Adsorption mechanism of diethyldithio carbamate on covellite, cuprite and tenorite

Adsorption of diethyldithiocarbamate (DTC) on covellite, cuprite and tenorite was investigated under different experimental conditions. The qualitative nature of surface species formed at the interface was examined by selective solvent extraction and UVvisible spectrophotometric techniques. The presence of surface species such ::lB [Cu(DTC)]+, Cu(DTC)2and Cu(I) DTC at different concentrations of the reagent and pH of the suspension was investigated. The results of this study indicate a surface reactionbetween DTC ligand molecules and surface copper sites. As a result of interaction with DTC, cations on the mineral surface are dislodged from the lattice and precipitated on the surface as copper dithiocarbamate complexes. Depending on the concentration of DTC, two types of copper complexes, i.e. [Cu(DTC)]+at low concentration and Cu(DTCh at higher concentration, are noted on copper(II) substrates, whereas on cuprite Cu(I) DTC was formed along with [Cu(DTC)]+ and Cu(DTCh. From the kinetic study, the overall adsorption was found to be mainly controlled by diffusion processes

Adsorption of thiol collectors on Chalcopyrite

Adsorption of diethyldithiocarbamate and ethylxanthate on chalcopyrite mineral surface was studied by static bed adsorption method. The qualitative nature of surface species was examined by selective solvent extraction and UV-visible spectroscopic technique.The results clearly indicate that the interaction between surface metal ions and thiols is chemical in nature. As a result of chemical interaction of ligand molecules, metal ions from mineral surface are dislodged from the lattice and precipitates of metal-ligand complexes were formed on the surface. Surface complexes were found to be identical to that of bulk complexes with metal-to-ligand ratio of 1:2

Electrokinetic studies on covellite, cuprite and tenorite

Detailed electrokinetic measurements are conduct.ed on synthetic covellite, cuprite and tenorite particles. The role of potential determining ions identical to that of the particle lattice is considered in addition to usual H+ and hydroxide ions. In the case of CuS, additional charge reversals are noticed between pH ~ 2.5 and < 6.0 in addition to the usual charge reversals that occur by direct hydrolysis in the socalled region of metal ion precipitation. Interaction of protons with hydrous mineral surface and the adsorption of desorbed or exces metal ions with protonated surface sites are explained by ion exchange mechanism. Effect of reducing environment and oxidation-reduction reactions o

Shear flocculation of quartz.

The present study deals with the shear flocculation of quartz in aqueous solutions of dodecylamine. Zetapotential data was correlated with flocculation behavior.It was observed that the particle hydrophobicity and pH were most important since dodecylamine chloride reactions are Ph and concentration dependent

Utilisation of Mineral Slimes and Industrial Waste by Electro Flotation and Selective Flocculation.

Electroflotation and selective flocculation or the combination of both appear to be potential techniques for the beneficiation of low grade mineral slimes and fines generated during mining, milling and other metallurgical operations. Considering the hydrodynamics of flotation process, electroflotation was proved to be an effective and viable technique to separate organic suspending particulate matter generated from leather, textile, metallurgical, oil refinery and food processing plants. Electroflotation is advantageous to process sulphide minerals and minerals that undergo surface changes when exposed to electrolytic oxygen and hydrogen. Adsorption of oxygen, liberated from the anode leads to the formation of elemental sulphur on the surface of the particles. Elemental sulphur thus formed under controlled oxidation enhances the hydrophobicity. Continuous liberation of H+ and OH- leads to drastic changes in the pH of the pulp. Hence, electroflotation technique is more disadvantageous where pH is a critical parameter. Also part of the collector will be either destroyed or dissociated under the influence of pH, electrolytic bubbles and oxidation-reduction environment changes. Selective flocculation of minerals using polymers followed by anyone of the separation techniques such as, flotation, elutriation, filtration, etc. offers considerable promise for processing non-precious oxide minerals. Natural and synthetic high molecular weight polymers have been successfully used as flocculants. Lack of desired specificity is the major set back in this process. However, specificity can be introduced by incorporating active groups in the polymers. Though there is enough literature on selective flocculation of synthetic mineral mixtures, reports on the flocculation of multi-component natural ores are scant. Further, it is generally observed that the prediction of selective flocculation on the basis of results obtained from single mineral tests fairly agrees with synthetic mineral mixtures but rarely on natural systems

A review of the renal system and diurnal variations of renal activity in livestock

Kidneys are the main organs regulating water-electrolyte homeostasis in the body. They are responsible for maintaining the total volume of water and its distribution in particular water spaces, for electrolyte composition of systemic fluids and also for maintaining acid-base balance. These functions are performed by the plasma filtration process in renal glomeruli and the processes of active absorption and secretion in renal tubules, all adjusted to an 'activity-rest' rhythm. These diurnal changes are influenced by a 24-hour cycle of activity of hormones engaged in the regulation of renal activity. Studies on spontaneous rhythms of renal activity have been carried out mainly on humans and laboratory animals, but few studies have been carried out on livestock animals. Moreover, those results cover only some aspects of renal physiology. This review gives an overview of current knowledge concerning renal function and diurnal variations of some renal activity parameters in livestock, providing greater understanding of general chronobiological processes in mammals. Detailed knowledge of these rhythms is useful for clinical, practical and pharmacological purposes, as well as studies on their physical performance

