title: Measuring the bulk impedance of brain tissue in vitro

authors: Wilson, Marcus T.

abstract: Theoretical and numerical models of brain activity suggest a link between seizures and electrical connectivity. We have therefore been motivated to measure electrical conductivity in brain tissue. Such measurements in vitro are difficult; it is necessary to use a conductive inorganic salt solution, artificial cerebrospinal fluid (ACSF), to keep the tissue alive. We have attempted to provide a robust method to make such measurements. Mouse brain tissue was sliced (400 μm) using established methods. Half the slices were placed in standard ACSF; half were placed in ACSF devoid of magnesium ions. The latter case promotes seizure activity. Electrical activity was measured with a tungsten electrode at various places on the slices. Sixty-nine samples of cortex (2 mm × 2 mm) were cut with a razor. Their areas were measured with a calibrated microscope. Each sample was placed between two flat Ag/AgCl electrodes in a Perspex sandwich. Excess ACSF was removed with filter paper. The impedance was measured at 25°C from 20 Hz to 2 MHz with an Agilent E4980A four-point impedance meter in a shielded room, using a low current. Between 1 kHz and 100 kHz the conductivity was approximately 0.2 S m⁻¹; outside this range dispersion occurred. Samples prepared in the magnesium-free ACSF had a conductivity about 10% lower. The Cole-Cole model of conductivity was fitted. There were few significant differences between the parameters for the different groups measured.

text: Measuring the bulk impedance of brain tissue in vitro Theoretical and numerical models of brain activity suggest a link between seizures and electrical connectivity. We have therefore been motivated to measure electrical conductivity in brain tissue. Such measurements in vitro are difficult; it is necessary to use a conductive inorganic salt solution, artificial cerebrospinal fluid (ACSF), to keep the tissue alive. We have attempted to provide a robust method to make such measurements. Mouse brain tissue was sliced (400 μm) using established methods. Half the slices were placed in standard ACSF; half were placed in ACSF devoid of magnesium ions. The latter case promotes seizure activity. Electrical activity was measured with a tungsten electrode at various places on the slices. Sixty-nine samples of cortex (2 mm × 2 mm) were cut with a razor. Their areas were measured with a calibrated microscope. Each sample was placed between two flat Ag/AgCl electrodes in a Perspex sandwich. Excess ACSF was removed with filter paper. The impedance was measured at 25°C from 20 Hz to 2 MHz with an Agilent E4980A four-point impedance meter in a shielded room, using a low current. Between 1 kHz and 100 kHz the conductivity was approximately 0.2 S m⁻¹; outside this range dispersion occurred. Samples prepared in the magnesium-free ACSF had a conductivity about 10% lower. The Cole-Cole model of conductivity was fitted. There were few significant differences between the parameters for the different groups measured.

year: 2015

title: Beneath the Golden Facade: A History of the Early Years on the Thames Goldfields

authors: Johnson, Matthew Alan Barker

subjects: Thames

abstract: The story of Thames has been told and retold by many authors since the area was proclaimed a goldfield in 1867. These histories often glamourise the prosperity and wealth that gold brought to the town and its people. This thesis argues that this was not the case. In fact, the goldfields struggled for many years because the area lacked the necessary equipment to extract the gold. By 1870, machinery was steadily introduced and implemented, leading to short period of prosperity in the town, but it was temporary. Throughout the late 1860s and 1870s, locals experienced many financial hardships, which have been neglected by historians in favour of more positive portrayals of life on the goldfields. This thesis explores the economic situation of the town during this period, highlighting the experiences of those that failed to strike it rich on the goldfields. By examining their stories, it is clear that the romantic portrayal of life in early Thames was in the most part fiction compared to the harsh realities of those actually living on the goldfields.
Additionally, this thesis examines the role that the community played in improving the economic situation in Thames. The efforts of locals helped to develop and foster a diverse array of industries, which lessened the town’s reliance on the success of the goldfields. These improvements came at a time when Thames was suffering considerable economic pressures, thanks in large part to the decline in gold production after 1871.
This thesis utilises a range of primary and secondary sources to investigate the economic situation of Thames during this early period. It makes thorough use of newspaper articles, which highlight what information was readily available to local and external observers pertaining to the condition of the town. Government reports are used to show the role that officials played in the development of Thames and what actions they took to improve the local economy. This thesis also examines personal accounts from residents, which illustrate the harsh realities of life on the goldfields.

