-binding protein (ULBP)/retinoic acid early transcript (RAET) family. NKG2D is thought to participate in anticancer immune responses. By using tissue microarrays representing over 300 patients with defined clinicopathological factors, we present the first comprehensive screen of the expression of all NKG2D ligands in primary ovarian cancers. NKG2D ligands were expressed by the majority of tumors; however, the level of expression varied considerably. By categorizing each tumor as having negative, low or high expression, it was shown that high expression of several NKG2D ligands is inversely correlated with disease survival. Patients whose tumors had high expression of RAET1E (p = 0.037), ULBP1 (p = 0.036) and ULBP3 (p = 0.004) surviving a median of 11, 14 and 11 months, respectively, compared with disease-specific survival of 29, 30 and 25 months in patients whose tumors showed no expression of these ligands. These results contrast with previous findings showing that high level NKG2D ligand expression is associated with good prognosis in colorectal cancer and suggest a fundamental difference in the involvement of NKG2D-mediated immunity in these two types of cancer. By using multivariate analysis, the factors retaining independent prognostic significance were International Federation of Gynecologists and Obstetricians stage (p < 0.001), presence of residual disease (p = 0.003), ULBP2 (p = 0.042) and RAET1E (p = 0.030).
Nagaraju, J.
2013-01-01
Phantoms are essentially required to generate boundary data for studying the inverse solver performance in electrical impedance tomography (EIT). A MATLAB-based boundary data simulator (BDS) is developed to generate accurate boundary data using neighbouring current pattern for assessing the EIT inverse solvers. Domain diameter, inhomogeneity number, inhomogeneity geometry (shape, size, and position), background conductivity, and inhomogeneity conductivity are all set as BDS input variables. Different sets of boundary data are generated by changing the input variables of the BDS, and resistivity images are reconstructed using electrical impedance tomography and diffuse optical tomography reconstruction software (EIDORS). Results show that the BDS generates accurate boundary data for different types of single or multiple objects which are efficient enough to reconstruct the resistivity images for assessing the inverse solver. It is noticed that for the BDS with 2048 elements, the boundary data for all inhomogeneities with a diameter larger than 13.3% of that of the phantom are accurate enough to reconstruct the resistivity images in EIDORS-2D. By comparing the reconstructed image with an original geometry made in BDS, it would be easier to study the inverse solver performance and the origin of the boundary data error can be identified. PMID:27006909
Regulation of ligands for the activating receptor NKG2D
Mistry, Anita R; O'Callaghan, Chris A
2007-01-01
The outcome of an encounter between a cytotoxic cell and a potential target cell depends on the balance of signals from inhibitory and activating receptors. Natural Killer group 2D (NKG2D) has recently emerged as a major activating receptor on T lymphocytes and natural killer cells. In both humans and mice, multiple different genes encode ligands for NKG2D, and these ligands are non-classical major histocompatibility complex class I molecules. The NKG2D–ligand interaction triggers an activating signal in the cell expressing NKG2D and this promotes cytotoxic lysis of the cell expressing the ligand. Most normal tissues do not express ligands for NKG2D, but ligand expression has been documented in tumour and virus-infected cells, leading to lysis of these cells. Tight regulation of ligand expression is important. If there is inappropriate expression in normal tissues, this will favour autoimmune processes, whilst failure to up-regulate the ligands in pathological conditions would favour cancer development or dissemination of intracellular infection. PMID:17614877
Rotation invariance principles in 2D/3D registration
NASA Astrophysics Data System (ADS)
Birkfellner, Wolfgang; Wirth, Joachim; Burgstaller, Wolfgang; Baumann, Bernard; Staedele, Harald; Hammer, Beat; Gellrich, Niels C.; Jacob, Augustinus L.; Regazzoni, Pietro; Messmer, Peter
2003-05-01
2D/3D patient-to-computed tomography (CT) registration is a method to determine a transformation that maps two coordinate systems by comparing a projection image rendered from CT to a real projection image. Applications include exact patient positioning in radiation therapy, calibration of surgical robots, and pose estimation in computer-aided surgery. One of the problems associated with 2D/3D registration is the fast that finding a registration includes sovling a minimization problem in six degrees-of-freedom in motion. This results in considerable time expenses since for each iteration step at least one volume rendering has to be computed. We show that by choosing an appropriate world coordinate system and by applying a 2D/2D registration method in each iteration step, the number of iterations can be grossly reduced from n6 to n5. Here, n is the number of discrete variations aroudn a given coordinate. Depending on the configuration of the optimization algorithm, this reduces the total number of iterations necessary to at least 1/3 of its original value. The method was implemented and extensively tested on simulated x-ray images of a pelvis. We conclude that this hardware-indepenent optimization of 2D/3D registration is a step towards increasing the acceptance of this promising method for a wide number of clinical applications.
2D nanostructures for water purification: graphene and beyond.
Dervin, Saoirse; Dionysiou, Dionysios D; Pillai, Suresh C
2016-08-18
Owing to their atomically thin structure, large surface area and mechanical strength, 2D nanoporous materials are considered to be suitable alternatives for existing desalination and water purification membrane materials. Recent progress in the development of nanoporous graphene based materials has generated enormous potential for water purification technologies. Progress in the development of nanoporous graphene and graphene oxide (GO) membranes, the mechanism of graphene molecular sieve action, structural design, hydrophilic nature, mechanical strength and antifouling properties and the principal challenges associated with nanopore generation are discussed in detail. Subsequently, the recent applications and performance of newly developed 2D materials such as 2D boron nitride (BN) nanosheets, graphyne, molybdenum disulfide (MoS2), tungsten chalcogenides (WS2) and titanium carbide (Ti3C2Tx) are highlighted. In addition, the challenges affecting 2D nanostructures for water purification are highlighted and their applications in the water purification industry are discussed. Though only a few 2D materials have been explored so far for water treatment applications, this emerging field of research is set to attract a great deal of attention in the near future.
2D Materials for Optical Modulation: Challenges and Opportunities.
Yu, Shaoliang; Wu, Xiaoqin; Wang, Yipei; Guo, Xin; Tong, Limin
2017-02-21
Owing to their atomic layer thickness, strong light-material interaction, high nonlinearity, broadband optical response, fast relaxation, controllable optoelectronic properties, and high compatibility with other photonic structures, 2D materials, including graphene, transition metal dichalcogenides and black phosphorus, have been attracting increasing attention for photonic applications. By tuning the carrier density via electrical or optical means that modifies their physical properties (e.g., Fermi level or nonlinear absorption), optical response of the 2D materials can be instantly changed, making them versatile nanostructures for optical modulation. Here, up-to-date 2D material-based optical modulation in three categories is reviewed: free-space, fiber-based, and on-chip configurations. By analysing cons and pros of different modulation approaches from material and mechanism aspects, the challenges faced by using these materials for device applications are presented. In addition, thermal effects (e.g., laser induced damage) in 2D materials, which are critical to practical applications, are also discussed. Finally, the outlook for future opportunities of these 2D materials for optical modulation is given.
2D DIGE saturation labeling for minute sample amounts.
Arnold, Georg J; Fröhlich, Thomas
2012-01-01
The 2D DIGE technique, based on fluorophores covalently linked to amino acid side chain residues and the concept of an internal standard, has significantly improved reproducibility, sensitivity, and the dynamic range of protein quantification. In saturation DIGE, sulfhydryl groups of cysteines are labeled with cyanine dyes to completion, providing a so far unraveled sensitivity for protein detection and quantification in 2D gel-based proteomic experiments. Only a few micrograms of protein per 2D gel facilitate the analysis of about 2,000 analytes from complex mammalian cell or tissue samples. As a consequence, 2D saturation DIGE is the method of choice when only minute sample amounts are available for quantitative proteome analysis at the level of proteins rather than peptides. Since very low amounts of samples have to be handled in a reproducible manner, saturation DIGE-based proteomic experiments are technically demanding. Moreover, successful saturation DIGE approaches require a strict adherence to adequate reaction conditions at each step. This chapter is dedicated to colleagues already experienced in 2D PAGE protein separation and intends to support the establishment of this ultrasensitive technique in proteomic workgroups. We provide basic guidelines for the experimental design and discuss crucial aspects concerning labeling chemistry, sample preparation, and pitfalls caused by labeling artifacts. A detailed step-by-step protocol comprises all aspects from initial sample preparation to image analysis and statistical evaluation. Furthermore, we describe the generation of preparative saturation DIGE gels necessary for mass spectrometry-based spot identification.
