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Generation of Porous Structures Using Fused Deposition
The Fused Deposition Modeling process uses hardware and software machine-level
language that are very similar to that of a pen-plotter. Consequently, the·use of patterns with
poly-lines as basic geometric features, instead of the current method based on filled polygons
(monolithic models), can increase its efficiency.
In the current study, various toolpath planning methods have been developed to fabricate
porous structures. Computational domain decomposition methods can be applied to the physical
or to slice-level domains to generate structured and unstructured grids. Also, textures can be
created using periodic tiling of the layer with unit cells (squares, honeycombs, etc). Methods
'based on curves include fractal space filling curves and.change of effective road width Within a
layer or within a continuous curve. Individual phases can also be placed in binary compositions.
In present investigation, a custom software has been developed and implemented to
generate build files (SML) and slice files (SSL) for the above-mentioned structures, demonstrating the efficient control ofthe size, shape, and distribution ofporosity.Mechanical Engineerin
Wide-field mid-infrared and millimetre imaging of the high-redshift radio galaxy, 4C41.17
We present deep 350- and 1200-micron imaging of the region around 4C41.17 --
one of the most distant (z = 3.792) and luminous known radio galaxies --
obtained with the Submillimeter High Angular Resolution Camera (SHARC-II) and
the Max Planck Millimeter Bolometer Array (MAMBO). The radio galaxy is robustly
detected at 350- and 1200-micron, as are two nearby 850-micron-selected
galaxies; a third 850-micron source is detected at 350-micron and coincides
with a ~ 2-sigma feature in the 1200-micron map. Further away from the radio
galaxy an additional nine sources are detected at 1200-micron, bringing the
total number of detected (sub)millimeter selected galaxies (SMGs) in this field
to 14. Using radio images from the Very Large Array (VLA) and Spitzer
mid-infrared (mid-IR) data, we find statistically robust radio and/or 24-micron
counterparts to eight of the 14 SMGs in the field around 4C41.17. Follow-up
spectroscopy with Keck/LRIS has yielded redshifts for three of the eight
robustly identified SMGs, placing them in the redshift range 0.5 < z < 2.7,
i.e. well below that of 4C41.17. We infer photometric redshifts for a further
four sources using their 1.6-micron (rest-frame) stellar feature as probed by
the IRAC bands; only one of them is likely to be at the same redshift as
4C41.17. Thus at least four, and as many as seven, of the SMGs within the
4C41.17 field are physically unrelated to the radio galaxy. With the redshift
information at hand we are able to constrain the observed over-densities of
SMGs within radial bins stretching to R=50 and 100" (~ 0.4 and ~ 0.8Mpc at z ~
3.8) from the radio galaxy to ~ 5x and ~ 2x that of the field, dropping off to
the background value at R=150". [Abridged]Comment: 20 pages, 9 figures, accepted for publication in MNRA
A Kiloparsec-Scale Hyper-Starburst in a Quasar Host Less than 1 Gigayear after the Big Bang
The host galaxy of the quasar SDSS J114816.64+525150.3 (at redshift z=6.42,
when the Universe was <1 billion years old) has an infrared luminosity of
2.2x10^13 L_sun, presumably significantly powered by a massive burst of star
formation. In local examples of extremely luminous galaxies such as Arp220, the
burst of star formation is concentrated in the relatively small central region
of <100pc radius. It is unknown on which scales stars are forming in active
galaxies in the early Universe, which are likely undergoing their initial burst
of star formation. We do know that at some early point structures comparable to
the spheroidal bulge of the Milky Way must have formed. Here we report a
spatially resolved image of [CII] emission of the host galaxy of
J114816.64+525150.3 that demonstrates that its star forming gas is distributed
over a radius of ~750pc around the centre. The surface density of the star
formation rate averaged over this region is ~1000 M_sun/yr/kpc^2. This surface
density is comparable to the peak in Arp220, though ~2 orders of magnitudes
larger in area. This vigorous star forming event will likely give rise to a
massive spheroidal component in this system.Comment: Nature, in press, Feb 5 issue, p. 699-70
Spin-squeezing and Dicke state preparation by heterodyne measurement
We investigate the quantum non-demolition (QND) measurement of an atomic
population based on a heterodyne detection and show that the induced
back-action allows to prepare both spin-squeezed and Dicke states. We use a
wavevector formalism to describe the stochastic process of the measurement and
the associated atomic evolution. Analytical formulas of the atomic distribution
momenta are derived in the weak coupling regime both for short and long time
behavior, and they are in good agreement with those obtained by a Monte-Carlo
