10,757 research outputs found
Synchronization in driven versus autonomous coupled chaotic maps
The phenomenon of synchronization occurring in a locally coupled map lattice
subject to an external drive is compared to the synchronization process in an
autonomous coupled map system with similar local couplings plus a global
interaction. It is shown that chaotic synchronized states in both systems are
equivalent, but the collective states arising after the chaotic synchronized
state becomes unstable can be different in these two systems. It is found that
the external drive induces chaotic synchronization as well as synchronization
of unstable periodic orbits of the local dynamics in the driven lattice. On the
other hand, the addition of a global interaction in the autonomous system
allows for chaotic synchronization that is not possible in a large coupled map
system possessing only local couplings.Comment: 4 pages, 3 figs, accepted in Phys. Rev.
Renormalization group improvement of the NRQCD Lagrangian and heavy quarkonium spectrum
We complete the leading-log renormalization group scaling of the NRQCD
Lagrangian at . The next-to-next-to-leading-log renormalization group
scaling of the potential NRQCD Lagrangian (as far as the singlet is concerned)
is also obtained in the situation . As a
by-product, we obtain the heavy quarkonium spectrum with the same accuracy in
the situation m\alpha_s^2 \simg \Lambda_{QCD}. When , this is equivalent to obtain the whole set of
terms in the heavy quarkonium spectrum.
The implications of our results in the non-perturbative situation are also mentioned.Comment: 16 pages, LaTeX. Minor changes. Final versio
Renormalization group improvement of the spectrum of Hydrogen-like atoms with massless fermions
We obtain the next-to-next-to-leading-log renormalization group improvement
of the spectrum of Hydrogen-like atoms with massless fermions by using
potential NRQED. These results can also be applied to the computation of the
muonic Hydrogen spectrum where we are able to reproduce some known double logs
at O(m\alpha^6). We compare with other formalisms dealing with log resummation
available in the literature.Comment: 9 pages, LaTeX. Minor changes, note added, final versio
Effective field theories for heavy quarkonium
We review recent theoretical developments in heavy quarkonium physics from
the point of view of Effective Field Theories of QCD. We discuss
Non-Relativistic QCD and concentrate on potential Non-Relativistic QCD. Our
main goal will be to derive QCD Schr\"odinger-like equations that govern the
heavy quarkonium physics in the weak and strong coupling regime. We also
discuss a selected set of applications, which include spectroscopy, inclusive
decays and electromagnetic threshold production.Comment: 162 pages, 30 figures, revised version, references added. Accepted
for publication in Reviews of Modern Physic
Lessons from helminth infections: ES-62 highlights new interventional approaches in rheumatoid arthritis
Parasitic worms are able to survive in their mammalian host for many years due to their ability to manipulate the immune response by secreting immunomodulatory products. It is increasingly clear that, reflecting the anti-inflammatory actions of such worm-derived immunomodulators, there is an inverse correlation between helminth infection and autoimmune diseases in the developing world. As the decrease in helminth infections due to increased sanitation has correlated with an alarming increase in prevalence of such disorders in industrialised countries, this "Hygiene Hypothesis" has led to the proposal that worms and their secreted products offer a novel platform for the development of safe and effective strategies for the treatment of autoimmune disorders. Here we review the anti-inflammatory effects of one such immunomodulator, ES-62 on innate and adaptive immune responses and the mechanisms it exploits to afford protection in the murine Collagen Induced Arthritis (CIA) model of rheumatoid arthritis (RA). As its core mechanism involves targeting of IL-17 responses, which despite being pathogenic in RA are important for combating infection, we discuss how its selective targeting of IL-17 production by Th17 and γδ T cells, whilst leaving that of CD49b+ Natural Killer (NK and NK T) cells intact, reflects the ability of helminths to modulate the immune system without immunocompromising the host. Exploiting helminth immunomodulatory mechanisms therefore offers the potential for safer therapies than current biologics, such as "IL-17 blockers", that are not able to discriminate sources of IL-17 and hence present adverse effects that limit their therapeutic potential
Ultrasoft Renormalization in Non-Relativistic QCD
For Non-Relativistic QCD the velocity renormalization group correlates the
renormalization scales for ultrasoft, potential and soft degrees of freedom.
Here we discuss the renormalization of operators by ultrasoft gluons. We show
that renormalization of soft vertices can induce new operators, and also
present a procedure for correctly subtracting divergences in mixed
potential-ultrasoft graphs. Our results affect the running of the
spin-independent potentials in QCD. The change for the NNLL t-tbar cross
section near threshold is very small, being at the 1% level and essentially
independent of the energy. We also discuss implications for analyzing
situations where mv^2 ~ Lambda_QCD.Comment: 31 pages, 11 fig
Soft, collinear and non-relativistic modes in radiative decays of very heavy quarkonium
We analyze the end-point region of the photon spectrum in semi-inclusive
radiative decays of very heavy quarkonium (m alpha_s^2 >> Lambda_QCD). We
discuss the interplay of the scales arising in the Soft-Collinear Effective
Theory, m, m(1-z)^{1/2} and m(1-z) for z close to 1, with the scales of heavy
quarkonium systems in the weak coupling regime, m, m alpha_s and m alpha_s^2.
For 1-z \sim alpha_s^2 only collinear and (ultra)soft modes are seen to be
relevant, but the recently discovered soft-collinear modes show up for 1-z <<
alpha_s^2. The S- and P-wave octet shape functions are calculated. When they
are included in the analysis of the photon spectrum of the Upsilon (1S) system,
the agreement with data in the end-point region becomes excellent. The NRQCD
matrix elements and
are also obtained.Comment: Revtex, 11 pages, 6 figures. Minor improvements and references added.
Journal versio
Renormalization group scaling in nonrelativistic QCD
We discuss the matching conditions and renormalization group evolution of
non-relativistic QCD. A variant of the conventional MS-bar scheme is proposed
in which a subtraction velocity nu is used rather than a subtraction scale mu.
We derive a novel renormalization group equation in velocity space which can be
used to sum logarithms of v in the effective theory. We apply our method to
several examples. In particular we show that our formulation correctly
reproduces the two-loop anomalous dimension of the heavy quark production
current near threshold.Comment: (27 pages, revtex
Drug-like analogues of the parasitic worm-derived immunomodulator ES-62 are therapeutic in the MRL/Lpr model of systemic lupus erythematosus
Introduction ES-62, a phosphorylcholine (PC)-containing immunomodulator secreted by the parasitic worm Acanthocheilonema viteae, protects against nephritis in the MRL/Lpr mouse model of systemic lupus erythematosus (SLE). However, ES-62 is not suitable for development as a therapy and thus we have designed drug-like small molecule analogues (SMAs) based around its active PC-moiety. To provide proof of concept that ES-62-based SMAs exhibit therapeutic potential in SLE, we have investigated the capacity of two SMAs to protect against nephritis when administered to MRL/Lpr mice after onset of kidney damage.
Methods SMAs 11a and 12b were evaluated for their ability to suppress antinuclear antibody (ANA) generation and consequent kidney pathology in MRL/Lpr mice when administered after the onset of proteinuria.
Results SMAs 11a and 12b suppressed development of ANA and proteinuria. Protection reflected downregulation of MyD88 expression by kidney cells and this was associated with reduced production of IL-6, a cytokine that exhibits promise as a therapeutic target for this condition.
Conclusions SMAs 11a and 12b provide proof of principle that synthetic compounds based on the safe immunomodulatory mechanisms of parasitic worms can exhibit therapeutic potential as a novel class of drugs for SLE, a disease for which current therapies remain inadequate
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