Oceanic Frontogenesis McWilliams, James C
Annual review of marine science,
01/2021, Letnik:
13, Številka:
1
Journal Article
Recenzirano
Frontogenesis is the fluid-dynamical processes that rapidly sharpen horizontal density gradients and their associated horizontal velocity shears. It is a positive feedback process where the ...ageostrophic, overturning secondary circulation in the cross-front plane accelerates the frontal sharpening until an arrest occurs through frontal instability and other forms of turbulent mixing. Several well-known types of oceanic frontal phenomena are surveyed, their impacts on oceanic system functioning are assessed, and future research is envisioned.
Abstract
Background
Troponin elevation is common in hospitalized COVID-19 patients, but underlying aetiologies are ill-defined. We used multi-parametric cardiovascular magnetic resonance (CMR) to ...assess myocardial injury in recovered COVID-19 patients.
Methods and results
One hundred and forty-eight patients (64 ± 12 years, 70% male) with severe COVID-19 infection all requiring hospital admission, 48 (32%) requiring ventilatory support and troponin elevation discharged from six hospitals underwent convalescent CMR (including adenosine stress perfusion if indicated) at median 68 days. Left ventricular (LV) function was normal in 89% (ejection fraction 67% ± 11%). Late gadolinium enhancement and/or ischaemia was found in 54% (80/148). This comprised myocarditis-like scar in 26% (39/148), infarction and/or ischaemia in 22% (32/148) and dual pathology in 6% (9/148). Myocarditis-like injury was limited to three or less myocardial segments in 88% (35/40) of cases with no associated LV dysfunction; of these, 30% had active myocarditis. Myocardial infarction was found in 19% (28/148) and inducible ischaemia in 26% (20/76) of those undergoing stress perfusion (including 7 with both infarction and ischaemia). Of patients with ischaemic injury pattern, 66% (27/41) had no past history of coronary disease. There was no evidence of diffuse fibrosis or oedema in the remote myocardium (T1: COVID-19 patients 1033 ± 41 ms vs. matched controls 1028 ± 35 ms; T2: COVID-19 46 ± 3 ms vs. matched controls 47 ± 3 ms).
Conclusions
During convalescence after severe COVID-19 infection with troponin elevation, myocarditis-like injury can be encountered, with limited extent and minimal functional consequence. In a proportion of patients, there is evidence of possible ongoing localized inflammation. A quarter of patients had ischaemic heart disease, of which two-thirds had no previous history. Whether these observed findings represent pre-existing clinically silent disease or de novo COVID-19-related changes remain undetermined. Diffuse oedema or fibrosis was not detected.
Graphical Abstract
Recent studies showing temporal changes in local and regional insect populations received exaggerated global media coverage. Confusing and inaccurate science communication on this important issue ...could have counterproductive effects on public support for insect conservation. The insect apocalypse narrative is fuelled by a limited number of studies that are restricted geographically (predominantly the United Kingdom, Europe, the United States) and taxonomically (predominantly some bees, macrolepidoptera, and ground beetles). Biases in sampling and analytical methods (e.g., categorical versus continuous time series, different diversity metrics) limit the relevance of these studies as evidence of generalized global insect decline. Rather, the value of this research lies in highlighting important areas for priority investment. We summarize research, communication, and policy priorities for evidence-based insect conservation, including key areas of knowledge to increase understanding of insect population dynamics. Importantly, we advocate for a balanced perspective in science communication to better serve both public and scientific interests.
Island Biodiversity in the Anthropocene Russell, James C; Kueffer, Christoph
Annual review of environment and resources,
10/2019, Letnik:
44, Številka:
1
Journal Article
Recenzirano
Biodiversity on marine islands is characterized by unique biogeographic, phylogenetic and functional characteristics. Islands hold a disproportionate amount of the world's biodiversity, and they have ...also experienced a disproportionate loss of it. Following human contact, island biodiversity has sustained negative human impacts increasing in rate and magnitude as islands transitioned from primary through secondary to tertiary economies. On islands, habitat transformation and invasive non-native species have historically been the major threats to biodiversity, and although these threats will continue in new forms, new impacts such as human-induced climate change and sea-level rise are emerging. Island biodiversity is changing with some species going extinct, others changing in abundance, non-native species becoming a part of many ecosystems, and humans shaping many ecological processes. Islands thus are microcosms for the emerging biodiversity and socioecological landscapes of the Anthropocene. Islands will require new strategies for the protection and restoration of their biodiversity, including maintaining biological and cultural heritage through regenerative practices, mainstreaming biodiversity in cultural and production landscapes, and engaging with the reality of novel ecosystems.
