2,055 research outputs found
Picolinic and Isonicotinic Acids: A Fourier Transform Microwave Spectroscopy Study
Producción CientíficaThe rotational spectra of laser ablated picolinic and isonicotinic acids have been studied using broadband chirped pulse (CP-FTMW) and narrowband molecular beam (MB-FTMW) Fourier transform microwave spectroscopies. Two conformers of picolinic acid, s-cis-I and s-cis-II, and one conformer of isonicotinic acid have been identified through the analysis of their rotational spectra. The values of the inertial defect and the quadrupole coupling constants obtained for the most stable s-cis-I conformer of picolinic acid, evidence the formation of an O–H···N hydrogen bond between the acid group and the endocyclic N atom. The stabilization provided by this hydrogen bond compensates the destabilization energy due to the adoption of a −COOH trans configuration in this conformer. Its rs structure has been derived from the rotational spectra of several 13C, 15N, and 18O species observed in their natural abundances. Mesomeric effects have been revealed by comparing the experimental values of the 14N nuclear quadrupole coupling constants in the isomeric series of picolinic, isonicotinic, and nicotinic acids.Junta de Castilla y León (programa de apoyo a proyectos de investigación – Ref. VA175U13
Impact of regulation fair disclosure on corporate communications with investors
In this study we report laser ablation–inductively coupled plasma–mass spectrometer U-Pb ages of granitoids from the so-called early granodiorites of the northwest Iberian Variscan belt. The U-Pb results attest to significant magmatic activity in Visean time (ca. 347–337 Ma) that generated a hitherto poorly constrained granitoid suite in the northwest Iberian tract of the western European Variscan belt realm. This early Carboniferous suite (ECS) is mainly composed of peraluminous cold and hot crustal granodiorites and monzogranites with minor associated mafic rocks that attest to minor involvement of mantle melting. Based on the geochronological and geochemical data, we compare the Visean granitoids with younger Variscan granitoids in northwest Iberia and, in view of the tectonothermal scenarios of the Variscan collision in northwest Iberia, propose a model for the genesis of the ECS in northwest Iberia that involves rapid melting upon fast exhumation of the thickened Gondwanan crust in the course of the protracted Variscan collision.This work has been funded by the Spanish Ministry of Economy and Competitiveness under the project ODRE III—Oroclines & Delamination: Relations & Effects (CGL2013-46061-P) and Происхождение, металлогения, климатические эффекты и цикличность Крупных Изверженных Провинций (КИП) (Origin, metallogeny, climatic effects, and cyclical large igneous provinces) (14.Y26.31.0012; Russian Federation) to Gutiérrez-Alonso and López-Carmona and CGL-2016-76438-P to Fernández-Suárez. López-Carmona was also funded by a “Juan de la Cierva” grant (reference FJCI-2014-20740).Peer reviewe
Seguimiento de la evolución de los niveles de salinidad y nitratos en el acuífero superficial de Zafarraya y en fincas de hortícolas al aire libre
La horticultura al aire libre del Llano de Zafarraya es el motor económico de la
comarca. El riego de este sector se sustenta en el sistema acuífero del Polje de Zafarraya y
Sierra Gorda. En estos acuíferos, como consecuencia de la explotación agrícola de la zona,
se viene produciendo desde hace décadas sobreexplotación del recurso, con la consiguiente
salinización y nitrificación. Los objetivos de este trabajo han sido estudiar los niveles de
salinidad y nitratos de las aguas del acuífero de Zafarraya y hacer un seguimiento de la
solución del suelo en explotaciones hortícolas de la zona, para poder realizar
recomendaciones que permitan mejorar la gestión de la fertilización y evitar el aumento de la
contaminación por nitratos. Los niveles de salinidad obtenidos a lo largo del periodo de
estudio han sido estables y no representan problemas para los principales cultivos hortícolas
de la zona. En lo que respecta a la concentración de nitratos, los resultados muestran
niveles excesivos por encima de 300 mg L-1. Estos resultados son consecuencia de la
práctica habitual de aplicaciones excesivas de fertilizantes nitrogenados. La recomendación
inicial sería mantener una concentración de nitratos estable a lo largo del ciclo de cultivo
para evitar acumulaciones en el suelo sobre todo al final del mismo
Star-formation histories of local luminous infrared galaxies
We present the analysis of the integrated spectral energy distribution (SED)
from the ultraviolet (UV) to the far-infrared and H of a sample of 29
local systems and individual galaxies with infrared (IR) luminosities between
10^11 Lsun and 10^11.8 Lsun. We have combined new narrow-band H+[NII]
and broad-band g, r optical imaging taken with the Nordic Optical Telescope
(NOT), with archival GALEX, 2MASS, Spitzer, and Herschel data. The SEDs
(photometry and integrated H flux) have been fitted with a modified
version of the MAGPHYS code using stellar population synthesis models for the
UV-near-IR range and thermal emission models for the IR emission taking into
account the energy balance between the absorbed and re-emitted radiation. From
the SED fits we derive the star-formation histories (SFH) of these galaxies.
For nearly half of them the star-formation rate appears to be approximately
constant during the last few Gyrs. In the other half, the current
star-formation rate seems to be enhanced by a factor of 3-20 with respect to
that occured ~1 Gyr ago. Objects with constant SFH tend to be more massive than
starbursts and they are compatible with the expected properties of a
main-sequence (M-S) galaxy. Likewise, the derived SFHs show that all our
objects were M-S galaxies ~1 Gyr ago with stellar masses between 10^10.1 and
10^11.5 Msun. We also derived from our fits the average extinction (A_v=0.6-3
mag) and the polycyclic aromatic hydrocarbons (PAH) luminosity to L(IR) ratio
(0.03-0.16). We combined the A_v with the total IR and H luminosities
into a diagram which can be used to identify objects with rapidly changing
(increasing or decreasing) SFR during the last 100 Myr.Comment: 16 pages + online material, accepted for publication in A&
Análisis de las adaptaciones inducidas por cuatro semanas de entrenamiento pliométrico
Episodic melting and magmatic recycling along 50 Ma in the Variscan belt linked to the orogenic evolution in NW Iberia
The advent of a large amount of more precise U-Pb age data on Variscan granitoids from NW Iberia in recent years has provided a more focused picture of the magmatic history of the Western European Variscan belt (WEVB). Based on these data, three main pulses of magmatic activity seem to be well established
Antiferromagnetic 4-d O(4) Model
We study the phase diagram of the four dimensional O(4) model with first
(beta1) and second (beta2) neighbor couplings, specially in the beta2 < 0
region, where we find a line of transitions which seems to be second order. We
also compute the critical exponents on this line at the point beta1 =0 (F4
lattice) by Finite Size Scaling techniques up to a lattice size of 24, being
these exponents different from the Mean Field ones.Comment: 26 pages LaTeX2e, 7 figures. The possibility of logarithmic
corrections has been considered, new figures and tables added. Accepted for
publication in Physical Review
- …