891 research outputs found
Low Rank Vector Bundles on the Grassmannian G(1,4)
Here we define the concept of -regularity for coherent sheaves on the
Grassmannian G(1,4) as a generalization of Castelnuovo-Mumford regularity on
. In this setting we prove analogs of some classical properties. We
use our notion of -regularity in order to prove a splitting criterion for
rank 2 vector bundles with only a finite number of vanishing conditions. In the
second part we give the classification of rank 2 and rank 3 vector bundles
without "inner" cohomology (i.e. H^i_*(E)=H^i(E\otimes\Q)=0 for any
) on G(1,4) by studying the associated monads.Comment: 11 pages, no figure
The water supercooled regime as described by four common water models
The temperature scale of simple water models in general does not coincide
with the natural one. Therefore, in order to make a meaningful evaluation of
different water models a temperature rescaling is necessary. In this paper we
introduce a rescaling using the melting temperature and the temperature
corresponding to the maximum of the heat capacity to evaluate four common water
models (TIP4P-Ew, TIP4P-2005, TIP5P-Ew and Six-Sites) in the supercooled
regime. Although all the models show the same general qualitative behavior, the
TIP5P-Ew appears as the best representation of the supercooled regime when the
rescaled temperature is used. We also analyze, using thermodynamic arguments,
the critical nucleus size for ice growth. Finally, we speculate on the possible
reasons why atomistic models do not usually crystalize while the coarse grained
mW model do crystallize.Comment: 8 pages, 8 figure
Radiosounding: Possible change in aerological data due to instrument change
radiosounding system allows to measure the profile of some meteorological quantities (temperature, humidity, pressure) from the ground up to a certain altitude. Such systems are continuously used by meteorological services in order to perform periodical measurements during the day, at
pre-determined times. The evolution of instrumentation technology leads to a fast obsolescence of equipment
through time, so that, inevitably, new instrumentation replaces the old one. The new VAISALA Radiosound RS92 has been recently introduced to substitute previous model RS90. The RS90 is currently used by many national and international institutes, including the Italian Air Force Meteorological Service (Servizio Meteorologico dell’Aeronautica Militare). In order to assess the way in which the substitution of RS90s with the new RS92s would affect measures performed by the altitude observation network with regard also to the historical series, several comparative measurements have been conducted by the “Reparto Sperimentazioni di Meteorologia Aeronautica” at Vigna di Valle (Rome). During this testing series,
Company VAISALA has given a remarkable level of cooperation by a continuous presence of technicians. The entire test has been performed according to WMO (World Meteorological Organization) protocols
Earthquakes as Precursors of Ductile Shear Zones in the Dry and Strong Lower Crust
The rheology and the conditions for viscous flow of the dry granulite facies lower crust are still
poorly understood. Viscous shearing in the dry and strong lower crust commonly localizes in pseudotachylyte
veins, but the deformation mechanisms responsible for the weakening and viscous shear localization in
pseudotachylytes are yet to be explored. We investigated examples of pristine and mylonitized pseudotachylytes
in anorthosites from Nusfjord (Lofoten, Norway). Mutual overprinting relationships indicate that pristine
and mylonitized pseudotachylytes are coeval and resulted from the cyclical interplay between brittle and
viscous deformation. The stable mineral assemblage in the mylonitized pseudotachylytes consists of
plagioclase, amphibole, clinopyroxene, quartz, biotite,6garnet6K-feldspar. Amphibole-plagioclase
geothermobarometry and thermodynamic modeling indicate that pristine and mylonitized pseudotachylytes
formed at 650\u20137508C and 0.7\u20130.8 GPa. Thermodynamic modeling indicates that a limited amount of H2O
infiltration (0.20\u20130.40 wt. %) was necessary to stabilize the mineral assemblage in the mylonite. Diffusion creep
is identified as the main deformation mechanisms in the mylonitized pseudotachylytes based on the lack of
crystallographic preferred orientation in plagioclase, the high degree of phase mixing, and the synkinematic
nucleation of amphiboles in dilatant sites. Extrapolation of flow laws to natural conditions indicates that
mylonitized pseudotachylytes are up to 3 orders of magnitude weaker than anorthosites deforming by
dislocation creep, thus highlighting the fundamental role of lower crustal earthquakes as agents of weakening
in strong granulites
Planck Low Frequency Instrument: Beam Patterns
The Low Frequency Instrument on board the ESA Planck satellite is coupled to
the Planck 1.5 meter off-axis dual reflector telescope by an array of 27
corrugated feed horns operating at 30, 44, 70, and 100 GHz. We briefly present
here a detailed study of the optical interface devoted to optimize the angular
resolution (10 arcmin at 100 GHz as a goal) and at the same time to minimize
all the systematics coming from the sidelobes of the radiation pattern. Through
optical simulations, we provide shapes, locations on the sky, angular
resolutions, and polarization properties of each beam.Comment: On behalf of the Planck collaboration. 3 pages, 1 figure. Article
published in the Proceedings of the 2K1BC Experimental Cosmology at
millimetre wavelength
Biological phosphorus and nitrogen removal in a full scale sequencing batch reactor treating piggery wastewater
Research activities carried out at ENEA during the last few years allowed the development of a Sequencing Batch Reactor (SBR) that is able to remove biologically organic waste, nitrogen and phosphorus and that was shown to be particularly suited to obtaining low effluent nutrient concentrations even starting from concentrated wastes. Research on optimisation of time cycles and on process modelling, allowed an advanced comprehension of reactor behaviour and the development of a process able to obtain more than 98% removal of nitrogen, phosphorus and COD, and therefore almost capable of matching effluent standards with a sole biological process. On the basis of laboratory results and process modelling, a full scale SBR plant has been designed and realised. This plant, in ten months of operation, is achieving even better results compared to the laboratory ones
Weighted Castelnuovo-Mumford Regularity and Weighted Global Generation
Weighted Castelnuovo-Mumford Regularity and Weighted Global GenerationWe
introduce and study a notion of Castelnuovo-Mumford regularity suitable for
weighted projective spaces
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