Synthesis of BaFe12O19-BaTiO3 multiferroics by mechanical activation

A mixture of polycrystalline powders of Fe (70 % wt.) and BaTiO3 (30 % wt.) was ball-milled in a planetary mill under air atmosphere, for different time intervals: 60, 120, 180, 240, 300 and 360 min. During the mechanical activation, the powder was exposed to oxygen from the air, resulting in formation of iron oxides: FeO and then Fe2O3 and Fe3O4. XRD and SEM analyses of the activated powders revealed that the weight fraction of the iron oxides in the mixture and microcrystal size depend on the activation time. For the powders activated for different time intervals, average crystallite size (Dhkl), dislocation density (ρn) and average microcrystal size of BaTiO3 and Fe were determined. In order to investigate the influence of thermally induced structural changes on magnetic properties, the change of magnetic properties of the pressed activated powders during multiple heating in a magnetic field of 10KA/m was measured. Maximum magnetization of the samples was reached after heating at 620 K. Pressed powder samples were sintered at temperatures of 1100 oC and 1200 °C for 2h giving the different phase diagrams. The samples sintered at 1100 oC include BaTiO3, BaFe12O19 and BaFeO2,67 as the dominant components. The samples sintered at 1200 °C containing only two components, BaTiO3 and BaFe12O19, exhibited pronounced ferromagnetic and ferroelectric propertie

A Multistage Stochastic Programming Approach to the Dynamic and Stochastic VRPTW - Extended version

We consider a dynamic vehicle routing problem with time windows and stochastic customers (DS-VRPTW), such that customers may request for services as vehicles have already started their tours. To solve this problem, the goal is to provide a decision rule for choosing, at each time step, the next action to perform in light of known requests and probabilistic knowledge on requests likelihood. We introduce a new decision rule, called Global Stochastic Assessment (GSA) rule for the DS-VRPTW, and we compare it with existing decision rules, such as MSA. In particular, we show that GSA fully integrates nonanticipativity constraints so that it leads to better decisions in our stochastic context. We describe a new heuristic approach for efficiently approximating our GSA rule. We introduce a new waiting strategy. Experiments on dynamic and stochastic benchmarks, which include instances of different degrees of dynamism, show that not only our approach is competitive with state-of-the-art methods, but also enables to compute meaningful offline solutions to fully dynamic problems where absolutely no a priori customer request is provided.Comment: Extended version of the same-name study submitted for publication in conference CPAIOR201

Microstructure and crystal growth in thermally treated Fe73,5Cu1Nb3Si15,5B7 alloy

Thermal treatment of Fe73.5Cu1Nb3Si15.5B7 amorphous alloy induces structural changes, including crystallization of several different phases and subsequent crystal growth. X-ray diffraction combined with differential scanning calorimetry were used to investigate these, to determine kinetic parameters and mechanism of individual steps, and the dimensionality of crystal growth using Matusita-Sakka method and texture analysis. It was found that after the alloy becomes fully crystalline, crystal growth of individual phases is, in general, impeded, leading to decreased dimensionality of growth. However, this does not impact the texture, due to lack of preferred direction of crystal growth.Physical chemistry 2012 : 11th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 24-28 September 201

Profiling of microorganism-binding serum antibody specificities in professional athletes

The goal of this work was to elucidate similarities between microorganisms from the perspective of the humoral immune system reactivity in professional athletes. The reactivity of serum IgG of 14 young, individuals was analyzed to 23 selected microorganisms as antigens by use of the in house ELISA. Serum IgM and IgA reactivity was also analyzed and a control group of sex and age matched individuals was used for comparison. The obtained absorbance levels were used as a string of values to correlate the reactivity to different microorganisms. IgM was found to be the most cross reactive antibody class, Pearson’s r = 0.7–0.92, for very distant bacterial species such as Lactobacillus and E. coli.High correlation in IgG levels was found for Gammaproteobacteria and LPS (from E. coli) (r = 0.77 for LPS vs. P. aeruginosa to r = 0.98 for LPS vs. E.coli), whereas this correlation was lower in the control group (r = 0.49 for LPS vs. P. aeruginosa to r = 0.66 for LPS vs. E.coli). The correlation was also analyzed between total IgG and IgG subclasses specific for the same microorganism, and IgG2 was identified as the main subclass recognising different microorganisms, as well as recognising LPS. Upon correlation of IgG with IgA for the same microorganism absence of or negative correlation was found between bacteria-specific IgA and IgG in case of Lactobacillus and Staphylococcusgeni, whereas correlation was absent or positive for Candida albicans, Enterococcusfaecalis,Streptococcus species tested in professional athletes. Opposite results were obtained for the control group. Outlined here is a simple experimental procedure and data analysis which yields functional significance and which can be used for determining the similarities between microorganisms from the aspect of the humoral immune system, for determining the main IgG subclass involved in an immune response as well as for the analysis of different target populations

