title: Prediction of the mechanical properties of isotropic pure metal-based and two-phase alloy-based porous materials using modified analytical models

authors: Bolzoni, Leandro

abstract: This work investigates the applicability and accuracy of the five fundamental analytical models commonly used to estimate the thermophysical properties of porous materials for the prediction of the mechanical behaviour, both compressive and tensile, of isotropic pure metal-based and two-phase alloy-based porous materials. In literature, the prediction of the mechanical behaviour of these advanced engineering materials requires the development of semi-empirical models, which are material-specific and, thus, require empirical constants. The significance of the current investigation is the possibility to optimise the mechanical behaviour of porous metallic materials through the rapid and accurate prediction of their mechano-physical behaviour using non-empirical physically-based prediction models. The work is complemented with the derivation of new combined models with increased accuracy prediction of up to approx. 90% with respect to fundamental models. Although developed for porous materials, the derived combined models could be applied for the accurate and rapid prediction of the thermophysical and mechanical properties of multi-phase materials with unknown microstructure such as two-ductile-phase alloys, nanocomposites, hetero- and harmonic-structured materials, and immiscible alloys.

text: Prediction of the mechanical properties of isotropic pure metal-based and two-phase alloy-based porous materials using modified analytical models This work investigates the applicability and accuracy of the five fundamental analytical models commonly used to estimate the thermophysical properties of porous materials for the prediction of the mechanical behaviour, both compressive and tensile, of isotropic pure metal-based and two-phase alloy-based porous materials. In literature, the prediction of the mechanical behaviour of these advanced engineering materials requires the development of semi-empirical models, which are material-specific and, thus, require empirical constants. The significance of the current investigation is the possibility to optimise the mechanical behaviour of porous metallic materials through the rapid and accurate prediction of their mechano-physical behaviour using non-empirical physically-based prediction models. The work is complemented with the derivation of new combined models with increased accuracy prediction of up to approx. 90% with respect to fundamental models. Although developed for porous materials, the derived combined models could be applied for the accurate and rapid prediction of the thermophysical and mechanical properties of multi-phase materials with unknown microstructure such as two-ductile-phase alloys, nanocomposites, hetero- and harmonic-structured materials, and immiscible alloys.

year: 2021

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: Mana Motuhake Ringa: The non-invasive neural interface based artificial hand

authors: Owen, Mahonri W.

subjects: Prosthetics

abstract: Ten million people on the earth at any given time suffer from the loss or lack of a limb. Three million of these are upper extremity amputees. No matter the cause or reason for amputation the amputees’ life is never the same again. Independence can be lost and never regained. The loss of a limb can be an overpowering event that effects the mental, social, and physical well-being of a person. Although there has been many attempts to restore hand function through neural prosthetics there is little to no credible solutions to regain it. This thesis presents methods to restore hand function based on the human grasping system and addresses key challenges in the practical application of those methods. The contribution of this work lies in improving artificial hand function by mimicking the human grasping system. The human grasping system consists of the brain, the nervous system and the hand. The methods used investigate: biomechanical design principles for artificial hands, the limitations of machine learning in non-invasive neural interfaces (NI’s) and the development of an autonomous hand control framework for artificial hand control. 

The application of the Support Vector Machine (SVM) to a non-invasive neural interface is principally limited to binary applications in the real world. In order to overcome this limitation an autonomous approach is developed to achieve better response and accuracy from NI control frameworks. In binary applications the SVM performed well with a classification accuracy of around 80% accompanied by a response time of just under 5 seconds. When applied to multiple classifications the SVM decreased in accuracy and response dramatically. The accuracy of the autonomous hand control framework had a classification accuracy of 95% with a response time comparable to that of the SVM. This outcome has the potential to move non-invasive NI research into the real world and to restore hand function in an intuitive and meaningful way. A key learning of this research is that machine learning methods for non-invasive neural interfaces are not the best way to restore hand function for amputees. Hand function is best restored through the combining of machine learning and machine vision into a single NI based control framework. Additionally, this work is based in Mātauranga Māori with a western science approach. By so doing, amputees will be empowered, have increased independence and enjoy a better quality of life.

The scope of this work is limited to the consideration of hand function restoration for upper extremity amputees. In particular trans-radial amputees. Focus is given to non-invasive methods of control, therefore, investigations are limited to the electroencephalography (EEG) signal. Mimicking the human grasping system is a complex and difficult process, therefore, the attempts in this work to restore hand function only consider mechanisms and processes related directly to the motor control of the human hand.

text: Mana Motuhake Ringa: The non-invasive neural interface based artificial hand Ten million people on the earth at any given time suffer from the loss or lack of a limb. Three million of these are upper extremity amputees. No matter the cause or reason for amputation the amputees’ life is never the same again. Independence can be lost and never regained. The loss of a limb can be an overpowering event that effects the mental, social, and physical well-being of a person. Although there has been many attempts to restore hand function through neural prosthetics there is little to no credible solutions to regain it. This thesis presents methods to restore hand function based on the human grasping system and addresses key challenges in the practical application of those methods. The contribution of this work lies in improving artificial hand function by mimicking the human grasping system. The human grasping system consists of the brain, the nervous system and the hand. The methods used investigate: biomechanical design principles for artificial hands, the limitations of machine learning in non-invasive neural interfaces (NI’s) and the development of an autonomous hand control framework for artificial hand control. 

The application of the Support Vector Machine (SVM) to a non-invasive neural interface is principally limited to binary applications in the real world. In order to overcome this limitation an autonomous approach is developed to achieve better response and accuracy from NI control frameworks. In binary applications the SVM performed well with a classification accuracy of around 80% accompanied by a response time of just under 5 seconds. When applied to multiple classifications the SVM decreased in accuracy and response dramatically. The accuracy of the autonomous hand control framework had a classification accuracy of 95% with a response time comparable to that of the SVM. This outcome has the potential to move non-invasive NI research into the real world and to restore hand function in an intuitive and meaningful way. A key learning of this research is that machine learning methods for non-invasive neural interfaces are not the best way to restore hand function for amputees. Hand function is best restored through the combining of machine learning and machine vision into a single NI based control framework. Additionally, this work is based in Mātauranga Māori with a western science approach. By so doing, amputees will be empowered, have increased independence and enjoy a better quality of life.

The scope of this work is limited to the consideration of hand function restoration for upper extremity amputees. In particular trans-radial amputees. Focus is given to non-invasive methods of control, therefore, investigations are limited to the electroencephalography (EEG) signal. Mimicking the human grasping system is a complex and difficult process, therefore, the attempts in this work to restore hand function only consider mechanisms and processes related directly to the motor control of the human hand.

year: 2019