81 research outputs found
Membrane, Four-Brane and Dual Coordinates in the M(atrix) Theory Compactified on Tori
In the M(atrix) theory by making the expansions of the matrices around the
membrane and four-brane solutions we derive the three- and five-dimensional
gauge theories on the dual tori. The explicit forms of solutions yield the dual
coordinates and each expansion is related to a toroidal compactification of the
M(atrix) theory. From the derived Lorentz and gauge invariant actions the gauge
coupling constants are shown to be characterized by the volume of the dual
tori.Comment: 9 pages, latex, no figure
Classical Equations for Quantum Systems
The origin of the phenomenological deterministic laws that approximately
govern the quasiclassical domain of familiar experience is considered in the
context of the quantum mechanics of closed systems such as the universe as a
whole. We investigate the requirements for coarse grainings to yield decoherent
sets of histories that are quasiclassical, i.e. such that the individual
histories obey, with high probability, effective classical equations of motion
interrupted continually by small fluctuations and occasionally by large ones.
We discuss these requirements generally but study them specifically for coarse
grainings of the type that follows a distinguished subset of a complete set of
variables while ignoring the rest. More coarse graining is needed to achieve
decoherence than would be suggested by naive arguments based on the uncertainty
principle. Even coarser graining is required in the distinguished variables for
them to have the necessary inertia to approach classical predictability in the
presence of the noise consisting of the fluctuations that typical mechanisms of
decoherence produce. We describe the derivation of phenomenological equations
of motion explicitly for a particular class of models. Probabilities of the
correlations in time that define equations of motion are explicitly considered.
Fully non-linear cases are studied. Methods are exhibited for finding the form
of the phenomenological equations of motion even when these are only distantly
related to those of the fundamental action. The demonstration of the connection
between quantum-mechanical causality and causalty in classical phenomenological
equations of motion is generalized. The connections among decoherence, noise,
dissipation, and the amount of coarse graining necessary to achieve classical
predictability are investigated quantitatively.Comment: 100pages, 1 figur
Gauge Theory of the String Geodesic Field
A relativistic string is usually represented by the Nambu-Goto action in
terms of the extremal area of a 2-dimensional timelike submanifold of Minkowski
space. Alternatively, a family of classical solutions of the string equation of
motion can be globally described in terms of the associated geodesic field. In
this paper we propose a new gauge theory for the geodesic field of closed and
open strings. Our approach solves the technical and conceptual problems
affecting previous attempts to describe strings in terms of local field
variables. The connection between the geodesic field, the string current and
the Kalb-Ramond gauge potential is discussed and clarified. A non-abelian
generalization and the generally covariant form of the model are also
discussed.Comment: 38 pages, PHYZZX, UTS-DFT-92-2
Solvable model of strings in a time-dependent plane-wave background
We investigate a string model defined by a special plane-wave metric ds^2 =
2dudv - l(u) x^2 du^2 + dx^2 with l(u) = k/u^2 and k=const > 0. This metric is
a Penrose limit of some cosmological, Dp-brane and fundamental string
backgrounds. Remarkably, in Rosen coordinates the metric has a ``null
cosmology'' interpretation with flat spatial sections and scale factor which is
a power of the light-cone time u. We show that: (i) This spacetime is a
Lorentzian homogeneous space. In particular, like Minkowski space, it admits a
boost isometry in u,v. (ii) It is an exact solution of string theory when
supplemented by a u-dependent dilaton such that its exponent (i.e. effective
string coupling) goes to zero at u=infinity and at the singularity u=0,
reducing back-reaction effects. (iii) The classical string equations in this
background become linear in the light-cone gauge and can be solved explicitly
in terms of Bessel's functions; thus the string model can be directly
quantized. This allows one to address the issue of singularity at the
string-theory level. We examine the propagation of first-quantized
point-particle and string modes in this time-dependent background. Using
certain analytic continuation prescription we argue that string propagation
through the singularity can be smooth.Comment: 58 pages, latex. v2: several references to related previous work
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Identification of the HSPB4/TLR2/NF-κB axis in macrophage as a therapeutic target for sterile inflammation of the cornea
Sterile inflammation underlies many diseases of the cornea including serious chemical burns and the common dry eye syndrome. In search for therapeutic targets for corneal inflammation, we defined the kinetics of neutrophil infiltration in a model of sterile injury to the cornea and identified molecular and cellular mechanisms triggering inflammatory responses. Neutrophil infiltration occurred in two phases: a small initial phase (Phase I) that began within 15 min after injury, and a larger second phase (Phase II) that peaked at 24–48 h. Temporal analysis suggested that the neuropeptide secretoneurin initiated Phase I without involvement of resident macrophages. Phase II was initiated by the small heat shock protein HSPB4 that was released from injured keratocytes and that activated resident macrophages via the TLR2/NF-κB pathway. The Phase II inflammation was responsible for vision-threatening opacity and was markedly suppressed by different means of inhibition of the HSPB4/TLR2/NF-κB axis: in mice lacking HSPB4 or TLR2, by antibodies to HSPB4 or by TNF-α stimulated gene/protein 6 that CD44-dependently inhibits the TLR2/NF-κB pathway. Therefore, our data identified the HSPB4/TLR2/NF-κB axis in macrophages as an effective target for therapy of corneal inflammation
Semiclassical Strings, Dipole Deformations of N=1 SYM and Decoupling of KK Modes
In this paper we investigate the recently found -deformed
Maldacena-Nunez background by studying the behavior of different semiclassical
string configurations. This background is conjectured to be dual to dipole
deformations of SYM. We compare our results to those in the pure
Maldacena-Nunez background and show that the energies of our string
configurations are higher than in the undeformed background. Thinking in the
lines of (hep-th/0505100) we argue that this is an evidence for better
decoupling of the Kaluza-Klein modes from the pure SYM theory excitations.
