ABSTRACT
We have developed an optical stack of holographically formed polymer dispersed liquid-crystal (H-PDLC) devices that is fully operational with nonpolarized light sources. The device consists of two H-PDLC transmission gratings separated by a passive polarization rotator that can output a diffracted s-polarized, p-polarized, or s- and p-polarized beam simultaneously.
ABSTRACT
A theoretical model of a new electronically switchable grating design that uses a multilayer structure of an electro-optic (EO) material with an interdigitated-electrode type of array is proposed as an original technique for calculating the induced refractive index. It is shown that asymmetrical distribution of the electric field induces a slanted Bragg grating, which allows the slant angle to be switched electronically among more than two switching states. Parameters of the suggested design are calculated for a number of EO materials. A special case of frequency-based switching is anticipated for some polymer-dispersed liquid-crystal materials.
ABSTRACT
Cationic-induced two-photon photo-polymerization is demonstrated at 710 nm, using an isopropylthioxanthone / diarylidonium salt initiating system for the cationic polymerization of an epoxide. In-situ monitoring of the polymer conversion using interferometry allows for determination of the polymerization threshold J2th, polymerization rate R and its dependence of initiator's concentration z. Best J2th achieved is 1 GW/cm 2 , with a dynamic range of > 100, i.e. the material can be fully polymerized at intensities > 100 times the threshold level without damage. The R is found to be proportional to the m=1.7 power of the intensity, or R =[C(J-J2th)]m =[C(J-J2th)]1.7 , which implies a significantly stronger localization of the photochemical response than that of free radical photoinitiators. Both R and J2th significantly improve when the concentration z of the initiator (onium salt) increases, reduction of J2th exhibiting z -m trend.
ABSTRACT
We demonstrate for the first time two-photon induced holographic recording at an arbitrary point in three dimensional photopolymeric cube by overlapping two coherent pulses from a 200 femtosecond Ti: Sapphire tunable laser operating at 710 nm. Spatial overlap is achieved by a novel pupil division method. The polymer material is made of epoxy host, which is fully polymerized and filled with liquid photopolymerisable formulation comprising acrylate type monomer and two-photon photoinitiator. Measured diffraction efficiency is measured to be 3.5%.
ABSTRACT
: Correction to References. Commercial codes of the chemicals are added.
ABSTRACT
A new technological approach makes fabrication of relief computer-generated focusing elements for IR radiation by use of a dry photopolymer recording material possible. The formation of a relief structure by self-development takes place in the dark, subsequent to the holographic illumination, without wet processing. Consequently these diffractive elements exhibit low surface scattering. The formation of a surface wave of the monomer along the light-darkness boundary is observed for the first time to our knowledge and confirms the previously proposed thermodynamic model of the mechanism of the hologram formation in photopolymerizable layers. Dye-sensitized polymerization of acrylamide is found to produce nonlinearity of the relief recording. At least partial compensation of this nonlinearity is attained by the introduction of appropriate corrections into the computer-generated amplitude function. A diffraction efficiency of ~ 55% is obtained for CO(2) laser radiation (λ = 10.6 µm).
ABSTRACT
"The article defines the place of the Southern Ukraine in the migratory process of...post-reform Russia in the second half of the 19th century. Official and unwarranted colonization of the Southern Ukraine and its influence on an increase in the number of population and dynamics of its natural reproduction are analyzed." (SUMMARY IN ENG)
Subject(s)
Population Dynamics , Population Growth , Demography , Developed Countries , Emigration and Immigration , Europe , Europe, Eastern , Population , USSR , UkraineABSTRACT
A method for assessing cytotoxicity in cell-mediated cytolysis as well as in reactions of natural killing and antibody-dependent cellular cytotoxicity through assaying the total esterolytic activity of serine proteinases (TEASP) is both sensitive and specific. TEASP levels in all cytotoxic tests correlated with the percentage of lysis of 51Cr-labelled target cells. The method permits the differential assessment of endoproteases in both the effector cell and the target cell.
