5,869 research outputs found
Evaluation of a Phosphate Management Protocol to Achieve Optimum Serum Phosphate Levels in Hemodialysis Patients
Original article can be found at: http://www.sciencedirect.com/science/journal/10512276 Copyright National Kidney Foundation, Inc. DOI: 10.1053/j.jrn.2008.05.003To evaluate the effectiveness of a protocol designed to optimize serum phosphate levels in patients undergoing regular hemodialysis (HD).Peer reviewe
Water exchange at a hydrated platinum electrode is rare and collective
We use molecular dynamics simulations to study the exchange kinetics of water
molecules at a model metal electrode surface -- exchange between water
molecules in the bulk liquid and water molecules bound to the metal. This
process is a rare event, with a mean residence time of a bound water of about
40 ns for the model we consider. With analysis borrowed from the techniques of
rare-event sampling, we show how this exchange or desorption is controlled by
(1) reorganization of the hydrogen bond network within the adlayer of bound
water molecules, and by (2) interfacial density fluctuations of the bulk liquid
adjacent to the adlayer. We define collective coordinates that describe the
desorption mechanism. Spatial and temporal correlations associated with a
single event extend over nanometers and tens of picoseconds.Comment: 10 pages, 9 figure
Compact Brillouin devices through hybrid integration on Silicon
A range of unique capabilities in optical and microwave signal processing
have been demonstrated using stimulated Brillouin scattering. The desire to
harness Brillouin scattering in mass manufacturable integrated circuits has led
to a focus on silicon-based material platforms. Remarkable progress in
silicon-based Brillouin waveguides has been made, but results have been
hindered by nonlinear losses present at telecommunications wavelengths. Here,
we report a new approach to surpass this issue through the integration of a
high Brillouin gain material, As2S3, onto a silicon chip. We fabricated a
compact spiral device, within a silicon circuit, achieving an order of
magnitude improvement in Brillouin amplification. To establish the flexibility
of this approach, we fabricated a ring resonator with free spectral range
precisely matched to the Brillouin shift, enabling the first demonstration of
Brillouin lasing in a silicon integrated circuit. Combining active photonic
components with the SBS devices shown here will enable the creation of compact,
mass manufacturable optical circuits with enhanced functionality
Prerequisites in behavioral science and business: opportunities for dental education.
There is increasing pressure on recent dental school graduates to understand and successfully utilize patient management and business management strategies to run a productive dental office. Dental schools are faced with the dilemma to either add more credit hours in their already crowded curriculum or adjust predental school requirements. All fifty-nine U.S. dental schools were assessed online to determine admission requirements in the areas of behavioral science and business education. Results show that only 11.9 percent of the schools require prerequisite course work in behavioral science and no school requires prerequisite course work in business. However, 64.4 percent and 30.5 percent of schools encouraged or recommended prerequisite course work in behavioral science and business, respectively. We suggest that the dental education community involve key stakeholders to discuss the incorporation of prerequisite course work in behavioral science and business. Additional courses in these disciplines would provide dental students better backgrounds from which the dental curriculum could build a more advanced and applied perspective to better prepare students for practice
A Survey of Atomic Carbon [C I] in High-redshift Main-Sequence Galaxies
We present the first results of an ALMA survey of the lower fine structure
line of atomic carbon [C I](^3P_1\,-\,^{3}P_0) in far infrared-selected
galaxies on the main sequence at in the COSMOS field. We compare our
sample with a comprehensive compilation of data available in the literature for
local and high-redshift starbursting systems and quasars. We show that the [C
I]() luminosity correlates on global scales with the
infrared luminosity similarly to low- CO transitions. We report
a systematic variation of L'_{\rm [C\,I]^3P_1\,-\, ^3P_0}/ as a
function of the galaxy type, with the ratio being larger for main-sequence
galaxies than for starbursts and sub-millimeter galaxies at fixed .
The L'_{\rm [C\,I]^3P_1\,-\, ^3P_0}/ and / mass ratios are similar for main-sequence galaxies and for
local and high-redshift starbursts within a 0.2 dex intrinsic scatter,
suggesting that [C I] is a good tracer of molecular gas mass as CO and dust. We
derive a fraction of %
of the total carbon mass in the atomic neutral phase. Moreover, we estimate the
neutral atomic carbon abundance, the fundamental ingredient to calibrate [C I]
as a gas tracer, by comparing L'_{\rm [C\,I]^3P_1\,-\, ^3P_0} and available
gas masses from CO lines and dust emission. We find lower [C I] abundances in
main-sequence galaxies than in starbursting systems and sub-millimeter
galaxies, as a consequence of the canonical and gas-to-dust
conversion factors. This argues against the application to different galaxy
populations of a universal standard [C I] abundance derived from highly biased
samples.Comment: 14 pages + Appendix. Accepted for publication in ApJ. All the data
tables in Appendix will be also released in electronic forma
Critical behavior of a fluid in a disordered porous matrix: An Ornstein-Zernike approach
Using a liquid-state approach based on Ornstein-Zernike equations, we study
the behavior of a fluid inside a porous disordered matrix near the liquid-gas
critical point.The results obtained within various standard approximation
schemes such as lowest-order -ordering and the mean-spherical
