title: Sedimentation in Antarctic proglacial lakes

authors: Sadler, Anthony John

abstract: A variety of Antarctic lakes occur either as proglacial lakes to glaciers, or as detached lakes within an enclosed drainage system in the Dry Valleys of McMurdo Sound, Antarctica. Some of these are the evaporated remnants of much larger proglacial lakes that formed during the last glacial, when the Ross Ice Shelf thickened, grounding on the continental shelf, and advanced landward entering many of the Dry Valleys. These former proglacial lakes have been the source of datable material using U/Th methods on the products of evaporation (CaC0₃), and ¹⁴C on algal deposits associated with many lacustrine sediments. These methods provide dates for glacial advances and hence allow correlation with similar northern hemisphere events.
Interpretation of both the data generated, and morphologic evidence for paleo-lacustrine environments, requires a knowledge of how these former lakes developed and the processes occurring within them. To this end a modem proglacial lake, Trough Lake in Pyramid Trough, was selected to study and provide a model for sedimentation in the former lakes as well as a guide for interpretation of former proglacial environments.
Although Trough Lake is proglacial to an alpine glacier, not a large ice sheet, and it is much smaller than the former lakes, it makes a satisfactory surrogatte. The principle aim was to examine the sedimentary processes occurring within the lake and to use this information to construct a facies model for the interpretation of former pro glacial lacustrine environments.
The transport of ice-rafted, formerly glacial material, across the lake ice and the changes that occur to it have been examined. The results indicate that aeolian processes, as well as extraction of the fine fraction through the lake ice, occur concentrating the coarse fraction in ice-cored domes at the distal end of the lake. The fine fraction if it migrates through the lake ice becomes part of the normal, predominantly silt, lacustrine sediments. However, the distance a sand particle can move through the ice is size dependent, the coarser the material the smaller the distance it can migrate downward. This sand/ice interaction manifests itself in bimodal lacustrine sediments becoming progressively coarser away from the glacier until a point is reached where all the sand fraction that can migrate through the ice, has done so, and beyond this, lacustrine sediments will be unimodal. Thus it is apparent, that grain size distribution analysis of proglacial lacustrine sediments, and their associated drift, can be very useful in determining the size and structure of former Antarctic proglacial lakes.
The calving of icebergs from the glacier snout and their eventual replacement by lake ice provides a mechanism by which lake ice can move at a rate of about 18 m per year (at Trough Lake) away from the glacier.
The formation of the characteristic ice-cored domes found on many pro glacial or former proglacial lakes in the Mcurdo Sound area was demonstrated in a laboratory experiment designed to model the Antarctic environment. These domes are important as they often cover and preserve underlying lacustrine silts and algae when left behind by falling lake levels through retreat of the associated glacier. In addition these deposits can be used to gauge the extent of former lakes as well as providing samples for ¹⁴C dating.
Evidence of seasonal cracks within the lake was observed and a core of sediment deposited through such a crack was extracted. This suggests another method by which lacustrine silts may be preserved in a very dry and windy Antarctic environment
The physics of sand/ice interactions was examined in some detail, and it was demonstrated that the feasibility of sand moving through ice was not size related as had been suggested by some workers, however the rate at which sand moves through ice is inversely proportional to grain size. This provides a non-structural mechanism by which sand can move through lake ice and accumulate within the normal lacustrine sediments.
By measuring temperature and chemical variation through the water column and the light penetrating the lake ice a model for a reverse convection cell operating within the lake was devised, and this explains how such a deep lake can maintain a very homogeneous water temperature and chemistry.
Finally with the accumulated information a model for present and past proglacial lacustrine sedimentation was developed and this was used as the basis for a proposed facies model for paleo-proglacial lacustrine environments.

