A Self-Similar Sine-Cosine Fractal Architecture for Multiport Interferometers

Multiport interferometers based on integrated beamsplitter meshes have recently captured interest as a platform for many emerging technologies. In this paper, we present a novel architecture for multiport interferometers based on the Sine-Cosine fractal decomposition of a unitary matrix. Our architecture is unique in that it is self-similar, enabling the construction of modular multi-chiplet devices. Due to this modularity, our design enjoys improved resilience to hardware imperfections as compared to conventional multiport interferometers. Additionally, the structure of our circuit enables systematic truncation, which is key in reducing the hardware footprint of the chip as well as compute time in training optical neural networks, while maintaining full connectivity. Numerical simulations show that truncation of these meshes gives robust performance even under large fabrication errors. This design is a step forward in the construction of large-scale programmable photonics, removing a major hurdle in scaling up to practical machine learning and quantum computing applications.Comment: 8 pages, 5 figure

Why do women not use antenatal services in low and middle income countries? A metasynthesis of qualitative studies

Background: Almost 50% of women in low & middle income countries (LMIC’s) don’t receive adequate antenatal care. Women’s views can offer important insights into this problem. Qualitative studies exploring inadequate use of antenatal services have been undertaken in a range of countries, but the findings are not easily transferable. We aimed to inform the development of future antenatal care programmes through a synthesis of findings in all relevant qualitative studies. Methods and Findings: Using a pre-determined search strategy, we identified robust qualitative studies reporting on the views and experiences of women in LMIC’s who received inadequate antenatal care. We used meta-ethnographic techniques to generate themes and a line of argument synthesis. We derived policy relevant hypotheses from the findings. We included 21 papers representing the views of more than 1230 women from 15 countries. Three key themes were identified: ‘Pregnancy as socially risky and physiologically healthy’; ‘Resource use and survival in conditions of extreme poverty’and ‘Not getting it right first time’. The line of argument synthesis describes a dissonance between programme design and cultural contexts that may restrict access and discourage return visits. We hypothesize that centralized, risk-focused antenatal care programmes may be at odds with the resources, beliefs and experiences of pregnant women who underuse antenatal services. Conclusions: Our findings suggest that there may be a mis-alignment between current antenatal provision and the social and cultural context of some women in LMIC’s. Antenatal care provision that is theoretically and contextually at odds with local contextual beliefs and experiences are likely to be underused, especially when attendance generates increased personal risks of lost family resource or physical danger during travel; when the promised care is not delivered due to resource constraints; and when women experience covert or overt abuse in care settings

Legionnaires' Disease with Facial Nerve Palsy

Legionnaires' disease is primarily a pneumonic process caused by Legionella pneumophilia, a gram-negative aerobic bacillus but also has multiple system involvement. The most common manifestation is encephalopathy suggesting a generalized brain dysfunction but focal neurological manifestations have been reported. We report a patient with Legionella pneumonia associated with cerebellar dysfunction and unilateral facial nerve weakness. 51-year-old previously healthy male presented with shortness of breath, cough, slurred speech, and unsteadiness on feet associated with malaise, fevers and myalgias. Patient's family reported facial asymmetry for 2 days. Patient had no significant medical history and was not on any medication. He denied smoking, alcohol or illicit drug use. Chest X-ray showed bilateral lower lobe infiltrates. Urinary antigen assay for Legionella pneumophilia serogroup 1 was positive. Patient was started on intravenous moxifloxacin. On day 5 the patient was discharged home and continued oral moxifloxacin for two weeks. After the two weeks, his respiratory symptoms, gait ataxia and dysarthria resolved. We report the first case of Legionnaires' disease with cerebellar dysfunction and seventh nerve palsy. Legionnaires' disease should be considered in patients with any neurological symptoms in the setting of pneumonia. Failure to recognize and treat the infection may lead to poor outcomes

MassFLOW-3D as a simulation tool for turbidity currents

Turbidity currents are the most important mechanism for the dispersal and deposition of sand in the deep-sea setting and thus the main phenomenon leading to the formation of oil and gas reservoirs in deep water deposits. The flow characteristics of turbidity currents are difficult to observe and study from the modern environment and their experimental approximations in the laboratory are typically limited by scaling issues, unrealistic flume geometries and short durations. Computational fluid dynamic (CFD) analysis, realised as numerical simulations, has been developed to fill the gap between the small and large scale, integrating data from theory, nature and experiments. CFD can also shed light on flow parameters which are so far impossible to deduce from experimental and field studies, such as detailed density and turbulent kinematic energy distributions. The deterministic process modelling CFD software MassFLOW-3D™ has been developed and used successfully to construct a three-dimensional model for the simulation of turbidity currents. All principal hydraulic properties of the flow (e.g. velocity, density, sediment concentration, apparent viscosity, turbulence intensity and bottom shear stress) and its responses to topography can be monitored continuously in three dimensions over the whole duration of the turbidity current. In this paper, comparisons made between the numerical output of MassFLOW-3DTM and the physical experiments are presented. In addition, the code is used to model the spatial characteristics, velocity structure and deposits of high-density turbidity currents and the flow dynamics of low-density turbidity currents in a sinuous channel. The numerical simulations show close fit to experimental sandy turbidity current dynamics for flows with sediment concentrations up to 27%. However, despite this initial success, on-going customisation and validation of these models, together with implementation of improved subroutines aimed at sediment transport and deposition, is essential in improving the computational code and our understanding of the natural phenomena