336 research outputs found
The Evolution of the Fractions of Quiescent and Star-forming Galaxies as a Function of Stellar Mass Since z=3: Increasing Importance of Massive, Dusty Star-forming Galaxies in the Early Universe
Using the UltraVISTA DR1 and 3D-HST catalogs, we construct a
stellar-mass-complete sample, unique for its combination of surveyed volume and
depth, to study the evolution of the fractions of quiescent galaxies,
moderately unobscured star-forming galaxies, and dusty star-forming galaxies as
a function of stellar mass over the redshift interval . We
show that the role of dusty star-forming galaxies within the overall galaxy
population becomes more important with increasing stellar mass, and grows
rapidly with increasing redshift. Specifically, dusty star-forming galaxies
dominate the galaxy population with at . The ratio of dusty and non-dusty star-forming galaxies as
a function of stellar mass changes little with redshift. Dusty star-forming
galaxies dominate the star-forming population at , being a factor of 3-5 more common,
while unobscured star-forming galaxies dominate at . At , red
galaxies dominate the galaxy population at all redshift , either because
they are quiescent (at late times) or dusty star-forming (in the early
universe).Comment: 7 pages, 4 figures, 1 table. Accepted by Astrophysical Journal
Letters after minor revisio
Linear and nonlinear analysis of normal and CAD-affected heart rate signals
Coronary Artery Disease (CAD) is one of the dangerous cardiac disease, often may lead to sudden cardiac death. It is difficult to diagnose CAD by manual inspection of electrocardiogram (ECG) signals. To automate this detection task, in this study, we extracted the Heart Rate (HR) from the ECG signals and used them as base signal for further analysis. We then analyzed the HR signals of both normal and CAD subjects using (i) time domain, (ii) frequency domain and (iii) nonlinear techniques. The following are the nonlinear methods that were used in this work: Poincare plots, Recurrence Quantification Analysis (RQA) parameters, Shannon entropy, Approximate Entropy (ApEn), Sample Entropy (SampEn), Higher Order Spectra (HOS) methods, Detrended Fluctuation Analysis (DFA), Empirical Mode Decomposition (EMD), Cumulants, and Correlation Dimension. As a result of the analysis, we present unique recurrence, Poincare and HOS plots for normal and CAD subjects. We have also observed significant variations in the range of these features with respect to normal and CAD classes, and have presented the same in this paper. We found that the RQA parameters were higher for CAD subjects indicating more rhythm. Since the activity of CAD subjects is less, similar signal patterns repeat more frequently compared to the normal subjects. The entropy based parameters, ApEn and SampEn, are lower for CAD subjects indicating lower entropy (less activity due to impairment) for CAD. Almost all HOS parameters showed higher values for the CAD group, indicating the presence of higher frequency content in the CAD signals. Thus, our study provides a deep insight into how such nonlinear features could be exploited to effectively and reliably detect the presence of CAD
Dialysis solution containing hyaluronan: Effect on peritoneal permeability and inflammation in rats
Dialysis solution containing hyaluronan: Effect on peritoneal permeability and inflammation in rats.BackgroundHyaluronan (HA), a high molecular weight mucopolysaccharide found in interstitial tissues and fluid, is lost from the peritoneal cavity during peritoneal dialysis. In order to determine the role of HA in peritoneal function, we investigated the effects of exogenous HA on peritoneal permeability, markers of intraperitoneal inflammation, and peritoneal morphology in rats exposed to peritoneal dialysis solution for four weeks.MethodsWistar rats were infused intraperitoneally, twice daily, with conventional, hypertonic dialysis solution (Dianeal 3.86%; control) or Dianeal solution containing 10 mg/dL of high molecular weight HA. Peritoneal permeabilities and clearances of solutes and protein were determined using a modified peritoneal permeability test (peritoneal equilibration test) at the beginning and the end of the treatment. Peritoneal volume and ultrafiltration