1,182 research outputs found
Magnetic field induced by elliiptical instability in a rotating tidally distorded sphere
It is usually believed that the geo-dynamo of the Earth or more generally of
other planets, is created by the convective fluid motions inside their molten
cores. An alternative to this thermal or compositional convection can however
be found in the inertial waves resonances generated by the eventual precession
of these planets or by the possible tidal distorsions of their liquid cores. We
will review in this paper some of our experimental works devoted to the
elliptical instability and present some new results when the experimental fluid
is a liquid metal. We show in particular that an imposed magnetic field is
distorted by the spin- over mode generated by the elliptical instability. In
our experiment, the field is weak (20 Gauss) and the Lorenz force is negligible
compared to the inertial forces, therefore the magnetic field does not modify
the fluid flow and the pure hydrodynamics growth rates of the instability are
recovered through magnetic measurements
Chlorine-bearing molecules in molecular absorbers at intermediate redshifts
We use observations of chlorine-bearing species in molecular absorbers at intermediate redshifts to investigate chemical properties and Cl-35/Cl-37 isotopic ratios in the absorbing sightlines. Chloronium (H2Cl+) is detected along three independent lines of sight in the z = 0.89 and z = 0.68 molecular absorbers located in front of the lensed quasars PKS 1830-211 and B 0218+357, respectively. Hydrogen chloride (HCl) was observed only toward PKS 1830-211, and is found to behave differently from H2Cl+. It is detected in one line of sight with an abundance ratio [H2Cl+]/[HCl] similar to 1, but remains undetected in the other, more diffuse, line of sight, with a ratio [H2Cl+] / [HCl] > 17. The absorption profiles of these two chlorine-bearing species are compared to other species and discussed in terms of the physical properties of the absorbing gas. Our findings are consistent with the picture emerging from chemical models where different species trace gas with different molecular hydrogen fraction. The Cl-35/Cl-37 isotopic ratios are measured in the different lines of sight and are discussed in terms of stellar nucleosynthesis
Glutathione is key to the synergistic enhancement of doxorubicin and etoposide by polyphenols in leukaemia cell lines
Recently published in Nature: Cell Death and Discovery,
Mahbub et al.1 have demonstrated that polyphenols can
synergistically enhance the action of the topoisomerase II
inhibitors: doxorubicin and etoposide in leukaemia cells. A
reduction of glutathione (GSH) was strongly associated with
sensitising cells to the pro-apoptotic effects of polyphenols when used in combination with doxorubicin or etoposide. Importantly, when polyphenols and topoisomerase II inhibitors were combined, it was possible to induce a
synergistic decrease in cell proliferation (measured as ATP
levels), cell-cycle arrest and induction of apoptosis in
leukaemia cell lines
An Upper Mass Limit on a Red Supergiant Progenitor for the Type II-Plateau Supernova SN 2006my
We analyze two pre-supernova (SN) and three post-SN high-resolution images of
the site of the Type II-Plateau supernova SN 2006my in an effort to either
detect the progenitor star or to constrain its properties. Following image
registration, we find that an isolated stellar object is not detected at the
location of SN 2006my in either of the two pre-SN images. In the first, an
I-band image obtained with the Wide-Field and Planetary Camera 2 on board the
Hubble Space Telescope, the offset between the SN 2006my location and a
detected source ("Source 1") is too large: > 0.08", which corresponds to a
confidence level of non-association of 96% from our most liberal estimates of
the transformation and measurement uncertainties. In the second, a similarly
obtained V-band image, a source is detected ("Source 2") that has overlap with
the SN 2006my location but is definitively an extended object. Through
artificial star tests carried out on the precise location of SN 2006my in the
images, we derive a 3-sigma upper bound on the luminosity of a red supergiant
that could have remained undetected in our pre-SN images of log L/L_Sun = 5.10,
which translates to an upper bound on such a star's initial mass of 15 M_Sun
from the STARS stellar evolutionary models. Although considered unlikely, we
can not rule out the possibility that part of the light comprising Source 1,
which exhibits a slight extension relative to other point sources in the image,
or part of the light contributing to the extended Source 2, may be due to the
progenitor of SN 2006my. Only additional, high-resolution observations of the
site taken after SN 2006my has faded beyond detection can confirm or reject
these possibilities.Comment: Minor text changes from Version 1. Appendix added detailing the
determination of confidence level of non-association of point sources in two
registered astronomical image
Type IIn supernovae at z ~ 2 from archival data
Supernovae have been confirmed to redshift z ~ 1.7 for type Ia (thermonuclear
detonation of a white dwarf) and to z ~ 0.7 for type II (collapse of the core
of the star). The subclass type IIn supernovae are luminous core-collapse
explosions of massive stars and, unlike other types, are very bright in the
ultraviolet, which should enable them to be found optically at redshifts z ~ 2
and higher. In addition, the interaction of the ejecta with circumstellar
material creates strong, long-lived emission lines that allow spectroscopic
confirmation of many events of this type at z ~ 2 for 3 - 5 years after
explosion. Here we report three spectroscopically confirmed type IIn
supernovae, at redshifts z = 0.808, 2.013 and 2.357, detected in archival data
using a method designed to exploit these properties at z ~ 2. Type IIn
supernovae directly probe the formation of massive stars at high redshift. The
number found to date is consistent with the expectations of a locally measured
stellar initial mass function, but not with an evolving initial mass function
proposed to explain independent observations at low and high redshift.Comment: 8 pages, 2 figures, includes supplementary informatio
ISTH definition of pulmonary embolism-related death and classification of the cause of death in venous thromboembolism studies: validation in an autopsy cohort.
