Importance of tetrahedral coordination for high-valent transition metal oxides: YCrO4_4 as a model system

We have investigated the electronic structure of the high oxidation state material YCrO$_4$ within the framework of the Zaanen-Sawatzky-Allen phase diagram. While Cr$^{4+}$-based compounds like SrCrO$_3$/CaCrO$_3$ and CrO$_2$ can be classified as small-gap or metallic negative-charge-transfer systems, we find using photoelectron spectroscopy that YCrO$_4$ is a robust insulator despite the fact that its Cr ions have an even higher formal valence state of 5+. We reveal using band structure calculations that the tetrahedral coordination of the Cr$^{5+}$ ions in YCrO$_4$ plays a decisive role, namely to diminish the bonding of the Cr $3d$ states with the top of the O $2p$ valence band. This finding not only explains why the charge-transfer energy remains effectively positive and the material stable, but also opens up a new route to create doped carriers with symmetries different from those of other transition-metal ions.Comment: 6 pages, 6 figure

Inhomogeneous electronic structure probed by spin-echo experiments in the electron doped high-Tc superconductor Pr_{1.85}Ce_{0.15}CuO_{4-y}

63Cu nuclear magnetic resonance (NMR) spin-echo decay rate (T_2^{-1}) measurements are reported for the normal and superconducting states of a single crystal of Pr_{1.85}Ce_{0.15}CuO_{4-y} (PCCO) in a magnetic field B_0=9T over the temperature range 2K<T<200K. The spin-echo decay rate is temperature-dependent for T<55K, and has a substantial dependence on the radio frequency (rf) pulse parameters below T~25K. This dependence indicates that T_2^{-1} is strongly effected by a local magnetic field distribution that can be modified by the rf pulses, including ones that are not at the nuclear Larmor frequency. The low-temperature results are consistent with the formation of a static inhomogeneous electronic structure that couples to the rf fields of the pulses.Comment: 4 pages, 4 figure

Multiple colonization and dispersal events hide the early origin and induce a lack of genetic structure of the moss Bryum argenteum in Antarctica.

The dispersal routes of taxa with transoceanic disjunctions remain poorly understood, with the potential roles of Antarctica not yet demonstrated. Mosses are suitable organisms to test direct intra‐Antarctic dispersal, as major component of the extant Antarctic flora, with the cosmopolitan moss Bryum argenteum as ideal target species. We analyzed the genetic structure of B. argenteum to provide an evolutionary time frame for its radiation and shed light into its historical biogeography in the Antarctic region. We tested two alternative scenarios: (a) intra‐Antarctic panmixia and (b) intra‐Antarctic genetic differentiation. Furthermore, we tested for evidence of the existence of specific intra‐Antarctic dispersal routes. Sixty‐seven new samples (40 collected in Antarctica) were sequenced for ITS nrDNA and rps4 cpDNA regions, and phylogenetic trees of B. argenteum were constructed, with a focus on its Southern Hemisphere. Combining our new nrDNA dataset with previously published datasets, we estimated time‐calibrated phylogenies based on two different substitution rates (derived from angiosperms and bryophytes) along with ancestral area estimations. Minimum spanning network and pairwise genetic distances were also calculated. B. argenteum was potentially distributed across Africa and Antarctica soon after its origin. Its earliest intra‐Antarctic dispersal and diversification occurred during a warming period in the Pliocene. On the same timescale, a radiation took place involving a dispersal event from Antarctica to the sub‐Antarctic islands. A more recent event of dispersal and diversification within Antarctica occurred during a warm period in the Pleistocene, creating favorable conditions also for its colonization outside the Antarctic continent worldwide. We provide evidence supporting the hypothesis that contemporary populations of B. argenteum in Antarctica integrate a history of both multiple long‐range dispersal events and local persistence combined with in situ diversification. Our data support the hypothesis that B. argenteum has been characterized by strong connectivity within Antarctica, suggesting the existence of intra‐Antarctic dispersal routes

