Thermal study of the Ce<Subscript>0.9</Subscript>Tb<Subscript>0.1</Subscript>O<Subscript>2</Subscript> pigment prepared by different synthesis

The inorganic ceramic compounds based on the CeO₂ belong into the group of high-temperature pigments. The pigments have been prepared by the classical dry process (i.e. solid-state reaction) in the temperature range from 1,300 to 1,600 °C and by the coprecipitation at the three different temperatures: 400, 600 and 1,100 °C. The principal of these pigments makes the host lattice of the CeO₂, which is doped by terbium ions. This incorporation of the doped ions leads to obtaining of the interesting dark orange colour after application into ceramic glaze. The aim of our research was to improve and optimize the synthesis conditions of these pigments. The samples were submitted to thermal analysis (TG–DTA) for determination of the temperature interval of the pigment formation and the thermal stability of pigments. The compounds were also measured from the point of view of their colouring, structure and particle size distribution.     

Detection of quorum sensing molecules in Burkholderia cepacia culture supernatants with enzyme-linked immunosorbent assays

The Burkholderia cepacia complex (Bcc) employs a quorum sensing (QS) mechanism which is a cell density-dependent bacterial communication system to regulate certain gene expressions. As with many other Gram-negative bacteria, Burkholderia cepacia species use (N-acyl-)homoserine lactones (AHLs or HSLs) as signalling molecules. Because of the essential role of QS in bacterial behavior, the aim of this study was to demonstrate the applicability of our in-house-developed enzyme-linked immunosorbent assays (ELISAs) for the detection of bacterial activities via HSLs in B. cepacia strain LA3 culture supernatants. For this purpose the previously developed monoclonal antibodies (mAbs) HSL1/2-2C10 and HSL1/2-4H5 were exploited. N-3-Oxo-decanoyl-L-homoserine lactone (3-oxo-C10-HSL) was used as main analyte throughout all experiments. With the bacterial culture medium (named ABC medium) a matrix effect in both ELISAs was visible (slight increase in optical density, shift in test midpoints (IC₅₀) and working ranges). For example, ELISA with mAb HSL1/2-2C10 and enzyme tracer HSL3-HRP (HSL derivative conjugated to horseradish peroxidase) had an IC₅₀ of 120 μg L⁻¹ for 3-oxo-C10-HSL in phosphate-buffered saline versus 372 μg L⁻¹ in ABC medium. A significant increase of HSLs in B. cepacia strain LA3 culture supernatants after 12 h to 48 h of growth was observed. Although the analytical result of these immunoassays cannot distinguish HSLs from homoserines (HSs), the appearance of these compounds can be easily followed. Hydrolysis and spiking experiments were carried out with these biological samples. According to our knowledge, these are the first immunoassays for the detection of quorum sensing molecules in biological culture supernatants. This study provides a cost-effective, fast, and sensitive analytical method for detection of HSLs/HSs in biological samples without complex sample preparation and will offer a quick idea about B. cepacia activities. The low sample amount requirement (less than 1 mL) constitutes a tremendous advantage for many analytical questions with biological samples.     

DTI at 7 and 3 T: systematic comparison of SNR and its influence on quantitative metrics

Diffusion tensor imaging (DTI) and advanced related methods such as diffusion spectrum and kurtosis imaging are limited by low signal-to-noise ratio (SNR) at conventional field strengths. DTI at 7 T can provide increased SNR; however, B0 and B1 inhomogeneity and shorter T2? still pose formidable challenges. The purpose of this study was to quantify and compare SNR at 7 and 3 T for different parallel imaging reduction factors, R, and TE, and to evaluate SNRs influences on fractional anisotropy (FA) and apparent diffusion coefficient (ADC). We found that R>4 at 7 T and R≥2 at 3 T were needed to reduce geometric distortions due to B0 inhomogeneity. For these R at 7 T, SNR was 70-90 for b=0 s/mm² and 22-28 for b=1000s/mm² in central brain regions. SNR was lower at 3 T (40 for b=0 s/mm² and 15 for b=1000 s/mm²) and in lateral brain regions at 7 T due to B1 inhomogeneity. FA and ADC did not change with MRI field strength, SENSE factor or TE in the tested range. However, the coefficient of variation for FA increased for SNR <15 and for SNR <10 in ADC, consistent with published theoretical studies. Our study demonstrates that 7 T is advantageous for DTI and lays the groundwork for further development. Foremost, future work should further address challenges with B0 and B1 inhomogeneity to take full advantage for the increased SNR at 7 T.     

Multi-dimensional scalar balance laws with discontinuous flux

We consider scalar balance laws with a dissipative source term. The flux function may be discontinuous with respect to both the space variable x and the unknown quantity u. We formulate the definition of entropy weak solutions and provide existence and uniqueness to the considered problem. The problem is formulated in the framework of multi-valued mappings. The notion of entropy measure-valued solutions is used to prove the so-called contraction principle and comparison principle.     

Operator splitting for dissipative delay equations

Operator splitting methods for a special class of nonlinear partial differential equations with delay are investigated. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

A class of quasi-variational inequalities for adaptive image denoising and decomposition

We introduce a class of adaptive non-smooth convex variational problems for image denoising in terms of a common data fitting term and a support functional as regularizer. Adaptivity is modeled by a set-valued mapping with closed, compact and convex values, that defines and steers the regularizer depending on the variational solution. This extension gives rise to a class of quasi-variational inequalities. We provide sufficient conditions for the existence of fixed points as solutions, and an algorithm based on solving a sequence of variational problems. Denoising experiments with spatial and spatio-temporal image data and an adaptive total variation regularizer illustrate our approach.     

Elimination Voltammetry of Miniaturized Mercury Drop Electrodes

Elimination voltammetry with linear scan (EVLS) in connection with renewed mini‐ drop mercury electrodes provides valuable information about the character and kinetics of processes at electrode/electrolyte interfaces. Based on the experiment related to the hydrogen evolution, it is presented that the EVLS is more sensitive than other voltammetric methods. Using miniaturized mercury electrodes, the EVLS is capable of detecting the effect of spherical diffusion associated with both the scan rates and the size of an electrode drop.