387 research outputs found
The modified dynamics (MOND) predicts an absolute maximum to the acceleration produced by `dark halos'
We have recently discovered that the modified dynamics (MOND) implies some
universal upper bound on the acceleration that can be contributed by a `dark
halo'--assumed in a Newtonian analysis to account for the effects of MOND. Not
surprisingly, the limit is of the order of the acceleration constant of the
theory. This can be contrasted directly with the results of structure-formation
simulations. The new limit is substantial and different from earlier MOND
acceleration limits (discussed in connection with the MOND explanation of the
Freeman law for galaxy disks, and the Fish law for ellipticals): It pertains to
the `halo', and not to the observed galaxy; it is absolute, and independent of
further physical assumptions on the nature of the galactic system; and it
applies at all radii, whereas the other limits apply only to the mean
acceleration in the system.Comment: Latex, five pages, final version to be published in Astrophys. J.
Let
First Results from the KMOS Lens-Amplified Spectroscopic Survey (KLASS): Kinematics of Lensed Galaxies at Cosmic Noon
We present the first results of the KMOS Lens-Amplified Spectroscopic Survey
(KLASS), a new ESO Very Large Telescope (VLT) large program, doing multi-object
integral field spectroscopy of galaxies gravitationally lensed behind seven
galaxy clusters selected from the HST Grism Lens-Amplified Survey from Space
(GLASS). Using the power of the cluster magnification we are able to reveal the
kinematic structure of 25 galaxies at , in four
cluster fields, with stellar masses . This sample includes 5 sources at with lower stellar masses
than in any previous kinematic IFU surveys. Our sample displays a diversity in
kinematic structure over this mass and redshift range. The majority of our
kinematically resolved sample is rotationally supported, but with a lower ratio
of rotational velocity to velocity dispersion than in the local universe,
indicating the fraction of dynamically hot disks changes with cosmic time. We
find no galaxies with stellar mass in our sample
display regular ordered rotation. Using the enhanced spatial resolution from
lensing, we resolve a lower number of dispersion dominated systems compared to
field surveys, competitive with findings from surveys using adaptive optics. We
find that the KMOS IFUs recover emission line flux from HST grism-selected
objects more faithfully than slit spectrographs. With artificial slits we
estimate slit spectrographs miss on average 60% of the total flux of emission
lines, which decreases rapidly if the emission line is spatially offset from
the continuum.Comment: Accepted for publication in Ap
A QUMOND galactic N-body code I: Poisson solver and rotation curve fitting
Here we present a new particle-mesh galactic N-body code that uses the full
multigrid algorithm for solving the modified Poisson equation of the Quasi
Linear formulation of Modified Newtonian Dynamics (QUMOND). A novel approach
for handling the boundary conditions using a refinement strategy is implemented
and the accuracy of the code is compared with analytical solutions of Kuzmin
disks. We then employ the code to compute the predicted rotation curves for a
sample of five spiral galaxies from the THINGS sample. We generated static
N-body realisations of the galaxies according to their stellar and gaseous
surface densities and allowed their distances, mass-to-light ratios (M/L) and
both the stellar and gas scale-heights to vary in order to estimate the best
fit parameters. We found that NGC 3621, NGC 3521 and DDO 154 are well fit by
MOND using expected values of the distance and M/L. NGC 2403 required a
moderately larger than expected and NGC 2903 required a substantially
larger value. The surprising result was that the scale-height of the dominant
baryonic component was well constrained by the rotation curves: the gas
scale-height for DDO 154 and the stellar scale-height for the others. In fact,
if the suggested stellar scale-height (one-fifth the stellar scale-length) was
used in the case of NGC 3621 and NGC 3521 it would not be possible to produce a
good fit to the inner rotation curve. For each of the four stellar dominated
galaxies, we calculated the vertical velocity dispersions which we found to be,
on the whole, quite typical compared with observed stellar vertical velocity
dispersions of face on spirals. We conclude that modelling the gas
