Study on Combined Optical and Electrochemical Analysis Using Indium‐tin‐oxide‐coated Optical Fiber Sensor

In this work an optical fiber sensor, where a lossy‐mode resonance (LMR) effect was obtained due to indium tin oxide (ITO) thin overlay, has been simultaneously applied as a working electrode in a 3‐electrode cyclic voltammetry electrochemical setup. Since LMR conditions highly depend on refractive index of a surrounding medium, an LMR‐based sensor was applied for optical investigations of electrolyte's properties at the ITO surface. We have found that the optical response of the sensor highly depends on the applied potential and its changes, as well as the properties of the investigated electrolyte, i. e., its composition and presence of a redox probe. Both optical and electrochemical response of the ITO‐LMR sensor to various concentrations of phosphate‐buffered saline (PBS), NaCl and Na₂SO₄, as well as scan rate were investigated and discussed. We have found that the responses in optical and electrical domains differ significantly and may deliver supplementary information about the investigated analyte.     

Covering of nanometric calcite with α-cyclodextrin

In the present experiments, the monodisperse calcium carbonate nanoparticles obtained in the reactor (three-phase reaction) with rotating discs have been covered with α-cyclodextrin. Both pure CaCO₃ nanoparticle and α-cyclodextrin-coated CaCO₃ powders were deeply analysed by the use of the scanning electron microscope, the dynamic light scattering and the thermogravimetric method. The experimental data have allowed for determination of effective diameter of the obtained particles (aggregates of ca. 30 nm single crystals) and their size distribution (almost monodisperse—ca. 390 nm) as well as for distinction between α-cyclodextrin molecules present on calcite surface or free α-cyclodextrin molecules if presented in the sample. It was found that the nanometric CaCO₃ obtained in the reactor with rotating discs can be covered with a maximum of 1.15% α-cyclodextrin monolayer. The maximal coverage of the CaCO₃ calcite particles with α-cyclodextrin can be done by 24-h shaking of 50 mg nanometric calcium carbonate with 25 mg of 36.79 mM α-cyclodextrin aqueous solution.

     

Hydroxy lactones with the gem-dimethylcyclohexane system – Synthesis and antimicrobial activity

Two new lactones comprising the gem-dimethylcyclohexane ring: 2-chloro-5,5-dimethyl-9-oxabicyclo[4.3.0]nonan-8-one and 2-bromo-5,5-dimethyl-9-oxabicyclo[4.3.0]nonan-8-one as well as the already known 2-iodo-5,5-dimethyl-9-oxabicyclo[4.3.0]nonan-8-one, were obtained from (6,6-dimethylcyclohex-2-en-1-yl)acetic acid. These lactones were used as substrates for the screening of biotransformation by whole cells of nine fungal strains (Fusarium species, Syncephalastrum racemosum and Cunninghamella japonica). Some of these microorganisms (mainly Fusarium species) transformed all three lactones during the hydrolytic dehalogenation into 2-hydroxy-5,5-dimethyl-9-oxabicyclo[4.3.0]nonan-8-one. It is worth noting that two microorganisms (Fusarium culmorum and Fusarium scirpi) converted iodolactone with very high enantioselectivity (75.1% and 91.6%, respectively). The (+) isomer of hydroxy lactone was preferred. At the last step the hydroxy lactone obtained during biotransformation was examined for its biological activity against bacteria, yeasts and fungi. It was found that this compound inhibits growth of some tested microorganisms.     

Heat kernels on metric spaces and a characterisation of constant functions

Using the Dirichlet forms theory, we prove that when the locally compact measure metric space (X,,m) is the state space of a Markov process with transition density p(t,x,y) bounded from the above by where is a function satisfying certain integrability condition, then the following statement holds: when u L²(X) and then u is a constant function.This work is partially supported by a KBN grant no. 2-PO3A-028-22.Mathematics Subject Classification (2000): primary 60J35, secondary 46E35     

The surface tension and density of the Cu-Ag-In alloys

The surface tension and the densities of the Cu-Ag-In alloys have been measured by means of the sessile drop method. The density of these alloys depends linearly on temperature in the case of all the investigated compositions. The surface tension shows a linear dependence on temperature except for the lowest temperatures. For most of the alloys, the surface tension at the lowest temperature is lower than that predicted by the straight line. The experimental values of the surface tension of the Cu-Ag-In alloys are compared with those computed from the model, and quite good agreement is observed.     

