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D Fornasiero

Publications and source records attributed to D Fornasiero.

10 recordsLinked to original sources
PubMed2006

Influence of very small bubbles on particle/bubble heterocoagulation.

Very small bubbles which partially coat the surface of particles influence whether or not heterocoagulation between a particle and a bubble occurs. The electrostatic and van der Waals forces of interaction between particles and bubbles were calculated as a function of electrolyte concentration, particle size, and the size and distributions of these very small bubbles present on the particle surface. The height of the surface force barrier was compared with the hydrodynamic pressing force under conditions of flotation. The presence of these very small bubbles has a profound effect on the interaction between particles and bubbles and, in particular, strongly decreases the critical particle radius for heterocoagulation.

Journal Article↗
PubMed2000

Particle-bubble collision models--a review

A critical review of the various models existing in the literature for the calculation of the collision efficiency between particles and single, rising gas bubbles is presented. Although all of these collision models predict that the collision efficiency increases with particle size, their dependence on the latter is different because of the various assumptions and hydrodynamic conditions used in each model. Collision efficiencies of quartz particles with single bubbles have been obtained from experimental flotation experiments under conditions where the attachment and stability efficiencies were at, or near, unity. These collision efficiencies were then used to test various collision models. Good agreement between the experimental and calculated collision efficiencies was only obtained with the Generalised Sutherland Equation. The differences in collision efficiencies obtained between the various models were mainly explained in terms of, firstly, the degree of mobility of the bubble surface and, secondly, a consideration of the inertial forces acting on the particles.

Journal Article↗
PubMed1999

Particle-Bubble Attachment in Mineral Flotation.

Attachment efficiencies of rough, angular, methylated quartz particles with nitrogen bubbles are derived from experimental capture efficiency data in conjunction with a collision model termed the Generalized Sutherland Equation (GSE). The methylated quartz particles ranged in size from 7.5 to 70 µm equivalent diameter and had advancing contact angles between 33 degrees and 74 degrees. They heterocoagulated with nitrogen bubbles between 0.77 and 1.52 mm in diameter in 0, 0.01, or 0.1 mol dm(-3) KCl. The attachment efficiencies decreased with increasing particle size and bubble size, but increased with particle contact angle and KCl electrolyte concentration. These attachment efficiency data were then used to test the Dobby-Finch attachment model for potential flow conditions. The latter model was modified so that the conditions of approach of the particle toward the bubble surface are the same as those defined previously in the GSE collision model (Dai et al., 1998, J. Colloid Interface Sci. 197, 275). Satisfactory agreement was obtained between the experimental attachment efficiencies obtained in this study and those calculated with the Dobby-Finch model. In the attachment efficiency calculations, the induction time (t(ind)) varied with particle size (d(p)) according to the well-known equation, t(ind) = Ad(B)(p). The parameter B, with a value of 0.6, was found to be independent of particle size, particle contact angle, bubble size, and KCl electrolyte concentration. Conversely, the value of the parameter A was dependent on the particle contact angle, especially for contact angles smaller than 50 degrees, and on the bubble size but to a lesser extent on the electrolyte concentration. The value of A decreased with an increase in particle contact angle and an increase in bubble size. The values of the induction time obtained in this study are in a reasonable agreement with experimental and calculated induction times reported in the literature. Copyright 1999 Academic Press.

Journal Article↗
PubMed1998

The Inertial Hydrodynamic Interaction of Particles and Rising Bubbles with Mobile Surfaces

The collection efficiency of single bubbles rising through a very dilute pulp of hydrophobized quartz particles has been determined. Measurements have been performed under conditions in which the bubble surface is mobile, as a function of electrolyte concentration, particle diameter (7 to 70 &mgr;m), bubble diameter (0.77 x 10(-3) to 1.52 x 10(-3) m), and particle advancing water contact angle. Situations in which the product of attachment and stability efficiency is at its maximum value have been identified, permitting a stringent, critical test of collision theory to be performed. A collision theory has been developed which accounts for the influence of positive and negative inertial forces in the case of bubbles with mobile surfaces. The approach considers only long-range hydrodynamic interactions under conditions where short-range interactions are strongly suppressed (i.e., high particle contact angle and high electrolyte concentrations) and attachment occurs at first collision. In this instance, good agreement between theory and experiment is achieved for particle diameters between 7 and 60 &mgr;m and Stokes numbers up to 0.27. The analytical equation developed is termed the generalized Sutherland equation (GSE). Copyright 1998 Academic Press. Copyright 1998Academic Press

Journal Article↗
PubMed1987

Paramagnetic complexes of manganese(II), iron(III), and gadolinium(III) as contrast agents for magnetic resonance imaging. The influence of stability constants on the biodistribution of radioactive aminopolycarboxylate complexes.

