6,055 research outputs found
Weber's Mixed BoundaryâValue Problem in Electrodynamics
Electrodynamics problems with mixed boundary values promise to assume increasing practical importance in fields such as plasma physics. A new method of attacking such problems in three dimensions is presented and discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69922/2/JMAPAQ-8-3-518-1.pd
The Mean Absorption Line Spectra of a Selection of Luminous z~6 Lyman Break Galaxies
We examine the absorption-line spectra of a sample of 31 luminous () Lyman break galaxies at redshift z sime 6 using data taken with the FOCAS and OSIRIS spectrographs on the Subaru and GTC telescopes. For two of these sources we present longer exposure data taken at higher spectral resolutions from ESO's X-shooter spectrograph. Using these data, we demonstrate the practicality of stacking our lower-resolution data to measure the depth of various interstellar and stellar absorption lines to probe the covering fraction of low-ionization gas and the gas phase and stellar metallicities near the end of the era of cosmic reionization. From maximum absorption-line depths of Si ii λ1260 and C ii λ1334, we infer a mean covering fraction of â„0.85 ± 0.16 for our sample. This is larger than that determined using similar methods for lower-luminosity galaxies at slightly lower redshifts, suggesting that the most luminous galaxies appear to have a lower escape fraction than fainter galaxies, and therefore may not play a prominent role in concluding reionization. Using various interstellar absorption lines we deduce gas-phase metallicities close to solar, indicative of substantial early enrichment. Using selected stellar absorption lines, we model our spectra with a range of metallicities using techniques successfully employed at lower redshift and deduce a stellar metallicity of solar, consistent with the stellar massâstellar metallicity relation recently found at z ~ 3â5. We discuss the implications of these metallicity estimates for the typical ages of our luminous galaxies and conclude our results imply initial star formation at redshifts z ~ 10, consistent with independent analyses of earlier objects
The Network Design Problem with Relays
Cataloged from PDF version of article.The network design problem with relays (NDPR) is defined on an undirected graph G = (V,E,K), where V = {1,...,n} is
a vertex set, E = {(i,j):i,j 2 V,i < j} is an edge set. The set K = {(o(k),d(k))} is a set of communication pairs (or commodities):
o(k) 2 V and d(k) 2 V denote the origin and the destination of the kth commodity, respectively. With each edge (i,j)
are associated a cost cij and a length dij. With vertex i is associated a fixed cost fi of locating a relay at i. The NDPR consists
of selecting a subset E of edges of E and of locating relays at a subset V of vertices of V in such a way that: (1) the sum Q of
edge costs and relay costs is minimized; (2) there exists a path linking the origin and the destination of each commodity in
which the length between the origin and the first relay, the last relay and the destination, or any two consecutive relays does
not exceed a preset upper bound k. This article develops a lower bound procedure and four heuristics for the NPDR. These
are compared on several randomly generated instances with |V| 6 1002 and |E| 6 1930.
2006 Elsevier B.V. All rights reserved
The first Frontier Fields cluster: 4.5{\mu}m excess in a z~8 galaxy candidate in Abell 2744
We present in this letter the first analysis of a z~8 galaxy candidate found
in the Hubble and Spitzer imaging data of Abell 2744, as part of the Hubble
Frontier Fields legacy program. We applied the most commonly-used methods to
select exceptionally high-z galaxies by combining non-detection and
color-criteria using seven HST bands. We used GALFIT on IRAC images for fitting
and subtracting contamination of bright nearby sources. The physical properties
have been inferred from SED-fitting using templates with and without nebular
emission. This letter is focussed on the brightest candidate we found
(m=26.2) over the 4.9 arcmin field of view covered by the WFC3.
It shows a non-detection in the ACS bands and at 3.6{\mu}m whereas it is
clearly detected at 4.5{\mu}m with rather similar depths. This break in the
IRAC data could be explained by strong [OIII]+H{\beta} lines at z~8 which
contribute to the 4.5{\mu}m photometry. The best photo-z is found at
z~8.0, although solutions at low-redshift (z~1.9) cannot be
completely excluded, but they are strongly disfavoured by the SED-fitting work.
