10,684 research outputs found
Seguiment del contingut de nitrats al sòl i en planta en parcel·les comercials de panís al Pla d'Urgell
En aquest treball es presenten els resultats parcials del primer any de seguiment de nitrats al sòl i en planta de parcel·les comercials de panís (Zea mays L.) a la zona regable dels canals d'Urgell. Les parcel·les han estat seleccionades a partir del coneixement dels sòls de la zona i com a principal criteri el de la representativitat espaial. L'excés de nitrogen a la zona, present a les capes freàtiques i a la xarxa de reg i de drenatges, ve donat per l'aplicació en excés de nitrogen als cultius, entre els quals el panís és un dels més importants. A les parcel·les seguides s'han aplicat dosis de nitrogen que van dels 250 als 350 kg N/ha. Els primers resultats mostren com les aplicacions que fan els agricultors són independents de les disponibilitats inicials de nitrogen al sòl. També es mostra com la determinació de nitrats a la base de la tija al final del cicle pot servir per conèixer si les disponibilitats de N han estat excessives. Els rendiments més elevats, 13,5 Mg/ha, han coincidit amb les aplicacions de N més baixes, les disponibilitats de nitrogen també més baixes i amb el contingut de nitrats a la base de la tija més baix (0,4 g NNO3/ kg). Tot això demostra que la racionalització de l'ús del nitrogen és possible.This paper presents the partial results of the first year monitoring of soil and plant nitrate contents in commercial maize (Zea mays L.) in the Urgell canal irrigated area. The fields have been selected starting from the knowledge of the soils in the area and their spatial representativeness as main criteria. The excess of nitrogen in the area, present in the groundwater as well as in the irrigation water, is due to overfertilisation of the crops, of which maize is one of the most importants. In the monitored fields the applied nitrogen fertiliser ranges from 250 to 350 kg/ha. The first results show that the farmers applications are not related to the initially available soil nitrogen. They also show how the determination of nitrates in the lower part of the stem at the end of the cycle may help to show if the N availability has been excessive. The higher yields, 13.5 Mg/ha are the same with the lower fertilizer applications, with the lower soil N availabilities and with the lower contents of nitrates in the lower part of the stem (0.4 g NNO3/ kg). All of this show there is ample room to rationalize the nitrogen use.En este trabajo se presentan los resultados parciales del primer año de seguimiento de nitratos en el suelo y en planta de parcelas comerciales de maíz (Zea mays L.) en la zona regable de los canales de Urgell. Las parcelas han sido seleccionadas a partir del conocimiento de los suelos de la zona y como criterio principal el de su representatividad espacial. El exceso de nitrógeno en la zona, presente en las capas freáticas y en la red de riego y de drenajes viene dado por la aplicación en exceso de nitróge-no a los cultivos, dentro de los cuales el maíz es uno de los más importantes. En las parcelas seguidas se han aplicado dosis de nitrógeno que van de los 250 a los 350 kg N/ha. Los primeros resultados muestran como las aplicaciones que hacen los agricultores son independientes de las disponibilidades iniciales de nitrógeno en el suelo. También se muestra como la determinación de nitratos en la base del tallo al final del ciclo puede servir para conocer si las disponibilidades de N han sido excesivas. Los rendimientos más elevados 13,5 Mg/ha han coincidido con las aplicaciones de N más bajas, las disponibilidades de nitrógeno también más bajas y con el contenido de nitratos en la base del tallo más bajo (0,4 g N-NO3/kg). Todo esto demuestra que la racionalización del uso del nitrógeno es posible
A vestige low metallicity gas shell surrounding the radio galaxy 0943-242 at z=2.92
Observations are presented showing the doublet CIV 1550 absorption lines
superimposed on the CIV emission in the radio galaxy 0943-242. Within the
errors, the redshift of the absorption system that has a column density of
N_CIV = 10^{14.5 +- 0.1} cm-2 coincides with that of the deep Ly-alpha
absorption trough observed by Rottgering et al. (1995). The gas seen in
absorption has a resolved spatial extent of at least 13 kpc (the size of the
extended emission line region). We first model the absorption and emission gas
as co-spatial components with the same metallicity and degree of excitation.
Using the information provided by the emission and absorption line ratios of
CIV and Ly-alpha, we find that the observed quantities are incompatible with
photoionization or collisional ionization of cloudlets with uniform properties.
We therefore reject the possibility that the absorption and emission phases are
co-spatial and favour the explanation that the absorption gas has low
metallicity and is located further away from the host galaxy (than the emission
line gas). The estimated low metallicity for the absorption gas in 0943-242 (Z
\~ 1% solar) and its proposed location -outer halo outside the radio cocoon-
suggest that its existence preceeds the observed AGN phase and is a vestige of
the initial starburst at the onset of formation of the parent galaxy.Comment: 11 pages,5 figures, A&A accepte
Visibility Fringe Reduction Due to Noise-Induced Effects: Microscopic Approach to Interference Experiments
Decoherence is the main process behind the quantum to classical transition.
It is a purely quantum mechanical effect by which the system looses its ability
to exhibit coherent behavior. The recent experimental observation of
diffraction and interference patterns for large molecules raises some
interesting questions. In this context, we identify possible agents of
decoherence to take into account when modeling these experiments and study
theirs visible (or not) effects on the interference pattern. Thereby, we
present an analysis of matter wave interferometry in the presence of a dynamic
quantum environment and study how much the visibility fringe is reduced and in
which timescale the decoherence effects destroy the interference of massive
objects. Finally, we apply our results to the experimental data reported on
fullerenes and cold neutrons.Comment: 14 pages, 5 figures. Version to appear in Mod. Phys.
