444 research outputs found
Synthesis and Properties of High Tilted Antiferroelectric Esters with Partially Fluorinated Alkoxyalkoxy Terminal Chains
Novel chiral esters with partially fluorinated alkoxyalkoxy terminal chains are described. Their phase transition temperatures, enthalpies, and electrooptical properties are reported. A helical pitch in pure compounds and their mixtures based on selective reflection of light is also characterized
Time-domain modeling of dispersive and lossy liquid-crystals for terahertz applications
A numerical framework based on the finite-difference timedomain method is proposed for the rigorous study of electro-optically tunable terahertz devices based on liquid crystals. The formulation accounts for both the liquid-crystal full-tensor anisotropy and the dispersion of its complex refractive indices, which is described via modified Lorentzian terms. Experimentally characterized liquid-crystalline materials in the terahertz spectrum are fitted and modeled in benchmark examples, directly compared with reference analytical or semi-analytical solutions. In addition, the efficiency of broadband time-domain modeling of the proposed technique is also demonstrated by accurately reproducing time-domain spectroscopy measurements. © 2014 Optical Society of America
Ferroelectric liquid crystal for use in a new generation of LCDs
The key to improvements in liquid crystalline displays lies in the continuous synthesis and studies of new kinds of liquid crystalline substances. Among them, ferroelectric compounds are the subject of much attention, due to the potential progresses in switching time, colour depth, and other qualities of liquid crystal displays. In this paper we describe the research of the physical properties of 4-(2-methylbutoxy)phenyl 4-(octyloxy)-benzoate for purposes of its potential application in liquid crystal displays
Computer faceted thermal model of helicopter
The paper presents a computer Faceted Thermal Target Model of helicopter (FTTM) describing radiative properties of target in the infrared. The model is predestined for target simulation in analyses of influence of thermal-scene conditions on the possibilities of target detection by a thermodetection system. This is a faceted model describing the target as a set of facets. The set of data for the model of helicopter requires information on the shape and dimensions of the target as well as on temperature distribution and emissivity coefficient of its surface. The model enables to determine emission of radiation from the target surface for various directions and distances of detection. It makes possible to obtain the data necessary to design devices for infrared recognition with a limited application of costly experimental investigations. 1
The activity and immunoexpression of cathepsin D in rat male reproductive organs
Cathepsin D is a cysteine endopeptidase that belongs to the lysosomal enzyme
family. The aim of the study was to evaluate the enzyme immunoexpression and
activity in selected male genital organs in mature Wistar rats. The activity of
cathepsin D was measured spectrophotometrically in homogenates of the testis,
epididymis, seminal vesicle and prostate. Immunohistochemical staining was
also performed in the ductus deferens. Enzyme activity was found in the following
sequence: testis>epididymis>dorsal prostatic lobe>seminal
vesicle>lateral prostatic lobe>ventral prostatic lobe. Although there were differences
in enzyme activity between various organs of the male reproductive
system, cathepsin D immunoreactivity was seen exclusively in the Sertoli and
Leydig cells in the testis
One-variable word equations in linear time
In this paper we consider word equations with one variable (and arbitrary
many appearances of it). A recent technique of recompression, which is
applicable to general word equations, is shown to be suitable also in this
case. While in general case it is non-deterministic, it determinises in case of
one variable and the obtained running time is O(n + #_X log n), where #_X is
the number of appearances of the variable in the equation. This matches the
previously-best algorithm due to D\k{a}browski and Plandowski. Then, using a
couple of heuristics as well as more detailed time analysis the running time is
lowered to O(n) in RAM model. Unfortunately no new properties of solutions are
shown.Comment: submitted to a journal, general overhaul over the previous versio
Ab-initio calculations of the optical properties of the Si(113)3x2ADI surface
We investigated the stable silicon (113) surface with a 3x2ADI reconstruction
by ab-initio methods. The ground state properties have been obtained using the
density-functional theory. We present the dispersion of the electronic band
structure, where the surface bands have been distinguished from the projected
bulk bands by calculating their localization in the slab. The optical spectra,
here the reflectance anisotropy (RAS), have been obtained within the
independent particle random phase approximation. We identified surface features
in the spectra tracing them back to the responsible electronic states and,
studied their localization in the slab. A comparison with available
experimental data for the band structure and the RAS shows a good agreement.Comment: 10 pages, 10 figure
Studies of new antiferroelectric liquid crystal based on quantum-chemical model
Physical properties of new thermotropic antiferroelectric liquid crystal have been studied. Experiments were done by use of complementary methods such as differential scanning calorimetry, polarizing optical microscopy and X-ray powder diffractometry. Acquired data from X-ray powder diffractometry was examined under application of quantum chemical approach. It has been found that compound studied exhibits stable enantiotropic antiferroelectric SmC_{A}^{*} phase in the wide temperature range while ferroelectric phase SmC^{*} is very narrow
Time-Symmetrization and Isotropization of Stiff-Fluid Kantowski-Sachs Universes
It is shown that growing-entropy stiff-fluid Kantowski-Sachs universes become
time-symmetric (if they start with time-asymmetric phase) and isotropize.
Isotropization happens without any inflationary era during the evolution since
there is no cosmological term here. It seems that this approach is an
alternative to inflation since the universe gets bigger and bigger approaching
'flatness'.Comment: 9 pages, no figure
Boson Stars as Gravitational Lenses
We discuss boson stars as possible gravitational lenses and study the lensing
effect by these objects made of scalar particles. The mass and the size of a
boson star may vary from an individual Newtonian object similar to the Sun to
the general relativistic size and mass of a galaxy close to its Schwarzschild
radius. We assume boson stars to be transparent which allows the light to pass
through them though the light is gravitationally deflected. We assume boson
stars of the mass to be on non-cosmological distance from
the observer. We discuss the lens equation for these stars as well as the
details of magnification. We find that there are typically three images of a
star but the deflection angles may vary from arcseconds to even degrees. There
is one tangential critical curve (Einstein ring) and one radial critical curve
for tangential and radial magnification, respectively. Moreover, the deflection
angles for the light passing in the gravitational field of boson stars can be
very large (even of the order of degrees) which reflects the fact they are very
strong relativistic objects. We also propose a suitable formula for the lens
equation for such large deflection angles, and with the reservation that large
deflection angle images are highly demagnified but in the area of the
tangential critical curve, their existence may help in observational detection
of suitable lenses possessing characteristic features of boson stars which
could also serve as a direct evidence for scalar fields in the universe.Comment: accepted by Astrophys. J., 31 pages, AASTeX, 6 figure
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