scale-heights of the gas rich dwarf spiral galaxies will be vital in order to
make precise conclusions about MOND.Comment: 14 pages, 11 figures, MNRAS in pres
MOND and the Universal Rotation Curve: similar phenomenologies
The Modified Newtonian Dynamics (MOND) and the Universal Rotation Curve (URC)
are two ways to describe the general properties of rotation curves, with very
different approaches concerning dark matter and gravity. Phenomenological
similarities between the two approaches are studied by looking for properties
predicted in one framework that are also reproducible in the other one. First,
we looked for the analogous of the URC within the MOND framework. Modifying in
an observationally-based way the baryonic contribution Vbar to the rotation
curve predicted by the URC, and applying the MOND formulas to this Vbar, leads
to a "MOND URC" whose properties are remarkably similar to the URC. Second, it
is shown that the URC predicts a tight mass discrepancy - acceleration
relation, which is a natural outcome of MOND. With the choice of Vbar that
minimises the differences between the URC and the "MOND URC" the relation is
almost identical to the observational one. This similarity between the
observational properties of MOND and the URC has no implications about the
validity of MOND as a theory of gravity, but it shows that it can reproduce in
detail the phenomenology of disk galaxies' rotation curves, as described by the
URC. MOND and the URC, even though they are based on totally different
assumptions, are found to have very similar behaviours and to be able to
reproduce each other's properties fairly well, even with the simple assumptions
made on the luminosity dependence of the baryonic contribution to the rotation
curve.Comment: Accepted for publication in ApJ. 8 pages, 5 figure
Association of perinatal sentinel events, placental pathology and cerebral MRI in neonates with hypoxic-ischemic encephalopathy receiving therapeutic hypothermia
OBJECTIVE: Placental pathology might provide information on the etiology of hypoxic-ischemic encephalopathy (HIE). To evaluate the association of perinatal sentinel events (PSE), placental pathology and cerebral MRI in cooled neonates with moderate/severe HIE.
STUDY DESIGN: Retrospective analysis of 52 neonates with HIE registered in the Swiss National Asphyxia and Cooling Register 2011-2019. PSE and Non-PSE groups were tested for association with placental pathology. Placental pathology categories were correlated with MRI scores.
RESULTS: In total, 14/52 neonates (27%) had a PSE, 38 neonates (73%) did not have a PSE. There was no evidence for an association of occurrence of PSE and placental pathologies (p = 0.364). Neonates with high MRI scores tended to have more often chronic pathologies in their placentas than acute pathologies or normal placentas (p = 0.067).
CONCLUSION: Independent of the occurrence of PSE, chronic placental pathologies might be associated with more severe brain injury and needs further study
Milky Way Mass Models and MOND
Using the Tuorla-Heidelberg model for the mass distribution of the Milky Way,
I determine the rotation curve predicted by MOND. The result is in good
agreement with the observed terminal velocities interior to the solar radius
and with estimates of the Galaxy's rotation curve exterior thereto. There are
no fit parameters: given the mass distribution, MOND provides a good match to
the rotation curve. The Tuorla-Heidelberg model does allow for a variety of
exponential scale lengths; MOND prefers short scale lengths in the range 2.0 to
2.5 kpc. The favored value of scale length depends somewhat on the choice of
interpolation function. There is some preference for the `simple' interpolation
function as found by Famaey & Binney. I introduce an interpolation function
that shares the advantages of the simple function on galaxy scales while having
a much smaller impact in the solar system. I also solve the inverse problem,
inferring the surface mass density distribution of the Milky Way from the
terminal velocities. The result is a Galaxy with `bumps and wiggles' in both
its luminosity profile and rotation curve that are reminiscent of those
frequently observed in external galaxies.Comment: Accepted for publication in the Astrophysical Journal. 31 pages
including 8 figures and 3 table
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A phase II study of temozolomide vs. procarbazine in patients with glioblastoma multiforme at first relapse.
