Modelling solute transport in soil columns using advective-dispersive equations with fractional spatial derivatives

Solute transport in soils is commonly simulated with the advective–dispersive equation, or ADE. It has been reported that this model cannot take into account several important features of solute movement through soil. Recently, a new model has been suggested that results in a solute transport equation with fractional spatial derivatives, or FADE. We have assembled a database on published solute transport experiments in soil columns to test the new model. The FADE appears to be a useful generalization of the ADE. The order of the fractional differentiation reflects differences in physical conditions of the solute transport in soi

Enhancing declarative debugging with loop expansion and tree compression

This work has been partially supported by the Spanish Ministerio de Econom´ıa y Competitividad (Secretar´ıa de Estado de Investigaci´on, Desarrollo e Innovaci´on) under grant TIN2008-06622-C03-02 and by the Generalitat Valenciana under grant PROMETEO/2011/052. David Insa was partially supported by the Spanish Ministerio de Eduaci´on under FPU grant AP2010-4415Insa Cabrera, D.; Silva Galiana, JF.; Tomás Franco, C. (2013). Enhancing declarative debugging with loop expansion and tree compression. En Logic-Based Program Synthesis and Transformation. Springer Verlag (Germany). 71-88. https://doi.org/10.1007/978-3-642-38197-3_6S7188Binks, D.: Declarative Debugging in Gödel. PhD thesis, University of Bristol (1995)Calejo, M.: A Framework for Declarative Prolog Debugging. PhD thesis, New University of Lisbon (1992)Davie, T., Chitil, O.: Hat-delta: One Right Does Make a Wrong. In: Butterfield, A. (ed.) Draft Proceedings of the 17th International Workshop on Implementation and Application of Functional Languages, IFL 2005, p. 11. Tech. Report No: TCD-CS-2005-60, University of Dublin, Ireland (September 2005)Davie, T., Chitil, O.: Hat-delta: One Right Does Make a Wrong. In: Seventh Symposium on Trends in Functional Programming, TFP 2006 (April 2006)Harrison, P.G., Khoshnevisan, H.: A new approach to recursion removal. Theor. Comput. Sci. 93(1), 91–113 (1992)Hirunkitti, V., Hogger, C.J.: A Generalised Query Minimisation for Program Debugging. In: Adsul, B. (ed.) AADEBUG 1993. LNCS, vol. 749, pp. 153–170. Springer, Heidelberg (1993)Insa, D., Silva, J.: An Algorithmic Debugger for Java. In: Proc. of the 26th IEEE International Conference on Software Maintenance, pp. 1–6 (2010)Insa, D., Silva, J.: Debugging with Incomplete and Dynamically Generated Execution Trees. In: Proc. of the 20th International Symposium on Logic-based Program Synthesis and Transformation, LOPSTR 2010, Austria (2010)Insa, D., Silva, J.: A Transformation of Iterative Loops into Recursive Loops. Technical Report DSIC/05/12, Universidad Politécnica de Valencia (2012), http://www.dsic.upv.es/~jsilva/research.htm#techsInsa, D., Silva, J., Tomás, C.: Enhancing Declarative Debugging with Loop Expansion and Tree Compression. Technical Report DSIC/11/12, Universidad Politécnica de Valencia (2012), http://www.dsic.upv.es/~jsilva/research.htm#techsLiu, Y.A., Stoller, S.D.: From recursion to iteration: what are the optimizations? In: Proceedings of the 2000 ACM SIGPLAN Workshop on Partial Evaluation and Semantics-Based Program Manipulation, PEPM 2000, pp. 73–82. ACM, New York (2000)Lloyd, J.W.: Declarative error diagnosis. New Gen. Comput. 5(2), 133–154 (1987)Nilsson, H.: Declarative Debugging for Lazy Functional Languages. PhD thesis, Linköping, Sweden (May 1998)NIST: The Economic Impacts of Inadequate Infrastructure for Software Testing. USA National Institute of Standards and Technology, NIST Planning Report 02-3 (May 2002)Riesco, A., Verdejo, A., Martí-Oliet, N., Caballero, R.: Declarative Debugging of Rewriting Logic Specifications. Journal of Logic and Algebraic Programming (September 2011)Shapiro, E.Y.: Algorithmic Program Debugging. MIT Press (1982)Silva, J.: A Survey on Algorithmic Debugging Strategies. Advances in Engineering Software 42(11), 976–991 (2011)Yi, Q., Adve, V., Kennedy, K.: Transforming loops to recursion for multi-level memory hierarchies. In: Proceedings of the SIGPLAN 2000 Conference on Programming Language Design and Implementation, pp. 169–181 (2000

