The effect of contact of copper sulphide grains on the initial rate of leaching in oxygenated sulphuric acid solution

The initial stage of leaching of chalcocite, bornite, and chalcopyrite as well as chalcocite-chalcopyrite and bornite-chalcopyrite mixtures in oxygenated aqueous sulphuric acid was investigated at 368 K. It was determined that chalcopyrite accelerates the rate of copper leaching from chalcocite due to grain contact between chalcocite and chalcopyrite. In contrast, chalcopyrite decreases the rate of dissolution of bornite.     

Chicken muscle homogenate gelation properties: effect of pH and muscle fiber type

Gelation properties of chicken breast and thigh muscle homogenates at a protein concentration of 4.5% under different pH conditions (5.80–6.60) and those of myofibrillar proteins at a protein concentration of 2% were compared to determine the influence of muscle fibre types on gelation. The optimal gelling pH for breast muscle homogenates (pH 6.30) was slightly higher than that for thigh muscle homogenates (pH 5.80–6.30), a similar trend was found for the isolated chicken myofibrillar proteins (pH 6.00 for breast and 5.50 for leg). Similarly, the pH values at which breast muscle homogenate gels were weaker (pH<6.20) or stronger (pH6.20) than thigh muscle homogenate gels were higher when compared with chicken breast and leg myofibrillar protein gels (pH<5.80 and pH>5.90, respectively).     

Implantation of silicon ions into a surface layer of the Ti6A14V titanium alloy and its effect upon the corrosion resistance and structure of this layer

The effect of silicon ion implantation upon the corrosion resistance and structure of the surface layers formed during the implantation in the Ti6A14V titanium alloy was examined. The silicon doses were 0.5, 1.5, 3.0 and 4.5 × 10¹⁷Si⁺/cm², and the ion beam energy was 100 keV. The corrosion resistance of the samples exposed to a 0.9% NaCl solution at a temperature of 37 °C was measured using electrochemical methods. The structure of the surface layers formed during the implantation was examined by a transmission electron microscope (TEM). The results of the corrosion resistance examinations have shown that the unimplanted and 0.5 × 10¹⁷Si⁺/cm² implanted samples undergo uniform corrosion. At higher silicon doses, the samples show pitting corrosion. The highest corrosion resistance was shown by the alloy implanted with 0.5 × 10¹⁷Si⁺/cm². It has been found that, after a long-term (1200 h) exposure to a 0.9% NaCl solution, the corrosion resistance of the samples is greater than that observed after a short-term exposure. TEM examinations have shown that, beginning from a dose of 1.5 × 10¹⁷Si⁺/cm², the surface of the Ti6A14V alloy samples becomes amorphous. Heating of the 1.5 × 10¹⁷Si⁺/cm² implanted samples at 200 and 500 °C does not change their structure, whereas after heating at 650 °C, the amorphous phase vanishes.     

Effect of Biaxial Load on Crack Deflection/Penetration at Bi-material Ceramic Interface

The paper investigates the effect of the biaxial loading on crack deflection/penetration at a bi-material ceramic interface. A biaxially loaded geometry was numerically investigated using Finite Element Analysis in order to determine the energy release rate. The obtained results could be used in conjunction with a fracture criteria at interface for estimating the path of the crack after the interface was reached.     

Radiation stability of ceramics: Test cases of zirconia and spinel

The study of the effects of radiation in ceramics of potential use in electronic, space and nuclear industries appears to be a major challenge in the next decades. The collect and analysis of data dealing with the production and recovery of radiation damage in this type of materials are thus tasks of prime interest. In this article, we present a review of the main structural and chemical modifications observed in test case ceramics (yttria-stabilized zirconia and magnesium-aluminate spinel) submitted to ion bombardment and thermal treatments. We show that the stability under irradiation depends on the intrinsic properties of the materials and on irradiation parameters such as the ion energy, fluence and temperature. We also demonstrate that the recovery of damage upon annealing at elevated temperatures induces drastic physico-chemical modifications of the matrix.     

Crime hotspot mapping using the crime related factors—a spatial data mining approach

The technique of Hotspot Mapping is widely used in analysing the spatial characteristics of crimes. The spatial distribution of crime is considered to be related with a variety of socio-economic and crime opportunity factors. But existing methods usually focus on the target crime density as input without utilizing these related factors. In this study, we introduce a new crime hotspot mapping tool—Hotspot Optimization Tool (HOT). HOT is an application of spatial data miming to the field of hotspot mapping. The key component of HOT is the Geospatial Discriminative Patterns (GDPatterns) concept, which can capture the differences between two classes in a spatial dataset. Experiments are done using a real world dataset from a northeastern city in the United States and the pros and cons of utilizing related factors in hotspot mapping are discussed. Comparison studies with the Hot Spot Analysis tool implemented by Esri ArcMap 10.1 validate that HOT is capable of accurately mapping crime hotspots.     

THE INFLUENCE OF N-ALKANES ON WETTABILITY DF LOW COAL RANKS

Contact angle measurements were carried out in coal / n-alkanes film - air bubble - water systems. Then theoretical an analysis of the equilibrium state of that system was carried out on the basis of the components of the surface free energy of coal of various ranks. The contact angles were measured for four ranks of Polish coal which surfaces were covered with n-alkanes film in the homological series from n-hexane to n-hexadecane. On the basis of the studies and calculations carried out we have concluded that the values of the contact angle depend on the rank of coal, a thickness of n-alkane film and its structure and the presence of water film under the air bubble. It was also found that the changes of the- values of the contact angles measured in the mentioned sytems as a function of the number of contacted air bubbles were similar to those calculated on the basis of the solution of Young equation in function of the surface free energy of coals precovered with n-alkane film.     

Molecular characterization of penicillin-resistant Streptococcus pneumoniae isolates from Bulgaria

As part of an ongoing surveillance program of antibiotic-resistant Streptococcus pneumoniae in Sofia, Bulgaria, 120 penicillin-resistant strains (PRSP) (most of them recovered from children hospitalized with pneumococcal disease) were analyzed by microbiological and molecular methods. Several unique features of this collection are of particular interest. (i) Most isolates (112 of 120) were also resistant to trimethoprim-sulfamethoxazole (SXT) (97 of 120 isolates, or 80%), and over 70% (86 of 120) of the isolates were resistant to at least three antibiotics in addition to penicillin. (ii) Close to 80% of all isolates were represented by large clusters of bacteria, each with a unique serotype, antibiotype, and chromosomal macrorestriction pattern (determined by pulsed-field gel electrophoresis), as well as unique restriction fragmentation length polymorphisms of the penicillin-binding protein genes pbp1a, pbp2x, and pbp2b. (iii) A large proportion (45 of 120, or 38%) of the strains belonged to two internationally spread epidemic clones of S. pneumoniae, the first expressing capsular type 23F and the second expressing serotype 9. (iv) A unique Bulgarian cluster composed of eight serotype 19F isolates was resistant to tetracycline, SXT, cefotaxime, and extremely high levels of penicillin and erythromycin. Nevertheless, this clone did not react with either the erm or the mef DNA probes, and thus the mechanism of macrolide resistance in this group of PRSP remains to be elucidated.