bluuebunny/crossref_metadata_2025 huggingface dataset:
Exponential Runge-Kutta Methods for the Multispecies Boltzmann Equation
Authors: Li Qin , Yang Xu
Published: July 2016

This paper generalizes the exponential Runge-Kutta asymptotic preserving (AP) method developed in [G. Dimarco and L. Pareschi,SIAM Numer. Anal., 49 (2011), pp. 2057-2077] to compute the multi-species Boltzmann equation. Compared to the single species Boltzmann equation that the method was originally applied on, this set of equation presents a new difficulty that comes from the lack of local conservation laws due to the interaction between different species. Hence extra stiff nonlinear source terms need to be treated properly to maintain the accuracy and the AP property. The method we propose does not contain any nonlinear nonlocal implicit solver, and can capture the hydrodynamic limit with time step and mesh size independent of the Knudsen number. We prove the positivity and strong AP properties of the scheme, which are verified by two numerical examples.
New Splitting Methods for Convection-Dominated Diffusion Problems and Navier-Stokes Equations
Authors: Shi Feng , Liang Guoping , Zhao Yubo , Zou Jun
Published: July 2016

We present a new splitting method for time-dependent convention-dominated diffusion problems. The original convention diffusion system is split into two sub-systems: a pure convection system and a diffusion system. At each time step, a convection problem and a diffusion problem are solved successively. A few important features of the scheme lie in the facts that the convection subproblem is solved explicitly and multistep techniques can be used to essentially enlarge the stability region so that the resulting scheme behaves like an unconditionally stable scheme; while the diffusion subproblem is always self-adjoint and coercive so that they can be solved efficiently using many existing optimal preconditioned iterative solvers. The scheme can be extended for solving the Navier-Stokes equations, where the nonlinearity is resolved by a linear explicit multistep scheme at the convection step, while only a generalized Stokes problem is needed to solve at the diffusion step and the major stiffness matrix stays invariant in the time marching process. Numerical simulations are presented to demonstrate the stability, convergence and performance of the single-step and multistep variants of the new scheme.
IMEX Large Time Step Finite Volume Methods for Low Froude Number Shallow Water Flows
Authors: Bispen Georgij , Arun K. R. , Lukáčová-Medvid’ová Mária , Noelle Sebastian
Published: July 2016

We present new large time step methods for the shallow water flows in the low Froude number limit. In order to take into account multiscale phenomena that typically appear in geophysical flows nonlinear fluxes are split into a linear part governing the gravitational waves and the nonlinear advection. We propose to approximate fast linear waves implicitly in time and in space by means of a genuinely multidimensional evolution operator. On the other hand, we approximate nonlinear advection part explicitly in time and in space by means of the method of characteristics or some standard numerical flux function. Time integration is realized by the implicit-explicit (IMEX) method. We apply the IMEX Euler scheme, two step Runge Kutta Cranck Nicolson scheme, as well as the semi-implicit BDF scheme and prove their asymptotic preserving property in the low Froude number limit. Numerical experiments demonstrate stability, accuracy and robustness of these new large time step finite volume schemes with respect to small Froude number.
Numerical Solution of 3D Poisson-Nernst-Planck Equations Coupled with Classical Density Functional Theory for Modeling Ion and Electron Transport in a Confined Environment
Authors: Meng Da , Zheng Bin , Lin Guang , Sushko Maria L.
Published: July 2016

We have developed efficient numerical algorithms for solving 3D steady-state Poisson-Nernst-Planck (PNP) equations with excess chemical potentials described by the classical density functional theory (cDFT). The coupled PNP equations are discretized by a finite difference scheme and solved iteratively using the Gummel method with relaxation. The Nernst-Planck equations are transformed into Laplace equations through the Slotboom transformation. Then, the algebraic multigrid method is applied to efficiently solve the Poisson equation and the transformed Nernst-Planck equations. A novel strategy for calculating excess chemical potentials through fast Fourier transforms is proposed, which reduces computational complexity from O(N2) to O(NlogN), where N is the number of grid points. Integrals involving the Dirac delta function are evaluated directly by coordinate transformation, which yields more accurate results compared to applying numerical quadrature to an approximated delta function. Numerical results for ion and electron transport in solid electrolyte for lithiumion (Li-ion) batteries are shown to be in good agreement with the experimental data and the results from previous studies.
Efficient Variable-Coefficient Finite-Volume Stokes Solvers
Authors: Cai Mingchao , Nonaka Andy , Bell John B. , Griffith Boyce E. , Donev Aleksandar
Published: July 2016

We investigate several robust preconditioners for solving the saddle-point linear systems that arise from spatial discretization of unsteady and steady variable-coefficient Stokes equations on a uniform staggered grid. Building on the success of using the classical projection method as a preconditioner for the coupled velocity pressure system [B. E. Griffith, J. Comp. Phys., 228 (2009), pp. 7565-7595], as well; established techniques for steady and unsteady Stokes flow in the finite-element literature, we construct preconditioners that employ independent generalized Helmholtz and Poisson solvers for the velocity and pressure subproblems. We demonstrate that only a single cycle of a standard geometric multigrid algorithm serves as an effective inexact solver for each of these subproblems. Contrary to traditional wisdom, we find that the Stokes problem can be solved nearly as efficiently as the independent pressure and velocity subproblems, making the overall cost of solving the Stokes system comparable to the cost of classical projection or fractional step methods for incompressible flow, even for steady flow and in the presence of large density and viscosity contrasts. Two of the five preconditioners considered here are found to be robust to GMRES restarts and to increasing problem size, making them suitable for large-scale problems. Our work opens many possibilities for constructing novel unsplit temporal integrators for finite-volume spatial discretizations of the equations of low Mach and incompressible flow dynamics.
Immersed Interface CIP for One Dimensional Hyperbolic Equations
Authors: Ito Kazufumi , Takeuchi Tomoya
Published: July 2016

