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Transmission Electron Microscopy as indispensable tool for imaging and chemical characterization of heterogeneous catalysts

Transmission Electron Microscopy as indispensable tool for imaging and chemical characterization of heterogeneous catalysts

Transmission Electron Microscopy (TEM) and its mutation Scanning Transmission Electron Microscopy (STEM) is one of the most important methods providing unique information on structure and chemistry of solid catalysts at length scale down to level. The principal reason is its high spatial resolution (below 0.1 nm) but also universality, i.e., ability of observation of both images and diffraction patterns of individual nanometer size objects. Recent advances in TEM in particular application of image and beam correctors, possibility of studying specimens at non vacuum conditions (environmental TEM) and possibility of dynamic (time resolved) studies even further broadened the applicability of the method in catalysis.

Open access
Ovidius University Annals of Chemistry
Analele Universitatii "Ovidius" Constanta - Seria Chimie
Open access
DNA-based biosensors with polyvinyl alcohol external membrane as a tool for the evaluation of antioxidant activity of white wines

Abstract

Electrochemical DNA-based biosensors with external protective membranes were prepared for the evaluation of antioxidant properties of white wines against pro-oxidant hydroxyl radicals. A glassy carbon working electrode (GCE) was modified using a layer-by-layer deposition technique with low molecular weight double stranded DNA and an outer sphere polymer film membrane of Nafion, chitosan or polyvinylalcohol. The composition of a working procedure with membrane-covered DNA biosensors were optimized with respect to their voltammetric response in solution of the DNA redox indicator [Fe(CN)6]3-/4- after the incubation in white wines. Polyvinylalcohol (PVA) film was proved to be the suitable membrane. The PVA/DNA/GCE biosensor was used for the detection of a deep degradation of the surface-attached DNA at the incubation in the cleavage agent and for the evaluation of antioxidant properties of white wines at the incubation in mixtures of cleavage agent and wine. The investigation of the biosensors with protective membranes represents a significant contribution to utilization of the electrochemical DNA based biosensors for practical purposes.

Open access
Analysis of C3 fraction splitting system performance by mathematical modeling in MATLAB environment

. Chudinova AA, Buchatskaya NI, Podgornyi VV, Gavrikov AA, Ivashkina EN, Dolganova IO (2016) Increase of efficiency isopropylbenzene manufacturing with use of integrated mathematical models. Petroleum and Coal, 58(2): 155—160. Chuzlov VA, Molotov KV (2016) Development of computer modeling system as a tool for light naphtha isomeration improvement. Petroleum and Coal, 58(1): 47—55. Kazemi A, Hosseimi M, Mehrabani-Zeinabad A, Faizi V (2016) Evaluation of different vapor recompression distillation configurations based on energy requirements and associated costs

Open access
Biosensors - classification, characterization and new trends

Biosensors - classification, characterization and new trends

Biosensors represent promising analytical tools applicable in areas such as clinical diagnosis, food industry, environment monitoring and in other fields, where rapid and reliable analyses are needed. Some biosensors were successfully implemented in the commercial sphere, but majority needs to be improved in order to overcome some imperfections. This review covers the basic types, principles, constructions and use of biosensors as well as new trends used for their fabrication.

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Non-parametric kinetic analysis of thermogravimetric data for the thermal degradation of poly(tetrafluorethylene)

Abstract

Thermal degradation of Teflon was investigated by thermoanalytical methods (TG and DTA). In the kinetic analysis of the experimental data, the NPK method proves to be a valuable tool, allowing for some new kinetic aspects of the degradation process to be obtained. Analysis of the computed isothermal and isoconversional vectors provided some insight into the reaction kinetics. Two different initiation pathways were suggested to control the global degradation kinetics, their relative contribution being temperature-dependant

Open access
Effect of thermal treatment on antioxidant activity and colour of carrot purées

Abstract

Total antioxidant activity, levels of bio-active compound groups and instrumental colour of carrot purée subjected to thermal treatment (70°C/2 min) were measured. The method applied to the dosage of ascorbic acid was with 2,6-diclorophenolindophenol. Total phenols (TP) in purée were determined using the Folin- Ciocalteau method and antioxidant activity by the use of DPPH free radical method. The colour of the samples was measured using a Hunter-Lab colour meter. Heat treatment caused a rapid decrease in ascorbic acid. Phenolic contents were in general unaffected by thermal treatment. Colour parameters were significantly affected by thermal treatment. This provides a helpful tool for understanding the effect of processing on colour variation of carrot purée in a broader spectrum. Industrial relevance: This research paper provides scientific evidence of the influence of thermal treatments in retaining important bioactive compounds.

Open access
CRISPR/Cas in genome defense and gene editing

Abstract

Targeted genome editing using engineered nucleases such as ZFNs and TALENs has been rapidly replaced by the CRISPR/Cas9 (clustered, regulatory interspaced, short palindromic/ CRISPR-associated nuclease) system. CRISPR/Cas9 technology represents a significant improvement enabling a new level of targeting, efficiency and simplicity. Gene editing mediated by CRISPR/Cas9 has been recently used not only in bacteria but in many eukaryotic cells and organisms, from yeasts to mammals. Other modifications of the CRISPR-Cas9 system have been used to introduce heterologous domains to regulate gene expressions or label specific loci in various cell types. The review focuses not only on native CRISPR/Cas systems which evolved in prokaryotes as an endogenous adaptive defense mechanism against foreign DNA attacks, but also on the CRISPR/Cas9 adoption as a powerful tool for site-specific gene modifications in fungi, plants and mammals.

Open access
Design of operational temperature for immobilized glucose isomerise using an accelerated inactivation method

Abstract

Thermal inactivation of immobilized glucose isomerase in a concentrated glucose solution was investigated in the batch mode and temperature range of 83–95 °C, which is substantially higher than the temperature used in the industrial production of high-fructose corn syrup. Simultaneous evaluation of all inactivation data showed that first-order kinetics with the Arrhenius temperature dependence of the rate constant provided a good approximation of the biocatalyst stability under the investigated conditions. The model parameters were then used to predict the operational temperature for this biocatalyst in the production of high-fructose corn syrup based on the set operational life-time of the biocatalyst. The simulation predicted a window of operational temperature of 60–65 °C, which corresponds very well with the industrial applications of this biocatalyst. This observation demonstrates that the multi-temperature method of enzyme inactivation can provide a good estimate of biocatalyst process stability and is thus a useful tool in the development of biocatalytic processes.

Open access
Determination of Toxicological Parameters of Selected Bioactive Organic Chemicals Using the Ostracodtoxkit FTM

Abstract

Assessment of the impact of pharmaceutical residues on living organisms is very complex subject. Apart from taking into account the toxicity of individual compounds also their presence in mixtures should be taken into account. In this work, attempts were made to assess the ecotoxicity of biologically active substances (with 50 % effective concentration (EC 50) values growing from fluoxetine (EC 50 = 4.431 nM) >> gemfibrozil ≈ 17α-ethinylestradiol ≈ ketorolac > indomethacin > theophylline ≈ progesterone > naproxen ≈ trypsin > 2-(2,4,5-trichlorophenoxy)propionic acid > chloramphenicol > acetylsalicylic acid > ibuprofen > ketoprofen > 19-norethindrone to bezafibrate as the least toxic drug among studied ones) to the ISO standardized Ostracodtoxkit FTM bioassay. The Ostracodtoxkit FTM was proven to be very sensitive tool with respect to responding to presence of pharmaceuticals. Results of studies justify the statement that more research is needed in field of assessment of chronic exposure to pharmaceuticals and other newly emerging pollutants especially when they are present in complex mixture.

Open access