The mechanism and kinetics of the electrochemical cleavage of azo bond of 2-hydroxy-5-sulfophenyl-azo-benzoic acids

The electrochemical reduction of 2-hydroxy-5-[(4-sulfophenyl)azo]benzoic acid, 2-hydroxy-5-[(3-sulfophenyl)azo]benzoic acid, 2-hydroxy-5-[(2-sulfophenyl)azo]benzoic acid and 2-hydroxy-5-azo-benzoic acid has been carried out in aqueous solutions at glassy carbon electrode using cyclic voltammetry and chronoamperometry. The position of sulfo substituent relative to azo bridge as well as pH of the solution have significant impact on the electrochemical behavior of these compounds. It has been proposed that these compounds are reduced predominantly as hydrazone tautomers resulting in corresponding hydrazo compounds. The overall electrochemical reduction follows DISP2 mechanism, ultimately leading to the 5-amino salicylic acid and sulfanilic acid. The rate determining step is the homogenous redox reaction between intermediate hydrazo compound and 5-amino salicylic acid quinoneimine. The mechanism is proposed in which activated complex of 5-amino salicylic acid quinoneimine and intermediate hydrazo compound is formed with the simultaneous loss of one proton.     

Bread and durum wheat compared for antioxidants contents,and lipoxygenase and peroxidase activities

Potential beneficial components, including proteins, total phenolics, total flavonoids, carotenoids, tocopherols, and DPPH radical scavenging activity, were investigated in wholemeal of ten bread (T. aestivum L.) and ten durum (T. durum Desf.) novel wheat genotypes. In addition, the activity rate of lipoxygenase (LOX) and peroxidase (POD) enzymes implicated in the antioxidant metabolism was determined. The protein contnet and the antioxidant properties varied according to the two different wheat species, as well as, between the different bread and durum wheat genotypes themselves. The results indicated significant differences in proteins and antioxidant compounds between bread and durum wheat. Higher total proteins, wet gluten and antioxidants contents, combined with lower LOX and POD activities, point to a higher nutritive value of durum wheat than bread wheat.     

Deposition of silver ions onto DBD and DCSBD plasma treated nonwoven polypropylene

The aim of this work is plasma activation of nonwoven polypropylene (PP) using two different ambient air plasma sources: volume dielectric barrier discharge (DBD) and diffuse coplanar surface barrier discharge (DCSBD) and its functionalization by silver ion deposition.     

Survey on some contaminants in white sugar from Serbian sugar beet refineries

Refined white sugar is a very pure food product, even though it contains very small amounts of soluble and insoluble impurities. The content of these impurities has nutritional significance and determines the usefulness of sugar for various industrial applications. The main quality criteria used to indicate the content of these impurities are ash and colour. The aim of this paper was to evaluate the quality according to the EU sugar market regime and the content of iron, copper and zinc in white sugar samples from Serbian sugar beet refineries during the 2003 campaign. A total of 166 samples representative of the production of four Serbian sugar refineries were investigated. After wet digestion the concentrations of iron, copper and zinc were determined by flame atomic absorption spectrometry. The mean content of iron, copper and zinc in sugar samples was 0.37 mg/kg, 0.06 mg/kg and 0.02 mg/kg and was significantly different from the average content 0.28 mg/kg, 0.09 mg/kg and 0.07 mg/kg respectively in the analysed European sugar factories. The data were also compared with literature values for commercial white sugar samples from European sugar beet refineries and European legislation set for copper and zinc. Furthermore, the quality of produced sugar was evaluated according to the standards of the European Union indicating that 76% of all investigated Serbian samples belonged to the second sugar quality category.     

A Conjoint-based approach to student evaluations of teaching performance

In recent years, the need for greater accountability and improvement in teaching’s quality has become a major issue in higher education. The results of student evaluation of teaching are increasingly used to make judgments about teaching quality, career advancement, and the funding of teaching itself. An important component of any such student evaluation is the communication of rating results in a manner that allows for fair and meaningful interpretations and comparisons of results by a wide range of evaluation users. In this paper, an approach for a more objective evaluation of university teachers is proposed, one which is based on previously obtained conjoint analysis data concerning criteria importance from a student’s point of view. Therein, an illustrative example is given to demonstrate the efficiency and practical usage of such a proposed approach.     

