3,214 research outputs found
Boletín bibliográfico sobre don Juan Manuel y su obra (IV: 2009-2012)
Continuación del repertorio bibliográfico sobre don Juan Manuel y su obra publicado en Memorabilia en 1998 (parte I), en 2002 (parte II) y en 2009-2010 (parte III). En esta cuarta parte se recogen y clasifican referencias de estudios publicados entre 2009 y 2012
A robust morphological classification of high-redshift galaxies using support vector machines on seeing limited images. II. Quantifying morphological k-correction in the COSMOS field at 1<z<2: Ks band vs. I band
We quantify the effects of \emph{morphological k-correction} at by
comparing morphologies measured in the K and I-bands in the COSMOS area.
Ks-band data have indeed the advantage of probing old stellar populations for
, enabling a determination of galaxy morphological types unaffected by
recent star formation. In paper I we presented a new non-parametric method to
quantify morphologies of galaxies on seeing limited images based on support
vector machines. Here we use this method to classify
selected galaxies in the COSMOS area observed with WIRCam at CFHT. The obtained
classification is used to investigate the redshift distributions and number
counts per morphological type up to and to compare to the results
obtained with HST/ACS in the I-band on the same objects from other works. We
associate to every galaxy with and a probability between 0 and
1 of being late-type or early-type. The classification is found to be reliable
up to . The mean probability is . It decreases with redshift
and with size, especially for the early-type population but remains above
. The classification is globally in good agreement with the one
obtained using HST/ACS for . Above , the I-band classification
tends to find less early-type galaxies than the Ks-band one by a factor
1.5 which might be a consequence of morphological k-correction effects.
We argue therefore that studies based on I-band HST/ACS classifications at
could be underestimating the elliptical population. [abridged]Comment: accepted for publication in A&A, updated with referee comments, 12
pages, 10 figure
Spin-orbit coupling in curved graphene, fullerenes, nanotubes, and nanotube caps
A continuum model for the effective spin orbit interaction in graphene is
derived from a tight-binding model which includes the and bands.
We analyze the combined effects of the intra-atomic spin-orbit coupling,
curvature, and applied electric field, using perturbation theory. We recover
the effective spin-orbit Hamiltonian derived recently from group theoretical
arguments by Kane and Mele. We find, for flat graphene, that the intrinsic
spin-orbit coupling \Hi \propto \Delta^ 2 and the Rashba coupling due to a
perpendicular electric field , ,
where is the intra-atomic spin-orbit coupling constant for carbon.
Moreover we show that local curvature of the graphene sheet induces an extra
spin-orbit coupling term . For the values of
and curvature profile reported in actual samples of graphene, we find
that \Hi < \Delta_{\cal E} \lesssim \Delta_{\rm curv}. The effect of
spin-orbit coupling on derived materials of graphene, like fullerenes,
nanotubes, and nanotube caps, is also studied. For fullerenes, only \Hi is
important. Both for nanotubes and nanotube caps is in the
order of a few Kelvins. We reproduce the known appearance of a gap and
spin-splitting in the energy spectrum of nanotubes due to the spin-orbit
coupling. For nanotube caps, spin-orbit coupling causes spin-splitting of the
localized states at the cap, which could allow spin-dependent field-effect
emission.Comment: Final version. Published in Physical Review
Dynamic exchange coupling and Gilbert damping in magnetic multilayers
We theoretically study dynamic properties of thin ferromagnetic films in
contact with normal metals. Moving magnetizations cause a flow of spins into
adjacent conductors, which relax by spin flip, scatter back into the
ferromagnet, or are absorbed by another ferromagnet. Relaxation of spins
outside the moving magnetization enhances the overall damping of the
magnetization dynamics in accordance with the Gilbert phenomenology. Transfer
of spins between different ferromagnets by these nonequilibrium spin currents
leads to a long-ranged dynamic exchange interaction and novel collective
excitation modes. Our predictions agree well with recent
ferromagnetic-resonance experiments on ultrathin magnetic films.Comment: 15 pages, 3 figures, for MMM'02 proceeding
Spin Relaxation in Single Layer Graphene with Tunable Mobility
Graphene is an attractive material for spintronics due to theoretical
predictions of long spin lifetimes arising from low spin-orbit and hyperfine
couplings. In experiments, however, spin lifetimes in single layer graphene
(SLG) measured via Hanle effects are much shorter than expected theoretically.
Thus, the origin of spin relaxation in SLG is a major issue for graphene
spintronics. Despite extensive theoretical and experimental work addressing
this question, there is still little clarity on the microscopic origin of spin
relaxation. By using organic ligand-bound nanoparticles as charge reservoirs to
tune mobility between 2700 and 12000 cm2/Vs, we successfully isolate the effect
of charged impurity scattering on spin relaxation in SLG. Our results
demonstrate that while charged impurities can greatly affect mobility, the spin
lifetimes are not affected by charged impurity scattering.Comment: 13 pages, 5 figure
Tras la huella de Walter Scott: presencia de Ivanhoe en El último templario, de Ernesto Méndez Luengo
El presente artículo tiene como objeto analizar la influencia de Walter Scott y, más concretamente, de su Ivanhoe, en la novela El último templario, de Ernesto Méndez Luengo, dando cuenta de que el magisterio del escritor escocés no solamente resulta clave en la configuración de la novela histórica y en la divulgación de un imaginario en torno a la Edad Media en muchos casos aún vigente, sino que pervive también a través de intertextualidades y reescrituras propias de la narrativa contemporánea, en este caso para defender la inocencia de la Orden del Temple
Rapid bottom-water circulation changes during the last glacial cycle in the coastal low-latitude NE Atlantic
Previous paleoceanographic studies along the NW African margin focused on the dynamics of surface and intermediate waters, whereas little attention has been devoted to deep-water masses. Currently, these deep waters consist mainly of North Atlantic Deep Waters as part of the Atlantic Meridional Overturning Circulation (AMOC). However, this configuration was altered during periods of AMOC collapse. We present a highresolution reconstruction of bottom-water ventilation and current evolution off Mauritania from the last glacial maximum into the early Holocene. Applying redox proxies (Mo, U and Mn) measured on sediments from off Mauritania, we describe changes in deep-water oxygenation and we infer the evolution of deep-water conditions during millennial-scale climate/oceanographic events in the area. The second half of Heinrich Event 1 and the Younger Dryas were recognized as periods of reduced ventilation, coinciding with events of AMOC reduction. We propose that these weakening circulation events induced deficient deep-water oxygenation in the Mauritanian upwelling region, which together with increased productivity promoted reducing conditions and enhanced organic-matter preservation. This is the first time the effect of AMOC collapse in the area is described at high resolution, broadening the knowledge on basin-wide oceanographic changes associated with rapid climate variability during the last deglaciation
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