1,536 research outputs found
ÂżUna estĂ©tica de la energĂa?
La energĂa se ha convertido en uno de los grandes temas de la arquitectura, pero la incorporaciĂłn de lo energĂ©tico al diseño no suele ir mĂĄs allĂĄ del simple trato con la tĂ©cnica. En realidad, mĂĄs que abrir un debate estĂ©tico, el diĂĄlogo con la energĂa muchas veces lo ha cerrado, pues es frecuente que los asuntos relacionados con lo que en sentido amplio llamamos âtermodinĂĄmicaâ se pongan en manos de âespecialistasâ poco dados a lucubraciones formales (profesionales del âbioclimatismoâ, ingenieros y socioecĂłlogos). El resultado ha sido una especie de escolĂĄstica tecnocrĂĄtica que parece despreciar cuanto no se mida en los tĂ©rminos de lo que se denomina âsostenibleâ. Y tambiĂ©n un tipo de funcionalismo, el ecolĂłgico, cuyo destino es repetir los errores de los viejos funcionalismos, en su confianza de encontrar la piedra filosofal que transmute la energĂa en forma construida, sin que en tal proceso parezca haber espacio para las mediaciones de tipo cultural. La conferencia repasarĂĄ las mediaciones culturales y estĂ©ticas que competen a la relaciĂłn de la arquitectura con la energĂa, preguntĂĄndose por la pertinencia de una âestĂ©ticaâ asociada a ella, con todas las contradicciones y paradojas que este tĂ©rmino implica.Universidad de MĂĄlaga. Campus de Excelencia Internacional AndalucĂa Tech
The central parsecs of M87: jet emission and an elusive accretion disc
We present the first simultaneous spectral energy distribution (SED) of M87
core at a scale of 0.4 arcsec () across the electromagnetic
spectrum. Two separate, quiescent, and active states are sampled that are
characterized by a similar featureless SED of power-law form, and that are thus
remarkably different from that of a canonical active galactic nuclei (AGN) or a
radiatively inefficient accretion source. We show that the emission from a jet
gives an excellent representation of the core of M87 core covering ten orders
of magnitude in frequency for both the active and the quiescent phases. The
inferred total jet power is, however, one to two orders of magnitude lower than
the jet mechanical power reported in the literature. The maximum luminosity of
a thin accretion disc allowed by the data yields an accretion rate of , assuming 10% efficiency. This power
suffices to explain M87 radiative luminosity at the jet-frame, it is however
two to three order of magnitude below that required to account for the jet's
kinetic power. The simplest explanation is variability, which requires the core
power of M87 to have been two to three orders of magnitude higher in the last
200 yr. Alternatively, an extra source of power may derive from black hole
spin. Based on the strict upper limit on the accretion rate, such spin power
extraction requires an efficiency an order of magnitude higher than predicted
from magnetohydrodynamic simulations, currently in the few hundred per cent
range.Comment: 18 pages, 6 figures. Accepted for publication in MNRA
Fate of 15N-fertilizers in the soil-plant system of a forage rotation under conservation and plough tillage.
The long-term effect of conventional plough tillage (PT) and conservation minimum tillage (MT) on soil
N (0-5, 5-15, 15-30, 30-45 and 45-60 cm), recovery efficiency of 15N-fertilizer (REN), plant N concentration
and N exported with crops was evaluated during two years in a 14-year-old ryegrass-maize forage
rotation. Adjacent PT (n=9) and MT (n=9) plots were randomly assigned in triplicate to three treatments
to which 15NH4
15NO3 (10 atom % 15N) was applied in one of the three first fertilizations (15NOctober-,
15NMarch- and 15NMay-fertilizer), the others being done with unlabelled N. Plant N concentration (% N) was
affected (p ryegrass-2
(1.9 ± 0.4%) > maize-2 (1.4 ± 0.1 %) > maize-1 (1.1 ± 0.2 %)] and the crop-tillage interaction (22 % of
variance explained). Jointly considering all data, more 15N-fertilizer was recovered in the MT (25 ± 4 %)
than in the PT soil profile (19 ± 6 %) at the end of the experiment whereas the N exported with the crops
was unaffected by the tillage system and varied from 5-6 % (15NOctober-fertilizer) to 45-49% (15NMarchfertilizer)
and 52-53 % (15NMay-fertilizer; despite only three instead of four subsequent crops were
studied).The 15N unaccounted for in the case of 15NOctober-fertilizer (72 ± 5 %) was more than twice that
in 15NMarch- (34 ± 7 %) and 15NMay-fertilizer (25 ± 14 %). Considering soil, site and weather conditions,
denitrification and nitrate leaching during the ryegrass-1 crop were the most likely processes explaining
the high losses of the 15NOctober-fertilizer. Results suggested a higher initial immobilization of the applied