Nonlinear effects in photonic crystal fibers filled with nematic liquid crystals

We have investigated the nonlinear propagation of light in photonic crystal fibers filled with nematic liquid crystals. We analyzed a configuration with a periodic modulation of the refractive index corresponding to a matrix of waveguides. Matrices of coupled waveguides allow observing a variety of new phenomena both for low power light beam propagation and with an existence of nonlinear effects. The opportunity for the creation of solitary waves caused by the interplay between diffraction and nonlinear effects in these kinds of fibers is investigated. At low power the propagating light beam spreads as it couples to more and more waveguides. When the intensity is increased the light modifies the refractive index distribution, inducing a defect in the periodic structure. The creation of such a defect can lead to a situation in which the light becomes self-localized and its diffractive broadening is eliminated. Eventually, in the case of positive Kerr-type nonlinearity, a discrete soliton can be created. In the case of negative nonlinearity the refractive index decreases with the optical power and can lead to bandgap shifting. The incident beam, with a frequency initially within the bandgap, is then turned outside the bandgap resulting in the changing of the propagation effect for the discrete diffraction effect. As a consequence the delocalization of the light can be observed. Presented at 9-th International Workshop on Nonlinear Optics Application, NOA 2007, May 17–20, 2007, Świnoujscie, Poland     

13C CP MAS NMR and GIAO-CHF calculations of coumarins

13C cross-polarization magic-angle spinning NMR spectra were recorded for a series of solid coumarins. Ab initio calculations of shielding constants were performed with the use of GIAO-CHF method. The combined CPMAS NMR and theoretical approach was successful in characterizing solid-state conformations of coumarins; a relationship sigma (ppm) = -1.032 xdelta + 205.28 (R(2) = 0.9845) can be used to obtain structural information for coumarins, for which solid-state NMR or crystal structure data are not available.     

Computer simulation and optimization of preparative thin-layer chromatography under conditions of isocratic and stepwise gradient elution

Summary An equilibrium sandwich chamber for continuous thin-layer chromatography was used to study overloaded systems. Mixtures of two or three dyes were used as the model samples, and wide starting zones were formed (volume-overloaded systems). The movement of the zones was recorded during continuous elution. The effect of sample volume and the mode of development (isocratic or gradient) on the maximum separation yield was investigated. A computer program was developed for the calculation of the final R_F values for the front and rear edges of the bands.Satisfactory agreement was found between the experimental R_F values of zone boundaries and the values predicted by computer simulation.Presented at the 2nd International Symposium on Preparative and Up-Scale Liquid Chromatography, February 1–3, 1988, Baden-Baden (FRG).     

Functional derivative δE/δρ in calculation of chemical potential for the Kohn–Sham electronic system

A method for finding the chemical potential for an electronic system with density ρ = Σ_ρi represented within the Kohn–Sham approximation is proposed. To find the chemical potential of the system under consideration, we propose to refer to the definition μ = δE/δ_ρ and to apply the mathematical properties of functional derivatives. Particularly, in the case examined, the result μ = μ( r ) ≠ const has been obtained, which may be explained in the framework of the calculus of variation. Taking the limit lim_r→∞ μ( r ) as the best approximation to the proper equilibrium chemical potential of a free atom, one obtains μ = ?I, where I denotes first ionization energy. A possibility of further applications of the proposed method in relation to crystalline systems is also discussed. © 1994 John Wiley & Sons, Inc.     

The Synthetic Utility of Amide and Amidine Derivatives Containing Polycarbonyl Moieties in the Synthesis of β-Aminoenones

Summary.  The application of derivatives of the easily decomposing weak bases formamide, semicarbazide, urea, or formamidine in the synthesis of β-aminoenones is described. These compounds readily undergo transamination with strong bases, thus opening the way to various heterocyclic compounds. Received July 16, 2001. Accepted (revised) September 17, 2001