219 research outputs found
On the Orbital Period of the New Cataclysmic Variable EUVE J2115-586
We have obtained phase-resolved spectroscopy (3660-6040 Å) of the recently discovered cataclysmic variable EUVE J21 15-586 using the 74-inch telescope at Mount Stromlo Observatory. The radial velocity is modulated over a period of 110.8 min with a possible one-cycle-per-day alias of 102.8 min, and a semiamplitude of ≍270 km s-1 at Hβ and ≍390 km s-1 at He II λ4686. The spectroscopic appearance (H I Balmer, Ca II, He I, He II emission lines), the orbital period, and the velocity amplitude indicate that this cataclysmic variable is probably an AM Her type; the absence of cyclotron humps indicates a low intensity magnetic field (B\u3c20 MG). Extreme ultraviolet emission phased at the orbital period shows evidence of variability, but additional EUV/soft x-ray observations are recommended
Effects of deep brain stimulation frequency on eye movements and cognitive control
Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is an effective treatment for Parkinson's disease (PD). Varying the frequency DBS has differential effects on axial and distal limb functions, suggesting differing modulation of relevant pathways. The STN is also a critical node in oculomotor and associative networks, but the effect of stimulation frequency on these networks remains unknown. This study aimed to investigate the effects of 80 hz vs. 130 Hz frequency STN-DBS on eye movements and executive control. Twenty-one STN-DBS PD patients receiving 130 Hz vs. 80 Hz stimulation were compared to a healthy control group (n = 16). All participants were tested twice in a double-blind manner. We examined prosaccades (latency and gain) and antisaccades (latency of correct and incorrect antisaccades, error rate and gain of the correct antisaccades). Executive function was tested with the Stroop task. The motor condition was assessed using Unified Parkinson's Disease Rating Scale part III. The antisaccadic error rate was higher in patients (p = 0.0113), more so in patients on 80 Hz compared to 130 Hz (p = 0.001) stimulation. The differences between patients and controls and between frequencies for all other eye-movements or cognitive measures were not statistically significant. We show that 80 Hz STN-DBS in PD reduces the ability to maintain stable fixation but does not alter inhibition, resulting in a higher antisaccade error rate presumably due to less efficient fixation, without altering the motor state. This provides a wider range of stimulation parameters that can reduce specific DBS-related effects without affecting motor outcomes
Does race impact functional outcomes in patients undergoing robotic partial nephrectomy?
Background: The role of race on functional outcomes after robotic partial nephrectomy (RPN) is still a matter of debate. We aimed to evaluate the clinical and pathologic characteristics of African American (AA) and Caucasian patients who underwent RPN and analyzed the association between race and functional outcomes.
Methods: Data was obtained from a multi-institutional database of patients who underwent RPN in 6 institutions in the USA. We identified 999 patients with complete clinical data. Sixty-three patients (6.3%) were AA, and each patient was matched (1:3) to Caucasian patients by age at surgery, gender, Charlson Comorbidity Index (CCI) and renal score. Bivariate and multivariate logistic regression analyses were used to evaluate predictors of acute kidney injury (AKI). Kaplan-Meier method and multivariable semiparametric Cox regression analyses were performed to assess prevalence and predictors of significant eGFR reduction during follow-up.
Results: Overall, 252 patients were included. AA were more likely to have hypertension (58.7%
Conclusions: Although African American patients were more likely to have hypertension, renal function outcomes of robotic partial nephrectomies were not significantly different when stratified by race. However, future studies with larger cohorts are necessary to validate these findings
Cosmic biology in perspective
Abstract: A series of astronomical observations obtained over the period 1986 to 2018 supports the idea that life is a cosmic rather than a purely terrestrial or planetary phenomenon. These include (1) the detection of biologically relevant molecules in interstellar clouds and in comets, (2) mid-infrared spectra of interstellar grains and the dust from comets, (3) a diverse set of data from comets including the Rosetta mission showing consistency with biology and (4) the frequency of Earth-like or habitable planets in the Galaxy. We argue that the conjunction of all the available data suggests the operation of cometary biology and interstellar panspermia rather than the much weaker hypothesis of comets being only the source of the chemical building blocks of life. We conclude with specific predictions on the properties expected of extra-terrestrial life if it is discovered on Enceladus, Europa or beyond. A radically different biochemistry elsewhere can be considered as a falsification of the theory of interstellar panspermia
Reionization with star-forming galaxies: insights from the Low-z Lyman Continuum Survey
The fraction of ionizing photons escaping from galaxies, , is at the
same time a crucial parameter in modelling reionization and a very poorly known
quantity, especially at high redshift. Recent observations are starting to
constrain the values of in low-z star-forming galaxies, but the
validity of this comparison remains to be verified. Applying at high-z the
empirical relation between and the UV slope trends derived from the
Low-z Lyman Continuum Survey, we use the DELPHI semi-analytical galaxy
