33,490 research outputs found
Hyposplenism in gastro-intestinal disease
The hazards of living without a spleen were recognised by the paediatricians in the early 1960âs when they focussed attention on the syndrome of fulminant sepsis, often due to pneumococcal infection, occurring in young children within the first two years of splenectomy. The danger of post-splenectomy sepsis (PSS) extends into adult life and splenectomised patients remain at risk 10, 20 and even 30 years after the operation. Problems following splenectomy may just be the tip of the iceberg. It is clear that many other diseases are associated with impaired splenic function in the presence of intact spleens.peer-reviewe
Regularized adaptive long autoregressive spectral analysis
This paper is devoted to adaptive long autoregressive spectral analysis when
(i) very few data are available, (ii) information does exist beforehand
concerning the spectral smoothness and time continuity of the analyzed signals.
The contribution is founded on two papers by Kitagawa and Gersch. The first one
deals with spectral smoothness, in the regularization framework, while the
second one is devoted to time continuity, in the Kalman formalism. The present
paper proposes an original synthesis of the two contributions: a new
regularized criterion is introduced that takes both information into account.
The criterion is efficiently optimized by a Kalman smoother. One of the major
features of the method is that it is entirely unsupervised: the problem of
automatically adjusting the hyperparameters that balance data-based versus
prior-based information is solved by maximum likelihood. The improvement is
quantified in the field of meteorological radar
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Morphological evidence for a sea-ice origin for Elysium Planitia platy terrain
Abstract not available
A survey of HC_3N in extragalactic sources: Is HC_3N a tracer of activity in ULIRGs?
Context. HC_3N is a molecule that is mainly associated with Galactic star-forming regions, but it has also been detected in extragalactic environments.
Aims. To present the first extragalactic survey of HC_3N, when combining earlier data from the literature with six new single-dish detections, and to compare HC_3N with other molecular tracers (HCN, HNC), as well as other properties (silicate absorption strength, IR flux density ratios, C_(II) flux, and megamaser activity).
Methods. We present mm IRAM 30 m, OSO 20 m, and SEST observations of HC_3N rotational lines (mainly the J = 10â9 transition) and of the J = 1â0 transitions of HCN and HNC. Our combined HC_3N data account for 13 galaxies (excluding the upper limits reported for the non-detections), while we have HCN and HNC data for more than 20 galaxies.
Results. A preliminary definition âHC_3N-luminous galaxyâ is made based upon the HC_3N/HCN ratio. Most (~80%) HC_3N-luminous galaxies seem to be deeply obscured galaxies and (U)LIRGs. A majority (~60% or more) of the HC3N-luminous galaxies in the sample present OH mega- or strong kilomaser activity. A possible explanation is that both HC_3N and OH megamasers need warm dust for their excitation. Alternatively, the dust that excites the OH megamaser offers protection against UV destruction of HC_3N. A high silicate absorption strength is also found in several of the HC_3N-luminous objects, which may help the HC3N to survive. Finally, we find that a high HC_3N/HCN ratio is related to a high dust temperature and a low C_(II) flux
Out of equilibrium quantum field dynamics of an initial thermal state after a change in the external field
The effects of the initial temperature in the out of equilibrium quantum
field dynamics in the presence of an homogeneous external field are
investigated. We consider an initial thermal state of temperature T for a
constant external field J. A subsequent sign flip of the external field, J to
-J, gives rise to an out of equilibrium nonperturbative quantum field dynamics.
The dynamics is studied here for the symmetry broken lambda(Phi^2)^2 scalar N
component field theory in the large N limit. We find a dynamical effective
potential for the expectation value that helps to understand the dynamics. The
dynamics presents two regimes defined by the presence or absence of a temporal
trapping close to the metastable equilibrium position of the potential. The two
regimes are separated by a critical value of the external field that depends on
the initial temperature. The temporal trapping is shorter for larger initial
temperatures or larger external fields. Parametric resonances and spinodal
instabilities amplify the quantum fluctuations in the field components
transverse to the external field. When there is a temporal trapping this is the
main mechanism that allows the system to escape from the metastable state for
large N. Subsequently backreaction stops the growth of the quantum fluctuations
and the system enters a quasiperiodic regime.Comment: LaTeX, 19 pages, 12 .eps figures, improved version to appear in Phys
Rev
EmergĂȘncia de sementes de castanha-do-brasil em função do tamanho e da idade.
bitstream/item/40153/1/Circ-Tec-56-CPATU.pd
Cellular automata on regular rooted trees
We study cellular automata on regular rooted trees. This includes the
characterization of sofic tree shifts in terms of unrestricted Rabin automata
and the decidability of the surjectivity problem for cellular automata between
sofic tree shifts
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