183 research outputs found
Probing the missing baryons with the Sunyaev-Zel'dovich effect from filaments
Observations of galaxies and galaxy clusters in the local universe can
account for only of the total baryon content. Cosmological
simulations predict that the `missing baryons' are spread throughout
filamentary structures in the cosmic web, forming a low-density gas with
temperatures of K. We search for this warm-hot intergalactic
medium (WHIM) by stacking the Planck Compton -parameter map of the thermal
Sunyaev-Zel'dovich (tSZ) effect for 1,002,334 pairs of CMASS galaxies from the
Sloan Digital Sky Survey. We model the contribution from the galaxy halo pairs
assuming spherical symmetry, finding a residual tSZ signal at the
2.9\mbox{\sigma} level from a stacked filament of length with a Compton parameter magnitude . We
consider possible sources of contamination and conclude that bound gas in
haloes may contribute only up to of the measured filamentary signal. To
estimate the filament gas properties we measure the gravitational lensing
signal for the same sample of galaxy pairs; in combination with the tSZ signal,
this yields an inferred gas density of with a temperature K. This result is consistent with the predicted WHIM properties, and
overall the filamentary gas can account for of the total baryon
content of the Universe. We also see evidence that the gas filament extends
beyond the galaxy pair. Averaging over this longer baseline boosts the
significance of the tSZ signal and increases the associated baryon content to
of the global value.Comment: 13 pages, 8 figures; accepted for publication in A&
Galaxy And Mass Assembly (GAMA): Stellar-to-Dynamical Mass Relation I. Constraining the Precision of Stellar Mass Estimates
In this empirical work, we aim to quantify the systematic uncertainties in
stellar mass estimates made from spectral energy distribution (SED)
fitting through stellar population synthesis (SPS), for galaxies in the local
Universe, by using the dynamical mass estimator as an
SED-independent check on stellar mass. We first construct a statistical model
of the high dimensional space of galaxy properties; size , velocity
dispersion , surface brightness , mass-to-light ratio
, rest-frame colour, S\'ersic index and dynamical mass
; accounting for selection effects and covariant errors. We
disentangle the correlations among galaxy properties and find that the
variation in is driven by , S\'ersic index and
colour. We use these parameters to calibrate an SED-independent
estimator, . We find the random scatter of the relation
to be and for
quiescent and star-forming galaxies respectively. Finally, we inspect the
residuals as a function of SPS parameters (dust, age, metallicity, star
formation rate) and spectral indices (H, H, . For
quiescent galaxies, of the scatter can be explained by the
uncertainty in SPS parameters, with dust and age being the largest sources of
uncertainty. For star-forming galaxies, while age and metallicity are the
leading factors, SPS parameters account for only of the scatter.
These results leave us with remaining unmodelled scatters of
and for quiescent and star-forming galaxies respectively.
This can be interpreted as a conservative limit on the precision in
that can be achieved via simple SPS-modelling.Comment: Accepted for publication in the Astrophysical Journal on 14 June 202
A comparison of ultrafast and conventional spectral Doppler ultrasound to measure cerebral blood flow velocity during inguinal hernia repair in infants
Background: Ultrafast cerebral Doppler ultrasound enables simultaneous quantification and visualization of cerebral blood flow velocity. The aim of this study is to compare the use of conventional and ultrafast spectral Doppler during anesthesia and their potential to show the effect of anesthesiologic procedures on cerebral blood flow velocities, in relation to blood pressure and cerebral oxygenation in infants undergoing inguinal hernia repair. Methods: A single-center prospective observational cohort study in infants up to six months of age. We evaluated conventional and ultrafast spectral Doppler cerebral ultrasound measurements in terms of number of successful measurements during the induction of anesthesia, after sevoflurane induction, administration of caudal analgesia, a fluid bolus and emergence of anesthesia. Cerebral blood flow velocity was quantified in pial arteries using conventional spectral Doppler and in the cerebral cortex using ultrafast Doppler by peak systolic velocity, end diastolic velocity and resistivity index.Results: Twenty infants were included with useable conventional spectral Doppler images in 72/100 measurements and ultrafast Doppler images in 51/100 measurements. Intraoperatively, the success rates were 53/60 (88.3%) and 41/60 (68.3%), respectively. Cerebral blood flow velocity increased after emergence for both conventional (end diastolic velocity, from 2.01 to 2.75 cm/s, p < 0.001) and ultrafast spectral Doppler (end diastolic velocity, from 0.59 to 0.94 cm/s), whereas cerebral oxygenation showed a reverse pattern with a decrease after the emergence of the infant (85% to 68%, p < 0.001). Conclusion: It is possible to quantify cortical blood flow velocity during general anesthesia using conventional and ultrafast spectral Doppler cerebral ultrasound. Cerebral blood flow velocity and blood pressure decreased, while regional cerebral oxygenation increased during general anesthesia. Ultrafast spectral Doppler ultrasound offers novel insights into perfusion within the cerebral cortex, unattainable through conventional spectral ultrasound. Yet, ultrafast Doppler is curtailed by a lower success rate and a more rigorous learning curve compared to conventional method.</p
