Lightning discharges in association with mesospheric optical phenomena in Japan and their effect on the lower ionosphere

A quantitative and statistical analysis was performed using data from coordinated measurements consisting of ELF waves, VLF subionospheric disturbances and lightning discharges associated with transient luminous events(TLEs). These TLEs(sprites and elves) were observed during winter lightning storms over the Sea of Japan in the winter of 1998/99. A clear, straightforward relationship was found between the charge moment of the parent discharge, calculated from ELF(f<15Hz) transients, and the ionospheric disturbances, with a correlation coefficient of 0.97 independent of the type of TLEs; this suggests significant atmosphere-mesosphere-ionosphere coupling and implies that a large quasi-electrostatic(QE) field change occurring above lightning discharges with TLEs plays a significant role in modifying the electrical properties of the lower ionosphere. Sprites tend to be associated with large ionospheric disturbancs(-13～+ 4.6dB, compared with the unperturbed waves) and a large charge moment(260-875Ckm), whereas a relatively large lightning peak current(+223～+ 470kA,)(or a slow-tail amplitude) leading to a strong electromagnetic pulse(EMP) but with a rather small ionospheric disturbances seems to be necessary to initiate elves

A Signaling Principle for the Specification of the Germ Cell Lineage in Mice

SummarySpecification of the germ cell lineage is vital to development and heredity. In mice, the germ cell fate is induced in pluripotent epiblast cells by signaling molecules, yet the underlying mechanism remains unknown. Here we demonstrate that germ cell fate in the epiblast is a direct consequence of Bmp4 signaling from the extraembryonic ectoderm (ExE), which is antagonized by the anterior visceral endoderm (AVE). Strikingly, Bmp8b from the ExE restricts AVE development, thereby contributing to Bmp4 signaling. Furthermore, Wnt3 in the epiblast ensures its responsiveness to Bmp4. Serum-free, defined cultures revealed that, in response to Bmp4, competent epiblast cells uniformly expressed key transcriptional regulators Blimp1 and Prdm14 and acquired germ-cell properties, including genome-wide epigenetic reprogramming, in an orderly fashion. Notably, the induced cells contributed to both spermatogenesis and fertility of offspring. By identifying a signaling principle in germ cell specification, our study establishes a robust strategy for reconstituting the mammalian germ cell lineage in vitro

Chiral Monolayers with Achiral Tetrapod Molecules on Highly Oriented Pyrolytic Graphite

金沢大学理工研究域物質化学系The self-assembly of organic molecules at the surface of highly oriented pyrolytic graphite (HOPG) is a promising process for constructing molecular-scale architectures. However, selectable organic molecules are generally restricted to two-dimensional molecules with planar Ï-conjugated structures and alkyl chains. We herein present the formation of self-assembled monolayers of tetrakis(4-ethynylphenyl)methane (TEPM) having a three-dimensional (3D) tetrapod geometry on HOPG, which was achieved by utilizing a simple spin-coating method. The arrangements of TEPM molecules in the monolayers were investigated using frequency-modulation atomic force microscopy (FM-AFM). The resulting subnanometer-resolution FM-AFM images revealed that the TEPM molecules formed linear rows with a periodicity of 0.85 nm oriented in a parallel configuration but with two alternating intervals of 0.7 and 1.0 nm. Moreover, the TEPM monolayers were classified into two chiral types with a relationship of mutual mirror-image symmetry, according to the observed molecular arrangements. Our results demonstrate the capability of TEPM molecules to act as 3D building blocks for the design of molecular-scale architectures at interfaces. Copyright © 2020 American Chemical Society

Possible precursor to the March 11, 2011, Japan earthquake: ionospheric perturbations as seen by subionospheric very low frequency/low frequency propagation

