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Andrew Mcintosh - One of the best experts on this subject based on the ideXlab platform.
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functional implications of craniomandibular morphology in african mole rats rodentia bathyergidae
Biological Journal of The Linnean Society, 2016Co-Authors: Andrew McintoshAbstract:African mole-rats are subterranean rodents from the family Bathyergidae. The family consists of six genera, five of which (Cryptomys, Fukomys, Georychus, Heliophobius and Heterocephalus) are chisel-tooth diggers, meaning they dig underground using procumbent incisors. The remaining genus of mole-rat (Bathyergus) is a scratch digger, which digs using its forelimbs. Chisel-tooth digging is thought to have evolved to enable exploitation of harder soils. It was hypothesized that to dig successfully using incisors, chisel-tooth digging mole-rats will have a craniomandibular complex that is better able to achieve a large bite force and wide gape compared with scratch digging mole-rats. Linear measurements of morphological characteristics associated with bite force and gape were measured in several chisel-tooth digging and scratch digging mole-rats. Chisel-tooth diggers have increased jaw and condyle lengths relative to their size (characteristics associated with larger gape). They also have relatively wider and taller skulls (characteristics associated with larger bite force). The mechanical advantage of three masticatory muscles of each specimen was also calculated. The mechanical advantage of the temporalis muscle was significantly larger in chisel-tooth digging mole-rats than scratch digging genus. The results demonstrate that chisel-tooth digging bathyergids have a craniomandibular morphology that is better able to facilitate high bite force and wide gape than scratch digging mole-rats.
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Functional implications of craniomandibular morphology in African mole‐rats (Rodentia: Bathyergidae)
Biological Journal of The Linnean Society, 2015Co-Authors: Andrew McintoshAbstract:African mole-rats are subterranean rodents from the family Bathyergidae. The family consists of six genera, five of which (Cryptomys, Fukomys, Georychus, Heliophobius and Heterocephalus) are chisel-tooth diggers, meaning they dig underground using procumbent incisors. The remaining genus of mole-rat (Bathyergus) is a scratch digger, which digs using its forelimbs. Chisel-tooth digging is thought to have evolved to enable exploitation of harder soils. It was hypothesized that to dig successfully using incisors, chisel-tooth digging mole-rats will have a craniomandibular complex that is better able to achieve a large bite force and wide gape compared with scratch digging mole-rats. Linear measurements of morphological characteristics associated with bite force and gape were measured in several chisel-tooth digging and scratch digging mole-rats. Chisel-tooth diggers have increased jaw and condyle lengths relative to their size (characteristics associated with larger gape). They also have relatively wider and taller skulls (characteristics associated with larger bite force). The mechanical advantage of three masticatory muscles of each specimen was also calculated. The mechanical advantage of the temporalis muscle was significantly larger in chisel-tooth digging mole-rats than scratch digging genus. The results demonstrate that chisel-tooth digging bathyergids have a craniomandibular morphology that is better able to facilitate high bite force and wide gape than scratch digging mole-rats.
Francisco Bozinovic - One of the best experts on this subject based on the ideXlab platform.
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energetics and burrowing behaviour in the semifossorial degu octodon degus rodentia octodontidae
Journal of Zoology, 2000Co-Authors: Luis A Ebensperger, Francisco BozinovicAbstract:The energetics and burrowing behaviour of the semifossorial Octodon degus (Rodentia: Octodontidae) were investigated and compared with that of more specialized fossorial rodents. An open-flow respirometry system was used to record energy expenditure of single degus inside respirometers partially filled with soft (moist) or hard (dry) soil. In addition, digging behaviour was recorded in groups of three animals inside a large terrarium under controlled conditions of food, photoperiod and temperature. In the field, the digging activity of degus was monitored, along with seasonal variations in rainfall, content of soil moisture and soil hardness. Mass-specific metabolic rate during digging was found to be higher in animals burrowing in soft soils compared to hard soil. However, animals burrowing in soft soil removed more soil per min than animals in hard soil. Thus, gram per gram, excavating in hard soil was energetically more expensive. The digging cost of semifossorial degus tends to be either similar to or above those of similarly sized, but more fossorial, rodents. In the field, heightened digging activity coincided with the occurrence of rainfall, greater content of soil moisture and relatively soft soil conditions. Degus generally use their front feet and teeth to shear the soil; disposal of accumulated debris being carried out by moving their front and hind feet backwards. We also observed the establishment of digging chains when two or three individuals burrowed at the same site. As far as digging is concerned, the behaviour of degus is similar to that of other fossorial rodents, such as African bathyergids and the more closely related South American ctenomyids.
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Communal burrowing in the hystricognath rodent, Octodon degus: a benefit of sociality?
