The nuclear contacts and short range correlations in nuclei

Atomic nuclei are complex strongly interacting systems and their exact theoretical description is a long-standing challenge. An approximate description of nuclei can be achieved by separating its short and long range structure. This separation of scales stands at the heart of the nuclear shell model and effective field theories that describe the long-range structure of the nucleus using a mean- field approximation. We present here an effective description of the complementary short-range structure using contact terms and stylized two-body asymptotic wave functions. The possibility to extract the nuclear contacts from experimental data is presented. Regions in the two-body momentum distribution dominated by high-momentum, close-proximity, nucleon pairs are identified and compared to experimental data. The amount of short-range correlated (SRC) nucleon pairs is determined and compared to measurements. Non-combinatorial isospin symmetry for SRC pairs is identified. The obtained one-body momentum distributions indicate dominance of SRC pairs above the nuclear Fermi-momentum.Comment: Accepted for publication in Physics Letters. 6 pages, 2 figure

Quantum Electrodynamics vacuum polarization solver

The self-consistent modeling of vacuum polarization due to virtual electron-positron fluctuations is of relevance for many near term experiments associated with high intensity radiation sources and represents a milestone in describing scenarios of extreme energy density. We present a generalized finite-difference time-domain solver that can incorporate the modifications to Maxwell's equations due to vacuum polarization. Our multidimensional solver reproduced in one dimensional configurations the results for which an analytic treatment is possible, yielding vacuum harmonic generation and birefringence. The solver has also been tested for two-dimensional scenarios where finite laser beam spot sizes must be taken into account. We employ this solver to explore different types of counter-propagating configurations that can be relevant for future planned experiments aiming to detect quantum vacuum dynamics at ultra-high electromagnetic field intensities

Fractional Newton-Raphson Method Accelerated with Aitken's Method

The Newton-Raphson (N-R) method is characterized by the fact that generating a divergent sequence can lead to the creation of a fractal, on the other hand the order of the fractional derivatives seems to be closely related to the fractal dimension, based on the above, a method was developed that makes use of the N-R method and the fractional derivative of Riemann-Liouville (R-L) that has been named as the Fractional Newton-Raphson (F N-R) method. In the following work we present a way to obtain the convergence of the F N-R method, which seems to be at least linearly convergent for the case where the order $\alpha$ of the derivative is different from one, a simplified way to construct the fractional derivative and fractional integral operators of R-L is presented, an introduction to the Aitken's method is made and it is explained why it has the capacity to accelerate the convergence of iterative methods to finally present the results that were obtained when implementing the Aitken's method in F N-R method.Comment: Newton-Raphson Method, Fractional Calculus, Fractional Derivative of Riemann-Liouville, Method of Aitken. arXiv admin note: substantial text overlap with arXiv:1710.0763

Study of X52 steel in seawater with biocides under turbulent flow conditions

This work presents the corrosion study of the API X52 pipeline steel immersed in seawater without biocide and with 0,25, 0,5 and 0,75 ppm of biocide, under static and dynamic (turbulent flow) conditions at room temperature and atmospheric pressure. The total exposure time of the steel sample in test solution was 24h. In order to control the hydrodynamic conditions, a rotating cylinder electrode(RCE) was used. The rotation speed was 1000 RPM. The steel samples were immersed in the test solution, then, an electrochemical corrosion study using linear polarization resistance (LPR), electrochemical impedance spectroscopy (EIS) and polarization curves (PC) was made. In the superficial analysis of the steel samples, a scanning electronic microscopy was used. The results of the electrochemical study shown that the corrosion rate is higher under turbulent flow conditions than static conditions, and as the biocide concentration increased in the test solution, the corrosion rate decreased. A localized corrosion type was found in all the samples tested

Magnetic frame-dragging correction to the electromagnetic solution of a compact neutron star

