57 research outputs found
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Humanism in the Age of COVID-19: Renewing Focus on Communication and Compassion
The global COVID-19 pandemic has become one of the largest clinical and operational challenges faced by emergency medicine, and our EDs continue to see increased volumes of infected patients, many of whom are not only ill, but acutely aware and fearful of their circumstances and potential mortality. Given this, there may be no more important time to focus on staff-patient communication and expression of compassion.However, many of the techniques usually employed by emergency clinicians to provide comfort to patients and their families are made more challenging or impossible by the current circumstances. Geriatric ED patients, who are at increased risk of severe disease, are particularly vulnerable to the effects of isolation.Despite many challenges, emergency clinicians have at their disposal a myriad of tools that can still be used to express compassion and empathy to their patients. Placing emphasis on using these techniques to maximize humanism in the care of COVID-19 patients during this crisis has the potential to bring improvements to ED patient care well after this pandemic has passed
The Projected Three-point Correlation Function: Theory and Observations
We report results for the angular three-point galaxy correlation function in
the APM survey and compare them with theoretical expectations. For the first
time, these measurements extend to sufficiently large scales to probe the
weakly non-linear regime. On large scales, the results are in good agreement
with the predictions of non-linear cosmological perturbation theory, for a
model with initially Gaussian fluctuations and linear power spectrum
consistent with that inferred from the APM survey. These results reinforce the
conclusion that large-scale structure is driven by non-linear gravitational
instability and that APM galaxies are relatively unbiased tracers of the mass
on large scales; they also provide stringent constraints upon models with
non-Gaussian initial conditions and strongly exclude the standard cold dark
matter model.Comment: 10 pages, latex, 2 figures, submited to ApJ Le
The Formation of High Redshift Submillimeter Galaxies
We describe a model for the formation of \zsim 2 Submillimeter Galaxies
(SMGs) which simultaneously accounts for both average and bright SMGs while
providing a reasonable match to their mean observed spectral energy
distributions (SEDs). By coupling hydrodynamic simulations of galaxy mergers
with the high resolution 3D polychromatic radiative transfer code Sunrise, we
find that a mass sequence of merger models which use observational constraints
as physical input naturally yield objects which exhibit black hole, bulge, and
H2 gas masses similar to those observed in SMGs. The dominant drivers behind
the 850 micron flux are the masses of the merging galaxies and the stellar
birthcloud covering fraction. The most luminous (S850 ~ 15 mJy) sources are
recovered by ~10^13 Msun 1:1 major mergers with a birthcloud covering fraction
close to unity, whereas more average SMGs ~5-7 mJy) may be formed in lower mass
halos ~5x10^12 Msun. These models demonstrate the need for high spatial
resolution hydrodynamic and radiative transfer simulations in matching both the
most luminous sources as well as the full SEDs of SMGs. While these models
suggest a natural formation mechanism for SMGs, they do not attempt to match
cosmological statistics of galaxy populations; future efforts along this line
will help ascertain the robustness of these models.Comment: MNRAS Accepted; Revised version includes expanded discussion of
simulated radio properties of SMG
Galaxy-Quasar correlations between APM galaxies and Hamburg-ESO QSOs
We detect angular galaxy-QSO cross-correlations between the APM Galaxy
Catalogue and a preliminary release (consisting of roughly half of the
anticipated final catalogue) of the Hamburg-ESO Catalogue of Bright QSOs as a
function of source QSO redshift using multiple cross-correlation estimators.
Each of the estimators yield very similar results, implying that the APM
catalogue and the Hamburg-ESO survey are both fair samples of the respective
true galaxy and QSO populations. Though the signal matches the expectations of
gravitational lensing qualitatively, the strength of the measured
cross-correlation signal is significantly greater than the CDM models of
lensing by large scale structure would suggest. This same disagreement between
models and observation has been found in several earlier studies. We estimate
our confidence in the correlation detections versus redshift by generating 1000
random realizations of the Hamburg-ESO QSO survey: We detect physical
associations between galaxies and low-redshift QSOs at 99% confidence and
detect lensing associations at roughly 95% confidence for QSOs with redshifts
between 0.6 and 1. Control cross-correlations between Galactic stars and QSOs
show no signal. Finally, the overdensities (underdensities) of galaxies near
QSO positions relative to those lying roughly 135 - 150 arcmin away are
uncorrelated with differences in Galactic extinction between the two regions,
implying that Galactic dust is not significantly affecting the QSO sample.Comment: 35 pages total, including 9 figures. Accepted by the Astrophysical
Journa
Succinylated Octopamine Ascarosides and a New Pathway of Biogenic Amine Metabolism in Caenorhabditis elegans