This study reports on a possible very low frequency/low frequency (VLF/LF) subionospheric precursor to a recent earthquake in Japan. As the epicenter of this large Japanese earthquake on March 11, 2011, was located just on the great-circle path from one of our VLF/LF network stations (Chofu) to the NLK US transmitter, we examined the propagation characteristics mainly associated with the signals from the NLK transmitter, as observed at three of the stations in Japan (Chofu, Kasugai and Kochi). On March 5 and 6, 2011, a remarkable anomaly was found on the path from NLK to Chofu, which is highly likely to have been a precursor to this earthquake. The anomaly in the night-time average amplitude at Chofu was characterized by a serious decrease in the signal that exceeded −4v (v: standard deviations). The anomaly was found on the same days on the other propagation paths (from NLK to both Kasugai and Kochi), although it was less enhanced. Finally, this propagation anomaly is extensively discussed with respect to the geomagnetic activity, and we also compare this anomaly with the properties related to the former 2004 Sumatra earthquake that had nearly the same magnitude as this March 11, 2011, earthquake.

The Ionospheric Precursor to the 2011 March 11 Earthquake Based upon Observations Obtained from the Japan-Pacific Subionospheric VLF/LF Network

By using network observation of subionospheric VLF (very low frequency)/LF (low frequency) signals in Japan and in Russia, we have found a significant ionospheric perturbation prior to the recent 2011 March 11 Japan earthquake (EQ) which occurred at sea proximate to the Tohoku area on the main island (Honshu) of Japan was an exceptionally huge plate-type EQ. A remarkable anomaly (with a decrease in the nighttime amplitude and also with enhancement in dispersion) was detected on March 5 and 6 along the propagation path from the NLK (Seattle, USA) transmitter to Chofu (together with Kochi and Kasugai). We also have observed the corresponding VLF anomaly during a prolonged period of March 1 - 6, with minima in the nighttime amplitude on March 3 and 4 along the path from JJI (Miyazaki, Kyushu) to Kamchatka, Russia. This ionospheric perturbation has been discussed extensively with respect to its reliability. (1) How abnormal is this VLF/LF propagation anomaly? (2) What was the temporal evolution of terminator times? (3) Were there any solar-terrestrial effects (especially the effect from geomagnetic storms) on the VLF/LF propagation anomaly? (4) The effect of any other EQs and foreshock activities on the VLF/LF anomaly? (5) Were there any correlations with other related phenomena? Finally, (6) are there any other examples of a VLF/LF propagation anomaly for oceanic EQs? We then compared the temporal properties of ionospheric perturbations for this EQ with those of a huge number of inland EQs and compared the corresponding spatial scale with the former result of the same oceanic 2004 Sumatra EQ with nearly the same magnitude. Finally, the generation mechanism of those seismo-ionospheric perturbations is briefly discussed

Ionospheric perturbations associated with two huge earthquakes in Japan, using principal component analysis for multiple subionospheric VLF/LF propagation paths

The presence of ionospheric perturbations in possible association with two huge earthquakes (Noto-hanto peninsula and Niigata-chuetu-oki earthquakes) in 2007 was studied on the basis of a conventional statistical study for a particular propagation path from the JJI transmitter in Miyazaki, Kyushu, to Moshiri in Hokkaido. This is based on automatic routine-based signal processing, in which the trend as the average nighttime amplitude is significantly decreased, with almost simultaneous significant enhancement in the night-time fluctuation as the night-time integration of negative fluctuation from the average. It is, however, shown that this routine-based signal analysis sometime suffers from artificial (or man-made) effects. Thus, in this study, we propose an additional use of principal component analysis (PCA) for simultaneous observation of a few VLF/LF propagation paths. With the application of this PCA method to multi-path data, the artificial effects can be reasonably removed, and also only the geophysical effects associated with earthquakes are detected, by focusing mainly on the third principal component. The satisfactory separation of the principal components is made possible by pre-analysis of the VLF data (extraction from the raw data of the average over a whole year). This PCA method enables us to identify the seismogenic effects in association with earthquakes with smaller magnitudes, down to M 5.5 or M 5.0.