Correlations of center flux in SU(2) Yang-Mills theory

By using the method of center projection the center vortex part of the gauge field is isolated and its propagator is evaluated in the center Landau gauge, which minimizes the open 3-dimensional Dirac volumes of non-trivial center links bounded by the closed 2-dimensional center vortex surfaces. The center field propagator is found to dominate the gluon propagator (in Landau gauge) in the low momentum regime and to give rise to an OPE correction to the latter of $\sqrt{\sigma} /p^3$.The screening mass of the center vortex field vanishes above the critical temperature of the deconfinement phase transition, which naturally explains the second order nature of this transition consistently with the vortex picture. Finally, the ghost propagator of maximal center gauge is found to be infrared finite and thus shows no signal of confinement.Comment: Presented at 23rd International Symposium on Lattice Field Field: Lattice 2005, Trinity College, Dublin, Ireland, 25-30 Jul 200

Ionization by bulk heating of electrons in capacitive radio frequency atmospheric pressure microplasmas

Electron heating and ionization dynamics in capacitively coupled radio frequency (RF) atmospheric pressure microplasmas operated in helium are investigated by Particle in Cell simulations and semi-analytical modeling. A strong heating of electrons and ionization in the plasma bulk due to high bulk electric fields are observed at distinct times within the RF period. Based on the model the electric field is identified to be a drift field caused by a low electrical conductivity due to the high electron-neutral collision frequency at atmospheric pressure. Thus, the ionization is mainly caused by ohmic heating in this "Omega-mode". The phase of strongest bulk electric field and ionization is affected by the driving voltage amplitude. At high amplitudes, the plasma density is high, so that the sheath impedance is comparable to the bulk resistance. Thus, voltage and current are about 45{\deg} out of phase and maximum ionization is observed during sheath expansion with local maxima at the sheath edges. At low driving voltages, the plasma density is low and the discharge becomes more resistive resulting in a smaller phase shift of about 4{\deg}. Thus, maximum ionization occurs later within the RF period with a maximum in the discharge center. Significant analogies to electronegative low pressure macroscopic discharges operated in the Drift-Ambipolar mode are found, where similar mechanisms induced by a high electronegativity instead of a high collision frequency have been identified

Habitat width along a latitudinal gradient

We use the Chowdhury ecosystem model, one of the most complex agent-based ecological models, to test the latitude-niche breadth hypothesis, with regard to habitat width, i.e., whether tropical species generally have narrower habitats than high latitude ones. Application of the model has given realistic results in previous studies on latitudinal gradients in species diversity and Rapoport's rule. Here we show that tropical species with sufficient vagility and time to spread into adjacent habitats, tend to have wider habitats than high latitude ones, contradicting the latitude-niche breadth hypothesis.Comment: 13 pages including all figures, draft for a biology journa

Introduction to the special issue: multiple jobholding in Europe

In a number of European countries there is a clear trend towards increased multiple jobholding. As things stand, however, little is known about the structure and the potential consequences of this increase, notably in terms of quality of work and social protection. This special issue focuses on contemporary forms of multiple jobholding in Europe. Have the structure, nature and dynamics of multiple jobholding changed over time? What are the roles of labour market flexibility, technological change and work fragmentation in the development of multiple jobholding? And do multiple jobholders benefit from similar and adequate employment terms, conditions and protections compared with single jobholders, or are they worse off as a consequence of their (fragmented) employment situation? What implications do these findings have for unions, policy-makers and the regulation of work? The collection of articles in this special issue adds to the literature on emerging forms of employment in the digital age and challenges for social protection, also in light of the COVID-19 pandemic. This introduction initiates a discussion of central debates on multiple jobholding and presents a synopsis of the articles in this issue

Effects of the Zanzibar School-Based Deworming Program on Iron Status of Children.

We evaluated the effects of the Zanzibar school-based deworming program on the iron status of primary school children. Parasitologic and nutritional assessments were carried out at baseline, 6 mo, and 12 mo in 4 nonprogram schools (n = 1002), 4 schools in which students received twice-yearly deworming (n = 952), and 4 schools in which students received thrice-yearly deworming (n = 970) with 500 mg generic mebendazole. Schools were randomly selected for evaluation and allocated to program groups. Relative to no treatment, thrice-yearly deworming caused significant decreases in protoporphyrin concentrations and both deworming regimens caused marginally significant increases in serum ferritin concentrations. The average annual changes in protoporphyrin concentrations were -5.9 and -23.5 micromol/mol heme in the control and thrice-yearly deworming groups, respectively (P < 0.001). The average changes in ferritin concentration were 2.8 and 4.5 microg/L, respectively (P = 0.07). Deworming had no effect on annual hemoglobin change or prevalence of anemia. However, the relative risk of severe anemia (hemoglobin < 70 g/L) was 0.77 (95% confidence limits: 0.39, 1.51) in the twice-yearly deworming group and 0.45 (0.19, 1.08) in the thrice-yearly deworming group. The effects on prevalence of high protoporphyrin values and incidence of moderate-to-severe anemia (hemoglobin < 90 g/L) were significantly greater in children with > 2000 hookworm eggs/g feces at baseline. We estimate that this deworming program prevented 1260 cases of moderate-to-severe anemia and 276 cases of severe anemia in a population of 30,000 schoolchildren in 1 y. Where hookworm is heavily endemic, deworming programs can improve iron status and prevent moderate and severe anemia, but deworming may be needed at least twice yearly