Flow of strange and charm particles in Pb--Pb collisions at sqrt{s_{NN}} = 2.76 TeV measured with ALICE

The ALICE experiment studies Pb-Pb collisions at the LHC in order to investigate the properties of the hot and dense QCD matter at extreme energy densities. Recent results from ALICE in identified particle flow allow for the exploration of the collective properties of the medium created in heavy-ion collisions. In this paper, I give special attention to strange and charm particles which probe the medium differently and thus provide new constraints for the study of its properties. The paper covers results on elliptic flow for pion, kaon, kzero, antiproton, phi, lambda, xi, omega, dplus, dzero and dstar measured at midrapidity by ALICE in Pb-Pb collisions at sqrt{s_{NN}} = 2.76 TeV. I present also the comparison with available models that predict the hydrodynamical evolution of the medium and the energy loss of light and heavy quarks as they travel through.Comment: 6 pages, 7 figures, ICHEP 2012 proceeding

What Dollar Stores Tell Us About Electoral Politics

This essay uses SNAP-authorized dollar stores per district as an indicator of the intersection of rurality and hardship. The authors show that dollar store counts create congressional district clusters that are more socio-economically homogenous than classification based on geographic density does. Up until 2016, the authors find, districts with more dollar stores had been swinging towards the Republican Party, a trend that culminated with the election of Donald Trump. But in the 2018 midterms, mid-to high dollar store districts swung as sharply towards the Democrats as did low dollar store districts

La guerra contra el narcotráfico: ¿una guerra perdida?

El presente trabajo trata sobre los problemas derivados del narcotráfico en México, por lo que se realiza un estudio de los resultados que ha tenido la guerra frontal emprendida por el presidente Calderón con base en datos proporcionados por instancias oficiales, como la Procuraduría General de la República, y organizaciones civiles, como México Unido Contra la Delincuencia, y en datos internacionales proporcionados por el Índice de Incidencia Delictiva. Todo ello con el propósito de analizar tanto los avances obtenidos contra el narcotráfico como la percepción ciudadana de la eficacia de la estrategia implementada.El presente trabajo trata sobre los problemas derivados del narcotráfico en México, por lo que se realiza un estudio de los resultados que ha tenido la guerra frontal emprendida por el presidente Calderón con base en datos proporcionados por instancias oficiales, como la Procuraduría General de la República, y organizaciones civiles, como México Unido Contra la Delincuencia, y en datos internacionales proporcionados por el Índice de Incidencia Delictiva. Todo ello con el propósito de analizar tanto los avances obtenidos contra el narcotráfico como la percepción ciudadana de la eficacia de la estrategia implementada

A versatile scanning photocurrent mapping system to characterize optoelectronic devices based on 2D materials

The investigation of optoelectronic devices based on two-dimensional materials and their heterostructures is a very active area of investigation with both fundamental and applied aspects involved. We present a description of a home-built scanning photocurrent microscope that we have designed and developed to perform electronic transport and optical measurements of two-dimensional materials based devices. The complete system is rather inexpensive (<10000 EUR) and it can be easily replicated in any laboratory. To illustrate the setup we measure current-voltage characteristics, in dark and under global illumination, of an ultra-thin PN junction formed by the stacking of an n-doped few-layer MoS2 flake onto a p-type MoS2 flake. We then acquire scanning photocurrent maps and by mapping the short circuit current generated in the device under local illumination we find that at zero bias the photocurrent is generated mostly in the region of overlap between the n-type and p-type flakes.Comment: 9 pages, 3 figures, 1 table, supporting informatio

Simulating the behavior of the human brain on GPUS

The simulation of the behavior of the Human Brain is one of the most important challenges in computing today. The main problem consists of finding efficient ways to manipulate and compute the huge volume of data that this kind of simulations need, using the current technology. In this sense, this work is focused on one of the main steps of such simulation, which consists of computing the Voltage on neurons’ morphology. This is carried out using the Hines Algorithm and, although this algorithm is the optimum method in terms of number of operations, it is in need of non-trivial modifications to be efficiently parallelized on GPUs. We proposed several optimizations to accelerate this algorithm on GPU-based architectures, exploring the limitations of both, method and architecture, to be able to solve efficiently a high number of Hines systems (neurons). Each of the optimizations are deeply analyzed and described. Two different approaches are studied, one for mono-morphology simulations (batch of neurons with the same shape) and one for multi-morphology simulations (batch of neurons where every neuron has a different shape). In mono-morphology simulations we obtain a good performance using just a single kernel to compute all the neurons. However this turns out to be inefficient on multi-morphology simulations. Unlike the previous scenario, in multi-morphology simulations a much more complex implementation is necessary to obtain a good performance. In this case, we must execute more than one single GPU kernel. In every execution (kernel call) one specific part of the batch of the neurons is solved. These parts can be seen as multiple and independent tridiagonal systems. Although the present paper is focused on the simulation of the behavior of the Human Brain, some of these techniques, in particular those related to the solving of tridiagonal systems, can be also used for multiple oil and gas simulations. Our studies have proven that the optimizations proposed in the present work can achieve high performance on those computations with a high number of neurons, being our GPU implementations about 4× and 8× faster than the OpenMP multicore implementation (16 cores), using one and two NVIDIA K80 GPUs respectively. Also, it is important to highlight that these optimizations can continue scaling, even when dealing with a very high number of neurons.This project has received funding from the European Union’s Horizon 2020 Research and Innovation Programme under Grant Agreement No. 720270 (HBP SGA1), from the Spanish Ministry of Economy and Competitiveness under the project Computación de Altas Prestaciones VII (TIN2015-65316-P), the Departament d’Innovació, Universitats i Empresa de la Generalitat de Catalunya, under project MPEXPAR: Models de Programació i Entorns d’Execució Parallels (2014-SGR-1051). We thank the support of NVIDIA through the BSC/UPC NVIDIA GPU Center of Excellence, and the European Union’s Horizon 2020 Research and Innovation Program under the Marie Sklodowska-Curie Grant Agreement No. 749516.Peer ReviewedPostprint (published version

Vortex ratchet reversal: The role of interstitial vortices

Triangular arrays of Ni nanotriangles embedded in superconducting Nb films exhibit unexpected dynamical vortex effects. Collective pinning with a vortex lattice configuration different from the expected fundamental triangular "Abrikosov state" is found. The vortex motion which prevails against the triangular periodic potential is produced by channelling effects between triangles. Interstitial vortices coexisting with pinned vortices in this asymmetric potential, lead to ratchet reversal, i.e. a DC output voltage which changes sign with the amplitude of an applied alternating drive current. In this landscape, ratchet reversal is always observed at all magnetic fields (all numbers of vortices) and at different temperatures. The ratchet reversal is unambiguously connected to the presence of two locations for the vortices: interstitial and above the artificial pinning sites.Comment: 21 pages, 4 figures, 1 Tabl