formation model to estimate the global ionizing emissivity of high-z galaxies,
which we use to compute the resulting reionization history. We find that both
the global ionizing emissivity and reionization history match the observational
constraints. Assuming that the low-z correlations hold during the epoch of
reionization, we find that galaxies with
are the main drivers of reionization. We derive a population-averaged at z=4.5, 6, 8.Comment: 5+1 page, 3 figures, submitted to A&
Quantifying the Effects of Known Unknowns on Inferred High-redshift Galaxy Properties: Burstiness, the IMF, and Nebular Physics
The era of the James Webb Space Telescope ushers stellar populations models
into uncharted territories, particularly at the high-redshift frontier. In a
companion paper, we apply the \texttt{Prospector} Bayesian framework to jointly
infer galaxy redshifts and stellar populations properties from broad-band
photometry as part of the UNCOVER survey. Here we present a comprehensive error
budget in spectral energy distribution (SED) modeling. Using a
sample, we quantify the systematic shifts stemming from various model choices
in inferred stellar mass, star formation rate (SFR), and age. These choices
encompass different timescales for changes in the star formation history (SFH),
non-universal stellar initial mass functions (IMF), and the inclusion of
variable nebular abundances, gas density and ionizing photon budget. We find
that the IMF exerts the strongest influence on the inferred properties: the
systematic uncertainties can be as much as 1 dex, 2--5 times larger than the
formal reported uncertainties in mass and SFR; and importantly, exceed the
scatter seen when using different SED fitting codes. This means that a common
practice in the literature of assessing uncertainties in SED-fitting processes
by comparing multiple codes is substantively underestimating the true
systematic uncertainty. Highly stochastic SFHs change the inferred SFH by much
larger than the formal uncertainties, and introduce dex systematics
in SFR and dex systematics in average age. Finally, employing a
flexible nebular emission model causes dex systematic increase in
mass, comparable to the formal uncertainty. This paper constitutes one of the
initial steps toward a complete uncertainty estimate in SED modeling.Comment: Submitted to ApJ. 18 pages, 8 figures, 2 table
UNCOVERing the extended strong lensing structures of Abell 2744 with the deepest JWST imaging
We present a new parametric lens model for the massive galaxy cluster
Abell~2744 based on the new ultra-deep JWST imaging taken in the framework of
the UNCOVER program. These observations constitute the deepest JWST images of a
lensing cluster to date, adding to the existing deep Hubble Space Telescope
(HST) images and the recent JWST ERS and DDT data taken for this field. The
wide field-of-view of UNCOVER ( arcmin) extends beyond the
cluster's well-studied central core and reveals a spectacular wealth of
prominent lensed features around two massive cluster sub-structures in the
north and north-west, where no multiple images were previously known. The 75
newly uncovered multiple images and candidates of 16 sources allow us, for the
first time, to constrain the lensing properties and total mass distribution
around these extended cluster structures using strong lensing (SL). Our model
yields an effective Einstein radius of for
the main cluster core (for ), enclosing a mass of
M, and
for the newly discovered north-western SL
structure enclosing
M. The northern clump is somewhat less massive with
enclosing
M. We find the
northern sub-structures of Abell~2744 to broadly agree with the findings from
weak lensing (WL) and align with the filamentary structure found by these
previous studies. Our model in particular reveals a large area of high
magnifications between the various cluster structures, which will be paramount
for lensed galaxy studies in the UNCOVER field. The model is made publicly
available to accompany the first UNCOVER data release.Comment: Accepted for publication in MNRAS. Updated to match the published
versio
JWST UNCOVER: Discovery of Galaxy Candidates Behind the Lensing Cluster Abell 2744
We present the results of a search for high-redshift () galaxy
candidates in the JWST UNCOVER survey, using deep NIRCam and NIRISS imaging in
7 bands over arcmin and ancillary HST observations. The NIRCam
observations reach a limiting magnitude of AB. The
identification of high candidates relies on a combination of a dropout
selection and photometric redshifts. We find 16 candidates at and 3
candidates at , eight candidates are deemed very robust. Their lensing
amplification ranges from to 11.5. Candidates have a wide range of
(lensing-corrected) luminosities and young ages, with low stellar masses
( log(M/M) ) and low star formation rates
(SFR=0.2-7 M yr), confirming previous findings in early JWST
observations of . A few galaxies at appear to show a clear
Balmer break between the F356W and F444W/F410M bands, which helps constrain
their stellar mass. We estimate blue UV continuum slopes between
and , typical for early galaxies at but not as extreme as the
bluest recently discovered sources. We also find evidence for a rapid
redshift-evolution of the mass-luminosity relation and a redshift-evolution of
the UV continuum slope for a given range of intrinsic magnitude, in line with
theoretical predictions. These findings suggest that deeper JWST observations
are needed to reach the fainter galaxy population at those early epochs, and
follow-up spectroscopy will help better constrain the physical properties and
star formation histories of a larger sample of galaxies.Comment: Submitted to MNRA
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