1,975 research outputs found
Flux-tube Structure, Sum Rules and Beta-functions in SU(2)
Action and energy flux-tube profiles are computed, in SU(2) with
beta=2.4,2.5, for two quarks up to 1 fm apart and for which the colour fields
are in their ground state (A_1g) and the first (E_u) and higher (A'_1g) excited
gluonic states. When these profiles are integrated over all space, a scaling
comparison is made between the beta=2.4 and 2.5 data. Using sum rules, these
integrated forms also permit an estimate to be made of generalised
beta-functions giving b(2.4)=-0.312(15), b(2.5)=-0.323(9), f(2.4)=0.65(1) and
f(2.5)=0.68(1). When the profiles are integrated only over planes transverse to
the interquark line and assuming underlying string features, scaling
comparisons are again made near the centres of the interquark line for the
largest interquark distances. For the A'_{1g} case, some of the profiles
exhibit a 'dip-like' structure characteristic of the Isgur-Paton model.Comment: 3 pages, 6 eps figures. Presented at LATTICE9
Effective String Theory of Vortices and Regge Trajectories
Starting from a field theory containing classical vortex solutions, we obtain
an effective string theory of these vortices as a path integral over the two
transverse degrees of freedom of the string. We carry out a semiclassical
expansion of this effective theory, and use it to obtain corrections to Regge
trajectories due to string fluctuations.Comment: 27 pages, revtex, 3 figures, corrected an error with the cutoff in
appendix E (was previously D), added more discussion of Fig. 3, moved some
material in section 9 to a new appendi
Chondrocytes respond to adenosine via A2receptors and activity is potentiated by an adenosine deaminase inhibitor and a phosphodiesterase inhibitor
AbstractObjective To test the mechanisms by which adenosine and adenosine analogues stimulate adenylate cyclase and suppress lipopolysaccharide (LPS)-induced production of nitric oxide (NO) by chondrocytes.Methods Primary chondrocytes isolated from equine articular cartilage were plated in monolayer. Intracellular cyclic-AMP (cAMP) accumulation was measured following exposure to medium containing adenosine, the non-hydrolyzable adenosine analogue N6-methyladenosine, the A2Aspecific agonist N6-(dimethoxyphenyl)-ethyl]adenosine (DPMA), the adenosine deaminase inhibitor erythro-9-(2-Hydroxy-3-nonyl)adenine hydrochloride (EHNA), or forskolin, a potent stimulator of adenylate cyclase. Regulation of NO production by LPS-stimulated chondrocytes, as determined by nitrite concentration, was assessed in the presence of adenosine, N6-methyladenosine, DPMA, the broad agonist 5âČ-N-ethylcarboxamidoadenosine (NECA), or forskolin. Alternatively, LPS-stimulated chondrocytes were exposed to EHNA or the phosphodiesterase inhibitor rolipram in the presence or absence of supplemental adenosine.Results Adenosine, N6-methyladenosine, DPMA, and forskolin each increased intracellular cAMP accumulation in a concentration-dependent manner and suppressed NO production by LPS-stimulated chondrocytes. NECA also decreased NO production by chondrocytes stimulated with LPS. Incubation with EHNA, to protect endogenously produced adenosine, or rolipram, which prevents the degradation of cAMP, similarly suppressed LPS-stimulated NO production. The addition of exogenous adenosine with EHNA or rolipram further suppressed NO production.Conclusions This study documents functional responses to adenosine by articular chondrocytes. These responses are mimicked by the A2Areceptor agonist, DPMA. Effects were enhanced by protecting adenosine using an adenosine deaminase inhibitor or by potentiating the cAMP response with rolipram. These experiments suggest that adenosine may play a physiological role in regulation of chondrocytes and that adenosine pathways could represent a novel target for therapeutic intervention
Stable long term engraftment and amelioration of clinical phenotype following hematopoietic stem cell transplantation from a matched sibling donor for sickle cell disease using a reduced intensity conditioning regimen
The Lazarus project: A pragmatic approach to binary black hole evolutions
We present a detailed description of techniques developed to combine 3D
numerical simulations and, subsequently, a single black hole close-limit
approximation. This method has made it possible to compute the first complete
waveforms covering the post-orbital dynamics of a binary black hole system with
the numerical simulation covering the essential non-linear interaction before
the close limit becomes applicable for the late time dynamics. To determine
when close-limit perturbation theory is applicable we apply a combination of
invariant a priori estimates and a posteriori consistency checks of the
robustness of our results against exchange of linear and non-linear treatments
near the interface. Once the numerically modeled binary system reaches a regime