The immersed interface technique is incorporated into CIP method to solve one-dimensional hyperbolic equations with piecewise constant coefficients. The proposed method achieves the third order of accuracy in time and space in the vicinity of the interface where the coefficients have jump discontinuities, which is the same order of accuracy of the standard CIP scheme. Some numerical tests are given to verify the accuracy of the proposed method.
Radar Cross Section Reduction of a Cavity in the Ground Plane
Authors: Bao Gang , Lai Jun
Published: July 2016

This paper investigates the reduction of backscatter radar cross section (RCS) for a rectangular cavity embedded in the ground plane. The bottom of the cavity is coated by a thin, multilayered radar absorbing material (RAM) with possibly different permittivities. The objective is to minimize the backscatter RCS by the incidence of a plane wave over a single or a set of incident angles. By formulating the scattering problem as a Helmholtz equation with artificial boundary condition, the gradient with respect to the material permittivities is determined efficiently by the adjoint state method, which is integrated into a nonlinear optimization scheme. Numerical example shows the RCS may be significantly reduced.
A Frequency Determination Method for Digitized NMR Signals
Authors: Yan H. , Li K. , Khatiwada R. , Smith E. , Snow W. M. , Fu C. B. , Chu P.-H. , Gao H. , Zheng W.
Published: July 2016

We present a high precision frequency determination method for digitized NMR FID signals. The method employs high precision numerical integration rather than simple summation as in many other techniques. With no independent knowledge of the other parameters of a NMR FID signal (phase ф, amplitude A, and transverse relaxation time T2) this method can determine the signal frequency f0 with a precision of if the observation time T ≫ T2. The method is especially convenient when the detailed shape of the observed FT NMR spectrum is not well defined. When T2 is +∞ and the signal becomes pure sinusoidal, the precision of the method is which is one order more precise than the ±1 count error induced precision of a typical frequency counter. Analysis of this method shows that the integration reduces the noise by bandwidth narrowing as in a lock-in amplifier, and no extra signal filters are needed. For a pure sinusoidal signal we find from numerical simulations that the noise-induced error in this method reaches the Cramer-Rao Lower Band (CRLB) on frequency determination. For the damped sinusoidal case of most interest, the noise-induced error is found to be within a factor of 2 of CRLB when the measurement time T is 2 or 3 times larger than T2. We discuss possible improvements for the precision of this method.
A High-Order Accurate Gas-Kinetic Scheme for One- and Two-Dimensional Flow Simulation
Authors: Liu Na , Tang Huazhong
Published: July 2016

This paper develops a high-order accurate gas-kinetic scheme in the framework of the finite volume method for the one- and two-dimensional flow simulations, which is an extension of the third-order accurate gas-kinetic scheme [Q.B. Li, K. Xu, and S. Fu, J. Comput. Phys., 229(2010), 6715-6731] and the second-order accurate gas-kinetic scheme [K. Xu, J. Comput. Phys., 171(2001), 289-335]. It is formed by two parts: quartic polynomial reconstruction of the macroscopic variables and fourth-order accurate flux evolution. The first part reconstructs a piecewise cell-center based quartic polynomial and a cell-vertex based quartic polynomial according to the “initial” cell average approximation of macroscopic variables to recover locally the non-equilibrium and equilibrium single particle velocity distribution functions around the cell interface. It is in view of the fact that all macroscopic variables become moments of a single particle velocity distribution function in the gas-kinetic theory. The generalized moment limiter is employed there to suppress the possible numerical oscillation. In the second part, the macroscopic flux at the cell interface is evolved in fourth-order accuracy by means of the simple particle transport mechanism in the microscopic level, i.e. free transport and the Bhatnagar-Gross-Krook (BGK) collisions. In other words, the fourth-order flux evolution is based on the solution (i.e. the particle velocity distribution function) of the BGK model for the Boltzmann equation. Several 1D and 2D test problems are numerically solved by using the proposed high-order accurate gas-kinetic scheme. By comparing with the exact solutions or the numerical solutions obtained the second-order or third-order accurate gas-kinetic scheme, the computations demonstrate that our scheme is effective and accurate for simulating invisid and viscous fluid flows, and the accuracy of the high-order GKS depends on the choice of the (numerical) collision time.
Computational Modeling of Solvent Effects on Protein-Ligand Interactions Using Fully Polarizable Continuum Model and Rational Drug Design
Authors: Zheng Fang , Zhan Chang-Guo
Published: July 2016

