Spontaneous Precipitation in the System Uranyl(2+ )nitrate Potassium Hydroxide - Phosphoric Acid - Water

The precipitation system U02(NOs)2-KOH-H3P04-H20 (at 298 K) aged for 1 day and for 30 days is examined ([U02(NOs)2] = = 1 · 10-a mol dm-3, [KOH] varied from 1 · 10-6 to 6 · 10-1 mol dm-3, [H3P04] from 2 · 10-4 to 6 · 10-1 mol dm-3 and 1.5 <pH< 11.5). The precipitation and phase boundaries are determined. The solid phases U02HP04 · 4 H20(s) and (U02)s(P04)2 · 8 H20 are stable at [KOH] < 1 · 10-3 mol dm-3, 1.5 <pH < 4.0. Uranates precipitate at pH > 9.5. The stability region of KU02P04 · 3 H20(s) is found at high concentrations of KOH and H3P04. X-ray diffraction pattern of this compound is given. According to the precipitation boundary after 30 days (equilibrium conditions) the solubility product of KU02P04 · 3 H20 is determined: log ([K+] · · [U022+] [P043-]) = -- 26.28 (at I =0 mol dm-3)

Identification and Characterization of Alkaline Uranyl(2 +) Phosphates

The spontaneous precipitation in the systems U02(N03)2- -MOH-HaP04--H20 and U02(N03)2-MNOa-H3P04- H20 (M = = Li, Na, K, Rb, Cs) is examined. The formation of alkaline- uranyl(2+) phosphates polyhydrates is detected: M[U02P04] · · n H20 (n = 4 for M = Li, n = 3 for M = Na, K, Rb and n = 2.5 for M =Cs). The X-ray powder patterns of these compounds are determined and compared with that of H30[U02P04] · 3 H20. A close structural relation within this series is observed. The size of the alkaline ionic species in the particular compound affects the content of crystalline water in the unit cell

Unique extremality

Extremal mappings have been one of the main topics in the theory of quasiconformal mappings since its earliest days, when Grötzsch solved the extremal problem for two rectangles. Grötzsch showed that among all quasiconformal mappings from a rectangle R_1 onto another rectangle R_2, mapping the sides of R_1 onto the corresponding sides of R_2, there exists a unique mapping with minimal dilatation (see [Gr]). Later, Teichmüller [T] generalized Grotzsch's ideas and found many extremal quasiconformal mappings, including the uniquely extremal mapping f in the set of all quasiconformal mappings homotopic to a given sense-preserving homeomorphism between two compact Riemann surfaces R and S = f(R) of genus greater than 1. In a neighborhood of all but finitely many points on the compact Riemann surface R, the extremal map f could be expressed as a conformal map followed by an affine map followed by a conformal map. The Beltrami coefficient off is of the form k|φ|φ, where 0 ≤ k < 1 and φ is an integrable holomorphic quadratic differential

Electric Field Effect in Ultrathin Films near the Superconductor-Insulator Transition

The effect of an electric field on the conductance of ultrathin films of metals deposited on substrates coated with a thin layer of amorphous Ge was investigated. A contribution to the conductance modulation symmetric with respect to the polarity of the applied electric field was found in regimes in which there was no sign of glassy behavior. For films with thicknesses that put them on the insulating side of the superconductor-insulator transition, the conductance increased with electric field, whereas for films that were becoming superconducting it decreased. Application of magnetic fields to the latter, which reduce the transition temperature and ultimately quench superconductivity, changed the sign of the reponse of the conductance to electric field back to that found for insulators. We propose that this symmetric response to capacitive charging is a consequence of changes in the conductance of the a-Ge layer, and is not a fundamental property of the physics of the superconductor-insulator transition as previously suggested.Comment: 4 pages text, 4 figure

Kinetics and mechanism of sphalerite leaching by sodium nitrate in sulphuric acid solution