Behavioral Ecology and Sociobiology, 2000Co-Authors: Luis A Ebensperger, Francisco BozinovicAbstract:We examined the hypothesis that a main benefit of group-living in the semifossorial rodent, Octodon degus (Rodentia: Octodontidae), is to decrease individual cost of burrow construction. We contrasted the digging behavior of groups of three same-sex, adult-sized individuals with that of solitary degus. The behavior of singles and trios was recorded inside a large terrarium partially filled with natural soil and under controlled conditions of food, light, and temperature. The observation that degus in groups do not decrease their burrowing time or frequency of digging compared with solitary diggers does not support the hypothesis that communal burrowing is a primary cause of degu sociality. On the other hand, the observation that degus in groups removed significantly more soil per capita than solitary digging degus, and that grouped individuals coordinated their digging – group members burrowed mostly in the same sites and formed digging chains –, suggests that social burrowing may potentially reduce the cost of burrow construction in the long term. We suggest that such long-term benefits will be a consequence rather than a cause of degu group-living.
G.j. Lyman - One of the best experts on this subject based on the ideXlab platform.
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The effect of Jigging time and air cycle on bed stratification in a pilot scale Baum jig
Fuel, 2003Co-Authors: R.x. Rong, G.j. LymanAbstract:A highly instrumented and controlled pilot jig was constructed to study water motion behaviour or oscillation with the object of optimizing bed stratification of coal washing jigs. Durable synthetic material, colour coded for density, was used as the bed material in a series of 114 experiments. The bed was fully analysed layer by layer for size and density distribution. It was found that Jigging time is a very significant parameter affecting the bed stratification. In general, bed stratification improves quickly up to a Jigging time of 180 s, and thereafter more slowly. When the Jigging time exceeds 300 s, the bed is in a state of dynamic equilibrium for material coarser than 8 mm; however, the finer particles (< 8mm) need more time to achieve such a state. To improve the bed stratification, operating parameters should be adjusted to generate suitable air and water behaviour in the jig. A cycle with a long inlet period (199-220 °), which is seldom used at present, appears to provide such behaviour. Improvement of bed stratification by using an appropriate air cycle will increase the separation efficiency and yield of product in coal washing jigs.
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Modelling jig bed stratification in a pilot scale Baum jig
Minerals Engineering, 2003Co-Authors: R.x. Rong, G.j. LymanAbstract:Abstract A modelling investigation of jig bed stratification has been conducted using a large data base developed in a pilot scale Baum jig. The influence of the jig operating parameters and water behaviour parameters in the Jigging chamber on the bed stratification were analyzed. It was found that 1. i. Bed stratification is most sensitive to the Jigging time, followed by the frequency of pulsation, air supply pressure and inlet period of the air cycle. 2. ii. A single power function equation was used to effectively represent the relationship between the extent of bed stratification and the Jigging time. 3. iii. The jig bed stratification is significantly affected by a number of water behaviour parameters in the Jigging chamber. The water pressure above the bed plate has a dominant effect, followed by the water displacement. The velocity and acceleration of the water have insignificant effects on the bed stratification. 4. iv. A model has been developed to describe the extent of bed stratification as a function of the water pressure above the bed plate and the water amplitude in the Jigging chamber. Such a type of model may be a basis for oscillation control of the jigs.
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Review of Jigging Principles and Control
Coal Preparation, 1992Co-Authors: G.j. LymanAbstract:The jig in its variety of forms applied in coal preparation has been a major unit in coal washeries for one hundred years; yet the principles of Jigging are still less well understood than those governing many other coal preparation unit operations. Jig control has also been viewed as an art rather than a science until recently. This review considers some of the history of jigs and the theories that have been advanced to explain their operation. Special emphasis is placed on discussion of the means of control of jigs, starting from the traditional means and working towards the novel methods that have been proposed recently. It is clear that our understanding of jigs and the means by which they will be controlled in the future will benefit from our rapidly increasing engineering computational power and will make much fuller use of microprocessor control and modern instrumentation.
Luis A Ebensperger - One of the best experts on this subject based on the ideXlab platform.
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energetics and burrowing behaviour in the semifossorial degu octodon degus rodentia octodontidae
Journal of Zoology, 2000Co-Authors: Luis A Ebensperger, Francisco BozinovicAbstract:The energetics and burrowing behaviour of the semifossorial Octodon degus (Rodentia: Octodontidae) were investigated and compared with that of more specialized fossorial rodents. An open-flow respirometry system was used to record energy expenditure of single degus inside respirometers partially filled with soft (moist) or hard (dry) soil. In addition, digging behaviour was recorded in groups of three animals inside a large terrarium under controlled conditions of food, photoperiod and temperature. In the field, the digging activity of degus was monitored, along with seasonal variations in rainfall, content of soil moisture and soil hardness. Mass-specific metabolic rate during digging was found to be higher in animals burrowing in soft soils compared to hard soil. However, animals burrowing in soft soil removed more soil per min than animals in hard soil. Thus, gram per gram, excavating in hard soil was energetically more expensive. The digging cost of semifossorial degus tends to be either similar to or above those of similarly sized, but more fossorial, rodents. In the field, heightened digging activity coincided with the occurrence of rainfall, greater content of soil moisture and relatively soft soil conditions. Degus generally use their front feet and teeth to shear the soil; disposal of accumulated debris being carried out by moving their front and hind feet backwards. We also observed the establishment of digging chains when two or three individuals burrowed at the same site. As far as digging is concerned, the behaviour of degus is similar to that of other fossorial rodents, such as African bathyergids and the more closely related South American ctenomyids.
