The present work deals with the exactly solvable spin-1/2 Ising-Heisenberg model on an
infinite but regular two-dimensional lattice composed of identical inter-connected bipyramidal
plaquettes with the aim to clarify a bipartite entanglement between the Heisenberg spins at
zero as well as finite temperatures. The quantity called concurrence is used as an indicator for
determining a...
The Brownian motion of a particle in a bath of other particles is effectively described by the
generalized Langevin equation (GLE). Following Kubo, it is usually assumed that if external
forces act on the system, they do not affect the thermal force and the memory function that
enter the GLE. The action of such forces is restricted to the Brownian particle (BP), leaving
the bath particles...
The Brownian motion of a particle immersed in a bath of charged particles is considered when
the system is placed in a magnetic field. The widely accepted Caldeira-Legget particle-bath
model is modified so that not only the charged Brownian particle (BP) but also the bath
particles respond to the external field. For stationary systems, two equations for the BP
motion across the field are...
The Heusler Ni 2 Mn 1+x Sn 1-x alloys exhibit structural martensitic transformation from cubic
(austenite) into orthorhombic (martensite) phase in a narrow composition range, 0,4 ≤ x ≤ 0,6,
only. The transformation is accompanied by a significant changes of volume, magnetization
and by large anomalies in transport properties. We have studied forced volume magneto-
striction, Joulian...
Sbírka řešených úloh z fyziky a Sbírka fyzikálních pokusů vznikají na Katedře didaktiky
fyziky MFF UK. Jedná se o podpůrné materiály pro studenty a učitele základních, středních
i vysokých škol.
Sbírka řešených úloh z fyziky je vyvíjena již 14 let a obsahuje přes 900 úloh v češtině. Je
primárně určena vysokoškolským studentům a žákům středních škol, lze v ní ale nalézt
i úlohy na úrovni...
Metallic glasses are still attracting the interest of researchers namely for their very good soft
magnetic properties. With the aim to enhance their practical applications, new compositions
are continuously scrutinized. Here, we present Mössbauer spectrometry study of a novel
Fe 51 Co 12 Si 16 B 8 Mo 5 P 8 metallic glass prepared in a form of ribbons by conventional method of
planar flow...
Polyaniline (PANI) is a material known for its high conductivity and also huge range of
obtainable conductivities. In general, three types of charge carriers are considered in PANI
salt, namely holes, polarons and protons. Many authors attribute the high conductivity of acid
doped PANI to polarons [1-3]. We show that conductivity of polarons might not be
necessarily the prevailing...
If we put a several tens of microns thin sample of nematic liquid crystal with planar alignment
of molecules with respect to the LC cell surface in between two crossed plane polarizers,
illuminate it by white light and rotate appropriately, then using a fiber optic spectrometer we
can observe a quasi-periodic spectral distribution of intensity of light behind the output
polarizer. The...
Lawsonite [CaAl2Si2O7(OH)2·H2O] is an uncommon mineral found in metamorphic rocks,
occurring at subduction zones, supposedly at depths of up to 250 km. It contains 11.5 wt%
water in its crystal structure. At room temperature, it is orthorhombic, crystallizing in the
Cmcm space group. Its structure contains a silicate tetrahedra framework with four formulas
in the unit cell. Each chemical...
Thermoplastic starch, a group of starch-based materials, has often been under review because
it can be used as low-cost bioplastics. Native starch is usually processed under the action of
high temperature and shear stress with addition of plasticizers such as low molecular weight
polyols and/or amide-containing molecules to obtain a moldable thermoplastic material. Such
materials are...
STEM vzdelávanie zamerané na Science, Technology, Engineering a Mathematics zahŕňa
v sebe prípravu vysokoškolsky vzdelaného absolventa technickej univerzity, ktorý v priebehu
prípravy získal zručnosti zo všetkých spomínaných oblastí. Podľa Bloomovej taxonómie
poznávacích cieľov takéto vzdelávanie je realizované na vyšších stupňoch, ako je analýza,
aplikácia a hodnotiace posúdenie....
V lednu 1956 bylo Československo přizváno k účasti na založení ústavu pro jaderný, který
měl být obdobou Laboratoře Evropské organizace pro jaderný výzkum (CERN) v Ženevě pro
země tzv. lidové demokracie. Československé stranické a vládní orgány nabídku přijaly.
Na konferenci o ústavu, která se konala ve dnech 20.–26. března 1956 v Moskvě, byla
československou vládou vyslána sedmičlenná...
Tokamak COMPASS je vybaven dvěma sadami diagnostik, které jsou rutině využívány
k počítání tomografických inverzí. Jedná se o polovodičové diody, které slouží buď jako
bolometry (měří celkový vyzářený výkon), nebo jsou vybaveny beryliovým filtrem a měří
měkké rentgenové záření.
V důsledku omezení pozorovacích úhlů je tomografická inverze na tokamacích nedostatečně
určená, a proto se...