BACKGROUND
The International Society on Thrombosis and Haemostasis (ISTH)'s Scientific and Standardization Committee (SSC) recently proposed a definition of pulmonary embolism (PE)-related death. We aimed to evaluate the accuracy and interrater reliability of the definition in an autopsy cohort.
METHODS
We reviewed reports of 1,064 consecutive adult autopsies that were performed at the NewYork-Presbyterian Hospital from 01/2010 until 07/2019. We included all patients with autopsy-confirmed PE-related death (cases) during that time frame, combined with patients who died in 2018 from a cause other than PE (controls). Based on clinical summaries, two adjudicators independently adjudicated the cause of death in each patient using the ISTH classification for the cause of death, blinded to the case/control status and ratio. The primary outcome was autopsy-confirmed PE-related death. We determined the sensitivity and specificity of the ISTH definition to identify autopsy-confirmed PE-related death, and its interrater reliability using the percentage agreement and Cohen's kappa.
RESULTS
A total of 126 patients who underwent autopsy were included in the analysis (median age, 68 years [range, 21-94], 60 [48%] women), of which 29 (23%) had died from PE as confirmed by autopsy. The ISTH definition's sensitivity and specificity for autopsy-confirmed PE-related death were 45% (95% CI, 26-64) and 99% (95% CI, 94-100), respectively. Interrater reliability for PE-related death was substantial (percentage agreement, 94% [95% CI, 89-97]; kappa, 0.73 [95% CI, 0.55-0.97]).
CONCLUSION
Adjudication of the cause of death using the ISTH definition resulted in very high specificity, moderate sensitivity, and good interrater reliability for PE-related death
High-angular-resolution NIR view of the Orion Bar revealed by Keck/NIRC2
Context. Nearby photo-dissociation regions (PDRs), where the gas and dust are heated by the far-ultraviolet (FUV) irradiation emitted from stars, are ideal templates with which to study the main stellar feedback processes. Aims. With this study, we aim to probe the detailed structures at the interfaces between ionized, atomic, and molecular gas in the Orion Bar. This nearby prototypical strongly irradiated PDR are among the first targets of the James Webb Space Telescope (JWST) within the framework of the PDRs4All Early Release Science program. Methods. We employed the subarcsecond resolution accessible with Keck-II NIRC2 and its adaptive optics system to obtain images of the vibrationally excited line H2 1-0 S(1) at 2.12 μm that are more detailed and complete than ever before. H2 1-0 S(1) traces the dissociation front (DF), and the [FeII] and Brγ lines, at 1.64 and 2.16 μm, respectively, trace the ionization front (IF). The former is a powerful tracer of the FUV radiation field strength and gas density distribution at the PDR edge, while the last two trace the temperature and density distribution from the ionized gas to the PDR. We obtained narrow-band filter images in these key gas line diagnostics over ∼40″ at spatial scales of ∼0.1″ (∼0.0002 pc or ∼40 AU at 414 pc). Results. The Keck/Near Infrared Camera 2 (NIRC2) observations spatially resolve a plethora of irradiated substructures such as ridges, filaments, globules, and proplyds. This portends what JWST should accomplish and how it will complement the highest resolution Atacama Large Millimeter/submillimeter Array (ALMA) maps of the molecular cloud. We observe a remarkable spatial coincidence between the H2 1-0 S(1) vibrational and HCO+ J = 4-3 rotational emission previously obtained with ALMA. This likely indicates the intimate link between these two molecular species and highlights that in high-pressure PDRs, the H/H2 and C+/C/CO transitions zones come closer than in a typical layered structure of a constant density PDR. The H/H2 dissociation front appears as a highly structured region containing substructures with a typical thickness of a few ∼10-3 pc
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