Contributions of the nine potential dust source regions (North and South Africa, the Arabian Peninsula, Central Asia, eastern and western China, North and South America, and Australia) to the global ...dust budget are investigated with a global dust transport model. A six-year simulation (1990 to 1995) indicates that the greatest contributor to the global dust budget is found to be North Africa (the Sahara Desert), which accounts for 58% of the total global dust emission and 62% of the total global dust load in the atmosphere. Australian dust dominates the southern hemisphere. The dust emission and atmospheric dust load originating from East Asia (eastern and western China) are estimated to be 214 Tg yr
−
1
and 1.1 Tg, respectively, which are 11% and 6% of the total global dust emission and dust load. Dust from East Asia dominates the atmospheric load over China and Mongolia (about 70%), Korea (60%), Japan (50%), and the North Pacific Ocean (40%). The contribution of dust originating from regions other than East Asia to the dust load over these East Asian countries and the North Pacific Ocean cannot be ignored. The simulated total dust deposition flux on Greenland suggests a possible overestimation of the Saharan dust and an underestimation of the East Asian dust in the Arctic region, which may be a common problem with global dust transport models. Possible reasons for the underestimation of the East Asian dust are discussed.
Cytokinins and auxins are major phytohormones involved in various aspects of plant growth and development. These phytohormones are also known to antagonize the effects of abscisic acid (ABA) on ...stomatal movement, and to affect ethylene biosynthesis. As ethylene has an antagonistic effect on ABA-induced stomatal closure, the possibility that the antagonistic effects of these phytohormones on ABA were mediated through ethylene biosynthesis was investigated. Both the cytokinin, 6-benzyladenine (BA), and the auxin, 1-naphthaleneacetic acid (NAA), antagonized ABA-induced stomatal closure in a manner similar to that following application of the ethylene precursor, 1-aminocyclopropane-1-carboxylic acid (ACC). However, these effects were negated when ethylene signalling, perception, or biosynthesis were blocked. As stomatal aperture is regulated by changes in guard cell volume, ABA application was found to reduce the volume of the guard cell protoplasts (GCP). It was found that BA, NAA, or ACC application compensated perfectly for the reduction in GCP volume by ABA application in WT plants. The above observations suggest that cytokinins and auxins inhibit ABA-induced stomatal closure through the modulation of ethylene biosynthesis, and that ethylene inhibits the ABA-induced reduction of osmotic pressure in the guard cells.
This paper reports two unique auroral features: postmidnight purple auroral rays and global Pc1 geomagnetic pulsations, observed before the onset of the corotating interaction region (CIR) storm of ...21 March 2017, at the beginning of the first campaign of the new Particles and Waves in the Inner magnetosphere using Ground‐based network observation (PWING) longitudinal ground network with the Arase satellite. The purple auroral rays were observed from ~0315 to 0430 UT (~03–04 magnetic local time) in the northeastern sky at Husafell, Iceland (magnetic latitude: 64.9°N). We newly propose that the entry of high‐density CIR plasma into the magnetotail created purple auroral rays in the sunlit ionosphere. Pc1 geomagnetic pulsations at frequencies of 0–0.5 Hz were observed after ~00 UT over a wide local time range, of 13 hr, from midnight to afternoon sectors at subauroral latitudes associated with CIR arrival. These results indicate preconditioning of the magnetosphere due to crossing of a CIR.
Plain Language Summary
We report auroral ray structures, which show a unique purple color, and global geomagnetic pulsations observed on 17 March 2017. The purple auroral rays were observed in the northeastern sky at Husafell, Iceland. The geomagnetic pulsations at frequencies of below 0.5 Hz were observed over a wide longitudinal range extending from midnight through morning to afternoon sectors at subauroral latitudes. These phenomena took place associated with the arrival of the so‐called corotating interaction region (CIR)” in the interplanetary space, which is characterized by high‐density high‐speed solar wind plasma. The CIR is one of the phenomena frequently occurring during the minimum phase of the 11‐year solar cycle. We suggest that the CIR can cause these unique purple auroras and global geomagnetic pulsations. The present observations also suggest a possible mechanism for dropout of radiation belt electrons due to electromagnetic ion cyclotron waves (=geomagnetic pulsations) associated with the CIR arrival.
Key Points
Unique postmidnight purple auroral rays and global Pc1/EMIC waves were observed during a CIR‐driven solar wind density enhancement
Pc1/EMIC waves were found over a wide longitudinal range extending from midnight through morning to the afternoon due to CIR arrival
Entry of high‐density solar wind plasma into the magnetotail may have created tall purple auroral rays in the sunlit ionosphere
Considerable efforts have been directed towards discovering and developing delivery vehicles for RNA therapeutics. While most studies emphasize the efficacy and safety of these delivery vehicles, few ...reports conduct a comprehensive assessment of their storage stability, a critical property for practical applications. Here, we report a potent and safe lipid nanoparticle with long-term storage stability. Through chemical synthesis and screening of cationic lipids, a formulation has been identified that enables potent knockdown of hepatocyte proteins in mice upon intravenous administration (siRNA ED50 ~0.02mg/kg). Toxicity studies revealed that a dose of 2mg/kg was well tolerated in rats, the most sensitive rodent model. We identified that a cyclic chemical structure in cationic lipids improved particle stability. The nanoparticles showed over 1.5year storage stability as a liquid, with over 90% siRNA encapsulation without any changes in particle size. This novel delivery material has promising potential as a drug product that could bring RNA therapeutics to the treatment of liver-related disorders.
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This study focuses on the one‐to‐one relationship between the morphology of polar mesosphere winter echo (PMWE) and cosmic noise absorption (CNA) as determined by measurements made with a single ...atmospheric radar, the Program of the Antarctic Syowa mesosphere‐stratosphere‐troposphere/incoherent scatter (PANSY) radar. CNA was calculated using the noise level in radar signal data collected during May 2013, including data of a solar proton event on 23 May. Using PMWE and CNA data in a common volume, their temporal variations and relation were examined in detail. PMWE altitude was clearly anticorrelated with CNA magnitude in a statistical sense: When a large CNA exceeding 0.50 dB took place, PMWE seemed to concentrate around 65 km and disappear above 70 km. The electron density behind the PMWE was estimated by using the ionospheric model for the auroral zone for the solar proton event. PMWE occurrence roughly coincided with a high electron density in the model, except that no PMWE was observed above 70 km at 0730 UT despite the electron density being higher than 108 m−3. Additionally, the estimated radar volume reflectivity with the Schmidt number Sc less than or equal to 1 is qualitatively consistent with the observed PMWE. Although weak turbulent energy dissipation rate can also play a dominant role in the observed PMWE decay, a plausible mechanism was small Sc or reduction of Sc that is equal to an increase in electron diffusivity resulting from an unusually high electron density, which significantly reduced radar volume reflectivity above 70 km.
Key Points
The PANSY radar observed simultaneous PMWE and CNA
PMWE below (above) 70 km intensified (decayed) with large CNA
The PMWE decay can be caused by small Sc or an increase in electron diffusivity due to high electron density
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