Paramagnetic complexes of manganese(II), iron(III), and gadolinium(III) with many ligands appear to undergo ligand substitution in vivo, producing biodistribution data similar to the hydrated metal ions. To identify ligands likely to be valuable in the preparation of paramagnetic contrast agents, a series of aminopolycarboxylate complexes with stability constants increasing in the order iminodiacetic acid (IDA) less than nitrilotriacetic acid (NTA) less than EDTA less than CDTA less than or equal to DTPA was prepared with 54Mn(II), 59Fe(III), and 153Gd(III) at both tracer and carrier levels. Biodistribution studies in mice suggested that complexes remained unchanged in vivo if their stability constants (K1) were approximately greater than 10(16) for Mn(II) and Gd(III) and greater than 10(22) for Fe(III) complexes at tracer levels. Metal complexes with added carrier appeared to be effectively more stable in vivo, possibly due to dissociation and saturation of metal-binding sites. To avoid the accumulation of metal ions in tissues, new paramagnetic contrast agents containing these metal ions will require stability constants equal to or greater than those identified here.

Animals↗
PubMed1986

The preparation of 99mTc-tertiarybutylisonitrile (99mTc-TBI) by a method suitable for routine clinical use.

The myocardial imaging agent technetium-99m-hexakis (tertiarybutylisonitrile) (99mTc-TBI) was prepared by the reaction of [99mTc]pertechnetate with TBI in 50% ethanol/0.9% saline at 100 degrees C, using stannous chloride as the reducing agent. A study of the reaction parameters enabled the yield to be optimized to better than 90%, although this was reduced to approximately 60% if a purification step was carried out. Chromatographic analysis on ITLC-SG medium showed the final product to be of high radiochemical purity. Biological studies comprising biodistribution in mice over a 2-h period, imaging studies in animals and sub-acute toxicity testing in mice indicated that 99mTc-TBI prepared as here described is a suitable agent for routine clinical use in humans.

Animals↗
PubMed1985

NMR compartmentalization of free water in the perfused rat heart.

Spin-lattice (T1) and spin-spin (T2) relaxation times have been measured on perfused rat hearts under two experimental conditions. T1 exhibits a monoexponential decay. On the other hand T2 has a decay with two components: a short one T2s and a long one T2l. These facts have been discussed according to cross-relaxation and a bicompartmentalization of tissue assuming a slow exchange model for spin-spin relaxation and a fast exchange model for spin-lattice relaxation. Increasing the osmotic pressure of the perfusion solution decreased the absolute density proton of the T2s compartment reflecting the loss of its water content. The paramagnetic ion manganese diminishes the values of T1 and those of the long component T2l without affecting its short component. Therefore the short component could be assigned to intracellular and the long component to extracellular free water. The extracellular T2 (459 ms) is approximatively 10-fold higher than the intracellular T2 (45 ms). With images of "pure T2" such a difference could be useful to enhance the contrast between organs and the surrounding liquid or between organs with different water compartmentalization.

Animals↗
PubMed1985

The binding of 9-aminoacridine to calf thymus DNA in aqueous solution. Electronic spectral studies.

Absorption, circular dichroism and steady-state fluorescence spectra were determined of 9-aminoacridine solutions in the presence of DNA at an ionic strength of 0.001 mol dm-3. Up to a dye/DNA phosphorus ratio of about 0.2 the results are fully consistent with the requirements and predictions of a binding model already shown to apply to the binding of other aminoacridines to DNA. The apparently anomalous spectroscopic behaviour of the 9-aminoacridine/DNA system compared with proflavine/DNA, for example, can be satisfactorily explained from a consideration of the magnitudes of exciton interactions between dyes bound to DNA.

Aminacrine↗
PubMed1984

Vibronic exciton interactions. Resolution and interpretation of the temperature-dependent circular dichroism and absorption spectra of ApA and of dApdA.

The circular dichroism and absorption spectra of the stacked and unstacked forms of ApA and dApdA were derived. The unstacked spectra are not identical with the corresponding free nucleoside spectrum. The stacked spectra can be satisfactorily described in terms of the vibronic degenerate exciton theory which suggests that the non-degenerate interactions have a less important influence on the observed circular dichroic spectra than hitherto assumed. From the experimental spectra the magnitudes of the exciton coupling were found to correspond to very fast transfer rates of energy between the adenine moieties. The absorption spectra of the stacked species are consistent with average angles of near 60 degrees and 20 degrees in ApA and dApdA, respectively, between the degenerate transition moments of the adenine moieties.

Adenosine Monophosphate↗