This is a brief review of the computational modeling of protein-ligand interactions using a recently developed fully polarizable continuum model (FPCM) and rational drug design. Computational modeling has become a powerful tool in understanding detailed protein-ligand interactions at molecular level and in rational drug design. To study the binding of a protein with multiple molecular species of a ligand, one must accurately determine both the relative free energies of all of the molecular species in solution and the corresponding microscopic binding free energies for all of the molecular species binding with the protein. In this paper, we aim to provide a brief overview of the recent development in computational modeling of the solvent effects on the detailed protein-ligand interactions involving multiple molecular species of a ligand related to rational drug design. In particular, we first briefly discuss the main challenges in computational modeling of the detailed protein-ligand interactions involving the multiple molecular species and then focus on the FPCM model and its applications. The FPCM method allows accurate determination of the solvent effects in the first-principles quantum mechanism (QM) calculations on molecules in solution. The combined use of the FPCM-based QM calculations and other computational modeling and simulations enables us to accurately account for a protein binding with multiple molecular species of a ligand in solution. Based on the computational modeling of the detailed protein-ligand interactions, possible new drugs may be designed rationally as either small-molecule ligands of the protein or engineered proteins that bind/metabolize the ligand. The computational drug design has successfully led to discovery and development of promising drugs.
A Kernel-Free Boundary Integral Method for Variable Coefficients Elliptic PDEs
Authors: Ying Wenjun , Wang Wei-Cheng
Published: July 2016

This work proposes a generalized boundary integral method for variable coefficients elliptic partial differential equations (PDEs), including both boundary value and interface problems. The method is kernel-free in the sense that there is no need to know analytical expressions for kernels of the boundary and volume integrals in the solution of boundary integral equations. Evaluation of a boundary or volume integral is replaced with interpolation of a Cartesian grid based solution, which satisfies an equivalent discrete interface problem, while the interface problem is solved by a fast solver in the Cartesian grid. The computational work involved with the generalized boundary integral method is essentially linearly proportional to the number of grid nodes in the domain. This paper gives implementation details for a second-order version of the kernel-free boundary integral method in two space dimensions and presents numerical experiments to demonstrate the efficiency and accuracy of the method for both boundary value and interface problems. The interface problems demonstrated include those with piecewise constant and large-ratio coefficients and the heterogeneous interface problem, where the elliptic PDEs on two sides of the interface are of different types.
Mathematical and Numerical Aspects of the Adaptive Fast Multipole Poisson-Boltzmann Solver
Authors: Zhang Bo , Lu Benzhuo , Cheng Xiaolin , Huang Jingfang , Pitsianis Nikos P. , Sun Xiaobai , McCammon J. Andrew
Published: July 2016

This paper summarizes the mathematical and numerical theories and computational elements of the adaptive fast multipole Poisson-Boltzmann (AFMPB) solver. We introduce and discuss the following components in order: the Poisson-Boltzmann model, boundary integral equation reformulation, surface mesh generation, the nodepatch discretization approach, Krylov iterative methods, the new version of fast multipole methods (FMMs), and a dynamic prioritization technique for scheduling parallel operations. For each component, we also remark on feasible approaches for further improvements in efficiency, accuracy and applicability of the AFMPB solver to large-scale long-time molecular dynamics simulations. The potential of the solver is demonstrated with preliminary numerical results.
Adaptive hp-Finite Element Computations for Time-Harmonic Maxwell’s Equations
Authors: Jiang Xue , Zhang Linbo , Zheng Weiying
Published: July 2016

In this paper, hp-adaptive finite element methods are studied for time-harmonic Maxwell’s equations. We propose the parallel hp-adaptive algorithms on conforming unstructured tetrahedral meshes based on residual-based a posteriori error estimates. Extensive numerical experiments are reported to investigate the efficiency of the hp-adaptive methods for point singularities, edge singularities, and an engineering benchmark problem of Maxwell’s equations. The hp-adaptive methods show much better performance than the h-adaptive method.
Variable High-Order Multiblock Overlapping Grid Methods for Mixed Steady and Unsteady Multiscale Viscous Flows, Part II: Hypersonic Nonequilibrium Flows
Authors: Lani Andrea , Sjögreen Björn , Yee H. C. , Henshaw William D.
Published: July 2016

The variable high-order multiblock overlapping (overset) grids method of Sjögreen & Yee [CiCP, Vol. 5, 2009] for a perfect gas has been extended to nonequilibrium flows. This work makes use of the recently developed high-order well-balanced shock-capturing schemes and their filter counterparts [Wang et al., J. Comput. Phys., 2009, 2010] that exactly preserve certain non-trivial steady state solutions of the chemical nonequilibrium governing equations. Multiscale turbulence with strong shocks and flows containing both steady and unsteady components is best treated by mixing of numerical methods and switching on the appropriate scheme in the appropriate subdomains of the flow fields, even under the multiblock grid or adaptive grid refinement framework. While low dissipative sixth- or higher-order shock-capturing filter methods are appropriate for unsteady turbulence with shocklets, second- and third- order shock-capturing methods are more effective for strong steady or nearly steady shocks in terms of convergence. It is anticipated that our variable high-order overset grid framework capability with its highly modular design will allow for an optimum synthesis of these new algorithms in such a way that the most appropriate spatial discretizations can be tailored for each particular region of the flow. In this paper some of the latest developments in single block high-order filter schemes for chemical nonequilibrium flows are applied to overset grid geometries. The numerical approach is validated on a number of test cases characterized by hypersonic conditions with strong shocks, including the reentry flow surrounding a 3D Apollo-like NASA Crew Exploration Vehicle that might contain mixed steady and unsteady components, depending on the flow conditions.
An Unpreconditioned Boundary-Integral for Iterative Solution of Scattering Problems with Non-Constant Leontovitch Impedance Boundary Conditions
Authors: Levadoux D. , Millot F. , Pernet S.
Published: July 2016

