Determining the age of adult wild dogs (Canis lupus dingo, C-l. domesticus and their hybrids). I. Pulp cavity: tooth width ratios

In order to determine the age of adult wild dogs, we compared two methods ( that of Thomson and Rose (TR method) and that of Knowlton and Whittemore (KW method)) of measuring and calculating pulp cavity : tooth width ratios on upper and lower canine teeth from 68 mixed-sex, known-age wild dogs of 9 months to 13 years of age reared at two localities. Although significant relationships ( P = 0.0001) were found between age and pulp cavity ratios by both methods, the TR ratio calculation and measurement showed heteroscedasity in error variance whereas the KW ratios had a more stable error variance and were normally distributed. The KW method also found significant differences between pulp cavity ratios between teeth of the upper and lower jaws ( P < 0.0001) and sex ( P = 0.01) but not geographic origin ( P = 0.1). Regressions and formulae for fitted curves are presented separately for male and female wild dogs. Males show greater variability in pulp cavity decrements with age than do females, suggesting a physiological difference between the sexes. We conclude that the KW method of using pulp cavity as a proportion of tooth width, measured 15 mm from the root tip and averaged over both upper canines, is the more accurate method of estimating the age of adult wild dogs.

Temperature changes in dental pulp associated with use of power grinding equipment on equine teeth

Objective To quantify the temperature changes in the dental pulp associated with equine dental procedures using power grinding equipment. Design A matrix experimental design with replication on the same sample was followed to allow the following independent variables to be assessed: horse age (young or old), tooth type (premolar or molar), powered grinding instrument (rotating disc or die grinder), grinding time (15 or 20 seconds) and the presence or absence of water coolant. Procedure Sound premolar and molar teeth from a 6-year-old horse and a 15-year-old horse, which had been removed postmortem, were sectioned parallel to the occlusal plane to allow placement of a miniature thermocouple at the level of the dental pulp. The maximum temperature increase, the time taken to reach this maximum and the cooling time were measured (n=10 in each study). The teeth were placed in a vice and the instrument used on the tooth as per clinical situation. Results Significant differences were recorded for horse age (P < 0.001), instrument type (P < 0.001), grinding time (P < 0.001) and presence or absence of coolant (P < 0.001). There was no significant difference for tooth type. Conclusion Thermal insult to the dental pulp from the use of power instruments poses a significant risk to the tooth. This risk can be reduced or eliminated by appropriate selection of treatment time and by the use of water irrigation as a coolant. The increased dentine thickness in older horses appears to mitigate against thermal injury from frictional heat.

Selective transport of attached particles across the pulp-froth interface

A technique for determining the recovery of attached particles across the froth phase in flotation that relies on measuring the rate at which bubble-particle aggregates enter the froth is used to investigate the selectivity of attached particles across the froth phase. Combining these measurements with those of other techniques for determining the froth recovery of attached particles provides an insight into the different sub-processes of particle rejection in the froth phase. The results of experiments conducted in a 3 m(3) Outokumpu tank cell show that the detachment of particles from aggregates in the froth phase occurs largely at the pulp-froth interface. In particular it is shown that the pulp-froth interface selectively detaches particles from aggregates according to their physical attributes. (C) 2005 Elsevier Ltd. All rights reserved.

Slurry flow in mills with TCPL - An efficient pulp lifter for ag/sag mills

The difficulties associated with slurry transportation in autogenous (ag) and semi-autogenous (sag) grinding mills have become more apparent in recent years with the increasing trend to build larger diameter mills for grinding high tonnages. This is particularly noticeable when ag/sag mills are run in closed circuit with classifiers such as fine screens/cyclones. Extensive test work carried out on slurry removal mechanism in grate discharge mills (ag/sag) has shown that the conventional pulp lifters (radial and curved) have inherent drawbacks. They allow short-circuiting of the slurry from pulp lifters into the grinding chamber leading to slurry pool formation. Slurry pool absorbs part of the impact thus inhibiting the grinding process. Twin Chamber Pulp Lifter (TCPL) - an efficient design of pulp lifter developed by the authors overcomes the inherent drawbacks of the conventional pulp lifters. Extensive testing in both laboratory and pilot scale mills has shown that the TCPL completely blocks the flow-back process, thus allowing the mill to operate close to their design flow capacity. The TCPL performance is also found to be independent of variations in charge volume and grate design, whereas they significantly affect the performance of conventional pulp lifters (radial and curved). (c) 2006 Elsevier B.V. All rights reserved.

Selective transport of attached particles across the pulp-froth interface

A technique for determining the recovery of attached particles across the froth phase in flotation that relies on measuring the rate at which bubble-particle aggregates enter the froth is used to investigate the selectivity of attached particles across the froth phase. Combining these measurements with those of other techniques for determining the froth recovery of attached particles provides an insight into the different subprocesses of particle rejection in the froth phase. The results of experiments conducted in a 3 m3 Outokumpu tank cell show that the detachment of particles from aggregates in the froth phase occurs largely at the pulp-froth interface. In particular it is shown that the pulp-froth interface selectively detaches particles from aggregates according to their physical attributes.

Life cycle assessment of advanced bioethanol production from pulp and paper sludge

This work evaluates the environmental performance of using pulp and paper sludge as feedstock for the production of second generation ethanol. An ethanol plant for converting 5400 tons of dry sludge/year was modelled and evaluated using a cradle-to-gate life cycle assessment approach. The sludge is a burden for pulp and paper mills that is mainly disposed in landfilling. The studied system allows for the valorisation of the waste, which due to its high polysaccharide content is a valuable feedstock for bioethanol production. Eleven impact categories were analysed and the results showed that enzymatic hydrolysis and neutralisation of the CaCO3 are the environmental hotspots of the system contributing up to 85% to the overall impacts. Two optimisation scenarios were evaluated: (1) using a reduced HCl amount in the neutralisation stage and (2) co-fermentation of xylose and glucose, for maximal ethanol yield. Both scenarios displayed significant environmental impact improvements.