The Physics of UHECRs: Spectra, Composition and the Transition Galactic-Extragalactic

We review the experimental evidences about flux and mass composition of ultra high energy cosmic rays in connection with theoretical scenarios concerning astrophysical sources. In this context, we also address the discussion about the expected transition between cosmic rays produced inside the Galaxy and those coming from the intergalactic space.Comment: 6 pages, 10 figures, invited talk given at the "2016 International Conference on Ultra-High Energy Cosmic Rays (UHECR2016)", Kyoto (Japan), 11-14 October 2016, version accepted for publication on JPS Conference Proceeding

A new early Pliocene murine rodent from the Iberian Peninsula and its biostratigraphic implications

In the last years, a murine identified as Paraethomys aff. abaigari has been repeatedly recognized in several early Pliocene localities of the Iberian Peninsula. We have revised these occurrences, as well as other samples of similar morphology, and propose that all these records correspond to a new species. We diagnose Paraethomys baeticus sp. nov. based on a large sample from the early Ruscinian site of Baza-1 (Guadix-Baza Basin, Spain). It is a medium-sized representative of the genus, with relatively well-developed longitudinal connections both in upper and lower molars, but incomplete stephanodonty. M1 displays high tubercles t6-t9 and low t4-t8 connections. M1 and, to a lesser extent, M2 have posterior spurs on t1 and t3. The t9 and t12 are absent in M2. In m1, a round islet of enamel between the anteroconid and the protoconid-metaconid is regularly observed, as well as a general lack of medial anteroconid, moderate labial cingulum with large posterior accessory cuspid, and longitudinal spur. The new species differs from other European representatives of the genus Paraethomys mainly in its size, which is intermediate between that of the small-sized Paraethomys meini and the large-sized Paraethomys abaigari. In addition, both the size and relative width are smaller than those of Paraethomys jaegeri. The frequency of posterior spurs on t1 and t3 of M1 and M2 is higher than that of P. meini and lower than that of P. jaegeri. The new species here described represents a key biochronological and biostratigraphic marker, since it is restricted to levels of late early Ruscinian age. Thus, this species is useful for establishing divisions within the early Ruscinian, and becomes a characteristic taxon for the early Pliocene in the terrestrial record of the Iberian Peninsula. Magnetobiostratigraphic correlations suggest a chronological range for P. baeticus sp. nov. between ca. 4.6 and 4.3 Ma.Fil: Piñero García, Pedro. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Zoología de Vertebrados. Sección de Mastozoología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Verzi, Diego Hector. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Zoología de Vertebrados. Sección de Mastozoología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentin

Morphological diversity of the humerus of the South American subterranean rodent Ctenomys (Rodentia, Ctenomyidae)

Humeral variation associated with digging ability in the subterranean rodent Ctenomys was analyzed through 6 functionally significant indexes. The humerus of some extinct and living species was slightly more specialized than that of fossorial octodontoids †Actenomys and Octodon, whereas it was highly specialized in some living species. The constant occurrence of greater epicondyles suggests a hierarchical pattern in the acquisition of scratch-digging specializations. A possible relationship between humeral morphological diversity and environments is preliminarily discussed.Facultad de Ciencias Naturales y Muse

Morphological diversity of the humerus of the South American subterranean rodent Ctenomys (Rodentia, Ctenomyidae)

Humeral variation associated with digging ability in the subterranean rodent Ctenomys was analyzed through 6 functionally significant indexes. The humerus of some extinct and living species was slightly more specialized than that of fossorial octodontoids †Actenomys and Octodon, whereas it was highly specialized in some living species. The constant occurrence of greater epicondyles suggests a hierarchical pattern in the acquisition of scratch-digging specializations. A possible relationship between humeral morphological diversity and environments is preliminarily discussed.Facultad de Ciencias Naturales y Muse

Neurotransmitter modulation of extracellular H+ fluxes from isolated retinal horizontal cells of the skate

Self-referencing H+-selective microelectrodes were used to measure extracellular H+ fluxes from horizontal cells isolated from the skate retina. A standing H+ flux was detected from quiescent cells, indicating a higher concentration of free hydrogen ions near the extracellular surface of the cell as compared to the surrounding solution. The standing H+ flux was reduced by removal of extracellular sodium or application of 5-(N-ethyl-N-isopropyl) amiloride (EIPA), suggesting activity of a Na+–H+ exchanger. Glutamate decreased H+ flux, lowering the concentration of free hydrogen ions around the cell. AMPA/kainate receptor agonists mimicked the response, and the AMPA/kainate receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) eliminated the effects of glutamate and kainate. Metabotropic glutamate agonists were without effect. Glutamate-induced alterations in H+ flux required extracellular calcium, and were abolished when cells were bathed in an alkaline Ringer solution. Increasing intracellular calcium by photolysis of the caged calcium compound NP-EGTA also altered extracellular H+ flux. Immunocytochemical localization of the plasmalemma Ca2+–H+-ATPase (PMCA pump) revealed intense labelling within the outer plexiform layer and on isolated horizontal cells. Our results suggest that glutamate modulation of H+ flux arises from calcium entry into cells with subsequent activation of the plasmalemma Ca2+–H+-ATPase. These neurotransmitter-induced changes in extracellular pH have the potential to play a modulatory role in synaptic processing in the outer retina. However, our findings argue against the hypothesis that hydrogen ions released by horizontal cells normally act as the inhibitory feedback neurotransmitter onto photoreceptor synaptic terminals to create the surround portion of the centre-surround receptive fields of retinal neuron