Enhancement of near-cloaking. Part II: the Helmholtz equation

The aim of this paper is to extend the method of improving cloaking structures in the conductivity to scattering problems. We construct very effective near-cloaking structures for the scattering problem at a fixed frequency. These new structures are, before using the transformation optics, layered structures and are designed so that their first scattering coefficients vanish. Inside the cloaking region, any target has near-zero scattering cross section for a band of frequencies. We analytically show that our new construction significantly enhances the cloaking effect for the Helmholtz equation.Comment: 16pages, 12 fugure

Generating Neutrino Mass in the 331 Model

A mechanism for generating small tree-level Majorana mass for neutrinos is implemented in the 331 Model. No additional fermions or scalars need to be added, and no mass scale greater than a few TeV is invoked.Comment: LaTex, 7 pages, no figures. Revised version to appear in Phys. Rev.

Spin dynamics in high-mobility two-dimensional electron systems

Understanding the spin dynamics in semiconductor heterostructures is highly important for future semiconductor spintronic devices. In high-mobility two-dimensional electron systems (2DES), the spin lifetime strongly depends on the initial degree of spin polarization due to the electron-electron interaction. The Hartree-Fock (HF) term of the Coulomb interaction acts like an effective out-of-plane magnetic field and thus reduces the spin-flip rate. By time-resolved Faraday rotation (TRFR) techniques, we demonstrate that the spin lifetime is increased by an order of magnitude as the initial spin polarization degree is raised from the low-polarization limit to several percent. We perform control experiments to decouple the excitation density in the sample from the spin polarization degree and investigate the interplay of the internal HF field and an external perpendicular magnetic field. The lifetime of spins oriented in the plane of a [001]-grown 2DES is strongly anisotropic if the Rashba and Dresselhaus spin-orbit fields are of the same order of magnitude. This anisotropy, which stems from the interference of the Rashba and the Dresselhaus spin-orbit fields, is highly density-dependent: as the electron density is increased, the kubic Dresselhaus term becomes dominant and reduces the anisotropy.Comment: 13 pages, 6 figure

Spin-dephasing anisotropy for electrons in a diffusive quasi-1D GaAs wire

We present a numerical study of dephasing of electron spin ensembles in a diffusive quasi-one-dimensional GaAs wire due to the D'yakonov-Perel' spin-dephasing mechanism. For widths of the wire below the spin precession length and for equal strength of Rashba and linear Dresselhaus spin-orbit fields a strong suppression of spin-dephasing is found. This suppression of spin-dephasing shows a strong dependence on the wire orientation with respect to the crystal lattice. The relevance for realistic cases is evaluated by studying how this effect degrades for deviating strength of Rashba and linear Dresselhaus fields, and with the inclusion of the cubic Dresselhaus term

Spin-filtering and charge- and spin-switching effects in a quantum wire with periodically attached stubs

Spin-dependent electron transport in a periodically stubbed quantum wire in the presence of Rashba spin-orbit interaction (SOI) is studied via the nonequilibrium Green's function method combined with the Landauer-Buttiker formalism. The coexistence of spin filtering, charge and spin switching are found in the considered system. The mechanism of these transport properties is revealed by analyzing the total charge density and spin-polarized density distributions in the stubbed quantum wire. Furthermore, periodic spin-density islands with high polarization are also found inside the stubs, owing to the interaction between the charge density islands and the Rashba SOI-induced effective magnetic field. The proposed nanostructure may be utilized to devise an all-electrical multifunctional spintronic device.Comment: 4 pages, 4 figure