This paper concerns the electromagnetic scattering by arbitrary shaped three dimensional imperfectly conducting objects modeled with non-constant Leontovitch impedance boundary condition. It has two objectives. Firstly, the intrinsically well-conditioned integral equation (noted GCSIE) proposed in [30] is described focusing on its discretization. Secondly, we highlight the potential of this method by comparison with two other methods, the first being a two currents formulation in which the impedance condition is implicitly imposed and whose the convergence is quasi-optimal for Lipschitz polyhedron, the second being a CFIE-like formulation [14]. In particular, we prove that the new approach is less costly in term of CPU time and gives a more accurate solution than that obtained from the CFIE formulation. Finally, as expected, It is demonstrated that no preconditioner is needed for this formulation.
Simulation of Propagating Acoustic Wavefronts with Random Sound Speed
Authors: Martinelli Sheri L.
Published: July 2016

A method for simulating acoustic wavefronts propagating under random sound speed conditions is presented. The approach applies a level set method to solve the Eikonal equation of high frequency acoustics for surfaces of constant phase, instead of tracing rays. The Lagrangian nature often makes full-field ray solutions difficult to reconstruct. The level set method captures multiple-valued solutions on a fixed grid. It is straightforward to represent other sources of uncertainty in the input data using this model, which has an advantage over Monte Carlo approaches in that it yields an expression for the solution as a function of random variables.
A Numerical Study on the Weak Galerkin Method for the Helmholtz Equation
Authors: Mu Lin , Wang Junping , Ye Xiu , Zhao Shan
Published: July 2016

A weak Galerkin (WG) method is introduced and numerically tested for the Helmholtz equation. This method is flexible by using discontinuous piecewise polynomials and retains the mass conservation property. At the same time, the WG finite element formulation is symmetric and parameter free. Several test scenarios are designed for a numerical investigation on the accuracy, convergence, and robustness of the WG method in both inhomogeneous and homogeneous media over convex and non-convex domains. Challenging problems with high wave numbers are also examined. Our numerical experiments indicate that the weak Galerkin is a finite element technique that is easy to implement, and provides very accurate and robust numerical solutions for the Helmholtz problem with high wave numbers.
Correlation Functions, Universal Ratios and Goldstone Mode Singularities inn-Vector Models
Authors: Kaupužs J. , Melnik R. V. N. , Rimšāns J.
Published: July 2016

Correlation functions in the(n) models below the critical temperature are considered. Based on Monte Carlo (MC) data, we confirm the fact stated earlier by Engels and Vogt, that the transverse two-plane correlation function of the(4) model for lattice sizes aboutL= 120 and small external fieldshis very well described by a Gaussian approximation. However, we show that fits of not lower quality are provided by certain non-Gaussian approximation. We have also tested larger lattice sizes, up toL= 512. The Fourier-transformed transverse and longitudinal two-point correlation functions have Goldstone mode singularities in the thermodynamic limit atk→ 0 andh= +0, i.e.,G⊥(k) ≃ak–λ⊥andG‖(k)≃bk–λ‖, respectively. Hereaandbare the amplitudes,k= |k| is the magnitude of the wave vectork. The exponents λᚆ, λ‖and the ratiobM2/a2, whereMis the spontaneous magnetization, are universal according to the GFD (grouping of Feynman diagrams) approach. Here we find that the universality follows also from the standard (Gaussian) theory, yieldingbM2/a2=(n−1)/16. Our MC estimates of this ratio are 0.06±0.01 forn=2, 0.17±0.01 forn= 4 and 0.498±0.010 forn= 10. According to these and our earlier MC results, the asymptotic behavior and Goldstone mode singularities are not exactly described by the standard theory. This is expected from the GFD theory. We have found appropriate analytic approximations forG⊥(k) andG‖(k), well fitting the simulation data for smallk. We have used them to test the Patashinski-Pokrovski relation and have found that it holds approximately.
Feature-Scale Simulations of Particulate Slurry Flows in Chemical Mechanical Polishing by Smoothed Particle Hydrodynamics
Authors: Wang Dong , Shao Sihong , Yan Changhao , Cai Wei , Zeng Xuan
Published: July 2016

In this paper, the mechanisms of material removal in chemical mechanical polishing (CMP) processes are investigated in detail by the smoothed particle hydrodynamics (SPH) method. The feature-scale behaviours of slurry flow, rough pad, wafer defects, moving solid boundaries, slurry-abrasive interactions, and abrasive collisions are modelled and simulated. Compared with previous work on CMP simulations, our simulations incorporate more realistic physical aspects of the CMP process, especially the effect of abrasive concentration in the slurry flows. The preliminary results on slurry flow in CMP provide microscopic insights on the experimental data of the relation between the removal rate and abrasive concentration and demonstrate that SPH is a suitable method for the research of CMP processes.
Numerical Solution for a Non-Fickian Diffusion in a Periodic Potential
Authors: Araújo Adérito , Das Amal K. , Neves Cidália , Sousa Ercília
Published: July 2016

