138 research outputs found
Interaction Effect of Social Isolation and High Dose Corticosteroid on Neurogenesis and Emotional Behavior
published_or_final_versio
Theory of current-driven motion of Skyrmions and spirals in helical magnets
We study theoretically the dynamics of the spin textures, i.e., Skyrmion
crystal (SkX) and spiral structure (SS), in two-dimensional helical magnets
under external current. By numerically solving the Landau-Lifshitz-Gilbert
equation, it is found that (i) the critical current density of the motion is
much lower for SkX compared with SS in agreement with the recent experiment,
(ii) there is no intrinsic pinning effect for SkX and the deformation of the
internal structure of Skyrmion reduces the pinning effect dramatically, (iii)
the Bragg intensity of SkX shows strong time-dependence as can be observed by
neutron scattering experiment.Comment: 4 pages, 3 figure
Field-free deterministic ultra fast creation of skyrmions by spin orbit torques
Magnetic skyrmions are currently the most promising option to realize
current-driven magnetic shift registers. A variety of concepts to create
skyrmions were proposed and demonstrated. However, none of the reported
experiments show controlled creation of single skyrmions using integrated
designs. Here, we demonstrate that skyrmions can be generated deterministically
on subnanosecond timescales in magnetic racetracks at artificial or natural
defects using spin orbit torque (SOT) pulses. The mechanism is largely similar
to SOT-induced switching of uniformly magnetized elements, but due to the
effect of the Dzyaloshinskii-Moriya interaction (DMI), external fields are not
required. Our observations provide a simple and reliable means for skyrmion
writing that can be readily integrated into racetrack devices
Spectral quantification of nonlinear behaviour of the nearshore seabed and correlations with potential forcings at Duck, N.C., U.S.A
Local bathymetric quasi-periodic patterns of oscillation are identified from
monthly profile surveys taken at two shore-perpendicular transects at the USACE
field research facility in Duck, North Carolina, USA, spanning 24.5 years and
covering the swash and surf zones. The chosen transects are the two furthest
(north and south) from the pier located at the study site. Research at Duck has
traditionally focused on one or more of these transects as the effects of the
pier are least at these locations. The patterns are identified using singular
spectrum analysis (SSA). Possible correlations with potential forcing
mechanisms are discussed by 1) doing an SSA with same parameter settings to
independently identify the quasi-periodic cycles embedded within three
potentially linked sequences: monthly wave heights (MWH), monthly mean water
levels (MWL) and the large scale atmospheric index known as the North Atlantic
Oscillation (NAO) and 2) comparing the patterns within MWH, MWL and NAO to the
local bathymetric patterns. The results agree well with previous patterns
identified using wavelets and confirm the highly nonstationary behaviour of
beach levels at Duck; the discussion of potential correlations with
hydrodynamic and atmospheric phenomena is a new contribution. The study is then
extended to all measured bathymetric profiles, covering an area of 1100m
(alongshore) by 440m (cross-shore), to 1) analyse linear correlations between
the bathymetry and the potential forcings using multivariate empirical
orthogonal functions (MEOF) and linear correlation analysis and 2) identify
which collective quasi-periodic bathymetric patterns are correlated with those
within MWH, MWL or NAO, based on a (nonlinear) multichannel singular spectrum
analysis (MSSA). (...continued in submitted paper)Comment: 50 pages, 3 tables, 8 figure
Integrating transposable elements in the 3D genome
Chromosome organisation is increasingly recognised as an essential component of genome regulation, cell fate and cell health. Within the realm of transposable elements (TEs) however, the spatial information of how genomes are folded is still only rarely integrated in experimental studies or accounted for in modelling. Whilst polymer physics is recognised as an important tool to understand the mechanisms of genome folding, in this commentary we discuss its potential applicability to aspects of TE biology. Based on recent works on the relationship between genome organisation and TE integration, we argue that existing polymer models may be extended to create a predictive framework for the study of TE integration patterns. We suggest that these models may offer orthogonal and generic insights into the integration profiles (or "topography") of TEs across organisms. In addition, we provide simple polymer physics arguments and preliminary molecular dynamics simulations of TEs inserting into heterogeneously flexible polymers. By considering this simple model, we show how polymer folding and local flexibility may generically affect TE integration patterns. The preliminary discussion reported in this commentary is aimed to lay the foundations for a large-scale analysis of TE integration dynamics and topography as a function of the three-dimensional host genome
Electric-field control of magnetic domain wall motion and local magnetization reversal
Spintronic devices currently rely on magnetic switching or controlled motion
of domain walls by an external magnetic field or spin-polarized current.
