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

Mechanism of resonant electron emission from the deprotonated GFP chromophore and its biomimetics

The Green Fluorescent Protein (GFP), which is widely used in bioimaging, is known to undergo light-induced redox transformations. Electron transfer is thought to occur resonantly through excited states of its chromophore; however, a detailed understanding of the electron gateway states of the chromophore is still missing. Here, we use photoelectron spectroscopy and high-level quantum chemistry calculations to show that following UV excitation, the ultrafast electron dynamics in the chromophore anion proceeds via an excited shape resonance strongly coupled to the open continuum. The impact of this state is found across the entire 355–315 nm excitation range, from above the first bound–bound transition to below the opening of higher-lying continua. By disentangling the electron dynamics in the photodetachment channels, we provide an important reference for the adiabatic position of the electron gateway state, which is located at 348 nm, and discover the source of the curiously large widths of the photoelectron spectra that have been reported in the literature. By introducing chemical modifications to the GFP chromophore, we show that the detachment threshold and the position of the gateway state, and hence the underlying excited-state dynamics, can be changed systematically. This enables a fine tuning of the intrinsic electron emission properties of the GFP chromophore and has significant implications for its function, suggesting that the biomimetic GFP chromophores are more stable to photooxidation

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

Quantum internet using code division multiple access

A crucial open problem in large-scale quantum networks is how to efficiently transmit quantum data among many pairs of users via a common data-transmission medium. We propose a solution by developing a quantum code division multiple access (q-CDMA) approach in which quantum information is chaotically encoded to spread its spectral content, and then decoded via chaos synchronization to separate different sender-receiver pairs. In comparison to other existing approaches, such as frequency division multiple access (FDMA), the proposed q-CDMA can greatly increase the information rates per channel used, especially for very noisy quantum channels.Comment: 29 pages, 6 figure

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

Youth Can Become Effective Leaders in Lebanon

Research and Policy Memo #

Understanding and enhancing future infrastructure resiliency: a socio-ecological approach

The resilience of any system, human or natural, centres on its capacity to adapt its structure, but not necessarily its function, to a new configuration in response to long-term socio-ecological change. In the long term, therefore, enhancing resilience involves more than simply improving a system's ability to resist an immediate threat or to recover to a stable past state. However, despite the prevalence of adaptive notions of resilience in academic discourse, it is apparent that infrastructure planners and policies largely continue to struggle to comprehend longer-term system adaptation in their understanding of resilience. Instead, a short-term, stable system (STSS) perspective on resilience is prevalent. This paper seeks to identify and problematise this perspective, presenting research based on the development of a heuristic 'scenario-episode' tool to address, and challenge, it in the context of United Kingdom infrastructure resilience. The aim is to help resilience practitioners to understand better the capacities of future infrastructure systems to respond to natural, malicious threats