Organic Molecules in the Galactic Center. Hot Core Chemistry without Hot Cores

We study the origin of large abundances of complex organic molecules in the Galactic center (GC). We carried out a systematic study of the complex organic molecules CH3OH, C2H5OH, (CH3)2O, HCOOCH3, HCOOH, CH3COOH, H2CO, and CS toward 40 GC molecular clouds. Using the LTE approximation, we derived the physical properties of GC molecular clouds and the abundances of the complex molecules.The CH3OH abundance between clouds varies by nearly two orders of magnitude from 2.4x10^{-8} to 1.1x10^{-6}. The abundance of the other complex organic molecules relative to that of CH3OH is basically independent of the CH3OH abundance, with variations of only a factor 4-8. The abundances of complex organic molecules in the GC are compared with those measured in hot cores and hot corinos, in which these complex molecules are also abundant. We find that both the abundance and the abundance ratios of the complex molecules relative to CH3OH in hot cores are similar to those found in the GC clouds. However, hot corinos show different abundance ratios than observed in hot cores and in GC clouds. The rather constant abundance of all the complex molecules relative to CH3OH suggests that all complex molecules are ejected from grain mantles by shocks. Frequent (similar 10^{5}years) shocks with velocities >6km/s are required to explain the high abundances in gas phase of complex organic molecules in the GC molecular clouds. The rather uniform abundance ratios in the GC clouds and in Galactic hot cores indicate a similar average composition of grain mantles in both kinds of regions. The Sickle and the Thermal Radio Arches, affected by UV radiation, show different relative abundances in the complex organic molecules due to the differentially photodissociation of these molecules.Comment: 18 pages, 10 Postscript figures, uses aa.cls, aa.bst, 10pt.rtx, natbib.sty, revsymb.sty revtex4.cls, aps.rtx and aalongtabl.sty. Accepted in A&A 2006. version 2. relocated figures and tables. Language editor suggestions. added reference

Phase diagram of a polydisperse soft-spheres model for liquids and colloids

The phase diagram of soft spheres with size dispersion has been studied by means of an optimized Monte Carlo algorithm which allows to equilibrate below the kinetic glass transition for all sizes distribution. The system ubiquitously undergoes a first order freezing transition. While for small size dispersion the frozen phase has a crystalline structure, large density inhomogeneities appear in the highly disperse systems. Studying the interplay between the equilibrium phase diagram and the kinetic glass transition, we argue that the experimentally found terminal polydispersity of colloids is a purely kinetic phenomenon.Comment: Version to be published in Physical Review Letter

Separation and fractionation of order and disorder in highly polydisperse systems

Microcanonical Monte Carlo simulations of a polydisperse soft-spheres model for liquids and colloids have been performed for very large polydispersity, in the region where a phase-separation is known to occur when the system (or part of it) solidifies. By studying samples of different sizes, from N=256 to N=864, we focus on the nature of the two distinct coexisting phases. Measurements of crystalline order in particles of different size reveal that the solid phase segregates between a crystalline solid with cubic symmetry and a disordered phase. This phenomenon is termed fractionation.Comment: 8 pages, 5 figure

The central parsecs of M87: jet emission and an elusive accretion disc

We present the first simultaneous spectral energy distribution (SED) of M87 core at a scale of 0.4 arcsec ($\sim 32\, \rm{pc}$) across the electromagnetic spectrum. Two separate, quiescent, and active states are sampled that are characterized by a similar featureless SED of power-law form, and that are thus remarkably different from that of a canonical active galactic nuclei (AGN) or a radiatively inefficient accretion source. We show that the emission from a jet gives an excellent representation of the core of M87 core covering ten orders of magnitude in frequency for both the active and the quiescent phases. The inferred total jet power is, however, one to two orders of magnitude lower than the jet mechanical power reported in the literature. The maximum luminosity of a thin accretion disc allowed by the data yields an accretion rate of $< 6 \times 10^{-5}\, \rm{M_\odot \, yr^{-1}}$, assuming 10% efficiency. This power suffices to explain M87 radiative luminosity at the jet-frame, it is however two to three order of magnitude below that required to account for the jet's kinetic power. The simplest explanation is variability, which requires the core power of M87 to have been two to three orders of magnitude higher in the last 200 yr. Alternatively, an extra source of power may derive from black hole spin. Based on the strict upper limit on the accretion rate, such spin power extraction requires an efficiency an order of magnitude higher than predicted from magnetohydrodynamic simulations, currently in the few hundred per cent range.Comment: 18 pages, 6 figures. Accepted for publication in MNRA

