2,348 research outputs found
4D Lorentz Electron Microscopy Imaging: Magnetic Domain Wall Nucleation, Reversal, and Wave Velocity
Magnetization reversal is an important topic of research in the fields of both basic and applied ferromagnetism. For the study of magnetization reversal dynamics and magnetic domain wall (DW) motion in ferromagnetic thin films, imaging techniques are indispensable. Here, we report 4D imaging of DWs by the out-of-focus Fresnel method in Lorentz ultrafast electron microscopy (UEM), with in situ spatial and temporal resolutions. The temporal change in magnetization, as revealed by changes in image contrast, is clocked using an impulsive optical field to produce structural deformation of the specimen, thus modulating magnetic field components in the specimen plane. Directly visualized are DW nucleation and subsequent annihilation and oscillatory reappearance (periods of 32 and 45 ns) in nickel films on two different substrates. For the case of Ni films on a Ti/Si_(3)N_4 substrate, under conditions of minimum residual external magnetic field, the oscillation is associated with a unique traveling wave train of periodic magnetization reversal. The velocity of DW propagation in this wave train is measured to be 172 m/s with a wavelength of 7.8 μm. The success of this study demonstrates the promise of Lorentz UEM for real-space imaging of spin switching, ferromagnetic resonance, and laser-induced demagnetization in ferromagnetic nanostructures
Nonchaotic Nonlinear Motion Visualized in Complex Nanostructures by Stereographic 4D Electron Microscopy
Direct electron imaging with sufficient time resolution is a powerful tool for visualizing the three-dimensional (3D) mechanical motion and resolving the four-dimensional (4D) trajectories of many different components of a nanomachine, e.g., a NEMS device. Here, we report a nanoscale nonchaotic motion of a nano- and microstructured NiTi shape memory alloy in 4D electron microscopy. A huge amplitude oscillatory mechanical motion following laser heating is observed repetitively, likened to a 3D motion of a conductor’s baton. By time-resolved 4D stereographic reconstruction of the motion, prominent vibrational frequencies (3.0, 3.8, 6.8, and 14.5 MHz) are fully characterized, showing evidence of nonlinear behavior. Moreover, it is found that a stress (fluence)−strain (displacement) profile shows nonlinear elasticity. The observed resonances of the nanostructure are reminiscent of classical molecular quasi-periodic behavior, but here both the amplitude and frequency of the motion are visualized using ultrafast electron microscopy
Exploring a Process Model for Stakeholder Management
This paper expands stakeholder management practice by incorporating concepts
from the issues management process model. Based on Jones and Chase’s issuesprocess
model, this study provides a comprehensive three-step stakeholder
management process: (1) stakeholder identification and analysis, (2) development
and implementation of stakeholder management strategies, and (3) stakeholder
management evaluation. From a practical point of view, the stakeholder identification
step helps organizations picture what types of reactions or attacks will occur in the
near future. In addition, stakeholder analysis allows organizations to enlist salient
stakeholders and offers a practical initiation into stakeholder management. The
criteria for stakeholder identification and analysis in this model can provide practical
guidelines for ongoing brainstorming drills within organizations to determine which
stakeholders should be engaged. Furthermore, an organization’s stakeholder
management strategies are created and selected according to stakeholder
categories on the basis of types and priorities. This cyclical process can motivate
organizations to continue their implementation and evaluation, which will lead to an
effective and efficient issues management process that can result in the construction
of a better society
Atomic-Scale Imaging in Real and Energy Space Developed in Ultrafast Electron Microscopy
In this contribution, we report the development of ultrafast electron microscopy (UEM) with atomic-scale real-, energy-, and Fourier-space resolutions. This second-generation UEM provides images, diffraction patterns, and electron energy spectra, and here we demonstrate its potential with applications for nanostructured materials and organometallic crystals. We clearly resolve the separation between atoms in the direct images and the Bragg spots/Debye−Scherrer rings in diffraction and obtain the electronic structure and elemental energies in the electron energy loss spectra (EELS) and energy filtered transmission electron microscopy (EFTEM)
DECAY FACTOR WITH EXPERIMENTAL VARIABLES IN TWO CIRCULATING FLUIDIZED BED (CFB) RISERS
The effects of the riser inlet velocity, solid mass flux and particle size on the axial solid holdup profile and decay factor were investigated using two circulating fluidized beds (CFBs) with FCC (Geldart A) particles as the bed materials. Based on the experimental results from the two-CFBs, the axial solid holdup in the two CFBs were compared with the correlations of previous studies. Also, an empirical correlation was proposed for decay factor that exhibited a good agreement with experimental data
Real-space observation of short-period cubic lattice of skyrmions in MnGe
Emergent phenomena and functions arising from topological electron-spin
textures in real space or momentum space are attracting growing interest for
new concept of states of matter as well as for possible applications to
spintronics. One such example is a magnetic skyrmion, a topologically stable
nanoscale spin vortex structure characterized by a topological index.