The uranium based intermetallics are intensively studied because of dual character of uranium
5f electrons. Unique coexistence of ferromagnetism and superconductivity has been revealed
in URhGe and UCoGe crystalizing in the orthorhombic TiNiSi-type structure. Since UCoGe
(T C =2.5 K) is very close to magnetic instability, it is a candidate to observe vanishing of
ferromagnetic order and...
Dust grains in the Martial dust storms or dust devils may be electrically charged by
triboelectric effects and laboratory experiments show that under specific conditions electric
discharges might occur in the dusty Martian atmosphere. Remote measurements from the
Earth using a 34-m Deep Space Network antenna have shown a non-thermal component of
electromagnetic radiation from Mars which...
Atomic Force Microscopy (AFM) is a powerful imaging technique which provides very high-resolution images and topological data in scales of nanometers. The quality of the obtained data is determined by quality of used AFM tip and fine adjustment of measuring parameters and settings of the machine. The measurement becomes more challenging if the AFM probe is about to approach a soft and elastic...
Kvarkonia jsou dúležitou sondou k vyšetřování vlastností kvark-gluonového plasmatu.
Proton-protonové srážky jsou nezbytným prostředkem k ustanovení základních vlastností,
které slouží ke studiu kvarkonií v proton-jaderných a jádro-jaderných srážek. Tento poster
prezentuje základní charakteristiky Upsilon mezonů zjištěné pomocí Monte Carlo generátorů
v proton-protonových srážkách při √ sNN...
Al-Li based alloys of AA2195 type are designed mainly for aerospace applications. They
exhibit a very high strength due to a presence of strengthening precipitates of a nanometric
size. However, materials prepared by a conventional direct-chill casting and following rolling
exhibit strong crystallographic texture and inhomogeneous mechanical properties. This
inconvenient behavior could be...
The Waves instrument onboard the Juno spacecraft recorded numerous cases of dispersed
electromagnetic waves generated by Jovian lightning. These waves, also known as whistlers,
propagated through ionospheric and magnetospheric plasmas before their detection by Juno
during its close approaches to Jupiter. We present observations of nearly five thousand low-
dispersion lightning whistlers...
Nitride semiconductors became the second most important semiconductor material after
silicon in the last two decades. Many daily used devices, such as blue light emitting diodes or
high electron mobility transistors in electronic devices, are based on nitride semiconductors.
Despite the nitride devices mass production, there are many open questions and not well
understood phenomena which...
One of the approaches to investigate the equation-of-state of dense nuclear matter is the study
of the short-range correlations of nucleons in nuclei. Short-range correlations have densities
comparable to the density in the center of a nucleon and they can be considered as the drops
of cold dense nuclear matter. Dp elastic and dp breakup processes are investigated at Internal
Target...
Nanoparticles of hexagonal phase in bcc-Ti(Mo) single crystals ( phase) occur due to a
diffusionless athermal to transformation and they grow during follow-up ageing at
elevated temperatures, while the alloying atoms (Mo in our case) are expelled from the
nanoparticle volumes. We used anomalous x-ray diffraction for the study of local chemical
composition of growing particles and...
The idea of controlling the magnetic ground state of a spin-1 one-dimensional
antiferromagnetic (1d AFM) quantum magnets has long been of interest to physicists. In the
study of anisotropic 1d AFM systems based on Ni 2+ compounds, a series of topologically
protected quantum phases was observed, one of these phases is the topologically protected
Haldane phase [1, 2]. The magnetic ground...
Current work is focused on the lattice subsystem of Cu(en)Cl 2 , Cu(tn)Cl 2 and
Cu(en)(H 2 O) 2 SO 4 (en = C 2 H 8 N 2 , tn = C 3 H 10 N 2 ), quasi-two-dimensional quantum magnets with
one-dimensional polymeric structure. Magnetic layers were described within spin = 1/2
Heisenberg models on the rectangular and zig-zag-square lattice with nearest-neighbor
couplings J 1 > J 2 . The...
Small-scale thin films are frequently used in microelectronic devices and micro-electro-
mechanical systems where they are commonly subjected to high strains during their dynamic
motion. However, mechanical behavior of thin films significantly differs from the behavior
observed in bulk materials. To understand the size dependent properties of deformation
mechanisms, characterization of the...
Bonding of aluminium and steel into one single material – an aluminium-steel clad –
represents an excellent composite material, which provides high potential for applications in
automobile industry by combination of properties of respective materials – high stiffness and
strength of steel and durability, corrosion resistance, thermal capacity and high specific
strength of aluminium....
Twin-roll casting of AA8079 aluminum sheets creates non-equilibrium structure as a result of
high solidification rates. Homogenization treatments consisting of an exposure of the as-cast
material to high temperatures close to the melting point result in a redistribution of solute
atoms and a formation of a more stable structure. Newly formed equilibrium particles have
different...
The usual interband transitions S0–S0, S0–S1, S0–S2 can be clearly identified in the recently published photoluminescence measurements on P3HT layers. However, in many cases the spectra are characterized by weaker ripples besides these main features. We point out their possible interpretation by means of the H and J aggregates theory proposed by Spano (F. C. Spano, J. Chem. Phys. 122,...
