The manipulation of spin textures with electric currents is an important challenge in the field of spintronics. Many attempts have been made to electrically drive magnetic domain walls in ...ferromagnets, yet the necessary current density remains quite high (~10(7) A cm(-2)). A recent neutron study combining Hall effect measurements has shown that an ultralow current density of J~10(2) A cm(-2) can trigger the rotational and translational motion of the skyrmion lattice in MnSi, a helimagnet, within a narrow temperature range. Raising the temperature range in which skyrmions are stable and reducing the current required to drive them are therefore desirable objectives. Here we demonstrate near-room-temperature motion of skyrmions driven by electrical currents in a microdevice composed of the helimagnet FeGe, by using in-situ Lorentz transmission electron microscopy. The rotational and translational motions of skyrmion crystal begin under critical current densities far below 100 A cm(-2).
The spacecraft Geotail surveyed the near‐Earth plasma sheet from XGSM = −10 to −31 RE and YGSM = −20 to +20 RE during the period from 1994 to 2022. It observed 243 magnetic reconnection events and ...785 tailward flow events under various solar wind conditions during plasma sheet residence time of over 23,000 hr. Magnetic reconnections associated with the onset of magnetospheric substorms occur mostly in the range XGSM = −23 to −31 RE. When the solar wind is intense and high substorm activities continue, magnetic reconnection can occur closer to the Earth. The YGSM locations of magnetic reconnections depend on the solar wind conditions and on previous substorm activity. Under normal solar wind conditions, magnetic reconnection occurs preferentially in the pre‐midnight plasma sheet. Under conditions with intense (weak) solar wind energy input, however, magnetic reconnection can occur in the post‐midnight (duskside) plasma sheet. Continuous substorm activity tends to shift the magnetic reconnection site duskward. The plasma sheet thinning proceeds faster under intense solar wind conditions, and the loading process that provides the preconditions for magnetic reconnection becomes shorter. When magnetic flux piles up during a prolonged period with a strongly northward‐oriented interplanetary magnetic field (IMF) Bz, the time necessary to provide the preconditions for magnetic reconnection becomes longer. Although the solar wind conditions are the primary factors that control the location and timing of magnetic reconnections, the plasma sheet conditions created by preceding substorm activity or the strongly northward IMF Bz can modify the solar wind control.
Key Points
Under normal solar wind conditions, magnetic reconnection in association with the onset of a substorm occurs in the pre‐midnight plasma sheet at XGSM = −23 to −31 RE
Intense (weak) solar wind energy input can shift the magnetic reconnection site toward the dawnside (duskside) plasma sheet
Plasma sheet thinning proceeds faster under intense solar wind energy input, although conditions in the plasma sheet can modify the solar wind control
In SrCoO3-delta (SC)-based mixed conductors, cation substitution is necessary to stabilize the high-oxygen permeable perovskite structure, but the dose of the substitution should be minimized to ...avoid degradation of permeability. To clarify the relation between the substitutional cation and the perovskite stability of the mixed conductor, SC-based oxides, (La0.1Sr0.9)CoO3-delta and Sr(Co0.9X0.1)O3-delta where X was Ni, Cu, Zn, Cr, Fe, Al, Ga, In, Ce, Ti, Zr, Sn, V and Nb, were studied. The appearance of the low oxygen permeable 2H-BaNiO3-type SrCoO2.52 phase during the preparation of the powder samples or post-annealing in oxygen was investigated and the tendency to transform to the hexagonal phase was evaluated. The sequence of the perovskite stability upon the substituting cation for SC was
Understanding the cooling effect of recent volcanoes is of particular interest in the context of the post-2000 slowing of the rate of global warming. Satellite observations of aerosol optical depth ...above 15 km have demonstrated that small-magnitude volcanic eruptions substantially perturb incoming solar radiation. Here we use lidar, Aerosol Robotic Network, and balloon-borne observations to provide evidence that currently available satellite databases neglect substantial amounts of volcanic aerosol between the tropopause and 15 km at middle to high latitudes and therefore underestimate total radiative forcing resulting from the recent eruptions. Incorporating these estimates into a simple climate model, we determine the global volcanic aerosol forcing since 2000 to be 0.19 +/- 0.09W/sq m. This translates into an estimated global cooling of 0.05 to 0.12 C. We conclude that recent volcanic events are responsible for more post-2000 cooling than is implied by satellite databases that neglect volcanic aerosol effects below 15 km.
Simulation studies of the Earth's radiation belts and ring current are very useful in understanding the acceleration, transport, and loss of energetic particles. Recently, the Comprehensive Ring ...Current Model (CRCM) and the Radiation Belt Environment (RBE) model were merged to form a Comprehensive Inner Magnetosphere-Ionosphere (CIMI) model. CIMI solves for many essential quantities in the inner magnetosphere, including ion and electron distributions in the ring current and radiation belts, plasmaspheric density, Region 2 currents, convection potential, and precipitation in the ionosphere. It incorporates whistler mode chorus and hiss wave diffusion of energetic electrons in energy, pitch angle, and cross terms. CIMI thus represents a comprehensive model that considers the effects of the ring current and plasmasphere on the radiation belts. We have performed a CIMI simulation for the storm on 5-9 April 2010 and then compared our results with data from the Two Wide-angle Imaging Neutral-atom Spectrometers and Akebono satellites. We identify the dominant energization and loss processes for the ring current and radiation belts. We find that the interactions with the whistler mode chorus waves are the main cause of the flux increase of MeV electrons during the recovery phase of this particular storm. When a self-consistent electric field from the CRCM is used, the enhancement of MeV electrons is higher than when an empirical convection model is applied. We also demonstrate how CIMI can be a powerful tool for analyzing and interpreting data from the new Van Allen Probes mission.