approximation suggest that the critical behavior is closely related to that of
the random-field Ising model (RFIM).Comment: 10 pages, revtex, to appear in Physical Review Letter
Dust emission at 8-mic and 24-mic as Diagnostics of HII Region Radiative Transfer
We use the Spitzer SAGE survey of the Magellanic Clouds to evaluate the
relationship between the 8-mic PAH emission, 24-mic hot dust emission, and HII
region radiative transfer. We confirm that in the higher-metallicity Large
Magellanic Cloud, PAH destruction is sensitive to optically thin conditions in
the nebular Lyman continuum: objects identified as optically thin candidates
based on nebular ionization structure show 6 times lower median 8-mic surface
brightness (0.18 mJy arcsec^-2) than their optically thick counterparts (1.2
mJy arcsec^-2). The 24-mic surface brightness also shows a factor of 3 offset
between the two classes of objects (0.13 vs 0.44 mJy arcsec^-2, respectively),
which is driven by the association between the very small dust grains and
higher density gas found at higher nebular optical depths. In contrast, PAH and
dust formation in the low-metallicity Small Magellanic Cloud is strongly
inhibited such that we find no variation in either 8-mic or 24-mic emission
between our optically thick and thin samples. This is attributable to extremely
low PAH and dust production together with high, corrosive UV photon fluxes in
this low-metallicity environment. The dust mass surface densities and
gas-to-dust ratios determined from dust maps using Herschel HERITAGE survey
data support this interpretation.Comment: Accepted to ApJ, May 15, 2017. 10 pages, 9 figure
Resonance structure in the Li^- photodetachment cross section
We report on the first observation of resonance structure in the total cross
section for the photodetachment of Li^-. The structure arises from the
autodetaching decay of doubly excited ^1P states of Li^- that are bound with
respect to the 3p state of the Li atom. Calculations have been performed for
both Li^- and H^- to assist in the identification of these resonances. The
lowest lying resonance is a symmetrically excited intrashell resonance. Higher
lying asymmetrically excited intershell states are observed which converge on
the Li(3p) limit.Comment: 4 pages, 2 figure, 19 references, RevTeX, figures in ep
The Spitzer discovery of a galaxy with infrared emission solely due to AGN activity
We present a galaxy (SAGE1CJ053634.78-722658.5) at a redshift of 0.14 of
which the IR is entirely dominated by emission associated with the AGN. We
present the 5-37 um Spitzer/IRS spectrum and broad wavelength SED of
SAGE1CJ053634, an IR point-source detected by Spitzer/SAGE (Meixner et al
2006). The source was observed in the SAGE-Spec program (Kemper et al., 2010)
and was included to determine the nature of sources with deviant IR colours.
The spectrum shows a redshifted (z=0.14+-0.005) silicate emission feature with
an exceptionally high feature-to-continuum ratio and weak polycyclic aromatic
hydrocarbon (PAH) bands. We compare the source with models of emission from
dusty tori around AGNs from Nenkova et al. (2008). We present a diagnostic
diagram that will help to identify similar sources based on Spitzer/MIPS and
Herschel/PACS photometry. The SED of SAGE1CJ053634 is peculiar because it lacks
far-IR emission and a clear stellar counterpart. We find that the SED and the
IR spectrum can be understood as emission originating from the inner ~10 pc
around an accreting black hole. There is no need to invoke emission from the
host galaxy, either from the stars or from the interstellar medium, although a
possible early-type host galaxy cannot be excluded based on the SED analysis.
The hot dust around the accretion disk gives rise to a continuum, which peaks
at 4 um, whereas the strong silicate features may arise from optically thin
emission of dusty clouds within ~10 pc around the black hole. The weak PAH
emission does not appear to be linked to star formation, as star formation
templates strongly over-predict the measured far-IR flux levels. The SED of
SAGE1CJ053634 is rare in the local universe but may be more common in the more
distant universe. The conspicuous absence of host-galaxy IR emission places
limits on the far-IR emission arising from the dusty torus alone.Comment: Accepted for publication in A&A, 7 pages, 6 figure
Herschel and JCMT observations of the early-type dwarf galaxy NGC 205
We present Herschel dust continuum, James Clerk Maxwell Telescope CO(3-2)
observations and a search for [CII] 158 micron and [OI] 63 micron spectral line
emission for the brightest early-type dwarf satellite of Andromeda, NGC 205.
While direct gas measurements (Mgas ~ 1.5e+6 Msun, HI + CO(1-0)) have proven to
be inconsistent with theoretical predictions of the current gas reservoir in
NGC 205 (> 1e+7 Msun), we revise the missing interstellar medium mass problem
based on new gas mass estimates (CO(3-2), [CII], [OI]) and indirect
measurements of the interstellar medium content through dust continuum
emission. Based on Herschel observations, covering a wide wavelength range from
70 to 500 micron, we are able to probe the entire dust content in NGC 205
(Mdust ~ 1.1-1.8e+4 Msun at Tdust ~ 18-22 K) and rule out the presence of a
massive cold dust component (Mdust ~ 5e+5 Msun, Tdust ~ 12 K), which was
suggested based on millimeter observations from the inner 18.4 arcsec. Assuming
a reasonable gas-to-dust ratio of ~ 400, the dust mass in NGC 205 translates
into a gas mass Mgas ~ 4-7e+6 Msun. The non-detection of [OI] and the low
L_[CII]-to-L_CO(1-0) line intensity ratio (~ 1850) imply that the molecular gas
phase is well traced by CO molecules in NGC 205. We estimate an atomic gas mass
of 1.5e+4 Msun associated with the [CII] emitting PDR regions in NGC 205. From
the partial CO(3-2) map of the northern region in NGC 205, we derive a
molecular gas mass of M_H2 ~ 1.3e+5 Msun. [abridged]Comment: 16 pages, 7 figures, accepted for publication in MNRA
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