Organic beekeeping in Mexico

Mexico is often described as a cornucopia, a land with high diversity in ecosystems, crops, fauna and flora. These are superb preconditions for organic honey production. Already the pre-hispanic Maya cultures produced honey from the native stingless bee (Meliponini) before the Spanish introduced European honey bee (Apis mellifera L). The main beekeeping product in Mexico is honey. Mexico ranks sixth in the world in honey production (57,000 t) and third as an exporter (25,000 t)

Thermal Excitation of Broadband and Long-range Surface Waves on SiO 2 Submicron Films

We detect thermally excited surfaces waves on a submicron SiO 2 layer, including Zenneck and guided modes in addition to Surface Phonon Polaritons. The measurements show the existence of these hybrid thermal-electromagnetic waves from near-(2.7 $\mu$m) to far-(11.2 $\mu$m) infrared. Their propagation distances reach values on the order of the millimeter, several orders of magnitude larger than on semi-infinite systems. These two features, spectral broadness and long range propagation, make these waves good candidates for near-field applications both in optics and thermics due to their dual nature.Comment: Applied Physics Letters, American Institute of Physics, 201

Combined multi-protocols qMRI for thigh muscle analysis: a preliminary study

Quantitative MRI (qMRI) has been shown to be crucial for assessing organ dysfunction in the body. Usually, in qMRI approaches, a few metrics are extracted to distinguish normal and abnormal tissues. In this study, we coupled four MRI protocols (mDIXON T1, T1 and T2 mapping and DTI) to obtain 34 complementary metrics including 20 shape metrics, 2 texture metrics and 12 water diffusivity metrics for thigh muscle analysis. These metrics were calculated on both thighs to detect a pathological difference between a pair of right and left muscles. The method is based on a dimension reduction method and a projection of shape and diffusivity metrics into a three-dimensional linear latent space, along with two texture metrics. 5 healthy individuals (10 thighs, each thigh 7 muscles, i.e., 4 exors and 3 extensors) were scanned to provide the reference scores. The developed pipeline was used to analyse the pair thighs of 4 patients in order to suggest a specific muscle therapy before total knee arthroplasty (TKA) individually for each of the 7 muscles. Preliminary results from the analysis of thigh muscle texture, shape and diffusivity showed that this qMRI protocol can help to suggest a targeted, patient-specific exercise plan to improve muscle recovery after TKA surgery. More healthy and pathological subjects are needed to confirm these encouraging results

Linking dust emission to fundamental properties in galaxies: The low-metallicity picture

In this work, we aim at providing a consistent analysis of the dust properties from metal-poor to metal-rich environments by linking them to fundamental galactic parameters. We consider two samples of galaxies: the Dwarf Galaxy Survey (DGS) and KINGFISH, totalling 109 galaxies, spanning almost 2 dex in metallicity. We collect infrared (IR) to submillimetre (submm) data for both samples and present the complete data set for the DGS sample. We model the observed spectral energy distributions (SED) with a physically-motivated dust model to access the dust properties. Using a different SED model (modified blackbody), dust composition (amorphous carbon), or wavelength coverage at submm wavelengths results in differences in the dust mass estimate of a factor two to three, showing that this parameter is subject to non-negligible systematic modelling uncertainties. For eight galaxies in our sample, we find a rather small excess at 500 microns (< 1.5 sigma). We find that the dust SED of low-metallicity galaxies is broader and peaks at shorter wavelengths compared to more metal-rich systems, a sign of a clumpier medium in dwarf galaxies. The PAH mass fraction and the dust temperature distribution are found to be driven mostly by the specific star-formation rate, SSFR, with secondary effects from metallicity. The correlations between metallicity and dust mass or total-IR luminosity are direct consequences of the stellar mass-metallicity relation. The dust-to-stellar mass ratios of metal-rich sources follow the well-studied trend of decreasing ratio for decreasing SSFR. The relation is more complex for highly star-forming low-metallicity galaxies and depends on the chemical evolutionary stage of the source (i.e., gas-to-dust mass ratio). Dust growth processes in the ISM play a key role in the dust mass build-up with respect to the stellar content at high SSFR and low metallicity. (abridged)Comment: 44 pages (20 pages main body plus 5 Appendices), 11 figures, 9 tables, accepted for publication in A&

Gas-to-Dust mass ratios in local galaxies over a 2 dex metallicity range

This paper analyses the behaviour of the gas-to-dust mass ratio (G/D) of local Universe galaxies over a large metallicity range. We combine three samples: the Dwarf Galaxy Survey, the KINGFISH survey and a subsample from Galametz et al. (2011) totalling 126 galaxies, covering a 2 dex metallicity range, with 30% of the sample with 12+log(O/H) < 8.0. The dust masses are homogeneously determined with a semi-empirical dust model, including submm constraints. The atomic and molecular gas masses are compiled from the literature. Two XCO are used to estimate molecular gas masses: the Galactic XCO, and a XCO depending on the metallicity (as Z^{-2}). Correlations with morphological types, stellar masses, star formation rates and specific star formation rates are discussed. The trend between G/D and metallicity is empirically modelled using power-laws (slope of -1 and free) and a broken power-law. We compare the evolution of the G/D with predictions from chemical evolution models. We find that out of the five tested galactic parameters, metallicity is the galactic property driving the observed G/D. The G/D versus metallicity relation cannot be represented by a power-law with a slope of -1 over the whole metallicity range. The observed trend is steeper for metallicities lower than ~ 8.0. A large scatter is observed in the G/D for a given metallicity, with a dispersion of 0.37 dex in metallicity bins of ~0.1 dex. The broken power-law reproduces best the observed G/D and provides estimates of the G/D that are accurate to a factor of 1.6. The good agreement of the G/D and its scatter with the three tested chemical evolution models shows that the scatter is intrinsic to galactic properties, reflecting the different star formation histories, dust destruction efficiencies, dust grain size distributions and chemical compositions across the sample. (abriged)Comment: 23 pages, 12 figures, accepted in Astronomy & Astrophysic

Interaction induced delocalisation for two particles in a periodic potential

We consider two interacting particles evolving in a one-dimensional periodic structure embedded in a magnetic field. We show that the strong localization induced by the magnetic field for particular values of the flux per unit cell is destroyed as soon as the particles interact. We study the spectral and the dynamical aspects of this transition.Comment: 4 pages, 5 EPS figures, minor misprints correcte

Quantum dynamics in high codimension tilings: from quasiperiodicity to disorder

We analyze the spreading of wavepackets in two-dimensional quasiperiodic and random tilings as a function of their codimension, i.e. of their topological complexity. In the quasiperiodic case, we show that the diffusion exponent that characterizes the propagation decreases when the codimension increases and goes to 1/2 in the high codimension limit. By constrast, the exponent for the random tilings is independent of their codimension and also equals 1/2. This shows that, in high codimension, the quasiperiodicity is irrelevant and that the topological disorder leads in every case, to a diffusive regime, at least in the time scale investigated here.Comment: 4 pages, 5 EPS figure