4,393 research outputs found
HIV-1 replication and the cellular eukaryotic translation apparatus
Eukaryotic translation is a complex process composed of three main steps: initiation, elongation, and termination. During infections by RNA- and DNA-viruses, the eukaryotic translation machinery is used to assure optimal viral protein synthesis. Human immunodeficiency virus type I (HIV-1) uses several non-canonical pathways to translate its own proteins, such as leaky scanning, frameshifting, shunt, and cap-independent mechanisms. Moreover, HIV-1 modulates the host translation machinery by targeting key translation factors and overcomes different cellular obstacles that affect protein translation. In this review, we describe how HIV-1 proteins target several components of the eukaryotic translation machinery, which consequently improves viral translation and replication
de Sitter Thick Brane Solution in Weyl Geometry
In this paper, we consider a de Sitter thick brane model in a pure geometric
Weyl integrable five-dimensional space-time, which is a generalization of
Riemann geometry and is invariant under a so-called Weyl rescaling. We find a
solution of this model via performing a conformal transformation to map the
Weylian structure into a familiar Riemannian one with a conformal metric. The
metric perturbations of the model are discussed. For gravitational
perturbation, we get the effective modified Pschl-Teller
potential in corresponding Schrdinger equation for
Kaluza-Klein (KK) modes of the graviton. There is only one bound state, which
is a normalizable massless zero mode and represents a stable 4-dimensional
graviton. Furthermore, there exists a mass gap between the massless mode and
continuous KK modes. We also find that the model is stable under the scalar
perturbation in the metric. The correction to the Newtonian potential on the
brane is proportional to , where is the de Sitter
parameter of the brane. This is very different from the correction caused by a
volcano-like effective potential.Comment: 24 pages, 13 figures, published versio
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Modeling, Oscillation Analysis and Distributed Stabilization Control of Autonomous PV-based Microgrids
Driven by rising energy demand and the goal of carbon neutrality, renewable energy generations (REGs), especially photovoltaic (PV) generations, are widely used in the urban power energy systems. While the intelligent control of microgrids (MG) brings economic and efficient operation, its potential stability problem cannot be ignored. To date, most of the research on modeling, analyzing and enhancing the stability of MG usually assume the DC-link as an ideal voltage source. However, this practice of ignoring the dynamics of DC-link may omit the latent oscillation phenomena of autonomous PV-based MG. First, this paper establishes a complete dynamic model of autonomous PV-based MG including PV panels and DC-link. Different from previous conclusions of idealizing DC-link dynamics, participation factor analysis finds the potential impact of DC-link dynamics on system dynamic performance, and different influence factors including critical control parameters and non-linear V-I output characteristic of PV array are considered to further reveal oscillation mechanisms. Second, based on the average consensus algorithm, a distributed stabilization controller with strong robustness is proposed to enhance stability of the PV-based MG, which does not affect the steady-state performance of the system. Finally, the correctness of all theoretical analysis and the effectiveness of the proposed controller are verified by time domain simulation and hardware-in-loop tests.10.13039/501100001809-National Natural Science Foundation of China (Grant Number: 51907031
Effects of temperature on thick branes and the fermion (quasi-)localization
Following Campos's work [Phys. Rev. Lett. 88, 141602 (2002)], we investigate
the effects of temperature on flat, de Sitter (dS), and anti-de Following
Campos's work [Phys. Rev. Lett. \textbf{88}, 141602 (2002)], we investigate the
effects of temperature on flat, de Sitter (dS), and anti-de Sitter (AdS) thick
branes in five-dimensional (5D) warped spacetime, and on the fermion
(quasi-)localization. First, in the case of flat brane, when the critical
temperature reaches, the solution of the background scalar field and the warp
factor is not unique. So the thickness of the flat thick brane is uncertain at
the critical value of the temperature parameter, which is found to be lower
than the one in flat 5D spacetime. The mass spectra of the fermion Kaluza-Klein
(KK) modes are continuous, and there is a series of fermion resonances. The
number and lifetime of the resonances are finite and increase with the
temperature parameter, but the mass of the resonances decreases with the
temperature parameter. Second, in the case of dS brane, we do not find such a
critical value of the temperature parameter. The mass spectra of the fermion KK
modes are also continuous, and there is a series of fermion resonances. The
effects of temperature on resonance number, lifetime, and mass are the same
with the case of flat brane. Last, in the case of AdS brane, {the critical
value of the temperature parameter can less or greater than the one in the flat
5D spacetime.} The spectra of fermion KK modes are discrete, and the mass of
fermion KK modes does not decrease monotonically with increasing temperature
parameter.Comment: 24 pages, 15 figures, published versio
Domain wall brane in squared curvature gravity
We suggest a thick braneworld model in the squared curvature gravity theory.
Despite the appearance of higher order derivatives, the localization of gravity
and various bulk matter fields is shown to be possible. The existence of the
normalizable gravitational zero mode indicates that our four-dimensional
gravity is reproduced. In order to localize the chiral fermions on the brane,
two types of coupling between the fermions and the brane forming scalar is
introduced. The first coupling leads us to a Schr\"odinger equation with a
volcano potential, and the other a P\"oschl-Teller potential. In both cases,
the zero mode exists only for the left-hand fermions. Several massive KK states
of the fermions can be trapped on the brane, either as resonant states or as
bound states.Comment: 18 pages, 5 figures and 1 table, references added, improved version
to be published in JHE
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Cycling Stem Cells Are Radioresistant and Regenerate the Intestine.