Mermin–Wagner fluctuations in 2D amorphous solids
Illing, Bernd; Fritschi, Sebastian; Kaiser, Herbert; Klix, Christian L.; Maret, Georg; Keim, Peter
2017-01-01
In a recent commentary, J. M. Kosterlitz described how D. Thouless and he got motivated to investigate melting and suprafluidity in two dimensions [Kosterlitz JM (2016) J Phys Condens Matter 28:481001]. It was due to the lack of broken translational symmetry in two dimensions—doubting the existence of 2D crystals—and the first computer simulations foretelling 2D crystals (at least in tiny systems). The lack of broken symmetries proposed by D. Mermin and H. Wagner is caused by long wavelength density fluctuations. Those fluctuations do not only have structural impact, but additionally a dynamical one: They cause the Lindemann criterion to fail in 2D in the sense that the mean squared displacement of atoms is not limited. Comparing experimental data from 3D and 2D amorphous solids with 2D crystals, we disentangle Mermin–Wagner fluctuations from glassy structural relaxations. Furthermore, we demonstrate with computer simulations the logarithmic increase of displacements with system size: Periodicity is not a requirement for Mermin–Wagner fluctuations, which conserve the homogeneity of space on long scales. PMID:28137872
Mean flow and anisotropic cascades in decaying 2D turbulence
NASA Astrophysics Data System (ADS)
Liu, Chien-Chia; Cerbus, Rory; Gioia, Gustavo; Chakraborty, Pinaki
2015-11-01
Many large-scale atmospheric and oceanic flows are decaying 2D turbulent flows embedded in a non-uniform mean flow. Despite its importance for large-scale weather systems, the affect of non-uniform mean flows on decaying 2D turbulence remains unknown. In the absence of mean flow it is well known that decaying 2D turbulent flows exhibit the enstrophy cascade. More generally, for any 2D turbulent flow, all computational, experimental and field data amassed to date indicate that the spectrum of longitudinal and transverse velocity fluctuations correspond to the same cascade, signifying isotropy of cascades. Here we report experiments on decaying 2D turbulence in soap films with a non-uniform mean flow. We find that the flow transitions from the usual isotropic enstrophy cascade to a series of unusual and, to our knowledge, never before observed or predicted, anisotropic cascades where the longitudinal and transverse spectra are mutually independent. We discuss implications of our results for decaying geophysical turbulence.
2-D Clinostat for Simulated Microgravity Experiments with Arabidopsis Seedlings
NASA Astrophysics Data System (ADS)
Wang, Hui; Li, Xugang; Krause, Lars; Görög, Mark; Schüler, Oliver; Hauslage, Jens; Hemmersbach, Ruth; Kircher, Stefan; Lasok, Hanna; Haser, Thomas; Rapp, Katja; Schmidt, Jürgen; Yu, Xin; Pasternak, Taras; Aubry-Hivet, Dorothée; Tietz, Olaf; Dovzhenko, Alexander; Palme, Klaus; Ditengou, Franck Anicet
2016-04-01
Ground-based simulators of microgravity such as fast rotating 2-D clinostats are valuable tools to study gravity related processes. We describe here a versatile g-value-adjustable 2-D clinostat that is suitable for plant analysis. To avoid seedling adaptation to 1 g after clinorotation, we designed chambers that allow rapid fixation. A detailed protocol for fixation, RNA isolation and the analysis of selected genes is described. Using this clinostat we show that mRNA levels of LONG HYPOCOTYL 5 (HY5), MIZU-KUSSEI 1 (MIZ1) and microRNA MIR163 are down-regulated in 5-day-old Arabidopsis thaliana roots after 3 min and 6 min of clinorotation using a maximal reduced g-force of 0.02 g, hence demonstrating that this 2-D clinostat enables the characterization of early transcriptomic events during root response to microgravity. We further show that this 2-D clinostat is able to compensate the action of gravitational force as both gravitropic-dependent statolith sedimentation and subsequent auxin redistribution (monitoring D R5 r e v :: G F P reporter) are abolished when plants are clinorotated. Our results demonstrate that 2-D clinostats equipped with interchangeable growth chambers and tunable rotation velocity are suitable for studying how plants perceive and respond to simulated microgravity.
Optimization schemes for the inversion of Bouguer gravity anomalies
NASA Astrophysics Data System (ADS)
Zamora, Azucena
Data sets obtained from measurable physical properties of the Earth structure have helped advance the understanding of its tectonic and structural processes and constitute key elements for resource prospecting. 2-Dimensional (2-D) and 3-D models obtained from the inversion of geophysical data sets are widely used to represent the structural composition of the Earth based on physical properties such as density, seismic wave velocities, magnetic susceptibility, conductivity, and resistivity. The inversion of each one of these data sets provides structural models whose consistency depends on the data collection process, methodology, and overall assumptions made in their individual mathematical processes. Although sampling the same medium, seismic and non-seismic methods often provide inconsistent final structural models of the Earth with varying accuracy, sensitivity, and resolution. Taking two or more geophysical data sets with complementary characteristics (e.g. having higher resolution at different depths) and combining their individual strengths to create a new improved structural model can help achieve higher accuracy and resolution power with respect to its original components while reducing their ambiguity and uncertainty effects. Gravity surveying constitutes a cheap, non-invasive, and non-destructive passive remote sensing method that helps to delineate variations in the gravity field. These variations can originate from regional anomalies due to deep density variations or from residual anomalies related to shallow density variations [41]. Since gravity anomaly inversions suffer from significant non-uniqueness (allowing two or more distinct density structures to have the same gravity signature) and small changes in parameters can highly impact the resulting model, the inversion of gravity data represents an ill-posed mathematical problem. However, gravity studies have demonstrated the effectiveness of this method to trace shallow subsurface density variations
Secretory pathways generating immunosuppressive NKG2D ligands
Baragaño Raneros, Aroa; Suarez-Álvarez, Beatriz; López-Larrea, Carlos
2014-01-01
Natural Killer Group 2 member D (NKG2D) activating receptor, present on the surface of various immune cells, plays an important role in activating the anticancer immune response by their interaction with stress-inducible NKG2D ligands (NKG2DL) on transformed cells. However, cancer cells have developed numerous mechanisms to evade the immune system via the downregulation of NKG2DL from the cell surface, including the release of NKG2DL from the cell surface in a soluble form. Here, we review the mechanisms involved in the production of soluble NKG2DL (sNKG2DL) and the potential therapeutic strategies aiming to block the release of these immunosuppressive ligands. Therapeutically enabling the NKG2D-NKG2DL interaction would promote immunorecognition of malignant cells, thus abrogating disease progression. PMID:25050215
Splashing transients of 2D plasmons launched by swift electrons
Lin, Xiao; Kaminer, Ido; Shi, Xihang; Gao, Fei; Yang, Zhaoju; Gao, Zhen; Buljan, Hrvoje; Joannopoulos, John D.; Soljačić, Marin; Chen, Hongsheng; Zhang, Baile
2017-01-01
Launching of plasmons by swift electrons has long been used in electron energy–loss spectroscopy (EELS) to investigate the plasmonic properties of ultrathin, or two-dimensional (2D), electron systems. However, the question of how a swift electron generates plasmons in space and time has never been answered. We address this issue by calculating and demonstrating the spatial-temporal dynamics of 2D plasmon generation in graphene. We predict a jet-like rise of excessive charge concentration that delays the generation of 2D plasmons in EELS, exhibiting an analog to the hydrodynamic Rayleigh jet in a splashing phenomenon before the launching of ripples. The photon radiation, analogous to the splashing sound, accompanies the plasmon emission and can be understood as being shaken off by the Rayleigh jet–like charge concentration. Considering this newly revealed process, we argue that previous estimates on the yields of graphene plasmons in EELS need to be reevaluated. PMID:28138546
Available information in 2D motional Stark effect imaging.