Recent Star Formation in Sextans A

We investigate the relationship between the spatial distributions of stellar populations and of neutral and ionized gas in the Local Group dwarf irregular galaxy Sextans A. This galaxy is currently experiencing a burst of localized star formation, the trigger of which is unknown. We have resolved various populations of stars via deep UBV(RI)_C imaging over an area with diameter \sim 5.'3. We have compared our photometry with theoretical isochrones appropriate for Sextans A, in order to determine the ages of these populations. We have mapped out the history of star formation, most accurately for times \lesssim 100 Myr. We find that star formation in Sextans A is correlated both in time and space, especially for the most recent (\lesssim 12 Myr) times. The youngest stars in the galaxy are forming primarily along the inner edge of the large H I shell. Somewhat older populations, \lesssim 50 Myr, are found inward of the youngest stars. Progressively older star formation, from \sim 50--100 Myr, appears to have some spatially coherent structure and is more centrally concentrated. The oldest stars we can accurately sample appear to have approximately a uniform spatial distribution, which extends beyond a surface brightness of \mu_B \simeq 25.9 mag arcsec^{-2} (or, a radius r \simeq 2.'3$). Although other processes are also possible, our data provides support for a mechanism of supernova-driven expansion of the neutral gas, resulting in cold gas pileup and compression along the H I shell and sequential star formation in recent times.Comment: 64 pages, 22 figures, to appear in A

Estudio del efecto relajante de la fibra lisa en íleo aislado de rata, inducido por derivados terpénicos

Presentamos el estudio de la actividad relajante de la fribra lisa por parte de algunos derivados terpénicos: Terpinenol-4, alfa-Pineno, Borneol y Canfeno, sobre la contracción del ileo. aislado de rata inducida con dósis crecientes de Acetil-colina y CaCl2 en un medio libre de calcio y previa despolarización del ileo con potasio. Los resultados obtenidos indican que el Terpinenol-4 a 1O-8 M y el alfa-Pineno a 1O-5 M poseen actividad relajante del ileo "in vitro" a través de un mecanismo de acción no mediado por receptores muscarínicos (antagonismo no competitivo frente a la Acetil-colina, dósis-dependiente) y muy probablemente relacionado con un antagonismo frente al Calcio, Terpinenol4 a 1O-5 M y alfa-Pineno 10-4 M, respectivamente

Estudio del efecto relajante de la fibra lisa en íleo aislado de rata, inducido por derivados terpénicos

Presentamos el estudio de la actividad relajante de la fribra lisa por parte de algunos derivados terpénicos: Terpinenol-4, alfa-Pineno, Borneol y Canfeno, sobre la contracción del ileo. aislado de rata inducida con dósis crecientes de Acetil-colina y CaCl2 en un medio libre de calcio y previa despolarización del ileo con potasio. Los resultados obtenidos indican que el Terpinenol-4 a 1O-8 M y el alfa-Pineno a 1O-5 M poseen actividad relajante del ileo "in vitro" a través de un mecanismo de acción no mediado por receptores muscarínicos (antagonismo no competitivo frente a la Acetil-colina, dósis-dependiente) y muy probablemente relacionado con un antagonismo frente al Calcio, Terpinenol4 a 1O-5 M y alfa-Pineno 10-4 M, respectivamente.A study on the relaxing activity of sorne terpenic derivates (TerpinenoI4, alpha-Pinene, Borneol y Canphene) over smooth muscle, has been performed. Contraction rat isolated ileus was induced by increasing doses of either Acetylcholine or Ca 2+ in a calcium free mediun previous despolarization by potassium. Both Terpinenol4 (lO-8M) and alpha-Pinene (lO-5M) showed "in vitro" relaxing activity of ileus through a muscatinic receptors non-mediated mechanism of action (non-competitive antagonism with Acetylcholine dose-depent). Probably this relaxing action is. attained by a antagonism between Terpinenol4 and alpha-Pinene with calcium