Neutron stars are commonly modelled as a spherical, rotating perfect conductors with a predominant intrinsic dipolar magnetic field anchored to their stellar crust. If compact enough, General Relativity modifies Maxwell's equations, leading to changes in the interior and exterior electromagnetic solutions. We present analytic solutions for a slowly-rotating magnetized neutron star that include the frame-dragging correction to the magnetic field components. For typical compactness values, i.e. $R_s \sim 0.5 [R_*]$, we show that the new terms account for a $0.43\%$ decrease in magnetic field strength at the equator and an average $1\%$ vectorial angle correction, both compared to the case without the magnetic frame-dragging correction. This correction leads to a self-consistent redistribution of the surface azimuthal current. We tested the validity of the derived solution by prescribing it as an initial value problem to two-dimensional particle-in-cell simulations. We observe a lower early-stage transient amplitude which reflects the proximity between the derived and exact solutions. At later times, our solution reduces the azimuthal electric field amplitude by almost an order of magnitude, demonstrating that simulations are more accurate at the expense of a more involved initialization. We show that this can potentially lead to a reduction of simulation runtimes.Comment: 13 pages, 8 figure

Quantum electrodynamics vacuum polarization solver

The self-consistent modeling of vacuum polarization due to virtual electron-positron fluctuations is of relevance for many near term experiments associated with high intensity radiation sources and represents a milestone in describing scenarios of extreme energy density. We present a generalized finite-difference time-domain solver that can incorporate the modifications to Maxwell’s equations due to vacuum polarization. Our multidimensional solver reproduced in one-dimensional configurations the results for which an analytic treatment is possible, yielding vacuum harmonic generation and birefringence. The solver has also been tested for two-dimensional scenarios where finite laser beam spot sizes must be taken into account. We employ this solver to explore different types of laser configurations that can be relevant for future planned experiments aiming to detect quantum vacuum dynamics at ultra-high electromagnetic field intensities.info:eu-repo/semantics/publishedVersio

The experience of preparing a closing session

This short article explains the development of a closing project developed with students of English as a foreign language. The project emerged with the idea of innovating in the classroom and trying to make links with their reality which could help developed a more meaningful process. Students involved study English for different reasons but most of them do it as a complementary activity for their job or study. They attend classes on the weekends so this project was enhanced also with the intention to break the old scheme of the foreign language as an additional but unconnected activity. The cooperative work and the motivation arisen from this task were some of the more valuable results

Laser Calibration System for Time of Flight Scintillator Arrays

A laser calibration system was developed for monitoring and calibrating time of flight (TOF) scintillating detector arrays. The system includes setups for both small- and large-scale scintillator arrays. Following test-bench characterization, the laser system was recently commissioned in experimental Hall B at the Thomas Jefferson National Accelerator Facility for use on the new Backward Angle Neutron Detector (BAND) scintillator array. The system successfully provided time walk corrections, absolute time calibration, and TOF drift correction for the scintillators in BAND. This showcases the general applicability of the system for use on high-precision TOF detectors.Comment: 11 pages, 11 figure

Proyectos finales integradores : una alternativa para enseñar y aprender activamente

Este número de Reflexiones Pedagógicas busca presentar los proyectos finales integradores (PFI) como una opción de enseñanza y aprendizaje activo. Se explica qué son los PFI, así como las ventajas que se obtienen al hacer uso de estos en una o más asignaturas. Por otro lado, se relatan las experiencias que el programa de Ingeniería Biomédica ha encontrado en la implementación de PFI en algunas de sus asignaturas. Por último, se exponen algunos retos y desafíos inherentes a la implementación de esta alternativa pedagógica. Esperamos que lo compartido en este número sea de utilidad para continuar en la ruta del aprendizaje activo y significativo, el cual implica retos tanto para los docentes como para los estudiantes. Luego de lo vivido como equipo de profesores, consideramos que esta experiencia es altamente transferible a otros campos de conocimiento. Los resultados son gratificantes, así lo hemos evidenciado en cada momento con los estudiantes

Potential of mathematical modeling in fruit quality

A review of mathematical modeling applied to fruit quality showed that these models ranged inresolution from simple yield equations to complex  representations of processes as respiration, photosynthesis and assimilation of nutrients. The latter models take into account complex  genotype environment interactions to estimate their effects on growth and yield. Recently, models are used to estimate seasonal changes in quality traits as fruit size, dry matter, water content and the concentration of sugars and acids, which are very important for flavor and aroma. These models have demonstrated their ability to generate relationships between physiological variables and quality attributes (allometric relations). This new kind of hybrid models has sufficient complexity to predict quality traits behavior