Whistler mode chorus waves can scatter plasma sheet electrons into the loss cone and produce the Earth's diffuse aurora. Van Allen Probes observed plasma sheet electron injections and intense chorus ...waves on 24 November 2012. We use quasilinear theory to calculate the precipitating electron fluxes, demonstrating that the chorus waves could lead to high differential energy fluxes of precipitating electrons with characteristic energies of 10–30 keV. Using this method, we calculate the precipitating electron flux from 2012 to 2019 when the Van Allen Probes were near the magnetic equator and perform global surveys of electron precipitation under different geomagnetic conditions. The most significant electron precipitation due to chorus is found from the nightside to dawn sectors over 4 < L < 6.5. The average total precipitating energy flux is enhanced during disturbed conditions, with time‐averaged values reaching ~3–10 erg/cm2/s when AE ≥ 500 nT.
Plain Language Summary
Whistler mode chorus is an electromagnetic emission present in the low‐density region of Earth's magnetosphere. Chorus waves can change the electron distribution in the plasma sheet to cause electron precipitation into Earth's upper atmosphere, leading to the diffuse aurora. We use satellite measurements of waves and electrons to quantify the electron precipitation from the plasma sheet to the upper atmosphere. An event study is presented to demonstrate that intense chorus waves observed near the magnetic equator can cause high energy fluxes of precipitating electrons with characteristic energy of 10–30 keV. To obtain the statistics of the electron precipitation, we calculate the precipitating electron flux from 2012 to 2019 using wave and electron measurements near the magnetic equator. Our survey indicates that chorus waves can cause the precipitation from the nightside to dawn sectors, over an equatorial radial distance of 4–6.5 Earth radii. The energy flux of electron precipitation is enhanced during disturbed geomagnetic conditions compared to quiet conditions. Our study provides the quantification of the empirical electron precipitation from the plasma sheet due to chorus on a global scale.
Key Points
We evaluate the electron precipitation due to whistler mode chorus waves and perform a global survey of the precipitating flux at L < 6.5
The chorus waves cause the precipitation of 1‐ to 100‐keV electrons predominantly from the nightside to dawn sectors over 4 < L < 6.5
Average total precipitating energy flux is enhanced during disturbed conditions, reaching 3–10 erg/cm2/s when AE > 500 nT
The oxidation states of magmas provide valuable information about the release and speciation of volatile elements during volcanic eruptions, metallogenesis, source rock compositions, open system ...magmatic processes, tectonic settings and potentially titanium (Ti) activity in chemical systems used for Ti-dependent geothermometers and geobarometers. In this paper we explore the use of Mn in apatite as an oxybarometer in intermediate and silicic igneous rocks. Increased Mn concentrations in apatite in granitic rocks from the zoned Criffell granitic pluton (southern Scotland) correlate with decreasing Fe2O3 (Fe3+) and Mn in the whole-rock and likely reflect increased Mn2+/Mn3+ and greater compatibility of Mn2+ relative to Mn3+ in apatite under reduced conditions. Fe3+/Fe2+ ratios in biotites have previously been used to calculate oxygen fugacities (fO2) in the outer zone granodiorites and inner zone granites where redox conditions have been shown to change from close to the magnetite-hematite buffer to close to the nickel-nickel oxide buffer respectively (Stephens et al., 1985). This trend is apparent in apatite Mn concentrations from a range of intermediate to silicic volcanic rocks that exhibit varying redox states and are shown to vary linearly and negatively with log fO2, such that logfO2=-0.0022(±0.0003)Mn(ppm)-9.75(±0.46)Variations in the Mn concentration of apatites appear to be largely independent of differences in the Mn concentration of the melt. Apatite Mn concentrations may therefore provide an independent oxybarometer that is amenable to experimental calibration, with major relevance to studies on detrital mineral suites, particularly those containing a record of early Earth redox conditions, and on the climatic impact of historic volcanic eruptions.
Summary
While murine CD4+CD39+ regulatory T cells (Treg) co‐express CD73 and hydrolyze exogenous (e) adenosine triphosphate (ATP) to immunosuppressive adenosine (ADO), surface co‐expression of CD73 ...on human circulating CD4+CD39+ Treg is rare. Therefore, the ability of human Treg to produce and utilize ADO for suppression remains unclear. Using mass spectrometry, we measured nucleoside production by subsets of human CD4+CD39+ and CD4+CD39(–)CD73+ T cells or CD19+ B cells isolated from blood of 30 volunteers and 14 cancer patients. CD39 and CD73 expression was evaluated by flow cytometry, Western blots, confocal microscopy or reverse transcription–polymerase chain reaction (RT–PCR). Circulating CD4+CD39+ Treg which hydrolyzed eATP to 5′‐AMP contained few intracytoplasmic granules and had low CD73 mRNA levels. Only ∼1% of these Treg were CD39+CD73+. In contrast, CD4+CD39negCD73+ T cells contained numerous CD73+ granules in the cytoplasm and strongly expressed surface CD73. In vitro‐generated Treg (Tr1) and most B cells were CD39+CD73+. All these CD73+ T cell subsets and B cells hydrolyzed 5′‐AMP to ADO. Exosomes isolated from plasma of normal control (NC) or cancer patients carried enzymatically active CD39 and CD73+ and, when supplied with eATP, hydrolyzed it to ADO. Only CD4+CD39+ Treg co‐incubated with CD4+CD73+ T cells, B cells or CD39+CD73+ exosomes produced ADO. Thus, contact with membrane‐tethered CD73 was sufficient for ADO production by CD4+CD39+ Treg. In microenvironments containing CD4+CD73+ T cells, B cells or CD39+CD73+ exosomes, CD73 is readily available to CD4+CD39+CD73neg Treg for the production of immunosuppressive ADO.
