909 research outputs found
Autler-Townes splitting in two-color photoassociation of 6Li
We report on high-resolution two-color photoassociation spectroscopy in the
triplet system of magneto-optically trapped 6Li. The absolute transition
frequencies have been measured. Strong optical coupling of the bound molecular
states has been observed as Autler-Townes splitting in the photoassociation
signal. The spontaneous bound-bound transition rate is determined and the
molecule formation rate is estimated. The observed lineshapes are in good
agreement with the theoretical model.Comment: 5 pages, 4 figures, accepted for publication in Phys. Rev. A (Rapid
Communication
Long range scattering resonances in strong-field seeking states of polar molecules
We present first steps toward understanding the ultracold scattering
properties of polar molecules in strong electric field-seeking states. We have
found that the elastic cross section displays a quasi-regular set of potential
resonances as a function of the electric field, which potentially offers
intimate details about the inter-molecular interaction. We illustrate these
resonances in a ``toy'' model composed of pure dipoles, and in more physically
realistic systems. To analyze these resonances, we use a simple WKB
approximation to the eigenphase, which proves both reasonably accurate and
meaningful. A general treatment of the Stark effect and dipolar interactions is
also presented
A New Version of Reimers' law of Mass Loss Based on a Physical Approach
We present a new semi-empirical relation for the mass loss of cool stellar
winds, which so far has frequently been described by "Reimers' law".
Originally, this relation was based solely on dimensional scaling arguments
without any physical interpretation. In our approach, the wind is assumed to
result from the spill-over of the extended chromosphere, possibly associated
with the action of waves, especially Alfven waves, which are used as guidance
in the derivation of the new formula. We obtain a relation akin to the original
Reimers law, but which includes two new factors. They reflect how the
chromospheric height depends on gravity and how the mechanical energy flux
depends, mainly, on effective temperature. The new relation is tested and
sensitively calibrated by modelling the blue end of the Horizontal Branch of
globular clusters. The most significant difference from mass loss rates
predicted by the Reimers relation is an increase by up to a factor of 3 for
luminous late-type (super-)giants, in good agreement with observations.Comment: 12 pages, 4 figures, accepted by ApJ Letter
Flaring Up All Over -- Radio Activity in Rapidly-Rotating Late-Type M and L Dwarfs
We present Very Large Array observations of twelve late M and L dwarfs in the
Solar neighborhood. The observed sources were chosen to cover a wide range of
physical characteristics - spectral type, rotation, age, binarity, and X-ray
and H\alpha activity - to determine the role of these properties in the
production of radio emission, and hence magnetic fields. Three of the twelve
sources, TVLM513-46546, 2MASS J0036159+182110, and BRI0021-0214, were observed
to flare and also exhibit persistent emission, indicating that magnetic
activity is not quenched at the bottom of the main sequence. The radio emission
extends to spectral type L3.5, and there is no apparent decrease in the ratio
of flaring luminosities to bolometric luminosities between M8-L3.5. Moreover,
contrary to the significant drop in persistent H\alpha activity beyond spectral
type M7, the persistent radio activity appears to steadily increase between
M3-L3.5. Similarly, the radio emission from BRI0021-0214 violates the
phenomenological relations between the radio and X-ray luminosities of
coronally active stars, hinting that radio and X-ray activity are also
uncorrelated at the bottom of the main sequence. The radio active sources that
have measured rotational velocities are rapid rotators, Vsin(i)>30 km/sec,
while the upper limits on radio activity in slowly-rotating late M dwarfs
(Vsin(i)<10 km/sec) are lower than these detections. These observations provide
tantalizing evidence that rapidly-rotating late M and L dwarfs are more likely
to be radio active. This possible correlation is puzzling given that the
observed radio emission requires sustained magnetic fields of 10-1000 G and
densities of 10^12 cm^-3, indicating that the active sources should have slowed
down considerably due to magnetic braking.Comment: Accepted to ApJ; Two new figures; Minor text revision
Young Suns Exoplanet Survey: Detection of a wide-orbit planetary-mass companion to a solar-type Sco-Cen member
The Young Suns Exoplanet Survey consists of a homogeneous sample of 70 young, solar-mass stars located in the Lower Centaurus-Crux subgroup of the Scorpius-Centaurus association with an average age of 15 ± 3 Myr. We report the detection of a co-moving companion around the K3IV star TYC 8998-760-1 (2MASSJ13251211–6456207) that is located at a distance of 94.6 ± 0.3 pc using SPHERE/IRDIS on the VLT. Spectroscopic observations with VLT/X-SHOOTER constrain the mass of the star to 1.00±0.02M⊙ and an age of 16.7±1.4 Myr. The companion TYC 8998-760-1 b is detected at a projected separation of 1.71″, which implies a projected physical separation of 162 au. Photometric measurements ranging from Y to M band provide a mass estimate of 14±3 M_(jup) by comparison to BT-Settl and AMES-dusty isochrones, corresponding to a mass ratio of q = 0.013 ± 0.003 with respect to the primary. We rule out additional companions to TYC 8998-760-1 that are more massive than 12 M_(jup) and farther than 12 au away from the host. Future polarimetric and spectroscopic observations of this system with ground and space based observatories will facilitate testing of formation and evolution scenarios shaping the architecture of the circumstellar environment around this ‘young Sun’
Saturation in heteronuclear photoassociation of 6Li7Li
We report heteronuclear photoassociation spectroscopy in a mixture of
magneto-optically trapped 6Li and 7Li. Hyperfine resolved spectra of the
vibrational level v=83 of the singlet state have been taken up to intensities
