1,707 research outputs found
Velocity dependence of friction and Kramers relaxation rates
We study the influence of the velocity dependence of friction on the escape
of a Brownian particle from the deep potential well (,
is the barrier height, is the Boltzmann constant, is the
bath temperature). The bath-induced relaxation is treated within the Rayleigh
model (a heavy particle of mass in the bath of light particles of mass
) up to the terms of the order of ,
. The term is equivalent to the Fokker-Planck
dissipative operator, and the term is responsible for the
velocity dependence of friction. As expected, the correction to the Kramers
escape rate in the overdamped limit is proportional to and is
small. The corresponding correction in the underdamped limit is proportional to
and is not necessarily small. We thus suggest that
the effects due to the velocity-dependent friction may be of considerable
importance in determining the rate of escape of an under- and moderately damped
Brownian particle from a deep potential well, while they are of minor
importance for an overdamped particle
IR Dust Bubbles: Probing the Detailed Structure and Young Massive Stellar Populations of Galactic HII Regions
We present an analysis of wind-blown, parsec-sized, mid-infrared bubbles and
associated star-formation using GLIMPSE/IRAC, MIPSGAL/MIPS and MAGPIS/VLA
surveys. Three bubbles from the Churchwell et al. (2006) catalog were selected.
The relative distribution of the ionized gas (based on 20 cm emission), PAH
emission (based on 8 um, 5.8 um and lack of 4.5 um emission) and hot dust (24
um emission) are compared. At the center of each bubble there is a region
containing ionized gas and hot dust, surrounded by PAHs. We identify the likely
source(s) of the stellar wind and ionizing flux producing each bubble based
upon SED fitting to numerical hot stellar photosphere models. Candidate YSOs
are also identified using SED fitting, including several sites of possible
triggered star formation.Comment: 37 pages, 17 figure
Manifestation of nonequilibrium initial conditions in molecular rotation: the generalized J-diffusion model
In order to adequately describe molecular rotation far from equilibrium, we
have generalized the J-diffusion model by allowing the rotational relaxation
rate to be angular momentum dependent. The calculated nonequilibrium rotational
correlation functions (CFs) are shown to decay much slower than their
equilibrium counterparts, and orientational CFs of hot molecules exhibit
coherent behavior, which persists for several rotational periods. As distinct
from the results of standard theories, rotational and orientational CFs are
found to dependent strongly on the nonequilibrium preparation of the molecular
ensemble. We predict the Arrhenius energy dependence of rotational relaxation
times and violation of the Hubbard relations for orientational relaxation
times. The standard and generalized J-diffusion models are shown to be almost
indistinguishable under equilibrium conditions. Far from equilibrium, their
predictions may differ dramatically
ATLASGAL - towards a complete sample of massive star forming clumps
By matching infrared-selected, massive young stellar objects (MYSOs) and compact HII regions in the Red MSX Source survey to massive clumps found in the submillimetre ATLASGAL (APEX Telescope Large Area Survey of the Galaxy) survey, we have identified ~1000 embedded young massive stars between 280{ring operator} <lPeer reviewedFinal Accepted Versio
Chloroxine overrides DNA damage tolerance to restore platinum sensitivity in high-grade serous ovarian cancer
High-grade serous cancer (HGSC) accounts for ~67% of all ovarian cancer deaths. Although initially sensitive to
platinum chemotherapy, resistance is inevitable and there is an unmet clinical need for novel therapies that can
circumvent this event. We performed a drug screen with 1177 FDA-approved drugs and identified the
hydroxyquinoline drug, chloroxine. In extensive validation experiments, chloroxine restored sensitivity to both cisplatin
and carboplatin, demonstrating broad synergy in our range of experimental models of platinum-resistant HGSC.
Synergy was independent of chloroxineâs predicted ionophore activity and did not relate to platinum uptake as
measured by atomic absorption spectroscopy. Further mechanistic investigation revealed that chloroxine overrides
DNA damage tolerance in platinum-resistant HGSC. Co-treatment with carboplatin and chloroxine (but not either drug
alone) caused an increase in ÎłH2AX expression, followed by a reduction in platinum-induced RAD51 foci. Moreover,
this unrepaired DNA damage was associated with p53 stabilisation, cell cycle re-entry and triggering of caspase 3/7-
mediated cell death. Finally, in our platinum-resistant, intraperitoneal in vivo model, treatment with carboplatin alone
resulted in a transient tumour response followed by tumour regrowth. In contrast, treatment with chloroxine and
carboplatin combined, was able to maintain tumour volume at baseline for over 4 months. In conclusion, our novel
results show that chloroxine facilitates platinum-induced DNA damage to restore platinum sensitivity in HGSC. Since
chloroxine is already licensed, this exciting combination therapy could now be rapidly translated for patient benefit
High level of telomerase RNA gene expression is associated with chromatin modification, the ALT phenotype and poor prognosis in liposarcoma
Telomere length is maintained by two known mechanisms, activation of telomerase or alternative lengthening of telomeres (ALT). The ALT pathway is more commonly activated in tumours of mesenchymal origin, although the mechanisms involved in the decision of a cell to activate either telomerase or ALT are unknown at present and no molecular markers exist to define the ALT phenotype. We have previously shown an association between chromatin remodelling, telomerase gene expression and ALT in cell line models. Here, we evaluate these findings and investigate their prognostic significance in a panel of liposarcoma tissue samples to understand the biology underlying the ALT phenotype. Liposarcoma samples were split into three groups: telomerase positive (Tel+); ALT positive; ALTâ/Telâ. Differences in telomerase gene expression were evident between the groups with increased expression of hTR in ALT and Tel+ compared to ALTâ/Telâ samples and increased hTERT in Tel+ samples only. Investigation of a small panel of chromatin modifications revealed significantly increased binding of acetyl H3 in association with hTR expression. We confirm that the presence of the ALT phenotype is associated with poor prognosis and in addition, for the first time, we show a direct association between hTR expression and poor prognosis in liposarcoma patients
Derivation of the action and symmetries of the q-deformed AdS5ĂS5 superstring
This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits any use, distribution and reproduction in any medium, provided the original author(s) and source are credited.We recently proposed an integrable q-deformation of the AdS5 Ă S 5 superstring action. Here we give details on the hamiltonian origin and construction of this deformation. The procedure is a generalization of the one previously developed for deforming principal chiral and symmetric space Ï-modelsPeer reviewedFinal Published versio
Global Optimization by Basin-Hopping and the Lowest Energy Structures of Lennard-Jones Clusters Containing up to 110 Atoms
We describe a global optimization technique using `basin-hopping' in which
the potential energy surface is transformed into a collection of
interpenetrating staircases. This method has been designed to exploit the
features which recent work suggests must be present in an energy landscape for
efficient relaxation to the global minimum. The transformation associates any
point in configuration space with the local minimum obtained by a geometry
optimization started from that point, effectively removing transition state
regions from the problem. However, unlike other methods based upon hypersurface
deformation, this transformation does not change the global minimum. The lowest
known structures are located for all Lennard-Jones clusters up to 110 atoms,
including a number that have never been found before in unbiased searches.Comment: 8 pages, 3 figures, revte
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