10,997 research outputs found
On the primacy and irreducible nature of first-person versus third-person information
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analyse\ua0qualia\ua0contents.
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Afterglow Observations Shed New Light on the Nature of X-ray Flashes
X-ray flashes (XRFs) and X-ray rich gamma-ray bursts (XRGRBs) share many
observational characteristics with long duration GRBs, but the reason for which
their prompt emission peaks at lower photon energies, , is still under
debate. Although many different models have been invoked in order to explain
the lower values, their implications for the afterglow emission were not
considered in most cases, mainly because observations of XRF afterglows have
become available only recently. Here we examine the predictions of the various
XRF models for the afterglow emission, and test them against the observations
of XRF 030723 and XRGRB 041006, the events with the best monitored afterglow
light curves in their respective class. We show that most existing XRF models
are hard to reconcile with the observed afterglow light curves, which are very
flat at early times. Such light curves are, however, naturally produced by a
roughly uniform jet with relatively sharp edges that is viewed off-axis (i.e.
from outside of the jet aperture). This type of model self consistently
accommodates both the observed prompt emission and the afterglow light curves
of XRGRB 041006 and XRF 030723, implying viewing angles from the
jet axis of and ,
respectively, where deg is the jet half-opening angle. This
suggests that GRBs, XRGRBs and XRFs are intrinsically similar relativistic jets
viewed from different angles, corresponding to
of less than 1, between 1 and a few, and more than a few, respectively, where
is the Lorentz factor. Future observations with Swift could help test
this unification scheme in which GRBs, XRGRBs and XRFs share the same basic
physics and differ only by their orientation relative to our line of sight.Comment: some references added, small typos corrected, and the important role
of HETE II emphasize
Pengujian Perda Dan Perdes Pasca Perubahan UU Pemda Dan UU Desa
The development of contemporary public law (both in the field of constitutional law and administrative law) in Indonesia was marked by the strengthening of the internal settlement administration assertion as a means of testing the legal norms of both abstract and concrete. With variations, in a legal dispute concerning the norms of concrete, these developments containing fragmentation models for partly governs how the advanced mechanism in the judiciary after taken administrative effort (eg, Law Administration) and some not at all set up (eg, Law Reform State Civil). Some of the latest legislation select general-abstract norm testing internally without linking them with the possibility of testing judicially by the judiciary, among others: Law on Local Government and Law Village. In both the legislation does not regulate how the mechanism of local regulation (Perda) or village laws (Perdes) canceled by the governor or regent / mayor, whether they can be tested back to the judiciary through judicial review mechanism. This paper intends to discuss how the implementation of the authority of judicial review by Supreme Court after the enactment Law of Local Goverment or Law of Village which is not regulated by the latest legal mechanism to test regional law in the form of regulation (local laws), including Perdes (Village Laws), whereas previous products or similar laws regulate otherwise
MetafĂsica y libertad en la filosofĂa antigua
In Greek philosophy there are two rival accounts of the relation
between ontology and freedom. In one of them the universe has its
origin in the act of free will of an intelligence. This entails, of
course, that this intelligence must be free. In the other the universe
comes from necessity from an impersonal being which has not the
features of an intelligent being and cannot be free
Analytical investigation of the dynamics of tethered constellations in earth orbit
This Quarterly Report on Tethering in Earth Orbit deals with three topics: (1) Investigation of the propagation of longitudinal and transverse waves along the upper tether. Specifically, the upper tether is modeled as three massive platforms connected by two perfectly elastic continua (tether segments). The tether attachment point to the station is assumed to vibrate both longitudinally and transversely at a given frequency. Longitudinal and transverse waves propagate along the tethers affecting the acceleration levels at the elevator and at the upper platform. The displacement and acceleration frequency-response functions at the elevator and at the upper platform are computed for both longitudinal and transverse waves. An analysis to optimize the damping time of the longitudinal dampers is also carried out in order to select optimal parameters. The analytical evaluation of the performance of tuned vs. detuned longitudinal dampers is also part of this analysis. (2) The use of the Shuttle primary Reaction Control System (RCS) thrusters for blowing away a recoiling broken tether is discussed. A microcomputer system was set up to support this operation. (3) Most of the effort in the tether plasma physics study was devoted to software development. A particle simulation code has been integrated into the Macintosh II computer system and will be utilized for studying the physics of hollow cathodes
Ab initio determination of an extended Heisenberg Hamiltonian in CuO2 layers
Accurate ab initio calculations on embedded Cu_4O_{12} square clusters,
fragments of the La_2CuO_4 lattice, confirm a value of the nearest neighbor
antiferromagnetic coupling (J=124 meV) previously obtained from ab initio
calculations on bicentric clusters and in good agreement with experiment. These
calculations predict non negligible antiferromagnetic second-neighbor
interaction (J'=6.5 meV) and four-spin cyclic exchange (K=14 meV), which may
affect the thermodynamic and spectroscopic properties of these materials. The
dependence of the magnetic coupling on local lattice distortions has also been
investigated. Among them the best candidate to induce a spin-phonon effect
seems to be the movement of the Cu atoms, changing the Cu-Cu distance, for
which the variation of the nearest neighbor magnetic coupling with the Cu-O
distance is {\Delta J}/{\Delta d_{Cu-O}}\sim 1700 cm^{-1} A^{-1}.Comment: 11 pages, 5 figures, submitted to Phys. Rev.
Perturbation of matrices and non-negative rank with a view toward statistical models
In this paper we study how perturbing a matrix changes its non-negative rank.
We prove that the non-negative rank is upper-semicontinuos and we describe some
special families of perturbations. We show how our results relate to Statistics
in terms of the study of Maximum Likelihood Estimation for mixture models.Comment: 13 pages, 3 figures. A theorem has been rewritten, and some
improvements in the presentations have been implemente
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