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Communal burrowing in the hystricognath rodent, Octodon degus: a benefit of sociality?
Behavioral Ecology and Sociobiology, 2000Co-Authors: Luis A Ebensperger, Francisco BozinovicAbstract:We examined the hypothesis that a main benefit of group-living in the semifossorial rodent, Octodon degus (Rodentia: Octodontidae), is to decrease individual cost of burrow construction. We contrasted the digging behavior of groups of three same-sex, adult-sized individuals with that of solitary degus. The behavior of singles and trios was recorded inside a large terrarium partially filled with natural soil and under controlled conditions of food, light, and temperature. The observation that degus in groups do not decrease their burrowing time or frequency of digging compared with solitary diggers does not support the hypothesis that communal burrowing is a primary cause of degu sociality. On the other hand, the observation that degus in groups removed significantly more soil per capita than solitary digging degus, and that grouped individuals coordinated their digging – group members burrowed mostly in the same sites and formed digging chains –, suggests that social burrowing may potentially reduce the cost of burrow construction in the long term. We suggest that such long-term benefits will be a consequence rather than a cause of degu group-living.
Carlos Hoffmann Sampaio - One of the best experts on this subject based on the ideXlab platform.
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Some observations on the influence of particle size and size distribution on stratification in pneumatic jigs
Powder Technology, 2019Co-Authors: Weslei M. Ambros, Carlos Hoffmann Sampaio, Bogdan Cazacliu, Paulo N. ConceiÇÃo, Glaydson S. Dos ReisaAbstract:Particle size variation plays a key role in Jigging performance, and despite extensive research in the area, very little attention has been given in the case of pneumatic Jigging. The aim of this study was to look into particle stratification in a pilot-scale pneumatic jig when varying the particle size and the range of the particle size distribution in ternary mixtures of aggregates. Jigging tests were especially designed to reduce contamination of jig products and a stratification index was elaborated to evaluate stratification efficiency. Experimental results provided compelling evidences that widening the particle size distribution of the system or using beds composed of particles of smaller sizes can enhance stratification by density. Similarly, smaller particles showed a remarkable tendency to concentrate in the upper zones of the stratified bed, whereas larger particles tended to concentrate more in lower zones. The obtained results suggest that particular operating features of pneumatic Jigging together with differential packing effects should play a decisive role in the stratification extent of beds formed by particles of different sizes. Experimental results are of practical importance since, among other benefits, they point to the possibility to increase pneumatic Jigging performance in some cases by using wider size distributions of the feed, thus reducing the need of prior stages of narrow size classification.
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Usage of air Jigging for multi-component separation of construction and demolition waste
Waste Management, 2017Co-Authors: Weslei Monteiro Ambrós, Carlos Hoffmann Sampaio, Bogdan Cazacliu, Gerson Miltzarek, Leonardo R. MirandaAbstract:The use of air Jigging for performing multi-component separation in the treatment of mixed construction and demolition waste was studied. Sorting tests were carried out with mixtures of equal bulk volume of concrete and brick in which fixed quantities of unwanted materials - gypsum, wood and paper - were added. Experimental results have demonstrated the possibility to use air Jigging to carry out both the removal of low-density contaminants and the concrete concentration in only one process step. In relation to the removal of contaminants only, the overall performance of Jigging process can be comparable with that of commercial air classifiers and automatic sorting systems. Also, the initial content of contaminants seems does not have a significant effect on the separation extent. These results are of particular importance for recycling plants processing as they represent an alternative to optimize the use of air jigs. Further investigation is needed in order to evaluate the practical feasibility of such method.
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Wall effects on particle separation in air jigs
Powder Technology, 2016Co-Authors: Weslei Monteiro Ambrós, Bogdan Cazacliu, Carlos Hoffmann SampaioAbstract:This study investigates the influence of wall effects on particle separation in an air Jigging device. Tests were conducted with a ternary mixture of concrete, brick and gypsum particles in the size range from 12 to 20 mm for three different Jigging times. It is shown that an unusual, remarkable segregation occurred in the direction perpendicular to the lateral walls, giving rise to a horizontal segregation pattern. In all cases, heavier particles concentrated more in the center of the particle bed while lighter particles concentrated along the side walls. Composition measurements of the stratified bed revealed that wall effects can significantly influence the composition of jig products. Linear predictions of Jigging evolution suggest that stratification progress linearly after the first initial stages. Also, time evolution and analysis of local compacities indicate that stratification starts from the bottom to the upper layers of particle bed. Based on the experimental results, a mechanism for the pattern formation was proposed, which was enhanced by a geometry model of bed rearrangement. Prediction results for bed composition correlated well with experimental data and endorsed the role of lateral walls on the segregation pattern formed. The results obtained also show practical significance for the use of air Jigging in the sorting of recycled aggregates.