Development of new dominant selectable markers for the nonconventional yeasts Ogataea polymorpha and Candida famata

Nonconventional yeast Candida famata and Ogataea polymorpha are interesting organisms for basic and applied studies. O. polymorpha is methylotrophic thermotolerant yeast capable of xylose alcoholic fermentation whereas C. famata is capable of riboflavin overproduction. Still, the new tools for molecular research of these species are needed. The aim of this study was to develop the new dominant selective markers for C. famata and O. polymorpha usable in metabolic engineering experiments. In this work, the BSD gene from Aspergillus terreus coding for blasticidin S deaminase, O. polymorpha AUR1 gene required for sphingolipid synthesis and IMH3 gene, which encodes IMP dehydrogenase, were tested as the new dominant selective marker genes. Our results showed that AUR1 and IMH3 genes could be used as dominant selective markers for O. polymorpha with frequencies of transformation of 40 and 20 transformants per microgram of DNA, respectively. The IMH3 gene was successfully used as the marker for construction of O. polymorpha strains with increased ethanol production from xylose due to overexpression of TAL1, TKL1 and AOX1 genes. The BSD gene from A. terreus, conferring resistance to blasticidin, was found to be efficient for selection of C. famata transformants.     

C60 and C60-arginine aqueous solutions: In vitro toxicity and structural study

Abstract

Small-angle X-ray and neutron scattering was applied for the structural characterization of aggregates in water dispersions of fullerene C₆₀ prepared by dialysis method and its conjugate with amino acid arginine. Two compounds are also compared with respect to their toxic properties. Experiments on the cytotoxicity of these systems on the A549, HepG2 and HeLa cells showed no toxic effects of the dispersions.     

Comment on“Hole-pinned defect-dipoles induced colossal permittivity in Bi doped SrTiO3ceramics with Sr deficiency”

With this contribution,as a comment to the publication in Journal of Mate rials Science&Technology 44(2020)54,reporting giant dielectric response,structural characterization and numerical simulations in Sr_(1-1.5 x)Bi_xTiO₃ceramics,we show that the re ported results are rather contradicting and not well analysed,while the suggested mechanism for the giant permittivity response is not valid or doubtful and has to be reconsidered.Moreover,many details and data are missing making impossible not only to call the obtained results very suitable for practical application but even to reproduce them.     

Environmental and individual exposure to secondhand aerosol of electronic cigarettes in confined spaces: Results from the TackSHS Project†

Secondhand electronic cigarette (e-cigarette) aerosol (SHA) might impair indoor air quality and expose bystanders. This study aims to investigate exposure to SHA in controlled conditions of enclosed settings simulating real-world scenario. An experiment was performed in a car and in a room, in which SHA was generated during a 30-minute ad libitum use of an e-cigarette. The experiment was replicated on five consecutive days in each setting. We measured PM_2.5, airborne nicotine concentrations, and biomarkers of exposure to SHA, such as nicotine metabolites, tobacco-specific nitrosamines, propylene glycol, and glycerol in bystanders’ saliva samples before, during, and after the exposure period. Self-reported health symptoms related to exposure to SHA were also recorded. The results showed that the highest median PM_2.5 concentration was recorded during the exposure period, being 21 µg/m³ in the room setting and 16 µg/m³ in the car setting—about twofold increase compared to the baseline. Most concentrations of the airborne nicotine and all biomarkers were below the limit of quantification in both settings. Bystanders in both settings experienced some short-term irritation symptoms, expressed as dry throat, nose, eyes, and phlegm. In conclusion, short-term use of an e-cigarette in confined spaces increased indoor PM_2.5 level and caused some irritation symptoms in bystanders.     

Determination of diffusion coefficients in film systems on the basis of Fe/Cr and Cu/Cr

This paper presents the results of investigation of condensation stimulated (CSD) and thermal stimulated (TSD) diffusion in nanoscale film systems on the basis of Fe/Cr and Cu/Cr by Auger-electron spectroscopy method. The film systems were built in ultrahigh vacuum. Auger spectrum was traced during condensation after each increase in thickness of 0.5-1 nm or during film systems annealing from 300 to 683 K over 5 h. According to experimental data the concentration profiles were built and the effective coefficients of CSD and TSD were computed by several mathematical methods. The efficiency of these techniques in different cases was analyzed. The most accurate results were obtained with Weeple and Gauss error methods that take into account the thickness of the diffusant source.     

Cold Model Investigations of Melting of Ice in a Gas-Stirred Vessel

The melting of steel scrap in high temperature liquid iron melt is investigated by conducting cold model experiments of the melting of ice sample of different geometries and sizes in an argon-stirred vessel containing water. The melting process of ice samples is observed using a high-speed camera. Design of experiments is based on similarity criteria. The relationships between non-dimensional groups related to heat transfer (Nu, Re, Pr, and Gr) are derived for different experimental conditions. The results are compared with those reported in the literature. The heat transfer coefficient is estimated as a function of mixing power and is found to be in good agreement with the calculated values obtained by using reported relationships in literature.     

Experimental investigation of compact silicon carbide heat exchangers for high temperatures

The results of experimental investigations of novel ceramic high-temperature heat exchangers (HTHE) and its main characteristics such as effectiveness and power load as a function of mass flow and the geometry of the channels are presented. Firstly, some information on the background and the manufacturing of the HTHE, which is based on honey comb structures made out of extruded silicon carbide, is given. The experimental tests have been carried out with air as a heat transfer medium at temperatures of up to 1000 °C. The experimental set-up is described in detail. The acquired characteristic temperature and effectiveness data for different inlet temperatures and mass flows are discussed. They have been compared with data from theoretical calculations as well as with characteristic data of typical counter flow heat exchangers. Additionally, thermal shock tests have been carried out for a qualitative testing of the mechanical strength. Finally, a conclusion and an outlook on further activities are given.