Three-dimensional quasi-Tonks gas in a harmonic trap

We analyze the macroscopic dynamics of a Bose gas in a harmonic trap with a superimposed two-dimensional optical lattice, assuming a weak coupling between different lattice sites. We consider the situation in which the local chemical potential at each lattice site can be considered as that provided by the Lieb-Liniger solution. Due to the weak coupling between sites and the form of the chemical potential, the three-dimensional ground-state density profile and the excitation spectrum acquire remarkable properties different from both 1D and 3D gases. We call this system a quasi-Tonks gas. We discuss the range of applicability of this regime, as well as realistic experimental situations where it can be observed.Comment: 4 pages, 3 figures, misprints correcte

The incidence of fragility hip fractures in a subpopulation of South Africa

Background. Fragility hip fractures (FHFs) are associated with significant morbidity, mortality and burden on the healthcare system. European and North American literature suggests that the worldwide incidence of FHFs is increasing, but very little is known about the incidence of FHFs in Africa and South Africa (SA). Historically FHFs were believed to be uncommon in black African populations, but recent studies have shown a marked increase in the incidence compared with the early literature. Objectives. To investigate the age-, gender-and population group-specific incidences of FHFs in a subpopulation in Eastern Cape Province, SA. Methods. A retrospective review of all patients presenting with FHFs was performed at a tertiary hospital in the Eastern Cape over a 1-year period. Age-, gender-and population group-specific incidence rates were calculated for 5-year age intervals using the age distribution data of the western region of the Eastern Cape (WREC) as a denominator for each age group. Overall crude incidence rates were calculated by using the sum total of FHFs, divided by the study population. All incidences were calculated as number of fractures per 100 000 people annually. Results. A total of 253 patients with FHFs were included. The crude incidence rate of low-energy hip fractures in the WREC was 19.3 per 100 000 (males 14.6, females 23.4) over the study period. Population group-specific incidences were 15.1, 18.7, 19.9 and 46.6 per 100 000 for black, coloured, Indian and white population groups, respectively. The highest number of low-energy hip fractures in females occurred in the ≥85-year (19.6%) and 70 -74-year (16.5%) age groups, with the highest number of male cases observed in the 60 -64-year group (20.2%). The highest frequency distribution of FHFs was observed in black males aged 60 -64 years (5.5%; n=14) and black females aged 70 -74 years (6.3%; n=16). Conclusions. The local incidence of FHFs is higher than initially reported, but when compared with other countries remains on the lower end of spectrum. A large proportion of FHFs are occurring in young patients (<65 years). These findings warrant further investigation that may prompt the development of preventive strategies and optimal treatment programmes

Numerical Investigation of Light Scattering off Split-Ring Resonators

Recently, split ring-resonators (SRR's) have been realized experimentally in the near infrared (NIR) and optical regime. In this contribution we numerically investigate light propagation through an array of metallic SRR's in the NIR and optical regime and compare our results to experimental results. We find numerical solutions to the time-harmonic Maxwell's equations by using advanced finite-element-methods (FEM). The geometry of the problem is discretized with unstructured tetrahedral meshes. Higher order, vectorial elements (edge elements) are used as ansatz functions. Transparent boundary conditions and periodic boundary conditions are implemented, which allow to treat light scattering problems off periodic structures. This simulation tool enables us to obtain transmission and reflection spectra of plane waves which are incident onto the SRR array under arbitrary angles of incidence, with arbitrary polarization, and with arbitrary wavelength-dependencies of the permittivity tensor. We compare the computed spectra to experimental results and investigate resonances of the system.Comment: 9 pages, 8 figures (see original publication for images with a better resolution

Mutual Event Observations of Io's Sodium Corona

We have measured the column density profile of Io's sodium corona using 10 mutual eclipses between the Galilean satellites. This approach circumvents the problem of spatially resolving Io's corona directly from Io's bright continuum in the presence of atmospheric seeing and telescopic scattering. The primary goal is to investigate the spatial and temporal variations of Io's corona. Spectra from the Keck Observatory and McDonald Observatory from 1997 reveal a corona that is only approximately spherically symmetric around Io. Comparing the globally averaged radial sodium column density profile in the corona with profiles measured in 1991 and 1985, we find that there has been no significant variation. However, there appears to be a previously undetected asymmetry: the corona above Io's sub-Jupiter hemisphere is consistently more dense than above the anti-Jupiter hemisphere

Quantifying the value of problem structuring interventions?

We review the current work on measuring and evaluating PSM interventions and return to the paradox of trying to determine a specific monetary value. In an attempt to resolve the paradox, we have borrowed freely from economic theory and constructed a scenario where the question of value can be investigated through the effect that a problem structuring intervention will have on information asymmetry in contract formation. This suggests an avenue of research where the value of problem structuring interventions can be investigated empirically. We discuss the difficulties of research design to investigate this question but also the potential benefits.European Commissio