Quantum fields near phantom-energy `sudden' singularities

This paper is committed to calculations near a type of future singularity driven by phantom energy. At the singularities considered, the scale factor remains finite but its derivative diverges. The general behavior of barotropic phantom energy producing this singularity is calculated under the assumption that near the singularity such fluid is the dominant contributor. We use the semiclassical formula for renormalized stress tensors of conformally invariant fields in conformally flat spacetimes and analyze the softening/enhancing of the singularity due to quantum vacuum contributions. This dynamical analysis is then compared to results from thermodynamical considerations. In both cases, the vacuum states of quantized scalar and spinor fields strengthen the accelerating expansion near the singularity whereas the vacuum states of vector fields weaken it.Comment: 6 pages RevTe

Equivalence between the real time Feynman histories and the quantum shutter approaches for the "passage time" in tunneling

We show the equivalence of the functions $G_{\rm p}(t)$ and $|\Psi(d,t)|^2$ for the ``passage time'' in tunneling. The former, obtained within the framework of the real time Feynman histories approach to the tunneling time problem, using the Gell-Mann and Hartle's decoherence functional, and the latter involving an exact analytical solution to the time-dependent Schr\"{o}dinger equation for cutoff initial waves

Fourier Decomposition of RR Lyrae light curves and the SX Phe population in the central region of NGC 3201

CCD time-series observations of the central region of the globular cluster NGC~3201 were obtained with the aim of performing the Fourier decomposition of the light curves of the RR~Lyrae stars present in that field. This procedure gave the mean values, for the metallicity, of [Fe/H]$_{ZW}=-1.483 \pm 0.006$ (statistical) $\pm 0.090$ (systematical), and for the distance, $5.000 \pm 0.001$~kpc (statistical) $\pm 0.220$ (systematical). The values found from two RRc stars are consistent with those derived previously. The differential reddening of the cluster was investigated and individual reddenings for the RR Lyrae stars were estimated from their $V-I$ curves. We found an average value of $E(B-V)= 0.23 \pm 0.02$. An investigation of the light curves of stars in the {\it blue stragglers} region led to the discovery of three new SX~Phe stars. The period-luminosity relation of the SX~Phe stars was used for an independent determination of the distance to the cluster and of the individual reddenings. We found a distance of 5.0 kpcComment: To appear in Revista Mexicana de Astronom\'ia y Astrof\'isica, Octuber 2014 issue, Vol 50. 17 pages, 10 figure

Science and poetry: poems as an educational tool for biology teaching

Contains fulltext : 253566.pdf (Publisher’s version ) (Open Access

Quantum shutter approach to tunneling time scales with wave packets

The quantum shutter approach to tunneling time scales (G. Garc\'{\i }a-Calder\'{o}n and A. Rubio, Phys. Rev. A \textbf{55}, 3361 (1997)), which uses a cutoff plane wave as the initial condition, is extended in such a way that a certain type of wave packet can be used as the initial condition. An analytical expression for the time evolved wave function is derived. The time-domain resonance, the peaked structure of the probability density (as the function of time) at the exit of the barrier, originally found with the cutoff plane wave initial condition, is studied with the wave packet initial conditions. It is found that the time-domain resonance is not very sensitive to the width of the packet when the transmission process is in the tunneling regime.Comment: 6 page

Dynamical description of the buildup process in resonant tunneling: Evidence of exponential and non-exponential contributions

The buildup process of the probability density inside the quantum well of a double-barrier resonant structure is studied by considering the analytic solution of the time dependent Schr\"{o}dinger equation with the initial condition of a cutoff plane wave. For one level systems at resonance condition we show that the buildup of the probability density obeys a simple charging up law, $| \Psi (\tau) / \phi | =1-e^{-\tau /\tau_0},$ where $\phi$ is the stationary wave function and the transient time constant $\tau_0$ is exactly two lifetimes. We illustrate that the above formula holds both for symmetrical and asymmetrical potential profiles with typical parameters, and even for incidence at different resonance energies. Theoretical evidence of a crossover to non-exponential buildup is also discussed.Comment: 4 pages, 2 figure

