Remarks on the Coulomb and Covariant Gauges in Finite Temperature QED

We compare the use of the Coulomb gauge in finite temperature QED with a recently proposed prescription for covariant gauges, in which only the transverse photon degrees of freedom are thermalized. Using the Landau rule as a guide, we clarify the relation between the retarded electron self-energy and the elements of the self-energy matrix in the real-time formulation of . The general results are illustrated by means of the one-loop expressions for the electron self-energy in a QED plasma.Comment: LaTeX, 10 pages, no figures; to be published in Phys. Lett.

On neutral pion electroproduction off deuterium

Threshold neutral pion electroproduction on the deuteron is studied in the framework of baryon chiral perturbation theory at next-to-leading order in the chiral expansion. To this order in small momenta, the amplitude is finite and a sum of two- and three-body interactions with no undetermined parameters. We calculate the S-wave multipoles for threshold production and the deuteron S-wave cross section as a function of the photon virtuality. We also discuss the sensitivity to the elementary neutron amplitudes.Comment: 6 pp, revtex, 3 figs, corrected version, to appear in Phys. Rev.

Considerations on rescattering effects for threshold photo- and electro-production of π0\pi^0 on deuteron

We show that for the S-state $\pi^0$-production in processes $\gamma+d\to d+\pi^0$ and $e^-+d\to e^-+d+\pi^0$ the rescattering effects due to the transition: $\gamma+d\to p+p+\pi^-$ (or $n+n+\pi^+)\to d+\pi^0$ are cancelled out due to the Pauli principle. The large values for these effects predicted in the past may result from the fact that the spin structure of the corresponding matrix element and the necessary antisymmetrization induced by the presence of identical protons (or neutrons) in the intermediate state was not taken into account accurately. One of the important consequences of these considerations is that $\pi^0$ photo- and electro-production on deuteron near threshold can bring direct information about elementary neutron amplitudes.Comment: Add a new sectio

Relation between capacities and bimanual performance in hemiplegic cerebral palsied children: Impact os synkinesis

ObjectiveTo analyse the link between unimanual capacities and bimanual performance in cerebral-palsied (CP) hemiplegic children, aged between 5 and 18 years old, studying specifically the impact of synkinesis.Material and methodsSeventy-one CP hemiplegic children (35 boys and 36 girls, mean age 8,5 years; MACS levels from I to III; GMFCS from I to IV) took part in a transversal study, assessed – Melbourne Test (MUUL) for unimanual capacities, and Assisting Hand Assessment (AHA) for bimanual performance – with a specific scale to analyze synkinesis during Box and Block test for affected and healthy hands, collecting synkinesis type, duration and intensity.ResultsThere is a strong correlation between unimanual capacities (MUUL) and bimanual performance (AHA) (r=0.871). Neither age nor gender contribute to bimanual performance (AHA). Multiple linear regression shows that MUUL contributes to bimanual performance variance (AHA) by 70%. Synkinesis partly correlated to capacities (MUUL) and accounts for 10% of the variance of the gap between capacities and bimanual performance.ConclusionA high relationship between unimanual capacities and bimanual performance is confirmed by this study; some authors demonstrated impact of sensory troubles [1], we demonstrate that synkinesis influences the use of unimanual capacities in bimanual performance

Non-Local Charges and their Algebra in Topological Field Theory

With the third order Monge-Amp\`ere equation as an example, we show that there exists an infinite number of nonlocal conserved charges associated with the Witten-Dijkgraaf-Verlinde-Verlinde equations. A general prescription for the construction of these charges is given and the charge algebra is calculated bringing out various other interesting features associated with such systems.Comment: 11 pages, plain Te

Double π0\pi^0 Photoproduction off the Proton at Threshold

The reaction $\gamma p \to \pi^0 \pi^0 p$ has been measured using the TAPS BaF$_2$ calorimeter at the tagged photon facility of the Mainz Microtron accelerator. Chiral perturbation theory (ChPT) predicts that close to threshold this channel is significantly enhanced compared to double pion final states with charged pions. In contrast to other reaction channels, the lower order tree terms are strongly suppressed in 2$\pi^0$ photoproduction. The consequence is the dominance of pion loops in the 2$\pi^0$ channel close to threshold - a result that opens new prospects for the test of ChPT and in particular its inherent loop terms. The present measurement is the first which is sensitive enough for a conclusive comparison with the ChPT calculation and is in agreement with its prediction. The data also show good agreement with a calculation in the unitary chiral approach.Comment: Submitted to PL

A contemporary assessment of land condition in the Northern Gulf region of Queensland

A framework using assessments of soil condition, pasture composition and woodland density was applied to describe 14 grazing land types as being in A (100% of original carrying capacity), B (75%), C (45%) or D (20%) condition. We assessed the condition of 260 sites, principally along public and some station roads, to provide a benchmark for current land condition. Land types were also assigned relative grazing values between 10 (best) and 0, reflecting soil fertility and potential biomass production. The method identifies particular, 'at-risk' land types for priority investment of resources, while the rationale behind assessments might point to management interventions to improve the condition of those land types. Across all land types, 47% of sites were in A condition, 34% in B condition, 17% in C condition and only 2% in D condition. Seventy-five percent of land types with grazing values >5 were in A or B condition, compared with 88% for those with grazing values ?5. For Georgetown granites, only 27% of sites were in A or B condition, with values for other land types being: alluvials 59%, black soils 64% and red duplex soils 57%, suggesting that improving management of these land types is a priority issue. On land types with high grazing value, the major discounting factor was pasture composition (72% of sites discounted), while increasing woodland density was the main discount (73% of sites discounted) on low grazing value land types