The amplification factor is relatively small at {\mu}=1.490.02. The Star
Formation Rate in this object is ranging from 8 to 60 Mo/yr, the stellar mass
is in the order of M=(2.5-10) x 10Mo and the size is
r~0.350.15 kpc. This object is one of the first z~8 LBG candidates showing
a clear break between 3.6{\mu}m and 4.5{\mu}m which is consistent with the IRAC
properties of the first spectroscopically confirmed galaxy at a similar
redshift. Due to its brightness, the redshift of this object could potentially
be confirmed by near infrared spectroscopy with current 8-10m telescopes. The
nature of this candidate will be revealed in the coming months with the arrival
of new ACS and Spitzer data, increasing the depth at optical and near-IR
wavelengths.Comment: 4 pages, 2 figures, Accepted for publication in Astronomy and
Astrophysics Letter
Analyses spectroscopiques du liquide céphalo-rachidien de rat en ex vivo et du noyau du raphé dorsal in vivo
Les propriĂ©tĂ©s d'absorption et de fluorescence du liquide cĂ©phalo-rachidien (LCR) ponctionnĂ© au niveau de la cisterna magna du rat, sont analysĂ©es puis comparĂ©es Ă l'Ă©mission mesurĂ©e in situ dans le noyau du raphe dorsal du rat libre de tous mouvements. Les mesures de fluorescence en ex vivo du LCR et in vivo du noyau raphĂ© dorsal, ont Ă©tĂ© rĂ©alisĂ©es par la mise en Ćuvre d'un microcapteur Ă fibre optique (FOCS). La fluorescence mesurĂ©e in vivo sous excitation Ă 337 nm, prĂ©sente 2 pics d'Ă©mission situĂ©s vers 410 et 460 nm. Les spectres d'absorption, d'Ă©mission en fluorescence statique et en fluorescence induite par laser sont rapportĂ©s. Avec des domaines de longueur d'onde d'excitation de 300-315 nm, 320-355 nm et 360-470 nm, les spectres d'Ă©mission du LCR en ex vivo montrent respectivement des pics centrĂ©s vers 340 nm, 390 nm et 530 nm. MalgrĂ© les limites liĂ©es aux diffĂ©rences de localisation anatomique, ces approches ainsi que celles de la littĂ©rature permettent de suggĂ©rer que le signal de fluorescence mesurĂ© in vivo Ă 460nm pourrait dĂ©pendre pour une grande partie du NADH intracellulaire
Unforgettable cruelties: influence of Antonin Artaud's theater of cruelty on Abla Farhoud's Jeux de Patience and Wajdi Mouawad's Incendies
The goal of the present study is to analyze the influence of Antonin Artaud's theater of cruelty on the present-day dramas of Lebanese-Canadian playwrights Abla Farhoud and Wajdi Mouawad. Their respective use of what Artaud calls the concrete language of the stage as well as their tendency to question the role of articulated language in the expression of trauma allows for new understandings of the theater's role within communities experiencing turmoil, displacement, and loss. By employing Artaudian cruelty on both a formal as well as a thematic level, the plays of Farhoud and Mouawad bear witness to the atrocities of war, while simultaneously offering new hope to victims and survivors of trauma by positioning the stage as a theater of witness
Disk Heating, Galactoseismology, and the Formation of Stellar Halos
Deep photometric surveys of the Milky Way have revealed diffuse structures
encircling our Galaxy far beyond the "classical" limits of the stellar disk.
This paper reviews results from our own and other observational programs, which
together suggest that, despite their extreme positions, the stars in these
structures were formed in our Galactic disk. Mounting evidence from recent
observations and simulations implies kinematic connections between several of
these distinct structures. This suggests the existence of collective disk
oscillations that can plausibly be traced all the way to asymmetries seen in
the stellar velocity distribution around the Sun. There are multiple
interesting implications of these findings: they promise new perspectives on
the process of disk heating, they provide direct evidence for a stellar halo
formation mechanism in addition to the accretion and disruption of satellite
galaxies, and, they motivate searches of current and near-future surveys to
trace these oscillations across the Galaxy. Such maps could be used as
dynamical diagnostics in the emerging field of "Galactoseismology", which
promises to model the history of interactions between the Milky Way and its
entourage of satellites, as well examine the density of our dark matter halo.
As sensitivity to very low surface brightness features around external galaxies
increases, many more examples of such disk oscillations will likely be
identified. Statistical samples of such features not only encode detailed
information about interaction rates and mergers, but also about long
sought-after dark matter halo densities and shapes. Models for the Milky Way's
own Galactoseismic history will therefore serve as a critical foundation for
studying the weak dynamical interactions of galaxies across the universe.Comment: 20 pages, 5 figures, accepted in for publication in a special edition
of the journal "Galaxies", reporting the proceedings of the conference "On
the Origin (and Evolution) of Baryonic Galaxy Halos", Puerto Ayora, Ecuador,
March 13-17 2017, Eds. Duncan A. Forbes and Ericson D. Lope
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