1,524 research outputs found
Chiral Symmetry in Light-front QCD
The definition of chiral transformations in light-front field theory is very
different from the conventional form in equal-time formalism. We study the
consistency of chiral transformations and chiral symmetry in light-front QCD
and derive a complete new light-front axial-vector current for QCD. The
breaking of chiral symmetry in light-front QCD is only associated with helicity
flip interaction between quarks and gluons. Remarkably, the new axial-vector
current does not contain the pion pole part so that the associate chiral charge
smoothly describes pion transitions for various hadronic processes.Comment: 15 pages, no figure, JHEP style, added reference and corrected typos
and some changed conten
Nonperturbative Description of Deep Inelastic Structure Functions in Light-Front QCD
We explore the deep inelastic structure functions of hadrons
nonperturbatively in an inverse power expansion of the light-front energy of
the probe in the framework of light-front QCD. We arrive at the general
expressions for various structure functions as the Fourier transform of matrix
elements of different components of bilocal vector and axial vector currents on
the light-front in a straightforward manner. The complexities of the structure
functions are mainly carried by the multi-parton wave functions of the hadrons,
while, the bilocal currents have a dynamically dependent yet simple structure
on the light-front in this description. We also present a novel analysis of the
power corrections based on light-front power counting which resolves some
ambiguities of the conventional twist analysis in deep inelastic processes.
Further, the factorization theorem and the scale evolution of the structure
functions are presented in this formalism by using old-fashioned light-front
time-ordered perturbation theory with multi-parton wave functions.
Nonperturbative QCD dynamics underlying the structure functions can be explored
in the same framework. Once the nonperturbative multi-parton wave functions are
known from low-energy light-front QCD, a complete description of deep inelastic
structure functions can be realized.Comment: Revtex, 30 pages and no figur
Production of inflammatory mediators by human macrophages obtained from ascites
Ascites is a readily available source of human macrophages (Mø), which can be used to study Mø functions in vitro. We characterized the mediators of inflammation produced by human peritoneal Mø (hp-Mø) obtained from patients with portal hypertension and ascites.
The production of the cytokines interleukin-1β (IL-1β), interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) was found to be lipopolysaccharide (LPS) concentration dependent (0–10 μg/ml) with a maximal production at 10 μg/ml and also dependent on the time of exposure to the stimulus (0–36 h). IL-1β, IL-6 and TNF-α production after LPS administration reached a plateau at 24 h.
In vitro stimulation for 24 h with LPS does not influence the eicosanoid production from endogenous arachidonate. 13 min of exposure of the cells to the calcium ionophore A23187 gives a significant increase in eicosanoid production from both exogenous and endogenous arachidonate. The main eicosanoids produced are the 5-lipoxgenase products LTB4 and 5-hydroxyeicosatetraenoic acid (HETE). The increase in production of the other eicosanoids is not significant. The eicosanoid production depends on the stimulus concentration. The optimal A23187 concentration is 1 μM.
Oxygen radical production was measured in the Mø by a flowcytometric method. The fluorescence intensity of phorbol 12-myristate 13-acetate stimulated and dihydro-rhodamine 123 loaded. hp-Mø increases significantly after 15 min.
We conclude that LPS stimulation of hp-Mø from liver disease results in similar production of IL-1β, IL-6 and TNF-α, but that the profile of the eicosanoid production of these Mø stimulated with LPS and A23187 differs from Mø of other origin and species
Path Integral Variational Methods for Strongly Correlated Systems
We introduce a new approach to highly correlated systems which generalizes
the Fermi Hypernetted Chain and Correlated Basis Function techniques. While the
latter approaches can only be applied to systems for which a nonrelativistic
wave function can be defined, the new approach is based on the variation of a
trial hamiltonian within a path integral framework and thus can also be applied
to relativistic and field theoretical problems. We derive a diagrammatic scheme
for the new approach and show how a particular choice of the trial hamiltonian
corresponds exactly to the use of a Jastrow correlated ansatz for the wave
function in the Fermi Hypernetted Chain approach. We show how our new approach
can be used to find upper bounds to ground state energies in systems which the
FHNC cannot handle, including those described by an energy-dependent effective
hamiltonian. We demonstrate our approach by applying it to a quantum field
theoretical system of interacting pions and nucleons.Comment: 35 RevTeX pages, 7 separated ps figures available on reques
Deep Inelastic Structure Functions in Light-Front QCD: Radiative Corrections
Recently, we have introduced a unified theory to deal with perturbative and
non-perturbative QCD contributions to hadronic structure functions in deep
inelastic scattering. This formulation is realized by combining the coordinate
space approach based on light-front current algebra techniques and the momentum
space approach based on Fock space expansion methods in the Hamiltonian
formalism of light-front field theory. In this work we show how a perturbative
analysis in the light-front Hamiltonian formalism leads to the factorization
scheme we have proposed recently. The analysis also shows that the scaling
violations due to perturbative QCD corrections can be rather easily addressed
in this framework by simply replacing the hadron target by dressed parton
target and then carrying out a systematic expansion in the coupling constant
based on the perturbative QCD expansion of the dressed parton
target. The tools employed for this calculation are those available from
light-front old-fashioned perturbation theory. We present the complete set of
calculations of unpolarized and polarized deep inelastic structure functions to
order . We extract the relevant splitting functions in all the cases.