were determined using a macromolecular marker and by gravimetric methods. Peritoneal inflammation was determined by cell counts and differential and by the measurement of cytokine concentrations in the dialysate effluent. Peritoneal thickness and HA content were determined in liver and mesentery biopsies taken at the end of the experiment.ResultsAfter four weeks of exposure to the dialysis solution, transperitoneal protein equilibration was significantly lower in HA-treated rats compared with rats treated with Dianeal alone (46% lower for albumin, P < 0.001; 33% lower for total protein, P < 0.001). The total drained volume after a four hour dwell was 29% higher in the HA group compared with the control (P < 0.001), yielding a positive net ultrafiltration in the HA group versus a negative net ultrafiltration in controls. Peritoneal clearances of urea and creatinine tended to be elevated in HA-treated rats, while clearances of total protein and albumin tended to be lower. Dialysate effluent from rats exposed to HA contained a lower percentage of neutrophils (8.8 ± 6.7 vs. 22.8 ± 9.5%, P < 0.01) and lower levels of the cytokines, tumor necrosis factor-α (11.2 ± 14.7 vs. 42.3 ± 35.3 pg/mL, P < 0.05) and monocyte chemoattractant protein-1 MCP-1 (72.0 ± 86.5 vs. 402.4 ± 258.3 pg/mL, P < 0.02), compared with rats treated with Dianeal alone. The thickness of the peritoneal interstitium showed a similar increase in both groups, but mesenteric tissue from the HA group contained more HA (48%, P < 0.01) than tissue from control animals.ConclusionsThe addition of HA to peritoneal dialysis solution decreases protein permeability, increases ultrafiltration, and decreases cytokine levels and the proportion of peritoneal neutrophils in dialysate from rats exposed to hypertonic dialysis solution. These results suggest that exogenous HA may help to protect the peritoneal membrane during exposure to dialysis solutions. These benefits, if sustained in the clinical setting, could lead to improvements in the therapy of peritoneal dialysis
CDM not dead yet: massive high-z Balmer break galaxies are less common than previously reported
Early JWST observations that targeted so-called double-break sources
(attributed to Lyman and Balmer breaks at ), reported a previously unknown
population of very massive, evolved high-redshift galaxies. This surprising
discovery led to a flurry of attempts to explain these objects' unexpected
existence including invoking alternatives to the standard CDM
cosmological paradigm. To test these early results, we adopted the same
double-break candidate galaxy selection criteria to search for such objects in
the JWST images of the CAnadian NIRISS Unbiased Cluster Survey (CANUCS), and
found a sample of 19 sources over five independent CANUCS fields that cover a
total effective area of arcmin at . However, (1) our SED
fits do not yield exceptionally high stellar masses for our candidates, while
(2) spectroscopy of five of the candidates shows that while all five are at
high redshifts, their red colours are due to high-EW emission lines in
star-forming galaxies rather than Balmer breaks in massive, evolved systems.
Additionally, (3) field-to-field variance leads to differences of
dex in the maximum stellar masses measured in the different fields, suggesting
that the early single-field JWST observations may have suffered from cosmic
variance and/or sample bias. Finally, (4) we show that the presence of even a
single massive outlier can dominate conclusions from small samples such as
those in early JWST observations. In conclusion, we find that the double-break
sources in CANUCS are not sufficiently massive or numerous to warrant
questioning the standard CDM paradigm.Comment: V2: correction of display problem of Fig.1 in Chrome browser.
Submitted to MNRAS, 10 pages (+4 in Appendix), 5 figures (+4), 1 table (+1
The Sparkler: Evolved High-Redshift Globular Clusters Captured by JWST
Using data from JWST, we analyze the compact sources ("sparkles") located
around a remarkable galaxy (the "Sparkler") that is
strongly gravitationally lensed by the galaxy cluster SMACS
J0723.3-7327. Several of these compact sources can be cross-identified in
multiple images, making it clear that they are associated with the host galaxy.