The ascarosides, small-molecule signals derived from combinatorial
assembly of primary metabolism-derived building
blocks, play a central role in Caenorhabditis elegans biology and
regulate many aspects of development and behavior in this
model organism as well as in other nematodes. Using HPLCMS/
MS-based targeted metabolomics, we identified novel ascarosides
incorporating a side chain derived from succinylation of
the neurotransmitter octopamine. These compounds, named
osas#2, osas#9, and osas#10, are produced predominantly by L1
larvae, where they serve as part of a dispersal signal, whereas
these ascarosides are largely absent from the metabolomes of
other life stages. Investigating the biogenesis of these octopamine-
derived ascarosides, we found that succinylation represents
a previously unrecognized pathway of biogenic amine
metabolism. At physiological concentrations, the neurotransmitters
serotonin, dopamine, and octopamine are converted to a
large extent into the corresponding succinates, in addition to
the previously described acetates. Chemically, bimodal deactivation
of biogenic amines via acetylation and succinylation parallels
posttranslational modification of proteins via acetylation
and succinylation of L-lysine. Our results reveal a small-molecule
connection between neurotransmitter signaling and
interorganismal regulation of behavior and suggest that ascaroside
biosynthesis is based in part on co-option of degradative
biochemical pathways
Clinical, radiologic, pathologic, and molecular characteristics of long-term survivors of diffuse intrinsic pontine glioma (DIPG): a collaborative report from the International and European Society for Pediatric Oncology DIPG registries
Purpose Diffuse intrinsic pontine glioma (DIPG) is a brainstem malignancy with a median survival of < 1 year. The International and European Society for Pediatric Oncology DIPG Registries collaborated to compare clinical, radiologic, and histomolecular characteristics between short-term survivors (STSs) and long-term survivors (LTSs). Materials and Methods Data abstracted from registry databases included patients from North America, Australia, Germany, Austria, Switzerland, the Netherlands, Italy, France, the United Kingdom, and Croatia. Results Among 1,130 pediatric and young adults with radiographically confirmed DIPG, 122 (11%) were excluded. Of the 1,008 remaining patients, 101 (10%) were LTSs (survival ≥ 2 years). Median survival time was 11 months (interquartile range, 7.5 to 16 months), and 1-, 2-, 3-, 4-, and 5-year survival rates were 42.3% (95% CI, 38.1% to 44.1%), 9.6% (95% CI, 7.8% to 11.3%), 4.3% (95% CI, 3.2% to 5.8%), 3.2% (95% CI, 2.4% to 4.6%), and 2.2% (95% CI, 1.4% to 3.4%), respectively. LTSs, compared with STSs, more commonly presented at age < 3 or > 10 years (11% v 3% and 33% v 23%, respectively; P < .001) and with longer symptom duration ( P < .001). STSs, compared with LTSs, more commonly presented with cranial nerve palsy (83% v 73%, respectively; P = .008), ring enhancement (38% v 23%, respectively; P = .007), necrosis (42% v 26%, respectively; P = .009), and extrapontine extension (92% v 86%, respectively; P = .04). LTSs more commonly received systemic therapy at diagnosis (88% v 75% for STSs; P = .005). Biopsies and autopsies were performed in 299 patients (30%) and 77 patients (10%), respectively; 181 tumors (48%) were molecularly characterized. LTSs were more likely to harbor a HIST1H3B mutation (odds ratio, 1.28; 95% CI, 1.1 to 1.5; P = .002). Conclusion We report clinical, radiologic, and molecular factors that correlate with survival in children and young adults with DIPG, which are important for risk stratification in future clinical trials
A Physical Model for z~2 Dust Obscured Galaxies
We present a physical model for the origin of z~2 Dust-Obscured Galaxies
(DOGs), a class of high-redshift ULIRGs selected at 24 micron which are
particularly optically faint (24/R>1000). By combining N-body/SPH simulations
of high redshift galaxy evolution with 3D polychromatic dust radiative transfer
models, we find that luminous DOGs (with F24 > 0.3 mJy at z~2 are well-modeled
as extreme gas-rich mergers in massive (~5x10^12-10^13 Msun) halos, with
elevated star formation rates (~500-1000 Msun/yr) and/or significant AGN growth
(Mdot > 0.5 Msun/yr), whereas less luminous DOGs are more diverse in nature. At
final coalescence, merger-driven DOGs transition from being starburst dominated
to AGN dominated, evolving from a "bump" to a power-law shaped mid-IR (IRAC)
spectral energy distribution (SED). After the DOG phase, the galaxy settles
back to exhibiting a "bump" SED with bluer colors and lower star formation
rates. While canonically power-law galaxies are associated with being
AGN-dominated, we find that the power-law mid-IR SED can owe both to direct AGN
contribution, as well as to a heavily dust obscured stellar bump at times that
the galaxy is starburst dominated. Thus power-law galaxies can be either
starburst or AGN dominated. Less luminous DOGs can be well-represented either
by mergers, or by massive ($M_{\rm baryon} ~5x10^11 Msun) secularly evolving
gas-rich disc galaxies (with SFR > 50 Msun/yr). By utilising similar models as
those employed in the SMG formation study of Narayanan et al. (2010), we
investigate the connection between DOGs and SMGs. We find that the most heavily
star-forming merger driven DOGs can be selected as Submillimetre Galaxies
(SMGs), while both merger-driven and secularly evolving DOGs typically satisfy