Creese, Mathew; Howard, John
2010-10-01
Recent advances in imaging techniques have allowed the extension of the standard polarimetric 1D motional Stark effect (MSE) diagnostic to 2D imaging of the internal magnetic field of fusion devices [J. Howard, Plasma Phys. Controlled Fusion 50, 125003 (2008)]. This development is met with the challenge of identifying and extracting the new information, which can then be used to increase the accuracy of plasma equilibrium and current density profile determinations. This paper develops a 2D analysis of the projected MSE polarization orientation and Doppler phase shift. It is found that, for a standard viewing position, the 2D MSE imaging system captures sufficient information to allow imaging of the internal vertical magnetic field component B(Z)(r,z) in a tokamak.
Perception-based reversible watermarking for 2D vector maps
NASA Astrophysics Data System (ADS)
Men, Chaoguang; Cao, Liujuan; Li, Xiang
2010-07-01
This paper presents an effective and reversible watermarking approach for digital copyright protection of 2D-vector maps. To ensure that the embedded watermark is insensitive for human perception, we only select the noise non-sensitive regions for watermark embedding by estimating vertex density within each polyline. To ensure the exact recovery of original 2D-vector map after watermark extraction, we introduce a new reversible watermarking scheme based on reversible high-frequency wavelet coefficients modification. Within the former-selected non-sensitive regions, our watermarking operates on the lower-order vertex coordinate decimals with integer wavelet transform. Such operation further reduces the visual distortion caused by watermark embedding. We have validated the effectiveness of our scheme on our real-world city river/building 2D-vector maps. We give extensive experimental comparisons with state-of-the-art methods, including embedding capability, invisibility, and robustness over watermark attacking.
Microscale 2D separation systems for proteomic analysis
Xu, Xin; Liu, Ke; Fan, Z. Hugh
2012-01-01
Microscale 2D separation systems have been implemented in capillaries and microfabricated channels. They offer advantages of faster analysis, higher separation efficiency and less sample consumption than the conventional methods, such as liquid chromatography (LC) in a column and slab gel electrophoresis. In this article, we review their recent advancement, focusing on three types of platforms, including 2D capillary electrophoresis (CE), CE coupling with capillary LC, and microfluidic devices. A variety of CE and LC modes have been employed to construct 2D separation systems via sophistically designed interfaces. Coupling of different separation modes has also been realized in a number of microfluidic devices. These separation systems have been applied for the proteomic analysis of various biological samples, ranging from a single cell to tumor tissues. PMID:22462786
2D materials for photon conversion and nanophotonics
NASA Astrophysics Data System (ADS)
Tahersima, Mohammad H.; Sorger, Volker J.
2015-09-01
The field of two-dimensional (2D) materials has the potential to enable unique applications across a wide range of the electromagnetic spectrum. While 2D-layered materials hold promise for next-generation photon-conversion intrinsic limitations and challenges exist that shall be overcome. Here we discuss the intrinsic limitations as well as application opportunities of this new class of materials, and is sponsored by the NSF program Designing Materials to Revolutionize and Engineer our Future (DMREF) program, which links to the President's Materials Genome Initiative. We present general material-related details for photon conversion, and show that taking advantage of the mechanical flexibility of 2D materials by rolling MoS2/graphene/hexagonal boron nitride stack to a spiral solar cell allows for solar absorption up to 90%.
Rapid-scan coherent 2D fluorescence spectroscopy.
Draeger, Simon; Roeding, Sebastian; Brixner, Tobias
2017-02-20
We developed pulse-shaper-assisted coherent two-dimensional (2D) electronic spectroscopy in liquids using fluorescence detection. A customized pulse shaper facilitates shot-to-shot modulation at 1 kHz and is employed for rapid scanning over all time delays. A full 2D spectrum with 15 × 15 pixels is obtained in approximately 6 s of measurement time (plus further averaging if needed). Coherent information is extracted from the incoherent fluorescence signal via 27-step phase cycling. We exemplify the technique on cresyl violet in ethanol and recover literature-known oscillations as a function of population time. Signal-to-noise behavior is analyzed as a function of the amount of averaging. Rapid scanning provides a 2D spectrum with a root-mean-square error of < 0.05 after 1 min of measurement time.
2D-3D transition of gold cluster anions resolved
NASA Astrophysics Data System (ADS)
Johansson, Mikael P.; Lechtken, Anne; Schooss, Detlef; Kappes, Manfred M.; Furche, Filipp
2008-05-01
Small gold cluster anions Aun- are known for their unusual two-dimensional (2D) structures, giving rise to properties very different from those of bulk gold. Previous experiments and calculations disagree about the number of gold atoms nc where the transition to 3D structures occurs. We combine trapped ion electron diffraction and state of the art electronic structure calculations to resolve this puzzle and establish nc=12 . It is shown that theoretical studies using traditional generalized gradient functionals are heavily biased towards 2D structures. For a correct prediction of the 2D-3D crossover point it is crucial to use density functionals yielding accurate jellium surface energies, such as the Tao-Perdew-Staroverov-Scuseria (TPSS) functional or the Perdew-Burke-Ernzerhof functional modified for solids (PBEsol). Further, spin-orbit effects have to be included, and large, flexible basis sets employed. This combined theoretical-experimental approach is promising for larger gold and other metal clusters.
IUPAP Award: Ion transport in 2D materials
NASA Astrophysics Data System (ADS)
Bao, Wenzhong
Intercalation in 2D materials drastically influences both physical and chemical properties, which leads to a new degree of freedom for fundamental studies and expands the potential applications of 2D materials. In this talk, I will discuss our work in the past two years related to ion intercalation of 2D materials, including insertion of Li and Na ions in graphene and MoS2. We focused on both fundamental mechanism and potential application, e.g. we measured in-situ optical transmittance spectra and electrical transport properties of few-layer graphene (FLG) nanostructures upon electrochemical lithiation/delithiation. By observing a simultaneous increase of both optical transmittance and DC conductivity, strikingly different from other materials, we proposed its application as a next generation transparent electrode.
2d-retrieval For Mipas-envisat
NASA Astrophysics Data System (ADS)
Steck, T.; von Clarmann, T.; Grabowski, U.; Höpfner, M.
Limb sounding of the Earth's atmosphere provides vertically high resolved profiles of geophysical parameters. The long ray path through the atmosphere makes limb sounders sensitive to even little abundant species. On the other hand, horizontal in- homogeneities, if not taken into account properly, can cause systematic errors within the retrieval process. Especially for limb emission measurements in the mid IR, at- mopheric temperature gradients result in considerable vmr retrieval errors if they are neglected. We present a dedicated method of taking full 2D fields of state parameters (indepen- dent of tangent points) into account in the forward model and in the retrieval. The basic idea is that the 2D state vector is updated sequentially for each limb scan. This method is applied to the 2D retrieval of temperature and vmr for simulated radiances as expected from MIPAS-ENVISAT.
Genetics, genomics, and evolutionary biology of NKG2D ligands.
Carapito, Raphael; Bahram, Seiamak
2015-09-01
Human and mouse NKG2D ligands (NKG2DLs) are absent or only poorly expressed by most normal cells but are upregulated by cell stress, hence, alerting the immune system in case of malignancy or infection. Although these ligands are numerous and highly variable (at genetic, genomic, structural, and biochemical levels), they all belong to the major histocompatibility complex class I gene superfamily and bind to a single, invariant, receptor: NKG2D. NKG2D (CD314) is an activating receptor expressed on NK cells and subsets of T cells that have a key role in the recognition and lysis of infected and tumor cells. Here, we review the molecular diversity of NKG2DLs, discuss the increasing appreciation of their roles in a variety of medical conditions, and propose several explanations for the evolutionary force(s) that seem to drive the multiplicity and diversity of NKG2DLs while maintaining their interaction with a single invariant receptor.
