Disorder-induced Anderson localization usually causes conducting materials to become insulating at low temperature. Graphene is a notable exception. But by increasing the carrier density in one ...graphene layer, a metal-insulator transition can be induced in an isolated second layer stacked above it.
—
A system for detecting the clamping point of a manipulator tip based on the probe of an atomic-force microscope operating in the hybrid mode was upgraded. The upgrading of the detection system made ...it possible not only to obtain topographic images of surfaces in this mode with vertical noises smaller than 10 nm, but also to use this manipulator to move microdroplets over the surface of a substrate. A method was proposed and implemented for moving nanowires using a fluid flow created by the tip of an atomic-force microscope.
Quasi-periodic pulsations (QPPs) are intrinsically connected to the mechanism of solar flares. They are regularly observed in the impulsive phase of flares since the 1970s. In the past years, the ...studies of QPPs regained interest with the advent of a new generation of soft X-ray/extreme ultraviolet radiometers that pave the way for statistical surveys. Since the amplitude of QPPs in these wavelengths is rather small, detecting them implies that the overall trend of the time series needs to be removed before applying any Fourier or wavelet transform. This detrending process is known to produce artificial detection of periods that must then be distinguished from real ones. In this paper, we propose a set of criteria to help identify real periods and discard artifacts. We apply these criteria to data taken by the
Extreme Ultraviolet Variability Experiment
(EVE)/ESP onboard the
Solar Dynamics Observatory
(SDO) and the
Large Yield Radiometer
(LYRA) onboard the
PRoject for On-Board Autonomy 2
(PROBA2) to search for QPPs in flares stronger than M5.0 that occurred during Solar Cycle 24.
Context.
The Association of Spacecraft for Polarimetric and Imaging Investigation of the Corona of the Sun (ASPIICS) is a novel externally occulted solar coronagraph that will be launched on board ...the Project for On-Board Autonomy (PROBA-3) mission in 2023. The external occulter will be placed on the first satellite ∼150 m ahead of the second satellite, which will carry an optical instrument. During 6 hours per orbit, the satellites will fly in a precise formation and will constitute a giant externally occulted coronagraph. The large distance between the external occulter and the primary objective will allow observations of the white-light solar corona starting from extremely low heights of ∼1.1
R
⊙
.
Aims.
Developing and testing of algorithms for the scientific image processing requires understanding of all the optics-related and detector-related effects of the coronagraph, development of appropriate physical and numerical models, and preparation of simulated images that include all these effects. At the same time, an analysis of the simulated data gives valuable information about the performance of the instrument, the suitable observation regime, and the amount of telemetry.
Methods.
We used available physical models of the instrument and implemented them as a software to generate simulated data. We analyzed intermediate and complete simulated images to obtain a better understanding of the performance of ASPIICS, in particular, to predict its photometric sensitivity, effect of noise, suitable exposure times, etc.
Results.
The proposed models and algorithms are used not only to create the simulated data, but also to form the basis for the scientific processing algorithms to be applied during on-ground ASPIICS data processing. We discuss the possible effect of noise and the uncertainty of the calibration factors on the accuracy of final data, and propose suitable exposure times.
We present an overview of the factors as well as post processing tools allowing optimization of magnetic softness and GMI effect of rapidly quenched materials: microwires and ribbons. Generally, low ...coercivity and high GMI effect have been observed in as-prepared Co-rich compositions. Annealing at adequate conditions can be very effective for manipulation of the magnetic properties and GMI effect of amorphous and nanocrystalline rapidly quenched materials. After annealing of Co-rich compositions, we can observe transformation of inclined hysteresis loops to rectangular. However, at certain annealing conditions GMI effect can be improved. Using stress-annealing, GMI effect of both Fe-rich and Co-rich microwires as well as of amorphous ribbons can be improved. On the other hand, in Fe-rich FeCuNbSiB microwires after appropriate annealing we observed considerable magnetic softening and GMI effect enhancement. The other promising post-processing allowing GMI effect optimization is Joule heating.
Display omitted
•Trends in optimization of GMI effect in amorphous and nanocrystalline materials.•Magnetic softening of Fe-rich microwires after stress-annealing or nanocrystallization.•Improvement of GMI effect after Joule heating of Co-rich microwires.•Optimization of GMI effect after post-processing of Co-rich amorphous ribbons.•Improvement of GMI effect after annealing and stress-annealing of Co-rich microwires.
Control over the quantization of electrons in quantum wells is at the heart of the functioning of modern advanced electronics; high electron mobility transistors, semiconductor and Capasso terahertz ...lasers, and many others. However, this avenue has not been explored in the case of 2D materials. Here we apply this concept to van der Waals heterostructures using the thickness of exfoliated crystals to control the quantum well dimensions in few-layer semiconductor InSe. This approach realizes precise control over the energy of the subbands and their uniformity guarantees extremely high quality electronic transport in these systems. Using tunnelling and light emitting devices, we reveal the full subband structure by studying resonance features in the tunnelling current, photoabsorption and light emission spectra. In the future, these systems could enable development of elementary blocks for atomically thin infrared and THz light sources based on intersubband optical transitions in few-layer van der Waals materials.
