title: Microstructural controls on the geomechanics of coarse grained soft rocks; Waitemata Group, Auckland

authors: de la Mare, Graham Norman

abstract: The geomechanical behaviour of a variety of soft rocks from the Waitemata Group, Auckland, is characterised, and the influence of microstructure in determining the geomechanics examined. Field geotechnical measurements of joint spacing and Schmidt Hammer rebound are related to geomechanical properties to determine controls on joint development and applicability of field index tests for soft materials. Samples studied are dominantly sandstones, with one conglomerate; all of which have a significant component of swelling clay minerals. Low bulk densities, high porosities and large void ratios are characteristic of the samples.

They vary from extremely weak, very low durability rocks to moderately: strong and durable materials. Extremely weak sandstones are highly deformable and undergo plastic deformation when loaded in compression. The stronger samples undergo strain softening and respond elastically to applied stresses prior to brittle failure. High softening factors indicate that compressive and tensile strengths are greatly reduced upon saturation.

All the study rocks have high proportions of sand and silt size material (≤ 95 %), and up to 10 % of < 2 μ m proportions; significant gravel size material only occurs in the conglomerate. Volcanic and detrital rock fragments are the dominant constituents in all samples, with abundant quartz, minor calcic plagioclase, and a variety of accessory minerals. The dominant clay is smectite with lesser amounts of illite, kaolinite, and mixed-layer clays.

Individual sand and silt grains are dominantly subrounded to subangular quartz, regular bricks of feldspar, and rods of rutile, and are often clay coated. Microaggregates and grains are combined into aggregates and assemblages, and in some cases macroassemblages, to form granular arrangements, which produce a network of interconnecting pores. The fabric of the rocks is characterised by discontinuous matrices. Fabric types range from skeletal to turbostratic, and arrangements range from tightly interlocking grains to loose granular structures. Clay micro aggregates are either flocculated or form welded FF honeycomb arrangements.

Strength and durability are not influenced by quantity, size, or type of clasts or minerals present; rather, it is the arrangement of individual components (and associated pore spaces) in the rock fabric which directly determines the geomechanical behaviour. Strong, durable samples have an abundance of clean grain to grain contacts, and few large clay aggregates. Clay microaggregates are arranged in welded FF arrangements, and pore space is restricted to micropores which resist water infiltration. Progressively weaker rocks are characterised by an increase in clay coated grains, clay aggregates, and clay connectors (which form weak links for stress transmission), and interconnecting pores at all levels in the fabric. In the weakest rock macroassemblages of clay coated grains, and open flocculated smectitic aggregates connected by point contacts, produce a network of macropores, allowing easy access of water which flocculates clays into weaker states by reducing bonding and cohesion.

Schmidt rebound values in the field do not provide a useful indication of either compressive or tensile strength of these rocks. The rebound values do, however, correlate well with laboratory determined dynamic elasticity values, suggesting that the instrument should be used in the field to predict rock elasticity and not strength.

Joint spacing within the rock units is related to elasticity with units capable of storing stress through plastic deformation having reasonably wide, uniformly spaced joints. Units which release stress through brittle fracture have closely spaced, and more complex joint systems.

text: Microstructural controls on the geomechanics of coarse grained soft rocks; Waitemata Group, Auckland The geomechanical behaviour of a variety of soft rocks from the Waitemata Group, Auckland, is characterised, and the influence of microstructure in determining the geomechanics examined. Field geotechnical measurements of joint spacing and Schmidt Hammer rebound are related to geomechanical properties to determine controls on joint development and applicability of field index tests for soft materials. Samples studied are dominantly sandstones, with one conglomerate; all of which have a significant component of swelling clay minerals. Low bulk densities, high porosities and large void ratios are characteristic of the samples.

They vary from extremely weak, very low durability rocks to moderately: strong and durable materials. Extremely weak sandstones are highly deformable and undergo plastic deformation when loaded in compression. The stronger samples undergo strain softening and respond elastically to applied stresses prior to brittle failure. High softening factors indicate that compressive and tensile strengths are greatly reduced upon saturation.

