484 research outputs found
Large deformation of spherical vesicle studied by perturbation theory and Surface evolver
With tangent angle perturbation approach the axial symmetry deformation of a
spherical vesicle in large under the pressure changes is studied by the
elasticity theory of Helfrich spontaneous curvature model.Three main results in
axial symmetry shape: biconcave shape, peanut shape, and one type of myelin are
obtained. These axial symmetry morphology deformations are in agreement with
those observed in lipsome experiments by dark-field light microscopy [Hotani,
J. Mol. Biol. 178, (1984) 113] and in the red blood cell with two thin
filaments (myelin) observed in living state (see, Bessis, Living Blood Cells
and Their Ultrastructure, Springer-Verlag, 1973). Furthermore, the biconcave
shape and peanut shape can be simulated with the help of a powerful software,
Surface Evolver [Brakke, Exp. Math. 1, 141 (1992) 141], in which the
spontaneous curvature can be easy taken into account.Comment: 16 pages, 6 EPS figures and 2 PS figure
The strain energy and Young's Moduli of single-wall Carbon nanotubules calculated from the electronic energy-band theory
The strain energies in straight and bent single-walled carbon nanotubes
(SWNTs) are calculated by taking account of the total energy of all the
occupied band electrons. The obtained results are in good agreement with
previous theoretical studies and experimental observations. The Young's modulus
and the effective wall thickness of SWNT are obtained from the bending strain
energies of SWNTs with various cross-sectional radii. The repulsion potential
between ions contributes the main part of the Young's modulus of SWNT.
The wall thickness of SWNT comes completely from the overlap of electronic
orbits, and is approximately of the extension of
orbit of carbon atom. Both the Young's modulus and the wall thickness
are independent of the radius and the helicity of SWNT, and insensitive to the
fitting parameters.
The results show that continuum elasticity theory can serve well to describe
the mechanical properties of SWNTs.Comment: 12 pages, 2 figure
Coexistence of the spin-density-wave and superconductivity in the (Ba,K)Fe2As2
The relation between the spin-density-wave (SDW) and superconducting order is
a central topic in current research on the FeAs-based high Tc superconductors.
Conflicting results exist in the LaFeAs(O,F)-class of materials, for which
whether the SDW and superconductivity are mutually exclusive or they can
coexist has not been settled. Here we show that for the (Ba,K)Fe2As2 system,
the SDW and superconductivity can coexist in an extended range of compositions.
The availability of single crystalline samples and high value of the energy
gaps would make the materials a model system to investigate the high Tc
ferropnictide superconductivity.Comment: 4 pages, 5 figure
A Generic Two-band Model for Unconventional Superconductivity and Spin-Density-Wave Order in Electron and Hole Doped Iron-Based Superconductors
Based on experimental data on the newly synthesized iron-based
superconductors and the relevant band structure calculations, we propose a
minimal two-band BCS-type Hamiltonian with the interband Hubbard interaction
included. We illustrate that this two-band model is able to capture the
essential features of unconventional superconductivity and spin density wave
(SDW) ordering in this family of materials. It is found that bound
electron-hole pairs can be condensed to reveal the SDW ordering for zero and
very small doping, while the superconducting ordering emerges at small finite
doping, whose pairing symmetry is qualitatively analyzed to be of nodal d-wave.
The derived analytical formulas not only give out a nearly symmetric phase
diagram for electron and hole doping, but also is likely able to account for
existing main experimental results. Moreover, we also derive two important
relations for a general two-band model and elaborate how to apply them to
determine the band width ratio and the effective interband coupling strength
from experimental data.Comment: 6 pages, 4 figures, refs. added, typos correcte
Observation of the electromagnetic doubly OZI-suppressed decay
Using a sample of billion events accumulated with the BESIII
detector at the BEPCII collider, we report the observation of the decay , which is the first evidence for a doubly
Okubo-Zweig-Iizuka suppressed electromagnetic decay. A clear structure
is observed in the mass spectrum around 1.02 GeV/, which can
be attributed to interference between and
decays. Due to this interference, two
possible solutions are found. The corresponding measured values of the
branching fraction of are and .Comment: 7 pages, 4 figures, published in Phys. Rev.
