In the present work, attempt has been made to investigate the influence of Ti on the castability of Alkilled ultra low carbon (ULC) steel, and to establish the possible reasons for the inferior castability of the Tibearing ULC steel vis-à-vis Ti-free grades. The work also attempted to identify suitable counter-measures for prevention of inclusion deposition in the submerged entry nozzles (SEN) during continuous casting of Tibearing Al-killed ULC steels. Characteristics of inclusions in the submerged entry nozzle deposit and corresponding liquid steel and slag samples from RH degasser and tundish were investigated. The presence of small quantity of Ti-bearing alumina inclusion was identified to be responsible for the extensive melt freezing inside the SEN deposit and poor castability of Ti-bearing Al-killed ULC steels. The influence of all materials contacting liquid steel subsequent to the RH degassing, on the reoxidation behaviour and castability of liquid steel, was assessed from their chemical composition. The present investigation indicated that while reoxidation is bad for the castability of all Al-killed steels, it becomes worse in the case of Ti-bearing Al-killed steels, primarily due to the formation of Ti-bearing inclusions that promote large-scale melt freezing inside the nozzle deposits.
The nucleus accumbens (NAc) is an important forebrain area involved in sensitization, withdrawal effects, and self-administration of cocaine. However, little is known about cocaine-induced alterations in the neuronal excitability and whole cell neuroplasticity in this region that may affect behaviors. Our recent investigations have demonstrated that repeated cocaine administration decreases voltage-sensitive sodium and calcium currents (VSSCs and VSCCs, respectively) in freshly dissociated NAc neurons of rats. In this study, current-clamp recordings were performed in slice preparations to determine the effects of chronic cocaine on evoked Ca(2+) potentials and voltage-sensitive K(+) currents in NAc neurons. Repeated cocaine administration with 3-4 days of withdrawal caused significant alterations in Ca(2+) potentials, including suppression of Ca(2+)-mediated spikes, increase in the intracellular injected current intensity required for generation of Ca(2+) potentials (rheobase), reduced duration of Ca(2+) plateau potentials, and abolishment of secondary Ca(2+) potentials associated with the primary Ca(2+) plateau potential. Application of nickel (Ni(2+)), which blocks low-voltage activated T-type Ca(2+) channels, had no impact on evoked Ca(2+) plateau potentials in NAc neurons, indicating that these Ca(2+) potentials are high-voltage activated (HVA). In addition, repeated cocaine pretreatment also hyperpolarized the resting membrane potential, increased the amplitude of afterhyperpolarization in Ca(2+) spikes, and enhanced the outward rectification observed during membrane depolarization. These findings indicate that repeated cocaine administration not only suppressed HVA-Ca(2+) potentials but also significantly enhanced the activity of various K(+) channels in NAc neurons. They also demonstrate an integrative role of whole cell neuroplasticity during cocaine withdrawal, by which the subthreshold membrane excitability of NAc neurons is significantly decreased.
Most refining reactions in steelmaking involve oxidation of impurity element(s). The product(s) of oxidation either dissolve in the slag or escape as gaseous phase. The activities of oxygen in the metal (h O ), and that of ''FeO'' in slag (a FeO ), are major factors controlling these chemical reactions. The activities of oxygen and ''FeO'' are thermodynamically related, provided equilibrium distribution of oxygen between the slag and the metal is attained. This enables direct estimation of one parameter from the other. A thorough knowledge of the variation in activity of FeO, and factors affecting the same, is therefore of great importance in the process metallurgy of steelmaking. The present work experimentally measures the activity of FeO in steelmaking slags and attempts to develop a correlation for estimation of c(FeO) as a function of temperature and chemical composition of the slag.
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