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Investigating the possible contribution of helicity condensation to the ambient increase in solar open flux
No full textThe Sun's Open Flux plays a vital role in heliospheric physics and for the origin of the solar wind. A key problem faced by global magnetic field models of the solar corona is that they consistently underestimate the amount of Open Flux compared to in situ measurements. The purpose of the present paper is to consider if statistically averaged helicity condensation (SAHC) can reduce this discrepancy by increasing the simulated Open Flux found in potential field source surface (PFSS) models. We consider each Carrington rotation from 1646–2149 (1976 September to 2014 April). For each rotation, we hold the photosphere fixed, construct a PFSS model, and inject nonpotentiality into the coronal field by applying SAHC at different angular rotation rates, ω. When ω exceeds 2.5 × 10−6 s−1, both ambient and sporadic enhancements of Open Flux are found within the Carrington rotation timescale. As ω increases, the amount of ambient Open Flux increases, along with the frequency of sporadic events. These enhancements are accompanied by increased footpoint area of open field lines, where the open field locations at each pole expand by up to 3°–6° of latitude. A solar cycle dependence is found with higher increases in ambient Open Flux at solar maximum compared to solar minimum. Comparing our results with 27 day averaged OMNI spacecraft measurements, our highest value of ω = 10 × 10−6 s−1 can resolve just under 50% of the discrepancy between in situ Open Flux measurements and PFSS models. Although helicity condensation cannot fully resolve the discrepancy, it can significantly contribute toward reducing it.</div
Diversity and abundance of ring nucleases in type III CRISPR-Cas loci
No full textMost type III CRISPR-Cas systems facilitate immune responses against invading mobile genetic elements such as phages by generating cyclic oligoadenylates (cOAs). Downstream effectors activated by cOAs are typically non-specific proteins that induce damage to essential cellular components, thereby preventing phage epidemics. Due to these toxic effects, it is crucial that the production and concentration of cOAs remain under tight regulatory control during infection-free periods or when deactivating the immune response after clearing an infection. Type III CRISPR loci often encode enzymes known as ring nucleases (RNs) that bind and degrade specific cOAs, while some effectors are auto-deactivating. Despite the discovery of several classes of RNs, a comprehensive bioinformatic analysis of type III CRISPR-Cas loci in this context is lacking. Here, we examined 38,742 prokaryotic genomes to provide a global overview of type III CRISPR loci, focussing on the known and predicted RNs. The candidate RNs Csx16 and Csx20 are confirmed as active enzymes, joining Crn1-3. Distributions and patterns of co-occurrence of RNs and associated effectors are explored, allowing the conclusion that a sizeable majority of type III CRISPR systems regulate cOA levels by degrading the signalling molecules, which has implications for cell fate following viral infection.This article is part of the discussion meeting issue ‘The ecology and evolution of bacterial immune systems’
Shooting for the moon:Benjamin Peirce’s ambitious 19<sup>th</sup>-century efforts to elevate American mathematics through astronomy
No full textOver fifty years as a mathematics professor at Harvard, Benjamin Peirce worked to elevate mathematical sciences in the US by championing educational reform, promoting research-level publication, and strategizing about scientific funding. He used his roles in the Nautical Almanac Office and the US Coast Survey to train and employ a generation of mathematical astronomers. Peirce further capitalized on the public enthusiasm generated by The Great Comet in 1843, the discovery of Neptune in 1846, observations of Saturn’s rings in the 1850s, and a number of total solar eclipses in the 1860s and 70s. Consistent and intentional advocacy from Benjamin Peirce sought to elevate the profile of American mathematics through astronomical work. This shaped how mathematics developed within the broader context of the establishment of scientific infrastructure in mid-nineteenth-century America
Review of <i>Literature and the Telephone: Conversations on Poetics, Politics and Place</i>
No full textSilence and fiction:female writing and the construction of Arab female experience in <i>The Blind Sindbad: Maps of the Ocean and War</i>
No full textVisible light communication using thermally activated delayed fluorescent OLEDs
No full textThermally activated delayed fluorescent (TADF) materials are appealing due to their ability to make efficient organic light-emitting diodes (OLEDs). In this study, we develop TADF OLEDs for visible light communication (VLC) and show that devices using the TADF emitter 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene (4CzIPN) can achieve a data rate of 54 Mbps over a 2 m VLC link. To enhance the bandwidth and data rate, we then developed TADF-sensitized fluorescent (hyperfluorescent) OLEDs. Using the fluorescent material 5,10,15,20-tetraphenylbisbenz[5,6]indeno[1,2,3-cd:1′,2′,3′-lm]perylene (DBP) as the terminal emitter, we achieve a data rate of 102 Mbps, which is much higher than the 10 Mbps reported for a phosphorescent OLED. Our results show that TADF and hyperfluorescent OLEDs are suitable for optical wireless communication, as the delayed fluorescence was found not to limit the data rate. This is particularly relevant for VLC applications requiring higher efficiency than fluorescent OLEDs can provide, such as lighting and displays
Framing the First World War:how divergent views shaped a global conflict
No full textThis innovative approach to the history of World War I looks at ways in which military actors saw and perceived war, and how that exerted a significant influence over the decisions they made and the actions they took.The character of the conflict that erupted in 1914 defied the expectations of many political leaders and military analysts. Despite the mountains of books and articles published on World War I, there has been surprisingly little systematic or comparative research on how military commanders and politicians framed and interpreted the conflict—or, indeed, on how they understood war itself—and how that understanding shaped their decision-making.Wars are fought by organizations and people who have disparate visions of the world they live in and the conflict they are fighting. In Framing the First World War, a team of leading scholars explore the gulf between imagined warfare and the realities of battle. By doing so, they investigate how the military forces that contested the First World War framed the conflict they were involved in and how those perspectives shaped and influenced the ways in which they sought to understand, conduct, and respond to the war. They use the notion of “frames” and the concept of “framing” to enable us to engage directly with the complexity and diversity of the conflict, which was fought for different reasons and in different ways, incorporating a range of issues with implications for the conduct of the war.Improving our appreciation of how commanders saw the world around them and their views on the war they were conducting opens up valuable new approaches for understanding debates over the higher direction of the conflict and the civil-military relations that underpinned them. The contributors to Framing the First World War work towards a fuller historical appraisal of how military figures understood the war, moving beyond a purely military analysis to incorporate broader cultural and social topics, including education, medicine, politics, and law