The number of matchings in random graphs
We study matchings on sparse random graphs by means of the cavity method. We
first show how the method reproduces several known results about maximum and
perfect matchings in regular and Erdos-Renyi random graphs. Our main new result
is the computation of the entropy, i.e. the leading order of the logarithm of
the number of solutions, of matchings with a given size. We derive both an
algorithm to compute this entropy for an arbitrary graph with a girth that
diverges in the large size limit, and an analytic result for the entropy in
regular and Erdos-Renyi random graph ensembles.Comment: 17 pages, 6 figures, to be published in Journal of Statistical
Mechanic
Inhibition of the Integrin/FAK Signaling Axis and c-Myc Synergistically Disrupts Ovarian Cancer Malignancy
Integrins, a family of heterodimeric receptors for extracellular matrix, are promising therapeutic targets for ovarian cancer, particularly high-grade serous-type (HGSOC), as they drive tumor cell attachment, migration, proliferation and survival by activating focal adhesion kinase (FAK)-dependent signaling. Owing to the potential off-target effects of FAK inhibitors, disruption of the integrin signaling axis remains to be a challenge. Here, we tackled this barrier by screening for inhibitors being functionally cooperative with small-molecule VS-6063, a phase II FAK inhibitor. From this screening, JQ1, a potent inhibitor of Myc oncogenic network, emerged as the most robust collaborator. Treatment with a combination of VS-6063 and JQ1 synergistically caused an arrest of tumor cells at the G2/M phase and a decrease in the XIAP-linked cell survival. Our subsequent mechanistic analyses indicate that this functional cooperation was strongly associated with the concomitant disruption of activation or expression of FAK and c-Myc as well as their downstream signaling through the PI3K/Akt pathway. In line with these observations, we detected a strong co-amplification or upregulation at genomic or protein level for FAK and c-Myc in a large portion of primary tumors in the TCGA or a local HGSOC patient cohort. Taken together, our results suggest that the integrin–FAK signaling axis and c-Myc synergistically drive cell proliferation, survival and oncogenic potential in HGSOC. As such, our study provides key genetic, functional and signaling bases for the small-molecule-based co-targeting of these two distinct oncogenic drivers as a new line of targeted therapy against human ovarian cancer
Does or did the supernova remnant Cassiopeia A operate as a PeVatron?
For decades, supernova remnants (SNRs) have been considered the prime sources
of Galactic Cosmic rays (CRs). But whether SNRs can accelerate CR protons to
PeV energies and thus dominate CR flux up to the knee is currently under
intensive theoretical and phenomenological debate. The direct test of the
ability of SNRs to operate as CR PeVatrons can be provided by ultrahigh-energy
(UHE; ~TeV) -rays. In this context, the historical
SNR Cassiopeia A (Cas A) is considered one of the most promising target for UHE
observations. This paper presents the observation of Cas A and its vicinity by
the LHAASO KM2A detector. The exceptional sensitivity of LHAASO KM2A in the UHE
band, combined with the young age of Cas A, enabled us to derive stringent
model-independent limits on the energy budget of UHE protons and nuclei
accelerated by Cas A at any epoch after the explosion. The results challenge
the prevailing paradigm that Cas A-type SNRs are major suppliers of PeV CRs in
the Milky Way.Comment: 11 pages, 3 figures, Accepted by the APJ
Measurement of ultra-high-energy diffuse gamma-ray emission of the Galactic plane from 10 TeV to 1 PeV with LHAASO-KM2A
The diffuse Galactic -ray emission, mainly produced via interactions
between cosmic rays and the interstellar medium and/or radiation field, is a
very important probe of the distribution, propagation, and interaction of
cosmic rays in the Milky Way. In this work we report the measurements of
diffuse -rays from the Galactic plane between 10 TeV and 1 PeV
energies, with the square kilometer array of the Large High Altitude Air Shower
Observatory (LHAASO). Diffuse emissions from the inner
(, ) and outer
(, ) Galactic plane are detected with
and significance, respectively. The outer Galactic
plane diffuse emission is detected for the first time in the very- to
ultra-high-energy domain (~TeV). The energy spectrum in the inner Galaxy
regions can be described by a power-law function with an index of
, which is different from the curved spectrum as expected from
hadronic interactions between locally measured cosmic rays and the
line-of-sight integrated gas content. Furthermore, the measured flux is higher
by a factor of than the prediction. A similar spectrum with an index of
is found in the outer Galaxy region, and the absolute flux for
TeV is again higher than the prediction for hadronic
cosmic ray interactions. The latitude distributions of the diffuse emission are
consistent with the gas distribution, while the longitude distributions show
clear deviation from the gas distribution. The LHAASO measurements imply that
either additional emission sources exist or cosmic ray intensities have spatial
variations.Comment: 12 pages, 8 figures, 5 tables; accepted for publication in Physical
Review Letters; source mask file provided as ancillary fil
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