35,633 research outputs found
The formation of planetary disks and winds: an ultraviolet view
Planetary systems are angular momentum reservoirs generated during star
formation. This accretion process produces very powerful engines able to drive
the optical jets and the molecular outflows. A fraction of the engine energy is
released into heating thus the temperature of the engine ranges from the 3000K
of the inner disk material to the 10MK in the areas where magnetic reconnection
occurs. There are important unsolved problems concerning the nature of the
engine, its evolution and the impact of the engine in the chemical evolution of
the inner disk. Of special relevance is the understanding of the shear layer
between the stellar photosphere and the disk; this layer controls a significant
fraction of the magnetic field building up and the subsequent dissipative
processes ougth to be studied in the UV.
This contribution focus on describing the connections between 1 Myr old suns
and the Sun and the requirements for new UV instrumentation to address their
evolution during this period. Two types of observations are shown to be needed:
monitoring programmes and high resolution imaging down to, at least,
milliarsecond scales.Comment: Accepted for publication in Astrophysics and Space Science 9 figure
A Poisson Mixed Model with Nonnormal Random Effect Distribution
We propose in this paper a random intercept Poisson model in which the random
effect distribution is assumed to follow a generalized log-gamma (GLG)
distribution. We derive the first two moments for the marginal distribution as
well as the intraclass correlation. Even though numerical integration methods
are in general required for deriving the marginal models, we obtain the
multivariate negative binomial model for a particular parameter setting of the
hierarchical model. An iterative process is derived for obtaining the maximum
likelihood estimates for the parameters in the multivariate negative binomial
model. Residual analysis are proposed and two applications with real data are
given for illustration.Comment: Submitted in the Computational Statistics & Data Analysis journa
Absence of Gluonic Components in Axial and Tensor Mesons
A quarkonium-gluonium mixing scheme previously developed to describe the
characteristic of the pseudoscalar mesons is applied to axial and tensor
mesons. The parameters of the model are determined by fitting the eigenvalues
of a mass matrix. The corresponding eigenvectors give the proportion of light
quarks, strange quarks and glueball in each meson. However the predictions of
the model for branching ratios and electromagnetic decays are incompatible with
the experimental results. These results suggest the absence of gluonic
components in the states of axial and tensor isosinglet mesons analyzed here.Comment: 12 page
Perceptions of Fishermen Households on the Long-Term Impact of Coastal Resources Management in Panguil Bay
Coastal resources management (CRM) has flourished as a management approach for attaining a more sustainable form of economic development in the coastal areas of the Philippines. Its proliferation, coupled with the reasonably long time it has been in implementation, now calls for an evaluation of its long-term impact as a management and development approach. In this study, the long-term impact of CRM is evaluated not from the perspectives of technical people but based on the perception of its intended primary beneficiaries--the fishermen households. It does so not by looking into a specific CRM program or project but by observing the succession of CRM activities conducted in a single coastal area--Panguil Bay, Mindanao--over many years. The objectives were to ascertain if CRM works, identify its major constraints if it does not, and recommend future courses of actions to address the constraints.coastal resources management, long-term impact indicators, ladder diagram, Panguil Bay
Perceptions of Fishermen Households on the Long-Term Impact of Coastal Resources Management in Panguil Bay
Coastal resources management (CRM) has flourished as a management approach for attaining a more sustainable form of economic development in the coastal areas of the Philippines. Its proliferation, coupled with the reasonably long time it has been in implementation, now calls for an evaluation of its long-term impact as a management and development approach. In this study, the long-term impact of CRM is evaluated not from the perspectives of technical people but based on the perception of its intended primary beneficiaries--the fishermen households. It does so not by looking into a specific CRM program or project but by observing the succession of CRM activities conducted in a single coastal area--Panguil Bay, Mindanao--over many years. The objectives were to ascertain if CRM works, identify its major constraints if it does not, and recommend future courses of actions to address the constraints.coastal resources management, long-term impact indicators, ladder diagram, Panguil Bay
The influence of statistical properties of Fourier coefficients on random surfaces
Many examples of natural systems can be described by random Gaussian
surfaces. Much can be learned by analyzing the Fourier expansion of the
surfaces, from which it is possible to determine the corresponding Hurst
exponent and consequently establish the presence of scale invariance. We show
that this symmetry is not affected by the distribution of the modulus of the
Fourier coefficients. Furthermore, we investigate the role of the Fourier
phases of random surfaces. In particular, we show how the surface is affected
by a non-uniform distribution of phases
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