Thermal Behaviors of Bisazocalix[4]arene Derivatives

In this article, calix[4]arene (4) was prepared by debutylation and hydrolyses reacting from 25,27-dibenzoyl-26,28-dihydroxy-5,11,17,23-tetra(tert-butyl)calix[4]arene (2). Azocalix[4]arenes (6a-c) were coupled by linking 4-methoxy, 4-ethyl, and 4-nitroaniline to calix[4]arene (4) through a diazo-coupling reaction. Thermal behavior characteristics and decomposition routes of 25,26,27,28-tetrahydroxy-11,23-di(tert-butyl)-5,17-(p-substitue phenyl)azocalix[4]arene (6a-c) were investigated in air atmosphere by means of thermogravimetry (TG), differential thermogravimetry (DTG), and differential thermal analysis (DTA) analyses. It was found that the decomposition of all compounds complete with two exothermic stages which corresponded to removal of substitute groups (methoxy-, ethyl-, nitro-) and second stage rest of structure decomposition.     

Synthesis of MnFe2O4 nanocrystals by wet-milling under atmospheric conditions

This work reports an original method for synthesis of well-crystallized manganese ferrite (MnFe₂O₄) nanoparticles via a high energy wet milling technique under atmospheric conditions, starting from metallic Mn and Fe powders in the presence of distilled water. The effects of milling conditions on the formation and magnetic properties of MnFe₂O₄ nanoparticles were investigated in detail. Fully stoichiometric MnFe₂O₄ nanocrystals with an average crystallite size of 14.5 nm were produced after 24 h of milling. As-synthesized MnFe₂O₄ nanocrystals were found to show soft magnetic behavior at room temperature with saturation magnetization of 53 emu/g. Due to reduced thermal effects, the saturation magnetization increased to 68 emu/g at 5 K. Results show that this method is simple and efficient for the mass production of MnFe₂O₄ nanoparticles.     

The effect of polypropylene fibers on asphalt performance

Polypropylene fibers are extensively used in civil engineering applications for many years. These fibers are used in concrete as a three-dimensional secondary reinforcement. Due to adhesion between polypropylene fibers and bitumen, the strengthening mechanism in asphalt concrete is somehow different.     

High power generation with simultaneous COD removal using a circulating column microbial fuel cell

BACKGROUND: A circulating column microbial fuel cell (MFC) with Cu anode and Au? Cu air cathode was used for power generation and chemical oxygen demand (COD) removal from synthetic wastewater. The column was operated in repeated‐fed batch mode using acclimated anaerobic sludge. The contents of the column MFC were circulated while the feed wastewater was fed to the reactor in fed‐batch mode. Effects of feed COD concentration and COD loading rate on voltage difference, power density and percentage COD removal were investigated. RESULTS: The highest voltage difference (650 mV), power density (40 W m^?2) were obtained with a feed COD of 6400 mg L^?1, yielding 45% COD removal with a COD loading rate of nearly 90 mg h^?1. Low COD loadings (<90 mg h^?1) caused substrate limitations, and high loadings (>90 mg h^?1) resulted in inhibition of COD removal and power generation. The highest percentage COD removal (50%) was obtained with feed COD content of 10.35 g L^?1 or a COD loading rate of 145 mg h^?1. CONCLUSION: The power densities obtained with the circulating column MFC were considerably higher than those reported in the literature due to elimination of mass transfer limitations by the high circulation rates, proximity of electrodes and small anode surface area used in this study. Further improvements may be possible with optimization of the operating parameters. Copyright © 2009 Society of Chemical Industry     

Nano/Micro Dielectric Surface Flashover in Partial Vacuum

In this paper, we present experimental results of surface flashover characteristics of epoxy resin and epoxy resin cast with powdered Al₂O₃ (nano/micro-composite dielectric) samples in partial pressure of nitrogen. The flashover studies are conducted separately using DC and 20 kHz AC signals. The voltage, current, and light emission waveforms are obtained. The optical data is collected by a video camera and a photomultiplier tube (PMT). The nano/micro composite dielectric samples used in the experiments are produced in-house by mixing 1:10 weight ratio of AI₂O₃ powder with epoxy resin of known properties. Throughout this study, copper electrodes are used and are placed over the dielectric samples to initiate surface flashover events. The results of surface flashover voltages as a function of pressure are presented. Additionally, optical emission characteristics along with the voltage and current waveform data are also presented.     

