Constraining the time evolution of dark energy, curvature and neutrino properties with cosmic chronometers

We use the latest compilation of observational H(z) measurements obtained with cosmic chronometers in the redshift range $0<z<2$ to place constraints on cosmological parameters. We consider the sample alone and in combination with other state-of-the art cosmological probes: CMB data from the latest Planck 2015 release, the most recent estimate of the Hubble constant $H_{0}$, a compilation of recent BAO data, and the latest SNe sample. Since cosmic chronometers are independent of the assumed cosmological model, we are able to provide constraints on the parameters that govern the expansion history of the Universe in a way that can be used to test cosmological models. We show that the H(z) measurements obtained with cosmic chronometer from the BOSS survey provide enough constraining power in combination with CMB data to constrain the time evolution of dark energy, yielding constraints competitive with those obtained using SNe and/or BAO. From late-Universe probes alone we find that $w_0=-0.9\pm0.18$ and $w_a=-0.5\pm1.7$, and when combining also CMB data we obtain $w_0=-0.98\pm0.11$and $w_a=-0.30\pm0.4$. These new constraints imply that nearly all quintessence models are disfavoured, only phantom models or a pure cosmological constant being allowed. For the curvature we find $\Omega_k=0.003\pm0.003$, including CMB data. Cosmic chronometers data are important also to constrain neutrino properties by breaking or reducing degeneracies with other parameters. We find that $N_{eff}=3.17\pm0.15$, thus excluding the possibility of an extra (sterile) neutrino at more than $5\sigma$, and put competitive limits on the sum of neutrino masses, $\Sigma m_{\nu}< 0.27$ eV at 95% confidence level. Finally, we constrain the redshift evolution of dark energy, and find w(z) consistent with the $\Lambda$CDM model at the 40% level over the entire redshift range $0<z<2$. [abridged]Comment: 19 pages, 9 figures, 6 tables, submitted to JCAP. The cosmic chronometers data used in this analysis can be downloaded at http://www.physics-astronomy.unibo.it/en/research/areas/astrophysics/cosmology-with-cosmic-chronometer

The Effectiveness of Different Types of Sunscreen against UV Light on Escherichia coli

Ultraviolet (UV) light from the sun damages the DNA of our skin cells which could potentially lead to development of skin cancer (Mahroos, Yaar, Phillps, Bhawan, & Gilchrest, 2002). Sunscreen is used to protect our skin from this damage. The two most commonly used sunscreens are physical and chemical sunscreens. Physical sunscreens, also referred to as mineral sunscreens, work by sitting on top of your skin and reflecting UV light, whereas chemical sunscreens penetrate the skin and absorb UV light. There are many different brands of these sunscreens in the market. We hypothesized that the physical sunscreens would serve as better protection than the chemical sunscreens due to their high cost and natural ingredients. Brands that we used that represent physical sunscreens were Badger and Goddess Garden. Brands of chemical sunscreens were Aveeno, Hawaiian Tropic, and Up & Up Target Sports. All the sunscreens were creamy and had an SPF of 30. On average, the physical sunscreens were two times more expensive than chemical sunscreens. To test our hypothesis, we used the bacterium Escherichia coli (E. coli) as a model organism and exposed it to UV light while using the various sunscreens for protection. We then counted the survival rate of the E.coli colonies that were exposed. Our results demonstrated that there was no statistical significance in sunscreen protection. We concluded that physical sunscreens are not worth their price

The effective Lagrangian of dark energy from observations

Using observational data on the expansion rate of the universe (H(z)) we constrain the effective Lagrangian of the current accelerated expansion. Our results show that the effective potential is consistent with being flat i.e., a cosmological constant; it is also consistent with the field moving along an almost flat potential like a pseudo-Goldstone boson. We show that the potential of dark energy does not deviate from a constant at more than 6% over the redshift range 0 < z < 1. The data can be described by just a constant term in the Lagrangian and do not require any extra parameters; therefore there is no evidence for augmenting the number of parameters of the LCDM paradigm. We also find that the data justify the effective theory approach to describe accelerated expansion and that the allowed parameters range satisfy the expected hierarchy. Future data, both from cosmic chronometers and baryonic acoustic oscillations, that can measure H(z) at the % level, could greatly improve constraints on the flatness of the potential or shed some light on possible mechanisms driving the accelerated expansion. Besides the above result, it is shown that the effective Lagrangian of accelerated expansion can be constrained from cosmological observations in a model-independent way and that direct measurements of the expansion rate H(z) are most useful to do so.Comment: 9 pages, 3 figures, JCAP submitted. This paper presents a reconstruction of the dark energy potential. It is a companion to Moresco et al. 2012a, which presents new H(z) results and Moresco et al. 2012b, which provides cosmological parameter constraint

Fortalecer el proceso de aprendizaje en el área de tecnología en estudiantes de 5 grado del IEP campo hermoso mediante el desarrollo de un aula virtual de aprendizaje de energía eléctrica.

