9,709 research outputs found
Factor Price Equalization : Geometrical Conditions
This paper presents a geometrical approach to the univalence problem for a system of cost functions. We present a natural (almost tautological) extension of a geometrical theorem due to McKenzie: our sufficient condition is related to the non-separability of two cones formed by convex combinations of the rows of the Jacobian matrix. This means that the cones spanned by the rows of Jacobian matrix (i.e., production coefficients) do not move wildly so that the two cones corresponding to the two end points (i.e., factor price vectors) cannot be separated by the hyperplane orthogonal to the vector of changes in factor prices. Unlike most ofthe previous propositions, our condition can naturally include as a special case such linear systems as having a non-singular matrix. We also give an alternative condition employing the concept of monotone functions. Dual to the above result is one more condition, which is shown to be
closely connected with Kuhn's WARP-like requirement when the given functions are concave as well as homogeneous of degree one
ASCA Slew Survey
We are systematically analyzing ASCA GIS data taken during the satellite
attitude maneuver operation. Our motivation is to search for serendipitous hard
X-ray sources and make the ASCA Slew Survey catalog.
During its operational life from 1993 February to 2000 July, ASCA carried out
more than 2,500 maneuver operations, and total exposure time during the
maneuver was ~415 ksec after data screening. Preliminary results are briefly
reported.Comment: Proceedings for "X-ray surveys in the light of new observations",
Santander (Spain), 2002 September. 1 pag
The X-ray Line Emission from the Supernova Remnant W49B
The Galactic supernova remnant W49B has one of the most impressive X-ray
emission line spectra obtained with the Advanced Satellite for Cosmology and
Astronomy (ASCA). We use both plasma line diagnostics and broadband model fits
to show that the Si and S emission lines require multiple spectral components.
The spectral data do not necessarily require individual elements to be
spatially stratified, as suggested by earlier work, although when ASCA line
images are considered, it is possible that Fe is stratified with respect to Si
and S. Most of the X-ray emitting gas is from ejecta, based on the element
abundances required, but is surprisingly close to being in collisional
ionization equilibrium. A high ionization age implies a high internal density
in a young remnant. The fitted emission measure for W49B indicates a minimum
density of 2 cm^-3, with the true density likely to be significantly higher.
W49B probably had a Type Ia progenitor, based on the relative element
abundances, although a low-mass Type II progenitor is still possible. We find
persuasive evidence for Cr and possibly Mn emission in the ASCA spectrum--the
first detection of these elements in X-rays from a cosmic source.Comment: 22 pages incl 8 postscript figures, to appear in Ap
XMM-Newton study of the ULIRG NGC 6240
A recently performed XMM-Newton observation of the ULIRG NGC 6240 clearly
indicates the presence of an AGN contribution to its X-ray spectrum. In the 5.0
- 7.0 keV energy range there is a clear signature of the fluorescent Fe K lines
at 6.4, 6.7 and 6.9 keV, respectively.
The line strength of the 6.4 keV line cannot be produced by a thermal
component. The 0.3 - 10.0 keV spectral energy distribution is characterized by
the following components: (I) two hot thermal components (the starburst), (II)
one direct component (heavily absorbed; AGN is hidden), (III) one reflection
component (the AGN), (IV) three narrow Fe lines. The model parameters for the
broad-band spectral energy distribution are consistent with the results of
previously works.Comment: 2 pages incl. 2 figures, to appear in the proceedings of the "New
Century of X-ray Astronomy" symposium held in Yokohama, Japan (March 6-8,
2001), eds. H. Kunieda and H. Inoue, ASP pres
Mixing of metals during star cluster formation: statistics and implications for chemical tagging
Ongoing surveys are in the process of measuring the chemical abundances in
large numbers of stars, with the ultimate goal of reconstructing the formation
history of the Milky Way using abundances as tracers. However, interpretation
of these data requires that we understand the relationship between stellar
distributions in chemical and physical space, i.e., how similar in chemical
abundance do we expect a pair of stars to be as a function of the distance
between their formation sites. We investigate this question by simulating the
gravitational collapse of a turbulent molecular cloud extracted from a
galaxy-scale simulation, seeded with chemical inhomogeneities with different
initial spatial scales. We follow the collapse from galactic scales down to
resolutions scales of pc, and find that, during this process,
turbulence mixes the metal patterns, reducing the abundance scatter initially
present in the gas by an amount that depends on the initial scale of
inhomogeneity of each metal field. However, we find that regardless of the
initial spatial structure of the metals at the onset of collapse, the final
stellar abundances are highly correlated on distances below a few pc, and
nearly uncorrelated on larger distances. Consequently, the star formation
process defines a natural size scale of pc for chemically-homogenous
star clusters, suggesting that any clusters identified as homogenous in
chemical space must have formed within pc of one another. However, in
order to distinguish different star clusters in chemical space, observations
across multiple elements will be required, and the elements that are likely to
be most efficient at separating distinct clusters in chemical space are those
whose correlation length in the ISM is of order tens of pc, comparable to the
sizes of individual molecular clouds.Comment: 15 pages, 10 figures; submitted to MNRA
Comment on `Equilibrium crystal shape of the Potts model at the first-order transition point'
We comment on the article by Fujimoto (1997 J. Phys. A: Math. Gen., Vol. 30,
3779), where the exact equilibrium crystal shape (ECS) in the critical Q-state
Potts model on the square lattice was calculated, and its equivalence with ECS
in the Ising model was established. We confirm these results, giving their
alternative derivation applying the transformation properties of the
one-particle dispersion relation in the six-vertex model. It is shown, that
this dispersion relation is identical with that in the Ising model on the
square lattice.Comment: 4 pages, 1 figure, LaTeX2
Aclimatação e quarentena: manejos muitas vezes esquecidos - quando não realizados, podem representar grandes perdas.
Quem nunca comprou um peixe e ao chegar em casa colocouo direto no aquário e, em um perÃodo compreendido entre quatro e sete dias, ele morreu ou todos os peixes do aquário começam a adoecer? Bom, esse é um cenário bem mais comum do que se imagina. Isso ocorre principalmente devido à falta de cuidados e de manejos adequados para a manutenção desse animal em cativeiro.bitstream/item/123109/1/12-aclimatacao-e-quarentena.pd
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