Analysis of full-QCD and quenched-QCD lattice propagators

Recent lattice-QCD results for the dressed-gluon propagator are used within the quark Dyson-Schwinger equation to determine the gluon-quark vertex dressing necessary to reproduce the lattice-QCD results for the dressed-quark propagator. Both quenched and full QCD lattice simulations, for a range of low quark current masses, are analyzed. The chiral extrapolation is made through this continuum DSE form. Resulting chiral and physical pion observables are investigated.Comment: Talk given at PANIC 2005 Conference, Santa Fe, October 2005. To be published in the Proceeding

Vector meson form factors and their quark-mass dependence

The electromagnetic form factors of vector mesons are calculated in an explicitly Poincar\'e covariant formulation, based on the Dyson--Schwinger equations of QCD, that respects electromagnetic current conservation, and unambiguously incorporates effects from vector meson poles in the quark-photon vertex. This method incorporates a 2-parameter effective interaction, where the parameters are constrained by the experimental values of chiral condensate and $f_{\pi}$. This approach has successfully described a large amount of light-quark meson experimental data, e.g. ground state pseudoscalar masses and their electromagnetic form factors; ground state vector meson masses and strong and electroweak decays. Here we apply it to predict the electromagnetic properties of vector mesons. The results for the static properties of the $\rho$-meson are: charge radius $= 0.54 {\rm fm}^2$, magnetic moment $\mu = 2.01$, and quadrupole moment ${\cal Q} = -0.41$. We investigate the quark mass dependence of these static properties and find that our results at the charm quark mass are in agreement with recent lattice simulations. The charge radius decreases with increasing quark mass, but the magnetic moment is almost independent of the quark mass.Comment: 13 pages, 7 figure

The role of markets in food availability and market integration among smallholder farmers: the case of Western Kenya [Poster]

Poster presented at Tropentag 2013. International Research on Food Security, Natural Resource Management and Rural Development. "Agricultural development within the rural-urban continuum". Stuttgart-Hohenheim (Germany), Sep 17-19 2013

Crop species diversity in smallholder farms in Western Kenya and their contribution to food security

Poster presented at First International Conference on Global Food Security. Noordwijkerhout (The Netherlands), 29 Sep - 02 Oct 2013

Quark-gluon vertex model and lattice-QCD data

A model for the dressed quark-gluon vertex, at zero gluon momentum, is formed from a nonperturbative extension of the two Feynman diagrams that contribute at 1-loop in perturbation theory. The required input is an existing ladder-rainbow model Bethe-Salpeter kernel from an approach based on the Dyson-Schwinger equations; no new parameters are introduced. The model includes an Ansatz for the triple-gluon vertex. Two of the three vertex amplitudes from the model provide a point-wise description of the recent quenched lattice-QCD data. An estimate of the effects of quenching is made.Comment: 4 pages, 3 figure

EVALUATION OF PHYTOCHEMICALS, ANTIOXIDANT CAPACITY AND ANTIBACTERIAL ACTION OF THE FRUIT OF THESPESIA POPULNEA (L.) SOL. EX. CORREA

Objectives: To carry out proximate analysis, detect phytochemicals, determine antioxidant activity, total polyphenolic content (TPC) and antimicrobial efficacy of the methanolic extract of the fruit of Thespesia populnea (T. populnea) and further carry out Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) tests for susceptible microorganisms.Methods: The following methods were used: Folin Ciocalteau method for TPC, DPPH radical scavenging assay for in vitro antioxidant activity, agar well diffusion for antimicrobial activity and broth dilution for MIC followed by MBC.Results: The following results were obtained: TPC of 78.12±6.46 mg/g GAE; IC50 value of the radical scavenging activity: 16.29 µg/ml; antibacterial activity-cold extract: excellent to moderate against Staphylococcus aureus, Streptococcus pyogenes and Pasteurella multocida, low to no effect against Escherichia coli, Candida albicans, Pseudomonas aeruginosa and Klebsiella pneumoniae; hot extract: excellent to moderate against S. aureus, P. multocida and E. coli; relatively low to no effect on S. pyogenes, Candida albicans, Pseudomonas aeruginosa and Klebsiella pneumoniae.MIC as well as MBC of the hot methanolic extracts of T. populnea were found to be between 0.1-2.5 mg/ml against S. aureus, E. coli and P. multocida whereas those of the cold extract against the same organisms was between 0.005-1.0 mg/ml.Conclusion: The methanolic extract of Thespesia populnea fruit showed excellent antimicrobial activity against some dreaded pathogens besides being an antioxidant in nature. These properties of the fruit can help protect injured and/or infected tissues and hence be used to develop a novel medicinal agent.Â

Stimulation of macromolecular synthesis by ascorbate in Neurospora

Stimulation of macromolecular synthesis by ascorbat

Current quark mass dependence of nucleon magnetic moments and radii

A calculation of the current-quark-mass-dependence of nucleon static electromagnetic properties is necessary in order to use observational data as a means to place constraints on the variation of Nature's fundamental parameters. A Poincare' covariant Faddeev equation, which describes baryons as composites of confined-quarks and -nonpointlike-diquarks, is used to calculate this dependence The results indicate that, like observables dependent on the nucleons' magnetic moments, quantities sensitive to their magnetic and charge radii, such as the energy levels and transition frequencies in Hydrogen and Deuterium, might also provide a tool with which to place limits on the allowed variation in Nature's constants.Comment: 23 pages, 2 figures, 4 tables, 4 appendice

Survey of nucleon electromagnetic form factors

A dressed-quark core contribution to nucleon electromagnetic form factors is calculated. It is defined by the solution of a Poincare' covariant Faddeev equation in which dressed-quarks provide the elementary degree of freedom and correlations between them are expressed via diquarks. The nucleon-photon vertex involves a single parameter; i.e., a diquark charge radius. It is argued to be commensurate with the pion's charge radius. A comprehensive analysis and explanation of the form factors is built upon this foundation. A particular feature of the study is a separation of form factor contributions into those from different diagram types and correlation sectors, and subsequently a flavour separation for each of these. Amongst the extensive body of results that one could highlight are: r_1^{n,u}>r_1^{n,d}, owing to the presence of axial-vector quark-quark correlations; and for both the neutron and proton the ratio of Sachs electric and magnetic form factors possesses a zero.Comment: 43 pages, 17 figures, 12 tables, 5 appendice