Search

Graphical abstract:

In the present work, the composition and relative density of light gasoil of catalytic cracking (LGCC) were studied using chromato‐mass‐spectrometry and its key physical properties were numerically simulated using molecular dynamics. We have studied the distribution of hydrocarbon compounds over narrow fractions of LGCC. We have applied the ASTM D2892‐11a standard distillation to find the component composition of LGCC and its narrow fractions obtained from a mixture of West Siberian oils. Molecular dynamics simulations were performed using the GROMOS96 54a7 force field for the ensemble of constant number of particles (N), pressure (P) and temperature (T) (NPT) ensemble under the constant temperature and constant pressure conditions. The topologies of the structures under study were generated by the automated topology builder (ATB) service. Both the chromatographic mass spectrometry experiments and molecular dynamics simulations indicate the contents of aromatic hydrocarbons in LGCC from the mixture of West Siberian oils up to 80 wt%. The composition and relative density of light gasoil of catalytic cracking (LGCC) were studied using chromato‐mass‐spectrometry and its key physical properties were numerically simulated using molecular dynamics. We have studied the distribution of hydrocarbon compounds over narrow fractions of LGCC. Both the chromatographic mass spectrometry experiments and molecular dynamics simulations indicate the contents of aromatic hydrocarbons in LGCC from the mixture of West Siberian oils up to 80 wt%.

In the preparation of nanoparticles (NPs) by the nanoprecipitation method, emulsifiers play a key role for NPs' characteristics. The present study aimed to investigate the combined emulsifier effect on ibuprofen loaded poly(lactic-co-glycolic acid) (PLGA) NPs' characteristics and anticancer activity. Ibuprofen loaded PLGA NPs were prepared by nanoprecipitation using different concentrations of PVA (poly(vinyl alcohol)) or PVA–TPGS (d-α-tocopherol polyethylene glycol 1000 succinate) combination as emulsifier. It was found that encapsulation efficiencies of NPs varied between 17.9 and 41.9 % and the highest encapsulation efficiency was obtained with 0.5% PVA + 0.1% TPGS (coded as PLGA PVA/TPGS NPs). PLGA PVA/TPGS NPs were characterized and compared with PLGA PVA NPs, which was obtained by 0.5% PVA alone. Polydispersity index of PLGA PVA/TPGS and PLGA PVA NPs were found to be 0.08 and 0.15, respectively. Incorporation of TPGS with PVA slightly decreased the initial ibuprofen release. Transmission electron microscopy analyses demonstrated a nearly uniform particle size distribution and spherical particle shape of the PLGA PVA/TPGS NPs. Additionally, PLGA PVA/TPGS NPs were significantly more cytotoxic than PLGA PVA NPs on the MCF-7 (human breast adenocarcinoma cells) and Caco-2 (human epithelial colorectal adenocarcinoma) cells (p<0.05). Also PLGA PVA/TPGS NPs were not cytotoxic on normal cells (L929, mouse healthy fibroblast cells) (p>0.05). In conclusion, these results indicated that using a combination of TPGS and PVA as an emulsifier in nanoprecipitation could be a promising approach for preparing ibuprofen loaded PLGA NPs because of their improved characteristics and anticancer activity.

A stir casting process was developed to produce aluminium alloy composites containing two different sizes and volume fractions of B4C particles up to 10 vol.-. Manufacturing of B4C particle reinforced 2024 aluminium alloy composites was modified so as to reduce the processing temperature. In the present study, in order to improve incorporation of the B4C particles by 2024 aluminium alloy melt, a novel pretreatment process before stir casting was attempted, and a significant improvement was gained. This finding showed that the treatment modified the surface condition of boron carbide powders via the removal of oxides. The comparison of added and incorporated particle ratios (the yield rate) indicated that the amount of incorporated particles decreased with increasing volume fraction and decreasing size of particles. Scanning electron microscopic observations of the microstructures revealed that the dispersion of the coarser sizes of particles was more uniform, while finer particles led to agglomeration of the particles and porosity. The results showed that the density of the composites decreased with increasing particle volume fraction and decreasing particle size, whereas the porosity and hardness values increased with increasing particle volume fraction and decreasing particle size.

The recovery of copper and cobalt from ancient copper slags from the Küre region of Turkey was investigated. A fayalitic-type of ancient copper slag containing 1.24% Cu, 0.53% Co and 53.16% Fe were subjected to an experimental study. Two different routes were followed to recover the metal values. The first route was roasting the slag with pyrite followed by leaching. The second route was flotation of the slags, roasting of the flotation tailings with pyrite and leaching. The second route was found to be suitable for the treatment of the copper slag studied. In the flotation step, a copper concentrate containing approximately 11% Cu was produced with a 77% recovery while 93% of the cobalt stayed in the tailings. In the roasting experiments, the effects of roasting time, pyriteislag ratio and roasting temperature on the dissolution efficiencies of Cu and Co were investigated, and the optimum conditions were determined. In the tests, 87% of the cobalt dissolution was observed after one hour of roasting at 500°C with a pyrite:slag ratio of 3:1. The copper dissolution in the tests was 31%. Based on the results of this study, a process flowsheet is proposed for the evaluation of these slags.