Numerical solutions of a non-Fickian diffusion equation belonging to a hyperbolic type are presented in one space dimension. The Brownian particle modelled by this diffusion equation is subjected to a symmetric periodic potential whose spatial shape can be varied by a single parameter. We consider a numerical method which consists of applying Laplace transform in time; we then obtain an elliptic diffusion equation which is discretized using a finite difference method. We analyze some aspects of the convergence of the method. Numerical results for particle density, flux and mean-square-displacement (covering both inertial and diffusive regimes) are presented.
Strong Convergence and Speed up of Nested Stochastic Simulation Algorithm
Authors: Huang Can , Liu Di
Published: July 2016

In this paper, we revisit the Nested Stochastic Simulation Algorithm (NSSA) for stochastic chemical reacting networks by first proving its strong convergence. We then study a speed up of the algorithm by using the explicit Tau-Leaping method as the Inner solver to approximate invariant measures of fast processes, for which strong error estimates can also be obtained. Numerical experiments are presented to demonstrate the validity of our analysis.
An Adaptive, Finite Difference Solver for the Nonlinear Poisson-Boltzmann Equation with Applications to Biomolecular Computations
Authors: Mirzadeh Mohammad , Theillard Maxime , Helgadöttir Asdís , Boy David , Gibou Frédéric
Published: July 2016

We present a solver for the Poisson-Boltzmann equation and demonstrate its applicability for biomolecular electrostatics computation. The solver uses a level set framework to represent sharp, complex interfaces in a simple and robust manner. It also uses non-graded, adaptive octree grids which, in comparison to uniform grids, drastically decrease memory usage and runtime without sacrificing accuracy. The basic solver was introduced in earlier works [16,27], and here is extended to address biomolecular systems. First, a novel approach of calculating the solvent excluded and the solvent accessible surfaces is explained; this allows to accurately represent the location of the molecule’s surface. Next, a hybrid finite difference/finite volume approach is presented for discretizing the nonlinear Poisson-Boltzmann equation and enforcing the jump boundary conditions at the interface. Since the interface is implicitly represented by a level set function, imposing the jump boundary conditions is straightforward and efficient.
Simulation with Fluctuating and Singular Rates
Authors: Barekat Farzin , Caflisch Russel
Published: July 2016

In this paper we present a method to generate independent samples for a general random variable, either continuous or discrete. The algorithm is an extension of the Acceptance-Rejection method, and it is particularly useful for kinetic simulation in which the rates are fluctuating in time and have singular limits, as occurs for example in simulation of recombination interactions in a plasma. Although it depends on some additional requirements, the new method is easy to implement and rejects less samples than the Acceptance-Rejection method.
Flow shop scheduling decisions through Techniques for Order Preference by Similarity to an Ideal Solution (TOPSIS)
Authors: Gupta Arun , Kumar Shailendra
Published: July 2016

The flow-shop scheduling problem (FSP) has been widely studied in the literature and having a very active research area. Over the last few decades, a number of heuristic/meta-heuristic solution techniques have been developed. Some of these techniques offer excellent effectiveness and efficiency at the expense of substantial implementation efforts and being extremely complicated. This paper brings out the application of a Multi-Criteria Decision Making (MCDM) method known as techniques for order preference by similarity to an ideal solution (TOPSIS) using different weighting schemes in flow-shop environment. The objective function is identification of a job sequence which in turn would have minimum makespan (total job completion time). The application of the proposed method to flow shop scheduling is presented and explained with a numerical example. The results of the proposed TOPSIS based technique of FSP are also compared on the basis of some benchmark problems and found compatible with the results obtained from other standard procedures.
La formación lectora y literaria (2015) o cómo reflexionar sobre L’horrible perill de la lectura (2015): diálogos en torno a la obra y el pensamiento del profesor Josep Ballester
Authors: Romero Oliva Manuel Francisco , Wilczyńska Agnieszka
Published: July 2016

Reseña bibliográfica de dos libros de este autor: 

Ballester, J. (2015). La formación lectora y literaria. Barcelona. Graó.

Ballester, J. (2015). L’horrible perill de la lectura. Valencia. Perifèric edicions.
El bilingüismo y la identidad: estudio de caso sobre la relación entre las lenguas y las emociones
Authors: Pérez-Luzardo Díaz Jessica , Schmidt Andjelina
Published: July 2016

En el presente estudio se analiza la relación que existe entre la lengua, la cultura y las emociones en el caso de los bilingües biculturales. Para probar la validez de la hipótesis de que los bilingües biculturales sienten de forma diferente en sus respectivas lenguas se realiza un estudio piloto. Los resultados apuntan a que las imágenes mentales para un mismo significante difieren según la lengua en la que se evoca.
Branchiura sowerbyi Reared in Two Sediments for Ecotoxicological Bioassays
Authors: Lobo Haroldo Santos , Espíndola Evaldo Luiz Gaeta
Published: July 2016