the BzK selection criteria.Comment: Accepted by MNRAS; major changes include better description of
dependency on ISM specification and updated models allowing dust to evolve
with metallicity
The shape of the SDSS DR5 galaxy power spectrum
We present a Fourier analysis of the clustering of galaxies in the combined
Main galaxy and Luminous Red Galaxy (LRG) Sloan Digital Sky Survey (SDSS) Data
Release 5 (DR5) sample. The aim of our analysis is to consider how well we can
measure the cosmological matter density using the signature of the horizon at
matter-radiation equality embedded in the large-scale power spectrum. The new
data constrains the power spectrum on scales 100--600h^-1Mpc with significantly
higher precision than previous analyses of just the SDSS Main galaxies, due to
our larger sample and the inclusion of the LRGs. This improvement means that we
can now reveal a discrepancy between the shape of the measured power and linear
CDM models on scales 0.01<k<0.15hMpc^-1, with linear model fits favouring a
lower matter density (Omega_m=0.22+/-0.04) on scales 0.01<k<0.06hMpc^-1 and a
higher matter density (Omega_m=0.32+/-0.01) when smaller scales are included,
assuming a flat LCDM model with h=0.73 and n_s=0.96. This discrepancy could be
explained by scale-dependent bias and, by analysing subsamples of galaxies, we
find that the ratio of small-scale to large-scale power increases with galaxy
luminosity, so all of the SDSS galaxies cannot trace the same power spectrum
shape over 0.01<k<0.2hMpc^-1. However, the data are insufficient to clearly
show a luminosity-dependent change in the largest scale at which a significant
increase in clustering is observed, although they do not rule out such an
effect. Significant scale-dependent galaxy bias on large-scales, which changes
with the r-band luminosity of the galaxies, could potentially explain
differences in our Omega_m estimates and differences previously observed
between 2dFGRS and SDSS power spectra and the resulting parameter constraints.Comment: 21 pages, 19 figures, minor corrections to match version accepted by
Ap
The physical scale of the far-infrared emission in the most luminous submillimetre galaxies II: evidence for merger-driven star formation
We present high-resolution 345 GHz interferometric observations of two
extreme luminous (L_{IR}>10^{13} L_sun), submillimetre-selected galaxies (SMGs)
in the COSMOS field with the Submillimeter Array (SMA). Both targets were
previously detected as unresolved point-sources by the SMA in its compact
configuration, also at 345 GHz. These new data, which provide a factor of ~3
improvement in resolution, allow us to measure the physical scale of the
far-infrared in the submillimetre directly. The visibility functions of both
targets show significant evidence for structure on 0.5-1 arcsec scales, which
at z=1.5 translates into a physical scale of 5-8 kpc. Our results are
consistent with the angular and physical scales of two comparably luminous
objects with high-resolution SMA followup, as well as radio continuum and CO
sizes. These relatively compact sizes (<5-10 kpc) argue strongly for
merger-driven starbursts, rather than extended gas-rich disks, as the preferred
channel for forming SMGs. For the most luminous objects, the derived sizes may
also have important physical consequences; under a series of simplifying
assumptions, we find that these two objects in particular are forming stars
close to or at the Eddington limit for a starburst.Comment: 9 pages, 3 Figures, submitted to MNRA
A physical model for the origin of the diffuse cosmic infrared background
We present a physical model for origin of the cosmic diffuse infrared
background (CDIRB). By utilizing the observed stellar mass function and its
evolution as input to a semi-empirical model of galaxy formation, we isolate
the physics driving diffuse IR emission. The model includes contributions from
three primary sources of IR emission: steady-state star formation owing to
isolated disk galaxies, interaction-driven bursts of star formation owing to
close encounters and mergers, and obscured active galactic nuclei (AGN). We
find that most of the CDIRB is produced by equal contributions from objects at
z=0.5-1 and z>1, as suggested by recent observations. Of those sources, the
vast majority of the emission originates in systems with low to moderate IR
luminosities (L_{IR}<10^{12} $L_sun); the most luminous objects contribute
significant flux only at high-redshifts (z>2). All star formation in ongoing
mergers accounts for <10% of the total at all wavelengths and redshifts, while
emission directly attributable to the interaction-driven burst itself accounts
for <5%. We furthermore find that obscured AGN contribute <1-2% of the CDIRB at
all wavelengths and redshifts, with a strong upper limit of less than 4% of the
total emission. Finally, since electron-positron pair production interactions
with the CDIRB represent the primary source of opacity to very high energy
(VHE: E_\gamma > 1 TeV) \gamma-rays, the model provides predictions for the
optical depth of the Universe to the most energetic photons. We find that these
predictions agree with observations of high-energy cutoffs at TeV energies in
nearby blazars, and suggest that while the Universe is extremely optically
thick at >10 TeV, the next generation of VHE \gamma-ray telescopes can
reasonably expect detections from out to 50-150 Mpc.Comment: 14 pages, 13 figures, submitted to MNRA
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