Characteristics of Conservation Laws for Difference Equations

Each conservation law of a given partial differential equation is determined (up to equivalence) by a function known as the characteristic. This function is used to find conservation laws, to prove equivalence between conservation laws, and to prove the converse of Noether's Theorem. Transferring these results to difference equations is nontrivial, largely because difference operators are not derivations and do not obey the chain rule for derivatives. We show how these problems may be resolved and illustrate various uses of the characteristic. In particular, we establish the converse of Noether's Theorem for difference equations, we show (without taking a continuum limit) that the conservation laws in the infinite family generated by Rasin and Schiff are distinct, and we obtain all five-point conservation laws for the potential Lotka-Volterra equation

Reposicionamiento de drogas efectos de la combinación de metformina y propanolol sobre modelos de cáncer colorrectal

El reposicionamiento de drogas en oncología se refiere al uso de fármacos originalmente formulados para otras indicaciones que mostraron potencial antitumoral. En este trabajo, se seleccionó un grupo de drogas en reposicionamiento que incluyen metformina (M, utilizada en el tratamiento de la diabetes), propranolol (P, indicado para tratar la hipertensión), cloroquina (CQ, se usa en el tratamiento o prevención de la malaria), DHEA (un precursor de hormonas sexuales), orlistat (empleado en el tratamiento de la obesidad), atorvastatina (utilizado para tratar niveles altos de colesterol) y dicloroacetato (un inhibidor de la piruvato deshidrogenasa cinasa). El potencial antitumoral de estos fármacos se evaluó in vitro en células de cáncer de colon humano HCT116 y HT29 a través de ensayos de viabilidad estándar, individualmente o de forma combinada. Todos los fármacos probados inhibieron significativamente la proliferación de células HCT116 y HT29 de una manera dependiente de la dosis. De las combinaciones probadas, M+P resultó la más atractiva en ambas líneas celulares, ya que mostró una fuerte inhibición del crecimiento incluso combinando dosis bajas de ambos fármacos (P <0,001). Adicionalmente, el tratamiento mostro efectos significativos tanto sobre la capacidad migratoria celular, aumentando el número de adhesiones focales en células tratadas, como en los niveles de apoptosis que también se vieron incrementados por el tratamiento. Los datos preliminares de un modelo in vivo con ratones BALB/c bajo un protocolo de carcinogénesis estándar de azoximetano (carcinógeno iniciador)/sulfato de dextrano (agente promotor) indicaron un beneficio potencial de la combinación M+P en la prevención del desarrollo de tumores de colon, sin síntomas asociados de toxicidad. A través de la tinción inmunohistoquímica para el antígeno Ki67 se detectó un menor número de células proliferativas en tumores tratados, lo que confirmó el efecto del tratamiento in vivo. En conjunto, nuestros resultados sugieren que la terapia con medicamentos reposicionados podría ser de interés para el tratamiento del cáncer de colon y, en particular, la combinación de M+P podría inhibir su desarrollo y potencialmente el desarrollo de metástasisFil: Anselmino L.E.. Universidad Nacional de RosarioFil: Baglioni M.V.. Universidad Nacional de RosarioFil: Rico M.J.. Universidad Nacional de RosarioFil: Rozados V.R.. Universidad Nacional de RosarioFil: Scharovsky O.G.. Universidad Nacional de RosarioFil: Fernández C.O.. Universidad Nacional de RosarioFil: Martínez-Marignac V.. Universidad Nacional de RosarioFil: Menacho-Márquez M.. Universidad Nacional de Rosari

