9,033 research outputs found
Effect of Photobiomodulation on Vinblastine-Poisoned Murine HERS Cells
Objective: The aim of this study was to investigate the effect of near-infrared (NIR) photobiomodulation on the proliferation and glutathione levels in murine Hertwig\u27s epithelial root sheath (HERS) cells after poisoning with vinblastine. Background: Photobiomodulation has been shown to improve wound healing in a number of animal models. There have been no studies on the effect of photobiomodulation on cancer-related chemotherapy injury to the cells that initiate tooth root growth. Materials and Methods: Control groups consisted of murine HERS cells without vinblastine (VB−) and cells with vinblastine at 10, 20, and 30 ng/mL (VB10, VB20, and VB30). Experimental groups consisted of these same groups with light therapy (VB-L, VB10L, VB20L, and VB30L). The cells were exposed to vinblastine for 1 h. Photobiomodulation consisted of a 75-cm2 gallium-aluminum-arsenide light-emitting diode (LED) array at an energy density of 12.8 J/cm2, delivered with 50 mW/cm2 power over 256 s. Results: Vinblastine alone significantly decreased HERS cell proliferation and glutathione levels at all concentrations (VB10 [−55%, p \u3c 1.0 × 10−8]; VB20 [−72%, p \u3c 1.0 × 10−9]; VB30 [−80%, p \u3c 1.0 × 10−10]; and VB10 [−36%, p \u3c 0.0001]; VB20 [−49%, p \u3c 1.0 × 10−6]; VB30 [−53%, p \u3c 1.0 × 10−7] respectively). Photobiomodulation significantly increased cell proliferation at all levels of vinblastine exposure (VB10L [+50%, p \u3c 0.0001]; VB20L [+45%, p \u3c 0.05]; VB30 [+39%, p \u3c 0.05]) but not of the control (+22%, p = 0.063). The photobiomodulation significantly increased glutathione production in all concentrations of vinblastine except 20 ng/mL (VB10L [+39%, p = 0.007]; VB20L [+19%, p = 0.087]; VB30 [+14%, p = 0.025]) and the control (+12%, p = 0.13). Conclusions: Photobiomodulation demonstrated an improvement in proliferation and glutathione levels in vinblastine-poisoned murine HERS cells
On the Metallicity-Color Relations and Bimodal Color Distributions in Extragalactic Globular Cluster Systems
We perform a series of numerical experiments to study how the nonlinear
metallicity--color relations predicted by different stellar population models
affect the color distributions observed in extragalactic globular cluster
systems. % We present simulations in the bandpasses based on five
different sets of simple stellar population (SSP) models. The presence of
photometric scatter in the colors is included as well. % We find that unimodal
metallicity distributions frequently ``project'' into bimodal color
distributions. The likelihood of this effect depends on both the mean and
dispersion of the metallicity distribution, as well as of course on the SSP
model used for the transformation. % Adopting the Teramo-SPoT SSP models for
reference, we find that optical--to--near-IR colors should be favored with
respect to other colors to avoid the bias effect in globular cluster color
distributions discussed by \citet{yoon06}. In particular, colors such as \vh\
or \vk are more robust against nonlinearity of the metallicity--color relation,
and an observed bimodal distribution in such colors is more likely to indicate
a true underlying bimodal metallicity distribution. Similar conclusions come
from the simulations based on different SSP models, although we also identify
exceptions to this result.Comment: ApJ accepte
Method of remotely characterizing thermal properties of a sample
A sample in a wind tunnel is radiated from a thermal energy source outside of the wind tunnel. A thermal imager system, also located outside of the wind tunnel, reads surface radiations from the sample as a function of time. The produced thermal images are characteristic of the heat transferred from the sample to the flow across the sample. In turn, the measured rates of heat loss of the sample are characteristic of the flow and the sample
A glimpse at the flat-spacetime limit of quantum gravity using the Bekenstein argument in reverse
An insightful argument for a linear relation between the entropy and the area
of a black hole was given by Bekenstein using only the energy-momentum
dispersion relation, the uncertainty principle, and some properties of
classical black holes. Recent analyses within String Theory and Loop Quantum
Gravity describe black-hole entropy in terms of a dominant contribution, which
indeed depends linearly on the area, and a leading log-area correction. We
argue that, by reversing the Bekenstein argument, the log-area correction can
provide insight on the energy-momentum dispersion relation and the uncertainty
principle of a quantum-gravity theory. As examples we consider the
energy-momentum dispersion relations that recently emerged in the Loop Quantum
Gravity literature and the Generalized Uncertainty Principle that is expected
to hold in String Theory.Comment: 7 pages, LaTex; this essay received an "honorable mention" in the
2004 Essay Competition of the Gravity Research Foundation; submitted to IJMPD
on 23 June 2004; published as Int.J.Mod.Phys.D13:2337-2343,200
The Dystrophin-Glycoprotein Complex in the Prevention of Muscle Damage
Muscular dystrophies are genetically diverse but share common phenotypic features of muscle weakness, degeneration, and progressive decline in muscle function. Previous work has focused on understanding how disruptions in the dystrophin-glycoprotein complex result in muscular dystrophy, supporting a hypothesis that the muscle sarcolemma is fragile and susceptible to contraction-induced injury in multiple forms of dystrophy. Although benign in healthy muscle, contractions in dystrophic muscle may contribute to a higher degree of muscle damage which eventually overwhelms muscle regeneration capacity. While increased susceptibility of muscle to mechanical injury is thought to be an important contributor to disease pathology, it is becoming clear that not all DGC-associated diseases share this supposed hallmark feature. This paper outlines experimental support for a function of the DGC in preventing muscle damage and examines the evidence that supports novel functions for this complex in muscle that when impaired, may contribute to the pathogenesis of muscular dystrophy
Revealing the tidal scars of the Small Magellanic Cloud
Due to their close proximity, the Large and Small Magellanic Clouds (SMC/LMC)
provide natural laboratories for understanding how galaxies form and evolve.
