Discrete CMC surfaces in R^3 and discrete minimal surfaces in S^3. A discrete Lawson correspondence

The main result of this paper is a discrete Lawson correspondence between discrete CMC surfaces in R^3 and discrete minimal surfaces in S^3. This is a correspondence between two discrete isothermic surfaces. We show that this correspondence is an isometry in the following sense: it preserves the metric coefficients introduced previously by Bobenko and Suris for isothermic nets. Exactly as in the smooth case, this is a correspondence between nets with the same Lax matrices, and the immersion formulas also coincide with the smooth case.Comment: 13 page

Learning parametric dictionaries for graph signals

In sparse signal representation, the choice of a dictionary often involves a tradeoff between two desirable properties -- the ability to adapt to specific signal data and a fast implementation of the dictionary. To sparsely represent signals residing on weighted graphs, an additional design challenge is to incorporate the intrinsic geometric structure of the irregular data domain into the atoms of the dictionary. In this work, we propose a parametric dictionary learning algorithm to design data-adapted, structured dictionaries that sparsely represent graph signals. In particular, we model graph signals as combinations of overlapping local patterns. We impose the constraint that each dictionary is a concatenation of subdictionaries, with each subdictionary being a polynomial of the graph Laplacian matrix, representing a single pattern translated to different areas of the graph. The learning algorithm adapts the patterns to a training set of graph signals. Experimental results on both synthetic and real datasets demonstrate that the dictionaries learned by the proposed algorithm are competitive with and often better than unstructured dictionaries learned by state-of-the-art numerical learning algorithms in terms of sparse approximation of graph signals. In contrast to the unstructured dictionaries, however, the dictionaries learned by the proposed algorithm feature localized atoms and can be implemented in a computationally efficient manner in signal processing tasks such as compression, denoising, and classification

Chebyshev Polynomial Approximation for Distributed Signal Processing

Unions of graph Fourier multipliers are an important class of linear operators for processing signals defined on graphs. We present a novel method to efficiently distribute the application of these operators to the high-dimensional signals collected by sensor networks. The proposed method features approximations of the graph Fourier multipliers by shifted Chebyshev polynomials, whose recurrence relations make them readily amenable to distributed computation. We demonstrate how the proposed method can be used in a distributed denoising task, and show that the communication requirements of the method scale gracefully with the size of the network.Comment: 8 pages, 5 figures, to appear in the Proceedings of the IEEE International Conference on Distributed Computing in Sensor Systems (DCOSS), June, 2011, Barcelona, Spai

A non-parametric method for measuring the local dark matter density

We present a new method for determining the local dark matter density using kinematic data for a population of tracer stars. The Jeans equation in the $z$-direction is integrated to yield an equation that gives the velocity dispersion as a function of the total mass density, tracer density, and the tilt term that describes the coupling of vertical and radial motions. We then fit a dark matter mass profile to tracer density and velocity dispersion data to derive credible regions on the vertical dark matter density profile. Our method avoids numerical differentiation, leading to lower numerical noise, and is able to deal with the tilt term while remaining one dimensional. In this study we present the method and perform initial tests on idealised mock data. We also demonstrate the importance of dealing with the tilt term for tracers that sample $\gtrsim 1$ kpc above the disc plane. If ignored, this results in a systematic underestimation of the dark matter density.Comment: V2: Improved tracer density description; increased number of mocks to explore outliers; corrected sign error in the (R, z) velocity dispersion; main conclusions unchanged. 19 pages, 14 figure

Self-pulsation dynamics in narrow stripe semiconductor lasers

In this paper, we address the physical origin of self-pulsation in narrow stripe edge emitting semiconductor lasers. We present both experimental time-averaged polarization-resolved near-field measurements performed with a charged-coupled device camera and picosecond time resolved near-field measurements performed with a streak camera. These results demonstrate dynamic spatial-hole burning during pulse formation and evolution. We conclude from these experimental results that the dominant process which drives the self-pulsation in this type of laser diode is carrier induced effective refractive index change induced by the spatial-hole burning

The Local Dark Matter Density from SDSS-SEGUE G-dwarfs

We derive the local dark matter density by applying the integrated Jeans equation method from Silverwood et al. (2016) to SDSS-SEGUE G-dwarf data processed and presented by B\"udenbender et al. (2015). We use the MultiNest Bayesian nested sampling software to fit a model for the baryon distribution, dark matter and tracer stars, including a model for the 'tilt term' that couples the vertical and radial motions, to the data. The $\alpha$-young population from B\"udenbender et al. (2015) yields the most reliable result of $\rho_{\rm DM} = 0.46^{+0.07}_{-0.09}\, {{\rm GeV\, cm}^{-3}} = 0.012^{+0.001}_{-0.002}\, {{\rm M}_\odot \, {\rm pc}^{-3}}$. Our analyses yield inconsistent results for the $\alpha$-young and $\alpha$-old data, pointing to problems in the tilt term and its modelling, the data itself, the assumption of a flat rotation curve, or the effects of disequilibria.Comment: 17 pages, 10 figures, submitted to MNRA