Moreover we are able to find a limit of the background in which the string
energy is independent of , these strings are interpreted as
corresponding to pure gauge theory effects.Comment: 31 pages, references added, new solutions in Section 7 presented, an
appendix added, to appear in JHE
D1-brane in beta-Deformed Background
We study various configurations of rotating and wound D1-brane in AdS_5\times
S^5 background and in its beta deformed version. We find giant magnon and spike
solutions on the world-volume of D1-brane in AdS_5\times S^5 background. We
also analyse the equations of motion of D1-brane in beta-deformed background.
We show that in the limit of large electric flux on world-volume of D1-brane
they reduce to the equations that describe collection of large number of
fundamental strings. We also construct rotating and wound D1-brane solution
that has two equal spins on S^5_\gamma.Comment: 26 pages, appendices and a reference added, to appear in JHE
Green-Schwarz Strings in TsT-transformed backgrounds
We consider classical strings propagating in a background generated by a
sequence of TsT transformations. We describe a general procedure to derive the
Green-Schwarz action for strings. We show that the U(1) isometry variables of
the TsT-transformed background are related to the isometry variables of the
initial background in a universal way independent of the details of the
background. This allows us to prove that strings in the TsT-transformed
background are described by the Green-Schwarz action for strings in the initial
background subject to twisted boundary conditions. Our construction implies
that a TsT transformation preserves integrability properties of the string
sigma model. We discuss in detail type IIB strings propagating in the
\g_i-deformed AdS_5 x S^5 space-time, find the twisted boundary conditions for
bosons and fermions, and use them to write down an explicit expression for the
monodromy matrix. We also discuss string zero modes whose dynamics is governed
by a fermionicgeneralization of the integrable Neumann model.Comment: 33 pages, latex, v2: typos correcte
Solulin reduces infarct volume and regulates gene-expression in transient middle cerebral artery occlusion in rats
<p>Abstract</p> <p>Background</p> <p>Thrombolysis after acute ischemic stroke has only proven to be beneficial in a subset of patients. The soluble recombinant analogue of human thrombomodulin, Solulin, was studied in an <it>in vivo </it>rat model of acute ischemic stroke.</p> <p>Methods</p> <p>Male SD rats were subjected to 2 hrs of transient middle cerebral artery occlusion (tMCAO). Rats treated with Solulin intravenously shortly before reperfusion were compared to rats receiving normal saline i.v. with respect to infarct volumes, neurological deficits and mortality. Gene expression of IL-6, IL-1β, TNF-α, MMP-9, CD11B and GFAP were semiquantitatively analyzed by rtPCR of the penumbra.</p> <p>Results</p> <p>24 hrs after reperfusion, rats were neurologically tested, euthanized and infarct volumes determined. Solulin significantly reduced mean total (p = 0.001), cortical (p = 0.002), and basal ganglia (p = 0.036) infarct volumes. Hippocampal infarct volumes (p = 0.191) were not significantly affected. Solulin significantly downregulated the expression of IL-1β (79%; p < 0.001), TNF-α (59%; p = 0.001), IL-6 (47%; p = 0.04), and CD11B (49%; p = 0.001) in the infarcted cortex compared to controls.</p> <p>Conclusions</p> <p>Solulin reduced mean total, cortical and basal ganglia infarct volumes and regulated a subset of cytokines and proteases after tMCAO suggesting the potency of this compound for therapeutic interventions.</p
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