The ancient place-name for the village of Torredonjimeno
El nombre antiguo (pre-romano o romano) de “Torredonjimeno” (Jaén) sigue siendo objeto de disputa. Para unos sería “Tucci Vetus” y para otros “Abra”. Por otra parte se le atribuye el nombre de “Ossaria” en época visigótica. Finalmente, en el propio “Torredonjimeno” y en general en la provincia de Jaén se da por cierto que su nombre fue “Tosiria”, del que deriva el localicio “Tosiriano” de uso generalizado. En este trabajo tratamos de arrojar luz a este problema toponímico.The ancient (pre-roman or roman) place-name for the village of “Torredonjimeno” (Jaen, in the South of Spain) is actually disputed. For some scholars it would be “Tucci Vetus”, for some others “Abra”. Further on, during the Visigothic time, it would be named “Ossaria”. Finally, in Torredonjimeno and generally speaking, in Jaen province, the names used nowadays are “Tosiria” for the village and “Tosirian” for its inhabitants. The present research work is aimed to bring some light into the problem
Status of the ANAIS Dark Matter Project at the Canfranc Underground Laboratory
The ANAIS experiment aims at the confirmation of the DAMA/LIBRA signal. A
detailed analysis of two NaI(Tl) crystals of 12.5 kg each grown by Alpha
Spectra will be shown: effective threshold at 1 keVee is at reach thanks to
outstanding light collection and robust PMT noise filtering protocols and the
measured background is well understood down to 3 keVee, having quantified K, U
and Th content and cosmogenic activation in the crystals. A new detector was
installed in Canfranc in March 2015 together with the two previous modules and
preliminary characterization results will be presented. Finally, the status and
expected sensitivity of the full experiment with 112 kg will be reviewed.Comment: Contributed to the 11th Patras Workshop on Axions, WIMPs and WISPs,
Zaragoza, June 22 to 26, 201
PKS1932-46: a radio source in an interacting group?
We present the results of a multiwavelength study of the z=0.23 radio source
PKS1932-46. VIMOS IFU spectroscopy is used to study the morphology, kinematics
and ionisation state of the EELR surrounding this source, and also a companion
galaxy at a similar redshift. Near- and far-IR imaging observations obtained
using the NTT and SPITZER are used to analyse the underlying galaxy
morphologies and the nature of the AGN. The host galaxy is identified as an ~M*
elliptical. Combining Spitzer mid-IR with X-ray, optical and near-IR imaging
observations of this source, we conclude that its AGN is underluminous for a
radio source of this type, despite its status as a BLRG. However, given its
relatively large [OIII] luminosity it is likely that the AGN was substantially
more luminous in the recent past (<10^4 years ago). The EELR is remarkably
extensive and complex, reminiscent of the systems observed around sources at
higher redshifts/radio powers, and the gas is predominantly ionised by a
mixture of AGN photoionisation and emission from young stars. We confirm the
presence of a series of star-forming knots extending N-S from the host galaxy,
with more prodigious star formation occuring in the merging companion galaxy to
the northeast, which has sufficient luminosity at mid- to far-IR wavelengths to
be classified as a LIRG. The most plausible explanation of our observations is
that PKS1932-46 is a member of an interacting galaxy group, and that the
impressive EELR is populated by star-forming, tidal debris. We suggest that the
AGN itself may currently be fuelled by material associated either with the
current interaction, or with a previous merger event. Surprisingly, it is the
companion object, rather than the radio source host galaxy, which is undergoing
the bulk of the star formation activity within the group.Comment: 15 pages, 14 figures (compressed for astro-ph, 1 colour). Accepted
for publication in MNRAS. Abstract abridge
Light yield determination in large sodium iodide detectors applied in the search for dark matter
Application of NaI(Tl) detectors in the search for galactic dark matter
particles through their elastic scattering off the target nuclei is well
motivated because of the long standing DAMA/LIBRA highly significant positive
result on annual modulation, still requiring confirmation. For such a goal, it
is mandatory to reach very low threshold in energy (at or below the keV level),
very low radioactive background (at a few counts/keV/kg/day), and high
detection mass (at or above the 100 kg scale). One of the most relevant
technical issues is the optimization of the crystal intrinsic scintillation
light yield and the efficiency of the light collecting system for large mass
crystals. In the frame of the ANAIS (Annual modulation with NaI Scintillators)
dark matter search project large NaI(Tl) crystals from different providers
coupled to two photomultiplier tubes (PMTs) have been tested at the Canfranc
Underground Laboratory. In this paper we present the estimates of the NaI(Tl)
scintillation light collected using full-absorption peaks at very low energy
from external and internal sources emitting gammas/electrons, and
single-photoelectron events populations selected by using very low energy
pulses tails. Outstanding scintillation light collection at the level of
15~photoelectrons/keV can be reported for the final design and provider chosen
for ANAIS detectors. Taking into account the Quantum Efficiency of the PMT
units used, the intrinsic scintillation light yield in these NaI(Tl) crystals
is above 40~photoelectrons/keV for energy depositions in the range from 3 up to
25~keV. This very high light output of ANAIS crystals allows triggering below
1~keV, which is very important in order to increase the sensitivity in the
direct detection of dark matter
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