Teaching Style in Physical Education and Changes of Daily Physical Activity after One Academic Year in Adolescents: GEOS Study

Increased Moderate-Vigorous physical activity (MVPA) and reduced sedentary time (ST) are key factors for a healthy lifestyle during childhood and adolescence. Studies have suggested that schools may be effective resources to promote healthy habits (Sallis, McKenzie et al. 2012). Therefore, in PE, is important to assess how teachers use strategies and provide students tools to engage in PA with the purpose of reduce the risk of sedentary behavior and contribute to promotion MVPA habits for a healthy lifestyle (Lonsdale, C. et al., 2013). Many factors may be involved in the successful PE class to promote healthy out-school behaviors, as teaching styles (TS), learning styles, learning time, motivation and so on (Mosston, M. 1966). Regarding TS, there is a lack of knowledge about influence of the teaching style (TS) in the promotion of daily MVPA. It was our aim to observe the differences of total daily PA dimensions between two groups of adolescents who were taught during a whole academic year using reproducing (RK) or producing knowledge (PK) TSs.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Visual attention mechanisms in happiness vs. trustworthiness processing of facial expressions

A happy facial expression makes a person look (more) trustworthy. Do perceptions of happiness and trustworthiness rely on the same face regions and visual attention processes? In an eye-tracking study, eye movements and fixations were recorded while participants judged the un/happiness or the un/trustworthiness of dynamic facial expressions in which the eyes and/or the mouth unfolded from neutral to happy or vice versa. A smiling mouth and happy eyes enhanced perceived happiness and trustworthiness similarly, with a greater contribution of the smile relative to the eyes. This comparable judgement output for happiness and trustworthiness was reached through shared as well as distinct attentional mechanisms: (a) entry times and (b) initial fixation thresholds for each face region were equivalent for both judgements, thereby revealing the same attentional orienting in happiness and trustworthiness processing. However, (c) greater and (d) longer fixation density for the mouth region in the happiness task, and for the eye region in the trustworthiness task, demonstrated different selective attentional engagement. Relatedly, (e) mean fixation duration across face regions was longer in the trustworthiness task, thus showing increased attentional intensity or processing effort

Equilibrium fluid-solid coexistence of hard spheres

We present a tethered Monte Carlo simulation of the crystallization of hard spheres. Our method boosts the traditional umbrella sampling to the point of making practical the study of constrained Gibb's free energies depending on several crystalline order-parameters. We obtain high-accuracy estimates of the fluid-crystal coexistence pressure for up to 2916 particles (enough to accommodate fluid-solid interfaces). We are able to extrapolate to infinite volume the coexistence pressure (p_{co}=11.5727(10) k_B T/\sigma^3) and the interfacial free energy (\gamma_{100}=0.636(11) k_B T/\sigma^2).Comment: 6 pages, 4 pdf figures. Version to be published in PRL. Appendices contain Supplemental Materia

Monte Carlo studies of antiferromagnetic spin models in three dimensions

We study several antiferromagnetic formulations of the O(3) spin model in three dimensions by means of Monte Carlo simulations. We discuss about the vacua properties and analyze the phase transitions. Using Finite Size Scaling analysis we conclude that all phase transitions found are of first orderComment: 4 pages, 2 Postscript figures. Contribution to Lattice '9