El objetivo principal de esta investigación fue fortalecer el proceso de aprendizaje en el área de tecnología en estudiantes de 5 grado del IEP Campo hermoso, mediante el estudio de la energía eléctrica y su relación con la vida cotidiana. Tomando una muestra de estudiantes se aplicó una encuesta sobre conceptos básicos de energía eléctrica en la que se detectó el poco conocimiento que tenían en el tema, gracias a esto se propuso la creación de un AVA de energía eléctrica como una alternativa novedosa para apropiar conocimientos en el tema. En el desarrollo de la prueba piloto los resultados mostraron que los estudiantes mejoraron su proceso de aprendizaje de conceptos básicos de energía eléctrica, apropiando el uso racional de nuestros recursos energéticos, y comprendiendo la responsabilidad que tiene el hombre en el daño ambiental por la generación y uso de la energía eléctrica, manifestando la importancia de usar de forma eficiente la energía como contribución al cuidado ambiental

The influence of BMSs on the characterization and modeling of series and parallel Li-ion packs

This work analyzes the effects of a BMS (battery management system) on the characterization and modeling of series and parallel connections of Li-ion cell packs. The Li-ion pack studied consists of four series modules connected in parallel. This pack has been characterized by means of charge, discharge and frequency tests. As a result of these tests, series and parallel influence on battery parameters have been determined. A model considering the effects of a BMS is established and compared with a model based on a single-cell approach. Experimental validations show that the single cell based approach gives poor results in comparison with a model that considers BMS effects

In vitro models for non-alcoholic fatty liver disease: Emerging platforms and their applications

Non-alcoholic fatty liver disease (NAFLD) represents a global healthcare challenge, affecting 1 in 4 adults, and death rates are predicted to rise inexorably. The progressive form of NAFLD, non-alcoholic steatohepatitis (NASH), can lead to fibrosis, cirrhosis, and hepatocellular carcinoma. However, no medical treatments are licensed for NAFLD-NASH. Identifying efficacious therapies has been hindered by the complexity of disease pathogenesis, a paucity of predictive preclinical models and inadequate validation of pharmacological targets in humans. The development of clinically relevant in vitro models of the disease will pave the way to overcome these challenges. Currently, the combined application of emerging technologies (e.g., organ-on-a-chip/microphysiological systems) and control engineering approaches promises to unravel NAFLD biology and deliver tractable treatment candidates. In this review, we will describe advances in preclinical models for NAFLD-NASH, the recent introduction of novel technologies in this space, and their importance for drug discovery endeavors in the future

Fortalecer el proceso de aprendizaje en el área de tecnología en estudiantes de 5 grado del IEP campo hermoso mediante el desarrollo de un aula virtual de aprendizaje de energía eléctrica.

El objetivo principal de esta investigación fue fortalecer el proceso de aprendizaje en el área de tecnología en estudiantes de 5 grado del IEP Campo hermoso, mediante el estudio de la energía eléctrica y su relación con la vida cotidiana. Tomando una muestra de estudiantes se aplicó una encuesta sobre conceptos básicos de energía eléctrica en la que se detectó el poco conocimiento que tenían en el tema, gracias a esto se propuso la creación de un AVA de energía eléctrica como una alternativa novedosa para apropiar conocimientos en el tema. En el desarrollo de la prueba piloto los resultados mostraron que los estudiantes mejoraron su proceso de aprendizaje de conceptos básicos de energía eléctrica, apropiando el uso racional de nuestros recursos energéticos, y comprendiendo la responsabilidad que tiene el hombre en el daño ambiental por la generación y uso de la energía eléctrica, manifestando la importancia de usar de forma eficiente la energía como contribución al cuidado ambiental

Setting the Stage for Cosmic Chronometers. I. Assessing the Impact of Young Stellar Populations on Hubble Parameter Measurements

The expansion history of the Universe can be constrained in a cosmology-independent way by measuring the differential age evolution of cosmic chronometers. This yields a measurement of the Hubble parameter $H(z)$ as a function of redshift. The most reliable cosmic chronometers known so far are extremely massive and passively evolving galaxies. Age-dating these galaxies is, however, a difficult task, and even a small contribution of an underlying young stellar population could, in principle, affect the age estimate and its cosmological interpretation. We present several spectral indicators to detect, quantify and constrain such contamination in old galaxies, and study how their combination can be used to maximize the purity of cosmic chronometers selection. In particular, we analyze the CaII H/K ratio, the presence (or absence) of H$\alpha$ and [OII] emission lines, higher order Balmer absorption lines, and UV flux; each indicator is especially sensitive to a particular age range, allowing us to detect young components ranging between 10 Myr and 1 Gyr. The combination of these indicators minimizes the contamination to a level below 1% in the case of ideal data. More importantly, it offers a way to control the systematic error on $H(z)$ as a function of the contamination by young stellar populations. We show that for our previous measurements of the Hubble parameter, the possible bias induced by the presence of a younger component is well below the current errors. We envision that these indicators will be instrumental in paving the road for a robust and reliable dating of the old population and its cosmological interpretation.Comment: 18 pages, 8 figures. Accepted for publication in the Astrophysical Journa