The field theoretic derivation of the contact value theorem in planar geometries and its modification by the Casimir effect

The contact value theorem for Coulomb gases in planar or film-like geometries is derived using a Hamiltonian field theoretic representation of the system. The case where the film is enclosed by a material of different dielectric constant to that of the film is shown to contain an additional Casimir-like term which is generated by fluctuations of the electric potential about its mean-field value.Comment: Link between Sine-Gordon and Coulomb gas pressures via subtraction of self interaction terms included. Discussion of results within Debye-Huckel approximation included. Added reference

Plant invasions in South Africa: Insights from the 2017 National Status Report on Biological Invasions

The impacts of biological invasions are increasing and are felt by all sectors of society. The Department of Environmental Affairs currently invests over R1.5 billion a year on managing biological invasions, mostly on alien plant control. In this talk we discuss the key findings of the first National Status Report on Biological Invasions in South Africa (produced October 2017). In contrast to many other countries, the most diverse, widespread, and damaging invaders in South Africa are plants. They are the third-largest threat to South Africa’s terrestrial biodiversity; invasive trees and shrubs reduce surface water resources by between 3 and 5%; and they have reduced the capacity of natural rangelands to support livestock production by over 100 000 large livestock units. The size of the problem is increasing. While the risk from legally introduced alien species is being addressed, the risk due to accidental introductions is probably increasing. Data from the Southern African Plant Invaders Atlas (SAPIA) show that over the past decade, an average of ten plant species per year have naturalised, and even the most widespread invaders are still spreading. In short, South Africa has a major plant invasion debt. More taxa should be listed under national regulations, but ultimately more needs to be done to ensure that management is strategic and effective. One of the main success stories, however, is biological control. The technology has led to significant and on-going economic returns. If we are to improve policy and management decisions we need more systematic estimates of the area and abundance of plant invasions; more studies documenting the ecological and socio-economic impacts of plant invasions; better planning, including the setting of goals; and better monitoring of the effectiveness of current control operations. We welcome ideas, in particular for how SAPIA should develop in future

Erratum to: Search for diboson resonances in hadronic final states in 139 fb−1 of pp collisions at s√ = 13 TeV with the ATLAS detector

A mistake was identified for the paper [1] in the treatment of the radion [2] cross-sections, which resulted in multiple changes.(undefined)info:eu-repo/semantics/publishedVersio

Determination of the Deep Inelastic Contribution to the Generalised Gerasimov-Drell-Hearn Integral for the Proton and Neutron

The virtual photon absorption cross section differences [sigma_1/2-sigma_3/2] for the proton and neutron have been determined from measurements of polarised cross section asymmetries in deep inelastic scattering of 27.5 GeV longitudinally polarised positrons from polarised 1H and 3He internal gas targets. The data were collected in the region above the nucleon resonances in the kinematic range nu < 23.5 GeV and 0.8 GeV**2 < Q**2 < 12 GeV**2. For the proton the contribution to the generalised Gerasimov-Drell-Hearn integral was found to be substantial and must be included for an accurate determination of the full integral. Furthermore the data are consistent with a QCD next-to-leading order fit based on previous deep inelastic scattering data. Therefore higher twist effects do not appear significant.Comment: 6 pages, 3 figures, 1 table, revte

Observation of a Coherence Length Effect in Exclusive Rho^0 Electroproduction

Exclusive incoherent electroproduction of the rho^0(770) meson from 1H, 2H, 3He, and 14N targets has been studied by the HERMES experiment at squared four-momentum transfer Q**2>0.4 GeV**2 and positron energy loss nu from 9 to 20 GeV. The ratio of the 14N to 1H cross sections per nucleon, known as the nuclear transparency, was found to decrease with increasing coherence length of quark-antiquark fluctuations of the virtual photon. The data provide clear evidence of the interaction of the quark- antiquark fluctuations with the nuclear medium.Comment: RevTeX, 5 pages, 3 figure

Measurement of the Neutron Spin Structure Function g1ng_1^n with a Polarized ^3He Target

Results are reported from the HERMES experiment at HERA on a measurement of the neutron spin structure function $g_1^n(x,Q^2)$ in deep inelastic scattering using 27.5 GeV longitudinally polarized positrons incident on a polarized $^3$He internal gas target. The data cover the kinematic range $0.023<x<0.6$ and $1 (GeV/c)^2 < Q^2 <15 (GeV/c)^2$. The integral $\int_{0.023}^{0.6} g_1^n(x) dx$ evaluated at a fixed $Q^2$ of $2.5 (GeV/c)^2$ is $-0.034\pm 0.013(stat.)\pm 0.005(syst.)$. Assuming Regge behavior at low $x$, the first moment $\Gamma_1^n=\int_0^1 g_1^n(x) dx$ is $-0.037\pm 0.013(stat.)\pm 0.005(syst.)\pm 0.006(extrapol.)$.Comment: 4 pages TEX, text available at http://www.krl.caltech.edu/preprints/OAP.htm