Application of a New Potentiometric Sensor for Determination of Anionic Surfactants in Wastewater

A new screen-printed potentiometric microsensor (SPMS) for the determination of anionic surfactants (ASs) based on the dimethyldioctadecylammonium-tetraphenylborate (DDA-TPB) ion pair as a sensing material was applied to real industrial effluents. The sensor is accurate, inexpensive, simple and very sensitive. The solutions of cetylpyridinium chloride (CPC) of the concentrations down to 5· 10–5 mol dm–3 were used as a titrant. Standard addition method was used for checking the precision and accuracy of measurements providing satisfactory results with recoveries between 98.3 to 102.0 % in pure AS solutions and 99.0 to 114.5 % in wastewater. Standard spectrophotometric method Methylene Blue Active Substances (MBAS) was used as control for comparison of the results obtained with the new sensor. The results obtained using SPMS were compared with those obtained by the polymeric membrane ion-selective electrodes (ISEs), containing the same sensing material, and exhibited good mutual agreement

Positron and positronium annihilation patterns in zeolites and bulk ceramics

Positron lifetime (LT) measurements have revealed that in porous media the annihilation pattern is probably dominated by a near-saturation level trapping both for the positron and the positronium as well, which masks the contribution from the ldquofree annihilationrdquo, i.e., annihilation from delocalised positrons. In this work we compare positron lifetime spectra of crystalline zeolites with bulk ceramic materials fabricated by sintering from the same constituents as the zeolites and analyse common features and differences between them. For the dense ceramic samples the contribution from long-living components to the annihilation pattern is substantially lower than that for the zeolites. The results are analysed with the aim to extract new knowledge for the zeolites and for the sensitivity limits for free volume studies in ceramics. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Vertebral Artery Hypoplasia – Sex-Specific Frequencies in 36 Parent-Offspring Pairs

The major interest in vertebral artery (VA) hypoplasia comes from its possible connection to migraines with aura as well as from the fact that it is one of the risk factors for a stroke. Therefore, the aim of this preliminary study was to investigate the mode of inheritance of VA hypoplasia. Initially, color Doppler of VA was performed in 64 firstand second-degree relatives of 33 probands, and the presence of VA hypoplasia was confirmed according to the already established criteria. Since a higher prevalence of VA hypoplasia (15.6%) in probands’ relatives in comparison with 2.34% in the general population of Croatia was indicative of a strong familial predisposition for this condition, an analysis of family data by means of Pearson’s chi-square statistics has been performed. In this analysis, the observed sex-specific frequencies of 36 parent-offspring pairs composed only of affected parent and his/her (affected or non-affected) offspring are compared to the frequencies as expected under eight proposed models. For both – autosomal and X-linked monogenetic inheritance – four hypotheses have been chosen, assuming that the individuals having the affected allele (in combination with a healthy one) have 100%, 50%, 40% and 0% chances of developing VA hypoplasia. Out of eight tested models only two – completely dominant and completely recessive X-linked models – were rejected. But, from the six non-rejected models, goodness-of-fit statistics showed that the hypothesis of X-linked inheritance of VA hypoplasia with the »healthy« allele being stronger (60% effect on phenotype) – almost perfectly fit the data ( 2 = 2.0023; df = 7; p = 0.9597). Further research encompassing a more enlarged family sample is needed to confirm the present findings

High Chern number van der Waals magnetic topological multilayers MnBi2_2Te4_4/hBN

Chern insulators are two-dimensional magnetic topological materials that conduct electricity along their edges via the one-dimensional chiral modes. The number of these modes is a topological invariant called the first Chern number $C$, that defines the quantized Hall conductance as $S_{xy}= C e^2/h$. Increasing $C$ is pivotal for the realization of low-power-consumption topological electronics, but there has been no clear-cut solution of this problem so far, with the majority of existing Chern insulators showing $C=1$. Here, by using state-of-the-art theoretical methods, we propose an efficient approach for the realization of the high-$C$ Chern insulator state in MnBi$_2$Te$_4$/hBN van der Waals multilayer heterostructures. We show that a stack of $n$ MnBi$_2$Te$_4$ films with $C=1$ intercalated by hBN monolayers gives rise to a high Chern number state with $C=n$, characterized by $n$ chiral edge modes. This state can be achieved both under the external magnetic field and without it, both cases leading to the quantized Hall conductance $S_{xy}= C e^2/h$. Our results therefore pave way to practical high-$C$ quantized Hall systems.Comment: 10 pages, 5 figure

Recoil polarization and beam-recoil double polarization measurement of \eta electroproduction on the proton in the region of the S_{11}(1535) resonance

The beam-recoil double polarization P_{x'}^h and P_{z'}^h and the recoil polarization P_{y'} were measured for the first time for the p(\vec{e},e'\vec{p})\eta reaction at a four-momentum transfer of Q^2=0.1 GeV^2/c^2 and a center of mass production angle of \theta = 120^\circ at MAMI C. With a center of mass energy range of 1500 MeV < W < 1550 MeV the region of the S_{11}(1535) and D_{13}(1520) resonance was covered. The results are discussed in the framework of a phenomenological isobar model (Eta-MAID). While P_{x'}^h and P_{z'}^h are in good agreement with the model, P_{y'} shows a significant deviation, consistent with existing photoproduction data on the polarized-target asymmetry.Comment: 4 pages, 1 figur