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Investigation of the electronic properties of ultrathin films of pure bismuth and bismuth–antimony alloys is of interest, since it is found that the conductivity increases with decreasing sample ...thickness. The results of experimental investigation of the structure, as well as of the electrical, galvanomagnetic, and thermoelectric properties of pure bismuth and Bi
1 –
x
Sb
x
thin films (
x
= 0.05 and 0.12) on a mica substrate in the thickness range of 10–30 nm are presented. An increase in the conductivity with decreasing thickness of the samples, which may be induced by the presence of topologically protected surface states, is found. It is shown that the features of this effect depend significantly on the band structure of alloys. The form of the temperature dependences of the Seebeck coefficient casts doubt on the fact that the surface states have a positive effect on the thermoelectric efficiency of thin bismuth–antimony films. However, the detection of positive thermoelectric power in Bi
0.88
Sb
0.12
samples may become an important factor in learning how to create the
p
branch of thermoelectric converters.
Since the energy spectrum of bismuth charge carriers is highly sensitive to mechanical deformations, studying their influence, leading to an increase or decrease in the overlap of actual extrema, on ...the transport properties of charge carriers in ultrathin bismuth films makes it possible to investigate the combination of manifestations of the quantum size effect and metallic surface states. In this work, the temperature dependencies of the electrical and galvanomagnetic properties of thin bismuth films (10–1250 nm) are studied under conditions of in-plane tensile and compressive deformation. Deformations are created as a result of the difference in the coefficients of thermal expansion of the film and substrate materials. Silicon with an oxidized surface, mica, and polished cleavage (111) CaF2 are used in order to create either tensile and compressive deformations. The presence of film deformations is confirmed by XRD. The magnitude of deformation is calculated based on the CTEs of the materials. The absence of mechanical stress relaxation or the formation of additional defects during temperature measurements is confirmed by the absence of hysteresis of properties in the range of 77–300 K. Based on the experimental results, the mobilities and concentration of charge carriers are calculated within the framework of the two-band model. As the film thickness decreases to less than 100 nm, an increase in the charge carrier concentration is observed, which is associated with metallic surface states. It is shown that the magnitude of the effect of deformation on the concentration of charge carriers in films of all thicknesses remains unchanged.
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•Deformation affects the transport properties of bismuth films.•Compression increases charge carrier concentration, and tension decreases it.•Metallic surface states increase the concentration in films thinner than 100 nm.•Effect of deformation remains constant across whole thickness range.•Metallic surface states are relatively weakly affected by deformation.
The features of the magnetic state of an array of parallel oriented permalloy ribbons are discussed. The arrays are made by explosive lithography. The ribbons have a thickness of 180 nm, a width of ...2.8 µm, and a length of about 4 mm. The distance between ribbons in different samples varies in the range from 300 nm to 4 μm. It is found that the ribbons in the regions far from the end faces are in a single-domain state with small-angle ripples, the magnetization distribution of which correlates with inhomogeneities of the ribbon side surfaces. Moreover, there is a distinct relationship in the spatial distribution of the ripples between adjacent ribbons with a relatively small distance between them. This makes it possible to evaluate the role of the magnetostatic coupling of magnetic subsystems of array elements and to estimate the characteristic value of the random stray field that pins the magnetization.
The effect of equal-channel angular pressing on structural phase transformations and mechanical properties of the as-cast hypoeutectic Al–4Ca–1.3Fe–0.8Mn–0.1Zr–0.1Sc alloy has been studied. ECAP was ...carried out under isothermal conditions at a temperature of 200 °C, with a channel intersection angle of 110º, using the BC route and the number of passes N = 6. After ECAP, a substructure with an increased dislocation density has developed in the alloy. ECAP led, firstly, to the evolution of the dendritic structure (dendrites elongate and merge with each other), and secondly, to the refinement of the Al4Ca, Al4Ca(Fe) and Al3−x(Fe, Mn) eutectic phase particles to nano- and submicron scale, their mixing and partial segregation of calcium. The tensile tests of the ECAP processed alloy showed that its strength increased, while its ductility decreased. The yield point increased from 122 to 257 MPa, the ultimate tensile strength increased from 174 to 281–314 MPa, and the relative elongation decreased from 6 to 1–3%. After ECAP, the strength is higher, and the relative elongation is lower for longitudinal specimens compared to transverse specimens.
•The as-cast Al-4Ca-1.3Fe-0.8Mn-0.1Zr-0.1Sc hypoeutectic alloy was processed by ECAP at 200 °C.•The elongation of the (Al)-dendrites along the pressing direction and their merging occurs.•The refinement of the eutectic phase particles to nano- and submicron scale occurs.•The eutectic phase particles mixing and partial Ca segregation occurs as a result of mass transfer.•The 1.7–2.2-fold increase in the alloy’s strength while maintaining moderate ductility occurs.
