The aim of this work consists of the evaluation of atmospheric pressure dielectric barrier discharges for the conversion of greenhouse gases into useful compounds. Therefore, pure CO 2 feed flows are administered to the discharge zone at varying discharge frequency, power input, gas temperature and feed flow rates, aiming at the formation of CO and O 2 . The discharge obtained in CO 2 is characterized as a filamentary mode with a microdischarge zone in each half cycle of the applied voltage. It is shown that the most important parameter affecting the CO 2 -conversion levels is the gas flow rate. At low flow rates, both the conversion and the CO-yield are significantly higher. In addition, also an increase in the gas temperature and the power input give rise to higher conversion levels, although the effect on the CO-yield is limited. The optimum discharge frequency depends on the power input level and it cannot be unambiguously stated that higher frequencies give rise to increased conversion levels. A maximum CO 2 conversion of 30% is achieved at a flow rate of 0.05 L min −1 , a power density of 14.75 W cm −3 and a frequency of 60 kHz. The most energy efficient conversions are achieved at a flow rate of 0.2 L min −1 , a power density of 11 W cm −3 and a discharge frequency of 30 kHz.

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The physics of plasmas containing positive and negative ions is discussed with special attention to the recently produced pair-ion plasma containing ions of equal mass and opposite charge. The effects of the density gradient in the direction perpendicular to the ambient magnetic field vector are discussed. The possible presence of electrons is discussed in the context of plasma modes propagating at an angle with respect to the magnetic field vector. It is shown that the electron plasma mode may become a backward mode in the presence of a density gradient, and this behavior may be controlled either by the electron number density or the mode number in the perpendicular direction. In plasmas with hot electrons an instability may develop, driven by the combination of electron collisions and the density gradient, and in the regime of a sound ions' response. In the case of a pure pair-ion plasma, for lower frequencies and for parameters close to those used in the recent experiments, the perturbed ions may feel the effects of the magnetic field. In this case the plasma mode also becomes backward, resembling features of an experimentally observed but yet unexplained backward mode.

A numerical parameter study has been performed for a cylindrical atmospheric pressure dielectric barrier discharge (DBD) in helium with nitrogen impurities using a two-dimensional time-dependent fluid model. The calculated electric currents and gap voltages as a function of time for a given applied potential are presented, as well as the number densities of the various plasma species. This study shows that for the geometry under consideration the applied voltage parameters have a large impact on the electric current profiles and that the discharge current is always determined by the electron and ion conduction currents while the displacement current is nearly negligible. A relative broadening of the current profiles (compared with the duration of the half cycle of the applied voltage) with an increase in the applied frequency is obtained. Nearly sinusoidal current wave forms, usually typical for radio frequency DBDs, are observed while still operating at the frequencies of tens of kilohertz. For the setup under investigation, the Townsend mode of the DBD is observed in the entire range of applied voltage amplitudes and frequencies. It is shown that the average power density dissipated in the discharge increases with rising applied voltage and frequency. An increase in applied voltage frequency leads to an increase in the electron density and a decrease in electron energy, while increasing the voltage amplitude has the opposite effect.

In all the three measured positions of the mandible with Angle Class II/2 malocclusion, bioelectrical activity was lowest at baseline and increased during the first year of treatment, and at the end of the treatment it partially reduced close to the approximate values in normal occlusion. Research on electromyographic activity of masticatory muscles is useful in everyday clinical practice, especially in present distinctive skeletal discrepancy before, during and after orthodontic treatment, if on the bases of the results we can evaluate the treatment, but also determine the start and duration of the retention period and retention device type.

Fetal pain remains a controversial subject both in terms of recognizing its existence and the time-frame within which it appears. This article investigates the hypothesis that pain perception during development is not related to any determined structures of the central nervous system (CNS), on the contrary, the process of perception could be made with any structure satisfying conditions that the perception of pain is the organization, identification, and interpretation of sensory information in order to represent and understand the environment. According to this definition, chronic decerebrate and decorticate experimental animals, anencephalic, and hydranencephalic patients demonstrate that the basic, most general, appropriate interaction with the environment can be achieved with a functional mesodiencephalon (brain stem, and diencephalon) as the hierarchically highest structure of the CNS during development. In intact fetuses, this structure shows signs of sufficient maturation starting from the 15th week of gestation. Bearing in mind the dominant role of the reticular formation of the brain stem, which is marked by a wide divergence of afferent information, a sense of pain transmitted through it is diffuse and can dominate the overall perception of the fetus. The threshold for tactile stimuli is lower at earlier stages of gestation. The pain inhibition mechanisms are not sufficiently developed during intrauterine development, which is another factor that leads to increased intensity of pain in the fetus. As a conclusion it could be proposed that the fetus is exposed to rudimentary painful stimuli starting from the 15th gestation week and that it is extremely sensitive to painful stimuli.

Over the past years, many scientific researches have been focused on thermo-sensitive hydrogels containing N-isopropylacrylamide (NIPAM) as a monomer. The NIPAM based hydrogels with 20 mol% 2-hydroxypropyl methacrylate (HPMet) were synthesized using ethylene glycol dimethacrylate as a cross-linker. The characterization of xerogel and phenacetin using FTIR spectra and SEM micrographs confirm the performed synthesis with satisfactory purity as well as loading of phenacetin into hydrogel. The swelling transport mechanism at simulated physiological conditions (pH 2.20 and 7.40 at 37°C) is described by the time-independent kinetics. The potential application of synthesized hydrogels for the controlled release of phenacetin as a model drug was investigated at simulated physiological conditions by HPLC method. [Acknowledgement. This work is part of the project MNTR TR-34012 financed by the Ministry of Education and Science of the Republic of Serbia. The authors are grateful for the support provided by the Ministry.

Serum copper values can be used as an indicator of some pathological pregnancies.