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Significant results of scientific activity in year 2015

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Strain-engineered silicon nanocrystals (SiNCs) have recently been shown to possess direct bandgap. Here, we report the observation of a rich structure in the single-nanocrystal photoluminescence spectra of strain-engineered direct-bandgap SiNCs in the temperature range of 9–300 K. The relationship between individual types of spectra is discussed, and the numerical modeling of spectral diffusion of the experimentally acquired spectra reveals a common origin for most types...

Mechanická a termomechanická únava kovových vláken ze slitiny s tvarovou pamětí NiTi je v současnosti v centru pozornosti v oboru. My jsme v roce 2015 analyzovali a publikovali výsledky unikátního in-situ experimentu, v němž jsme pomocí difrakce synchrotronového záření pozorovali vývoj mikrostruktury a vnitřního napětí v superelastickém vláknu NiTi během cyklické tahové deformace.

Top kvark, nejtěžší známá elementární částice, je díky své extrémní hmotnosti vhodným kandidátem pro hledání signálů za rámcem standardního modelu (SM) částicové fyziky. Fyzika top kvarku patří tradičně k hlavním oblastem výzkumu, na který se pracovníci našeho ústavu zaměřují a kteří také patřili k hlavním autorům práce. Měření nábojové asymetrie v párové produkci top kvarku v proton-protonových srážkách na urychlovači LHC v CERN představuje důležitý test SM částicové fyziky.

Hematite, α- Fe2O3, is considered as one of the most promising materials for sustainable hydrogen production via photoelectrochemical water splitting with a theoretical solar-to-hydrogen efficiency of 17%. However, the poor electrical conductivity of hematite is a substantial limitation reducing its efficiency in real experimental conditions. Despite of computing models suggesting that the electrical conductivity is extremely anisotropic, revealing...

The rate at which atoms and ions within a plasma are further ionized by collisions with the free electrons is a fundamental parameter that dictates the dynamics of plasma systems at intermediate and high densities. While collision rates are well known experimentally in a few dilute systems, similar measurements for nonideal plasmas at densities approaching or exceeding those of solids remain elusive. Here we describe a spectroscopic method to study collision rates in...

The magnetic quadrupole structure formation during the interaction of two ultrashort high power laser pulses with a collisionless plasma is demonstrated with 2.5-dimensional particle-in-cell simulations. The subsequent expansion of the quadrupole is accompanied by magnetic-field annihilation in the ultrarelativistic regime, when the magnetic field cannot be sustained by the plasma current. This results in a dominant contribution of the displacement current exciting a...

Structure solution and refinement from single-crystal X-ray diffraction data has become a standard approach for determination of crystal structures. On the other hand, electron diffraction used to be applied for the same purpose much more rarely, although numerous successful solutions were reported (Vainshtein, 1964[Vainshtein, B. K. (1964). Electron Diffraction Structure Analysis. Oxford: Pergamon Press.]; Cowley, 1992[Cowley, J. M. (1992). Electron Diffraction...

Liquid crystals (LCs) are highly fluid self-assembling media revealing the complexity of physical properties as well as providing a powerful tool for multidisciplinary research. From the application point of view, the reorientation of nematics under an applied electric field is a fundamental phenomenon, which is widely used in modern technologies. The self-assembling properties of LCs are strictly linked to the shape and chemical structure of the molecules.1 A variety of...

A model of filaments of the twist-grain-boundary smectic-A phase (TGBA) arising from the homeotropic smectic-A phase and nucleating on the sample surface is proposed. The model is based on the concept of finite blocks of parallel smectic layers forming a helical structure. The blocks are surrounded by dislocation loops. The model describes the filament structure near the sample surface and the observed inclination of the filament axis with respect to the easy direction of...

u na substrátu, který je dekorován monodisperzními magnetickými nanočásticemi.

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