A comparison of ultrafast and conventional spectral Doppler ultrasound to measure cerebral blood flow velocity during inguinal hernia repair in infants
Background: Ultrafast cerebral Doppler ultrasound enables simultaneous quantification and visualization of cerebral blood flow velocity. The aim of this study is to compare the use of conventional and ultrafast spectral Doppler during anesthesia and their potential to show the effect of anesthesiologic procedures on cerebral blood flow velocities, in relation to blood pressure and cerebral oxygenation in infants undergoing inguinal hernia repair. Methods: A single-center prospective observational cohort study in infants up to six months of age. We evaluated conventional and ultrafast spectral Doppler cerebral ultrasound measurements in terms of number of successful measurements during the induction of anesthesia, after sevoflurane induction, administration of caudal analgesia, a fluid bolus and emergence of anesthesia. Cerebral blood flow velocity was quantified in pial arteries using conventional spectral Doppler and in the cerebral cortex using ultrafast Doppler by peak systolic velocity, end diastolic velocity and resistivity index.Results: Twenty infants were included with useable conventional spectral Doppler images in 72/100 measurements and ultrafast Doppler images in 51/100 measurements. Intraoperatively, the success rates were 53/60 (88.3%) and 41/60 (68.3%), respectively. Cerebral blood flow velocity increased after emergence for both conventional (end diastolic velocity, from 2.01 to 2.75 cm/s, p < 0.001) and ultrafast spectral Doppler (end diastolic velocity, from 0.59 to 0.94 cm/s), whereas cerebral oxygenation showed a reverse pattern with a decrease after the emergence of the infant (85% to 68%, p < 0.001). Conclusion: It is possible to quantify cortical blood flow velocity during general anesthesia using conventional and ultrafast spectral Doppler cerebral ultrasound. Cerebral blood flow velocity and blood pressure decreased, while regional cerebral oxygenation increased during general anesthesia. Ultrafast spectral Doppler ultrasound offers novel insights into perfusion within the cerebral cortex, unattainable through conventional spectral ultrasound. Yet, ultrafast Doppler is curtailed by a lower success rate and a more rigorous learning curve compared to conventional method.</p
Less is less: photometry alone cannot predict the observed spectral indices of galaxies from the LEGA-C spectroscopic survey
We test whether we can predict optical spectra from deep-field photometry of
distant galaxies. Our goal is to perform a comparison in data space,
highlighting the differences between predicted and observed spectra. The Large
Early Galaxy Astrophysics Census (LEGA-C) provides high-quality optical spectra
of thousands of galaxies at redshift . Broad-band photometry of the
same galaxies, drawn from the recent COSMOS2020 catalog, is used to predict the
optical spectra with the spectral energy distribution (SED) fitting code
Prospector and the MILES stellar library. The observed and predicted spectra
are compared in terms of two age and metallicity-sensitive absorption features
(H and Fe4383). The global bimodality of star-forming and
quiescent galaxies in photometric space is recovered with the model spectra.
But the presence of a systematic offset in the Fe4383 line strength and the
weak correlation between the observed and modeled line strength imply that
accurate age or metallicity determinations cannot be inferred from photometry
alone. For now we caution that photometry-based estimates of stellar population
properties are determined mostly by the modeling approach and not the physical
properties of galaxies, even when using the highest-quality photometric
datasets and state-of-the-art fitting techniques. When exploring a new physical
parameter space (i.e. redshift or galaxy mass) high-quality spectroscopy is
always needed to inform the analysis of photometry.Comment: 13 pages, 8 figures, accepted 26 October 202
What endocrinologists can do to prevent cardiovascular complications in adults with Prader-Willi syndrome:Lessons from a case series
Context: Prader-Willi syndrome (PWS) is a complex rare genetic syndrome. Mortality in patients with PWS is 3% per year. In nearly half of the patients, the cause of death is of cardiopulmonary origin. Prevention, diagnosis and treatment of cardiovascular (CV) disease in PWS adults is complicated by the behavioral phenotype, reduced ability to express physical complaints, high pain threshold and obesity. Objective: To describe the challenges in prevention, diagnosis and treatment of CV disease in PWS adults, in order to increase awareness and improve medical care. Methods: Retrospective study of medical records of adults visiting the Dutch PWS reference center. Results: We describe the challenges encountered during diagnosis and treatment of four PWS adults with heart failure. All had pre-existent peripheral edema. CV risk factors in these patients were obesity (n=4), type 2 diabetes mellitus (n=2), hypertension (n=2), hypogonadism (n=3) and sleep apnea (n=2). Remarkably, all patients were younger than 40 years during their first cardiac decompensation. All patients presented with progressive shortness of breath and/or orthopnea and progressive pitting edema. In 117 controls with PWS without CV problems, 31% had leg edema. Conclusion: Diagnosing CV problems in PWS adults is challenging. Peripheral edema is common in PWS adults without CV morbidity, which makes edema in general a poor marker for heart failure. However, when edema is of the pitting kind and progressive, this is a strong predictor of cardiac decompensation. We provide practical recommendations for diagnosing and treating CV problems in this vulnerable patient population.</p