Graphene based 2D-materials for supercapacitors
NASA Astrophysics Data System (ADS)
Palaniselvam, Thangavelu; Baek, Jong-Beom
2015-09-01
Ever-increasing energy demands and the depletion of fossil fuels are compelling humanity toward the development of suitable electrochemical energy conversion and storage devices to attain a more sustainable society with adequate renewable energy and zero environmental pollution. In this regard, supercapacitors are being contemplated as potential energy storage devices to afford cleaner, environmentally friendly energy. Recently, a great deal of attention has been paid to two-dimensional (2D) nanomaterials, including 2D graphene and its inorganic analogues (transition metal double layer hydroxides, chalcogenides, etc), as potential electrodes for the development of supercapacitors with high electrochemical performance. This review provides an overview of the recent progress in using these graphene-based 2D materials as potential electrodes for supercapacitors. In addition, future research trends including notable challenges and opportunities are also discussed.
Chemical vapour deposition: Transition metal carbides go 2D
Gogotsi, Yury
2015-08-17
Here, the research community has been steadily expanding the family of few-atom-thick crystals beyond graphene, discovering new materials or producing known materials in a 2D state and demonstrating their unique properties1, 2. Recently, nanometre-thin 2D transition metal carbides have also joined this family3. Writing in Nature Materials, Chuan Xu and colleagues now report a significant advance in the field, showing the synthesis of large-area, high-quality, nanometre-thin crystals of molybdenum carbide that demonstrate low-temperature 2D superconductivity4. Moreover, they also show that other ultrathin carbide crystals, such as tungsten and tantalum carbides, can be grown by chemical vapour deposition with a highmore » crystallinity and very low defect concentration.« less
Optoelectronics based on 2D TMDs and heterostructures
NASA Astrophysics Data System (ADS)
Huo, Nengjie; Yang, Yujue; Li, Jingbo
2017-03-01
2D materials including graphene and TMDs have proven interesting physical properties and promising optoelectronic applications. We reviewed the growth, characterization and optoelectronics based on 2D TMDs and their heterostructures, and demonstrated their unique and high quality of performances. For example, we observed the large mobility, fast response and high photo-responsivity in MoS2, WS2 and WSe2 phototransistors, as well as the novel performances in vdW heterostructures such as the strong interlayer coupling, am-bipolar and rectifying behaviour, and the obvious photovoltaic effect. It is being possible that 2D family materials could play an increasingly important role in the future nano- and opto-electronics, more even than traditional semiconductors such as silicon.
Applications of Doppler Tomography in 2D and 3D
NASA Astrophysics Data System (ADS)
Richards, M.; Budaj, J.; Agafonov, M.; Sharova, O.
2010-12-01
Over the past few years, the applications of Doppler tomography have been extended beyond the usual calculation of 2D velocity images of circumstellar gas flows. This technique has now been used with the new Shellspec spectrum synthesis code to demonstrate the effective modeling of the accretion disk and gas stream in the TT Hya Algol binary. The 2D tomography procedure projects all sources of emission onto a single central (Vx, Vy) velocity plane even though the gas is expected to flow beyond that plane. So, new 3D velocity images were derived with the Radioastronomical Approach method by assuming a grid of Vz values transverse to the central 2D plane. The 3D approach has been applied to the U CrB and RS Vul Algol-type binaries to reveal substantial flow structures beyond the central velocity plane.
Chemical vapour deposition: Transition metal carbides go 2D
Gogotsi, Yury
2015-08-17
Here, the research community has been steadily expanding the family of few-atom-thick crystals beyond graphene, discovering new materials or producing known materials in a 2D state and demonstrating their unique properties^{1, 2}. Recently, nanometre-thin 2D transition metal carbides have also joined this family^{3}. Writing in Nature Materials, Chuan Xu and colleagues now report a significant advance in the field, showing the synthesis of large-area, high-quality, nanometre-thin crystals of molybdenum carbide that demonstrate low-temperature 2D superconductivity^{4}. Moreover, they also show that other ultrathin carbide crystals, such as tungsten and tantalum carbides, can be grown by chemical vapour deposition with a high crystallinity and very low defect concentration.
Real-time 2-D temperature imaging using ultrasound.
Liu, Dalong; Ebbini, Emad S
2010-01-01
We have previously introduced methods for noninvasive estimation of temperature change using diagnostic ultrasound. The basic principle was validated both in vitro and in vivo by several groups worldwide. Some limitations remain, however, that have prevented these methods from being adopted in monitoring and guidance of minimally invasive thermal therapies, e.g., RF ablation and high-intensity-focused ultrasound (HIFU). In this letter, we present first results from a real-time system for 2-D imaging of temperature change using pulse-echo ultrasound. The front end of the system is a commercially available scanner equipped with a research interface, which allows the control of imaging sequence and access to the RF data in real time. A high-frame-rate 2-D RF acquisition mode, M2D, is used to capture the transients of tissue motion/deformations in response to pulsed HIFU. The M2D RF data is streamlined to the back end of the system, where a 2-D temperature imaging algorithm based on speckle tracking is implemented on a graphics processing unit. The real-time images of temperature change are computed on the same spatial and temporal grid of the M2D RF data, i.e., no decimation. Verification of the algorithm was performed by monitoring localized HIFU-induced heating of a tissue-mimicking elastography phantom. These results clearly demonstrate the repeatability and sensitivity of the algorithm. Furthermore, we present in vitro results demonstrating the possible use of this algorithm for imaging changes in tissue parameters due to HIFU-induced lesions. These results clearly demonstrate the value of the real-time data streaming and processing in monitoring, and guidance of minimally invasive thermotherapy.
Towards functional assembly of 3D and 2D nanomaterials
NASA Astrophysics Data System (ADS)
Jacobs, Christopher B.; Wang, Kai; Ievlev, Anton V.; Muckley, Eric S.; Ivanov, Ilia N.
2016-09-01
Functional assemblies of materials can be realized by tuning the work function and band gap of nanomaterials by rational material selection and design. Here we demonstrate the structural assembly of 2D and 3D nanomaterials and show that layering a 2D material monolayer on a 3D metal oxide leads to substantial alteration of both the surface potential and optical properties of the 3D material. A 40 nm thick film of polycrystalline NiO was produced by room temperature rf-sputtering, resulting in a 3D nanoparticle assembly. Chemical vapor deposition (CVD) grown 10-30 μm WS2 flakes (2D material) were placed on the NiO surface using a PDMS stamp transfer technique. The 2D/3D WS2/NiO assembly was characterized using confocal micro Raman spectroscopy to evaluate the vibrational properties and using Kelvin probe force microscopy (KPFM) to evaluate the surface potential. Raman maps of the 2D/3D assembly show spatial non-uniformity of the A1g mode ( 418 cm-1) and the disorder-enhanced longitudinal acoustic mode, 2LA(M) ( 350 cm-1), suggesting that the WS2 exists in a strained condition on when transferred onto 3D polycrystalline NiO. KPFM measurements show that single layer WS2 on SiO2 has a surface potential 75 mV lower than that of SiO2, whereas the surface potential of WS2 on NiO is 15 mV higher than NiO, indicating that WS2 could act as electron donor or acceptor depending on the 3D material it is interfaced with. Thus 2D and 3D materials can be organized into functional assemblies with electron flow controlled by the WS2 either as the electron donor or acceptor.
Mirus, B.B.; Perkins, K.S.; Nimmo, J.R.; Singha, K.
2009-01-01
To understand their relation to pedogenic development, soil hydraulic properties in the Mojave Desert were investi- gated for three deposit types: (i) recently deposited sediments in an active wash, (ii) a soil of early Holocene age, and (iii) a highly developed soil of late Pleistocene age. Eff ective parameter values were estimated for a simplifi ed model based on Richards' equation using a fl ow simulator (VS2D), an inverse algorithm (UCODE-2005), and matric pressure and water content data from three ponded infi ltration experiments. The inverse problem framework was designed to account for the eff ects of subsurface lateral spreading of infi ltrated water. Although none of the inverse problems converged on a unique, best-fi t parameter set, a minimum standard error of regression was reached for each deposit type. Parameter sets from the numerous inversions that reached the minimum error were used to develop probability distribu tions for each parameter and deposit type. Electrical resistance imaging obtained for two of the three infi ltration experiments was used to independently test fl ow model performance. Simulations for the active wash and Holocene soil successfully depicted the lateral and vertical fl uxes. Simulations of the more pedogenically developed Pleistocene soil did not adequately replicate the observed fl ow processes, which would require a more complex conceptual model to include smaller scale heterogeneities. The inverse-modeling results, however, indicate that with increasing age, the steep slope of the soil water retention curve shitis toward more negative matric pressures. Assigning eff ective soil hydraulic properties based on soil age provides a promising framework for future development of regional-scale models of soil moisture dynamics in arid environments for land-management applications. ?? Soil Science Society of America.
