13,076 research outputs found
Solar type II radio bursts associated with CME expansions as shown by EUV waves
We investigate the physical conditions of the sources of two metric Type-II
bursts associated with CME expansions with the aim of verifying the
relationship between the shocks and the CMEs, comparing the heights of the
radio sources and the heights of the EUV waves associated with the CMEs. The
heights of the EUV waves associated with the events were determined in relation
to the wave fronts. The heights of the shocks were estimated by applying two
different density models to the frequencies of the Type-II emissions and
compared with the heights of the EUV waves. For the 13 June 2010 event, with
band-splitting, the shock speed was estimated from the frequency drifts of the
upper and lower branches of the harmonic lane, taking into account the H/F
frequency ratio fH/fF = 2. Exponential fits on the intensity maxima of the
branches revealed to be more consistent with the morphology of the spectrum of
this event. For the 6 June 2012 event, with no band-splitting and with a clear
fundamental lane on the spectrum, the shock speed was estimated directly from
the frequency drift of the fundamental emission, determined by linear fit on
the intensity maxima of the lane. For each event, the most appropriate density
model was adopted to estimate the physical parameters of the radio source. The
13 June 2010 event presented a shock speed of 664-719 km/s, consistent with the
average speed of the EUV wave fronts of 609 km/s. The 6 June 2012 event was
related to a shock of speed of 211-461 km/s, also consistent with the average
speed of the EUV wave fronts of 418 km/s. For both events, the heights of the
EUV wave revealed to be compatible with the heights of the radio source,
assuming a radial propagation of the shock.Comment: Accepted for publication in Astronomy and Astrophysic
Quantum computing with incoherent resources and quantum jumps
Spontaneous emission and the inelastic scattering of photons are two natural
processes usually associated with decoherence and the reduction in the capacity
to process quantum information. Here we show that when suitably detected, these
photons are sufficient to build all the fundamental blocks needed to perform
quantum computation in the emitting qubits while protecting them from
deleterious dissipative effects. We exemplify by showing how to teleport an
unknown quantum state and how to efficiently prepare graph states for the
implementation of measurement-based quantum computation.Comment: 5 pages, 5 figure
Abundance Patterns in Stars in the Bulge and Galactic Center
We discuss oxygen and iron abundance patterns in K and M red-giant members of
the Galactic bulge and in the young and massive M-type stars inhabiting the
very center of the Milky Way. The abundance results from the different bulge
studies in the literature, both in the optical and the infrared, indicate that
the [O/Fe]-[Fe/H] relation in the bulge does not follow the disk relation, with
[O/Fe] values falling above those of the disk. Based on these elevated values
of [O/Fe] extending to large Fe abundances, it is suggested that the bulge
underwent a rapid chemical enrichment with perhaps a top-heavy initial mass
function. The Galactic Center stars reveal a nearly uniform and slightly
elevated (relative to solar) iron abundance for a studied sample which is
composed of 10 red giants and supergiants. Perhaps of more significance is the
fact that the young Galactic Center M-type stars show abundance patterns that
are reminiscent of those observed for the bulge population and contain enhanced
abundance ratios of alpha-elements relative to either the Sun or Milky Way disk
at near-solar metallicities.Comment: requires iaus.cls; to appear in Formation and Evolution of Galaxy
Bulges, Proceedings IAU Symposium No. 245, 2007, M. Bureau et al. eds., in
pres
Viana do Castelo Littoral Geopark Geosites
[Excerto] O território do Geoparque Litoral de Viana do Castelo
abrange a área do concelho de Viana do Castelo e está legalmente
constituído como Associação Geoparque Litoral de
Viana do Castelo. Esta entidade tem por missão contribuir para
a proteção, valorização e dinamização do património natural e
cultural, com especial ênfase no património geológico, numa
perspetiva de aprofundamento e divulgação do conhecimento
científico, promovendo o turismo e o desenvolvimento sustentável
em torno de uma herança geológica que remonta ao
Câmbrico Inferior...info:eu-repo/semantics/publishedVersio
Making the computation of approximations of invariant measures and its attractors for IFS and GIFS, through the deterministic algorithm, tractable
We present algorithms to compute approximations of invariant measures and its
attractors for IFS and GIFS, using the deterministic algorithm in a tractable
way, with code optimization strategies and use of data structures and search
algorithms. The results show that these algorithms allow the use of these
(G)IFS in a reasonable running time.Comment: Submitted to Numerical Algorithm
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