Inflammatory Bowel Disease in Latin America: A Systematic Review

BACKGROUND: Inflammatory bowel disease (IBD) is the name given to two inflammatory diseases of the colon and/or small intestine: Crohn disease (CD) and ulcerative colitis (UC). There is no information summarizing the complete body of evidence about IBD in developing regions, including Latin America. OBJECTIVES: To estimate the burden of IBD in Latin America. METHODS: We conducted a systematic review searching published and unpublished studies on major international and regional databases from January 2000 to September 2015. Outcomes considered were incidence, prevalence, mortality, hospitalization attributable, treatment patterns, comparative effectiveness, patient-reported outcomes, and adherence to treatment. Pairs of reviewers independently selected, extracted, and assessed the risk of bias of the studies. Discrepancies were solved by consensus. RESULTS: We retrieved 3445 references, finally including 25 studies. Only 19% of the observational studies had a low risk of bias for participant selection and 60% were based on registries. The incidence ranged from 0.74 to 6.76/100,000 person-years for UC and from 0.24 to 3.5/100,000 person-years for CD. The prevalence rate ranged from 0.99 to 44.3/100,000 inhabitants for UC and 0.24 to 16.7/100,000 inhabitants for CD. Mortality rates ranged from 0.60 to 1.02 for UC and from 0.23 to 0.40 for CD. Patient-reported outcomes showed a decrease in quality of life associated with depression and anxiety and correlated with the time of diagnosis. The most frequently used medication in the studies was mesalazine. CONCLUSIONS: The burden of IBD in Latin America seems to be important, but there is a considerable gap of high-quality evidence in the region

From Informal Housing to Housing at Risk, Preliminary Diagnosis of Some Neighborhoods in Quito

In the second half of the twentieth century in Ecuador, collective housing projects undertaken by the state began to emerge, while informal settlements consolidated on the outskirts of the city. The way in which these neighborhoods were consolidated has had an impact on the quality of life of their inhabitants. By allowing them to identify natural, social, and anthropic risks, they have accentuated and conditioned the safety of users, such as hillside location, context, materiality, accessibility, mobility, infrastructure, etc. The research is based on a comparative study of risks in three neighborhoods of Quito, to understand that both the participation of the people and the cooperation of the regulating entity are important for giving rise to housing projects. Based on the method proposed by Livingston and supported by the literature and bibliographic review, we seek to identify the risks that are generated or emphasized in the different stages of housing, highlighting the importance of building an integrated city based on the inhabitants and their way of inhabiting the space. Finally, we seek to understand that in the creation of housing projects, the appropriation of space makes it possible to turn a neighborhood into a community that reflects the diverse way of living of the users. Keywords: citizen participation, social housing, informal settlements, Quito. Resumen En la segunda mitad del siglo XX en Ecuador empezaron a surgir proyectos de vivienda colectiva emprendidos por el estado central, en paralelo en la periferia de la ciudad se consolidaron asentamientos informales. La forma en la que se consolidaron estos barrios ha tenido un impacto en la calidad de vida de sus habitantes; esto ha permitido identificar riesgos naturales, sociales y antrópicos, los mismos que se han acentuado y condicionan la seguridad de los usuarios, tales como ubicación sobre laderas, contexto, materialidad, accesibilidad, movilidad, infraestructura, etc. La investigación se basa en un estudio comparativo sobre riesgos presentes en tres barrios de Quito, con el fin de entender que tanto la participación de las personas como la cooperación de la entidad reguladora, son importantes al momento de dar lugar a proyectos de vivienda. Partiendo del método propuesto por Livingston y apoyado en la revisión literaria y bibliográfica, se busca identificar los riesgos que se generan o enfatizan en las diferentes etapas de la vivienda, resaltando la importancia de construir una ciudad integrada que tiene como base a los habitantes y su forma de habitar el espacio. Finalmente, se busca entender que en la creación de proyectos habitacionales la apropiación del espacio permite convertir a un barrio en una comunidad que refleja la forma diversa de habitar de los usuarios. Palabras Clave: Participación Ciudadana, Vivienda Social, Asentamientos Informales, Quito