This paper presents the results of studying the magnitude of the strain of semimetal films created by the dome bending of the substrate. The deformation is controlled by X-ray diffraction (XRD) ...analysis. It is shown that the dome bending method can be used to study films under conditions of the in-plane deformation that occurs in the film-substrate system due to the difference in the coefficients of thermal expansion of the film and substrate material. It is established that the deformation created by the dome bending of the substrate in combination with the use of substrates with a different thermal expansion makes it possible to obtain a relative in-plane deformation of bismuth films up to 0.8% at 300 K.
Chemotherapy and radiation therapy for cancer often have severe side effects that limit their efficacy. Because these effects are in part determined by p53-mediated apoptosis, temporary suppression ...of p53 has been suggested as a therapeutic strategy to prevent damage of normal tissues during treatment of p53-deficient tumors. To test this possibility, a small molecule was isolated for its ability to reversibly block p53-dependent transcriptional activation and apoptosis. This compound, pifithrin-α, protected mice from the lethal genotoxic stress associated with anticancer treatment without promoting the formation of tumors. Thus, inhibitors of p53 may be useful drugs for reducing the side effects of cancer therapy and other types of stress associated with p53 induction.
Identification of unique features of cancer cells is important for defining specific and efficient therapeutic targets. Mutant p53 is present in nearly half of all cancer cases, forming a promising ...target for pharmacological reactivation. In addition to being defective for the tumor-suppressor function, mutant p53 contributes to malignancy by blocking a p53 family member p73. Here, we describe a small-molecule RETRA that activates a set of p53-regulated genes and specifically suppresses mutant p53-bearing tumor cells in vitro and in mouse xenografts. Although the effect is strictly limited to the cells expressing mutant p53, it is abrogated by inhibition with RNAi to p73. Treatment of mutant p53-expressing cancer cells with RETRA results in a substantial increase in the expression level of p73, and a release of p73 from the blocking complex with mutant p53, which produces tumor-suppressor effects similar to the functional reactivation of p53. RETRA is active against tumor cells expressing a variety of p53 mutants and does not affect normal cells. The results validate the mutant p53-p73 complex as a promising and highly specific potential target for cancer therapy.
Special features of thermomechanical behavior and structure formation of shape memory alloy Ti – 19 at.% Zr – 14 at.% Nb for medical applications are studied under the conditions of upsetting at 600 ...– 1000°C with strain rates 0.1, 1, and 10 sec
–1
. The main parameters of the compressive stress–strain diagram are determined. Metallographic and x-ray diffraction analyses of the alloy are performed. The Vickers hardness of the specimens is measured. The alloy is shown to be well deformable under the conditions studied, and its sensitivity to the deformation rate is not high. Recommendations are developed for thermomechanical treatment of semiproducts from the Ti – Zr – Nb alloy.
The graphene oxide (GO) film embossing and reduction was demonstrated under femtosecond laser pulses. The best conductivity of laser reduced GO film of 200Ω/□ was achieved for fs laser pulses energy ...of 35–45nJ and 10–25 pulses per µm. We demonstrate the patterned laser reduction over the embossed GO film that holds it integrity and conductivity. Laser reduced GO properties was studied by Raman, SEM and sheet resistance measurements.
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•Laser direct patterning of reduced GO was produced from 500nm GO film on flexible (PET) substrate by femtosecond pulses.•For thick LrGO film there is a minimum in resistance while linear crystalline quality increases with laser fluence.•Laser induced embossing of GO provides 3D formation with details aspect ratio as 1:10.•Two-step laser-induced detachment of GO patches from polymer substrates is shown.
The paper presents a brief overview of the ITER Divertor Test Facility (IDTF) located at the Efremov Institute of Electrophysical Apparatus, St. Petersburg, Russia; it describes the high heat flux ...tests of the plasma-facing ITER divertor components performed on the IDTF and explains the role of the divertor and the choice of tungsten as the divertor armor material. The IDTF is a unique test facility in Russia: all plasma-facing ITER divertor components pass the high heat flux tests there. The high heat flux tests consist in the thermal cycling load produced by the electron flow accelerated by the electron-beam system of the test facility and applied to the test objects placed in the IDTF vacuum chamber. The alternating cycles of heating and cooling of particular parts of the test object armor material result in its gradual wear. Further investigation of the defects occurring under the tests makes it possible to define the validity of the technology chosen for production of the plasma-facing components. In the ten years of operation (by the beginning of 2020), about 20 main test campaigns have been performed of small-scale mock-ups and full-scale prototypes of the plasma-facing ITER divertor components. Serial tests of the divertor elements to be performed within the framework of the ITER project should be the next important step of the test facility operation.
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