Correlation effects in the density of states of annealed GaMnAs

We report on an experimental study of low temperature tunnelling in hybrid NbTiN/GaMnAs structures. The conductance measurements display a root mean square V dependence, consistent with the opening of a correlation gap in the density of states of GaMnAs. Our experiment shows that low temperature annealing is a direct empirical tool that modifies the correlation gap and thus the electron-electron interaction. Consistent with previous results on boron-doped silicon we find, as a function of voltage, a transition across the phase boundary delimiting the direct and exchange correlation regime.Comment: Replaced with revised version. To appear in Phys. Rev.

Aryl-viologen pentapeptide self-assembled conductive nanofibers.

A pentapeptide sequence was functionalized with an asymmetric arylated methyl-viologen (AVI3D2) and through controllable β-sheet self-assembly, conductive nanofibers were formed. Using a combination of spectroscopic techniques and conductive atomic force microscopy, we investigated the molecular conformation of the resultant AVI3D2 fibers and how their conductivity is affected by β-sheet self-assembly. These conductive nanofibers have potential for future exploration as molecular wires in optoelectronic applications.ERC (‘ASPiRe’, 240629) Marie Curie (FP7 ‘SASSYPOL’ ITN, 607602

Surface versus bulk characterization of the electronic inhomogeneity in a VO_{2} film

We investigated the inhomogeneous electronic properties at the surface and interior of VO_{2} thin films that exhibit a strong first-order metal-insulator transition (MIT). Using the crystal structural change that accompanies a VO_{2} MIT, we used bulk-sensitive X-ray diffraction (XRD) measurements to estimate the fraction of metallic volume p^{XRD} in our VO_{2} film. The temperature dependence of the p$^{XRD}$ was very closely correlated with the dc conductivity near the MIT temperature, and fit the percolation theory predictions quite well: $\sigma$ $\sim$ (p - p_{c})^{t} with t = 2.0$\pm$0.1 and p_{c} = 0.16$\pm$0.01. This agreement demonstrates that in our VO$_{2}$ thin film, the MIT should occur during the percolation process. We also used surface-sensitive scanning tunneling spectroscopy (STS) to investigate the microscopic evolution of the MIT near the surface. Similar to the XRD results, STS maps revealed a systematic decrease in the metallic phase as temperature decreased. However, this rate of change was much slower than the rate observed with XRD, indicating that the electronic inhomogeneity near the surface differs greatly from that inside the film. We investigated several possible origins of this discrepancy, and postulated that the variety in the strain states near the surface plays an important role in the broad MIT observed using STS. We also explored the possible involvement of such strain effects in other correlated electron oxide systems with strong electron-lattice interactions.Comment: 27 pages and 7 figure

Energy-resolved electron-spin dynamics at surfaces of p-doped GaAs

Electron-spin relaxation at different surfaces of p-doped GaAs is investigated by means of spin, time and energy resolved 2-photon photoemission. These results are contrasted with bulk results obtained by time-resolved Faraday rotation measurements as well as calculations of the Bir-Aronov-Pikus spin-flip mechanism. Due to the reduced hole density in the band bending region at the (100) surface the spin-relaxation time increases over two orders of magnitude towards lower energies. At the flat-band (011) surface a constant spin relaxation time in agreement with our measurements and calculations for bulk GaAs is obtained.Comment: 6 pages, 4 figure

Стабилизация движения робота по показаниям электронного компаса

Laser-induced breakdown spectroscopy has been applied to polymer samples in order to investigate the possibility of using this method for the identification of different materials. The plasma emission spectra of high-density polyethylene (HDPE), low-density polyethylene (LDPE), polyvinyl chloride (PVC), polyethylene terephthylene (PET), and polypropylene (PP) have been studied. Spectral features have been measured - for example, the 725.7 nm chlorine line, the 486.13 mm H(?) line, and the 247.86 nm carbon line - whose evaluation with neural networks permits identification accuracies between 90 and 1 00 per cent, depending on polymer type

Smearing of phase transition due to a surface effect or a bulk inhomogeneity in ferroelectric nanostructures

The boundary conditions, customarily used in the Landau-type approach to ferroelectric thin films and nanostructures, have to be modified to take into account that a surface of a ferroelectric (FE) is a defect of the ``field'' type. The surface (interface) field is coupled to a normal component of polarization and, as a result, the second order phase transitions are generally suppressed and anomalies in response are washed out. In FE films with a compositional (grading) or some other type of inhomogeneity, the transition into a monodomain state is suppressed, but a transition with formation of a domain structure may occur.Comment: 5 pages, 1 figure; the effective bias field is very large, the estimate is adde

