1,321 research outputs found
Enhanced [CII] emission in a z=4.76 submillimetre galaxy
We present the detection of bright [CII] emission in the z=4.76 submillimetre
galaxy LESS J033229.4-275619 using the Atacama Pathfinder EXperiment. This
represents the highest redshift [CII] detection in a submm selected,
star-formation dominated system. The AGN contributions to the [CII] and
far-infrared (FIR) luminosities are small. We find an atomic mass derived from
[CII] comparable to the molecular mass derived from CO. The ratio of the [CII],
CO and FIR luminosities imply a radiation field strength G_0~10^3 and a density
~10^4 cm^-3 in a kpc-scale starburst, as seen in local and high redshift
starbursts. The high L_[CII]/L_FIR=2.4x10^-3 and the very high
L_[CII]/L_CO(1-0) ~ 10^4 are reminiscent of low metallicity dwarf galaxies,
suggesting that the highest redshift star-forming galaxies may also be
characterised by lower metallicities. We discuss the implications of a reduced
metallicity on studies of the gas reservoirs, and conclude that especially at
very high redshift, [CII] may be a more powerful and reliable tracer of the
interstellar matter than CO.Comment: 5 pages, 2 figures; accepted for publication in Astronomy &
Astrophysics Letter
Progress toward sonifying Napoleon’s march and fluid flow simulations through binaural horizons
Cross-modal data analytics—that can be rendered for experience
through vision, hearing, and touch—poses a fundamental
challenge to designers. Non-linguistic sonification is a
well-researched means for non-visual pattern recognition but
higher density datasets pose a challenge. Because human hearing
is optimized for detecting locations on a horizontal plane, our
approach recruits this optimization by employing an immersive
binaural horizontal plane using auditory icons. Two case studies
demonstrate our approach: A sonic translation of a map and a
sonic translation of a computational fluid dynamics simulation
Mechanical control of the directional stepping dynamics of the kinesin motor
Among the multiple steps constituting the kinesin's mechanochemical cycle,
one of the most interesting events is observed when kinesins move an 8-nm step
from one microtubule (MT)-binding site to another. The stepping motion that
occurs within a relatively short time scale (~100 microsec) is, however, beyond
the resolution of current experiments, therefore a basic understanding to the
real-time dynamics within the 8-nm step is still lacking. For instance, the
rate of power stroke (or conformational change), that leads to the
undocked-to-docked transition of neck-linker, is not known, and the existence
of a substep during the 8-nm step still remains a controversial issue in the
kinesin community. By using explicit structures of the kinesin dimer and the MT
consisting of 13 protofilaments (PFs), we study the stepping dynamics with
varying rates of power stroke (kp). We estimate that 1/kp <~ 20 microsec to
avoid a substep in an averaged time trace. For a slow power stroke with 1/kp>20
microsec, the averaged time trace shows a substep that implies the existence of
a transient intermediate, which is reminiscent of a recent single molecule
experiment at high resolution. We identify the intermediate as a conformation
in which the tethered head is trapped in the sideway binding site of the
neighboring PF. We also find a partial unfolding (cracking) of the binding
motifs occurring at the transition state ensemble along the pathways prior to
binding between the kinesin and MT.Comment: 26 pages, 10 figure
ALMA reveals a chemically evolved submillimeter galaxy at z=4.76
The chemical properties of high-z galaxies provide important information to
constrain galaxy evolutionary scenarios. However, widely-used metallicity
diagnostics based on rest-frame optical emission lines are not usable for
heavily dust-enshrouded galaxies (such as Sub-Millimeter Galaxies; SMGs),
especially at z>3. Here we focus on the flux ratio of the far-infrared
fine-structure emission lines [NII]205um and [CII]158um to assess the
metallicity of high-z SMGs. Through ALMA cycle 0 observations, we have detected
the [NII]205um emission in a strongly [CII]-emitting SMG, LESS J033229.4-275619
at z=4.76. The velocity-integrated [NII]/[CII] flux ratio is 0.043 +/- 0.008.
