Nanocomposites of SnO2 and g-C3N4: Preparation,characterization and photocatalysis under visible LED irradiation

Tin dioxide nanoparticles were prepared in the presence of graphitized carbon nitride (g-C₃N₄) forming nanocomposites with different contents of SnO₂ up to 40 %. G-C₃N₄ was synthetized by heating of melamine at 550 °C in the open air and Sn²⁺ ions were precipitated by sodium hydroxide in g-C₃N₄ aqueous dispersions. Resulting mixtures were dried by freezing at ?20 °C and calcined at 450 °C to obtain SnO₂/g-C₃N₄ nanocomposites.The nanocomposites were characterized by common characterization methods in solid state and in their aqueous dispersions using dynamic light scattering (DLS) analysis and photocatalysis. SnO₂ nanoparticles in the nanocomposites were found to have an average size of 4 nm, however, those precipitated without g-C₃N₄ had an average size of 14 nm. Separation of photoinduced electron and holes via heterojunction between SnO₂ and g-C₃N₄ was demonstrated by photocatalytic decomposition of Rhodamine B (RhB) under LED visible irradiation (416 nm) and photocurrent measurements. The most photocatalytically active nanocomposite contained 10 % of SnO₂. Graphitized carbon nitride was assumed to serve as a template structure for the preparation of SnO₂ nanoparticles with a narrow size distribution without using any stabilizing additives.     

Synthesis and magnetorheological characteristics of ribbon‐like,polypyrrole‐coated carbonyl iron suspensions under oscillatory shear

One of the crucial problems of classical magnetorheological (MR) fluids is their high rate of sedimentation. This disadvantage may be substantially eliminated using core‐shell particles. The aim of this study is to prepare spherical carbonyl iron (CI) particles coated with conducing polymer polypyrrole (PPy) with ribbon‐like morphology. Scanning electron microscopy proved the formation of the ribbon‐like layer onto CI particles while Fourier transform infrared spectroscopy confirmed the chemical structure of PPy. The magnetic properties observed via vibrating sample magnetometer showed decreased magnetization saturation of core‐shell‐structured particles due to the existence of non‐magnetic surface layer. MR measurements performed under oscillatory shear flow as a function of the applied magnetic flux density, temperature, and particle concentration showed that core‐shell particle‐based MR suspension exhibits sufficient MR performance for practical applications. Moreover, the suspension stability is promoted significantly when core‐shell particles are used as a dispersed phase. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Development and benchmarking of a mechanical model for GFR plate-type fuel

The reference fuel design currently being considered within the Generation-IV Gas-cooled Fast Reactor (GFR) project is a ceramic plate matrix with a honeycomb inner structure containing small fuel cylinders. The fuel is mixed plutonium–uranium carbide, while the matrix material is silicon carbide. The present paper describes the mechanical part of a thermal–mechanical model being developed for studying the transient behavior of this highly heterogeneous fuel type. Benchmarking has been carried out against detailed finite-elements modeling (FEM).The resultant thermal–mechanical model can provide reliable fuel and cladding (matrix) stress/strain conditions to evaluate temperatures and neutronic feedbacks. As such, it has been integrated into PSI’s coupled code system “FAST”, which aims at the comprehensive safety analysis of advanced fast reactor systems.The detailed FEM analysis of the GFR fuel has been useful not only for benchmarking the new model, but also for obtaining an in-depth understanding of fuel stress/strain characteristics, which cannot be reproduced with simplified models. Thereby, the range of applicability of the new model has clearly been defined. In particular, the 3D FEM analysis has revealed a concentration of stresses at the pellet corners during pellet/matrix contact, which could lead to fuel element failure. This effect is found to be mitigated considerably, if the fuel pellets are shaped in a manner which enhances the contact area.     

