Density operator of a system pumped with polaritons: A Jaynes-Cummings like approach

We investigate the effects of considering two different incoherent pumpings over a microcavity-quantum dot system modelled using the Jaynes-Cummings Hamiltonian. When the system is incoherently pumped with polaritons it is able to sustain a large number of photons inside the cavity with Poisson-like statistics in the stationary limit, and also leads to a separable exciton-photon state. We also investigate the effects of both types of pumpings (Excitonic and Polaritonic) in the emission spectrum of the cavity. We show that the polaritonic pumping as considered here is unable to modify the dynamical regimes of the system as the excitonics pumping does. Finally, we obtain a closed form expression for the negativity of the density matrices that the quantum master equation considered here generates.Comment: 16 pages, 4 figure

Quantum correlations between two distant cavity QED systems coupled by a mechanical resonator

Achieving quantum correlations between two distant systems is a desirable feature for quantum networking. In this work, we study a system composed of two quantum emitter-cavity subsystems spatially separated. A mechanical resonator couples to either both quantum emitters or both cavities leading to quantum correlations between both subsystems such as non-local light-matter dressed states and cavity-cavity normal mode splitting. These indirect couplings can be explained by an effective Hamiltonian for large energy detuning between the mechanical resonator and the atoms/cavities. Moreover, it is found optimal conditions for the physical parameters of the system in order to maximize the entanglement of such phonon-mediated couplings

Using machine learning and information visualisation for discovering latent topics in Twitter news

We propose a method to discover latent topics and visualise large collections of tweets for easy identification and interpretation of topics, and exemplify its use with tweets from a Colombian mass media giant in the period 2014--2019. The latent topic analysis is performed in two ways: with the training of a Latent Dirichlet Allocation model, and with the combination of the FastText unsupervised model to represent tweets as vectors and the implementation of K-means clustering to group tweets into topics. Using a classification task, we found that people respond differently according to the various news topics. The classification tasks consists of the following: given a reply to a news tweet, we train a supervised algorithm to predict the topic of the news tweet solely from the reply. Furthermore, we show how the Colombian peace treaty has had a profound impact on the Colombian society, as it is the topic in which most people engage to show their opinions.Comment: 10 pages, 6 figures, to be presented at SmartTech-IC 201

DYNAMICS AND ENTANGLEMENT OF A QUANTUM DOT-CAVITY SYSTEM COUPLED BY A NON-LINEAR OPTICAL INTERACTION

We propose a simple theoretical model for a dissipative quantum dot-microcavity system interacting with a non-linear optical interaction. The Lindblad master equation formalism is considered to study the full dynamics for both weak and strong coupling regimes. The photoluminescence spectra of the system at the stationary limit is calculated in an exact form, and the effect due to non-linear optical interaction is explicitly evidenced. The entanglement of the system is calculated, and we found revivals and sudden death are evidenced. We also study the relationship between the light-matter and non-linear optical interaction terms by calculating the average photon number.Se propone un modelo teórico sencillo para un sistema disipativo de punto cuántico-microcavidad que interactúan a través de una interacción óptica no lineal. El formalismo de la ecuación maestra en la forma de Lindblad es considerado para estudiar la dinámica del sistema en los regímenes de acoplamiento débil y fuerte, respectivamente. El espectro de fotoluminiscencia del sistema en el límite estacionario es calculado en forma exacta, y se muestra el efecto de la interacción óptica no lineal explícitamente sobre éste. Se calcula el entrelazamiento del sistema, y se encuentra resurgimientos y muerte s\'ubita del entrelazamiento. Adicionalmente, se estudia la relación entre los términos de interacción luz-materia (Jaynes-Cummings) e interacción óptica no lineal (medio Kerr) por medio del número medio de fotones

Returning home: forced conscription, reintegration, and mental health status of former abductees of the Lord's Resistance Army in northern Uganda

<p>Abstract</p> <p>Background</p> <p>Since the late 1980s, the Lord's Resistance Army (LRA), a spiritualist rebel group in northern Uganda, has killed and mutilated thousands of civilians and abducted an estimated 52,000 to 75,000 people to serve as soldiers, porters, and sex slaves for its commanders. This study examines the types of violence to which former abductees have been exposed and the extent to which these acts have affected their psychological well-being.</p> <p>Methods</p> <p>This is a cross-sectional study of 2,875 individuals selected through a multi-stage stratified cluster sampling design conducted in 8 districts of northern Uganda. Multivariate logistic regressions were performed with symptoms for Post-traumatic Stress Disorder (PTSD) and depression as the main outcome measures.</p> <p>Results</p> <p>One-third of the respondents (33%) self-reported having experienced abduction (49% among the Acholi, the largest tribal group in northern Uganda). Over half (56%) of all the respondents and over two-thirds of those who experienced abduction met the criteria for symptoms of post-traumatic stress disorder (PTSD). Multivariate analysis shows that several factors increased the risk of former LRA abductees developing symptoms of PTSD. These factors included gender (females were more susceptible than males), being a member of the Acholi ethnic group, participating in or witnessing a cumulative number of traumatic events, and encountering difficulties re-integrating into communities after abduction. Factors associated with increased risk of meeting criteria for symptoms of depression included older age of males at the time of abduction, lower score on social relationship scale, high incidence of general traumatic event exposure, high incidence of forced acts of violence, and problems reintegrating into communities after abduction.</p> <p>Conclusion</p> <p>Abduction and forced conscription of civilians has affected the psychological well-being of a significant number of northern Ugandans. The sources of psychological trauma are multiple, ranging from witnessing to being forced to commit violent acts, and compounded by prolonged exposure to violence, often for months or years. Community-based mental health care services and reintegration programs are needed to facilitate the reintegration of former abductees back into their communities.</p

Distortion product otoacoustic emissions as a health surveillance technique for hearing screening in workers in the steel manufacturing industry

BACKGROUND : Distortion product otoacoustic emissions (DPOAEs) are a promising screening technique for the early detection of subtle noise-induced cochlear function changes. OBJECTIVES : To determine the applicability of DPOAEs as a health surveillance technique for the early detection of noise-induced hearing loss (NIHL) in workers at a steel manufacturing industry. METHODS : DPOAE measurements were recorded in 20 participants with no history of occupational noise exposure and 20 participants exposed to noise in the steel manufacturing industry. Participants were not exposed to noise for at least 48 hours prior to testing. All participants were male, with normal audiometric thresholds of ≤15 dB HL. The DPOAE presence and response levels for different frequencies were compared between the two groups. The study further evaluated the shortterm test-retest repeatability of DPOAE measurements. RESULTS : The noise-exposed group had significantly lower DPOAE response amplitudes than the control group for all the tested frequencies: p<0.001 at 2002 to 4004 Hz; p=0.01 and p=0.001 at 6348 and 7996 Hz, respectively, suggesting early outer hair cell damage in the noise-exposed group. DPOAEs showed good reproducibility. CONCLUSION : DPOAEs appear to be a sensitive technique for detecting noise-induced subtle cochlear function changes. DPOAEs could be used as a health surveillance technique in conjunction with pure tone audiometry for the early detection of NIHL in the steel manufacturing industry.http://www.occhealth.co.zaam2018Speech-Language Pathology and Audiolog