Achieving the same degree of magnetic controllability using an electric field
has potential advantages including enhanced functionality and low power
consumption. Here, we report on an approach to electrically control local
magnetic properties, including the writing and erasure of regular ferromagnetic
domain patterns and the motion of magnetic domain walls, in multiferroic
CoFe-BaTiO3 heterostructures. Our method is based on recurrent strain transfer
from ferroelastic domains in ferroelectric media to continuous magnetostrictive
films with negligible magnetocrystalline anisotropy. Optical polarization
microscopy of both ferromagnetic and ferroelectric domain structures reveals
that domain correlations and strong inter-ferroic domain wall pinning persist
in an applied electric field. This leads to an unprecedented electric
controllability over the ferromagnetic microstructure, an accomplishment that
produces giant magnetoelectric coupling effects and opens the way to
multiferroic spintronic devices.Comment: 6 pages, 4 figure
Resonant amplification of vortex-core oscillations by coherent magnetic-field pulses
Vortex structures in soft magnetic nanodisks are highly attractive due to their scientific beauty and potential technological applications. Here, we experimentally demonstrated the resonant amplification of vortex oscillations by application of simple coherent field pulses tuned to optimal width and time intervals. In order to investigate vortex excitations on the sub-ns time scale, we employed state-of-the-art time-resolved full-field soft X-ray microscopy of 70 ps temporal and 25 nm lateral resolution. We found that, due to the resonant enhancement of the vortex gyration motion, the signal input power can be significantly reduced to similar to 1 Oe in field strength, while increasing signal gains, by increasing the number of the optimal field pulses. We identified the origin of this behavior as the forced resonant amplification of vortex gyration. This work represents an important milestone towards the potential implementation of vortex oscillations in future magnetic vortex devices.open4
Suppression of Stochastic Domain Wall Pinning Through Control of Gilbert Damping
Finite temperature micromagnetic simulations were used to investigate the magnetisation structure, propagation dynamics and stochastic pinning of domain walls in rare earth-doped Ni80Fe20 nanowires. We first show how the increase of the Gilbert damping, caused by the inclusion rare-earth dopants such as holmium, acts to suppress Walker breakdown phenomena. This allows domain walls to maintain consistent magnetisation structures during propagation. We then employ finite temperature simulations to probe how this affects the stochastic pinning of domain walls at notch-shaped artificial defect sites. Our results indicate that the addition of even a few percent of holmium allows domain walls to pin with consistent and well-defined magnetisation configurations, thus suppressing dynamically-induced stochastic pinning/depinning phenomena. Together, these results demonstrate a powerful, materials science-based solution to the problems of stochastic domain wall pinning in soft ferromagnetic nanowires
Pharmacological Properties and Physiological Function of a P2X-Like Current in Single Proximal Tubule Cells Isolated from Frog Kidney
Although previous studies have provided evidence for the expression of P2X receptors in renal proximal tubule, only one cell line study has provided functional evidence. The current study investigated the pharmacological properties and physiological role of native P2X-like currents in single frog proximal tubule cells using the whole-cell patch-clamp technique. Extracellular ATP activated a cation conductance (P2Xf) that was also Ca2+-permeable. The agonist sequence for activation was ATP = αβ-MeATP > BzATP = 2-MeSATP, and P2Xf was inhibited by suramin, PPADS and TNP-ATP. Activation of P2Xf attenuated the rundown of a quinidine-sensitive K+ conductance, suggesting that P2Xf plays a role in K+ channel regulation. In addition, ATP/ADP apyrase and inhibitors of P2Xf inhibited regulatory volume decrease (RVD). These data are consistent with the presence of a P2X receptor that plays a role in the regulation of cell volume and K+ channels in frog renal proximal tubule cells
A 160-kilobit molecular electronic memory patterned at 10^(11) bits per square centimetre
The primary metric for gauging progress in the various semiconductor integrated circuit technologies is the spacing, or pitch, between the most closely spaced wires within a dynamic random access memory (DRAM) circuit. Modern DRAM circuits have 140nm pitch wires and a memory cell size of 0.0408 μm^2. Improving integrated circuit technology will require that these dimensions decrease over time. However, at present a large fraction of the patterning and materials requirements that we expect
to need for the construction of new integrated circuit technologies in 2013 have ‘no known solution’. Promising ingredients for advances in integrated circuit technology are nanowires, molecular electronics and defect-tolerant architectures, as demonstrated by reports of single devices and small circuits. Methods of extending these approaches to large-scale, high-density circuitry are largely undeveloped. Here we describe a 160,000-bit molecular electronic memory circuit, fabricated at a density of 10^(11) bits cm^(-2) (pitch 33 nm; memory cell size 0.0011 mm^2), that is, roughly analogous to the dimensions of a DRAM circuit projected to be available by 2020. A monolayer of bistable, [2]rotaxane molecules 10 served as the data storage elements. Although the circuit has large numbers of defects, those defects could be readily identified through electronic testing and isolated using software coding. The working bits were then configured to form a fully functional random access memory circuit for storing and retrieving information
- …