Ranking the efficacies of selected red wine phenolic anti-oxidants using reversed-phase HPLC

Several studies have assessed total anti-oxidant activity of wine or individual components in isolation using chemical-based assays. In this study, a quantitative approach was developed to assess the relative anti-oxidant efficacies of selected red wine phenolics via peak reduction, using reversed-phase HPLC. Both intact red wine and phenolic standard solutions were challenged with five oxidant model systems as follows: (1) hydrogen peroxide (H₂O₂); redox-active metal ions (2) Fe³⁺ and (3) Cu²⁺; and the Fenton reagents (4) H₂O₂ + Fe²⁺; and (5) H₂O₂ + Cu⁺. Treatment with oxidants (1–3) resulted in loss of 47–60% of phenolic standards, which increased to 66–89% for treatment with the Fenton systems, with quercetin exhibiting the optimal anti-oxidant activity. For intact red wine, treatment with oxidants (1–3) led to all phenolic compounds being oxidised (27–77% loss), with caffeic acid and quercetin as the most effective anti-oxidants. For both Fenton systems (4–5), activities in red wine were considerably enhanced for caffeic acid and quercetin, which exhibited the highest anti-oxidant efficacies with 100% peak reduction, while p-coumaric acid and gallic acid were less effective anti-oxidants with peak reductions of 60–68%. The ranking, facilitated by this new quantitative approach, allows comparison of the individual efficacies of the anti-oxidants in a complex matrix.     

Controlled band dispersion for quantitative binding determination and analysis with electrospray ionization‐mass spectrometry

This review discusses recent emerging techniques that have been used to couple flow‐injection analysis (FIA) and electrospray ionization‐mass spectrometry (ESI‐MS) for the quantitation of noncovalent binding interactions. Focus is placed predominantly on two such methods. Diffusion‐based measurements, developed by Konermann and co‐workers, uses controlled‐band dispersion prior to ESI‐MS to determine diffusion constants and binding constants based on the temporal variation of ligand signal measured in the mass spectrum (an indirect technique). Dynamic titration, developed by Schug and co‐workers, is a direct method, where a temporal compositional gradient of a guest molecule is induced in the presence of host in solution to monitor the concentration dependence of complex formation as a function of observed complex ion abundance after ESI‐MS. Further discussion places these techniques in the context of a variety of other direct and indirect ESI‐MS‐based binding determination methods, and highlights advantages, disadvantages, and practical considerations for their proper use to investigate a broad range of macromolecular and small‐molecule interaction systems. © 2009 Wiley Periodicals, Inc., Mass Spec Rev 29:806–829, 2010     

A New and Fast HPLC Method for Determination of Rutin, Troxerutin, Diosmin and Hesperidin in Food Supplements Using Fused-Core Column Technology

A new and fast high-performance liquid chromatography (HPLC) method using fused-core column for separation of rutin, troxerutin, diosmin, and hesperidin has been developed and used for determination of these flavonoids in food supplements. Efficient separation of flavonoids and internal standard methylparaben was achieved on the fused-core column Ascentis Express RP-Amide (100?×?3.0 mm), particle size 2.7 μm, with mobile phase acetonitrile/water solution of acetic acid pH?3 (30:70, v/v) at a flow rate of 1.0 mL?min^?1 and at temperature 50 °C. The detection wavelengths were set at 283 nm for hesperidin and at 255 nm for rutin, troxerutin, diosmin, and internal standard methylparaben. Under the optimal chromatographic conditions, good linearity with correlation coefficients in the range (r?=?0.9991–0.9998; n?=?7) for all flavonoids was achieved. Commercial samples of food supplements were extracted with 100 % dimethyl sulfoxide using ultrasound bath for 10 min and then diluted to methanol. A 5-μL sample volume of the filtered solution was directly injected into the HPLC system. Accuracy of the method defined as a mean recovery of flavonoids from food supplement matrix was in the range 96.2–104.4 % for all flavonoids. The intraday method precision was satisfactory, and relative standard deviations of sample analysis including preparation and determination of different food supplements were in the range 0.5–3.5 % for all flavonoids. The developed method has shown high sample throughput during sample preparation process, modern separation approach, and short time (5 min) of analysis.     