Real-space regular arrays of skyrmions are described by combination of
multi-directional spin helixes. Nanoscale configurations and characteristics of
the two-dimensional skyrmion hexagonal-lattice have been revealed extensively
by real-space observations. Other three-dimensional forms of skyrmion lattices,
such as a cubic-lattice of skyrmions, are also anticipated to exist, yet their
direct observations remain elusive. Here we report real-space observations of
spin configurations of the skyrmion cubic-lattice in MnGe with a very short
period (~3 nm) and hence endowed with the largest skyrmion number density. The
skyrmion lattices parallel to the {100} atomic lattices are directly observed
using Lorentz transmission electron microscopes (Lorentz TEMs). It enables the
first simultaneous observation of magnetic skyrmions and underlying
atomic-lattice fringes. These results indicate the emergence of
skyrmion-antiskyrmion lattice in MnGe, which is a source of emergent
electromagnetic responses and will open a possibility of controlling
few-nanometer scale skyrmion lattices through atomic lattice modulations
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Cellular energy stress induces AMPK-mediated regulation of YAP and the Hippo pathway.
YAP (Yes-associated protein) is a transcription co-activator in the Hippo tumour suppressor pathway and controls cell growth, tissue homeostasis and organ size. YAP is inhibited by the kinase Lats, which phosphorylates YAP to induce its cytoplasmic localization and proteasomal degradation. YAP induces gene expression by binding to the TEAD family transcription factors. Dysregulation of the Hippo-YAP pathway is frequently observed in human cancers. Here we show that cellular energy stress induces YAP phosphorylation, in part due to AMPK-dependent Lats activation, thereby inhibiting YAP activity. Moreover, AMPK directly phosphorylates YAP Ser 94, a residue essential for the interaction with TEAD, thus disrupting the YAP-TEAD interaction. AMPK-induced YAP inhibition can suppress oncogenic transformation of Lats-null cells with high YAP activity. Our study establishes a molecular mechanism and functional significance of AMPK in linking cellular energy status to the Hippo-YAP pathway
A Distributed ADMM Approach to Non-Myopic Path Planning for Multi-Target Tracking
This paper investigates non-myopic path planning of mobile sensors for
multi-target tracking. Such problem has posed a high computational complexity
issue and/or the necessity of high-level decision making. Existing works tackle
these issues by heuristically assigning targets to each sensing agent and
solving the split problem for each agent. However, such heuristic methods
reduce the target estimation performance in the absence of considering the
changes of target state estimation along time. In this work, we detour the
task-assignment problem by reformulating the general non-myopic planning
problem to a distributed optimization problem with respect to targets. By
combining alternating direction method of multipliers (ADMM) and local
trajectory optimization method, we solve the problem and induce consensus
(i.e., high-level decisions) automatically among the targets. In addition, we
propose a modified receding-horizon control (RHC) scheme and edge-cutting
method for efficient real-time operation. The proposed algorithm is validated
through simulations in various scenarios.Comment: Copyright 2019 IEEE. Personal use of this material is permitted.
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Primary segmental volvulus of the ileum mimicking meconium plug syndrome
Primary segmental volvulus (PSV) of the ileum in neonate occurs rarely but shows an aggressive clinical course. Thus, early diagnosis is important to prevent necrosis and perforation of the intestine. We report a case of PSV of the ileum in a 2-day-old female neonate whose clinical features and radiologic findings appeared to be meconium plug syndrome
Rag GTPases are cardioprotective by regulating lysosomal function.
The Rag family proteins are Ras-like small GTPases that have a critical role in amino-acid-stimulated mTORC1 activation by recruiting mTORC1 to lysosome. Despite progress in the mechanistic understanding of Rag GTPases in mTORC1 activation, little is known about the physiological function of Rag GTPases in vivo. Here we show that loss of RagA and RagB (RagA/B) in cardiomyocytes results in hypertrophic cardiomyopathy and phenocopies lysosomal storage diseases, although mTORC1 activity is not substantially impaired in vivo. We demonstrate that despite upregulation of lysosomal protein expression by constitutive activation of the transcription factor EB (TFEB) in RagA/B knockout mouse embryonic fibroblasts, lysosomal acidification is compromised owing to decreased v-ATPase level in the lysosome fraction. Our study uncovers RagA/B GTPases as key regulators of lysosomal function and cardiac protection
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