11,461 research outputs found
Astrocyte production of the chemokine macrophage inflammatory protein-2 is inhibited by the spice principle curcumin at the level of gene transcription
BACKGROUND: In neuropathological processes associated with neutrophilic infiltrates, such as experimental allergic encephalitis and traumatic injury of the brain, the CXC chemokine, macrophage inflammatory protein-2 (MIP-2) is thought to play a pivotal role in the induction and perpetuation of inflammation in the central nervous system (CNS). The origin of MIP-2 in inflammatory disorders of the brain has not been fully defined but astrocytes appear to be a dominant source of this chemokine. Curcumin is a spice principle in, and constitutes approximately 4 percent of, turmeric. Curcumin's immunomodulating and antioxidant activities suggest that it might be a useful adjunct in the treatment of neurodegenerative illnesses characterized by inflammation. Relatively unexplored, but relevant to its potential therapeutic efficacy in neuroinflammatory syndromes is the effect of curcumin on chemokine production. To examine the possibility that curcumin may influence CNS inflammation by mechanisms distinct from its known anti-oxidant activities, we studied the effect of this spice principle on the synthesis of MIP-2 by astrocytes. METHODS: Primary astrocytes were prepared from neonatal brains of CBA/CaJ mice. The cells were stimulated with lipopolysaccharide in the presence or absence of various amount of curcumin or epigallocatechin gallate. MIP-2 mRNA was analyzed using semi-quantitative PCR and MIP-2 protein production in the culture supernatants was quantified by ELISA. Astrocytes were transfected with a MIP-2 promoter construct, pGL3-MIP-2, and stimulated with lipopolysaccharide in the presence or absence of curcumin. RESULTS: The induction of MIP-2 gene expression and the production of MIP-2 protein were inhibited by curcumin. Curcumin also inhibited lipopolysaccharide-induced transcription of the MIP-2 promoter reporter gene construct in primary astrocytes. However MIP-2 gene induction by lipopolysaccharide was not inhibited by another anti-oxidant, epigallocatechin gallate. CONCLUSION: Our results indicate that curcumin potently inhibits MIP-2 production at the level of gene transcription and offer further support for its potential use in the treatment of inflammatory conditions of the CNS
Planar Laser Imaging of Sprays for Liquid Rocket Studies
A planar laser imaging technique which incorporates an optical polarization ratio technique for droplet size measurement was studied. A series of pressure atomized water sprays were studied with this technique and compared with measurements obtained using a Phase Doppler Particle Analyzer. In particular, the effects of assuming a logarithmic normal distribution function for the droplet size distribution within a spray was evaluated. Reasonable agreement between the instrument was obtained for the geometric mean diameter of the droplet distribution. However, comparisons based on the Sauter mean diameter show larger discrepancies, essentially because of uncertainties in the appropriate standard deviation to be applied for the polarization ratio technique. Comparisons were also made between single laser pulse (temporally resolved) measurements with multiple laser pulse visualizations of the spray
Quantum baker maps with controlled-NOT coupling
The characteristic stretching and squeezing of chaotic motion is linearized
within the finite number of phase space domains which subdivide a classical
baker map. Tensor products of such maps are also chaotic, but a more
interesting generalized baker map arises if the stacking orders for the factor
maps are allowed to interact. These maps are readily quantized, in such a way
that the stacking interaction is entirely attributed to primary qubits in each
map, if each subsystem has power-of-two Hilbert space dimension. We here study
the particular example of two baker maps that interact via a controlled-not
interaction. Numerical evidence indicates that the control subspace becomes an
ideal Markovian environment for the target map in the limit of large Hilbert
space dimension.Comment: 8 page
Electroproduction of phi(1020) mesons at 1.4 \u3c= Q(2) \u3c= 3.8 GeV2 measured with the CLAS spectrometer
Electroproduction of exclusive Ď• vector mesons has been studied with the CLAS detector in the kinematic range 1.