Формирование алмазоподобных кремний-углеродных покрытий

Выпускная квалификационная работа 111 с., 23 рис., 29 табл., 39 источников, 1 прил. Ключевые слова: алмазоподообные углеродные, кремний, ПФМС, несамостоятельный дуговой разряд, твердость, тонкие пленки. Объектом исследования являются алмазоподобные кремний-углеродные покрытия, полученные из плазмы несамостоятельного дугового разряда с накаленным катодом. Цель работы – изучение процесса формирования алмазоподобных кремний-углеродных покрытий и исследование их свойств В процессе работы проводилась оптимизация процесса осаждения и экспериментальные исследования полученных пленок. В результате исследования были получены твердые покрытия с низкой степенью износа и низким коэффициентом трения. Область применения: повышение срока службы промышленных механизмов, медицинских инструментов и др.Final qualifying work of 111 p., 23 Fig., 29 tables, 39 source, 1 app. Keywords: diamond-like carbon, silicon, PFMS, dependent arc discharge, hardness, thin films. The object of the study is silicon-doped diamond-like carbon films prepared from the plasma of the dependent arc discharge with hot cathode. The work objective was the optimization of the process of deposition of silicon-doped diamond-like carbon films, synthesis of coatings and their research. In the process of the work it was carried out, that the optimization of the deposition process and experimental investigations of the received films. The study was received the solid films with a high wear resistance and a low friction coefficient. Scope: improving the lifetime of industrial machinery, medical tools, and other

Point defects on the (110) surfaces of InP, InAs and InSb: a comparison with bulk

The basic properties of point defects, such as local geometries, positions of charge-transfer levels, and formation energies, have been calculated using density-functional theory, both in the bulk and on the 110 surface of InP, InAs, and InSb. Based on these results we discuss the electronic properties of bulk and surface defects, defect segregation, and compensation. In comparing the relative stability of the surface and bulk defects, it is found that the native defects generally have higher formation energies in the bulk. From this it can be concluded that at equilibrium there is a considerably larger fraction of defects at the surface and under nonequilibrium conditions defects are expected to segregate to the surface, given sufficient time. In most cases the charge state of a defect changes upon segregation, altering the charge-carrier concentrations. The photo-thresholds are also calculated for the three semiconductors and are found to be in good agreement with experimental data

The novel benzimidazole derivative BRP-7 inhibits leukotriene biosynthesis in vitro and in vivo by targeting 5-lipoxygenase-activating protein (FLAP).

BACKGROUND AND PURPOSE: Leukotrienes (LTs) are inflammatory mediators produced via the 5-lipoxygenase (5-LOX) pathway and are linked to diverse disorders, including asthma, allergic rhinitis and cardiovascular diseases. We recently identified the benzimidazole derivative BRP-7 as chemotype for anti-LT agents by virtual screening targeting 5-LOX-activating protein (FLAP). Here, we aimed to reveal the in vitro and in vivo pharmacology of BRP-7 as an inhibitor of LT biosynthesis. EXPERIMENTAL APPROACH: We analysed LT formation and performed mechanistic studies in human neutrophils and monocytes, in human whole blood (HWB) and in cell-free assays. The effectiveness of BRP-7 in vivo was evaluated in rat carrageenan-induced pleurisy and mouse zymosan-induced peritonitis. KEY RESULTS: BRP-7 potently suppressed LT formation in neutrophils and monocytes and this was accompanied by impaired 5-LOX co-localization with FLAP. Neither the cellular viability nor the activity of 5-LOX in cell-free assays was affected by BRP-7, indicating that a functional FLAP is needed for BRP-7 to inhibit LTs, and FLAP bound to BRP-7 linked to a solid matrix. Compared with the FLAP inhibitor MK-886, BRP-7 did not significantly inhibit COX-1 or microsomal prostaglandin E2 synthase-1, implying the selectivity of BRP-7 for FLAP. Finally, BRP-7 was effective in HWB and impaired inflammation in vivo, in rat pleurisy and mouse peritonitis, along with reducing LT levels. CONCLUSIONS AND IMPLICATIONS: BRP-7 potently suppresses LT biosynthesis by interacting with FLAP and exhibits anti-inflammatory effectiveness in vivo, with promising potential for further development