Density-functional embedding using a plane-wave basis

The constrained electron density method of embedding a Kohn-Sham system in a substrate system (first described by P. Cortona, Phys. Rev. B {\bf 44}, 8454 (1991) and T.A. Wesolowski and A. Warshel, J. Phys. Chem {\bf 97}, 8050 (1993)) is applied with a plane-wave basis and both local and non-local pseudopotentials. This method divides the electron density of the system into substrate and embedded electron densities, the sum of which is the electron density of the system of interest. Coupling between the substrate and embedded systems is achieved via approximate kinetic energy functionals. Bulk aluminium is examined as a test case for which there is a strong interaction between the substrate and embedded systems. A number of approximations to the kinetic-energy functional, both semi-local and non-local, are investigated. It is found that Kohn-Sham results can be well reproduced using a non-local kinetic energy functional, with the total energy accurate to better than 0.1 eV per atom and good agreement between the electron densities.Comment: 11 pages, 4 figure

Light-cone QCD Sum Rules for the Λ\Lambda Baryon Electromagnetic Form Factors and its magnetic moment

We present the light-cone QCD sum rules up to twist 6 for the electromagnetic form factors of the $\Lambda$ baryon. To estimate the magnetic moment of the baryon, the magnetic form factor is fitted by the dipole formula. The numerical value of our estimation is $\mu_\Lambda=-(0.64\pm0.04)\mu_N$, which is in accordance with the experimental data and the existing theoretical results. We find that it is twist 4 but not the leading twist distribution amplitudes that dominate the results.Comment: 13 page, 7 figures, accepted for publication in Euro. Phys. J.

Hepatic scavenger receptor class B type 1 knockdown reduces atherosclerosis and enhances the antiatherosclerotic effect of brown fat activation in APOE*3-Leiden.CETP mice

Objective:Brown fat activation attenuates atherosclerosis development by accelerating triglyceride-rich lipoprotein turnover and/or stimulation of reverse cholesterol transport via the SRB1 (scavenger receptor class B type 1). The aim of this study was to investigate the specific role of hepatic SRB1 in the atheroprotective properties of brown fat activation.Approach and Results:APOE*3-Leiden.CETP mice, a well-established model of human-like lipoprotein metabolism and atherosclerosis, were treated with vehicle or adenoassociated virus serotype 8-short hairpin RNA, which decreased hepatic SRB1 protein levels by 40% to 55%. After 2 weeks, mice without or with hepatic SRB1 knockdown were treated with vehicle or the beta 3-adrenergic receptor agonist CL316 243 to activate brown fat for 4 weeks to determine HDL (high-density lipoprotein) catabolism and for 9 weeks to evaluate atherosclerosis. Surprisingly, hepatic SRB1 knockdown additively improved the beneficial effects of beta 3-adrenergic receptor agonism on atherosclerosis development. In fact, hepatic SRB1 knockdown per se not only increased HDL-cholesterol levels but also reduced plasma triglyceride and non-HDL-cholesterol levels, thus explaining the reduction in atherosclerosis development. Mechanistic studies indicated that this is due to increased lipolytic processing and hepatic uptake of VLDL (very low density lipoprotein) by facilitating VLDL-surface transfer to HDL.Conclusions:Hepatic SRB1 knockdown in a mouse model with an intact ApoE (apolipoprotein E)-LDLR (low density lipoprotein receptor) clearance pathway, relevant to human lipoprotein metabolism, reduced atherosclerosis and improved the beneficial effect of brown fat activation on atherosclerosis development, explained by pleiotropic effects of hepatic SRB1 knockdown on lipolytic processing and hepatic uptake of VLDL. Brown fat activation could thus be an effective strategy to treat cardiovascular disease also in subjects with impaired SRB1 function.Functional Genomics of Systemic Disorder