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We analyze a sample of $z$-dropout galaxies in the CANDELS GOODS South and UDS fields that have been targeted by a dedicated spectroscopic campaign aimed at detecting their Ly$\alpha$ line. Deep IRAC observations at 3.6 and 4.5 μm are used to determine the strength of optical emission lines affecting these bands at $z$ ~ 6.5-6.9 in order to (1) investigate possible physical differences between Ly$\alpha$ emitting and non-emitting sources; (2) constrain the escape fraction of ionizing photons; and (3) provide an estimate of the specific star formation rate at high redshifts. We find evidence of strong [O III]+Hβ emission in the average (stacked) SEDs of galaxies both with and without Ly$\alpha$ emission. The blue IRAC [3.6]-[4.5] color of the stack with detected Ly$\alpha$ line can be converted into a rest-frame equivalent width EW([O III]+Hβ) = 1500$^{+530}_{-440}$Å assuming a flat intrinsic stellar continuum. This strong optical line emission enables a first estimate of $f_{esc} \lesssim$ 20% on the escape fraction of ionizing photons from Ly$\alpha$ detected objects. The objects with no Ly$\alpha$ line show less extreme EW([O III]+Hβ) = Å, suggesting different physical conditions of the H II regions with respect to Ly$\alpha$-emitting ones, or a larger $f_{esc}$. The latter case is consistent with a combined evolution of $f_{esc}$ and the neutral hydrogen fraction as an explanation of the lack of bright Ly$\alpha$ emission at $z$ > 6. A lower limit on the specific star formation rate, SSFR > 9.1 Gyr$^{-1}$ for $M_{star}$ = 2 $\times$ 10$^9$ $M_\odot$ galaxies at these redshifts can be derived from the spectroscopically confirmed sample., K.C. acknowledges funding from the European Research Council through the award of the Consolidator Grant ID 681627-BUILDUP. The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007–2013) under grant agreement n 312725. This work is based on data obtained with ESO Programmes 084.A-0951, 085.A-0844, 086.A-0968, 088.A-1013, 088.A-0192, and 190.A-0685.

Hybrid nanoparticles (NPs) are emerging as an important family of multifunctional nanoscale materials. Due to its unique properties cyclodextrins (CDs) present the possibility to be employed in nanostructured devices for multiple applications. Therefore the study of hybrids NPs containing CDs, metal nanoparticles and an organic molecular guest is promising for applications in separation science, sensing, optics, catalysis and medical therapy. To investigate the hybrid nanoparticles properties in light of technological and medical science interfaces we chose tramadol hydrochloride as the model molecular guest. Using 2D 1H NMR and FTIR spectroscopies and ESI-MS we studied the topology and host-guest stoichiometry of inclusion compound between 2-hydroxypropyl-α-cyclodextrin and tramadol. These techniques confirmed that the inclusion compounds present 1:1 stoichiometry with the tramadol aromatic moiety inserted in the CD cavity and the amine part interacting with the CD superficial OHs. Performing capillary electrophoresis experiments, the stability constants of inclusion compounds were obtained and showed that the increase of temperature during the synthesis of these NPs can decrease their stabilities. Precipitated palladium nanoparticles were determined to have 80-200 nm of size distribution and the incorporation of tramadol was evidenced by additional 1H NMR experiments.

Deep observations are revealing a growing number of young galaxies in the first billion years of cosmic time. Compared to typical galaxies at later times, they show more extreme emission-line properties, higher star formation rates, lower masses, and smaller sizes. However, their faintness precludes studies of their chemical abundances and ionization conditions, strongly limiting our understanding of the physics driving early galaxy build-up and metal enrichment. Here we study a rare population of ultraviolet-selected, low-luminosity galaxies at redshift 2.4 < z < 3.5 that exhibit all the rest-frame properties expected from primeval galaxies. These low-mass, highly compact systems are rapidly forming galaxies able to double their stellar mass in only a few tens of millions of years. They are characterized by very blue ultraviolet spectra with weak absorption features and bright nebular emission lines, which imply hard radiation fields from young hot massive stars. Their highly ionized gas phase has strongly sub-solar carbon and oxygen abundances, with metallicities more than a factor of two lower than that found in typical galaxies of similar mass and star formation rate at z≤2.5. These young galaxies reveal an early and short stage in the assembly of their galactic structures and their chemical evolution, a vigorous phase that is likely to be dominated by the effects of gas-rich mergers, accretion of metal-poor gas and strong outflows.