Laboratory Experiments On Continually Forced 2d Turbulence
NASA Astrophysics Data System (ADS)
Wells, M. G.; Clercx, H. J. H.; Van Heijst, G. J. F.
There has been much recent interest in the advection of tracers by 2D turbulence in geophysical flows. While there is a large body of literature on decaying 2D turbulence or forced 2D turbulence in unbounded domains, there have been very few studies of forced turbulence in bounded domains. In this study we present new experimental results from a continuously forced quasi 2D turbulent field. The experiments are performed in a square Perspex tank filled with water. The flow is made quasi 2D by a steady background rotation. The rotation rate of the tank has a small (<8 %) sinusoidal perturbation which leads to the periodic formation of eddies in the corners of the tank. When the oscillation period of the perturbation is greater than an eddy roll-up time-scale, dipole structures are observed to form. The dipoles can migrate away from the walls, and the interior of the tank is continually filled with vortexs. From experimental visualizations the length scale of the vortexs appears to be largely controlled by the initial formation mechanism and large scale structures are not observed to form at large times. Thus the experiments provide a simple way of cre- ating a continuously forced 2D turbulent field. The resulting structures are in contrast with most previous laboratory experiments on 2D turbulence which have investigated decaying turbulence and have observed the formations of large scale structure. In these experiments, decaying turbulence had been produced by a variety of methods such as the decaying turbulence in the wake of a comb of rods (Massen et al 1999), organiza- tion of vortices in thin conducting liquids (Cardoso et al 1994) or in rotating systems where there are sudden changes in angular rotation rate (Konijnenberg et al 1998). Results of dye visualizations, particle tracking experiments and a direct numerical simulation will be presented and discussed in terms of their oceanographic application. Bibliography Cardoso,O. Marteau, D. &Tabeling, P
2dF grows up: Echidna for the AAT
NASA Astrophysics Data System (ADS)
McGrath, Andrew; Barden, Sam; Miziarski, Stan; Rambold, William; Smith, Greg
2008-07-01
We present the concept design of a new fibre positioner and spectrograph system for the Anglo-Australian Telescope, as a proposed enhancement to the Anglo-Australian Observatory's well-known 2dF facility. A four-fold multiplex enhancement is accomplished by replacing the 400-fibre 2dF fibre positioning robot with a 1600-fibre Echidna unit, feeding three clones of the AAOmega optical spectrograph. Such a facility has the capability of a redshift 1 survey of a large fraction of the southern sky, collecting five to ten thousand spectra per night for a million-galaxy survey.
Noninvasive deep Raman detection with 2D correlation analysis
NASA Astrophysics Data System (ADS)
Kim, Hyung Min; Park, Hyo Sun; Cho, Youngho; Jin, Seung Min; Lee, Kang Taek; Jung, Young Mee; Suh, Yung Doug
2014-07-01
The detection of poisonous chemicals enclosed in daily necessaries is prerequisite essential for homeland security with the increasing threat of terrorism. For the detection of toxic chemicals, we combined a sensitive deep Raman spectroscopic method with 2D correlation analysis. We obtained the Raman spectra from concealed chemicals employing spatially offset Raman spectroscopy in which incident line-shaped light experiences multiple scatterings before being delivered to inner component and yielding deep Raman signal. Furthermore, we restored the pure Raman spectrum of each component using 2D correlation spectroscopic analysis with chemical inspection. Using this method, we could elucidate subsurface component under thick powder and packed contents in a bottle.
Evaluation of 2D ceramic matrix composites in aeroconvective environments
NASA Technical Reports Server (NTRS)
Riccitiello, Salvatore R.; Love, Wendell L.; Balter-Peterson, Aliza
1992-01-01
An evaluation is conducted of a novel ceramic-matrix composite (CMC) material system for use in the aeroconvective-heating environments encountered by the nose caps and wing leading edges of such aerospace vehicles as the Space Shuttle, during orbit-insertion and reentry from LEO. These CMCs are composed of an SiC matrix that is reinforced with Nicalon, Nextel, or carbon refractory fibers in a 2D architecture. The test program conducted for the 2D CMCs gave attention to their subsurface oxidation.
Quantum process tomography by 2D fluorescence spectroscopy
Pachón, Leonardo A.; Marcus, Andrew H.; Aspuru-Guzik, Alán
2015-06-07
Reconstruction of the dynamics (quantum process tomography) of the single-exciton manifold in energy transfer systems is proposed here on the basis of two-dimensional fluorescence spectroscopy (2D-FS) with phase-modulation. The quantum-process-tomography protocol introduced here benefits from, e.g., the sensitivity enhancement ascribed to 2D-FS. Although the isotropically averaged spectroscopic signals depend on the quantum yield parameter Γ of the doubly excited-exciton manifold, it is shown that the reconstruction of the dynamics is insensitive to this parameter. Applications to foundational and applied problems, as well as further extensions, are discussed.
Experimental validation of equations for 2D DIC uncertainty quantification.
Reu, Phillip L.; Miller, Timothy J.
2010-03-01
Uncertainty quantification (UQ) equations have been derived for predicting matching uncertainty in two-dimensional image correlation a priori. These equations include terms that represent the image noise and image contrast. Researchers at the University of South Carolina have extended previous 1D work to calculate matching errors in 2D. These 2D equations have been coded into a Sandia National Laboratories UQ software package to predict the uncertainty for DIC images. This paper presents those equations and the resulting error surfaces for trial speckle images. Comparison of the UQ results with experimentally subpixel-shifted images is also discussed.
Scale Invariance in 2D BCS-BEC Crossover
NASA Astrophysics Data System (ADS)
Sensarma, Rajdeep; Taylor, Edward; Randeria, Mohit
2013-03-01
In 2D BCS-BEC crossover, the frequency of the breathing mode in a harmonic trap, as well as the lower edge of the radio frequency spectroscopy response, show remarkable scale-invariance throughout the crossover regime, i.e. they are independent of the coupling constant. Using functional integral methods, we study the behaviour of these quantities in the 2D BCS-BEC crossover and comment on the possible reasons for this scale independence. RS was supported by DAE, Govt. of India. MR was supported by NSF Grant No. DMR-1006532. ET was supported by NSERC and the Canadian Institute for Advanced Research.
Closed-shell and open-shell 2D nanographenes.
Sun, Zhe; Wu, Jishan
2014-01-01
This chapter describes a series of two-dimensional (2D) expanded arene networks, also known as nanographenes, with either closed-shell or open-shell electronic structure in the ground state. These systems are further categorized into three classes on a basis of different edge structures: those with zigzag edges only, those with armchair edges only, and those possessing both. Distinctive physical properties of these 2D aromatic systems are closely related to their structural characteristics and provide great potential for them as materials for different applications.
2D Log-Gabor Wavelet Based Action Recognition
NASA Astrophysics Data System (ADS)
Li, Ning; Xu, De
The frequency response of log-Gabor function matches well the frequency response of primate visual neurons. In this letter, motion-salient regions are extracted based on the 2D log-Gabor wavelet transform of the spatio-temporal form of actions. A supervised classification technique is then used to classify the actions. The proposed method is robust to the irregular segmentation of actors. Moreover, the 2D log-Gabor wavelet permits more compact representation of actions than the recent neurobiological models using Gabor wavelet.