Abstract
It is important to measure and ensure the thermal insulation performance of newly built or existing residential buildings to promote energy-efficient and comfortable housing throughout ...society. Among various in-situ measurement methods for this purpose, this study focuses on the probe insertion method, in which a borescope and a temperature sensor are inserted through a tiny hole drilled in the interior side of the wall to visually inspect and measure the temperature distribution inside the wall. In this method, the temperature sensor itself can act as a thermal bridge, which causes a deviation from the original temperature distribution inside the insulation material. In this paper, based on physical considerations and heat conduction simulation, we introduce two dominant dimensionless numbers that determine the temperature deviation: the Biot number and the newly defined
N
c
value. In addition, we draw schematic charts to find the temperature deviation from the introduced dimensionless numbers, and suggest a procedure to determine the required specifications of a temperature sensor that can accurately measure the temperature distribution.
This study investigates the role of aerosol microphysics in stratospheric sulfate aerosol changes after the 1991 Mount Pinatubo eruption using an atmospheric general circulation model that is coupled ...interactively with a chemistry module and a modal aerosol microphysical module with three modes. Our model can reproduce the global mean stratospheric aerosol optical depth (SAOD) observed by the Stratospheric Aerosol and Gas Experiment (SAGE) II during June 1991 to January 1993. The model underestimates the observed SAOD before the eruption and after January 1993. The model also underestimates the integrated backscatter coefficient observed by ground‐based lidar at Tsukuba, Naha, and Lauder. The modeled effective radius becomes larger (about 0.5 μm) and agrees with the balloon‐borne measurements at Laramie, Wyoming (41°N, 105°W). We further investigate effects of the inclusion of evaporation along with the condensation processes and the inclusion of van der Waals and viscous forces in the coagulation processes. The inclusion of evaporation along with the condensation processes reduces the global mean effective radius by up to 0.04 μm and increases the global burden of stratospheric sulfate aerosols (about 15% in late 1993). The inclusion of van der Waals and viscous forces in the coagulation processes increases the global mean effective radius by up to 0.06–0.07 μm and decreases the global burden (15–30% in late 1993). The effects of van der Waals and viscous forces differ between two schemes. However, we do not conclude which simulation is superior because all simulations fall within error bars.
Key Points
Microphysical model suggests that evaporation shrinks sulfate and increases the global burden (15%)
Van der Waals and viscous forces enhance coagulation and decrease the global sulfate burden by 30%
None of the simulations are superior as they all fall within error bars
In many phenomena of biological systems, not a majority, but a minority of cells act on the entire multicellular system causing drastic changes in the system properties. To understand the mechanisms ...underlying such phenomena, it is essential to observe the spatiotemporal dynamics of a huge population of cells at sub-cellular resolution, which is difficult with conventional tools such as microscopy and flow cytometry. Here, we describe an imaging system named AMATERAS that enables optical imaging with an over-one-centimeter field-of-view and a-few-micrometer spatial resolution. This trans-scale-scope has a simple configuration, composed of a low-power lens for machine vision and a hundred-megapixel image sensor. We demonstrated its high cell-throughput, capable of simultaneously observing more than one million cells. We applied it to dynamic imaging of calcium ions in HeLa cells and cyclic-adenosine-monophosphate in Dictyostelium discoideum, and successfully detected less than 0.01% of rare cells and observed multicellular events induced by these cells.
Fluorescence resonance energy transfer (FRET) technology has been used to develop genetically encoded fluorescent indicators for various cellular functions. Although most indicators have cyan- and ...yellow-emitting fluorescent proteins (CFP and YFP) as FRET donor and acceptor, their poor dynamic range often prevents detection of subtle but significant signals. Here, we optimized the relative orientation of the two chromophores in the Ca2+indicator, yellow cameleon (YC), by fusing YFP at different angles. We generated circularly permuted YFPs (cpYFPs) that showed efficient maturation and acid stability. One of the cpYFPs incorporated in YC absorbs a great amount of excited energy from CFP in its Ca2+-saturated form, thereby increasing the Ca2+-dependent change in the ratio of YFP/CFP by nearly 600%. Both in cultured cells and in the nervous system of transgenic mice, the new YC enables visualization of subcellular Ca2+dynamics with better spatial and temporal resolution than before. Our study provides an important guide for the development and improvement of indicators using GFP-based FRET.
We performed a preliminary study of neutron resonance absorption imaging to investigate the spatial distribution of constituent elements in borosilicate glasses containing simulated high-level ...radioactive waste, in which elemental inhomogeneities affect the physical and chemical stabilities of the glass. Dips generated by the resonance absorptions of Rh, Pd, Na, Gd, Cs, and Sm were observed in the neutron transmission spectra of the glass samples. The spatial distributions of these elements were obtained from the neutron transmission images at the resonance energies. The distributions of Rh and Pd visualized the sedimentation of these platinum group elements. In contrast, the lanthanides (Gd and Sm) and Cs were uniformly dispersed. These results show that neutron resonance absorption imaging is a promising tool for characterizing borosilicate glasses and investigating the vitrification mechanism of high-level radioactive waste.
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