1,722,360 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Food insecurity, safety nets, and coping strategies during the COVID-19 pandemic: Multi-country evidence from sub-saharan Africa
Get PDFThe COVID-19 pandemic has affected food security across the world. As governments respond in different ways both with regards to containing the pandemic and addressing food insecurity, in parallel detailed datasets are being collected and analysed. To date, literature addressing food insecurity during the pandemic, using these datasets, has tended to focus on individual countries. By contrast, this paper provides the first detailed multi-country cross-sectional snapshot of the social dimensions of food insecurity during the COVID-19 pandemic across nine African countries (Chad, Djibouti, Ethiopia, Kenya, Malawi, Mali, Nigeria, South Africa, and Uganda). Econometric analysis reveals that female-headed households, the poor, and the less-formally educated, appear to suffer more in terms of food insecurity during this global pandemic. Importantly, our findings show that the negative consequences of the pandemic are disproportionately higher for lower-income households and those who had to borrow to make ends meet rather than relying on savings; impacts are country-specific; and there is considerable spatial heterogeneity within country food insecurity, suggesting that tailored policies will be required. These nine countries employ both food and cash safety nets, with the evidence suggesting that, at least when these data were collected, cash safety nets have been slightly more effective at reducing food insecurity. Our results provide a baseline that can be used by governments to help design and implement tailored policies to address food insecurity. Our findings can also be used as lessons to reshape policies to tackle the heterogeneous impacts of climate change
Simulating the Brillouin response of arbitrary optical fibres with a finite element method
No full textStimulated Brillouin scattering (SBS) is an important nonlinear optical phenomenon that has been gainfully exploited in many important applications/devices such as slow light generation, Brillouin amplifiers/lasers, and distributed sensing. On the other hand, it is a highly undesirable effect in telecoms applications and in fibre-based devices like parametric amplifiers and fibre lasers. Thus, significant research efforts have been focussed on designing optical fibres with tailored acousto-optic interactions in order to enhance/mitigate their SBS characteristics, which necessitates evaluating their Brillouin gain spectrum (BGS). Various theoretical and numerical techniques for calculating BGS have been reported in recent years, though the applicability of most of these are limited to fibres with radial symmetry and/or weak acoustic guiding properties. In this paper, for the first time to the best of our knowledge, we employ a commercial finite-element method (FEM) solver to calculate the optical and acoustic modes of arbitrary longitudinally invariant fibres and thus determine their BGS. The method, a derivation of the one presented in [1], can be applied to solid fibres with arbitrary refractive index profiles, as well as to microstructured optical fibres (MOFs). Comparisons with reported simulations and with experimental results confirm the accuracy of our implementation
Alexander Crum Brown: A Forgotten Pioneer in Vestibular Sciences
No full textAlthough vestibular anatomy was described in the Renaissance period, research in vestibular physiology began in the 1820s and was spearheaded by Purkinje and Flourens. This was subsequently expanded by Ménière, Helmholtz, Goltz, Mach, Breuer, Ewald, and Hogyes, who are regarded as the early pioneers in research on vestibular physiology in the 19th century. The relationship of endolymphatic flow and semicircular canal function is termed the Mach-Breuer hypothesis. What is less well known is that a Scottish chemist, Alexander Crum Brown, arrived at similar conclusions as Mach and Breuer at the same time quite independently. In fact, he pioneered several concepts in vestibular physiology that included pairing of semicircular canals for function, the vestibular pathway, optic fixation elimination in vestibular experimentation, the theory of motion intolerance, and study in deaf mutes for insights into vestibular pathology and vestibular compensation. This article is a tribute to this forgotten pioneer in vestibular research
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