Rowley-Neale, Samuel J; Fearn, Jamie M; Brownson, Dale A C; Smith, Graham C; Ji, Xiaobo; Banks, Craig E
2016-08-21
Two-dimensional molybdenum disulphide nanosheets (2D-MoS2) have proven to be an effective electrocatalyst, with particular attention being focused on their use towards increasing the efficiency of the reactions associated with hydrogen fuel cells. Whilst the majority of research has focused on the Hydrogen Evolution Reaction (HER), herein we explore the use of 2D-MoS2 as a potential electrocatalyst for the much less researched Oxygen Reduction Reaction (ORR). We stray from literature conventions and perform experiments in 0.1 M H2SO4 acidic electrolyte for the first time, evaluating the electrochemical performance of the ORR with 2D-MoS2 electrically wired/immobilised upon several carbon based electrodes (namely; Boron Doped Diamond (BDD), Edge Plane Pyrolytic Graphite (EPPG), Glassy Carbon (GC) and Screen-Printed Electrodes (SPE)) whilst exploring a range of 2D-MoS2 coverages/masses. Consequently, the findings of this study are highly applicable to real world fuel cell applications. We show that significant improvements in ORR activity can be achieved through the careful selection of the underlying/supporting carbon materials that electrically wire the 2D-MoS2 and utilisation of an optimal mass of 2D-MoS2. The ORR onset is observed to be reduced to ca. +0.10 V for EPPG, GC and SPEs at 2D-MoS2 (1524 ng cm(-2) modification), which is far closer to Pt at +0.46 V compared to bare/unmodified EPPG, GC and SPE counterparts. This report is the first to demonstrate such beneficial electrochemical responses in acidic conditions using a 2D-MoS2 based electrocatalyst material on a carbon-based substrate (SPEs in this case). Investigation of the beneficial reaction mechanism reveals the ORR to occur via a 4 electron process in specific conditions; elsewhere a 2 electron process is observed. This work offers valuable insights for those wishing to design, fabricate and/or electrochemically test 2D-nanosheet materials towards the ORR.
3D inversion based on multi-grid approach of magnetotelluric data from Northern Scandinavia
NASA Astrophysics Data System (ADS)
Cherevatova, M.; Smirnov, M.; Korja, T. J.; Egbert, G. D.
2012-12-01
solver is implemented within the framework of the modular system for EM inversion (ModEM by G. Egbert, A. Kelbert, N. Meqbel), using the ModEM 3D finite difference staggered grid forward solver (second order PDE in the electric field, with divergence correction) as a starting point for our development. The first 3D inversion model for the crust and upper mantle shows the highly conducting bodies in the crust which can be interpreted as alum shales. The eastern and central parts are presented by resistive Precambrian rocks of the Svecofennian and Archaean domains. The upper mantle is resistive and relates to the Baltica basement. We also compare 3D inversion model with the results of 2D inversion along several profiles. We are able to explain some of the features in the data (out of quadrant phase) with 3D model, thus providing more reliable results compared to routine 2D approach.
Impact of Nanosize on Supercapacitance: Study of 1D Nanorods and 2D Thin-Films of Nickel Oxide.
Patil, Ranjit A; Chang, Cheng-Ping; Devan, Rupesh S; Liou, Yung; Ma, Yuan-Ron
2016-04-20
We synthesized unique one-dimensional (1D) nanorods and two-dimensional (2D) thin-films of NiO on indium-tin-oxide thin-films using a hot-filament metal-oxide vapor deposition technique. The 1D nanorods have an average width and length of ∼100 and ∼500 nm, respectively, and the densely packed 2D thin-films have an average thickness of ∼500 nm. The 1D nanorods perform as parallel units for charge storing. However, the 2D thin-films act as one single unit for charge storing. The 2D thin-films possess a high specific capacitance of ∼746 F/g compared to 1D nanorods (∼230 F/g) using galvanostatic charge-discharge measurements at a current density of 3 A/g. Because the 1D NiO nanorods provide more plentiful surface areas than those of the 2D thin-films, they are fully active at the first few cycles. However, the capacitance retention of the 1D nanorods decays faster than that of the 2D thin-films. Also, the 1D NiO nanorods suffer from instability due to the fast electrochemical dissolution and high nanocontact resistance. Electrochemical impedance spectroscopy verifies that the low dimensionality of the 1D NiO nanorods induces the unavoidable effects that lead them to have poor supercapacitive performances. On the other hand, the slow electrochemical dissolution and small contact resistance in the 2D NiO thin-films favor to achieve high specific capacitance and great stability.
NASA Astrophysics Data System (ADS)
Lin, Zhong; McCreary, Amber; Briggs, Natalie; Subramanian, Shruti; Zhang, Kehao; Sun, Yifan; Li, Xufan; Borys, Nicholas J.; Yuan, Hongtao; Fullerton-Shirey, Susan K.; Chernikov, Alexey; Zhao, Hui; McDonnell, Stephen; Lindenberg, Aaron M.; Xiao, Kai; LeRoy, Brian J.; Drndić, Marija; Hwang, James C. M.; Park, Jiwoong; Chhowalla, Manish; Schaak, Raymond E.; Javey, Ali; Hersam, Mark C.; Robinson, Joshua; Terrones, Mauricio
2016-12-01
The rise of two-dimensional (2D) materials research took place following the isolation of graphene in 2004. These new 2D materials include transition metal dichalcogenides, mono-elemental 2D sheets, and several carbide- and nitride-based materials. The number of publications related to these emerging materials has been drastically increasing over the last five years. Thus, through this comprehensive review, we aim to discuss the most recent groundbreaking discoveries as well as emerging opportunities and remaining challenges. This review starts out by delving into the improved methods of producing these new 2D materials via controlled exfoliation, metal organic chemical vapor deposition, and wet chemical means. We look into recent studies of doping as well as the optical properties of 2D materials and their heterostructures. Recent advances towards applications of these materials in 2D electronics are also reviewed, and include the tunnel MOSFET and ways to reduce the contact resistance for fabricating high-quality devices. Finally, several unique and innovative applications recently explored are discussed as well as perspectives of this exciting and fast moving field.
Joint inversion of Wenner and dipole-dipole data to study a gasoline-contaminated soil
NASA Astrophysics Data System (ADS)
de la Vega, Matías; Osella, Ana; Lascano, Eugenia
2003-11-01
The goal of this work was to study a contaminated soil due to a gasoline spill produced by fissures in a concrete purge chamber located along a gas transmission line. A monitoring well drilled 16 m down gradient from the purge chamber revealed the presence of a gasoline layer of 0.5 m thick at 1.5 m depth, floating on top of the water table. A second well, drilled 30 m away from the first well, and in the same direction, did not show any evidence of contamination. To investigate this problem, a geoelectrical survey was conducted, combining dipole-dipole and Wenner arrays. First, four dipole-dipole profiles in a direction perpendicular to the longitudinal axis joining the wells were carried out. The electrical tomographies obtained from the 2D inversion of the data showed that the contaminated region was characterized by a resistive plume located at a depth between 1 to 2 m and had lateral extent of about 6-8 m. The longitudinal extension was less than 20 m, since the last profile located 30 m farther from the chamber did not show this kind of anomaly. To better determine the longitudinal extension, we performed a dipole-dipole profile along a line in this direction. The inverse model confirmed that the extension of the contaminated section was about 16 m. To complete the study of the deeper layer, we carried out Wenner soundings. The results of the inversion process indicated that to a depth of 20 m the soil was very conductive, because of the presence of clays as the main constituents, which confine the contaminant within this impermeable surrounding. To improve the inverse model, we performed a joint inversion of dipole-dipole and Wenner data. Analysis of the depth of penetration showed that it increased to 25 m and comparing the resulting model with the ones obtained from each array separately, we concluded that the joint inversion improves the depth obtained by the survey, while maintaining the shallow lateral resolution.