This is the first measurement of the [NII]/[CII] flux ratio in high-z galaxies,
and the inferred flux ratio is similar to the ratio observed in the nearby
universe (~0.02-0.07). The velocity-integrated flux ratio and photoionization
models suggest that the metallicity in this SMG is consistent with solar,
implying the chemical evolution has progressed very rapidly in this system at
z=4.76. We also obtain a tight upper limit on the CO(12-11) transition, which
translates into CO(12-11)/CO(2-1) <3.8 (3 sigma). This suggests that the
molecular gas clouds in LESS J033229.4-275619 are not affected significantly by
the radiation field emitted by the AGN in this system.Comment: 5 pages, 3 figures, accepted for publication in Astronomy and
Astrophysics Letter
Submillimeter galaxies behind the Bullet Cluster (1E 0657-56)
Clusters of galaxies are effective gravitational lenses able to magnify
background galaxies and making it possible to probe the fainter part of the
galaxy population. Submillimeter galaxies, which are believed to be
star-forming galaxies at typical redshifts of 2 to 3, are a major contaminant
to the extended Sunyaev-Zeldovich (SZ) signal of galaxy clusters. For a proper
quantification of the SZ signal the contribution of submillimeter galaxies
needs to be quantified. The aims of this study are to identify submillimeter
sources in the field of the Bullet Cluster (1E 0657-56), a massive cluster of
galaxies at z~0.3, measure their flux densities at 870 micron, and search for
counterparts at other wavelengths to constrain their properties. We carried out
deep observations of the submillimeter continuum emission at 870 micron using
the Large APEX BOlometer CAmera (LABOCA) on the Atacama Pathfinder EXperiment
(APEX) telescope. Several numerical techniques were used to quantify the noise
properties of the data and extract sources. In total, seventeen sources were
found. Thirteen of them lie in the central 10 arcminutes of the map, which has
a pixel sensitivity of 1.2 mJy per 22 arcsec beam. After correction for flux
boosting and gravitational lensing, the number counts are consistent with
published submm measurements. Nine of the sources have infrared counterparts in
Spitzer maps. The strongest submm detection coincides with a source previously
reported at other wavelengths, at an estimated redshift z~2.7. If the submm
flux arises from two images of a galaxy magnified by a total factor of 75, as
models have suggested, its intrinsic flux would be around 0.6 mJy, consistent
with an intrinsic luminosity below 10^12 L_sun.Comment: Accepted by A&A, 15 pages, 11 figure
Sonification of Flow Instabilities in CFD Aneurysm Models
Paper presented at 2018 Canadian Society of Mechanical Engineers International Congress, 27-30 May 2018.Recent investigations using image-based computational flow dynamics (CFD) have revealed turbulent-like blood flow instabilities (hemodynamics) within intracranial cerebral aneurysms and surrounding vasculature, which may contribute to aneurysm initiation, growth, and rupture. We describe a method derived from spectral decomposition of flow for inspecting and characterizing these “turbulent-like” hemodynamic structures in intracranial aneurysms by sonification of CFD generated data. Motivated by auscultation techniques, the current research seeks to address the limitations of conventional CFD animations by allowing the user to listen to complex flow patterns that are often difficult to discern visually. In the process, the proposed method of sonification is successfully applied to a series of datasets resulting from highfidelity numerical simulations of intracranial aneurysms. The resulting framework is shown to be highly efficient in performing parametric sonification in real time
A continuous isotropic-nematic liquid crystalline transition of F-actin solutions
The phase transition from the isotropic (I) to nematic (N) liquid crystalline
suspension of F-actin of average length m or above was studied by local
measurements of optical birefringence and protein concentration. Both
parameters were detected to be continuous in the transition region, suggesting
that the I-N transition is higher than 1st order. This finding is consistent
with a recent theory by Lammert, Rokhsar & Toner (PRL, 1993, 70:1650),
predicting that the I-N transition may become continuous due to suppression of
disclinations. Indeed, few line defects occur in the aligned phase of F-actin.
Individual filaments in solutions of a few mg/ml F-actin undergo fast
translational diffusion along the filament axis, whereas both lateral and
rotational diffusions are suppressed.Comment: 4 pages with 4 figures. Submitted to Physical Review Letter
A Retrospective Study To Determine Patients' Satisfaction With Fixed Dental Prostheses Provided During The Period 2008 – 2012 at The School of Dentistry In Trinidad
Introduction : The School of Dentistry undertakes the training of dental students, where they provide fixed dental prostheses such as crowns bridges and onlays to patients of the dental polyclinic. The aim of this study was to determine the patient satisfaction with their fixed prostheses and the quantity of remakes at the School of Dentistry polyclinic during the period 2008-2012. Methods : The lab records of fixed prosthetic work during the period 2008-2012 were analyzed. Patients who received treatment during this period were contacted via telephone for a structured interview via a questionnaire. Results : Ninety-six (96) patients were contacted via telephone and 72% of patients were female. Fifty-six (56) crowns and onlays, 22 conventional bridges and 18 resin-retained bridges were provided for patients. Ninety-six (96%) of patients were satisfied with the aesthetics (appearance) of their prosthesis immediately after fitting and 90.7 % were still satisfied with the appearance at the time of interview. 79.2% of prostheses were still in place at the time of interview but patients reported that 18% of crowns failed, 22.7% of conventional bridges and 27.8% of resin-retained bridges had failed. Fifteen (15%) of the fixed prostheses were remade. However, the majority of patients (99 %) were overall satisfied with their services at the School of Dentistry in Trinidad. Conclusion : Patients are generally satisfied with the fixed prosthetic work delivered at the School of Dentistry polyclinic and highly satisfied with the services provided. The amount of remakes whilst small can be reduced with more stringent quality assurance measure
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