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

UTJECAJ DUŽINE TRANSPORTA I MIJEŠANJA GRUPA NA KAKVOĆU JUNEĆIH TRUPOVA SIMENTALSKIH BIKOVA

In the last few years, beef producers have had great problems with beef distribution, related primarily to the frequent incidence of dark, firm, dry meat. Consumers are unlikely to buy and consume such meat. The aim of this study was to examine the effect of transport period and mixing of groups during rest period in lairage on the quality of beef carcasses. The study included 40 Simmental bulls aged from 18 to 20 months. Ultimate pH value and meat colour were measured 24 hours post mortem in m. longissimus dorsi and m. gracilis. Only 45% of carcasses were within the standard pHu range. Results of transport period did not show significant effect on beef quality. In contrast to transport period, mixing of groups during rest period in lairage had highly significant adverse effect on beef quality (p<0.001). The effect of mixing of bulls during the resting period of 18 hours, could however be regarded of being the main stress factor.Proizvođači junećega mesa proteklih godina imaju značajne probleme u plasmanu junetine, prvenstveno zbog učestalije pojave tamnog suhog i tvrdog mesa (DFD). Potrošači takvo meso nerado kupuju i konzumiraju. Cilj ovog istraživanja je utvrditi značajnost utjecaja dužine transporta i miješanja grupa bikova tijekom odmora u stočnom depou na kakvoću junećih trupova. Istraživanje je uključilo 40 simentalske junadi u dobi od 18 do 20 mjeseci. Mjerenje konačne pH vrijednosti i boje mesa vršena su 24 sata post mortem na m. longissimus dorsi i m. gracilis. Samo je 45% trupova imalo vrijednost kpH u poželjnom intervalu. Istraživanjem nije utvrđen značajan utjecaj dužine transporta na pokazatelje kakvoće junećih trupova. Miješanje grupa bikova tijekom odmora u stočnom depou ima značajan utjecaj na kakvoću junećih trupova (p<0.001). Utjecaj miješanja grupa bikova tijekom odmora u stočnom može se smatrati jednim od glavnih uzročnika stresa odgovornog za pojavu DFD junećega mesa

UTJECAJ DUŽINE TRANSPORTA I MIJEŠANJA GRUPA NA KAKVOĆU JUNEĆIH TRUPOVA SIMENTALSKIH BIKOVA

In the last few years, beef producers have had great problems with beef distribution, related primarily to the frequent incidence of dark, firm, dry meat. Consumers are unlikely to buy and consume such meat. The aim of this study was to examine the effect of transport period and mixing of groups during rest period in lairage on the quality of beef carcasses. The study included 40 Simmental bulls aged from 18 to 20 months. Ultimate pH value and meat colour were measured 24 hours post mortem in m. longissimus dorsi and m. gracilis. Only 45% of carcasses were within the standard pHu range. Results of transport period did not show significant effect on beef quality. In contrast to transport period, mixing of groups during rest period in lairage had highly significant adverse effect on beef quality (p<0.001). The effect of mixing of bulls during the resting period of 18 hours, could however be regarded of being the main stress factor.Proizvođači junećega mesa proteklih godina imaju značajne probleme u plasmanu junetine, prvenstveno zbog učestalije pojave tamnog suhog i tvrdog mesa (DFD). Potrošači takvo meso nerado kupuju i konzumiraju. Cilj ovog istraživanja je utvrditi značajnost utjecaja dužine transporta i miješanja grupa bikova tijekom odmora u stočnom depou na kakvoću junećih trupova. Istraživanje je uključilo 40 simentalske junadi u dobi od 18 do 20 mjeseci. Mjerenje konačne pH vrijednosti i boje mesa vršena su 24 sata post mortem na m. longissimus dorsi i m. gracilis. Samo je 45% trupova imalo vrijednost kpH u poželjnom intervalu. Istraživanjem nije utvrđen značajan utjecaj dužine transporta na pokazatelje kakvoće junećih trupova. Miješanje grupa bikova tijekom odmora u stočnom depou ima značajan utjecaj na kakvoću junećih trupova (p<0.001). Utjecaj miješanja grupa bikova tijekom odmora u stočnom može se smatrati jednim od glavnih uzročnika stresa odgovornog za pojavu DFD junećega mesa