Fatty acid bioconversion in harpacticoid copepods in a changing environment : a transcriptomic approach

By 2100, global warming is predicted to significantly reduce the capacity of marine primary producers for long-chain polyunsaturated fatty acid (LC-PUFA) synthesis. Primary consumers such as harpacticoid copepods (Crustacea) might mitigate the resulting adverse effects on the food web by increased LC-PUFA bioconversion. Here, we present a high-quality de novo transcriptome assembly of the copepodPlatychelipus littoralis, exposed to changes in both temperature (+3 degrees C) and dietary LC-PUFA availability. Using this transcriptome, we detected multiple transcripts putatively coding for LC-PUFA-bioconverting front-end fatty acid (FA) desaturases and elongases, and performed phylogenetic analyses to identify their relationship with sequences of other (crustacean) taxa. While temperature affected the absolute FA concentrations in copepods, LC-PUFA levels remained unaltered even when copepods were fed an LC-PUFA-deficient diet. While this suggests plasticity of LC-PUFA bioconversion withinP. littoralis, none of the putative front-end desaturase or elongase transcripts was differentially expressed under the applied treatments. Nevertheless, the transcriptome presented here provides a sound basis for future ecophysiological research on harpacticoid copepods. This article is part of the theme issue 'The next horizons for lipids as 'trophic biomarkers': evidence and significance of consumer modification of dietary fatty acids'

A study of corrosion and chromium diffusion for power station boiler tube materials

The aim of this study is to determine the influence alloy diffusion processes have on corrosion. [Continues.

FINANCIAL TECHNOLOGY AND LIQUIDITY IN THE NIGERIAN BANKING SECTOR

In recent times, financial technology advancement has been growing in volume of transactions. The increasingly used payment system has prompted concern on the long run impact of electronic payment on liquidity of the Nigerian banking sector. The study investigated impact of financial technology on the liquidity of the Nigerian banking sector. A case study research design was used to determine relationship existing between electronic payment services and banking sector liquidity in Nigeria. The study covered nine years period, using quarterly data spanning from the first quarter of 2009 to the fourth quarter of 2017. Secondary data was also collected in order to estimate the model. The dependent variable was proxied by loan to deposit ratio while the independent variables was proxied by automated teller machine, point of sales, mobile payment and automated clearing system-cheque. A unit root test was employed as a pre-estimation technique for this study, hence the variables where stationary at first difference. The study employed the Auto Regressive Distributed Lag or Bounds test approach in order to establish the short run dynamics and long run relationship of the model. Findings from the study suggested that there was a notable impact of electronic payment (fin-tech) on liquidity among all Deposit Money banks in Nigeria. Due to this finding the study concluded that an e-system in the banking sector will bring about financial development. Deposit Money banks should be encouraged to adopt electronic payment systems so as to have a better banking experience, easy access to banking products, reduced cost and flexibility of online international transactions

Transport properties of a molecule embedded in an Aharonov-Bohm interferometer

We theoretically investigate the transport properties of a molecule embedded in one arm of a mesoscopic Aharonov-Bohm interferometer. Due to the presence of phonons the molecule level position ($\epsilon_d$) and the electron-electron interaction ($U$) undergo a \emph{polaronic shift} which affects dramatically the electronic transport through the molecular junction. When the electron-phonon interaction is weak the linear conductance presents Fano-line shapes as long as the direct channel between the electrodes is opened. The observed Fano resonances in the linear conductance are originated from the interference between the spin Kondo state and the direct path. For strong enough electron-phonon interaction, the electron-electron interaction is renormalized towards negative values, {\it i.e.} becomes effectively attractive. This scenario favors fluctuations between the empty and doubly occupied charge states and therefore promotes a charge Kondo effect. However, the direct path between the contacts breaks the electron-hole symmetry which can efficiently suppress this charge Kondo effect. Nevertheless, we show that a proper tuning of the gate voltage is able to revive the Kondo resonance. Our results are obtained by using the Numerical Renormalization approximation to compute the electronic spectral function and the linear conductance.Comment: 17 pages, 12 figure