Synthesis of carbohydrate-saccharin conjugates

The synthesis of some carbohydrate-saccharin conjugates has been achieved by treatment of sugar derivatives containing “isolated” hydroxyl groups with equimolar amounts of saccharin, diethyl azodicarboxylate, and triphenylphosphine. Both C-N-linked and C-O-linked compounds can be obtained.     

Riesz–Jacobi Transforms as Principal Value Integrals

We establish an integral representation for the Riesz transforms naturally associated with classical Jacobi expansions. We prove that the Riesz–Jacobi transforms of odd orders express as principal value integrals against kernels having non-integrable singularities on the diagonal. On the other hand, we show that the Riesz–Jacobi transforms of even orders are not singular operators. In fact they are given as usual integrals against integrable kernels plus or minus, depending on the order, the identity operator. Our analysis indicates that similar results, existing in the literature and corresponding to several other settings related to classical discrete and continuous orthogonal expansions, should be reinvestigated so as to be refined and in some cases also corrected.     

Application of the novel dynamic thermo-optical analysis for identification of the sequence of mesophases in thermotropic liquid crystal

Identification of mesophases using a polarising microscope is vital in the area of research and development of the liquid crystal (LC) materials, however, sometimes it is very difficult to distinguish one texture from another. Here, we propose a novel method allowing for the examination of thermotropic phase sequence in polymorphic LCs called dynamic thermo-optical analysis (DTOA). In the DTOA technique the LC subjected to the cooling process is simultaneously influenced by the electric field varying sinusoidally with time. It results in the dynamic changes in the light intensity passing through the layer of such LC observed under a polarised microscope and recorded by a charge-coupled device camera. The magnitude of the changes uniquely depends on the type of the mesophase. The subsequent numerical analysis of the recorded movie (performed with a help of the image-processing software) reveals the changes in the amplitude of the average intensity of the images of the respective textures, i.e. nematic, SmA, SmC, SmI, thereby allowing for their clear identification. Furthermore, the DTOA allows to distinguish easily the SmA from the SmC phase. The azobenzene-based LC known of rich sequence of mesophases has been used here to demonstrate the principle of the DTOA method.     

Theoretical study of hydrogenated tetrahedral aluminum clusters

We report on the structures of aluminum hydrides derived from a tetrahedral aluminum (Al₄) cluster using ab initio quantum chemical calculation. Our calculation of binding energies of the aluminum hydrides reveals that stability of these hydrides increases as more hydrogen atoms are adsorbed, while stability of Al – H bonds decreases. We also analyze and discuss the chemical bonds of those clusters by using recently developed method based on the electronic stress tensor. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

A novel circuit for independent control of electron energy and emission current of a hot cathode electron source

The implementation of a non-linear combination of two reference voltages to control the anode voltage in the previously described biasing system of an electron source with a hot cathode allows elimination of the correlation between the emission current and the accelerating voltage. The presented system is highly suitable for applications in electron-impact mass spectrometers, ionization gauges and other instruments (for example, electron microscopes).     

Preparation and optical properties of novel bioactive photonic crystals obtained from core-shell poly(styrene/α-<Emphasis Type="Italic">tert</Emphasis>-butoxy-ω-vinylbenzyl-polyglycidol) microspheres

Optical properties of polymer microspheres with polystyrene cores and polyglycidol-enriched shells poly(styrene/α-tert-butoxy-ω-vinylbenzyl-polyglycidol) (P(S/PGL) particles with number average diameters D _n determined by scanning electron microscopy equal 237 and 271 nm), were studied before and after immobilization of ovalbumin. The particles were synthesized by emulsifier-free emulsion copolymerization of styrene and polyglycidol macromonomer (poly(styrene/α-tert-butoxy-ω-vinylbenzyl-polyglycidol)) initiated with potassium persulfate. Molar fraction of polyglycidol units in the interfacial layer of the microspheres determined by XPS was equal 42.6 and 34.0%, for the particles with D _n equal 137 and 271 nm, respectively. Colloidal crystals from the aforementioned particles were prepared by deposition of particle suspensions on the glass slides and subsequent evaporation of water. It was found that optical properties of colloidal crystals from the P(S/PGL) microspheres strongly depend on modification of their interfacial layer by covalent immobilization of ovalbumin. The coating of particles with ovalbumin resulted in decreasing their refractive index from 1.58 to 1.52.     

Characterization of a Transformation Function of a Photochromic Adaptive Filter

Simple, fast and accurate procedure is developed for measuring a Transformation Function (TF) of a Photochromic Adaptive Filter (PAF). Photochromic filters, whose spectral transmittance depends on previous and immediate radiant exposure and other environmental conditions, require special methods of spectro-photometry to determine their properties. This article describes methodology of characterizing the luminous transmittance as a function of light intensity using easy to implement method. Transformation functions of sample filters for different sources of radiation and varied light intensity are evaluated. The measuring system can also be used for fast determination of spatially and spectrally uniform light sources with UV spectral component.     

Maximizing power yield in energy systems - A thermodynamic synthesis

We present a synthesizing thermodynamic approach to modeling and power maximization in various energy converters, such as thermal, solar and chemical engines and fuel cells. Static and dynamical systems are investigated. Thermodynamic analyses lead to converters’ efficiencies in terms of propelling fluxes. Efficiency equations are applied to find maximum power points in static systems. These efficiency equations are also applied to determine maxima of integrated power (work) in dynamical systems, which work with upgrading and downgrading of a resource medium. While optimization of static systems requires using of differential calculus and Lagrange multipliers, dynamic optimization involves variational calculus and dynamic programming. In reacting mixtures balances of mass and energy are applied to derive power yield in terms of an active part of chemical affinity. Power maximization approach is finally applied for fuel cells treated as flow engines driven by fluxes of chemical reagents and electrochemical mechanism of electric current generation. The efficiency decrease is linked with thermodynamic and electrochemical irreversibilities expressed in terms of polarizations (activation, concentration and ohmic). Maximum power data provide bounds for SOFC energy generators, which are more exact and informative than reversible bounds for electrochemical transformation.