In the current study, we have succeeded to fabricate Co2FeSi Heusler alloy glass-covered microwires with magnetic core nucleus diameter d = 4.36 µm and total diameter D = 17.55 µm, with high Curie ...temperature (Tc>1100 K) and well-defined magnetic anisotropy for high temperature spintronic devices application. The magnetic properties of as-prepared and annealed at different temperature (873 K, 973 K and 1073 K for 1 h) of Co2FeSi Heusler alloy glass-covered microwires have been investigated. Strong dependence of the magnetic properties on the annealing conditions has been indicated. Anomalous magnetic behavior for annealed samples at 873 K and 973 K has been found and structural properties of such samples have been analyzed. Critical temperatures 155 K and 250 K have been detected for annealed samples at 873 K and 973 K, respectively, where the behavior of M-H loops and coercivity changed. Below the critical point the M-H curve shows “kink or wasp-waisted” magnetic behavior and complex magnetic reversal mechanism is supposed. The anomalous magnetic behavior is due to the martensitic phases induced by annealing conditions below the room temperature. This unusual magnetization behavior provides opportunities to understand the phenomena of different types of magnetic domain structures in the preferred crystallographically oriented Co2FeSi Heusler alloy glass-coated micro-wires, essentially helpful for designing the devices based on magnetization switching.
•Production of Co2FeSi Heusler alloy glass-coated microwires with high Curie temperature.•Strong dependence of the magnetic properties Co2FeSi Heusler alloy glass-coated microwires on the annealing conditions.•Anomalous magnetic behavior below the room temperature for Co2FeSi glass-coated microwires annealed at 873 K and 973 K.•Critical temperatures where changes in the magnetic and structure phases appear were detected for annealed samples.•Suitability of Co2FeSi microwires for the design of devices based on magnetization switching.
Abstract
Arch-like loop structures filled with million Kelvin hot plasma form the building blocks of the quiet-Sun corona. Both high-resolution observations and magnetoconvection simulations show the ...ubiquitous presence of magnetic fields on the solar surface on small spatial scales of ∼100 km. However, the question of how exactly these quiet-Sun coronal loops originate from the photosphere and how the magnetic energy from the surface is channeled to heat the overlying atmosphere is a long-standing puzzle. Here we report high-resolution photospheric magnetic field and coronal data acquired during the second science perihelion of Solar Orbiter that reveal a highly dynamic magnetic landscape underlying the observed quiet-Sun corona. We found that coronal loops often connect to surface regions that harbor fleeting weaker, mixed-polarity magnetic field patches structured on small spatial scales, and that coronal disturbances could emerge from these areas. We suggest that weaker magnetic fields with fluxes as low as 10
15
Mx and/or those that evolve on timescales less than 5 minutes are crucial to understanding the coronal structuring and dynamics.
As-prepared and annealed Heusler-type NiMnGa glass-covered microwires present considerable dependence of magnetization on magnetic field values attributed to the magnetic and atomic disorder. We ...observed that annealing conditions strongly affect structure, temperature dependence of magnetization and Curie temperature of microwires. After annealing a magnetic phase transition is observed at about 270–300 K which is beneficial for magnetic solid state refrigeration. Exchange bias effect, enhanced coercivity values at low temperature and features that can be attributed to coexistence of two magnetic phases are observed after long annealing of NiMnGa glass-covered microwires.
Display omitted
•Tunability of magnetic properties of Heusler-type microwires by annealing.•Magnetic phase transition near room temperature beneficial for magnetic solid state refrigeration.•An exchange bias of about 20 Oe at 5 K in annealed NiMnGa microwires.•An enhanced coercivity at low temperatures in annealed NiMnGa microwires.
One of the most important priorities for all countries with property beyond the Arctic Circle and territories located in permafrost areas is the development of special construction technologies and ...systems. The required conditions are met by insulation systems based on seamless insulation shells made of polyethylene foam. The study of the strength and performance properties of polyethylene foam and its combinability was carried out according to standard methods and using the methods of experimental design and the analytical processing of the results. The change in material properties at negative temperatures was determined based on the results of climatic tests, followed by an evaluation of creep under load. The evaluation of the effectiveness of the design solutions was carried out using special computer programs. It was found that the performance characteristics of products made of polyethylene foam (rolls, mats) meet the requirements for insulation materials used at temperatures down to −60 °C. The resulting material is moderately combustible, which must be taken into account when developing recommendations for its use in insulation systems. A nomogram has been developed that makes it possible to predict the properties of a material and solve formulation problems. Insulation systems were developed, and a visualisation of the thermal fields of the insulation systems of the external walls and ceilings of a building was carried out.
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