Active auroral arc powered by accelerated electrons from very high altitudes

オーロラ粒子の加速領域が超高高度まで広がっていたことを解明 －オーロラ粒子の加速の定説を覆す発見－. 京都大学プレスリリース. 2021-01-20.Bright, discrete, thin auroral arcs are a typical form of auroras in nightside polar regions. Their light is produced by magnetospheric electrons, accelerated downward to obtain energies of several kilo electron volts by a quasi-static electric field. These electrons collide with and excite thermosphere atoms to higher energy states at altitude of ~ 100 km; relaxation from these states produces the auroral light. The electric potential accelerating the aurora-producing electrons has been reported to lie immediately above the ionosphere, at a few altitudes of thousand kilometres1. However, the highest altitude at which the precipitating electron is accelerated by the parallel potential drop is still unclear. Here, we show that active auroral arcs are powered by electrons accelerated at altitudes reaching greater than 30, 000 km. We employ high-angular resolution electron observations achieved by the Arase satellite in the magnetosphere and optical observations of the aurora from a ground-based all-sky imager. Our observations of electron properties and dynamics resemble those of electron potential acceleration reported from low-altitude satellites except that the acceleration region is much higher than previously assumed. This shows that the dominant auroral acceleration region can extend far above a few thousand kilometres, well within the magnetospheric plasma proper, suggesting formation of the acceleration region by some unknown magnetospheric mechanisms

P-type low-molecular-weight hydrogelators

As the use of low-molecular-weight gelators (LMWGs) as components in single and multicomponent systems for optoelectronic and solar cell applications increases, so does the need for more functional gelators. There are relatively few examples of p-type gelators that can be used in such systems. Here, the synthesis and characterization of three amino-acid-functionalized p-type gelators based on terthiophene, tetrathiafulvalene, and oligo(phenylenevinylene) are described. The cores of these molecules are already used as electron donors in optoelectronic applications. These newly designed molecules can gel water to form highly organized structures, which can be dried into thin films that show p-type behavior

Base methylations in the double-stranded RNA by a fused methyltransferase bearing unwinding activity

Modifications of rRNAs are clustered in functional regions of the ribosome. In Helix 74 of Escherichia coli 23S rRNA, guanosines at positions 2069 and 2445 are modified to 7-methylguanosine(m7G) and N2-methylguanosine(m2G), respectively. We searched for the gene responsible for m7G2069 formation, and identified rlmL, which encodes the methyltransferase for m2G2445, as responsible for the biogenesis of m7G2069. In vitro methylation of rRNA revealed that rlmL encodes a fused methyltransferase responsible for forming both m7G2069 and m2G2445. We renamed the gene rlmKL. The N-terminal RlmL activity for m2G2445 formation was significantly enhanced by the C-terminal RlmK. Moreover, RlmKL had an unwinding activity of Helix 74, facilitating cooperative methylations of m7G2069 and m2G2445 during biogenesis of 50S subunit. In fact, we observed that RlmKL was involved in the efficient assembly of 50S subunit in a mutant strain lacking an RNA helicase deaD

Theory Techniques for Precision Physics -- Snowmass 2021 TF06 Topical Group Report

The wealth of experimental data collected at laboratory experiments suggests that there is some scale separation between the Standard Model (SM) and phenomena beyond the SM (BSM). New phenomena can manifest itself as small corrections to SM predictions, or as signals in processes where the SM predictions vanish or are exceedingly small. This makes precise calculations of the SM expectations essential, in order to maximize the sensitivity of current and forthcoming experiments to BSM physics. This topical group report highlights some past and forthcoming theory developments critical for maximizing the sensitivity of the experimental program to understanding Nature at the shortest distances.Comment: 36 pages, 2 figures. Report of the TF06 topical group for Snowmass 202

Functional analysis of GbAGL1, a D-lineage gene from cotton (Gossypium barbadense)

Cotton fibres originate from the outer ovule integument and D-lineage genes are essential for ovule development and their roles can be described by the ‘ABCDE’ model of flower development. To investigate the role of D-lineage genes during ovule and fibre development, GbAGL1 (GenBank accession number: FJ198049) was isolated from G. barbadense by using the SMART RACE strategy. Sequence and phylogenetic analyses revealed that GbAGL1 was a member of the D-lineage gene family. Southern blot analysis showed that GbAGL1 belonged to a low-copy gene family. Semi-quantitative RT-PCR and RNA in situ hybridization analyses revealed that the GbAGL1 gene in G. barbadense was highly expressed in whole floral bud primordia and the floral organs including ovules and fibres, but the signals were barely observed in vegetative tissues. GbAGL1 expression increased gradually with the ovule developmental stages. Over-expression of GbAGL1 in Arabidopsis caused obvious homeotic alternations in the floral organs, such as early flowering, and an extruded stigma, which were the typical phenotypes of the D-lineage gene family. In addition, a complementation test revealed that GbAGL1 could rescue the phenotypes of the stk mutant. Our study indicated that GbAGL1 was a D-lineage gene that was involved in ovule development and might play key roles in fibres development

Evaluating the Sensitivity of Mycobacterium tuberculosis to Biotin Deprivation Using Regulated Gene Expression

In the search for new drug targets, we evaluated the biotin synthetic pathway of Mycobacterium tuberculosis (Mtb) and constructed an Mtb mutant lacking the biotin biosynthetic enzyme 7,8-diaminopelargonic acid synthase, BioA. In biotin-free synthetic media, ΔbioA did not produce wild-type levels of biotinylated proteins, and therefore did not grow and lost viability. ΔbioA was also unable to establish infection in mice. Conditionally-regulated knockdown strains of Mtb similarly exhibited impaired bacterial growth and viability in vitro and in mice, irrespective of the timing of transcriptional silencing. Biochemical studies further showed that BioA activity has to be reduced by approximately 99% to prevent growth. These studies thus establish that de novo biotin synthesis is essential for Mtb to establish and maintain a chronic infection in a murine model of TB. Moreover, these studies provide an experimental strategy to systematically rank the in vivo value of potential drug targets in Mtb and other pathogens