All the study rocks have high proportions of sand and silt size material (≤ 95 %), and up to 10 % of < 2 μ m proportions; significant gravel size material only occurs in the conglomerate. Volcanic and detrital rock fragments are the dominant constituents in all samples, with abundant quartz, minor calcic plagioclase, and a variety of accessory minerals. The dominant clay is smectite with lesser amounts of illite, kaolinite, and mixed-layer clays.

Individual sand and silt grains are dominantly subrounded to subangular quartz, regular bricks of feldspar, and rods of rutile, and are often clay coated. Microaggregates and grains are combined into aggregates and assemblages, and in some cases macroassemblages, to form granular arrangements, which produce a network of interconnecting pores. The fabric of the rocks is characterised by discontinuous matrices. Fabric types range from skeletal to turbostratic, and arrangements range from tightly interlocking grains to loose granular structures. Clay micro aggregates are either flocculated or form welded FF honeycomb arrangements.

Strength and durability are not influenced by quantity, size, or type of clasts or minerals present; rather, it is the arrangement of individual components (and associated pore spaces) in the rock fabric which directly determines the geomechanical behaviour. Strong, durable samples have an abundance of clean grain to grain contacts, and few large clay aggregates. Clay microaggregates are arranged in welded FF arrangements, and pore space is restricted to micropores which resist water infiltration. Progressively weaker rocks are characterised by an increase in clay coated grains, clay aggregates, and clay connectors (which form weak links for stress transmission), and interconnecting pores at all levels in the fabric. In the weakest rock macroassemblages of clay coated grains, and open flocculated smectitic aggregates connected by point contacts, produce a network of macropores, allowing easy access of water which flocculates clays into weaker states by reducing bonding and cohesion.

Schmidt rebound values in the field do not provide a useful indication of either compressive or tensile strength of these rocks. The rebound values do, however, correlate well with laboratory determined dynamic elasticity values, suggesting that the instrument should be used in the field to predict rock elasticity and not strength.

Joint spacing within the rock units is related to elasticity with units capable of storing stress through plastic deformation having reasonably wide, uniformly spaced joints. Units which release stress through brittle fracture have closely spaced, and more complex joint systems.

year: 1992

title: Identification of central circuitry components mediating anorexigenic properties of oxytocin