Electronic Transport Properties of New 2-D Materials GeH and NaSn2As2
NASA Astrophysics Data System (ADS)
He, Bin; Cultrara, Nicholas; Arguilla, Maxx; Goldberger, Joshua; Heremans, Joseph
2-D materials potentially have superior thermoelectric properties compared to traditional 3-D materials due to their layered structure. Here we present electrical and thermoelectric transport properties of 2 types of 2-D materials, GeH and NaSn2As2. GeH is a graphane analog which is prepared using chemical exfoliation of CaGe2 crystals. Intrinsic GeH is proven to be a highly resistive material at room temperature. Resistance and Seebeck coefficient of Ga doped GeH are measured in a cryostat with a gating voltage varying from -100V to 100V. NaSn2As2 is another 2-D system, with Na atom embedded between nearly-2D Sn-As layers. Unlike GeH, NaSn2As2 is a metal based of Hall measurements, with p-type behavior, and with van der Pauw resistances on the order of 5m Ω/square. Thermoelectric transport properties of NaSn2As2 will be reported. This work is support by the NSF EFRI-2DARE project EFRI-1433467.
NASA Astrophysics Data System (ADS)
Iryanti, Mimin; Srigutomo, Wahyu; Bijaksana, Satria; Setiawan, Tedy
2016-08-01
Lembang Fault is a normal fault situated at the southern flank of Tangkuban Parahu Volcano in West Java Indonesia. The fault's movement may have caused the formation of sag pond in the vicinity of its which is characterized by the soil layers of the sag pond. The characteristics of the soil can be examined based on its electrical properties such as conductivity (the inverse of resistivity) and dielectric permittivity. Direct field measurement was conducted using DC-resistivity Wenner-Schlumberger method on the sag pond as well as laboratory resistivity measurement of cores taken from the sag pond. Two resistivity crosssections were obtained after performing 2D inversion of the data which reveal that the resistivity distribution consist of a resistive layer (40-60 ohm.m) overlying a medium resistive layer (30-35 ohm.m). The third layer has relatively low resistivity of 16-25 ohm.m. At the intersection of these two lines we took coring samples down to depth of 5 m below surface and measured the electrical conductivity and dielectric permittivity for each 1 cm of sample using EM-50 data logger. Results from both field and laboratory measurement were analysed to get a better understanding of the sag pond.
2D:4D Asymmetry and Gender Differences in Academic Performance
Nye, John V. C.; Androuschak, Gregory; Desierto, Desirée; Jones, Garett; Yudkevich, Maria
2012-01-01
Exposure to prenatal androgens affects both future behavior and life choices. However, there is still relatively limited evidence on its effects on academic performance. Moreover, the predicted effect of exposure to prenatal testosterone (T)–which is inversely correlated with the relative length of the second to fourth finger lengths (2D:4D)–would seem to have ambiguous effects on academic achievement since traits like aggressiveness or risk-taking are not uniformly positive for success in school. We provide the first evidence of a non-linear, quadratic, relationship between 2D:4D and academic achievement using samples from Moscow and Manila. We also find that there is a gender differentiated link between various measures of academic achievement and measured digit ratios. These effects are different depending on the field of study, choice of achievement measure, and use of the right hand or left digit ratios. The results seem to be asymmetric between Moscow and Manila where the right (left) hand generates inverted-U (U-shaped) curves in Moscow while the pattern for hands reverses in Manila. Drawing from unusually large and detailed samples of university students in two countries not studied in the digit literature, our work is the first to have a large cross country comparison that includes two groups with very different ethnic compositions. PMID:23056282
2D:4D asymmetry and gender differences in academic performance.
Nye, John V C; Androuschak, Gregory; Desierto, Desirée; Jones, Garett; Yudkevich, Maria
2012-01-01
Exposure to prenatal androgens affects both future behavior and life choices. However, there is still relatively limited evidence on its effects on academic performance. Moreover, the predicted effect of exposure to prenatal testosterone (T)-which is inversely correlated with the relative length of the second to fourth finger lengths (2D:4D)-would seem to have ambiguous effects on academic achievement since traits like aggressiveness or risk-taking are not uniformly positive for success in school. We provide the first evidence of a non-linear, quadratic, relationship between 2D:4D and academic achievement using samples from Moscow and Manila. We also find that there is a gender differentiated link between various measures of academic achievement and measured digit ratios. These effects are different depending on the field of study, choice of achievement measure, and use of the right hand or left digit ratios. The results seem to be asymmetric between Moscow and Manila where the right (left) hand generates inverted-U (U-shaped) curves in Moscow while the pattern for hands reverses in Manila. Drawing from unusually large and detailed samples of university students in two countries not studied in the digit literature, our work is the first to have a large cross country comparison that includes two groups with very different ethnic compositions.
Weinger, Jason G; Plaisted, Warren C; Maciejewski, Sonia M; Lanier, Lewis L; Walsh, Craig M; Lane, Thomas E
2014-10-01
Transplantation of major histocompatibility complex-mismatched mouse neural precursor cells (NPCs) into mice persistently infected with the neurotropic JHM strain of mouse hepatitis virus (JHMV) results in rapid rejection that is mediated, in part, by T cells. However, the contribution of the innate immune response to allograft rejection in a model of viral-induced neurological disease has not been well defined. Herein, we demonstrate that the natural killer (NK) cell-expressing-activating receptor NKG2D participates in transplanted allogeneic NPC rejection in mice persistently infected with JHMV. Cultured NPCs derived from C57BL/6 (H-2(b) ) mice express the NKG2D ligand retinoic acid early precursor transcript (RAE)-1 but expression was dramatically reduced upon differentiation into either glia or neurons. RAE-1(+) NPCs were susceptible to NK cell-mediated killing whereas RAE-1(-) cells were resistant to lysis. Transplantation of C57BL/6-derived NPCs into JHMV-infected BALB/c (H-2(d) ) mice resulted in infiltration of NKG2D(+) CD49b(+) NK cells and treatment with blocking antibody specific for NKG2D increased survival of allogeneic NPCs. Furthermore, transplantation of differentiated RAE-1(-) allogeneic NPCs into JHMV-infected BALB/c mice resulted in enhanced survival, highlighting a role for the NKG2D/RAE-1 signaling axis in allograft rejection. We also demonstrate that transplantation of allogeneic NPCs into JHMV-infected mice resulted in infection of the transplanted cells suggesting that these cells may be targets for infection. Viral infection of cultured cells increased RAE-1 expression, resulting in enhanced NK cell-mediated killing through NKG2D recognition. Collectively, these results show that in a viral-induced demyelination model, NK cells contribute to rejection of allogeneic NPCs through an NKG2D signaling pathway.
Discrepant Results in a 2-D Marble Collision
ERIC Educational Resources Information Center
Kalajian, Peter
2013-01-01
Video analysis of 2-D collisions is an excellent way to investigate conservation of linear momentum. The often-desired experimental design goal is to minimize the momentum loss in order to demonstrate the conservation law. An air table with colliding pucks is an ideal medium for this experiment, but such equipment is beyond the budget of many…
2-D Finite Element Cable and Box IEMP Analysis
Scivner, G.J.; Turner, C.D.
1998-12-17
A 2-D finite element code has been developed for the solution of arbitrary geometry cable SGEMP and box IEMP problems. The quasi- static electric field equations with radiation- induced charge deposition and radiation-induced conductivity y are numerically solved on a triangular mesh. Multiple regions of different dielectric materials and multiple conductors are permitted.
2D Orthogonal Locality Preserving Projection for Image Denoising.
Shikkenawis, Gitam; Mitra, Suman K
2016-01-01
Sparse representations using transform-domain techniques are widely used for better interpretation of the raw data. Orthogonal locality preserving projection (OLPP) is a linear technique that tries to preserve local structure of data in the transform domain as well. Vectorized nature of OLPP requires high-dimensional data to be converted to vector format, hence may lose spatial neighborhood information of raw data. On the other hand, processing 2D data directly, not only preserves spatial information, but also improves the computational efficiency considerably. The 2D OLPP is expected to learn the transformation from 2D data itself. This paper derives mathematical foundation for 2D OLPP. The proposed technique is used for image denoising task. Recent state-of-the-art approaches for image denoising work on two major hypotheses, i.e., non-local self-similarity and sparse linear approximations of the data. Locality preserving nature of the proposed approach automatically takes care of self-similarity present in the image while inferring sparse basis. A global basis is adequate for the entire image. The proposed approach outperforms several state-of-the-art image denoising approaches for gray-scale, color, and texture images.