Interest for application of hydrometallurgical processes in a processing of complex sulphide ores and concentrates has increased in recent years. Their application provides better metal recoveries and reduced emission of gaseous and toxic ageneses in the environment. The kinetics and mechanism of sphalerite leaching from complex sulphide concentrate with sulphuric acid and sodium nitrate solution at standard conditions was presented in this paper. The influences of temperature and time on the leaching degree of zinc were investigated and kinetic analysis of the process was accomplished. With temperature increasing from 60 to 90°C, the zinc leaching increased from 25.23% to 71.66% after 2 hours, i.e. from 59.40% to 99.83% after 4 hours. The selected kinetic model indicated that the diffusion through the product layer was the rate-controlling step during the sphalerite leaching. The activation energy was determined to be 55 kJ/mol in the temperature range 60-90°C. XRD, light microscopy and SEM/EDX analyses of the complex concentrate and leach residue confirmed formation of elemental sulphur and diffusion-controlled leaching mechanism

Influence of mechanical activation on microstructure and crystal structure of sintered MgO-TiO2 system

Mixtures of MgO-TiO2 were mechanically activated using high-energy planetary ball mill during 5, 10, 20, 40, 80 and 120 minutes. Sintering process was preformed in air at 1100°-1400°C for 2h. The decrease in powder's particle size was noticed as the time of mechanical activation increased and confirmed by particle size analyzer. XRD analyses were performed in order to acquire the information about phase composition. Different ratio mixtures of MgTiO3 and Mg2TiO4 are present within all sintered samples. The effect of tribophysical activation on microstructure was investigated by scanning electron microscopy. The differential thermal gravimetric analysis has been performed in order to investigate thermal behaviour of the mixtures.Smeše MgO-TiO2 su mehanički aktivirane u visoko-energetskom planetarnom mlinu tokom 5, 10, 20, 40, 80 i 120 minuta. Fazni sastav je određen rendgenskom difrakcijom. Sa porastom vremena mlevenja, primećeno je smanjenje veličine čestica praha. Takođe, ispitan je i efekat tribofizičke aktivacije na mikrostrukturu praha metodom skenirajuće elektronske mikroskopije. Radi ispitivanja termičkih svojstava praha, urađena je diferencijalna termijska analiza. Proces sinterovanja izveden je u vazduhu u temperaturnom opsegu od 1100°-1400°C tokom 2 sata. U svim sinterovanim uzorcima uočeno je prisustvo dve faze MgTiO3 i Mg2TiO4 ali njihov međusobni odnos koncentracija varira u odnosu na temperaturu sinterovanja

Hygrophorus eburneus, edible mushroom, a promising natural bioactive agent

It is known that many edible mushrooms have important medicinal properties, including effects on different types of cancers. This is the first report regarding the neuroprotective, antimicrobial, antioxidative and anticancer activities of the acetone extract of edible mushroom Hygrophorus eburneus. Neuroprotective potential was evaluated by measuring the capacity of the extract to inhibit acetylcholinesterase. In this assay, the tested extract showed activity against acetylcholinesterase in a dose-dependent manner where the percentage of inhibition ranged from 13.19 to 46.44 %. The antimicrobial potential was determined by the microdilution method against five species of bacteria and eight species of fungi and the results of this method exhibited moderate antimicrobial activity of H. eburneus with MIC values ranging from 6.25 to 25 mg/mL. Antioxidant activity was evaluated by measuring the scavenging capacity of the tested sample on DPPH and superoxide anion radicals, by the reducing power assay and by measuring the amounts of total phenolics in extract. As a result of the study, H. eburneus extract showed a potent antioxidant activity (IC50 were 102.93 μg/mL for DPPH radical scavenging activity and 123.27 μg/mL for superoxide anion radicals scavenging) while absorbances for reducing power assay were from 0.0235 to 0.1161. The total phenolic content in the extract was 9.27 µg PE/mg. Finally, anticancer effects were evaluated by MTT test for cytotoxicity, acridine orange/ethidium bromide staining for detection of the type of cell death and wound healing assay for antimigratory effects on human colorectal cancer cell line (HCT-116) and human breast cancer cell line (MDA-MB-231). The results for cytotoxicity and apoptosis were measured after 24 and 72 h and for anti-migratory effect after 12 and 24 h. The tested H. eburneus mushroom extract expressed cell selectivity, with notable cytotoxic effects observed on HCT-116 cells, with a strong proapoptotic potential. The migration of HCT-116 cells was significantly inhibited, while MDA-MB-231 cells were less sensitive to the treatment. The results of this study revealed that the tested extract had relatively strong neuroprotective, antimicrobial, antioxidant, and anticancer effects. It suggests that this mushroom can be proposed as a novel source of nutraceuticals and pharmaceuticals