text: Sedimentation in Antarctic proglacial lakes A variety of Antarctic lakes occur either as proglacial lakes to glaciers, or as detached lakes within an enclosed drainage system in the Dry Valleys of McMurdo Sound, Antarctica. Some of these are the evaporated remnants of much larger proglacial lakes that formed during the last glacial, when the Ross Ice Shelf thickened, grounding on the continental shelf, and advanced landward entering many of the Dry Valleys. These former proglacial lakes have been the source of datable material using U/Th methods on the products of evaporation (CaC0₃), and ¹⁴C on algal deposits associated with many lacustrine sediments. These methods provide dates for glacial advances and hence allow correlation with similar northern hemisphere events.
Interpretation of both the data generated, and morphologic evidence for paleo-lacustrine environments, requires a knowledge of how these former lakes developed and the processes occurring within them. To this end a modem proglacial lake, Trough Lake in Pyramid Trough, was selected to study and provide a model for sedimentation in the former lakes as well as a guide for interpretation of former proglacial environments.
Although Trough Lake is proglacial to an alpine glacier, not a large ice sheet, and it is much smaller than the former lakes, it makes a satisfactory surrogatte. The principle aim was to examine the sedimentary processes occurring within the lake and to use this information to construct a facies model for the interpretation of former pro glacial lacustrine environments.
The transport of ice-rafted, formerly glacial material, across the lake ice and the changes that occur to it have been examined. The results indicate that aeolian processes, as well as extraction of the fine fraction through the lake ice, occur concentrating the coarse fraction in ice-cored domes at the distal end of the lake. The fine fraction if it migrates through the lake ice becomes part of the normal, predominantly silt, lacustrine sediments. However, the distance a sand particle can move through the ice is size dependent, the coarser the material the smaller the distance it can migrate downward. This sand/ice interaction manifests itself in bimodal lacustrine sediments becoming progressively coarser away from the glacier until a point is reached where all the sand fraction that can migrate through the ice, has done so, and beyond this, lacustrine sediments will be unimodal. Thus it is apparent, that grain size distribution analysis of proglacial lacustrine sediments, and their associated drift, can be very useful in determining the size and structure of former Antarctic proglacial lakes.
The calving of icebergs from the glacier snout and their eventual replacement by lake ice provides a mechanism by which lake ice can move at a rate of about 18 m per year (at Trough Lake) away from the glacier.
The formation of the characteristic ice-cored domes found on many pro glacial or former proglacial lakes in the Mcurdo Sound area was demonstrated in a laboratory experiment designed to model the Antarctic environment. These domes are important as they often cover and preserve underlying lacustrine silts and algae when left behind by falling lake levels through retreat of the associated glacier. In addition these deposits can be used to gauge the extent of former lakes as well as providing samples for ¹⁴C dating.
Evidence of seasonal cracks within the lake was observed and a core of sediment deposited through such a crack was extracted. This suggests another method by which lacustrine silts may be preserved in a very dry and windy Antarctic environment
The physics of sand/ice interactions was examined in some detail, and it was demonstrated that the feasibility of sand moving through ice was not size related as had been suggested by some workers, however the rate at which sand moves through ice is inversely proportional to grain size. This provides a non-structural mechanism by which sand can move through lake ice and accumulate within the normal lacustrine sediments.
By measuring temperature and chemical variation through the water column and the light penetrating the lake ice a model for a reverse convection cell operating within the lake was devised, and this explains how such a deep lake can maintain a very homogeneous water temperature and chemistry.
Finally with the accumulated information a model for present and past proglacial lacustrine sedimentation was developed and this was used as the basis for a proposed facies model for paleo-proglacial lacustrine environments.

year: 1989

title: Connecting the Points: An Investigation into Student Learning about Decimal Numbers

authors: Moody, Bruce David

subjects: Decimals

abstract: The purpose of this research project was to investigate the effects of a short-term teaching experiment on the learning of decimal numbers by primary students. The literature describes this area of mathematics as highly problematic for students. 
The content first covered student understanding of decimal symbols, and how this impacted upon their ability to order decimal numbers and carry out additive operations. It was then extended to cover the density of number property, and the application of multiplicative operations to situations involving decimals. In doing so, three areas of cognitive conflict were encountered by students, the belief that longer decimal numbers are larger than shorter ones (irrespective of the actual digits), that multiplication always makes numbers bigger, and that division always makes numbers smaller. 
The use of a microgenetic approach yielded data was able to be presented that provides details of the environment surrounding the moments where new learning was constructed. The characteristics of this environment include the use of physical artifacts and situational contexts involving measurement that precipitate student discussion and reflection. 
The methodology allowed for the collection of evidence regarding the highly complex nature of the learning, with evidence of 'folding back' to earlier schema and the co-existence of competing schema.   The discussion presents reasons as to why the pedagogical approach that was employed facilitated learning. 
One of the main findings was that the use of challenging problems situated in measurement contexts that involved direct student participation promoted the extension and/or re-organization of student schema with regard to decimal numbers. 
The study has important implications for teachers at the upper primary level wanting to support student learning about the decimal numbers system.

text: Connecting the Points: An Investigation into Student Learning about Decimal Numbers The purpose of this research project was to investigate the effects of a short-term teaching experiment on the learning of decimal numbers by primary students. The literature describes this area of mathematics as highly problematic for students. 
The content first covered student understanding of decimal symbols, and how this impacted upon their ability to order decimal numbers and carry out additive operations. It was then extended to cover the density of number property, and the application of multiplicative operations to situations involving decimals. In doing so, three areas of cognitive conflict were encountered by students, the belief that longer decimal numbers are larger than shorter ones (irrespective of the actual digits), that multiplication always makes numbers bigger, and that division always makes numbers smaller. 
The use of a microgenetic approach yielded data was able to be presented that provides details of the environment surrounding the moments where new learning was constructed. The characteristics of this environment include the use of physical artifacts and situational contexts involving measurement that precipitate student discussion and reflection. 
The methodology allowed for the collection of evidence regarding the highly complex nature of the learning, with evidence of 'folding back' to earlier schema and the co-existence of competing schema.   The discussion presents reasons as to why the pedagogical approach that was employed facilitated learning. 
One of the main findings was that the use of challenging problems situated in measurement contexts that involved direct student participation promoted the extension and/or re-organization of student schema with regard to decimal numbers. 
The study has important implications for teachers at the upper primary level wanting to support student learning about the decimal numbers system.

year: 2008

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