Mass and momentum transfer in packed beds of spherical inert particles

Mass transfer coefficients between fluid and immersed sphere in liquid dense and loose packed beds of spherical inert particles have been studied experimentally using column 40 mm in diameter. Mass transfer data were obtained by studying transfer of benzoic acid from a large spherical particle to flowing water using the disssolution method. In all runs mass transfer rates were determined in the presence of inert spherical glass particles 0.54, 0.68, 1.20, 1.94, 2.98 and 4.98 mm in diameter. Measurements have covered a particle Reynolds number range from 0.35 to 400 and one Schmidt number (25°C) 969. Experimental data are correlated by the widely used general form, j D = f(Re p ). The resulting correlation for packed beds, which covers dense and loose packed beds, is j D = 0.395ε -1,2 Re p -0,39 . In the same experimental systems a relationship between friction factor and particle Reynolds number has been studied. The results indicate that numerical constants in Ergun equation are system specific

Kinetics of multi-step processes of thermal degradation of Co(II) complex with N-benzyloxycarbonylglycinato ligand. Deconvolution of DTG curves

Thermal decomposition of Co(II) complex with N-benzyloxycarbonylglycinato ligand, [Co(N-Boc-gly)2(H2O)4]•2H2O, in non-isothermal conditions occurs in three complex steps. In order to investigate detail kinetics of first two steps, dehydration and ligand degradation, DTG curves were deconvoluted using product of Gaussian and Lorentzian function. It was shown that process of complex dehydration consists of three, while process of ligand fragmentation consist of five elementary steps. For elementary steps the kinetic triplet (Ea, Z and f(α)) was determinated. Kinetic parameters were obtained by application of IKP method. On the basis of Màlek’s criteria and Šesták-Berggren's method, Šesták-Berggren's model, f(α)=αM(1-α)N was suggested for all elementary steps, while Master plot method and Perez- Maqueda criteria confirmed suggested reaction models. The thermodynamic activation parameters were calculated for process of complex dehydration, and lifetime for first elementary step of the dehydration and ligand degradation processes was estimated. [Projekat Ministarstva nauke Republike Srbije, br. 172055

Prevalence of speech and language disorders in children in northern Kosovo and Metohija

On the territory of the northern part of Kosovo and Metohija (Kosovo municipalities Mitrovica, Zvecan, Leposavic and Zubin Potok) a study is conducted in primary schools in order to determine the presence of speech-language disorders in children of early school age. Data were collected from the teachers of the third and fourth grades of primary schools in these municipalities (n = 36, which include a total number of 641 student). The results show that the number of children with speech and language disorders represented in the different municipalities of the research vary (the largest is in Leposavic, the smallest is in Zvecan), then 3/4 the total number of children with speech and language disorders are boys. It is also found that the speech-language disorders usually appear from the very beginning of schooling and that the examined teachers recognize 12 types of speech-language disorders in their students. Teachers recognize dyslexia as the most common speech-language disorder, while dysphasia and distortion are the least common, in the opinion of the teachers. The results show that children are generally accepted by their peers, but only during schooling; then, there is a difference in school success between children with speech and language disorders and children without any speech-language disorders. It also found that the teachers' work is generally not affected by the children with speech and language disorders, and that there is generally an intensive cooperation between teachers and parents of children with speech and language disorders. The research and the results on prevalence of speech-language disorders in children in northern Kosovo and Metohija can be considered as an important guidelines in future work