Ab initio study of the elastic behavior of MgSiO3 ilmenite at high pressure

We investigate the athermal high pressure behavior of the elastic properties of MgSiO3 ilmenite up to 30 GPa using the ab initio pseudopotential method. Our results at zero pressure are in good agreement with single-crystal elasticity measurements. The elastic anisotropy is shown to decrease slightly under compression and hence to remain substantial (25 to 20% shear wave anisotropy and 16 to 10% longitudinal wave anisotropy) over the pressure regime studied. The directions of fastest and slowest wave propagation are found to change slightly with pressure as determined by the pressure dependence of c(14) and c(25). Comparisons with the elastic behavior of other deep transition zone phases such as ringwoodite and garnet show that ilmenite is likely to be the fastest and most anisotropic mineral in this region. Large contrasts (approximate to 10%) in velocities and densities between ilmenite and garnet are suggested to be significant for the interpretation of lateral structure in the transition zone

Erratum to: Emergence of novel phenomena on the border of low dimensional spin and charge order (The European Physical Journal B, (2018), 91, 9, (196), 10.1140/epjb/e2018-90358-3)

AbstractProximity to magnetic order as well as low dimensionality are both beneficial to superconductivity at elevated temperatures. Materials on the border of magnetism display a wide range of novel and potentially useful phenomena: highTcs, heavy fermions, coexistence of magnetism and superconductivity and giant magnetoresistance. Low dimensionality is linked to enhanced fluctuations and, in the case of heavy fermions, has been experimentally shown to be beneficial for the fluctuations that are responsible for the rich abundance of novel emergent phases. This experimental strategy motivated us to explore 2D insulating magnets with a view to investigate phase evolution across metal-insulator and magnetic-non-magnetic boundaries. This has been a fruitful venture with totally novel results different to our expectations. We present results from 2 distinct systems. The MPS3family are highly anisotropic in both their crystal and magnetic structures. FePS3in particular is a model insulating honeycomb antiferromagnet. We find that the application of pressure to FePS3induces an insulator to metal transition. The second system, Cs2CuCl4, is a highly-frustrated quantum spin liquid at low temperature. The competition of the 3 relevant exchange couplings is delicately balanced. It has been shown to become antiferromagnetic at very low temperatures (~1 K). We have found that the application of pressure for 3 days or more followed by a return to ambient pressure stabilises a totally distinct magnetic ground state.</jats:p

An ethnographic study of the everyday lives of young women living with HIV in Zambia

Although young women in sub-Saharan Africa are disproportionately affected by HIV, limited research has documented their lives with HIV. This thesis aimed to understand the impact of HIV on young women’s everyday lives in Lusaka, Zambia. I conducted a 12-month ethnography with seven middle-income young women living with HIV in 2017-18. Participant observation with the young women, their friends and families was conducted in their homes, recreational spaces, churches, health facilities, colleges and workplaces. Additional data were generated through participatory workshops, diaries and visual collages. The young women had previously participated in a qualitative study in 2014- 15. Data from the latter study were included for secondary analysis. Analyses were inductive, theory-driven and iterative. Methodological critique assessed how collage methods effectively enabled self-reflection among participants in their representations of their lives with HIV. This thesis also prompted critical reflections on ethics-in-practice in conducting research with these participants, and identified areas of ethical tension, including the negotiated researcher-participant relationship and protecting participants’ HIV status. Theoretical findings showed how young women enacted agency through employing strategies to navigate their lives, including secrecy and limiting disclosure. This enabled them to cope with a stigmatising environment and the tight restrictions that were sometimes imposed around disclosure, sexual relationships and treatment adherence. Temporal analyses explored the impact of HIV on the participants’ lives across time, showing how their everyday and biographical experiences were interlinked with the historical availability of ART. My findings provide evidence of these young women’s resilience, offsetting a historical focus on their vulnerability. I propose applying Reynolds Whytes’ term “biogeneration” to capture how young people’s lives are entwined lives to their biosocial-historical environment. I question overly-simplistic narratives urging routine HIV-status disclosure, and endorse support groups for young people living with HIV to provide critical safe spaces to share their experiences with their peers

The North East Italy (NI) broadband seismic network run by OGS: experience in improving the long period performances

The NI broadband seismic network is designed to monitor regional seismic activity of North East Italy and surroundings as well as to provide high quality data for various research projects in regional and global broadband seismology, like moment tensor determination. The network, grown during the last 30 years within local Civil Defence agencies and neighbouring scientific institutions cooperation, currently consists of 11 digital broadband stations equipped with Streckeisen STS-2 and STS-1, Nanometrics Trillium 40 and Guralp CMG-3T seismometers with 120 and 40 seconds long period corners; most of the seismic stations are also equipped with accelerometers. Waveforms and parametric data of the NI seismic network are transmitted in real time to the Friuli-Venezia Giulia, Veneto and Provincia di Trento Civil Defence Agencies, to the Italian National Institute for Geophysics and Volcanology (INGV) and to the Earth Science Department (DST) of the Trieste University in Italy, to the Austrian Central Institute for Meteorology and Geodynamics (ZAMG) in Vienna, Austria and to the Environmental Agency of the Republic of Slovenia (ARSO) in Ljubljana, Slovenia to support emergency management and seismological studies in the whole Alps–Dinarides junction zone. The commercial Antelope software suite from BRTT has been chosen as the common basis for real time data exchange, rapid location of earthquakes and alerting. In order to guarantee high quality installations, we sustain a continuous effort that involves searches for appropriate sites, away from sources of long period noise, improvements in installation procedures and insulation techniques, maintenance of transfer function files and routine monitoring of noise conditions at individual existing station. The quality of the seismic data is checked through the noise Power Spectral Density (PSD) analysis. The insulation equipment that we designed for our network is a local adaptation of the pressure-thermal insulation experimented and routinely used by the world wide GEOFON seismic network and the German regional seismic network: examples and performances of a typical OGS installation will be shown

Magnetoelastic coupling associated with vacancy ordering and ferrimagnetism in natural pyrrhotite, Fe7S8.

Magnetoelastic coupling associated with the hexagonal-monoclinic transition in a natural sample of the mineral pyrrhotite, Fe7S8, has been analysed in terms of separate coupling of spontaneous strains with two discrete order parameters, q v for Fe/vacancy ordering and q m for magnetic ordering. Coupling of the two order parameters separately with strain gives rise to two terms for coupling between them, λ [Formula: see text] and λ [Formula: see text], and a pattern of evolution in which q v varies continuously and q m discontinuously through a single transition point. The transition is ferrimagnetic and ferroelastic but the relatively slow relaxation rate for Fe/vacancy ordering, in comparison with magnetic ordering, results in elastic and anelastic properties which are quite different from those observed in other ferroic or multiferroic materials with two instabilities. Instead of classical elastic softening, there is stiffening of the elastic constants which scales with [Formula: see text] and [Formula: see text]. Instead of the normal pattern of acoustic loss associated with the mobility and subsequent freezing for ferroelastic twin walls, the loss is consistently low throughout the temperature range 300 K-875 K