Context.
The heating of the solar corona by small heating events requires an increasing number of such events at progressively smaller scales, with the bulk of the heating occurring at scales that ...are currently unresolved.
Aims.
The goal of this work is to study the smallest brightening events observed in the extreme-UV quiet Sun.
Methods.
We used commissioning data taken by the Extreme Ultraviolet Imager (EUI) on board the recently launched Solar Orbiter mission. On 30 May 2020, the EUI was situated at 0.556 AU from the Sun. Its High Resolution EUV telescope (HRI
EUV
, 17.4 nm passband) reached an exceptionally high two-pixel spatial resolution of 400 km. The size and duration of small-scale structures was determined by the HRI
EUV
data, while their height was estimated from triangulation with simultaneous images from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory mission. This is the first stereoscopy of small-scale brightenings at high resolution.
Results.
We observed small localised brightenings, also known as ‘campfires’, in a quiet Sun region with length scales between 400 km and 4000 km and durations between 10 s and 200 s. The smallest and weakest of these HRI
EUV
brightenings have not been previously observed. Simultaneous observations from the EUI High-resolution Lyman-
α
telescope (HRI
Lya
) do not show localised brightening events, but the locations of the HRI
EUV
events clearly correspond to the chromospheric network. Comparisons with simultaneous AIA images shows that most events can also be identified in the 17.1 nm, 19.3 nm, 21.1 nm, and 30.4 nm pass-bands of AIA, although they appear weaker and blurred. Our differential emission measure analysis indicated coronal temperatures peaking at log
T
≈ 6.1 − 6.15. We determined the height for a few of these campfires to be between 1000 and 5000 km above the photosphere.
Conclusions.
We find that ‘campfires’ are mostly coronal in nature and rooted in the magnetic flux concentrations of the chromospheric network. We interpret these events as a new extension to the flare-microflare-nanoflare family. Given their low height, the EUI ‘campfires’ could stand as a new element of the fine structure of the transition region-low corona, that is, as apexes of small-scale loops that undergo internal heating all the way up to coronal temperatures.
The amazing climbing ability of geckos has attracted the interest of
philosophers and scientists alike for centuries. However,
only in the past few years has progress been made in
understanding the ...mechanism behind this ability, which relies on submicrometre
keratin hairs covering the soles of geckos. Each hair produces a miniscule
force 10−7 N (due to van der Waals and/or capillary
interactions) but millions of hairs acting together create a formidable
adhesion of 10 N cm−2: sufficient to keep geckos
firmly on their feet, even when upside down on a glass ceiling. It is very
tempting to create a new type of adhesive by mimicking the
gecko mechanism. Here we report on a prototype of such 'gecko tape' made by
microfabrication of dense arrays of flexible plastic pillars, the geometry of
which is optimized to ensure their collective adhesion. Our approach shows a
way to manufacture self-cleaning, re-attachable dry adhesives, although
problems related to their durability and mass production are yet to be
resolved.
Magnetic reconnection is a key mechanism involved in solar eruptions and is also a prime possibility to heat the low corona to millions of degrees. Here, we present ultra-high-resolution extreme ...ultraviolet observations of persistent null-point reconnection in the corona at a scale of about 390 km over one hour observations of the Extreme-Ultraviolet Imager on board Solar Orbiter spacecraft. The observations show formation of a null-point configuration above a minor positive polarity embedded within a region of dominant negative polarity near a sunspot. The gentle phase of the persistent null-point reconnection is evidenced by sustained point-like high-temperature plasma (about 10 MK) near the null-point and constant outflow blobs not only along the outer spine but also along the fan surface. The blobs appear at a higher frequency than previously observed with an average velocity of about 80 km s
and life-times of about 40 s. The null-point reconnection also occurs explosively but only for 4 minutes, its coupling with a mini-filament eruption generates a spiral jet. These results suggest that magnetic reconnection, at previously unresolved scales, proceeds continually in a gentle and/or explosive way to persistently transfer mass and energy to the overlying corona.
The magnetic anisotropy of Fe‐rich, thin, amorphous wires is tailored by stress annealing (SA). In particular, the effect of conventional annealing (CA) and SA on the magnetic properties of ...Fe74B13Si11C2 glass‐coated microwires is studied. CA treatment does not significantly change the character of the hysteresis loop. Under certain SA conditions (annealing temperature, Tann > 300 °C; applied stress, σ > 400 MPa), a transverse magnetic anisotropy is induced: a rectangular hysteresis loop transforms into an inclined one at magnetic‐anisotropy fields above 1000 A m–1. Under tensile stress, the rectangular hysteresis loop of microwires annealed using SA is recovered. Samples subjected to SA show noticeable magnetoimpedance and stress‐impedance effects, despite their large magnetostriction. The samples obtained exhibit a high stress sensitivity of their giant magnetoimpedance (GMI) effect and hysteretic properties, allowing the use of the obtained samples in magnetoelastic sensors, and for designing stress‐sensitive, tunable composite materials. By varying the time and temperature of such SA, we are able to tailor both the magnetic properties and the GMI of Fe‐rich microwires.
The magnetic anisotropy of Fe‐rich, thin, amorphous wires (see Figure) is tailored by stress annealing, allowing the induction of transverse magnetic anisotropy and a considerable stress‐sensitive giant magnetoimpedance effect in microwires with a positive magnetostriction constant. Such samples are suitable for magnetoelastic sensors and stress‐sensitive, tunable composite materials.