Combining data from JWST's {\em Near-Infrared Camera} (NIRCam) with archival
data from the {\em Hubble Space Telescope} (HST), we perform 0.4-4.4m
photometry on these objects, finding several of them to be very red and
consistent with the colors of quenched, old stellar systems. Morphological fits
confirm that these red sources are spatially unresolved even in strongly
magnified JWST/NIRCam images, while JWST/NIRISS spectra show [OIII]5007
emission in the body of the Sparkler but no indication of star formation in the
red compact sparkles. The most natural interpretation of these compact red
companions to the Sparkler is that they are evolved globular clusters seen at
. Applying \textsc{Dense Basis} SED-fitting to the sample, we infer
formation redshifts of for these globular cluster
candidates, corresponding to ages of Gyr at the epoch of
observation and a formation time just 0.5~Gyr after the Big Bang. If
confirmed with additional spectroscopy, these red, compact "sparkles" represent
the first evolved globular clusters found at high redshift, could be amongst
the earliest observed objects to have quenched their star formation in the
Universe, and may open a new window into understanding globular cluster
formation. Data and code to reproduce our results will be made available at
\faGithub\href{https://niriss.github.io/sparkler.html}{http://canucs-jwst.com/sparkler.html}.Comment: Submitted to ApJL. Comments are welcome. Data and code to reproduce
our results will be made available at niriss.github.io/sparkler.htm
A Steep Decline in the Galaxy Space Density Beyond Redshift 9 in the CANUCS UV Luminosity Function
We present a new sample of 158 galaxies at redshift selected from
deep \jwst\ NIRCam imaging of five widely-separated sightlines in the CANUCS
survey. Two-thirds of the pointings and 80\% of the galaxies are covered by 12
to 14 NIRCam filters, including seven to nine medium bands, providing accurate
photometric redshifts and robustness against low redshift interlopers. A sample
of 28 galaxies at with spectroscopic redshifts shows a low systematic
offset and scatter in the difference between photometric and spectroscopic
redshifts. We derive the galaxy UV luminosity function at redshifts 8 to 12,
finding a slightly higher normalization than previously seen with \hst\ at
redshifts 8 to 10. We observe a steeper decline in the galaxy space density
from to than found by most \jwst\ Cycle 1 studies. In particular, we
find only eight galaxies at and none at , with no
galaxies brighter than F277W AB=28 or in our unmasked,
delensed survey area of 53.4 square arcminutes. We attribute the lack of bright
galaxies in CANUCS compared to GLASS and CEERS to intrinsic variance in
the galaxy density along different sightlines. The evolution in the CANUCS
luminosity function between and is comparable to that predicted by
simulations that assume a standard star formation efficiency, without invoking
any special adjustments.Comment: 30 pages, 12 figures, ApJ, in pres
Gaussian Mixture Model of Heart Rate Variability
Heart rate variability (HRV) is an important measure of sympathetic and parasympathetic functions of the autonomic nervous system and a key indicator of cardiovascular condition. This paper proposes a novel method to investigate HRV, namely by modelling it as a linear combination of Gaussians. Results show that three Gaussians are enough to describe the stationary statistics of heart variability and to provide a straightforward interpretation of the HRV power spectrum. Comparisons have been made also with synthetic data generated from different physiologically based models showing the plausibility of the Gaussian mixture parameters
The near-infrared imager and slitless spectrograph for the James Webb Space Telescope. II. Wide field slitless spectroscopy
We acknowledge support from the Natural Sciences and Engineering Research Council of Canada (NSERC) through a variety of its funding programs. This work is in part supported by Canadian Space Agency grant 18JWSTGTO1. C.P., S.R. and K.V. are supported by the Canadian Space Agency under a contract with NRC Herzberg Astronomy and Astrophysics. K.M. acknowledges funding by the Science and Technology Foundation of Portugal (FCT), grants No. IF/00194/2015, PTDC/FIS-AST/28731/2017, UIDB/00099/2020.We present the wide field slitless spectroscopy mode of the NIRISS instrument on the James Webb Space Telescope. This mode employs two orthogonal low-resolution (resolving power ≈150) grisms in combination with a set of six blocking filters in the wavelength range 0.8–2.3 μm to provide a spectrum of almost every source across the field-of-view. When combined with the low background, high sensitivity and high spatial resolution afforded by the telescope, this mode will enable unprecedented studies of the structure and evolution of distant galaxies. We describe the performance of the as-built hardware relevant to this mode and expected imaging and spectroscopic sensitivity. We discuss operational and calibration procedures to obtain the highest quality data. As examples of the observing mode usage, we present details of two planned Guaranteed Time Observations programs: The Canadian NIRISS Unbiased Cluster Survey and The NIRISS Survey for Young Brown Dwarfs and Rogue Planets.Publisher PDFPeer reviewe
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