The instrument suite of the European Spallation Source

An overview is provided of the 15 neutron beam instruments making up the initial instrument suite of the European Spallation Source (ESS), and being made available to the neutron user community. The ESS neutron source consists of a high-power accelerator and target station, providing a unique long-pulse time structure of slow neutrons. The design considerations behind the time structure, moderator geometry and instrument layout are presented. The 15-instrument suite consists of two small-angle instruments, two reflectometers, an imaging beamline, two single-crystal diffractometers; one for macromolecular crystallography and one for magnetism, two powder diffractometers, and an engineering diffractometer, as well as an array of five inelastic instruments comprising two chopper spectrometers, an inverse-geometry single-crystal excitations spectrometer, an instrument for vibrational spectroscopy and a high-resolution backscattering spectrometer. The conceptual design, performance and scientific drivers of each of these instruments are described. All of the instruments are designed to provide breakthrough new scientific capability, not currently available at existing facilities, building on the inherent strengths of the ESS long-pulse neutron source of high flux, flexible resolution and large bandwidth. Each of them is predicted to provide world-leading performance at an accelerator power of 2 MW. This technical capability translates into a very broad range of scientific capabilities. The composition of the instrument suite has been chosen to maximise the breadth and depth of the scientific impact o

Observation of ηc(2S)→ppˉ\eta_{c}(2S) \to p \bar p and search for X(3872)→ppˉX(3872) \to p \bar p decays

The first observation of the decay $\eta_{c}(2S) \to p \bar p$ is reported using proton-proton collision data corresponding to an integrated luminosity of $3.0\rm \, fb^{-1}$ recorded by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. The $\eta_{c}(2S)$ resonance is produced in the decay $B^{+} \to [c\bar c] K^{+}$. The product of branching fractions normalised to that for the $J/\psi$ intermediate state, ${\cal R}_{\eta_{c}(2S)}$, is measured to be \begin{align*} {\cal R}_{\eta_{c}(2S)}\equiv\frac{{\mathcal B}(B^{+} \to \eta_{c}(2S) K^{+}) \times {\mathcal B}(\eta_{c}(2S) \to p \bar p)}{{\mathcal B}(B^{+} \to J/\psi K^{+}) \times {\mathcal B}(J/\psi\to p \bar p)} =~& (1.58 \pm 0.33 \pm 0.09)\times 10^{-2}, \end{align*} where the first uncertainty is statistical and the second systematic. No signals for the decays $B^{+} \to X(3872) (\to p \bar p) K^{+}$ and $B^{+} \to \psi(3770) (\to p \bar p) K^{+}$ are seen, and the 95\% confidence level upper limits on their relative branching ratios are % found to be ${\cal R}_{X(3872)}<0.25\times10^{-2}$ and ${\cal R}_{\psi(3770))}<0.10$. In addition, the mass differences between the $\eta_{c}(1S)$ and the $J/\psi$ states, between the $\eta_{c}(2S)$ and the $\psi(2S)$ states, and the natural width of the $\eta_{c}(1S)$ are measured as \begin{align*} M_{J/\psi} - M_{\eta_{c}(1S)} =~& 110.2 \pm 0.5 \pm 0.9 \rm \, MeV, M_{\psi(2S)} -M_{\eta_{c}(2S)} =~ & 52.5 \pm 1.7 \pm 0.6 \rm \, MeV, \Gamma_{\eta_{c}(1S)} =~& 34.0 \pm 1.9 \pm 1.3 \rm \, MeV. \end{align*}Comment: 16 pages, 2 figures All figures and tables, along with any supplementary material and additional information, are available at https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2016-016.htm

Highly-parallelized simulation of a pixelated LArTPC on a GPU

The rapid development of general-purpose computing on graphics processing units (GPGPU) is allowing the implementation of highly-parallelized Monte Carlo simulation chains for particle physics experiments. This technique is particularly suitable for the simulation of a pixelated charge readout for time projection chambers, given the large number of channels that this technology employs. Here we present the first implementation of a full microphysical simulator of a liquid argon time projection chamber (LArTPC) equipped with light readout and pixelated charge readout, developed for the DUNE Near Detector. The software is implemented with an end-to-end set of GPU-optimized algorithms. The algorithms have been written in Python and translated into CUDA kernels using Numba, a just-in-time compiler for a subset of Python and NumPy instructions. The GPU implementation achieves a speed up of four orders of magnitude compared with the equivalent CPU version. The simulation of the current induced on 10^3 pixels takes around 1 ms on the GPU, compared with approximately 10 s on the CPU. The results of the simulation are compared against data from a pixel-readout LArTPC prototype