Structural studies on Ca3Al4MgO10 (C3A2M)—A ternary phase in the system CaO–Al2O3–MgO

In a sequence of temperature-dependent solid-state reactions in the system CaO–Al₂O₃–MgO the formation of the ternary phase Ca₃Al₄MgO₁₀ or C₃A₂M has been studied. Whereas the compound could not be prepared at 1200°C, a yield of 85 wt.-% of Ca₃Al₄MgO₁₀ was obtained at 1320°C (incongruent melting point: 1330°C). Powder diffraction data compare well with results of previous investigations from the 1960s. Single crystals of Ca₃Al₄MgO₁₀ could be retrieved from the sinter-pellets. Basic crystallographic data are as follows: orthorhombic symmetry, space group Pbcm, a = 5.14073(8), b = 16.7576(2), c = 10.70977(16) Å, V = 922.61(2) ų, Z = 4. Using synchrotron diffraction data it was possible to solve the crystal structure. Least-squares refinements resulted in a residual of R(|F|) = 0.021 for 1000 independent observed reflections with I > 2σ(I) and 97 parameters. The structure contains [TO₄]-tetrahedra (T=Al,Mg) forming a three-dimensional (3-D) framework whose topological characteristics have been determined. Al-Mg distributions on the different T-sites have been studied. The calcium cations are located in voids of the network. More than 50 years after its first observation our investigation clarifies the crystal structure of a compound belonging to a system that is of relevance for several fields of materials science.     

Reduction of solid content in starch industry wastewater by microfiltration

Wastewater obtained in the production process of wheat starch and vital wheat gluten was treated by microfiltration through a ceramic tubular membrane with 200 nm pore sizes. The consumption of process water would thus be reduced, the starch would be recovered to a greater extent and the wastewater problem would consequently be solved. Reduction of the occurrence of polarization layer on the membrane and the constant wastewater permeate flux through the membrane was maintained by inserting of the mixer Kenics inside the membrane tube. The maximum value of the permeate flux (24 L m⁻² h⁻¹) without the use of a static mixer was achieved at 3 × 10⁻⁵ Pa and at a flow rate of 150 L/h, for wastewater samples initially allowed to settle for 4 h prior microfiltration. Under the very same conditions of the working parameters, the use of a static mixer enables a flux that is up to two or three times more intensive compared to the values obtained without using a mixer. Microfiltration reduces the wastewater dry matter from 11 000 to 4000 mg/L, lessens the chemical oxygen demand by 74%, i.e. from 21 000 to 5100 mgO₂/L and significantly decreases the values of the suspended matter, namely from 9000 to 300 mg/L.     

Influence of Soft Cocoa Butter Equivalents on Color and Other Physical Attributes of Chocolate

The physical characteristics and color of chocolate depend on the physical properties and crystallization behavior of the fat phase. In this study, the fat phase of chocolate samples contains cocoa butter from Ghana and soft cocoa butter equivalent (CBE). The laboratory-made chocolate samples were tempered at three different precrystallization temperatures (25, 27 and 29 °C), using three different concentrations of CBE (3, 5 and 7%), calculated as percentage of the chocolate. Physical characteristics of chocolate, namely thermoreographic parameters and solid fat content (SFC), were measured. The color of the chocolate was determined instrumentally, before and after thermo-cycle testing at 32/20 °C. It was found that CBE changed the melting properties of chocolate produced with cocoa butter from Ghana, which is of moderate hardness. It was determined that the optimum precrystallization temperature for chocolate mass with addition of CBE in the given conditions of measurement was 27 °C, the temperature that resulted in the best fat bloom resistance.     

Application of fuzzy logic for evaluation of the level of social acceptance of waste treatment

The social aspect is very important in sustainability assessment of waste treatment technique, as well as making decision on their application and planning. In recent years, it is becoming evident that a waste treatment technique, which ignores social aspects, is doomed to failure. The most commonly used social indicators are: number of jobs created, level of social acceptance, public knowledge, public health etc. The most of them are qualitative and measuring the sustainability and quantifying the social dimension of sustainability are difficult tasks. This paper presents the application of fuzzy logic for evaluating the social indicator—level of social acceptance. The fuzzy set theory and fuzzy logic were used to develop a model for the evaluation of level of social acceptance, due to the lack of data, uncertainties, and qualitative character of indicators and also to provide effective way to include knowledge and gained experience on the process. A questionnaire was applied as instrument for data collection. The fuzzy model was verified using the city of Ni? as a case study. The results obtained using the developed fuzzy model, shows that the highest level of social acceptance in the city of Ni? is for recycling (57.47 %) and the lowest level of social acceptance is for incineration (17.74 %). The presented study suggests an innovative methodology for evaluation of level of social acceptance of certain waste treatment based on fuzzy logic approach and can be used for ranking of waste management scenarios in the sustainability assessment.