The implementation of wideband 90° hybrids on non-optimal substrates

A new technique to implement wideband 90° hybrid coupling profiles on non-optimal substrate configurations is presented. The technique uses an impedance taper over the whole length of the hybrid to remove the restriction of a substrate defined maximum coupling coefficient at crossover, thus resulting in much more flexibility for the implementation of hybrids on integrated printed circuit boards. The choice of board thicknesses and material type no longer needs to be dominated by the hybrid, but can be optimized for other components or priorities. The flexibility provided by the technique is shown in the implementation of a 2–18 GHz hybrid on a large range of substrate thicknesses as well as on a non-optimal substrate material, for which acceptable measured performance is still obtained.http://wileyonlinelibrary.com/iet-elam2022Electrical, Electronic and Computer Engineerin

The bii4africa dataset of faunal and floral population intactness estimates across Africa’s major land uses

Sub-Saharan Africa is under-represented in global biodiversity datasets, particularly regarding the impact of land use on species’ population abundances. Drawing on recent advances in expert elicitation to ensure data consistency, 200 experts were convened using a modified-Delphi process to estimate ‘intactness scores’: the remaining proportion of an ‘intact’ reference population of a species group in a particular land use, on a scale from 0 (no remaining individuals) to 1 (same abundance as the reference) and, in rare cases, to 2 (populations that thrive in human-modified landscapes). The resulting bii4africa dataset contains intactness scores representing terrestrial vertebrates (tetrapods: ±5,400 amphibians, reptiles, birds, mammals) and vascular plants (±45,000 forbs, graminoids, trees, shrubs) in sub-Saharan Africa across the region’s major land uses (urban, cropland, rangeland, plantation, protected, etc.) and intensities (e.g., large-scale vs smallholder cropland). This dataset was co-produced as part of the Biodiversity Intactness Index for Africa Project. Additional uses include assessing ecosystem condition; rectifying geographic/ taxonomic biases in global biodiversity indicators and maps; and informing the Red List of Ecosystems

Interactions between Woody Plants and Browsing Mammals Mediated by Secondary Metabolites

Mammals must overcome several challenges to exploit woody plants; these include variation among plant species, individuals, growth stages, and parts in their nutritional value and mechanical and chemical defenses (91). The latter are especially significant because woody plants produce a variety of secondary metabolites (56), many of which are chemical defenses against browsing by mammals and some of which appear to be an evolutionary response to browsing by mammals (12a). Not all secondary metabolites are equally effective as defenses against browsing, and none provides complete protection (98), because mammals have evolved anatomical, physiological, and behavioral counters to plant defenses (27, 61, 91). As a result, some woody plants are browsed more than others. The effects of secondary metabolites occur at different hierarchical scales, ranging from individual plants to ecosystems. There are recent reviews of the evolutionary and environmental controls of chemical defenses against browsing, and of the physiological and biochemical mechanisms mammals use to counter these defenses (61, 81). This review concerns three aspects of chemically mediated interactions between woody plants and browsing mammals: (i) chemical specificity and toxicity, (ii) learning as a counter to chemical defense, and (iii) the effects of chemical defense on plant communities and ecosystems

The 2015-19 multi year drought in the Eastern Cape, South Africa : it's evolution and impacts on agriculture

The Eastern Cape Province, and in particular, it's interior western Karoo region, has long been subject to periodic droughts, with significant implications for it's agricultural sector. From 2015, with some recovery in 2020, the area experienced a severe multi year drought, with negative impacts for a range of sectors, including extensive livestock farming. At the time of the drought, a common narrative in the media stated that the drought was unprecedented. In this paper, we analyze how the drought evolved climatically, as well as its impacts on vegetation and farming conditions. Our findings indicate that it would appear that the drought was not unprecedented. It was, however, considered to be extremely severe – with some local impacts found to be critical. Loss of production impacts, and loss of income, now compounded by the difficulties resulting from the COVID19 pandemic (which has impacted the South African economy severely) are likely to continue to impact the agricultural sector in the Eastern Cape for some time – and given the likelihood of increased frequency of extreme events in southern Africa in the future, we may see more frequent subsequent severe multi-year events.EA's Rated Researchers grant from the National Research Foundationhttp://www.elsevier.com/locate/jaridenvhj2021Geography, Geoinformatics and Meteorolog