Mitigation measures to disperse marine mammals prior to pile-driving include acoustic deterrent devices and piling soft starts, but their efficacy remains uncertain. We developed a self-contained ...portable hydrophone cluster to detect small cetacean movements from the distributions of bearings to detections. Using an array of clusters within 10 km of foundation pile installations, we tested the hypothesis that harbour porpoises (
) respond to mitigation measures at offshore windfarm sites by moving away. During baseline periods, porpoise movements were evenly distributed in all directions. By contrast, animals showed significant directional movement away from sound sources during acoustic deterrent device use and piling soft starts. We demonstrate that porpoises respond to measures aimed to mitigate the most severe impacts of construction at offshore windfarms by swimming directly away from these sound sources. Portable directional hydrophone clusters now provide opportunities to characterize responses to disturbance sources across a broad suite of habitats and contexts.
We report the first CW Ka-band radio-frequency (RF) power measurements at 35 GHz from a passivated Al 0.82 In 0.18 N/GaN high-electron mobility transistor on SiC with 9.8-nm-thin barrier. This device ...delivered a maximum of 5.8 W/mm with a power-added efficiency of 43.6% biased at V DS = 20 V and 10% I DSS when matched for power at CW. The device was grown by metal-organic chemical vapor deposition with 2.8-¿m source-drain spacing and a gate length of 160 nm. An excellent ohmic contact was obtained with an R c of 0.62 ¿·mm. The maximum extrinsic transconductance was 354 mS/mm with an I DSS of 1197 mA/mm at a V GS of 0 V, an ft of 79 GHz, and an f max of 113.8 GHz.
Unstrained high-electron mobility transistors (HEMTs) were fabricated from InAlN/GaN on semi-insulating SiC substrates. The devices had 0.24-mum T-gates with a total width of 2times150 mum. Final ...passivated performance values for these devices are I max =1279 mA/mm, I DSS =1182 mA/mm, R c =0.43 Omegamiddotmm, rho s =315 Omega/sq, f T =45 GHz, f max(MAG) =64 GHz, and g m =268 mS/mm. Continuous-wave power measurements at 10 GHz produced P sat =3.8 W/mm, G t =8.6 dB, and PAE=30% at V DS =20 V at 25% I DSS . To our knowledge, these are the first power measurements reported at 10 GHz for this material
Plant functional trait classifications have provided a useful framework for understanding the biodiversity of natural ecosystems. Here we propose that trait-based ecology may be expanded for ...understanding urban biodiversity in human planted and human dominated land cover by including plant attributes that influence human choices about cultivated species in novel ecosystems. We measured leaf functional traits in 24 tree species grown in the Los Angeles region of southern California in order to assess whether leaf functional traits were (1) predictable based on biogeographic region of origin, and (2) related to urban plant performance and ecosystem-services based traits. This entailed the development of a proposed new, ecosystem services-based classification of tree species traits is based on ∼1000 household surveys of the preferences of urban residents for specific tree attributes in southern California. We evaluated the relationship between leaf functional traits, ecosystem services-based traits, and urban tree performance as measured by stem growth and predawn leaf water potential (as a metric of rooting distributions). Leaf functional traits were strongly predictable based on species' biogeographic region of origin including native habitat type and continent of origin, and hence appeared to be conserved in the urban environment. Ecosystem services-based traits such as tree water use, provision of showy flowers, size at maturity, and growth rates were also predictable based on geographic region of origin, and several ecosystem services-based traits were related to leaf functional traits. We suggest that ecosystem services-based traits may be useful variables to quantify in studies of urban forest community assembly, where species composition is strongly influenced by decision-making based on the preferences of urban residents and stakeholders. Our initial ecosystem services-based trait classification is defined from the results of household surveys and measurements in the Los Angeles area; these results are likely to vary by location, and can be improved with additional data on the performance, physiology, and morphology of urban trees as well as a better understanding of human preferences by region.
Genes and mechanisms involved in common complex diseases, such as the autoimmune disorders that affect approximately 5% of the population, remain obscure. Here we identify polymorphisms of the ...cytotoxic T lymphocyte antigen 4 gene (CTLA4)--which encodes a vital negative regulatory molecule of the immune system--as candidates for primary determinants of risk of the common autoimmune disorders Graves' disease, autoimmune hypothyroidism and type 1 diabetes. In humans, disease susceptibility was mapped to a non-coding 6.1 kb 3' region of CTLA4, the common allelic variation of which was correlated with lower messenger RNA levels of the soluble alternative splice form of CTLA4. In the mouse model of type 1 diabetes, susceptibility was also associated with variation in CTLA-4 gene splicing with reduced production of a splice form encoding a molecule lacking the CD80/CD86 ligand-binding domain. Genetic mapping of variants conferring a small disease risk can identify pathways in complex disorders, as exemplified by our discovery of inherited, quantitative alterations of CTLA4 contributing to autoimmune tissue destruction.
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