Helechos y licofitas: actualización de la flora del Valle de Lerma - Salta, Argentina

Abstract: The Lerma Valley is located in the center of the province of Salta, Argentina. Its vegetation corresponds to two phytogeographic domains, Amazonian domain and Chaco domain. An updated list of the diversity of ferns and lycophytes is presented as a result of new collections and a review of herbarium specimens and specific bibliography. We registered 115 taxa, 107 ferns, and 8 lycophytes, belonging to 16 and 2 families respectively, which correspond to an increase of 22 new taxa compared to the original flora. Three records are cited for the first time for the northwest region of Argentina, Microgramma vaccinifolia, Pellaea atropurpurea and Pteris multifida. The three best-represented families are Pteridaceae with 34 taxa, Polypodiaceae with 19, and Aspleniaceae with 14. Of the 115 taxa identified, 110 belong to the native flora and five are naturalized species.Resumen: El Valle de Lerma se encuentra en el centro de la provincia de Salta, Argentina. Su vegetación corresponde a dos dominios fitogeográficos, amazónico y chaqueño. Se presenta un listado actualizado de la diversidad de helechos y licófitas como resultado de nuevas colectas y revisión de ejemplares de herbarios y bibliografía específica. Se registraron 115 taxones, 107 helechos y 8 licófitas, pertenecientes a 16 y 2 familias respectivamente, lo que corresponde a un incremento de 22 nuevos taxones respecto a la flora original. Tres registros se citan por primera vez para la región noroeste de Argentina, Microgramma vaccinifolia, Pellaea atropurpurea y Pteris multifida. Las tres familias mejor representadas son, Pteridaceae con 34 taxones, Polypodiaceae con 19, y Aspleniaceae con 14. De los 115 taxones identificados, 110 pertenecen a la flora nativa y cinco son especies naturalizadas

An experimental and theoretical study of nitrogen-broadened acetylene lines

We present experimental nitrogen-broadening coefficients derived from Voigt profiles of isotropic Raman Q-lines measured in the ν2 band of acetylene (C2H2) at 150K and 298K, and compare them to theoretical values obtained through calculations that were carried out specifically for this work. Namely, full classical calculations based on Gordon[U+05F3]s approach, two kinds of semi-classical calculations based on Robert-Bonamy method as well as full quantum dynamical calculations were performed. All the computations employed exactly the same ab initio potential energy surface for the C2H2-N2 system which is, to our knowledge, the most realistic, accurate and up-to-date one. The resulting calculated collisional half-widths are in good agreement with the experimental ones only for the full classical and quantum dynamical methods. In addition, we have performed similar calculations for IR absorption lines and compared the results to bibliographic values. Results obtained with the full classical method are again in good agreement with the available room temperature experimental data. The quantum dynamical close-coupling calculations are too time consuming to provide a complete set of values and therefore have been performed only for the R(0) line of C2H2. The broadening coefficient obtained for this line at 173K and 297K also compares quite well with the available experimental data. The traditional Robert-Bonamy semi-classical formalism, however, strongly overestimates the values of half-width for both Q- and R-lines. The refined semi-classical Robert-Bonamy method, first proposed for the calculations of pressure broadening coefficients of isotropic Raman lines, is also used for IR lines. By using this improved model that takes into account effects from line coupling, the calculated semi-classical widths are significantly reduced and closer to the measured ones. © 2014 Elsevier Ltd.D.B. and R.Z.M. acknowledge the financial support of the Ministry of Economy and Competitiveness through Research Grant FIS2012-38175. Q.M. acknowledges the financial support from NSF under Grant 1228861. D.B., R.Z.M and F.T. acknowledge financial support from the European GDRI HiRESMIR (high resolution microwave, infrared and Raman molecular spectroscopy).Peer Reviewe