Pericentrosomal targeting of Rab6 secretory vesicles by Bicaudal-D-related protein 1 (BICDR-1) regulates neuritogenesis
Membrane and secretory trafficking are essential for proper neuronal development. However, the molecular mechanisms that organize secretory trafficking are poorly understood. Here, we identify Bicaudal-D-related protein 1 (BICDR-1) as an effector of the small GTPase Rab6 and key component of the molecular machinery that controls secretory vesicle transport in developing neurons. BICDR-1 interacts with kinesin motor Kif1C, the dynein/dynactin retrograde motor complex, regulates the pericentrosomal localization of Rab6-positive secretory vesicles and is required for neural development in zebrafish. BICDR-1 expression is high during early neuronal development and strongly declines during neurite outgrowth. In young neurons, BICDR-1 accumulates Rab6 secretory vesicles around the centrosome, restricts anterograde secretory transport and inhibits neuritogenesis. Later during development, BICDR-1 expression is strongly reduced, which permits anterograde secretory transport required for neurite outgrowth. These results indicate an important role for BICDR-1 as temporal regulator of secretory trafficking during the early phase of neuronal differentiation
Stellar Half-Mass Radii of Galaxies: Comparison with JWST/NIRCam Half-Light Radii
We use CEERS JWST/NIRCam imaging to measure rest-frame near-IR light profiles
of 500 galaxies in the redshift range .
We compare the resulting rest-frame 1.5-2m half-light radii
() with stellar half-mass radii (\rmass) derived with multi-color
light profiles from CANDELS HST imaging. In general agreement with previous
work, we find that and \rmass~are up to 40\%~smaller than the
rest-frame optical half-light radius . The agreement between
and \rmass~is excellent, with negligible systematic offset
(0.03 dex) up to for quiescent galaxies and up to for
star-forming galaxies. We also deproject the profiles to estimate \rmassd, the
radius of a sphere containing 50\% of the stellar mass. We present the
distribution of galaxies at , comparing ,
\rmass~and \rmassd. The slope is significantly flatter for \rmass~and \rmassd~
compared to , mostly due to downward shifts in size for massive
star-forming galaxies, while \rmass~and \rmassd~do not show markedly different
trends. Finally, we show rapid size evolution ()
for massive () quiescent galaxies between and
, again comparing , \rmass~and \rmassd. We conclude that
the main tenets of the size evolution narrative established over the past 20
years, based on rest-frame optical light profile analysis, still hold in the
era of JWST/NIRCam observations in the rest-frame near-IR.Comment: Submitted to ApJ. Comments welcom
Malignancies in Prader-Willi Syndrome:Results From a Large International Cohort and Literature Review
CONTEXT: Prader-Willi syndrome (PWS) is a complex disorder combining hypothalamic dysfunction, neurodevelopmental delay, hypotonia, and hyperphagia with risk of obesity and its complications. PWS is caused by the loss of expression of the PWS critical region, a cluster of paternally expressed genes on chromosome 15q11.2-q13. As life expectancy of patients with PWS increases, age-related diseases like malignancies might pose a new threat to health. OBJECTIVE: To investigate the prevalence and risk factors of malignancies in patients with PWS and to provide clinical recommendations for cancer screening. METHODS: We included 706 patients with PWS (160 children, 546 adults). We retrospectively collected data from medical records on past or current malignancies, the type of malignancy, and risk factors for malignancy. Additionally, we searched the literature for information about the relationship between genes on chromosome 15q11.2-q13 and malignancies. RESULTS: Seven adults (age range, 18-55 years) had been diagnosed with a malignancy (acute lymphoblastic leukemia, intracranial hemangiopericytoma, melanoma, stomach adenocarcinoma, biliary cancer, parotid adenocarcinoma, and colon cancer). All patients with a malignancy had a paternal 15q11-13 deletion. The literature review showed that several genes on chromosome 15q11.2-q13 are related to malignancies. CONCLUSION: Malignancies are rare in patients with PWS. Therefore, screening for malignancies is only indicated when clinically relevant symptoms are present, such as unexplained weight loss, loss of appetite, symptoms suggestive of paraneoplastic syndrome, or localizing symptoms. Given the increased cancer risk associated with obesity, which is common in PWS, participation in national screening programs should be encouraged.</p
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