of 1000 W/cm^2. Saturation of the photoassociation rate has been observed for
two hyperfine transitions, which can be shown to be due to saturation of the
rate coefficient near the unitarity limit. Saturation intensities on the order
of 40 W/cm^2 can be determined.Comment: 5 pages, 3 figures, to appear in Phys. Rev. A (Rapid Communication
Cell-specific responses to the cytokine TGFβ are determined by variability in protein levels
The cytokine TGFβ provides important information during embryonic development, adult tissue homeostasis, and regeneration. Alterations in the cellular response to TGFβ are involved in severe human diseases. To understand how cells encode the extracellular input and transmit its information to elicit appropriate responses, we acquired quantitative time-resolved measurements of pathway activation at the single-cell level. We established dynamic time warping to quantitatively compare signaling dynamics of thousands of individual cells and described heterogeneous single-cell responses by mathematical modeling. Our combined experimental and theoretical study revealed that the response to a given dose of TGFβ is determined cell specifically by the levels of defined signaling proteins. This heterogeneity in signaling protein expression leads to decomposition of cells into classes with qualitatively distinct signaling dynamics and phenotypic outcome. Negative feedback regulators promote heterogeneous signaling, as a SMAD7 knock-out specifically affected the signal duration in a subpopulation of cells. Taken together, we propose a quantitative framework that allows predicting and testing sources of cellular signaling heterogeneity
A Comparison of Outflow Properties in AGN Dwarfs vs. Star Forming Dwarfs
Feedback likely plays a crucial role in resolving discrepancies between
observed and theoretical predictions of dwarf galaxy properties. Stellar
feedback was once believed to be sufficient to explain these discrepancies, but
it has thus far failed to fully reconcile theory and observations. The recent
discovery of energetic galaxy-wide outflows in dwarf galaxies hosting Active
Galactic Nuclei (AGN) suggests that AGN feedback may have a larger role in the
evolution of dwarf galaxies than previously suspected. In order to assess the
relative importance of stellar versus AGN feedback in these galaxies, we
perform a detailed Keck/KCWI optical integral field spectroscopic study of a
sample of low-redshift star-forming (SF) dwarf galaxies that show outflows in
ionized gas in their SDSS spectra. We characterize the outflows and compare
them to observations of AGN-driven outflows in dwarfs. We find that SF dwarfs
have outflow components that have comparable widths (W) to those of
outflows in AGN dwarfs, but are much less blue-shifted, indicating that SF
dwarfs have significantly slower outflows than their AGN counterparts. The
outflows in SF dwarfs are spatially resolved and significantly more extended
than those in AGN dwarfs. The mass loss rates, momentum and energy rates of
SF-driven outflows are much lower than those of AGN-driven outflows. Our
results indicate that AGN feedback in the form of gas outflows may play an
important role in dwarf galaxies and should be considered along with SF
feedback in models of dwarf galaxy evolution.Comment: 27 pages, 25 figures, Accepted for publication in Ap
Olaparib in combination with pegylated liposomal doxorubicin for platinum-resistant ovarian cancer regardless of BRCA status: a GEICO phase II trial (ROLANDO study)
Inhibidor de PARP; Olaparib; Càncer d'ovari recurrent resistent al platíInhibidor de PARP; Olaparib; Cáncer de ovario recurrente resistente al platinoPARP inhibitor; Olaparib; Platinum-resistant recurrent ovarian cancerBackground
There is limited evidence for the benefit of olaparib in platinum-resistant ovarian cancer (PROC) patients with BRCA wild-type tumors. This study investigated whether this combination of a DNA-damaging chemotherapy plus olaparib is effective in PROC regardless BRCA status.
Patients and methods
Patients with high-grade serous or endometrioid ovarian carcinoma and one previous PROC recurrence were enrolled regardless of BRCA status. Patients with ≤4 previous lines (up to 5 in BRCA-mut) with at least one previous platinum-sensitive relapse were included; primary PROC was allowed only in case of BRCA-mut. Patients initially received six cycles of olaparib 300 mg b.i.d. (biduum) + intravenous pegylated liposomal doxorubicin (PLD) 40 mg/m2 (PLD40) every 28 days, followed by maintenance with olaparib 300 mg b.i.d. until progression or toxicity. The PLD dose was reduced to 30 mg/m2 (PLD30) due to toxicity. The primary endpoint was progression-free survival (PFS) at 6 months (6m-PFS) by RECIST version 1.1. A proportion of 40% 6m-PFS or more was considered of clinical interest.
Results
From 2017 to 2020, 31 PROC patients were included. BRCA mutations were present in 16%. The median of previous lines was 2 (range 1-5). The overall disease control rate was 77% (partial response rate of 29% and stable disease rate of 48%). After a median follow-up of 10 months, the 6m-PFS and median PFS were 47% and 5.8 months, respectively. Grade ≥3 treatment-related adverse events occurred in 74% of patients, with neutropenia/anemia being the most frequent. With PLD30 serious AEs were less frequent than with PLD40 (21% versus 47%, respectively); moreover, PLD30 was associated with less PLD delays (32% versus 38%) and reductions (16% versus 22%).
Conclusions
The PLD–olaparib combination has shown significant activity in PROC regardless of BRCA status. PLD at 30 mg/m2 is better tolerated in the combination.This work was supported by Grupo Español de Investigación en Cáncer de Ovario (GEICO) (no grant number). AstraZeneca provided olaparib and awarded a grant to GEICO (no grant number) to pay the costs of the study but did not take part in the conduct of the current clinical trial or in the analysis and interpretation of the results. Pegylated ribosomal doxorubicin was provided by the sites according to local standard procedures
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