5101. Determination of biogenic amines by thermal lens microscopic detection of enzymatically released ammoniumMojca Žorž, Mladen Franko, 2016, published scientific conference contribution abstract Abstract: Biogenic amines (BAs) are organic amines present in meat, fish, dairy produce and wine due to the breakdown of amino acids, catalysed by microbial decarboxylases. BAs determination in food is important not only because of possible toxicological effects such as nausea, sweating and headache but also due to their possible role as indicators of food spoilage. Chromatographic methods are traditionally applied for determination of BAs in food [1], which usually require preliminary operations for sample pre-treatment that are laborious and difficult to automate. On the other hand, screening analytical systems provide simple, low cost and rapid analysis with the possibility of subjecting high number of samples to the screening system in a short time [2]. In this work we present a novel method for screening determination of BAs using a microfluidic system with the detection by highly sensitive thermal lens microscope (μFIA-TLM).
Four biogenic amines (putrescine, cadaverine, histamine and tyramine) were subjected to enzymatic catalysis by transglutaminase, where ammonia was released as a product of acyl transfer reaction between the peptide bound glutamine (Gln) and the amino group of BAs. Ammonia was further transformed into indophenol blue by the Berthelot reaction. The coloured product was detected in batch (static) mode in a 100 μm sample cell or in μFIA (flowing) mode in a microchip with the same optical path length. The detection was performed on a TLM system applying a solid-state diode as an excitation source (660 nm). Organic solvents were tested for signal enhancement.
For evaluation of the sensitivity and determination of LOD values (S/N = 3 basis), the NH4Cl standard solution was applied in Berthelot reaction with further detection on TLM system. The LODs for NH4+ in batch mode and in μFIA were 24 μg/L and 109 μg/L, respectively. Both LOD values are lower than the LOD achieved with conventional spectrophotometry (180 μg/L). When mixtures of the indophenol standard solutions and EtOH in the ratio of 1:1 were prepared the LOD in batch mode was improved to 3 μg/L, achieving 60-times improvement compared to spectrophotometry.
Keywords: Biogenic amines, Thermal lens microscopy, microfluidics, translgutaminase
Published in RUNG: 05.07.2016; Views: 5174; Downloads: 0
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5104. Highly Sensitive Determination of Pyoverdine in Cloud Water by HPLC-Thermal Lens SpectrometryLeja Goljat, Mitja Martelanc, Virginie Vinatier, Anne-Marie Delort, Mladen Franko, 2016, published scientific conference contribution abstract Abstract: New method for pyoverdine and Fe(III)-pyoverdine detection was developed. Two isomers of pyoverdine and two isomers of Fe(III)-pyoverdine were separated isocraticaly on reversed-phase (RP)-C18 chromatograhic column and detected by DAD, FLD and TLS. HPLC-TLS method enables separation and determination of pyoverdine and Fe(III)-pyoverdine in a single run and excels in superior sensitivities when compared to conventional HPLC-DAD system.
Keywords: Pyoverdine, Fe(III)-pyoverdine, cloud water, high-performance liquid chromatography, thermal lens spectrometry
Published in RUNG: 04.07.2016; Views: 5611; Downloads: 0 |
5105. Slovenska literatura na stičišču kulturAna Toroš, published scientific conference contribution (invited lecture) Abstract: Prispevek obravnava sodobno slovensko literaturo iz Goriške, Tržaške in Videmske pokrajine (Rezija, Beneška Slovenija), torej literaturo, ki nastaja v Furlaniji – Julijski krajini, v Italiji, ob meji s Slovenijo. Na primerih del posameznih avtorjev (Viljem Černo, Silvana Paletti idr.) so prikazane nekatere značilnosti te literature, med katerimi gre izpostaviti osredotočenost avtorjev na vprašanje obstoja slovenske skupnosti v Italiji in s tem povezano refleksijo o jeziku, identiteti, meji ter »Drugem« v tem prostoru.
Keywords: slovenska poezija, manjšinska literatura, Trst, Gorica, Rezija, Beneška Slovenija
Published in RUNG: 01.07.2016; Views: 4479; Downloads: 0
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5106. Non-Singular Method of Fundamental Solutions for Two-dimensional Thermoelasticityliu qingguo, Božidar Šarle, published scientific conference contribution abstract Abstract: A framework for simulation of thermomechanical processing of microstructures by the method of fundamental solutions, free of artificial boundary, is shown. The formulation of the method for two-dimensional thermal and mechanical models is presented. In particular, the formulation for thermo-elastic problems is discussed. In the thermal and mechanical models, the concentrated point sources are replaced by the distributed sources over the sphere around the singularity to regularize the singularities and the balance of forces is used to calculate some of the otherwise singular diagonal coefficients. This procedure enables also for solving problems with internal voids and inclusions. The novel boundary meshless method has been assessed by comparison with MFS and analytical solution. The method is easy to code, accurate, and efficient.