The present work compared the survival, growth, and reproduction of Branchiura sowerbyi reared in natural sediment and in artificial tropical sediment (composed of sand, clay, and coconut fibers). The artificial tropical sediment, in the tested composition, appeared not to be suitable for conducting bioassays with this species, since the results showed a high mortality of the juveniles and low reproduction of adults as compared to those observed for the natural sediment.
Variation of CCN activity during new particle formation events in the North
China Plain
Authors: Ma Nan , Zhao Chunsheng , Tao Jiangchuan , Wu Zhijun , Kecorius Simonas , Wang Zhibin , Größ Johannes , Liu Hongjian , Bian Yuxuan , Kuang Ye , Teich Monique , Spindler Gerald , Müller Konrad , van Pinxteren Dominik , Herrmann Hartmut , Hu Min , Wiedensohler Alfred
Published: July 2016

Abstract. The aim of this investigation was to obtain a better understanding of the variability of the cloud condensation nuclei (CCN) activity during new particle formation (NPF) events in an anthropogenically polluted atmosphere of the North China Plain (NCP). We investigated the size-resolved activation ratio as well as particle number size distribution, hygroscopicity, and volatility during a 4-week intensive field experiment in summertime at a regional atmospheric observatory in Xianghe. Interestingly, based on a case study, two types of NPF events were found, in which the newly formed particles exhibited either a higher or a lower hygroscopicity. Therefore, the CCN activity of newly formed particles in different NPF events was largely different, indicating that a simple parameterization of particle CCN activity during NPF events over the NCP might lead to poor estimates of CCN number concentration (NCCN). For a more accurate estimation of the potential NCCN during NPF events, the variation of CCN activity has to be taken into account. Considering that a fixed activation ratio curve or critical diameter are usually used to calculate NCCN, the influence of the variation of particle CCN activity on the calculation of NCCN during NPF events was evaluated based on the two parameterizations. It was found that NCCN might be underestimated by up to 30 % if a single activation ratio curve (representative of the region and season) were to be used in the calculation; and might be underestimated by up to 50 % if a fixed critical diameter (representative of the region and season) were used. Therefore, we suggest not using a fixed critical diameter in the prediction of NCCN in NPF. If real-time CCN activity data are not available, using a proper fixed activation ratio curve can be an alternative but compromised choice.
Transfer of diazotroph-derived nitrogen towards non-diazotrophic
planktonic communities: a comparative study between
Trichodesmium erythraeum, Crocosphaera
watsonii and Cyanothece sp.
Authors: Berthelot Hugo , Bonnet Sophie , Grosso Olivier , Cornet Véronique , Barani Aude
Published: July 2016

Abstract. Biological dinitrogen (N2) fixation is the major source of new nitrogen (N) for the open ocean, and thus promotes marine productivity, in particular in the vast N-depleted regions of the surface ocean. Yet, the fate of the diazotroph-derived N (DDN) in marine ecosystems is poorly understood, and its transfer to auto- and heterotrophic surrounding plankton communities is rarely measured due to technical limitations. Moreover, the different diazotrophs involved in N2 fixation (Trichodesmium spp. vs. UCYN) exhibit distinct patterns of N2 fixation and inhabit different ecological niches, thus having potentially different fates in the marine food webs that remain to be explored. Here we used nanometer scale secondary ion mass spectrometry (nanoSIMS) coupled with 15N2 isotopic labelling and flow cytometry cell sorting to examine the DDN transfer to specific groups of natural phytoplankton and bacteria during artificially induced diazotroph blooms in New Caledonia (southwestern Pacific). The fate of the DDN was compared according to the three diazotrophs: the filamentous and colony-forming Trichodesmium erythraeum (IMS101), and the unicellular strains Crocosphaera watsonii WH8501 and Cyanothece ATCC51142. After 48 h, 7–17 % of the N2 fixed during the experiment was transferred to the dissolved pool and 6–12 % was transferred to non-diazotrophic plankton. The transfer was twice as high in the T. erythraeum bloom than in the C. watsonii and Cyanothece blooms, which shows that filamentous diazotrophs blooms are more efficient at promoting non-diazotrophic production in N-depleted areas. The amount of DDN released in the dissolved pool did not appear to be a good indicator of the DDN transfer efficiency towards the non-diazotrophic plankton. In contrast, the 15N-enrichment of the extracellular ammonium (NH4+) pool was a good indicator of the DDN transfer efficiency: it was significantly higher in the T. erythraeum than in unicellular diazotroph blooms, leading to a DDN transfer twice as efficient. This suggests that NH4+ was the main pathway of the DDN transfer from diazotrophs to non-diazotrophs. The three simulated diazotroph blooms led to significant increases in non-diazotrophic plankton biomass. This increase in biomass was first associated with heterotrophic bacteria followed by phytoplankton, indicating that heterotrophs took the most advantage of the DDN in this oligotrophic ecosystem.
The PRISM4 (mid-Piacenzian) paleoenvironmental reconstruction
Authors: Dowsett Harry , Dolan Aisling , Rowley David , Moucha Robert , Forte Alessandro M. , Mitrovica Jerry X. , Pound Matthew , Salzmann Ulrich , Robinson Marci , Chandler Mark , Foley Kevin , Haywood Alan
Published: July 2016

