Similarity between Positronium-Atom and Electron-Atom Scattering

We employ the impulse approximation for a description of positronium-atom scattering. Our analysis and calculations of Ps-Kr and Ps-Ar collisions provide a theoretical explanation of the similarity between the cross sections for positronium scattering and electron scattering for a range of atomic and molecular targets observed by S. J. Brawley et al. [Science 330, 789 (2010)].

Fluxes of organic contaminants from the river catchment into, through and out of the Humber Estuary, UK

This paper summarises the work done on the distribution and reactivity of organic contaminants (simazine, atrazine, lindane, fluoranthene, pyrene, PCB 77, PCB 118) in the Humber Estuary and associated major rivers, as part of the LOIS programme. The preliminary flux calculations show that the most important contributors of selected organic contaminants were the rivers Trent (45% of simazine, 20% of atrazine), Aire (30% of simazine and 33% of atrazine), Don (36 and 37% of fluoranthene and pyrene) and Ouse (18% of fluoranthene and pyrene). For lindane and PCBs, the Aire and Ouse were the key sources. The water flow in all the rivers shows strong seasonal variations, as do the contaminant concentrations. As a result, the mean daily fluxes of these contaminants displayed a strong seasonality. Annual mean concentrations of simazine and atrazine decreased by more than 50% over the period 1994-1995 in most of the rivers, probably as a result of their restricted use in the UK. Mass balance calculations show that the Humber is a sink for atrazine, lindane, PCB 77 and PCB 118, although the degree of removal is generally much lower for atrazine and lindane than for PCB 77 and PCB 118. Mass balance results also show that the Humber can either be a source of fluoranthene and pyrene (in the suspended particulate phase), or a sink (in the dissolved phase), although overall the Humber acts as sink. The budget exercise represents an attempt to quantify the input and output of selected organic contaminants from catchment to ocean. However, due to limited data and assumptions involved in calculations, the estimates should be considered as an order of magnitude approximation. Further improvement both in resolution and accuracy is required.

Reliability of reports of childhood trauma in bipolar disorder: A test–retest study over 18 months

This study aimed to explore the reliability of self-reported trauma histories in a population with a diagnosis of Bipolar Disorder using the Childhood Trauma Questionnaire. Previous studies in other populations suggest high reliability of trauma histories over time and it was postulated that a similar high reliability would be demonstrated in this population. Thirty-nine patients with a confirmed diagnosis (DSM-IV criteria) were followed-up and re-administered the Childhood Trauma Questionnaire after 18 months. Cohen's kappa scores and intraclass correlations suggest reasonable test-retest reliability over the 18-month time period of the study for all types of childhood abuse, namely emotional, physical, sexual, and physical abuse and emotional neglect. Intraclass correlations ranged from r = .50 to (sexual abuse) to r = .96 (physical abuse). Cohen's kappas ranged from .44 (sexual abuse) to .76 (physical abuse). Retrospective reports of childhood trauma can be seen as reliable and are in keeping with results found with other mental health populations.

Photoionization cross sections for the trans-iron element Se + from 18 to 31 eV

Absolute photoionization cross-section calculations are presented for Se + using large-scale close-coupling calculations within the Breit--Pauli and Dirac--Coulomb R -matrix approximations. The results from our theoretical work are compared with recent measurements (Esteves 2010 PhD Thesis publication number AAI3404727, University of Reno, NV, USA; Sterling et al 2011 J. Phys. B: At. Mol. Opt. Phys. 44 025701; Esteves et al 2011 Phys. Rev. A 84 013406) made at the advanced light source (ALS) radiation facility in Berkeley, CA, USA. We report on results for the photon energy range 18.0--31.0 eV, which spans the ionization thresholds of the 4 S o 3/2 ground state and the low-lying 2 D o 5/2,3/2 and 2 P o 3/2,1/2 metastable states. Metastable fractions are inferred from our present work. Resonance energies and quantum defects of the prominent Rydberg resonances series identified in the spectra are compared for the 4p → n d transitions with the recent ALS experimental measurements made on this complex trans-iron element.

Experimental and theoretical photoionization cross sections for Se + from 18 eV to 31 eV

Absolute Se photoionization cross-section measurements and Dirac-Coulomb R -matrix calculations are reported for the photon energy range 18.0 eV – 31.0 eV, which spans the ionization thresholds of the 4 S 0 3/2 ground state and the low-lying 2 D 0 3/2,5/2 and 2 P 0 1/2,3/2 metastable states. The determination of the photoionization and recombination properties of n -capture element ions is motivated by their astrophysical detection and the importance of their elemental abundances in testing theories of nucleosynthesis and stellar structure.