15N in the soil organic matter (SOM) of MT, that reduces 15N availability to the first crop, followed by
an increase of the residual availability of the fertilizer 15N to the subsequent 2-3 crops.Peer reviewe
IBSE: An OWL Interoperability Evaluation Infrastructure
The technology that supports the Semantic Web presents a great diversity and, whereas all the tools use different types of ontologies, not all of them share a common knowledge representation model, which may pose problems when they try to interoperate. The Knowledge Web European Network of Excellence is organizing a benchmarking of interoperability of ontology tools using OWL as interchange language with the goal of assessing and improving tool interoperability. This paper presents the development of IBSE, an evaluation infrastructure that allows executing automatically the benchmarking experiments and provides an easy way of analysing the results. Thus,including new tools into the evaluation infrastructure will be simple and straightforward
Impact of fire and post-fire management techniques on soil chemical properties
The effects of
fire (
Control
burned soil) and two emergency stabilisation techniques (grass
Seeding
and straw
Mulching
) on 20 chemical characteristics were evaluated on 0
â
5 cm top-soils sampled 1, 90, 180 and
365 days after an experimental
fi
re in a steep shrubland of a temperate-humid region (NW Spain). Most
part of pH (in H
2
O and KCl) variance was explained by the sampling date. No clear temporal trends were
identi
fi
able for total soil C and N content, likely due to the large SOM pool in these soils; however, changes
on soil
ÎŽ
13
C were explained by the deposition of
13
C-depleted ashes, followed by its progressive erosion,
while those on soil
ÎŽ
15
N were a consequence of
fi
re induced N outputs. After the
fi
re, NH
4
+
â
N, P, Na, K, Mg,
Ca, Mn, Cu, Zn and B concentrations increased, while those of NO
3
â
â
N, Al, Fe and Co did not vary significantly.
Despite a significant decline with time, concentrations of Mg, Ca and Mn at the end of the study were still
higher than in unburned soil, while those of K, Cu, Zn and B were similar to the pre-fire levels and those of
NH
4
+
â
N, P and Na were below pre-fire values.
Mulching
and
Seeding
treatments for burned soil emergency
stabilisation had significant effects on soil
ÎŽ
15
N and extractable K, Mg and Ca, while data were inconclusive
for their possible effects on the extractable Al, Fe and C
On the monitoring of surface displacement in connection with volcano reactivation in Tenerife, Canary Islands, using space techniques
Geodetic volcano monitoring in Tenerife has mainly focused on the Las Cañadas Caldera, where a geodetic micronetwork and a levelling profile are located. A sensitivity test of this geodetic network showed that it should be extended to cover the whole island for volcano monitoring purposes. Furthermore, InSAR allowed detecting two unexpected movements that were beyond the scope of the traditional geodetic network. These two facts prompted us to design and observe a GPS network covering the whole of Tenerife that was monitored in August 2000. The results obtained were accurate to one centimetre, and confirm one of the deformations, although they were not definitive enough to confirm the second one. Furthermore, new cases of possible subsidence have been detected in areas where InSAR could not be used to measure deformation due to low coherence. A first modelling attempt has been made using a very simple model and its results seem to indicate that the deformation observed and the groundwater level variation in the island may be related. Future observations will be necessary for further validation and to study the time evolution of the displacements, carry out interpretation work using different types of data (gravity, gases, etc) and develop models that represent the island more closely. The results obtained are important because they might affect the geodetic volcano monitoring on the island, which will only be really useful if it is capable of distinguishing between displacements that might be linked to volcanic activity and those produced by other causes. One important result in this work is that a new geodetic monitoring system based on two complementary techniques, InSAR and GPS, has been set up on Tenerife island. This the first time that the whole surface of any of the volcanic Canary Islands has been covered with a single network for this purpose. This research has displayed the need for further similar studies in the Canary Islands, at least on the islands which pose a greater risk of volcanic reactivation, such as Lanzarote and La Palma, where InSAR techniques have been used already
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