Abstract. The mid-Piacenzian is known as a period of relative warmth when compared to the present day. A comprehensive understanding of conditions during the Piacenzian serves as both a conceptual model and a source for boundary conditions as well as means of verification of global climate model experiments. In this paper we present the PRISM4 reconstruction, a paleoenvironmental reconstruction of the mid-Piacenzian ( ∼  3 Ma) containing data for paleogeography, land and sea ice, sea-surface temperature, vegetation, soils, and lakes. Our retrodicted paleogeography takes into account glacial isostatic adjustments and changes in dynamic topography. Soils and lakes, both significant as land surface features, are introduced to the PRISM reconstruction for the first time. Sea-surface temperature and vegetation reconstructions are unchanged but now have confidence assessments. The PRISM4 reconstruction is being used as boundary condition data for the Pliocene Model Intercomparison Project Phase 2 (PlioMIP2) experiments.
Atmospheric methane control mechanisms during the early Holocene
Authors: Yang Ji-Woong , Ahn Jinho , Brook Edward J. , Ryu Yeongjun
Published: July 2016

Abstract. Understanding the atmospheric methane (CH4) change is crucial to predict and mitigate the future climate change. In spite of recent studies using various approaches for the last ~ 1000 to 2000 years, control mechanisms of CH4 still remain unclear, partly because the late Holocene CH4 budget is comprised of natural and anthropogenic emissions. In contrast, the early Holocene was a period when human influence should have been substantially smaller, so that it allows us to elucidate the natural controls under interglacial conditions. Here we present new high resolution CH4 records of millennial scale CH4 variability from Siple Dome, Antarctica, covering from 11.6 to 7.7 thousands of years before 1950 AD (ka). We observe several local CH4 minima on a roughly 1000-year spacing. Each CH4 minimum corresponds to cool periods in Greenland. We hypothesize that the cooling in Greenland forced the Intertropical Convergence Zone (ITCZ) to migrate southward, reducing rainfall in northern tropical wetlands although there is no obvious change was observed in low latitude hydrology corresponding to abrupt CH4 reduction at ~ 10.3 ka. A high resolution inter-polar difference (IPD) during the early Holocene increased from ~ 10.7 to 9.9 ka, and remained high until ~ 9.3 ka. With a simple three-box model results, our new IPD records suggest that the ratio of northern high latitude to tropical sources increased due to a boreal source expansion following the deglaciation.
Comment on "Scaling regimes and linear/nonlinear responses of last millennium
climate to volcanic and solar forcing" by S. Lovejoy and C. Varotsos (2016)
Authors: Rypdal Kristoffer , Rypdal Martin
Published: July 2016

Abstract. Lovejoy and Varotsos (2016) (L&V) analyse the temperature response to solar, volcanic, and solar plus volcanic forcing in the Zebiak–Cane (ZC) model, and to solar and solar plus volcanic forcing in the Goddard Institute for Space Studies (GISS) E2-R model. By using a simple wavelet filtering technique they conclude that the responses in the ZC model combine subadditively on timescales from 50 to 1000 years. Nonlinear response on shorter timescales is claimed by analysis of intermittencies in the forcing and the temperature signal for both models. The analysis of additivity in the ZC model suffers from a confusing presentation of results based on an invalid approximation, and from ignoring the effect of internal variability. We present tests without this approximation which are not able to detect nonlinearity in the response, even without accounting for internal variability. We also demonstrate that internal variability will appear as subadditivity if it is not accounted for. L&V's analysis of intermittencies is based on a mathematical result stating that the intermittencies of forcing and response are the same if the response is linear. We argue that there are at least three different factors that may invalidate the application of this result for these data. It is valid only for a power-law response function; it assumes power-law scaling of structure functions of forcing as well as temperature signal; and the internal variability, which is strong at least on the short timescales, will exert an influence on temperature intermittence which is independent of the forcing. We demonstrate by a synthetic example that the differences in intermittencies observed by L&V easily can be accounted for by these effects under the assumption of a linear response. Our conclusion is that the analysis performed by L&V does not present valid evidence for a detectable nonlinear response in the global temperature in these climate models.
Ultrafast imaging Raman spectroscopy of large-area samples without stepwise
scanning
Authors: Schmälzlin Elmar , Moralejo Benito , Bodenmüller Daniel , Darvin Maxim E. , Thiede Gisela , Roth Martin M.
Published: July 2016

Abstract. Step-by-step, time-consuming scanning of the sample is still the state-of-the-art in imaging Raman spectroscopy. Even for a few 100 image points the measurement time may add up to minutes or hours. A radical decrease in measurement time can be achieved by applying multiplex spectrographs coupled to imaging fiber bundles that are successfully used in astronomy. For optimal use of the scarce and expensive observation time at astronomical observatories, special high-performance spectrograph systems were developed. They are designed for recording thousands of spatially resolved spectra of a two-dimensional image field within one single exposure. Transferring this technology to imaging Raman spectroscopy allows a considerably faster acquisition of chemical maps. Currently, an imaging field of up to 1 cm2 can be investigated. For porcine skin the required measurement time is less than 1 min. For this reason, this technique is of particular interest for medical diagnostics, e.g., the identification of potentially cancerous abnormalities of skin tissue.
4-D imaging of sub-second dynamics in pore-scale processes using real-time synchrotron X-ray tomography
Authors: Dobson Katherine J. , Coban Sophia B. , McDonald Samuel A. , Walsh Joanna N. , Atwood Robert C. , Withers Philip J.
Published: July 2016

