1,626 research outputs found
The proteosome inhibitor MG132 attenuates Retinoic Acid Receptor trans-activation and enhances trans-repression of Nuclear Factor ÎșB. Potential relevance to chemo-preventive interventions with retinoids
BACKGROUND: Nuclear factor kappa B (NFÎșB) is a pro-malignant transcription factor with reciprocal effects on pro-metastatic and anti-metastatic gene expression. Interestingly, NFÎșB blockade results in the reciprocal induction of retinoic acid receptors (RARs). Given the established property of RARs as negative regulators of malignant progression, we postulated that reciprocal interactions between NFÎșB and RARs constitute a signaling module in metastatic gene expression and malignant progression. Using Line 1 tumor cells as a model for signal regulation of metastatic gene expression, we investigated the reciprocal interactions between NFÎșB and RARs in response to the pan-RAR agonist, all-trans retinoic acid (at-RA) and the pan-RAR antagonist, AGN193109. RESULTS: At-RA [0.1â1 ÎŒM] dose-dependently activated RAR and coordinately trans-repressed NFÎșB, while AGN193109 [1â10 ÎŒM] dose-dependently antagonized the effects of at-RA. At-RA and AGN193109 reciprocally regulate pro-metastatic matrix metalloprotease 9 (MMP 9) and its endogenous inhibitor, the tissue inhibitor of metalloprotease 1 (TIMP 1), in a manner consistent with the putative roles of NFÎșB and RAR in malignant progression. Activation of RAR concurs with its ubiquitination and proteosomal degradation. Accordingly, the proteosome inhibitor, MG132 [5 ÎŒM], blocked RAR degradation, quelled RAR trans-activation and enhanced RAR trans-repression of NFÎșB. CONCLUSION: We conclude that reciprocal interactions between NFÎșB and RARs constitute a signaling module in metastatic gene expression and malignant progression and propose that the dissociative effect of proteosome inhibitors could be harnessed towards enhancing the anticancer activity of retinoids
Improved sensitivity of H.E.S.S.-II through the fifth telescope focus system
The Imaging Atmospheric Cherenkov Telescope (IACT) works by imaging the very
short flash of Cherenkov radiation generated by the cascade of relativistic
charged particles produced when a TeV gamma ray strikes the atmosphere. This
energetic air shower is initiated at an altitude of 10-30 km depending on the
energy and the arrival direction of the primary gamma ray. Whether the best
image of the shower is obtained by focusing the telescope at infinity and
measuring the Cherenkov photon angles or focusing on the central region of the
shower is a not obvious question. This is particularly true for large size IACT
for which the depth of the field is much smaller. We address this issue in
particular with the fifth telescope (CT5) of the High Energy Stereoscopic
System (H.E.S.S.); a 28 m dish large size telescope recently entered in
operation and sensitive to an energy threshold of tens of GeVs. CT5 is equipped
with a focus system, its working principle and the expected effect of focusing
depth on the telescope sensitivity at low energies (50-200 GeV) is discussed.Comment: In Proceedings of the 33rd International Cosmic Ray Conference
(ICRC2013), Rio de Janeiro (Brazil
Sensitivity to the KARMEN Timing Anomaly at MiniBooNE
We present sensitivities for the MiniBooNE experiment to a rare exotic pion
decay producing a massive particle, Q^0. This type of decay represents one
possible explanation for the timing anomaly reported by the KARMEN
collaboration. MiniBooNE will be able to explore an area of the KARMEN signal
that has not yet been investigated
Continuous Uniform Finite Time Stabilization of Planar Controllable Systems
Continuous homogeneous controllers are utilized in a full state feedback setting for the uniform finite time stabilization of a perturbed double integrator in the presence of uniformly decaying piecewise continuous disturbances. Semiglobal strong Lyapunov functions are identified to establish uniform asymptotic stability of the closed-loop planar system. Uniform finite time stability is then proved by extending the homogeneity principle of discontinuous systems to the continuous case with uniformly decaying piecewise continuous nonhomogeneous disturbances. A finite upper bound on the settling time is also computed. The results extend the existing literature on homogeneity and finite time stability by both presenting uniform finite time stabilization and dealing with a broader class of nonhomogeneous disturbances for planar controllable systems while also proposing a new class of homogeneous continuous controllers
A Fixed-Target ExpeRiment at the LHC (AFTER@LHC) : luminosities, target polarisation and a selection of physics studies
We report on a future multi-purpose fixed-target experiment with the proton