With the goal of determining the structure and dynamical state of the SMC, we
present new spectroscopic data for 3000 SMC red giant branch stars
observed using the AAOmega spectrograph at the Anglo-Australian Telescope. We
complement our data with further spectroscopic measurements from previous
studies that used the same instrumental configuration and proper motions from
the \textit{Gaia} Data Release 2 catalogue. Analysing the photometric and
stellar kinematic data, we find that the SMC centre of mass presents a
conspicuous offset from the velocity centre of its associated \mbox{H\,{\sc
i}} gas, suggesting that the SMC gas is likely to be far from dynamical
equilibrium. Furthermore, we find evidence that the SMC is currently undergoing
tidal disruption by the LMC within 2\,kpc of the centre of the SMC, and
possibly all the way in to the very core. This is evidenced by a net outward
motion of stars from the SMC centre along the direction towards the LMC and
apparent tangential anisotropy at all radii. The latter is expected if the SMC
is undergoing significiant tidal stripping, as we demonstrate using a suite of
-body simulations of the SMC/LMC system disrupting around the Milky Way.
These results suggest that dynamical models for the SMC that assume a steady
state will need to be revisited.Comment: Revised version submitted to MNRAS after referee report, 18 pages, 18
figure
Ab initio quality neural-network potential for sodium
An interatomic potential for high-pressure high-temperature (HPHT)
crystalline and liquid phases of sodium is created using a neural-network (NN)
representation of the ab initio potential energy surface. It is demonstrated
that the NN potential provides an ab initio quality description of multiple
properties of liquid sodium and bcc, fcc, cI16 crystal phases in the P-T region
up to 120 GPa and 1200 K. The unique combination of computational efficiency of
the NN potential and its ability to reproduce quantitatively experimental
properties of sodium in the wide P-T range enables molecular dynamics
simulations of physicochemical processes in HPHT sodium of unprecedented
quality.Comment: 8 pages, 11 figures, 2 table
Topology and energy transport in networks of interacting photosynthetic complexes
We address the role of topology in the energy transport process that occurs
in networks of photosynthetic complexes. We take inspiration from light
harvesting networks present in purple bacteria and simulate an incoherent
dissipative energy transport process on more general and abstract networks,
considering both regular structures (Cayley trees and hyperbranched fractals)
and randomly-generated ones. We focus on the the two primary light harvesting
complexes of purple bacteria, i.e., the LH1 and LH2, and we use
network-theoretical centrality measures in order to select different LH1
arrangements. We show that different choices cause significant differences in
the transport efficiencies, and that for regular networks centrality measures
allow to identify arrangements that ensure transport efficiencies which are
better than those obtained with a random disposition of the complexes. The
optimal arrangements strongly depend on the dissipative nature of the dynamics
and on the topological properties of the networks considered, and depending on
the latter they are achieved by using global vs. local centrality measures. For
randomly-generated networks a random arrangement of the complexes already
provides efficient transport, and this suggests the process is strong with
respect to limited amount of control in the structure design and to the
disorder inherent in the construction of randomly-assembled structures.
Finally, we compare the networks considered with the real biological networks
and find that the latter have in general better performances, due to their
higher connectivity, but the former with optimal arrangements can mimic the
real networks' behaviour for a specific range of transport parameters. These
results show that the use of network-theoretical concepts can be crucial for
the characterization and design of efficient artificial energy transport
networks.Comment: 14 pages, 16 figures, revised versio
Linear Ramps of Interaction in the Fermionic Hubbard Model
We study the out of equilibrium dynamics of the Fermionic Hubbard Model
induced by a linear ramp of the repulsive interaction from the metallic
state through the Mott transition. To this extent we use a time dependent
Gutzwiller variational method and complement this analysis with the inclusion
of quantum fluctuations at the leading order, in the framework of a slave
spin theory. We discuss the dynamics during the ramp and the issue of
adiabaticity through the scaling of the excitation energy with the ramp
duration . In addition, we study the dynamics for times scales longer
than the ramp time, when the system is again isolated and the total energy
conserved. We establish the existence of a dynamical phase transition analogous
to the one present in the sudden quench case and discuss its properties as a
function of final interaction and ramp duration. Finally we discuss the role of
quantum fluctuations on the mean field dynamics for both long ramps, where spin
wave theory is sufficient, and for very short ramps, where a self consistent
treatment of quantum fluctuations is required in order to obtain relaxation.Comment: v2: 19 pages, 14 figures, published versio
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