Keywords: thermomechanics, elasticity, plasticity, non-singular method of fundamental solutions, three-dimensions, microstructures
Published in RUNG: 28.06.2016; Views: 5245; Downloads: 0
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5107. Method of Regularized Sources for Stokes Flow Problems with Improved Calculation of Velocity Derivatives at the BoundaryBožidar Šarler, wen shiting, li ming, published scientific conference contribution abstract Abstract: The solution of Stokes flow problems with Dirichlet and Neumann boundary conditions is performed by a non-singular Method of Fundamental Solutions which does not require artificial boundary, i.e. source points of fundamental solution coincide with the collocation points on the boundary. Instead of Dirac delta force, an exponential function, called blob, with a free parameter epsilon is employed, which limits to Dirac delta function when epsilon limits to zero. The solution of the problem is sought as a linear combination of the fields due to the regularized sources that coincide with the boundary and with their intensities chosen in such a way that the solution complies with the boundary conditions. A two-dimensional flow between parallel plates is chosen to assess the properties of the method. The results of the method are accurate except for the derivatives at the boundary. A correction of the method is proposed which can be used to properly assess also the derivatives at the boundary
Keywords: stokes flow, method of regularized sources, meshless method
Published in RUNG: 28.06.2016; Views: 4279; Downloads: 0
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5108. Study of Li-S batteries by S K-edge RIXS spectroscopyMatjaž Kavčič, Matjaž Žitnik, Klemen Bučar, Marko Petrič, Iztok Arčon, Robert Dominko, Alen Vižintin, 2016, published scientific conference contribution abstract Abstract: Li-S batteries are considered as one of the most promising candidates for future batteries in applications where high energy density is required [1]. Despite that the general principle of operation is known for a long time [2], the lack of detailed understanding of relevant operation mechanisms has so far prevented their extensive use. A Li-S battery is composed of a lithium metal anode and a sulfur based cathode, separated by a porous separator wetted with electrolyte. During the battery cycle the reduction and oxidation of S to Li2S and back proceeds through a complicated equilibrium mixture of compounds that are typically dissolved in the electrolyte in the form of long and short chain polysulfides. In order to improve our understanding of polysulfide formation and its interactions within electrode, which are essential to achieve the long term cycling stability, development and application of new analytical tools is required.
In this work sulfur K-edge resonant X-ray emission (RXES) measurements were performed on the Li-S battery in operando mode. The experiment was performed at the ID26 beamline at ESRF using the Johansson type tender x-ray emission spectrometer [3]. Full K-L RIXS maps were recorded on a set of chemically prepared Li2Sx sample standards characterized by different Li:S stoichiometric ratio, followed by the operando measurements on Li-S battery. Using the spectra recorded on Li2Sx standards two excitation energies were chosen and RXES spectra from the back of the battery cathode were sequentially acquired during one discharge cycle (C20). The relative amounts of each sulfur compound in the cathode during the discharge cycle were determined from the linear combination fit using measured reference standard spectra. Because of resonant excitation conditions the sensitivity for the polysulfide detection was significantly enhanced. Our work sets up S K-edge RIXS spectroscopy as an important analytical tool to study the mechanism of Li-polysulfide formation in the cathode and their interaction with the host matrix and electrolyte.
Keywords: RIXS, RXES, Li-S battery, operando, Sulphur K-edge XANES, Lithium polysulphides, Li2S
Published in RUNG: 28.06.2016; Views: 5695; Downloads: 0
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5109. XAS and micro-XRF analysis of mono and bi-metallic exopolysaccharide (FePd-EPS) bio-generated by K. oxytocaIztok Arčon, Stefano Paganelli, Oreste Piccolo, Michele Gallo, Katarina Vogel-Mikuš, Franco Baldi, 2016, published scientific conference contribution abstract Abstract: Bacteria Klebsiella oxytoca (DSM 29614) secret a specific exopolysaccharide (EPS) in the presence of Fe(III)-citrate, as sole carbon and energy source, and produces after 7 days an iron gel precipitate (Fe-EPS) [1]. In the presence of palladium or other metal species, the culture of K. oxytoca can produce other mono or bimetal species (Pd-EPS, FePd-EPS) [2]. These bio-materials may be used as green biogenerated catalysts or for other biotechnological purposes. In this work we present the analysis of the morphology and the chemical state of the metals in mono and bi-metallic (Fe-EPS, Pd-EPS, FePd-EPS) complexes, by a combination of micro X-ray fluorescence, X-ray absorption spectroscopy methods (XANES and EXAFS), and transmission electron microscopy. The results show that iron in monometallic Fe-EPS and bimetalic FePd-EPS is in the mineralized form of iron oxides/hydroxides, predominantly in the form of Fe3+, with a small amount of Fe2+ in the structure, as a mixture of different nano-crystalline iron oxides and hydroxides. Palladium on the other hand is found as Pd(0) in the form of metallic nanoparticles with fcc structure in both, bi-metallic (FePd-EPS) and mono-metallic (Pd-EPS) species. In bi-metallic species Pd and Fe nanoparticles agglomerate in larger clusters, but they remain spatially separated. Access to the SR facilities at ESRF (beamline ID21, project LS-2225), DESY (beamline C) Hamburg (project I-20110511 EC) and ELETTRA (beamline XAFS, project 20115112) is acknowledged.
Keywords: Klebsiella oxytoca, Fe, Pd, XANES, EXAFS, exopolysaccharide, FePd-EPS
Published in RUNG: 28.06.2016; Views: 5583; Downloads: 0
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5110. Fuzzy Subhypergroups DegreeIrina Elena Cristea, 2016, original scientific article Abstract: In this paper we define the degree to which a fuzzy subset on a hypergroup is a fuzzy subhypergroup by means of the residuate sets, constructed using the minimum t-norm. We give also some properties of this new index connected with the intersection of a family of fuzzy subhypergroups, and respectively with the homomorphic image/preimage of a fuzzy subset. We conclude with addressing new problems related with intuitionistic fuzzy subhypergroups and fuzzy subpolygroups in the framework of our discussion.
Keywords: Fuzzy set, fuzzy subhypergroup, residuate set, t-norm
Published in RUNG: 24.06.2016; Views: 4300; Downloads: 0
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