that can be treated as perturbations of the Kerr spacetime, we must
approximately relate the numerical coordinates to the perturbative background
coordinates. We also perform a rotation of a numerically defined tetrad to
asymptotically reproduce the tetrad required in the perturbative treatment. We
can then produce numerical Cauchy data for the close-limit evolution in the
form of the Weyl scalar and its time derivative
with both objects being first order coordinate and tetrad invariant. The
Teukolsky equation in Boyer-Lindquist coordinates is adopted to further
continue the evolution. To illustrate the application of these techniques we
evolve a single Kerr hole and compute the spurious radiation as a measure of
the error of the whole procedure. We also briefly discuss the extension of the
project to make use of improved full numerical evolutions and outline the
approach to a full understanding of astrophysical black hole binary systems
which we can now pursue.Comment: New typos found in the version appeared in PRD. (Mostly found and
collected by Bernard Kelly
Observing Long Colour Flux Tubes in SU(2) Lattice Gauge Theory
We present results of a high statistics study of the chromo field
distribution between static quarks in SU(2) gauge theory on lattices of volumes
16^4, 32^4, and 48^3*64, with physical extent ranging from 1.3 fm up to 2.7 fm
at beta=2.5, beta=2.635, and beta=2.74. We establish string formation over
physical distances as large as 2 fm. The results are tested against Michael's
sum rules. A detailed investigation of the transverse action and energy flux
tube profiles is provided. As a by-product, we obtain the static lattice
potential in unpreceded accuracy.Comment: 66 pages, 29 figures, uuencoded latex file with epsfigures (450 K),
supplementary full colour figures are available via ftp, CERN-TH.7413/94
(extended version
Tricritical Behavior of Two-Dimensional Scalar Field Theories
We compute by Monte Carlo numerical simulations the critical exponents of
two-dimensional scalar field theories at the tricritical point.
The results are in agreement with the Zamolodchikov conjecture based on
conformal invariance.Comment: 13 pages, uuencode tar-compressed Postscript file, preprint numbers:
IF/UFRJ/25/94, DFTUZ 94.06 and NYU--TH--94/10/0
A probabilistic analysis of the next fit decreasing bin packing heuristic
A probabilistic analysis is presented of the Next Fit Decreasing bin packing heuristic, in which bins are opened to accomodate the items in order of decreasing size
CABYR is essential for fibrous sheath integrity and progressive motility in mouse spermatozoa
Ca<sup>2+</sup>-binding tyrosine-phosphorylation-regulated protein (CABYR) has been implicated in sperm physiological function in several in vitro studies. It has also been implicated as a potential cause of and diagnostic tool in asthenozoospermic human males. CABYR is known to be localized to the fibrous sheath, an accessory structure in the flagellar principal piece. Utilizing the CRISPRâCas9 technology, we have knocked out this gene in mice to understand its role in male fertility. <i>Cabyr</i>-knockout male mice showed severe subfertility with a defect in sperm motility as well as a significant disorganization in the fibrous sheath. Further, abnormal configuration of doublet microtubules was observed in the Cabyr-knockout spermatozoa, suggesting that the fibrous sheath is important for the correct organization of the axoneme. Our results show that it is the role of CABYR in the formation of the fibrous sheath that is essential for male fertility
Non-perturbative calculations for the effective potential of the symmetric and non-Hermitian field theoretic model
We investigate the effective potential of the symmetric
field theory, perturbatively as well as non-perturbatively. For the
perturbative calculations, we first use normal ordering to obtain the first
order effective potential from which the predicted vacuum condensate vanishes
exponentially as in agreement with previous calculations. For the
higher orders, we employed the invariance of the bare parameters under the
change of the mass scale to fix the transformed form totally equivalent to
the original theory. The form so obtained up to is new and shows that all
the 1PI amplitudes are perurbative for both and regions. For
the intermediate region, we modified the fractal self-similar resummation
method to have a unique resummation formula for all values. This unique
formula is necessary because the effective potential is the generating
functional for all the 1PI amplitudes which can be obtained via and thus we can obtain an analytic calculation for the 1PI
amplitudes. Again, the resummed from of the effective potential is new and
interpolates the effective potential between the perturbative regions.
Moreover, the resummed effective potential agrees in spirit of previous
calculation concerning bound states.Comment: 20 page
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