A randomized, multicentre, open-label, phase II study compared temozolomide (TMZ), an oral second-generation alkylating agent, and procarbazine (PCB) in 225 patients with glioblastoma multiforme at first relapse. Primary objectives were to determine progression-free survival (PFS) at 6 months and safety for TMZ and PCB in adult patients who failed conventional treatment. Secondary objectives were to assess overall survival and health-related quality of life (HRQL). TMZ was given orally at 200 mg/m(2)/day or 150 mg/m(2)/day (prior chemotherapy) for 5 days, repeated every 28 days. PCB was given orally at 150 mg/m(2)/day or 125 mg/m(2)/day (prior chemotherapy) for 28 days, repeated every 56 days. HRQL was assessed using the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire (EORTC QLQ-C30 [+3]) and the Brain Cancer Module 20 (BCM20). The 6-month PFS rate for patients who received TMZ was 21%, which met the protocol objective. The 6-month PFS rate for those who received PCB was 8% (P = 0.008, for the comparison). Overall PFS significantly improved with TMZ, with a median PFS of 12.4 weeks in the TMZ group and 8.32 weeks in the PCB group (P = 0.0063). The 6-month overall survival rate for TMZ patients was 60% vs. 44% for PCB patients (P = 0.019). Freedom from disease progression was associated with maintenance of HRQL, regardless of treatment received. TMZ had an acceptable safety profile; most adverse events were mild or moderate in severity
Dyspnea in Patients Receiving Radical Radiotherapy for Non-Small Cell Lung Cancer: A Prospective Study
Background and Purpose: Dyspnea is an important symptomatic endpoint for
assessment of radiation-induced lung injury (RILI) following radical radiotherapy in
locally advanced disease, which remains the mainstay of treatment at the time of
significant advances in therapy including combination treatments with immunotherapy
and chemotherapy and the use of local ablative radiotherapy techniques. We investigated
the relationship between dose-volume parameters and subjective changes in dyspnea as
a measure of RILI and the relationship to spirometry.
Material and Methods: Eighty patients receiving radical radiotherapy for non-small cell
lung cancer were prospectively assessed for dyspnea using two patient-completed tools:
EORTC QLQ-LC13 dyspnea quality of life assessment and dyspnea visual analogue scale
(VAS). Global quality of life, spirometry and radiation pneumonitis grade were also
assessed. Comparisons were made with lung dose-volume parameters.
Results: The median survival of the cohort was 26 months. In the evaluable group of 59
patients there were positive correlations between lung dose-volume parameters and a
change in dyspnea quality of life scale at 3 months (V30 p=0.017; V40 p=0.026; V50
p=0.049; mean lung dose p=0.05), and a change in dyspnea VAS at 6 months (V30
p=0.05; V40 p=0.026; V50 p=0.028) after radiotherapy. Lung dose-volume parameters
predicted a 10% increase in dyspnea quality of life score at 3 months (V40; p=0.041, V50;
p=0.037) and dyspnea VAS score at 6 months (V40; p=0.027) post-treatment.
Conclusions: Worsening of dyspnea is an important symptom of RILI. We demonstrate a
relationship between lung dose-volume parameters and a 10% worsening of subjectiv
Constraining Lyman-alpha spatial offsets at from VANDELS slit spectroscopy
We constrain the distribution of spatially offset Lyman-alpha emission
(Ly) relative to rest-frame ultraviolet emission in high
redshift () Lyman-break galaxies (LBGs) exhibiting Ly emission
from VANDELS, a VLT/VIMOS slit-spectroscopic survey of the CANDELS Ultra Deep
Survey and Chandra Deep Field South fields (
total). Because slit spectroscopy compresses two-dimensional spatial
information into one spatial dimension, we use Bayesian inference to recover
the underlying Ly spatial offset distribution. We model the
distribution using a 2D circular Gaussian, defined by a single parameter
, the standard deviation expressed in polar
coordinates. Over the entire redshift range of our sample (), we find
kpc ( conf.),
corresponding to arcsec at . We also find that
decreases significantly with redshift. Because
Ly spatial offsets can cause slit-losses, the decrease in
with redshift can partially explain the increase
in the fraction of Ly emitters observed in the literature over this
same interval, although uncertainties are still too large to reach a strong
conclusion. If continues to decrease into the
reionization epoch, then the decrease in Ly transmission from galaxies
observed during this epoch might require an even higher neutral hydrogen
fraction than what is currently inferred. Conversely, if spatial offsets
increase with the increasing opacity of the IGM, slit losses may explain some
of the drop in Ly transmission observed at . Spatially resolved
observations of Ly and UV continuum at are needed to settle the
issue.Comment: Submitted to MNRA
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