Exactly quantized dynamics of classical incommensurate sliders
We report peculiar velocity quantization phenomena in the classical motion of
an idealized 1D solid lubricant, consisting of a harmonic chain interposed
between two periodic sliders. The ratio v_cm/v_ext of the chain center-of-mass
velocity to the externally imposed relative velocity of the sliders stays
pinned to exact "plateau" values for wide ranges of parameters, such as sliders
corrugation amplitudes, external velocity, chain stiffness and dissipation, and
is strictly determined by the commensurability ratios alone. The phenomenon is
explained by one slider rigidly dragging the kinks that the chain forms with
the other slider. Possible consequences of these results for some real systems
are discussed.Comment: 5 pags 4 fig
Quantization of multidimensional cat maps
In this work we study cat maps with many degrees of freedom. Classical cat
maps are classified using the Cayley parametrization of symplectic matrices and
the closely associated center and chord generating functions. Particular
attention is dedicated to loxodromic behavior, which is a new feature of
two-dimensional maps. The maps are then quantized using a recently developed
Weyl representation on the torus and the general condition on the Floquet
angles is derived for a particular map to be quantizable. The semiclassical
approximation is exact, regardless of the dimensionality or of the nature of
the fixed points.Comment: 33 pages, latex, 6 figures, Submitted to Nonlinearit
Spin liquid ground state in a two dimensional non-frustrated spin model
We consider an exchange model describing two isotropic spin-1/2 Heisenberg
antiferromagnets coupled by a quartic term on the square lattice. The model is
relevant for systems with orbital degeneracy and strong electron-vibron
coupling in the large Hubbard repulsion limit, and is known to show a
spin-Peierls-like dimerization in one dimension. In two dimensions we calculate
energy gaps, susceptibilities, and correlation functions with a Green's
Function Monte Carlo. We find a finite spin gap and no evidence of any kind of
order. We conclude that the ground state is, most likely, a spin liquid of
resonating valence bonds.Comment: 4 pages, 4 figures, Revte
Strong Correlations in Electron Doped Phthalocyanine Conductors Near Half Filling
We propose that electron doped nontransition metal-phthalocyanines (MPc) like
ZnPc and MgPc, similar to those very recently reported, should constitute novel
strongly correlated metals. Due to orbital degeneracy, Jahn-Teller coupling and
Hund's rule exchange, and with a large on-site Coulomb repulsion, these
molecular conductors should display, particularly near half filling at two
electrons/molecule, very unconventional properties, including Mott insulators,
strongly correlated superconductivity, and other intriguing phases.Comment: 4 pages, 1 figure, submited to PR
Valence-bond states in dynamical Jahn-Teller molecular systems
We discuss a hopping model of electrons between idealized molecular sites
with local orbital degeneracy and dynamical Jahn-Teller effect, for crystal
field environments of sufficiently high symmetry. For the Mott-insulating case
(one electron per site and large Coulomb repulsions), in the simplest two-fold
degenerate situation, we are led to consider a particular exchange hamiltonian,
describing two isotropic spin-1/2 Heisenberg problems coupled by a quartic term
on equivalent bonds. This twin-exchange hamiltonian applies to a physical
regime in which the inter-orbital singlet is the lowest-energy intermediate
state available for hopping. This regime is favored by a relatively strong
electron-phonon coupling. Using variational arguments, a large-N limit, and
exact diagonalization data, we find that the ground state, in the one
dimensional case, is a solid valence bond state. The situation in the two
dimensional case is less clear. Finally, the behavior of the system upon hole
doping is studied in one dimension.Comment: 11 pages, 5 figure
Convergence theorems for quantum annealing
We prove several theorems to give sufficient conditions for convergence of
quantum annealing, which is a protocol to solve generic optimization problems
by quantum dynamics. In particular the property of strong ergodicity is proved
for the path-integral Monte Carlo implementation of quantum annealing for the
transverse Ising model under a power decay of the transverse field. This result
is to be compared with the much slower inverse-log decay of temperature in the
conventional simulated annealing. Similar results are proved for the Green's
function Monte Carlo approach. Optimization problems in continuous space of
particle configurations are also discussed.Comment: 19 page
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