2D signature for detection and identification of drugs
NASA Astrophysics Data System (ADS)
Trofimov, Vyacheslav A.; Varentsova, Svetlana A.; Shen, Jingling; Zhang, Cunlin; Zhou, Qingli; Shi, Yulei
2011-06-01
The method of spectral dynamics analysis (SDA-method) is used for obtaining the2D THz signature of drugs. This signature is used for the detection and identification of drugs with similar Fourier spectra by transmitted THz signal. We discuss the efficiency of SDA method for the identification problem of pure methamphetamine (MA), methylenedioxyamphetamine (MDA), 3, 4-methylenedioxymethamphetamine (MDMA) and Ketamine.
Optoelectronics of supported and suspended 2D semiconductors
NASA Astrophysics Data System (ADS)
Bolotin, Kirill
2014-03-01
Two-dimensional semiconductors, materials such monolayer molybdenum disulfide (MoS2) are characterized by strong spin-orbit and electron-electron interactions. However, both electronic and optoelectronic properties of these materials are dominated by disorder-related scattering. In this talk, we investigate approaches to reduce scattering and explore physical phenomena arising in intrinsic 2D semiconductors. First, we discuss fabrication of pristine suspended monolayer MoS2 and use photocurrent spectroscopy measurements to study excitons in this material. We observe band-edge and van Hove singularity excitons and estimate their binding energies. Furthermore, we study dissociation of these excitons and uncover the mechanism of their contribution to photoresponse of MoS2. Second, we study strain-induced modification of bandstructures of 2D semiconductors. With increasing strain, we find large and controllable band gap reduction of both single- and bi-layer MoS2. We also detect experimental signatures consistent with strain-induced transition from direct to indirect band gap in monolayer MoS2. Finally, we fabricate heterostructures of dissimilar 2D semiconductors and study their photoresponse. For closely spaced 2D semiconductors we detect charge transfer, while for separation larger than 10nm we observe Forster-like energy transfer between excitations in different layers.
Graphene band structure and its 2D Raman mode
NASA Astrophysics Data System (ADS)
Narula, Rohit; Reich, Stephanie
2014-08-01
High-precision simulations are used to generate the 2D Raman mode of graphene under a range of screening conditions and laser energies EL. We reproduce the decreasing trend of the 2D mode FWHM vs EL and the nearly linearly increasing dispersion ∂ω2D/∂EL seen experimentally in freestanding (unscreened) graphene, and propose relations between these experimentally accessible quantities and the local, two-dimensional gradients |∇ | of the electronic and TO phonon bands. In light of state-of-the-art electronic structure calculations that acutely treat the long-range e-e interactions of isolated graphene and its experimentally observed 2D Raman mode, our calculations determine a 40% greater slope of the TO phonons about K than given by explicit phonon measurements performed in graphite or GW phonon calculations in graphene. We also deduce the variation of the broadening energy γ [EL] for freestanding graphene and find a nominal value γ ˜140 meV, showing a gradually increasing trend for the range of frequencies available experimentally.
Development of a MEMS 2D separations device
NASA Astrophysics Data System (ADS)
Bloschock, Kristen P.; Flyer, Jonathan N.; Schneider, Thomas W.; Hussam, Abul; Van Keuren, Edward R.
2004-12-01
A polymer based biochip for rapid 2D separations of peptides, proteins, and other biomedically relevant molecules was designed and fabricated. Like traditional 2D polyacrylamide gel electrophoresis (2D-PAGE) methods, the device will allow molecules to separate based on isoelectric point (pI) and molecular weight (MW). Our design, however, integrates both an initial capillary isoelectric focusing (cIEF) step followed by capillary electrophoresis (CE) in multiple parallel channels, all on a single microfluidic chip. Not only is the "lab-on-a-chip" design easier to use and less expensive, but the miniaturization of the device produces very rapid separations. Compared to traditional 2D-PAGE, which can take hours to complete, we estimate separation times on the order of seconds. Fluorescence detection will be used in the preliminary stages of testing, but the device also is equipped with integrated electrodes in the electrophoresis channels to perform multiplexed electrochemical detection for quantitative analysis. We will present preliminary results of the chip development and testing.
The 2dF Galaxy Redshift Survey: Preliminary Results
NASA Astrophysics Data System (ADS)
Maddox, Steve; 2DF Galaxy Redshift Survey Team; Bland-Hawthorn, Joss; Cannon, Russell; Cole, Shaun; Colless, Matthew; Collins, Chris; Couch, Warrick; Dalton, Gavin; Driver, Simon; Ellis, Richard; Efstathiou, George; Folkes, Simon; Frenk, Carlos; Glazebrook, Karl; Kaiser, Nick; Lahav, Ofer; Lumsden, Stuart; Peterson, Bruce; Peacock, John; Sutherland, Will; Taylor, Keith
Spectroscopic observations for a new survey of 250 000 galaxy redshifts are underway, using the 2dF instrument at the AAT. The input galaxy catalogue and commissioning data are described. The first result from the preliminary data is a new estimate of the galaxy luminosity function at
Volume Calculation of Venous Thrombosis Using 2D Ultrasound Images.
Dhibi, M; Puentes, J; Bressollette, L; Guias, B; Solaiman, B
2005-01-01
Venous thrombosis screening exams use 2D ultrasound images, from which medical experts obtain a rough idea of the thrombosis aspect and infer an approximate volume. Such estimation is essential to follow up the thrombosis evolution. This paper proposes a method to calculate venous thrombosis volume from non-parallel 2D ultrasound images, taking advantage of a priori knowledge about the thrombosis shape. An interactive ellipse fitting contour segmentation extracts the 2D thrombosis contours. Then, a Delaunay triangulation is applied to the set of 2D segmented contours positioned in 3D, and the area that each contour defines, to obtain a global thrombosis 3D surface reconstruction, with a dense triangulation inside the contours. Volume is calculated from the obtained surface and contours triangulation, using a maximum unit normal component approach. Preliminary results obtained on 3 plastic phantoms and 3 in vitro venous thromboses, as well as one in vivo case are presented and discussed. An error rate of volume estimation inferior to 4,5% for the plastic phantoms, and 3,5% for the in vitro venous thromboses was obtained.
ELLIPT2D: A Flexible Finite Element Code Written Python
Pletzer, A.; Mollis, J.C.
2001-03-22
The use of the Python scripting language for scientific applications and in particular to solve partial differential equations is explored. It is shown that Python's rich data structure and object-oriented features can be exploited to write programs that are not only significantly more concise than their counter parts written in Fortran, C or C++, but are also numerically efficient. To illustrate this, a two-dimensional finite element code (ELLIPT2D) has been written. ELLIPT2D provides a flexible and easy-to-use framework for solving a large class of second-order elliptic problems. The program allows for structured or unstructured meshes. All functions defining the elliptic operator are user supplied and so are the boundary conditions, which can be of Dirichlet, Neumann or Robbins type. ELLIPT2D makes extensive use of dictionaries (hash tables) as a way to represent sparse matrices.Other key features of the Python language that have been widely used include: operator over loading, error handling, array slicing, and the Tkinter module for building graphical use interfaces. As an example of the utility of ELLIPT2D, a nonlinear solution of the Grad-Shafranov equation is computed using a Newton iterative scheme. A second application focuses on a solution of the toroidal Laplace equation coupled to a magnetohydrodynamic stability code, a problem arising in the context of magnetic fusion research.
Rheological Properties of Quasi-2D Fluids in Microgravity
NASA Technical Reports Server (NTRS)
Stannarius, Ralf; Trittel, Torsten; Eremin, Alexey; Harth, Kirsten; Clark, Noel; Maclennan, Joseph; Glaser, Matthew; Park, Cheol; Hall, Nancy; Tin, Padetha
2015-01-01
In recent years, research on complex fluids and fluids in restricted geometries has attracted much attention in the scientific community. This can be attributed not only to the development of novel materials based on complex fluids but also to a variety of important physical phenomena which have barely been explored. One example is the behavior of membranes and thin fluid films, which can be described by two-dimensional (2D) rheology behavior that is quite different from 3D fluids. In this study, we have investigated the rheological properties of freely suspended films of a th