Oxytocin and cholecystokinin secretion in women with colectomy

BACKGROUND: Cholecystokinin (CCK) concentrations in plasma have been shown to be significantly higher in colectomised subjects compared to healthy controls. This has been ascribed to reduced inhibition of CCK release from colon. In an earlier study CCK in all but one woman who was colectomised, induced release of oxytocin, a peptide present throughout the gastrointestinal (GI) tract. The aim of this study was thus to examine if colectomised women had a different oxytocin response to CCK compared to healthy controls. METHODS: Eleven women, mean age 34.4 ± 2.3 years, who had undergone colectomy because of ulcerative colitis or constipation were studied. Eleven age-matched healthy women served as controls. All subjects were fasted overnight and given 0.2 μg/kg body weight of CCK-8 i.v. in the morning. Samples were taken ten minutes and immediately before the injection, and 10, 20, 30, 45, 60, 90 and 120 min afterwards. Plasma was collected for measurement of CCK and oxytocin concentrations. RESULTS: The basal oxytocin and CCK concentrations in plasma were similar in the two groups. Intravenous injection of CCK increased the release of oxytocin from 1.31 ± 0.12 and 1.64 ± 0.19 pmol/l to 2.82 ± 0.35 and 3.26 ± 0.50 pmol/l in controls and colectomised women, respectively (p < 0.001). Given the short half-life of CCK-8 in plasma, the increased concentration following injection could not be demonstrated in the controls. On the other hand, in colectomised women, an increase of CCK in plasma was observed for up to 20 minutes after the injection, concentrations increasing from 1.00 ± 0.21 to a maximum of 1.81 ± 0.26 pmol/l (p < 0.002). CONCLUSION: CCK stimulates the release of oxytocin in women. There is no difference in plasma concentrations between colectomised and controls. However, colectomy seems to reduce the metabolic clearance of CCK. The hyperCCKemia in patients who had undergone colectomy is consequently not only dependent on CCK release, but may also depend on reduced clearance

The differential hormonal milieu of morning versus evening, may have an impact on muscle hypertrophic potential

Substantial gains in muscle strength and hypertrophy are clearly associated with the routine performance of resistance training. What is less evident is the optimal timing of the resistance training stimulus to elicit these significant functional and structural skeletal muscle changes. Therefore, this investigation determined the impact of a single bout of resistance training performed either in the morning or evening upon acute anabolic signalling (insulin-like growth factor-binding protein-3 (IGFBP-3), myogenic index and differentiation) and catabolic processes (cortisol). Twenty-four male participants (age 21.4±1.9yrs, mass 83.7±13.7kg) with no sustained resistance training experience were allocated to a resistance exercise group (REP). Sixteen of the 24 participants were randomly selected to perform an additional non-exercising control group (CP) protocol. REP performed two bouts of resistance exercise (80% 1RM) in the morning (AM: 0800 hrs) and evening (PM: 1800 hrs), with the sessions separated by a minimum of 72 hours. Venous blood was collected immediately prior to, and 5 min after, each resistance exercise and control sessions. Serum cortisol and IGFBP-3 levels, myogenic index, myotube width, were determined at each sampling period. All data are reported as mean ± SEM, statistical significance was set at P≤0.05. As expected a significant reduction in evening cortisol concentration was observed at pre (AM: 98.4±10.5, PM: 49.8±4.4 ng/ml, P0.05). Timing of resistance training regimen in the evening appears to augment some markers of hypertrophic potential, with elevated IGFBP-3, suppressed cortisol and a superior cellular environment. Further investigation, to further elucidate the time course of peak anabolic signalling in morning vs evening training conditions, are timely

3,4-Methylenedioxymethamphetamine (MDMA) neurotoxicity in rats: a reappraisal of past and present findings

RATIONALE: 3,4-Methylenedioxymethamphetamine (MDMA) is a widely abused illicit drug. In animals, high-dose administration of MDMA produces deficits in serotonin (5-HT) neurons (e.g., depletion of forebrain 5-HT) that have been interpreted as neurotoxicity. Whether such 5-HT deficits reflect neuronal damage is a matter of ongoing debate. OBJECTIVE: The present paper reviews four specific issues related to the hypothesis of MDMA neurotoxicity in rats: (1) the effects of MDMA on monoamine neurons, (2) the use of “interspecies scaling” to adjust MDMA doses across species, (3) the effects of MDMA on established markers of neuronal damage, and (4) functional impairments associated with MDMA-induced 5-HT depletions. RESULTS: MDMA is a substrate for monoamine transporters, and stimulated release of 5-HT, NE, and DA mediates effects of the drug. MDMA produces neurochemical, endocrine, and behavioral actions in rats and humans at equivalent doses (e.g., 1–2 mg/kg), suggesting that there is no reason to adjust doses between these species. Typical doses of MDMA causing long-term 5-HT depletions in rats (e.g., 10–20 mg/kg) do not reliably increase markers of neurotoxic damage such as cell death, silver staining, or reactive gliosis. MDMA-induced 5-HT depletions are accompanied by a number of functional consequences including reductions in evoked 5-HT release and changes in hormone secretion. Perhaps more importantly, administration of MDMA to rats induces persistent anxiety-like behaviors in the absence of measurable 5-HT deficits. CONCLUSIONS: MDMA-induced 5-HT depletions are not necessarily synonymous with neurotoxic damage. However, doses of MDMA which do not cause long-term 5-HT depletions can have protracted effects on behavior, suggesting even moderate doses of the drug may pose risks