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

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

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 $\alpha_s$ 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 $g_2$ is fulfilled, the corresponding sum rule for $h_2$ is violated.Comment: 10 pages, REVTe

Dynamical mean-field theory of spiking neuron ensembles: response to a single spike with independent noises

Dynamics of an ensemble of $N$-unit FitzHugh-Nagumo (FN) neurons subject to white noises has been studied by using a semi-analytical dynamical mean-field (DMF) theory in which the original $2 N$-dimensional {\it stochastic} differential equations are replaced by 8-dimensional {\it deterministic} differential equations expressed in terms of moments of local and global variables. Our DMF theory, which assumes weak noises and the Gaussian distribution of state variables, goes beyond weak couplings among constituent neurons. By using the expression for the firing probability due to an applied single spike, we have discussed effects of noises, synaptic couplings and the size of the ensemble on the spike timing precision, which is shown to be improved by increasing the size of the neuron ensemble, even when there are no couplings among neurons. When the coupling is introduced, neurons in ensembles respond to an input spike with a partial synchronization. DMF theory is extended to a large cluster which can be divided into multiple sub-clusters according to their functions. A model calculation has shown that when the noise intensity is moderate, the spike propagation with a fairly precise timing is possible among noisy sub-clusters with feed-forward couplings, as in the synfire chain. Results calculated by our DMF theory are nicely compared to those obtained by direct simulations. A comparison of DMF theory with the conventional moment method is also discussed.Comment: 29 pages, 2 figures; augmented the text and added Appendice

Primordialists and Constructionists: a typology of theories of religion

This article adopts categories from nationalism theory to classify theories of religion. Primordialist explanations are grounded in evolutionary psychology and emphasize the innate human demand for religion. Primordialists predict that religion does not decline in the modern era but will endure in perpetuity. Constructionist theories argue that religious demand is a human construct. Modernity initially energizes religion, but subsequently undermines it. Unpacking these ideal types is necessary in order to describe actual theorists of religion. Three distinctions within primordialism and constructionism are relevant. Namely those distinguishing: a) materialist from symbolist forms of constructionism; b) theories of origins from those pertaining to the reproduction of religion; and c) within reproduction, between theories of religious persistence and secularization. This typology helps to make sense of theories of religion by classifying them on the basis of their causal mechanisms, chronology and effects. In so doing, it opens up new sightlines for theory and research

Eureka and beyond: mining's impact on African urbanisation

This collection brings separate literatures on mining and urbanisation together at a time when both artisanal and large-scale mining are expanding in many African economies. While much has been written about contestation over land and mineral rights, the impact of mining on settlement, notably its catalytic and fluctuating effects on migration and urban growth, has been largely ignored. African nation-states’ urbanisation trends have shown considerable variation over the past half century. The current surge in ‘new’ mining countries and the slow-down in ‘old’ mining countries are generating some remarkable settlement patterns and welfare outcomes. Presently, the African continent is a laboratory of national mining experiences. This special issue on African mining and urbanisation encompasses a wide cross-section of country case studies: beginning with the historical experiences of mining in Southern Africa (South Africa, Zambia, Zimbabwe), followed by more recent mineralizing trends in comparatively new mineral-producing countries (Tanzania) and an established West African gold producer (Ghana), before turning to the influence of conflict minerals (Angola, the Democratic Republic of Congo and Sierra Leone)