278 research outputs found
The origin of planetary impactors in the inner solar system
New insights into the history of the inner solar system are derived from the
impact cratering record of the Moon, Mars, Venus and Mercury, and from the size
distributions of asteroid populations. Old craters from a unique period of
heavy bombardment that ended 3.8 billion years ago were made by asteroids
that were dynamically ejected from the main asteroid belt, possibly due to the
orbital migration of the giant planets. The impactors of the past 3.8
billion years have a size distribution quite different from the main belt
asteroids, but very similar to the population of near-Earth asteroids.Comment: 12 pages (including 4 figures
Response of a Fermi gas to time-dependent perturbations: Riemann-Hilbert approach at non-zero temperatures
We provide an exact finite temperature extension to the recently developed
Riemann-Hilbert approach for the calculation of response functions in
nonadiabatically perturbed (multi-channel) Fermi gases. We give a precise
definition of the finite temperature Riemann-Hilbert problem and show that it
is equivalent to a zero temperature problem. Using this equivalence, we discuss
the solution of the nonequilibrium Fermi-edge singularity problem at finite
temperatures.Comment: 10 pages, 2 figures; 2 appendices added, a few modifications in the
text, typos corrected; published in Phys. Rev.
Fermi edge singularity in a non-equilibrium system
We report exact results for the Fermi Edge Singularity in the absorption
spectrum of an out-of-equilibrium tunnel junction. We consider two metals with
chemical potential difference V separated by a tunneling barrier containing a
defect, which exists in one of two states. When it is in its excited state,
tunneling through the otherwise impermeable barrier is possible. We find that
the lineshape not only depends on the total scattering phase shift as in the
equilibrium case but also on the difference in the phase of the reflection
amplitudes on the two sides of the barrier. The out-of-equilibrium spectrum
extends below the original threshold as energy can be provided by the power
source driving current across the barrier. Our results have a surprisingly
simple interpretation in terms of known results for the equilibrium case but
with (in general complex-valued) combinations of elements of the scattering
matrix replacing the equilibrium phase shifts.Comment: 4 page
Energy-dependent effective interactions for dilute many-body systems
We address the issue of determining an effective two-body interaction for
mean-field calculations of energies of many-body systems. We show that the
effective interaction is proportional to the phase shift, and demonstrate this
result in the quasiclassical approximation when there is a trapping potential
in addition to the short-range interaction between a pair of particles. We
calculate numerically energy levels for the case of an interaction with a
short-range square-well and a harmonic trapping potential and show that the
numerical results agree well with the analytical expression. We derive a
generalized Gross--Pitaevskii equation which includes effective range
corrections and discuss the form of the electron--atom effective interaction to
be used in calculations of Rydberg atoms and molecules.Comment: 6 pages, 2 figure
Fermi-edge problem in the presence of AC electric field
We study in this paper a non-equilibrium Fermi-edge problem where the system
under investigation is a single electron reservoir putting under an AC electric
field. We show that the electron Green's function and other correlation
functions in the problem can be solved and expressed exactly in terms of a
well-defined integral. The qualitative behaviors of the solution is studied and
compared with the situation where the impurity is coupled to more than one
reservoirs at different chemical potentials.Comment: Published versio
Emerging roles of ATG7 in human health and disease
The cardinal stages of macroautophagy are driven by core autophagy-related (ATG) proteins, whose ablation largely abolishes intracellular turnover. Disrupting ATG genes is paradigmatic of studying autophagy deficiency, yet emerging data suggest that ATG proteins have extensive biological importance beyond autophagic elimination. An important example is ATG7, an essential autophagy effector enzyme that in concert with other ATG proteins, also regulates immunity, cell death and protein secretion, and independently regulates the cell cycle and apoptosis. Recently, a direct association between ATG7 dysfunction and disease was established in patients with biallelic ATG7 variants and childhood-onset neuropathology. Moreover, a prodigious body of evidence supports a role for ATG7 in protecting against complex disease states in model organisms, although how dysfunctional ATG7 contributes to manifestation of these diseases, including cancer, neurodegeneration and infection, in humans remains unclear. Here, we systematically review the biological functions of ATG7, discussing the impact of its impairment on signalling pathways and human pathology. Future studies illuminating the molecular relationship between ATG7 dysfunction and disease will expedite therapies for disorders involving ATG7 deficiency and/or impaired autophagy.Peer reviewe
FANTOM5 CAGE profiles of human and mouse samples
In the FANTOM5 project, transcription initiation events across the human and
mouse genomes were mapped at a single base-pair resolution and their
frequencies were monitored by CAGE (Cap Analysis of Gene Expression) coupled
with single-molecule sequencing. Approximately three thousands of samples,
consisting of a variety of primary cells, tissues, cell lines, and time series
samples during cell activation and development, were subjected to a uniform
pipeline of CAGE data production. The analysis pipeline started by measuring
RNA extracts to assess their quality, and continued to CAGE library production
by using a robotic or a manual workflow, single molecule sequencing, and
computational processing to generate frequencies of transcription initiation.
Resulting data represents the consequence of transcriptional regulation in
each analyzed state of mammalian cells. Non-overlapping peaks over the CAGE
profiles, approximately 200,000 and 150,000 peaks for the human and mouse
genomes, were identified and annotated to provide precise location of known
promoters as well as novel ones, and to quantify their activities
DGAT1 activity synchronises with mitophagy to protect cells from metabolic rewiring by iron depletion
Mitophagy removes defective mitochondria via lysosomal elimination. Increased mitophagy coincides with metabolic reprogramming, yet it remains unknown whether mitophagy is a cause or consequence of such state changes. The signalling pathways that integrate with mitophagy to sustain cell and tissue integrity also remain poorly defined. We performed temporal metabolomics on mammalian cells treated with deferiprone, a therapeutic iron chelator that stimulates PINK1/PARKIN-independent mitophagy. Iron depletion profoundly rewired the metabolome, hallmarked by remodelling of lipid metabolism within minutes of treatment. DGAT1-dependent lipid droplet biosynthesis occurred several hours before mitochondrial clearance, with lipid droplets bordering mitochondria upon iron chelation. We demonstrate that DGAT1 inhibition restricts mitophagy in vitro, with impaired lysosomal homeostasis and cell viability. Importantly, genetic depletion of DGAT1 in vivo significantly impaired neuronal mitophagy and locomotor function in Drosophila. Our data define iron depletion as a potent signal that rapidly reshapes metabolism and establishes an unexpected synergy between lipid homeostasis and mitophagy that safeguards cell and tissue integrity.Peer reviewe
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