A certain number of epithelial cells in intestinal crypts are DNA damage resistant and contribute to regeneration. However, the cellular mechanism underlying intestinal regeneration remains unclear. Using lineage tracing, we show that cells marked by an Msi1 reporter (Msi1+) are right above Lgr5high cells in intestinal crypts and exhibit DNA damage resistance. Single-cell RNA sequencing reveals that the Msi1+ cells are heterogeneous with the majority being intestinal stem cells (ISCs). The DNA damage-resistant subpopulation of Msi1+ cells is characterized by low-to-negative Lgr5 expression and is more rapidly cycling than Lgr5high radiosensitive crypt base columnar stem cells (CBCs). This enables an efficient repopulation of the intestinal epithelium at early stage when Lgr5high cells are not emerging. Furthermore, relative to CBCs, Msi1+ cells preferentially produce Paneth cells during homeostasis and upon radiation repair. Together, we demonstrate that the DNA damage-resistant Msi1+ cells are cycling ISCs that maintain and regenerate the intestinal epithelium
Vacuum Polarization and Dynamical Chiral Symmetry Breaking: Phase Diagram of QED with Four-Fermion Contact Interaction
We study chiral symmetry breaking for fundamental charged fermions coupled
electromagnetically to photons with the inclusion of four-fermion contact
self-interaction term. We employ multiplicatively renormalizable models for the
photon dressing function and the electron-photon vertex which minimally ensures
mass anomalous dimension = 1. Vacuum polarization screens the interaction
strength. Consequently, the pattern of dynamical mass generation for fermions
is characterized by a critical number of massless fermion flavors above which
chiral symmetry is restored. This effect is in diametrical opposition to the
existence of criticality for the minimum interaction strength necessary to
break chiral symmetry dynamically. The presence of virtual fermions dictates
the nature of phase transition. Miransky scaling laws for the electromagnetic
interaction strength and the four-fermion coupling, observed for quenched QED,
are replaced by a mean-field power law behavior corresponding to a second order
phase transition. These results are derived analytically by employing the
bifurcation analysis, and are later confirmed numerically by solving the
original non-linearized gap equation. A three dimensional critical surface is
drawn to clearly depict the interplay of the relative strengths of interactions
and number of flavors to separate the two phases. We also compute the
beta-function and observe that it has ultraviolet fixed point. The power law
part of the momentum dependence, describing the mass function, reproduces the
quenched limit trivially. We also comment on the continuum limit and the
triviality of QED.Comment: 9 pages, 10 figure
The TESS Objects of Interest Catalog from the TESS Prime Mission
We present 2241 exoplanet candidates identified with data from the Transiting Exoplanet Survey Satellite (TESS) during its 2 yr Prime Mission. We list these candidates in the TESS Objects of Interest (TOI) Catalog, which includes both new planet candidates found by TESS and previously known planets recovered by TESS observations. We describe the process used to identify TOIs, investigate the characteristics of the new planet candidates, and discuss some notable TESS planet discoveries. The TOI catalog includes an unprecedented number of small planet candidates around nearby bright stars, which are well suited for detailed follow-up observations. The TESS data products for the Prime Mission (sectors 1-26), including the TOI catalog, light curves, full-frame images, and target pixel files, are publicly available at the Mikulski Archive for Space Telescopes
Discovery of a Fast Expanding Shell in the Inside-out Born-Again Planetary Nebula HuBi 1 Through High-Dispersion Integral Field Spectroscopy
HuBi 1 has been proposed to be member of the rare class of born-again
planetary nebulae (PNe), i.e., its central star experienced a very late thermal
pulse and ejected highly-processed material at high speeds inside the old
hydrogen-rich PN. In this letter we present GTC MEGARA integral field
spectroscopic observations of the innermost regions of HuBi 1 at high spectral
resolution km s and multi-epoch sub-arcsec images obtained
yr apart. The analysis of these data indicates that the inner
regions of HuBi 1 were ejected yr ago and expand at velocities
km s, in excellent agreement with the born-again scenario.
The unprecedented tomographic capabilities of the GTC MEGARA high-dispersion
observations used here reveal that the ejecta in HuBi 1 has a shell-like
structure, in contrast to the disrupted disk and jet morphology of the ejecta
in other born-again PNe.Comment: 7 pages, 5 Figures; accepted to ApJ
Two-channel Kondo Lattice Model on a ladder studied by the Density Matrix Renormalization Group Method
Using the density matrix renormalization group (DMRG) method we study a
two-channel Kondo lattice model on a half filled ladder. Our model involves an
on-site s-wave and a nearest neighbor d-wave coupling between the local moments
and the conduction electrons on the ladder. By changing the relative strength
of the two Kondo interactions we examine the evolution of the system from a
conventional Kondo insulator with a singlet at each site to a new kind of
semimetallic state formed by overlapping of Zhang-Rice-like singlets. The DMRG
is used to study how the spin and charge correlation functions evolve between
these two regimes
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