Abstract. A variable volume flow cell has been integrated with state-of-the-art ultra-high-speed synchrotron X-ray tomography imaging. The combination allows the first real-time (sub-second) capture of dynamic pore (micron)-scale fluid transport processes in 4-D (3-D + time). With 3-D data volumes acquired at up to 20 Hz, we perform in situ experiments that capture high-frequency pore-scale dynamics in 5–25 mm diameter samples with voxel (3-D equivalent of a pixel) resolutions of 2.5 to 3.8 µm. The data are free from motion artefacts and can be spatially registered or collected in the same orientation, making them suitable for detailed quantitative analysis of the dynamic fluid distribution pathways and processes. The methods presented here are capable of capturing a wide range of high-frequency nonequilibrium pore-scale processes including wetting, dilution, mixing, and reaction phenomena, without sacrificing significant spatial resolution. As well as fast streaming (continuous acquisition) at 20 Hz, they also allow larger-scale and longer-term experimental runs to be sampled intermittently at lower frequency (time-lapse imaging), benefiting from fast image acquisition rates to prevent motion blur in highly dynamic systems. This marks a major technical breakthrough for quantification of high-frequency pore-scale processes: processes that are critical for developing and validating more accurate multiscale flow models through spatially and temporally heterogeneous pore networks.
Optical Coherence Tomography Angiography in Retinal Vein Occlusion Treated with Dexamethasone Implant: A New Test for Follow-Up Evaluation
Authors: Glacet-Bernard Agnes , Sellam Alexandre , Coscas Florence , Coscas Gabriel , Souied Eric H.
Published: July 2016

Purpose

To quantitatively and qualitatively analyze patients with macular edema secondary to retinal vein occlusion (RVO) and treated with the intravitreal dexamethasone implant using optical coherence tomography angiography (OCTA).

Methods

The files of patients treated with intravitreal injection of dexamethasone implant for macular edema secondary to RVO were retrospectively analyzed. Before and after injection, the following data were recorded: best-corrected visual acuity (BCVA), central macular thickness (CMT) measured using spectral-domain optical coherence tomography, fluorescein angiography, and OCTA (Optovue, Inc., Fremont, CA, USA). Results of automatic measurement of vascular density of the superficial capillary plexus (SCP) and deep capillary plexus were obtained before and after treatment and compared to those of healthy subjects matched for age and sex.

Results

Seven eyes of 7 patients (mean age, 76 years; 57% male) were analyzed, including 3 cases of central RVO and 4 cases of branch RVO. All patients received 1 intravitreal injection of dexamethasone implant. After a mean follow-up of 2 months, CMT significantly decreased from 657 µm to 324 µm on average and BCVA increased from 20/100 to 20/50 (p = 0.017 and p<0.001, respectively). At the SCP, the mean whole en face vascular density slightly decreased during follow-up from 43.21% to 42.76% (not statistically significant). Vascular densities were largely inferior to those observed in control subjects (p≤0.01 in all quadrants).

Conclusions

This study confirms the potential contribution of OCTA as a novel noninvasive imaging technology that enables a quantitative and qualitative evaluation of the follow-up of macular edema in RVO. Optical coherence tomography angiography may complement advantageously multimodal imaging to monitor patients with RVO.
Regression of Epiretinal Membrane after Optic Nerve Atrophy
Authors: Wetzel Barbara , Mylonas Georgios , Prager Franz , Kahraman Guenal , Bernhart Clemens , Lux Robert , Amon Michael
Published: July 2016

Purpose

To describe a case of epiretinal membrane (ERM) regression after optic nerve atrophy.

Methods

Retrospective case report.

Results

A 56-year-old man with progressive visual impairment was found to have an ERM with associated retinal thickening and distortion (documented with spectral-domain optical coherence tomography [OCT]). In addition, we noted a slight unilateral paleness of the optic nerve. The patient denied any further diagnostic investigation and presented himself again 2 years after the initial presentation. A new OCT examination at this point revealed a remarkable regression of the ERM and atrophy of the retinal nerve fiber layer.

Conclusions

Regression of ERM may occur after optic nerve atrophy. A potential causal linkage is suggested based on the atrophy of the retinal nerve fibers and regression of the glial cells.
Understanding the Pelvic Pain Mechanism is Key to Find an Adequate Therapeutic Approach
Authors: Van Kerrebroeck Philip
Published: July 2016

Pain is a natural mechanism to actual or potential tissue damage and involves both a sensory and an emotional experience. In chronic pelvic pain, localisation of pain can be widespread and can cause considerable distress. A multidisciplinary approach is needed in order to fully understand the pelvic pain mechanism and to identify an adequate therapeutic approach.
Fighting Urinary Tract Infections with Antibiotic and Non-Antibiotic Therapies
Authors: Peri Lluis
Published: July 2016

Urinary tract infections (UTIs) place a considerable burden on the patient and are associated with substantial economic cost. Treatment of UTIs is mainly achieved using antibiotics, however, the rise in antibiotic resistance is concerning and the use of non-antimicrobial prophylaxis offers alternative treatment methods.