authors: Klockars, Oscar Andreas

abstract: Recent years have brought exciting discoveries showing that a neurohormone, oxytocin (OT), acts as an appetite suppressant. Importantly, OT decreases energy needs-driven consumption of high-calorie foods by promoting early satiation, and it terminates intake motivated by palatability related to sweet taste. OT’s anorexigenic effects on both aspects of ingestive behavior are mediated by the OT receptor (OTr) expressed broadly in the brain, however, our understanding of which specific sites relay anorexigenic actions of OT is limited. Thus far, only the nucleus accumbens and ventral tegmental area of the mesolimbic system, and the brainstem’s dorsal vagal complex, have been directly implicated in relaying OT-induced hypophagia. Thus, the overarching goal of this thesis was to examine which discrete components of circuitry expressing the OTr mediate OT’s anorexigenic effects on energy- versus reward-driven feeding. The research approaches included intracranial drug administration, analyses of region-specific expression of genes, neuronal activation mapping, and feeding behavior testing in rats.
The first set of studies explored whether extreme overeating induced by a powerful orexigen, butorphanol tartrate (BT), can be alleviated by pharmacologically stimulating the OT receptor in the forebrain versus the hindbrain (via lateral (LV) and fourth ventricular (4V) OT injections, respectively). I established effective doses of BT and LV / 4V OT. Then, I determined doses of LV and 4V OT that reduce hyperphagia produced by BT in sated and deprived rats. Finally, I assessed whether OT’s effects on BT-induced feeding can be suppressed by an OTr antagonist. 4 mg/kg BT increased intake in fed and in deprived rats, whereas LV and 4V OT at 1μg caused a decrease in deprived rats. BT-induced chow intake in hungry and sated animals was suppressed by a very low, 0.1-μg dose of 4V OT, whereas 1μg OT was effective LV. The effect of OT was attenuated by OTr antagonist. The data strongly suggest that while both the forebrain and hindbrain populations of the OTr promote hypophagia, the hindbrain component of the circuitry is particularly sensitive to appetite reducing properties of OT in animals motivated to eat by a potent orexigen, BT.
In the second set of studies, I examined whether either of the two populations of the hypothalamic OTr, in the medial preoptic area (MPOA) or the ventromedial hypothalamic nucleus (VMH), mediates OT-driven hypophagia in energy- and reward-related ingestive behaviors. I provide insights into mechanisms underlying OT-driven anorexia mediated by the hypothalamus by (a) defining whether OT MPOA or VMH administration affects feeding for energy versus palatability; (b) identifying feeding-related sites activated by VMH OT injection; (c) measuring VMH OTr mRNA changes in response to hunger and palatability; and (d) examining how VMH OT affects sweet solution intake in rats. MPOA had no effect on intake of energy-dense chow in deprived rats nor did it decrease intake of calorie-dilute palatable solutions. VMH OT decreased chow intake and the effect was reversed by the antagonist. OT did not affect intakes of saccharin and sucrose solutions. Fos immunoreactivity, a marker of neuronal activation, was elevated in the VMH and energy balance-related paraventricular and arcuate nuclei, but not reward areas. VMH OT receptor expression was higher in hungry than sated rats; saccharin intake had no effect. In sum, MPOA OTr is not involved in OT-driven hypophagia mediated by hypothalamic networks. VMH OT decreases intake driven by energy not by palatability.
Finally, I assessed whether the OTr present in the basolateral (BLA) and central amygdala (CNA), sites implicated in emotional/pleasure processing of food intake, is involved in appetite control by OT. I injected OT in the BLA or CNA and assessed intake of chow induced by energy deprivation and intake of sweet solutions in nondeprived rats. I examined whether these effects are reversible by OTr blockade. I determined the effect of energy deprivation and exposure to saccharin on BLA and CNA expression of OTr mRNA. BLA OT at 0.3 μg and CNA OT at 1 μg reduced chow intake after deprivation. Only BLA OT was effective at suppressing consumption of sucrose and saccharin. The anorexigenic effects of BLA and CNA OT were attenuated by an OTr antagonist. BLA OTr mRNA expression was affected by exposure to saccharin, whereas that of CNA OTr, by energy deprivation. The relationship between amygdalar OT and energy- vs palatability-driven intake depends on the discrete localization of the OTr in this complex structure.
Overall, these findings shed light on the specific elements of brain circuitry mediating anorexigenic properties of OT. Both the forebrain and hindbrain OTr populations are relevant to feeding control. OT’s inhibitory effects on feeding for energy are mediated by a broader network of sites that includes, aside from the previously reported nucleus accumbens and dorsal vagal complex, the VMH, BLA, and CNA. Only the BLA OT modifies eating for reward. Surprisingly, the OTr in the MPOA is not involved in feeding regulation.