We explicitly verify all the sum rules to order . We demonstrate the
validity of approximations made in the derivation of the new factorization
scheme. This is achieved with the help of detailed calculations of the
evolution of structure function of a composite system carried out using
multi-parton wavefunctions.Comment: Revtex, 26 pages and no figur
Higher twist and transverse momentum dependent parton distributions: a light-front hamiltonian approach
In order to study twist-3 and transverse momentum dependent parton
distributions, we use light-front time-ordered pQCD at order to
calculate various distribution functions for a dressed quark target. This study
enables us to investigate in detail the existing relations between twist-3 and
transverse momentum dependent parton distributions. Our calculation shows
explicitly that two versions of such relations, considered to be equivalent,
occur in the literature which need to be distinguished. Moreover, we examine
sum rules for higher twist distributions. While the Burkhardt-Cottingham sum
rule for is fulfilled, the corresponding sum rule for is violated.Comment: 10 pages, REVTe
Levels of soluble intercellular adhesion molecule 1, eicosanoids and cytokines in ascites of patients with liver cirrhosis, peritoneal cancer and spontaneous bacterial peritonitis
The levels of the eicosanoids leukotriene B4, prostaglandin E2, prostacycline and thromboxane B2, the cytokines interleukin-1β, interleukin-6 and tumour necrosis factor-α and soluble intercellular adhesion molecule 1 were measured in ascites and plasma samples of patients with liver cirrhosis (53), peritoneal cancer (26) and spontaneous bacterial peritonitis (10) to assess their value as a possible diagnostic and prognostic parameter in the course of the disease. Soluble intercellular adhesion molecule 1, of the eicosanoids prostaglandin E2 and leukotriene B4, and the protein concentration in ascites were all significantly elevated in ascites of patients with peritoneal cancer in comparison to ascites of patients with liver cirrhosis. In ascites of patients with spontaneous bacterial infection interleukin-6 concentration was significantly elevated and the protein concentration was significantly lower in comparison to the other two groups. None of these parameters, however, seems to be of practical use as a diagnostic parameter, as there is an overlap between all the levels of these mediators in ascites of liver cirrhosis, peritoneal cancer and spontaneous bacterial peritonitis group. Soluble intercellular adhesion molecule 1 levels were much higher in plasma than in ascites, in contrast to interleukin-6 levels which were much higher in ascites than in plasma. Soluble intercellular adhesion molecule 1 in ascites correlated with soluble intercellular adhesion molecule 1 in plasma (r = 0.6926, P = 0.0001). Soluble intercellular adhesion molecule 1, interleukin-6 and the number of polymorphonuclear cells in peritoneal fluid correlated during episodes of infection in patients with a peritonitis. For this reason soluble intercellular adhesion molecule 1 and interleukin-6 could be of prognostic value for patients with peritonitis
Detection of Supernova Neutrinos by Neutrino-Proton Elastic Scattering
We propose that neutrino-proton elastic scattering, ,
can be used for the detection of supernova neutrinos in scintillator detectors.
Though the proton recoil kinetic energy spectrum is soft, with , and the scintillation light output from slow, heavily ionizing
protons is quenched, the yield above a realistic threshold is nearly as large
as that from . In addition, the measured proton
spectrum is related to the incident neutrino spectrum, which solves a
long-standing problem of how to separately measure the total energy and
temperature of , , , and .
The ability to detect this signal would give detectors like KamLAND and
Borexino a crucial and unique role in the quest to detect supernova neutrinos.Comment: 10 pages, 9 figures, revtex
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