Three amigos: Direct oxidative amination of the C2‐position of azoles enables the synthesis of important classes of heterocycle in an efficient and atom‐economic manner (see scheme). Recent research ...has uncovered three distinct approaches to this transformation.
Theories of Error Back-Propagation in the Brain Whittington, James C.R.; Bogacz, Rafal
Trends in cognitive sciences,
March 2019, 2019-03-00, 20190301, Letnik:
23, Številka:
3
Journal Article
Recenzirano
Odprti dostop
This review article summarises recently proposed theories on how neural circuits in the brain could approximate the error back-propagation algorithm used by artificial neural networks. Computational ...models implementing these theories achieve learning as efficient as artificial neural networks, but they use simple synaptic plasticity rules based on activity of presynaptic and postsynaptic neurons. The models have similarities, such as including both feedforward and feedback connections, allowing information about error to propagate throughout the network. Furthermore, they incorporate experimental evidence on neural connectivity, responses, and plasticity. These models provide insights on how brain networks might be organised such that modification of synaptic weights on multiple levels of cortical hierarchy leads to improved performance on tasks.
The error back-propagation algorithm can be approximated in networks of neurons, in which plasticity only depends on the activity of presynaptic and postsynaptic neurons.
These biologically plausible deep learning models include both feedforward and feedback connections, allowing the errors made by the network to propagate through the layers.
The learning rules in different biologically plausible models can be implemented with different types of spike-time-dependent plasticity.
The dynamics and plasticity of the models can be described within a common framework of energy minimisation.
The status of room‐temperature potassium‐ion batteries is reviewed in light of recent concerns regarding the rising cost of lithium and the fact that room‐temperature sodium‐ion batteries have yet to ...be commercialised thus far. Initial reports of potassium‐ion cells appear promising given the infancy of the research area. This review presents not only an overview of the current potassium‐ion battery literature, but also attempts to provide context by describing previous developments in lithium‐ion and sodium‐ion batteries and the electrochemical reaction mechanisms discovered thus far. Perspectives and directions on the techniques available to characterize newly developed battery materials are also provided based on our experience and knowledge from the literature. It is hoped that through this review, the potential of potassium‐ion batteries as a competitive energy‐storage technology will be realised, and the accessibility and available knowledge of the techniques required to develop the technology will be made apparent.
A critical review and perspectives of electrode materials for potassium‐ion batteries, and the techniques available to characterise the materials or devices and search for new materials are presented.
This research used molecular modeling and rotating disk electrode experiments (RDE) to investigate possible reaction pathways for persulfate production via electrolysis of sulfuric acid solutions ...using boron doped diamond (BDD) film anodes. Density functional theory (DFT) modeling indicated that uncatalyzed oxidation of SO42− and HSO4− occurs at lower potentials than water oxidation, and that sulfate radical species (SO4−• and HSO4•) may be produced via direct electron transfer, or via reaction with hydroxyl radicals. The RDE experiments indicated that rates of persulfate generation were strongly dependent of the condition of the electrode surface, and that aged electrode surfaces favored water oxidation over direct SO42− and HSO4− oxidation. Combination of sulfate radical species in solution is the lowest energy pathway for persulfate production. Sulfate radical species may also react with radical sites on the electrode surface and produce chemisorbed intermediates that can stabilize sulfate radical species. Reaction of the chemisorbed intermediates with a bisulfate radical can produce persulfate via a surface catalyzed pathway. However, the activation barriers for this pathway are much higher than those for persulfate production via solution phase species.
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