Preparation of copolymers of p-Isopropenylcalix[8]arene and Styrene

Summary p-Isopropenylcalix[n]arenes are useful building blocks for the design of novel polymer architectures. This paper is the first report on copolymerization of p-isopropenylcalix[8]arene and styrene by free radical polymerization. An extensive study on the optimization of the reaction conditions (especially monomer to initiator ratio, initiator concentration, and duration of the process) was performed in order to prepare high molecular weight copolymers in good yield. Homopolymerizations were also carried out for comparison. The products obtained by homopolymerization of the monomers and their copolymerization were fractionated and each fraction was characterized by chromatographic (GPC and HLPC) and spectroscopic methods as UV, IR and ¹H NMR and analytical methods. Considering the molecular weight, spectroscopic and analytical data the most probable structure of the copolymer was proposed. Extraction of metal picrates from water into organic solvent was used to evaluate the ion binding capabilities of p-isopropenylcalix[8]arenestyrene and O-acetylated p-isopropenycalix[8]arenestyrene copolymers.     

Frequency and Timing Offset Estimation Using Single Reference Symbol

In this paper we will investigate the performance of an estimator employing single OFDM reference symbol for timing and frequency offset estimation. We will show how both coarse and fine frequency offset estimation can be performed with this single OFDM reference symbol. The performance of this estimator will be compared with the ML estimator employing OFDM reference symbols of different length for coarse and fine frequency offset estimation. It will be shown that, unlike ML estimator, the estimation range of the analyzed estimator is not constrained.     

Hologram reconstruction corrected for measurements through layers with different refractive indices in digital in-line holographic microscopy

Digital in-line holographic microscopy (DIHM) using point sources has been shown to be a versatile technique, especially for three-dimensional tracking of particles or microorganisms. However, the spherical source wave is altered when measurements are performed through layers with different refractive indices, such as water cuvettes. The situations where a layer of medium with a refractive index different than that of the predominant surrounding propagation medium (usually air) is situated behind or in front of the plane to be reconstructed are analyzed in detail, and a general approach for reconstruction under such circumstances is developed. The proposed refractive index correction is tested experimentally and compared to conventional reconstruction algorithms. Using 3D traces of swimming algal spores, the influence on the velocity calculation is also shown.     

Forward Adaptive Logarithmic Quantizer with New Lossless Coding Method for Laplacian Source

The aim of this paper is to improve the G.711 standard, which is widely used, especially in the public switched telephone network (PSTN). Two solutions are proposed. The first solution uses only lossless coder, achieving a bit-rate decrease of 0.82 bits/sample, compared to the G.711 codec. The second solution uses forward adaptation and a lossless coder, further decreasing the bit-rate (by 1.25 bits/sample) and achieving higher average signal-to-quantization noise ratio (SQNR) in comparison with the G.711 codec. Also, the second solution is more robust than the G.711 codec, which means that it has near constant SQNR for a wide range of input signal power. That is very important for signals whose input power varies with time, such as speech and video signals. Our solutions are compatible with the G.711 codec, they have little additional complexity and delay and therefore can be applied in real-time systems, such as PSTN or VoIP. They can also be used in many other systems, such as WiMax and OFDM, as a replacement or improvement of the G.711 codec. Standardization process of the G.711.1 standard (which is a wide-band extension of the G.711 standard) is largely present. Our solutions fulfill all the requirements for that new standard; therefore they can be implemented in its low-frequency part.     

The influence of an organosulfonate on the reaction between Ellman's reagent and thiocholine

The aim of this work was to elucidate the effect of methanesulfonyl fluoride on the detection reaction for the determination of cholinesterase activity. The effect of methanesulfonyl fluoride was studied by monitoring the time course of the appearance and disappearance of the detection reaction product using a stopped-flow technique. The obtained experimental data were analyzed by progress curve analysis. It was found that the effect of methanesulfonyl fluoride results from a reaction between methanesulfonyl fluoride and the detection reaction product with the following rate constant: k1 = 5.33 x 10(-2) M-1s-1. In evaluating the effect of methanesulfonyl fluoride, the decomposition of this agent in water was included in the analysis because the decomposition considerably affected the reaction between methanesulfonyl fluoride and the product. The corresponding rate constant was found to be k2 = 4.9 x 10(-5) M-1s-1.     

Design of product polar quantizers for A/D conversion of measurement signals with Gaussian distribution

In this paper, a design of product polar quantizers for A/D (analog-to-digital) conversion of measurement signals and an analysis of their performances in the wide range of variances are considered, in a general manner, i.e. for any compression function. Special attention is devoted to the design of robust product polar quantizers, applying the developed theory on μ-law logarithmic compression function, which is very important since a lot of measurement signals are nonstationary. The proposed quantizers achieve much better performances than scalar quantizers (they have higher the maximal SQNR (signal-to-quantization noise ratio) for about 2.5 dB and they are more robust), without increasing of complexity. Theory is proved by simulation. These quantizers can be applied for many different types of measurement signals and can be used in many measurement systems (telemetry, telemedicine, wireless sensor networks, etc.).     

A numerical investigation of the refrigerant maldistribution from a header towards parallel channels in an evaporator of automotive air conditioning system

Evaporators in automotive air conditioning are designed as compact heat exchangers with the aim to cool outside air for the widest possible range of weather conditions. Under low operating loads a non-uniformity of the refrigerant liquid and gas phase distribution from the evaporator headers towards the evaporating channels leads to a decrease of the evaporator efficiency and a temperature stratification in the exit stream of cooled air. This malfunction is investigated by numerical simulations and analyses with the Computational Multi-Fluid Dynamic code. The applied numerical approach is validated for available experimental conditions. In order to eliminate the air exit temperature stratification, numerical experiments are performed with design changes of the evaporator header and the effectiveness of applied measures is demonstrated.     

Determinization of fuzzy automata with membership values in complete residuated lattices

In this paper we introduce a new method for determinization of fuzzy finite automata with membership values in complete residuated lattices. In comparison with the previous methods, developed by Bělohlávek [R. Bělohlávek, Determinism and fuzzy automata, Information Sciences 143 (2002), 205-209] and Li and Pedrycz [Y.M. Li, W. Pedrycz, Fuzzy finite automata and fuzzy regular expressions with membership values in lattice ordered monoids, Fuzzy Sets and Systems 156 (2005), 68-92], our method always gives a smaller automaton, and in some cases, when the previous methods result in infinite automata, our method can result in a finite one. We also show that determinization of fuzzy automata is closely related to fuzzy right congruences on a free monoid and fuzzy automata associated with them, and in particular, to the concept of the Nerode’s fuzzy right congruence of a fuzzy automaton, which we introduce and study here.