Novel Coulometric Approach to Evaluation of Total Free Polyphenols in Tea and Coffee Beverages in Presence of Milk Proteins

Electrogenerated hexacyanoferrate(III) ions have been used as coulometric titrant for the determination of total free polyphenols in beverages. Stoichiometric coefficients of natural flavonoids (rutin, quercetin, and taxifolin) in their reaction with [Fe(CN)₆]³⁻ ions were established. The number of electrons involved in the oxidation corresponds to number of phenolic OH groups in the molecule of polyphenols. Proteins (casein and bovine serum albumin) bind polyphenols in the complexes that leads to significant decrease of free polyphenols portion (in the range of 5–76%). Ferric reducing power (FRP) of eight tea and 17 coffee samples was determined. The absolute FRP values ranged from 224 to 405 and from 241 to 488 C cup⁻¹ for tea and coffee, respectively. Effect of milk proteins on total free polyphenols of tea and coffee and appropriate alteration of beverages FRP were evaluated. Milk addition decreases FRP of drinks in the range of 10–70% reflecting high content of inactive polyphenols.     

Advanced ePrometheus™ GNF fuel cycle optimization tool

This paper presents the advanced version of ePrometheus™ GNF Fuel Cycle Optimization Tool. ePrometheus is Global Nuclear Fuel-Americas LLC (“GNF”) patented computer system used to optimize Boiling Water Reactor (BWR) fuel management and operations. The advanced version of ePrometheus utilizes a new database structure (Oracle 11 g) and a new C#, WPF based graphical user interface (GUI), and employs a capability of performing refueling calculation. It also displays additional 2-D and 3-D core simulation data that are necessary to improve the fuel cycle design process, and utilizes many more advanced features based on user experience feedback. The objective of this paper is to present new advanced infrastructure of the system, and to provide overall information on the advanced features of the newly released version 3.0.     

Commercial test kits and the determination of histamine in traditional (ethnic) fish products-evaluation against an EU accepted HPLC method

Although commercial test kits are generally used and/or evaluated for determining histamine in fresh and canned fish, and fish meal, there is little information on their performance and the application for traditional fish products (TFPs), which generally differ in product properties. In this study, three quantitative (Food EIA, Veratox, Histaquant) and four qualitative (Histasure, Histameter, Transia qualitative and semi-quantitative) commercial histamine test kits were evaluated against HPLC method for detecting histamine in several traditional fish products. Among the quantitative kits, Histamine Food EIA showed the best correlation with HPLC method for TFPs (R² = 0.9132) as well as good recoveries ranging between 89 (±4.11)% and 117 (±1.50)%. Although good recoveries were also observed with Veratox kit, poor correlation was found with HPLC. Poor correlation and low recoveries were also observed with Histaquant. Histasure and Transia tube histamine kits showed good agreement with HPLC results. However, the detection limit for Transia qualitative kit is 100 ppm, and for Histasure and Transia semi-quantitative kits can be set to 50 ppm. Therefore, Histasure and Transia semi-quantitative kits are found more suitable for either HACCP monitoring histamine in seafood processing plants or regulatory purposes according to Food Drug and Administration (FDA) legislation for TFPs. However, Transia semi-quantitative kit should be used in caution for histamine cut off values <50 ppm. This study shows that each test kit can represent different performance for determining histamine in TFPs according to product type, and therefore new commercial test kits should be evaluated against an approved analytical method before applications in future for these types of products.     

Determination of formability characteristics of Crofer 22 APU sheets as interconnector for solid oxide fuel cells

In this study, the general formability characteristics of Crofer^® 22 APU sheets of different thicknesses (0.2 mm–1.0 mm) are experimentally investigated via tensile, out of plane, Erichsen, cupping and springback tests for a possible application for solid oxide fuel cells in sheet form unlike the conventional bulk form. Holloman equation is also used to fit the experimental stress-strain curves and the anisotropic behavior of the material is considered by determining Lankford parameters. The tensile test results show that the formability is about 0.29 mm/mm for 0.2 mm thick sheets, indicating the suitability of these sheets for the fabrication of interconnectors by a stamping process with desired channel geometry having dimensions similar to conventional channel dimensions. In addition, for a specific combination of process parameters such as blank holder force and lubrication, the formability can be enhanced as proven by Erichsen and cupping test results. Moreover, the formability is found to increase with increasing the sheet thickness and highly anisotropic behavior is observed. In three point bending tests, the negative springback behavior, namely spring-in, is surprisingly observed for a relatively narrow shoulder distance at all thicknesses and set angle values (θ = 90°–120°).