Ethnic Microaggressions, Traumatic Stress Symptoms, And Latino Depression: A Moderated Mediational Model

Although ethnic microaggressions have received increased empirical attention in recent years, there remains a paucity of research regarding how these subtle covert forms of discrimination contribute to Latino mental health. The present study examined the role of traumatic stress symptoms underlying the relationship between ethnic microaggressions and depression. Further, ethnic identity and general self-efficacy were tested as moderators between the ethnic microaggressions and traumatic stress link. Among a sample of 113 Latino adults, moderated mediational analyses revealed statistically significant conditional indirect effects in which traumatic stress symptoms mediated the relationship between ethnic microaggressions and depression while ethnic identity and self-efficacy functioned as moderators. The major findings suggested that the indirect effects were the most robust within low ethnic identity and low self-efficacy. The findings are discussed within a stress and coping framework that highlight the internal resources and stress responses associated with experiencing ethnic microaggressions

Canonically Transformed Detectors Applied to the Classical Inverse Scattering Problem

The concept of measurement in classical scattering is interpreted as an overlap of a particle packet with some area in phase space that describes the detector. Considering that usually we record the passage of particles at some point in space, a common detector is described e.g. for one-dimensional systems as a narrow strip in phase space. We generalize this concept allowing this strip to be transformed by some, possibly non-linear, canonical transformation, introducing thus a canonically transformed detector. We show such detectors to be useful in the context of the inverse scattering problem in situations where recently discovered scattering echoes could not be seen without their help. More relevant applications in quantum systems are suggested.Comment: 8 pages, 15 figures. Better figures can be found in the original article, wich can be found in http://www.sm.luth.se/~norbert/home_journal/electronic/v12s1.html Related movies can be found in www.cicc.unam.mx/~mau

New gamma/hadron separation parameters for a neural network for HAWC

The High-Altitude Water Cherenkov experiment (HAWC) observatory is located 4100 meters above sea level. HAWC is able to detect secondary particles from extensive air showers (EAS) initiated in the interaction of a primary particle (either a gamma or a charged cosmic ray) with the upper atmosphere. Because an overwhelming majority of EAS events are triggered by cosmic rays, background noise suppression plays an important role in the data analysis process of the HAWC observatory. Currently, HAWC uses cuts on two parameters (whose values depend on the spatial distribution and luminosity of an event) to separate gamma-ray events from background hadronic showers. In this work, a search for additional gamma-hadron separation parameters was conducted to improve the efficiency of the HAWC background suppression technique. The best-performing parameters were integrated to a feed-foward Multilayer Perceptron Neural Network (MLP-NN), along with the traditional parameters. Various iterations of MLP-NN's were trained on Monte Carlo data, and tested on Crab data. Preliminary results show that the addition of new parameters can improve the significance of the point source at high-energies (~ TeV), at the expense of slightly worse performance in conventional low-energy bins (~ GeV). Further work is underway to improve the efficiency of the neural network at low energies.Comment: Presented at the 35th International Cosmic Ray Conference (ICRC2017), Bexco, Busan, Korea. See arXiv:1708.02572 for all HAWC contribution

Spin frequency distributions of binary millisecond pulsars

Rotation-powered millisecond radio pulsars have been spun up to their present spin period by a $10^8$ - $10^9$ yr long X-ray-bright phase of accretion of matter and angular momentum in a low-to-intermediate mass binary system. Recently, the discovery of transitional pulsars that alternate cyclically between accretion and rotation-powered states on time scales of a few years or shorter, has demonstrated this evolutionary scenario. Here, we present a thorough statistical analysis of the spin distributions of the various classes of millisecond pulsars to assess the evolution of their spin period between the different stages. Accreting sources that showed oscillations exclusively during thermonuclear type I X-ray bursts (nuclear-powered millisecond pulsars) are found to be significantly faster than rotation-powered sources, while accreting sources that possess a magnetosphere and show coherent pulsations (accreting millisecond pulsars) are not. On the other hand, if accreting millisecond pulsars and eclipsing rotation-powered millisecond pulsars form a common class of transitional pulsars, these are shown to have a spin distribution intermediate between the faster nuclear-powered millisecond pulsars and the slower non-eclipsing rotation-powered millisecond pulsars. We interpret these findings in terms of a spin-down due to the decreasing mass-accretion rate during the latest stages of the accretion phase, and in terms of the different orbital evolutionary channels mapped by the various classes of pulsars. We summarize possible instrumental selection effects, showing that even if an unbiased sample of pulsars is still lacking, their influence on the results of the presented analysis is reduced by recent improvements in instrumentation and searching techniques.Comment: Accepted for publication in A&A (6 pages, 4 figures

Two interacting atoms in a cavity: exact solutions, entanglement and decoherence

We address the problem of two interacting atoms of different species inside a cavity and find the explicit solutions of the corresponding eigenvalues and eigenfunctions using a new invariant. This model encompasses various commonly used models. By way of example we obtain closed expressions for concurrence and purity as a function of time for the case where the cavity is prepared in a number state. We discuss the behaviour of these quantities and and their relative behaviour in the concurrence-purity plane.Comment: 10 pages, 3 figure

Kubo formula for Floquet states and photoconductivity oscillations in a 2D electron gas

The recent discovery of the microwave induced vanishing resistance states in a two dimensional electron system (2DES) is an unexpected and surprising phenomena. In these experiments the magnetoresistance of a high mobility 2DES under the influence of microwave radiation of frequency $\omega$ at moderate values of the magnetic field, exhibits strong oscillations with zero-resistance states (ZRS) governed by the ratio $\omega /\omega_c$, where $\omega_c$ is the cyclotron frequency. In this work we present a model for the photoconductivity of a two dimensional electron system (2DES) subjected to a magnetic field. The model includes the microwave and Landau contributions in a non-perturbative exact way, impurity scattering effects are treated perturbatively. In our model, the Landau-Floquet states act coherently with respect to the oscillating field of the impurities, that in turn induces transitions between these levels. Based on this formalism, we provide a Kubo-like formula that takes into account the oscillatory Floquet structure of the problem. We study the effects of both short-range and long-range disorder on the photoconductivity. Our calculation yields a magnetoresistance oscillatory behavior with the correct period and phase. It is found that, in agreement with experiment, negative dissipation can only be induced in very high mobility samples. We analyze the dependence of the results on the microwave power and polarization. For high-intensity radiation multi-photon processes take place predicting new negative-resistance states centered at $\omega / \omega_c=1/2$, and $\omega / \omega_c= 3/2$.Comment: Final version, accepted for publication in Phys. Rev.

Decoherence at constant excitation

We present a simple exactly solvable extension of of the Jaynes-Cummings model by adding dissipation. This is done such that the total number of excitations is conserved. The Liouville operator in the resulting master equation can be reduced to blocks of $4\times 4$ matrices