4,807 research outputs found
Gravitational wave source populations: Disentangling an AGN component
The astrophysical origin of the over 90 compact binary mergers discovered by
the LIGO and Virgo gravitational wave observatories is an open question. While
the unusual mass and spin of some of the discovered objects constrain
progenitor scenarios, the observed mergers are consistent with multiple
interpretations. A promising approach to solve this question is to consider the
observed distributions of binary properties and compare them to expectations
from different origin scenarios. Here we describe a new hierarchical population
analysis framework to assess the relative contribution of different formation
channels simultaneously. For this study we considered binary formation in AGN
disks along with phenomenological models, but the same framework can be
extended to other models. We find that high-mass and high-mass-ratio binaries
appear more likely to have an AGN origin compared to the same origin as
lower-mass events. Future observations of high-mass black hole mergers could
further disentangle the AGN component from other channels.Comment: 7 pages, 4 figures, and 1 tabl
Increase of the mean inner Coulomb potential in Au clusters induced by surface tension and its implication for electron scattering
Electron holography in a transmission electron microscope was applied to
measure the phase shift induced by Au clusters as a function of the cluster
size. Large phase shifts Df observed for small Au clusters cannot be described
by the well-known equation Df=C_E V_0 t (C_E: interaction constant, V_0: mean
inner Coulomb potential (MIP) of bulk gold, t: cluster thickness). The rapid
increase of the Au MIP with decreasing cluster size derived from Df, can be
explained by the compressive strain of surface atoms in the cluster
Reversible Electrocatalytic Production and Oxidation of Hydrogen at Low Overpotentials by a Functional Hydrogenase Mimic
An efficient ligand combination: A new bis(diphosphine) nickel(II) complex (see picture) is described. A ΔG° value of 0.84 kcal mol^(−1) for hydrogen addition for this complex was calculated from the experimentally determined equilibrium constant. This complex displayed reversible electrocatalytic activity for hydrogen production and oxidation at low overpotentials, which are characteristic for hydrogenase enzymes
The CoQ oxidoreductase FSP1 acts parallel to GPX4 to inhibit ferroptosis.
Ferroptosis is a form of regulated cell death that is caused by the iron-dependent peroxidation of lipids1,2. The glutathione-dependent lipid hydroperoxidase glutathione peroxidase 4 (GPX4) prevents ferroptosis by converting lipid hydroperoxides into non-toxic lipid alcohols3,4. Ferroptosis has previously been implicated in the cell death that underlies several degenerative conditions2, and induction of ferroptosis by the inhibition of GPX4 has emerged as a therapeutic strategy to trigger cancer cell death5. However, sensitivity to GPX4 inhibitors varies greatly across cancer cell lines6, which suggests that additional factors govern resistance to ferroptosis. Here, using a synthetic lethal CRISPR-Cas9 screen, we identify ferroptosis suppressor protein 1 (FSP1) (previously known as apoptosis-inducing factor mitochondrial 2 (AIFM2)) as a potent ferroptosis-resistance factor. Our data indicate that myristoylation recruits FSP1 to the plasma membrane where it functions as an oxidoreductase that reduces coenzyme Q10 (CoQ) (also known as ubiquinone-10), which acts as a lipophilic radical-trapping antioxidant that halts the propagation of lipid peroxides. We further find that FSP1 expression positively correlates with ferroptosis resistance across hundreds of cancer cell lines, and that FSP1 mediates resistance to ferroptosis in lung cancer cells in culture and in mouse tumour xenografts. Thus, our data identify FSP1 as a key component of a non-mitochondrial CoQ antioxidant system that acts in parallel to the canonical glutathione-based GPX4 pathway. These findings define a ferroptosis suppression pathway and indicate that pharmacological inhibition of FSP1 may provide an effective strategy to sensitize cancer cells to ferroptosis-inducing chemotherapeutic agents
Information Causality and Extremal Tripartite Correlations
We study the principle of information causality for the set of extremal
correlations in the tripartite scenario. We show that all but one nonlocal
extremal correlations in this scenario violate information causality. This
undetected correlation is shown to satisfy any bipartite physical principle.Comment: 8 pages, 2 figures. Minor corrections and improvement to the proof in
appendi
Ground State Magnetization of Polymerized Spin Chains
We investigate the ground state magnetization plateaus appearing in spin 1/2
polymerized Heisenberg chains under external magnetic fields. The associated
fractional quantization scenario and the exponents which characterize the
opening of gapful excitations are analyzed by means of abelian bosonization
methods. Our conclusions are fully supported by the extrapolated results
obtained from Lanczos diagonalizations of finite systems.Comment: 5 pages, 6 figures, final version to appear in Phys.Rev.
ALMA Observations of the Sub-kpc Structure of the Host Galaxy of a z= 6.5 Lensed Quasar: A Rotationally-Supported Hyper-Starburst System at the Epoch of Reionization
We report ALMA observations of the dust continuum and {\cii} emission of the
host galaxy of J0439+1634, a gravitationally lensed quasar at .
Gravitational lensing boosts the source-plane resolution to \sim0\farcs15
. The lensing model derived from the ALMA data is
consistent with the fiducial model in \citet{fan19} based on {\it HST} imaging.
The host galaxy of J0439+1634 can be well-fitted by a S\'ersic profile
consistent with an exponential disk, both in the far-infrared (FIR) continuum
and the {\cii} emission. The overall magnification is for the
continuum and for the {\cii} line. The host galaxy of J0439+1634
is a compact ultra-luminous infrared galaxy, with a total star formation rate
(SFR) of after correcting for lensing and
an effective radius of kpc. The resolved regions in J0439+1634 follow
the ``{\cii} deficit," where the {\cii}-to-FIR ratio decreases with FIR surface
brightness. The reconstructed velocity field of J0439+1634 appears to be
rotation-like. The maximum line-of-sight rotation velocity of 130 km/s at a
radius of 2 kpc. However, our data cannot be fit by an axisymmetric thin
rotating disk, and the inclination of the rotation axis, , remains
unconstrained. We estimate the dynamical mass of the host galaxy to be
. J0439+1634 is likely to have a high
gas-mass fraction and an oversized SMBH compared to local relations. The SFR of
J0439+1634 reaches the maximum possible values, and the SFR surface density is
close to the highest value seen in any star-forming galaxy currently known in
the universe.Comment: 14 pages, 7 figures. Accepted by Ap
Mitochondrial CoQ deficiency is a common driver of mitochondrial oxidants and insulin resistance
Insulin resistance in muscle, adipocytes and liver is a gateway to a number of metabolic diseases. Here, we show a selective deficiency in mitochondrial coenzyme Q (CoQ) in insulin-resistant adipose and muscle tissue. This defect was observed in a range of in vitro insulin resistance models and adipose tissue from insulin-resistant humans and was concomitant with lower expression of mevalonate/CoQ biosynthesis pathway proteins in most models. Pharmacologic or genetic manipulations that decreased mitochondrial CoQ triggered mitochondrial oxidants and insulin resistance while CoQ supplementation in either insulin-resistant cell models or mice restored normal insulin sensitivity. Specifically, lowering of mitochondrial CoQ caused insulin resistance in adipocytes as a result of increased superoxide/hydrogen peroxide production via complex II. These data suggest that mitochondrial CoQ is a proximal driver of mitochondrial oxidants and insulin resistance, and that mechanisms that restore mitochondrial CoQ may be effective therapeutic targets for treating insulin resistance
Molecular excitation in the Interstellar Medium: recent advances in collisional, radiative and chemical processes
We review the different excitation processes in the interstellar mediumComment: Accepted in Chem. Re
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