Physicochemical Investigation of the Reaction of Components of the Si — Al — O — N — Ti System in the Si3N4 — Al2O3 — AlN — SiO2 — TiN — TiO2 Region. Part 2. Subsystems Si3N4 — AlN,TiN — AlN,Al2O3 — AlN

The reaction of components of the Si — Al — O — N — Ti system in its elements Si ₃N₄ — AlN, TiN — AlN, and Al ₂O ₃ — AlN was investigated by differential thermal and x-ray diffraction analysis. It was established that upon hot pressing mixtures of Si₃N ₄ and AlN (up to 1950°C) free silicon is formed by the decomposition of Si ₃N₄, which reacts with oxygen present as an impurity to form SiO. When TiN reacts with AlN a phase with the spinel structure (Al₂₃O ₂₇N ₅), which can form only in the presence of excess oxygen, appears in addition to the initial components. Spinel is also produced by the reaction of Al ₂O₃ with AlN. In this case a eutectic between Al ₂₃O₂₇N₅ and Al₂O₃ is observed.     

Volatile compounds on the surface and within Iberian dry-cured loin

The profile of volatile compounds from external and internal areas of Iberian dry-cured loin was studied by headspace solid-phase microextraction. Higher levels of 16 volatile compounds (hexane, decane, 3-methylbutanal, several sulphur compounds and some aromatic hydrocarbons) were detected in the outer part of the loins. These differences could be owing to several factors, such as greater exposure to oxygen and dehydration conditions in the surface of the product, which favour oxidation reactions and Strecker degradation of amino acids. Moreover, the addition of spices on the surface and the proximity of a mould layer growing on the surface of the product could also contribute to the higher levels of these compounds on the external layer. However, other sulphur compounds coming from spices showed similar levels on the surface and within the loins. This different behaviour could be a consequence of different diffusion rates depending on the features of the compound and the matrix.     

Fast branch & bound algorithms for optimal feature selection

A novel search principle for optimal feature subset selection using the Branch & Bound method is introduced. Thanks to a simple mechanism for predicting criterion values, a considerable amount of time can be saved by avoiding many slow criterion evaluations. We propose two implementations of the proposed prediction mechanism that are suitable for use with nonrecursive and recursive criterion forms, respectively. Both algorithms find the optimum usually several times faster than any other known Branch & Bound algorithm. As the algorithm computational efficiency is crucial, due to the exponential nature of the search problem, we also investigate other factors that affect the search performance of all Branch & Bound algorithms. Using a set of synthetic criteria, we show that the speed of the Branch & Bound algorithms strongly depends on the diversity among features, feature stability with respect to different subsets, and criterion function dependence on feature set size. We identify the scenarios where the search is accelerated the most dramatically (finish in linear time), as well as the worst conditions. We verify our conclusions experimentally on three real data sets using traditional probabilistic distance criteria.     

Simple On-Line Algorithms for the Maximum Disjoint Paths Problem

In this paper we study the classical problem of finding disjoint paths in graphs. This problem has been studied by a number of authors both for specific graphs and general classes of graphs. Whereas for specific graphs many (almost) matching upper and lower bounds are known for the competitiveness of on-line algorithms, not much is known about how well on-line algorithms can perform in the general setting. The best results obtained so far use the expansion of a network to measure the algorithms performance. We use a different parameter called the routing number that, as we will show, allows more precise results than the expansion. It enables us to prove tight upper and lower bounds for deterministic on-line algorithms. The upper bound is obtained by surprisingly simple greedy-like algorithms. Interestingly, our upper bound on the competitive ratio is even better than the best previous approximation ratio for off-line algorithms. Furthermore, we introduce a refined variant of the routing number and show that this variant allows us, for some classes of graphs, to construct on-line algorithms with a competitive ratio significantly below the best possible upper bound that could be obtained using the routing number or the expansion of a network only. We also show that our on-line algorithms can be transformed into efficient algorithms for the more general unsplittable flow problem.