text: Identification of central circuitry components mediating anorexigenic properties of oxytocin Recent years have brought exciting discoveries showing that a neurohormone, oxytocin (OT), acts as an appetite suppressant. Importantly, OT decreases energy needs-driven consumption of high-calorie foods by promoting early satiation, and it terminates intake motivated by palatability related to sweet taste. OT’s anorexigenic effects on both aspects of ingestive behavior are mediated by the OT receptor (OTr) expressed broadly in the brain, however, our understanding of which specific sites relay anorexigenic actions of OT is limited. Thus far, only the nucleus accumbens and ventral tegmental area of the mesolimbic system, and the brainstem’s dorsal vagal complex, have been directly implicated in relaying OT-induced hypophagia. Thus, the overarching goal of this thesis was to examine which discrete components of circuitry expressing the OTr mediate OT’s anorexigenic effects on energy- versus reward-driven feeding. The research approaches included intracranial drug administration, analyses of region-specific expression of genes, neuronal activation mapping, and feeding behavior testing in rats.
The first set of studies explored whether extreme overeating induced by a powerful orexigen, butorphanol tartrate (BT), can be alleviated by pharmacologically stimulating the OT receptor in the forebrain versus the hindbrain (via lateral (LV) and fourth ventricular (4V) OT injections, respectively). I established effective doses of BT and LV / 4V OT. Then, I determined doses of LV and 4V OT that reduce hyperphagia produced by BT in sated and deprived rats. Finally, I assessed whether OT’s effects on BT-induced feeding can be suppressed by an OTr antagonist. 4 mg/kg BT increased intake in fed and in deprived rats, whereas LV and 4V OT at 1μg caused a decrease in deprived rats. BT-induced chow intake in hungry and sated animals was suppressed by a very low, 0.1-μg dose of 4V OT, whereas 1μg OT was effective LV. The effect of OT was attenuated by OTr antagonist. The data strongly suggest that while both the forebrain and hindbrain populations of the OTr promote hypophagia, the hindbrain component of the circuitry is particularly sensitive to appetite reducing properties of OT in animals motivated to eat by a potent orexigen, BT.
In the second set of studies, I examined whether either of the two populations of the hypothalamic OTr, in the medial preoptic area (MPOA) or the ventromedial hypothalamic nucleus (VMH), mediates OT-driven hypophagia in energy- and reward-related ingestive behaviors. I provide insights into mechanisms underlying OT-driven anorexia mediated by the hypothalamus by (a) defining whether OT MPOA or VMH administration affects feeding for energy versus palatability; (b) identifying feeding-related sites activated by VMH OT injection; (c) measuring VMH OTr mRNA changes in response to hunger and palatability; and (d) examining how VMH OT affects sweet solution intake in rats. MPOA had no effect on intake of energy-dense chow in deprived rats nor did it decrease intake of calorie-dilute palatable solutions. VMH OT decreased chow intake and the effect was reversed by the antagonist. OT did not affect intakes of saccharin and sucrose solutions. Fos immunoreactivity, a marker of neuronal activation, was elevated in the VMH and energy balance-related paraventricular and arcuate nuclei, but not reward areas. VMH OT receptor expression was higher in hungry than sated rats; saccharin intake had no effect. In sum, MPOA OTr is not involved in OT-driven hypophagia mediated by hypothalamic networks. VMH OT decreases intake driven by energy not by palatability.
Finally, I assessed whether the OTr present in the basolateral (BLA) and central amygdala (CNA), sites implicated in emotional/pleasure processing of food intake, is involved in appetite control by OT. I injected OT in the BLA or CNA and assessed intake of chow induced by energy deprivation and intake of sweet solutions in nondeprived rats. I examined whether these effects are reversible by OTr blockade. I determined the effect of energy deprivation and exposure to saccharin on BLA and CNA expression of OTr mRNA. BLA OT at 0.3 μg and CNA OT at 1 μg reduced chow intake after deprivation. Only BLA OT was effective at suppressing consumption of sucrose and saccharin. The anorexigenic effects of BLA and CNA OT were attenuated by an OTr antagonist. BLA OTr mRNA expression was affected by exposure to saccharin, whereas that of CNA OTr, by energy deprivation. The relationship between amygdalar OT and energy- vs palatability-driven intake depends on the discrete localization of the OTr in this complex structure.
Overall, these findings shed light on the specific elements of brain circuitry mediating anorexigenic properties of OT. Both the forebrain and hindbrain OTr populations are relevant to feeding control. OT’s inhibitory effects on feeding for energy are mediated by a broader network of sites that includes, aside from the previously reported nucleus accumbens and dorsal vagal complex, the VMH, BLA, and CNA. Only the BLA OT modifies eating for reward. Surprisingly, the OTr in the MPOA is not involved in feeding regulation.

year: 2019

title: Taking quality work to a new brilliance: Tama Ma on tour [Review]

authors: Crawford, Terri Ripeka

subjects: Tama Ma

abstract: Choreographers: Taiaroa Royal and Taane Mete; Douglas Wright; Michael Parmenter  Okareka Dance Company at Telecom Playhouse Theatre, WEL Energy Trust Academy of Performing Arts, Hamilton
From 17 Jun 2009 to 20 Jun 2009 

Reviewed by Terri Ripeka Crawford, 22 Jun 2009.

text: Taking quality work to a new brilliance: Tama Ma on tour [Review] Choreographers: Taiaroa Royal and Taane Mete; Douglas Wright; Michael Parmenter  Okareka Dance Company at Telecom Playhouse Theatre, WEL Energy Trust Academy of Performing Arts, Hamilton
From 17 Jun 2009 to 20 Jun 2009 

Reviewed by Terri Ripeka Crawford, 22 Jun 2009.

year: 2009