A polypyrrole electrode with ferrocene mediator is prepared and its sensitivity to hydrogen peroxide is investigated. The polypyrrole is deposited upon a 0.5 cm2Pt plate by the polymerization of pyrrole by scanning the electrode potential between 0.0 and 0.9 V at a scan rate of 50 mV/s. The platinum/polypyrrole-ferrocene (Pt/PPy-Fc) electrode is prepared by adding ferrocene to the coverage medium. The electrode’s sensitivity to hydrogen peroxide is investigated at room temperature using 0.025 M phosphate buffer at pH 7. The working potential is 0.7 V, the concentrations of pyrrole and ferrocene are 0.2 M and 10 mM. Polypyrrole was coated on the electrode surface within 26 cycles.A polypyrrole electrode with ferrocene mediator is prepared and its sensitivity to hydrogen peroxide is investigated. The polypyrrole is deposited upon a 0.5 cm2Pt plate by the polymerization of pyrrole by scanning the electrode potential between 0.0 and 0.9 V at a scan rate of 50 mV/s. The platinum/polypyrrole-ferrocene (Pt/PPy-Fc) electrode is prepared by adding ferrocene to the coverage medium. The electrode’s sensitivity to hydrogen peroxide is investigated at room temperature using 0.025 M phosphate buffer at pH 7. The working potential is 0.7 V, the concentrations of pyrrole and ferrocene are 0.2 M and 10 mM. Polypyrrole was coated on the electrode surface within 26 cycles.

Not Available

Microflotation tests, electrokinetic and electrochemical measurements were carried out to investigate the flotation behavior of pyrite samples taken from different regions of Turkey. Chemical analyses and mineralogical examinations showed that these pyrite samples have different impurities and structural properties. The flotation characteristics of pyrites using ethyl xanthate were similar. Zeta potential measurements were carried out to investigate the effects of pH, conditioning time and collector addition on the flotation of pyrites. Electrochemical measurements were conducted to understand the flotation mechanism using the potential-pH diagrams drawn for the system studied. The results revealed that impurities and structural differences among the various pyrite samples have little or no effect on their flotation behaviors. However, the differences observed in practice originate from the types and the amount of ions dissolved from the associated minerals. It was found that copper ions activate the pyrite flotation due to the formation of copper xanthate and dixanthogen.

Gold losses in the cyanidation of refractory ores are mainly due to the presence of sulfide and carbonaceous materials. Sulfide minerals in the ore can be oxidized by hypochlorite generated electrochemically in the leaching reactor. The electrooxidation of a gold-bearing sulfide concentrate that contains pyrite, pyrrhotite and arsenopyrite was investigated in an electrochemical cell with 10% (by weight) NaCl electrolyte. The relative amount of iron dissolved by the oxidation of sulfide minerals increased with the duration of the test under constant applied current and leveled off at about 80% after 8 hours. Increasing the pulp density increased the current efficiency and the total amount of material oxidized. Cyanidation tests after 38% iron removal by electrooxidation resulted in a gold extraction increase of approximately 29% and a cyanide consumption decrease of about 31%.

In this study production of rapidly solidified metal powders by water cooled rotating disc has been investigated. A rotating disc was cooled by water which was not in contact with the molten metal and the produced powders during atomisation. This method is an effective process to produce rapidly solidified powders and ribbons.Tin, lead, aluminium, zinc, and AA 2014 aluminium alloy powders and ribbons were produced using different types of discs. Parameters such as disc rotation velocity, disc shape, diameter of liquid metal stream, and superheat were investigated. The results showed that increasing disc rotation velocity, decreasing liquid metal stream diameter, and increasing superheat resulted in finer particles as expected.Different types of discs such as flat, flat with fins, and cone with fins were used to investigate the effects of the disc geometry. Performance of the flat type disc with rectangular fins was better than that of the others.Metallographic examinations showed that estimated cooling rates of atomised AA 2014 powders were between 104–105K s-1depending on particle size. With the ribbons cooling rates were relatively higher, of the order of 105–106K s-1.

Despite its importance in various diverse industries, research on beneficiation strategies of boron minerals has not received enough attention. Boron minerals are primarily upgraded by wet processing methods. However, severe environmental constrains have accelerated the development of dry processing techniques such as calcination. Interestingly, the boron minerals colemanite, ulexite and borax undergo decrepitation, shrinkage and expansion, respectively, upon heat treatment. Each mineral then requires a different beneficiation scheme. In this study, laboratory and pilot-plant studies conducted in our laboratories on the calcination of boron minerals are briefly reviewed and their implications to commercial operations are discussed.

Liquid tin solution calorimetry has been used to measure the enthalpies of formation of iron-cobalt alloys covering the composition range of 7.6 to 91.0 at.-% iron. Measurements at two temperatures (475 and 775 K) allowed extrapolation to 923 K at which temperature free-energy measurements are available for combination with the enthalpies to determine entropies of formation. The low values of these lead to speculation about the possible sources of substantial negative contributions and point to the necessity for low-temperature heat capacity measurements to resolve the problem. The compositional dependence of the enthalpy results indicates a maximum at the non-stoichiometric composition of 53 at-% iron. This, and deductions concerning the value of the order/disorder transformation, are in keeping with previous work on the system.

A 64-year-old man suffering from an acute posterior wall myocardial infarction underwent primary percutaneous coronary intervention. After several aspiration attempts, tirofiban infusion and pre- and post-dilatation, a bare-metal stent was successfully implanted in the culprit right coronary artery. While the patient did not show any neurological symptoms before or during the procedure, he exhibited hemiplegia and loss of spontaneous speech. Additional magnetic resonance imaging showed an extensive brain stem infarction. This is the first report of a brain stem infarction as a complication of percutaneous coronary intervention.