Baryon Magnetic Moments in the 1/N_c Expansion with Flavor Symmetry Breaking

The magnetic moments and transition magnetic moments of the ground state baryons are analyzed in an expansion in 1/N_c, SU(3) flavor symmetry breaking and isospin symmetry breaking. There is clear evidence in the experimental data for the hierarchy of magnetic moments of the combined expansion in 1/N_c and flavor breaking. SU(3) breaking in the magnetic moments is expected to be enhanced relative to that of other hadronic observables, and significant SU(3) breaking is found.Comment: 21 pages, 1 figure, CLAS reference update

The Kinetics of the Exchange of Tritium between Hypophosphorous Acid and Water

We have measured the rates of exchange of radioactive hydrogen (tritium) between tritiated water, HTO, and the thwo "undissociable" hydrogens of monobasic hydrophosphorous acid, H3PO2

Past plant use in Jordan as revealed by archaeological and ethnoarchaeological phytolith signatures

Ninety-six phytolith samples were analysed from seven archaeological sites ranging from the Pre-Pottery Neolithic to the Classical period and from two ethnoarchaeological sites in Jordan. The aims were to test the possibility of detecting past irrigation with the methodology outlined by Madella et al. (2009) and Jenkins et al. (Chapter 21, this volume) and to study the contextual and temporal variation of plant use in Jordan. We utilised a water availability index using the proportion of phytolith types and ordination statistical methods to explore the similarities between the phytolith assemblages. The result of applying the irrigation methodology was promising, with contexts from water channels showing the greatest indication of water availability. Changes in plant use through time were also apparent with regard to phytolith densities and taxonomy. Date palm was identified in the Pottery Neolithic, providing one of the earliest records for this taxon in Jordan. This study shows the potential of both the water availability index and the value of inter-site comparison of phytolith assemblages

An asymptotic sampling formula for the coalescent with Recombination

Ewens sampling formula (ESF) is a one-parameter family of probability distributions with a number of intriguing combinatorial connections. This elegant closed-form formula first arose in biology as the stationary probability distribution of a sample configuration at one locus under the infinite-alleles model of mutation. Since its discovery in the early 1970s, the ESF has been used in various biological applications, and has sparked several interesting mathematical generalizations. In the population genetics community, extending the underlying random-mating model to include recombination has received much attention in the past, but no general closed-form sampling formula is currently known even for the simplest extension, that is, a model with two loci. In this paper, we show that it is possible to obtain useful closed-form results in the case the population-scaled recombination rate $\rho$ is large but not necessarily infinite. Specifically, we consider an asymptotic expansion of the two-locus sampling formula in inverse powers of $\rho$ and obtain closed-form expressions for the first few terms in the expansion. Our asymptotic sampling formula applies to arbitrary sample sizes and configurations.Comment: Published in at http://dx.doi.org/10.1214/09-AAP646 the Annals of Applied Probability (http://www.imstat.org/aap/) by the Institute of Mathematical Statistics (http://www.imstat.org

Inactivation of the antibacterial and cytotoxic properties of silver ions by biologically relevant compounds

There has been a recent surge in the use of silver as an antimicrobial agent in a wide range of domestic and clinical products, intended to prevent or treat bacterial infections and reduce bacterial colonization of surfaces. It has been reported that the antibacterial and cytotoxic properties of silver are affected by the assay conditions, particularly the type of growth media used in vitro. The toxicity of Ag+ to bacterial cells is comparable to that of human cells. We demonstrate that biologically relevant compounds such as glutathione, cysteine and human blood components significantly reduce the toxicity of silver ions to clinically relevant pathogenic bacteria and primary human dermal fibroblasts (skin cells). Bacteria are able to grow normally in the presence of silver nitrate at >20-fold the minimum inhibitory concentration (MIC) if Ag+ and thiols are added in a 1:1 ratio because the reaction of Ag+ with extracellular thiols prevents silver ions from interacting with cells. Extracellular thiols and human serum also significantly reduce the antimicrobial activity of silver wound dressings Aquacel-Ag (Convatec) and Acticoat (Smith & Nephew) to Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli in vitro. These results have important implications for the deployment of silver as an antimicrobial agent in environments exposed to biological tissue or secretions. Significant amounts of money and effort have been directed at the development of silver-coated medical devices (e.g. dressings, catheters, implants). We believe our findings are essential for the effective design and testing of antimicrobial silver coatings

Hilbert Series for Flavor Invariants of the Standard Model

The Hilbert series is computed for the lepton flavor invariants of the Standard Model with three generations including the right-handed neutrino sector needed to generate light neutrino masses via the see-saw mechanism. We also compute the Hilbert series of the quark flavor invariants for the case of four generations.Comment: 6 page

Bosonic Operator Methods for the Quark Model

Quark model matrix elements can be computed using bosonic operators and the holomorphic representation for the harmonic oscillator. The technique is illustrated for normal and exotic baryons for an arbitrary number of colors. The computations are much simpler than those using conventional quark model wavefunctions