or lead ion LHC beams extracted by a bent crystal. The multi-TeV LHC beams
allow for the most energetic fixed-target experiments ever performed. Such an
experiment, tentatively named AFTER for "A Fixed-Target ExperRiment", gives
access to new domains of particle and nuclear physics complementing that of
collider experiments, in particular at RHIC and at the EIC projects. The
instantaneous luminosity at AFTER using typical targets surpasses that of RHIC
by more than 3 orders of magnitude. Beam extraction by a bent crystal offers an
ideal way to obtain a clean and very collimated high-energy beam, without
decreasing the performance of the LHC. The fixed-target mode also has the
advantage of allowing for spin measurements with a polarised target and for an
access over the full backward rapidity domain up to xF ~ - 1. Here, we
elaborate on the reachable luminosities, the target polarisation and a
selection of measurements with hydrogen and deuterium targets.Comment: 6 pages. Proceedings of the Sixth International Conference on Quarks
and Nuclear Physics QNP2012 (16-20 April 2012, Ecole Polytechnique,
Palaiseau,France
Spin physics at A Fixed-Target ExpeRiment at the LHC (AFTER@LHC)
We outline the opportunities for spin physics which are offered by a next
generation and multi-purpose fixed-target experiment exploiting the proton LHC
beam extracted by a bent crystal. In particular, we focus on the study of
single transverse spin asymetries with the polarisation of the target.Comment: Contributed to the 20th International Spin Physics Symposium,
SPIN2012, 17-22 September 2012, Dubna, Russia, 4 pages, LaTe
Thermodynamics of self-gravitating systems
Self-gravitating systems are expected to reach a statistical equilibrium
state either through collisional relaxation or violent collisionless
relaxation. However, a maximum entropy state does not always exist and the
system may undergo a ``gravothermal catastrophe'': it can achieve ever
increasing values of entropy by developing a dense and hot ``core'' surrounded
by a low density ``halo''. In this paper, we study the phase transition between
``equilibrium'' states and ``collapsed'' states with the aid of a simple
relaxation equation [Chavanis, Sommeria and Robert, Astrophys. J. 471, 385
(1996)] constructed so as to increase entropy with an optimal rate while
conserving mass and energy. With this numerical algorithm, we can cover the
whole bifurcation diagram in parameter space and check, by an independent
method, the stability limits of Katz [Mon. Not. R. astr. Soc. 183, 765 (1978)]
and Padmanabhan [Astrophys. J. Supp. 71, 651 (1989)]. When no equilibrium state
exists, our relaxation equation develops a self-similar collapse leading to a
finite time singularity.Comment: 54 pages. 25 figures. Submitted to Phys. Rev.
Prospectives for A Fixed-Target ExpeRiment at the LHC: AFTER@LHC
We argue that the concept of a multi-purpose fixed-target experiment with the
proton or lead-ion LHC beams extracted by a bent crystal would offer a number
of ground-breaking precision-physics opportunities. The multi-TeV LHC beams
will allow for the most energetic fixed-target experiments ever performed. The
fixed-target mode has the advantage of allowing for high luminosities, spin
measurements with a polarised target, and access over the full backward
rapidity domain --uncharted until now-- up to x_F ~ -1.Comment: 6 pages, 1 table, LaTeX. Proceedings of the 36th International
Conference on High Energy Physics (ICHEP2012), 4-11 July 2012, Melbourne,
Australi
Prediction of interaction between a side overflow and bed-load transport in a channel with semi-empirical approaches
Les seuils a deversoir lateral sont des structures de controle et de detournement a ecoulement libre regulierement utilisees en ingenierie de lutte contre les inondations. La perte laterale d'eau permet de reduire la capacite de transport de la charge de fond dans le chenal principal, engendrant ainsi une deposition locale des sediments pres du deversoir lateral. Le debordement servant aux calculs est donc augmente de maniere non controlee. Des experiences systematiques de canal sur appuis ont ete realisees puisque cette interaction ecoulement-sediments dans un tel canal n'avait jamais ete etudiee. Base sur ces experiences, un modele empirique bidimensionnel a ete developpe afin de decrire l'evolution longitudinale de la portion du canal alluvial a proximite du deversoir. De plus, une approche simple et explicite d'estimation directe de l'ecoulement lateral avec transport de la charge de fond a ete determinee. Pour etre applicables a l'ingenierie, les variables d'entree sont exprimees en termes de parametres sans dimensions. Finalement, l'utilisation des modeles est demontree sur une etude de cas du Rhone en Suisse
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