simulation. The experimental implementation of the proposed heterodyne
detection scheme is discussed. The role played in the squeezing process by the
spontaneous emission is considered
A Molecular Einstein Ring: Imaging a Starburst Disk Surrounding a Quasi-Stellar Object
Images of the CO 2-1 line emission, and the radio continuum emission, from
the redshift 4.12 gravitationally lensed quasi-stellar object (QSO) PSS
J2322+1944 reveal an Einstein ring with a diameter of 1.5". These observations
are modeled as a star forming disk surrounding the QSO nucleus with a radius of
2 kpc. The implied massive star formation rate is 900 M_sun/year. At this rate
a substantial fraction of the stars in a large elliptical galaxy could form on
a dynamical time scale of 10^8 years. The observation of active star formation
in the host galaxy of a high-redshift QSO supports the hypothesis of coeval
formation of supermassive black holes and stars in spheroidal galaxies.Comment: 12 pages. to appear in Science, April 200
Radio observations of the cool gas, dust, and star formation in the first galaxies
We summarize cm through submm observations of the host galaxies of z ~ 6
quasars. These observations reveal the cool molecular gas (the fuel for star
formation), the warm dust (heated by star formation), the fine structure line
emission (tracing the CNM and PDRs), and the synchrotron emission. Our results
imply active star formation in ~ 30% of the host galaxies, with star formation
rates ~ 10^3 M_sun/year, and molecular gas masses ~ 10^10 M_sun. Imaging of the
[CII] emission from the most distant quasar reveals a 'maximal starburst disk'
on a scale ~ 1.5 kpc. Gas dynamical studies suggest a departure of these
galaxies from the low-z M_{BH} -- M_{bulge} relation, with the black holes
being, on average, 15 times more massive than expected. Overall, we are
witnessing the co-eval formation of massive galaxies and supermassive black
holes within 1 Gyr of the Big Bang.Comment: First Stars and Galaxies: Challenges in the Next Decade, AIP, 2010;
Austin TX (eds Whelan, Bromm, Yoshida); 7 page
Phase transition and hyperscaling violation for scalar Black Branes
We investigate the thermodynamical behavior and the scaling symmetries of the
scalar dressed black brane (BB) solutions of a recently proposed, exactly
integrable Einstein-scalar gravity model [1], which also arises as
compactification of (p-1)-branes with a smeared charge. The extremal, zero
temperature, solution is a scalar soliton interpolating between a conformal
invariant AdS vacuum in the near-horizon region and a scale covariant metric
(generating hyperscaling violation on the boundary field theory)
asymptotically. We show explicitly that for the boundary field theory this
implies the emergence of an UV length scale (related to the size of the brane),
which decouples in the IR, where conformal invariance is restored. We also show
that at high temperatures the system undergoes a phase transition. Whereas at
small temperature the Schwarzschild-AdS BB is stable, above a critical
temperature the scale covariant, scalar-dressed BB solution, becomes
energetically preferred. We calculate the critical exponent z and the
hyperscaling violation parameter of the scalar-dressed phase. In particular we
show that the hyperscaling violation parameter is always negative. We also show
that the above features are not a peculiarity of the exact integrable model of
Ref.[1], but are a quite generic feature of Einstein-scalar and
Einstein-Maxwell-scalar gravity models for which the squared-mass of the scalar
field is positive and the potential vanishes exponentially as the scalar field
goes to minus infinity.Comment: 20 pages, 4 figures. In the revised version it has been pointed out
that the Einstein-scalar gravity model considered in the paper also arises as
compactification of black p-branes with smeared charge
350 ÎŒm dust emission from high-redshift quasars
We report detections of six high-redshift (1.8 †z †6.4), optically luminous, radio-quiet quasars at 350 ÎŒm, using the SHARC II bolometer camera at the Caltech Submillimeter Observatory. Our observations double the number of high-redshift quasars for which 350 ÎŒm photometry is available. By combining the 350 ÎŒm measurements with observations at other submillimeter/millimeter wavelengths, for each source we have determined the temperature of the emitting dust (ranging from 40 to 60 K) and the far-infrared luminosity [(0.6-2.2) Ă 10^(13) Lâ]. The combined mean spectral energy distribution of all high-redshift quasars with two or more rest-frame far-infrared photometric measurements is best fit with a graybody with temperature of 47 ± 3 K and a dust emissivity power-law spectral index of ÎČ = 1.6 ± 0.1. This warm dust component is a good tracer of the starburst activity of the quasar host galaxy. The ratio of the far-infrared to radio luminosities of infrared-luminous, radio-quiet high-redshift quasars is consistent with that found for local star-forming galaxies
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