Influence of lower-limb muscle power-related variables on the ippon-seoi-nage of elite judokas

This study investigated the influence of the lower-limb extension mechanical variables (strength variables) on the ippon-seoi-nage kinematic variables (technical variables) in elite judokas. Additionally, we studied the effect of performing ippon-seoi-nage with lower-limb flexion-extension action vs. without it, on the technical and strength variables, as well as on their relationship. Twenty-four male elite judokas were classified in two groups depending on the type of ippon-seoi-nage performed, i.e., with lower-limb flexion-extension action or without it. Mechanical outputs from an incremental loaded countermovement jump test were assessed, as well as kinematic variables transferred to the uke (person who is thrown) during an ippon-seoi-nage technique test. The strength parameters did not positively correlate with the technical ones, showing no transference between the variables studied. Furthermore, the judokas that performed the ippon-seoi-nage with lower-limb flexion-extension action presented lower times in the execution of the technique than the group that did not perform this action. Therefore, the transference from strength parameters to the performance of ippon-seoi-nage is not yet explained, even when considering different technical styles.This work was supported by the Spanish Ministry of Economy, Industry and Competitiveness under Grant DEP2015-64350-P MINECO/FEDER and FPI pre-doctoral grant under Grant BES-2016-078035 awarded to one of the authors

Estudio experimental del efecto relajante del etanol sobre la fibra lisa

We study the relaxing effect of ethanol on smooth muscle, refered to the contraction of rat isolated ileum induced by increasing doses of acetylcholine and calcium chloride in a calcium free medium after depolarising ileum with potassium. The results obtaines show that ethanol has relaxing activity on the ileum "in vitro". The mechanism of this effect seems not to be mediated through muscarinic receptors (acetylcholine) but very probably related to an antagonism towards calcium.Estudiamos el efecto relajante del Etanol sobre la contracción del ileo aislado de rata inducida con dósis crecientes de acetil-colina y Cloruro cálcico en un medio libre de calcio y previa despolarización del ileo con potasio. Los resultados obtenidos indican que el Etanol posee actividad relajante del ileo "in vitro" a través de un mecanismo de acción no mediado por receptores muscarínicos (Acetil-colina) y muy probablemente relacionado con un antagonismo frente al calcio

Warp or lag? The ionized and neutral hydrogen gas in the edge-on dwarf galaxy UGC 1281

The properties of gas in the halos of galaxies constrain global models of the interstellar medium. Kinematical information is of particular interest since it is a clue to the origin of the gas. Until now mostly massive galaxies have been investigated for their halo properties. Here we report on deep HI and H{\alpha} observations of the edge-on dwarf galaxy UGC 1281 in order to determine the existence of extra-planar gas and the kinematics of this galaxy. This is the first time a dwarf galaxy is investigated for its gaseous halo characteristics. We have obtained H{\alpha} integral field spectroscopy using PPAK at Calar Alto and deep HI observations with the WSRT of this edge-on dwarf galaxy. These observations are compared to 3D models in order to determine the distribution of HI in the galaxy. We find that UGC 1281 has H{\alpha} emission up to 25"(655 pc) in projection above the plane and in general a low H{\alpha} flux. Compared to other dwarf galaxies UGC 1281 is a normal dwarf galaxy with a slowly rising rotation curve that flattens off at 60 km/s and a central depression in its HI distribution. Its HI extends 70" (1.8 kpc) in projection from the plane. This gas can be explained by either a warp partially in the line-of-sight warp or a purely edge-on warp with rotational velocities that decline with a vertical gradient of 10.6 \pm 3.7 km/s/kpc. The line-of-sight warp model is the preferred model as it is conceptually simpler. In either model the warp starts well within the optical radius.Comment: Accepted for publication in MNRAS. 16 pages, 14 figure