Graphene's linear dispersion relation makes its charge carriers behave as if they were massless. However, near the Dirac point where graphene's valence and conduction bands meet, electron-electron ...interactions cause this relation to diverge, such that it becomes strongly nonlinear and the effective carrier velocity doubles. A study reports measurements of the cyclotron mass in suspended graphene for carrier concentrations n varying over three orders of magnitude.
Measurements of magnetotransport in high quality InN nanowires in presence of conductive atomic-force microscope tip performed at a temperature of
K are presented. We demonstrate evidence of ...influence of the close to nanowire placed AFM tip at certain ranges of the back gate voltages and the decreasing of the influence in external magnetic field of
mT. We explain such a behavior by presence of the branched current under the surface of the InN nanowire similar to ones of two-dimensional electrons in heterostructures and graphene samples with point contacts.
The application of foamed polymers as one of the components of insulating coatings allows to solve the problems of energy saving and creation of optimal operating conditions for constructions. The ...systems of application of energy-efficient heat-insulating materials must consider both the particularities of the insulating materials and the functional orientation of the constructions. The implementation of the concept of seamless insulating coatings implies the achievement of thermal effect and reduction in air permeability both by means of the application of thermal insulation with low thermal conductivity and the minimization of junctions between separate elements of the insulating coating, which is achieved using elastic foamed polymers and, first of all, polyethylene foam. Construction of seamless insulating coatings creates practically impermeable heat, vapor, and water barriers along the outer perimeter of the insulated object. Multilayer products based on polyethylene foam represent a relatively new material—a fact that requires examination of their properties, as well as under various operating conditions, and development of a methodology for evaluation of the operational resistance of these materials in structures of different purposes, including cold conservation. The performed tests have shown that the compressive strength at 10% deformation is determined by the function of load application area and varies from 70 kPa during the test of cube samples of 10 × 10 × 10 in size to 260 kPa for areas exceeding 100 m2. The longitudinal tensile strength amounts to 80–92 kPa, and the strength of the weld seam is equal to 29–32 kPa. It has been established that the values of thermal conductivity of polyethylene foam with an average density of 18–20 kg/m3 amounts to 0.032–0.034 W/(m·K), diffusion moisture absorption is equal to 0.44 kg/m2 without a metallized coating and 0.37 kg/m2 with a metallized coating; water absorption after partial immersion in water for 24 h amounts to 0.013 kg/m2; water absorption by volume after complete water immersion for 28 days is equal to 0.96%. The material does not practically change its properties under conditions of long-term temperature alteration from −60 to +70 °C. The developed and implemented insulation systems for protective surfaces of framed construction objects, rubbhalls and frameless structures, floating floors, indoor ice rinks, and snow conservation systems are presented.
We point out that superconducting quantum computers are prospective for the simulation of the dynamics of spin models far from equilibrium, including nonadiabatic phenomena and quenches. The ...important advantage of these machines is that they are programmable, so that different spin models can be simulated in the same chip, as well as various initial states can be encoded into it in a controllable way. This opens an opportunity to use superconducting quantum computers in studies of fundamental problems of statistical physics such as the absence or presence of thermalization in the free evolution of a closed quantum system depending on the choice of the initial state as well as on the integrability of the model. In the present paper, we performed proof-of-principle digital simulations of two spin models, which are the central spin model and the transverse-field Ising model, using 5- and 16-qubit superconducting quantum computers of the IBM Quantum Experience. We found that these devices are able to reproduce some important consequences of the symmetry of the initial state for the system’s subsequent dynamics, such as the excitation blockade. However, lengths of algorithms are currently limited due to quantum gate errors. We also discuss some heuristic methods which can be used to extract valuable information from the imperfect experimental data.
A review on extending the fields of applications of the atomic-force-microscope hybrid mode is presented. This is the main mode for two-probe AFM manipulators. Various methods for improving the ...feedback system of AFMs, which significantly reduce noise in topographic mapping are presented. Additionally, the successful application of a wide range of probes, both flexible ones such as standard W probes and glass capillaries as well as rigid probes (sapphire probes with probe-tip diameters of dozens of microns) are presented as well. We show examples of the application of this mode in measurements of the conductivity and adhesion forces of nanowhiskers on a Si substrate. Besides this, the application of the hybrid mode in microfluidics and nanofluidics, such as the formation of drops of defined volumes, the replacement of drops, and their division and merging are presented. Examples of different techniques for manipulating nanowhiskers on the surface of a Si substrate are presented. The possibility of the manipulation of nanowhiskers by means of a liquid flow formed by an AFM probe, i.e., avoiding direct tip-to-nanowhisker contact, is shown.
Literature data about qualitative composition of the classes of polar lipids constituting plant cell membranes are discussed. A diversity of classes of phospho-, glyco-, and other lipids and ...hydrophobic compounds lacking acyl groups are given. Fatty acid composition of polar lipids, composition of amino alcohols as components of glycosphingolipids, and oxyacids abundant in cerebrosides are considered. A key role of saturated fatty acids in the creation of an optimal physical state of membranes necessary for their normal operation is emphasized. A necessity and feasibility of construction of 3D models of biomembranes is stressed. A logic approach is proposed to a better understanding of the role of qualitative diversity of lipid composition in membrane organization. Materials showing a possibility of chemical and biological transformation of lipids in plants are cited. Several issues of membrane structure, including microdomains, remodeling of bilayer, and vesicular traffic are addressed.
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