text: Beneath the Golden Facade: A History of the Early Years on the Thames Goldfields The story of Thames has been told and retold by many authors since the area was proclaimed a goldfield in 1867. These histories often glamourise the prosperity and wealth that gold brought to the town and its people. This thesis argues that this was not the case. In fact, the goldfields struggled for many years because the area lacked the necessary equipment to extract the gold. By 1870, machinery was steadily introduced and implemented, leading to short period of prosperity in the town, but it was temporary. Throughout the late 1860s and 1870s, locals experienced many financial hardships, which have been neglected by historians in favour of more positive portrayals of life on the goldfields. This thesis explores the economic situation of the town during this period, highlighting the experiences of those that failed to strike it rich on the goldfields. By examining their stories, it is clear that the romantic portrayal of life in early Thames was in the most part fiction compared to the harsh realities of those actually living on the goldfields.
Additionally, this thesis examines the role that the community played in improving the economic situation in Thames. The efforts of locals helped to develop and foster a diverse array of industries, which lessened the town’s reliance on the success of the goldfields. These improvements came at a time when Thames was suffering considerable economic pressures, thanks in large part to the decline in gold production after 1871.
This thesis utilises a range of primary and secondary sources to investigate the economic situation of Thames during this early period. It makes thorough use of newspaper articles, which highlight what information was readily available to local and external observers pertaining to the condition of the town. Government reports are used to show the role that officials played in the development of Thames and what actions they took to improve the local economy. This thesis also examines personal accounts from residents, which illustrate the harsh realities of life on the goldfields.

year: 2013

title: Mana Wahine Geographies: Spiritual, Spatial and Embodied Understandings of Papatūānuku

authors: Simmonds, Naomi Beth

subjects: Mana wahine

abstract: This thesis is a theoretical and empirical exploration of Māori women's knowledges and understandings of Papatūānuku in contemporary Aotearoa. The primary focus of this research is on the complexities, connections, and contradictions of Māori women's embodied relationships with the spaces of Papatūānuku - spaces that are simultaneously material, discursive, symbolic, and spiritual. In doing so, I displace the boundaries between coloniser/colonised, self/other, rational/irrational and scientific/spiritual. I demonstrate that Māori women's colonised realities produce multiple, complex and hybrid understandings of Papatūānuku. 

This thesis has three main strands. The first is theoretical. I offer mana wahine (Māori feminist discourses) as another perspective for geography that engages with the complex intersections of colonisation, race and gender. A mana wahine geography framework is a useful lens through which to explore the complexities of Māori women's relationships to space and place. This framework contributes to, and draws together, feminist geographies and Māori and indigenous academic scholarship.

Autobiographical material is woven with joint and individual semi-structured in-depth interviews conducted with nine Māori women in the Waikato region. The second strand, woven into this thesis, is a critical examination of the colonisation of Māori women's spiritual and embodied relationships to Papatūānuku. The invisibility of Māori women's knowledges in dominant conceptualisations of mythology, tikanga and wairua discourses is not a harmless omission rather it contains a political imperative that maintains the hegemony of colonialism and patriarchy. I argue that to understand further Māori women's relationships to space and place an examination of wairua discourses is necessary.

The third strand reconfigures embodied and spatial conceptualisations of Papatūānuku. Māori women's maternal bodies are intimately tied to Papatūānuku in a way that challenges the oppositional distinctions between mind/body and biology/social inscription. Māori women's maternal bodies (and the representation of them in te reo Māori) are constructed by, and in turn, construct Papatūānuku. Furthermore, women's spatial relationship to tūrangawaewae, home space and wider environmental concerns demonstrates the co-constitution of subjectivities, bodies and space/place. 

My hope is that this thesis will add to geographical literature by addressing previously ignored knowledges and that it will contribute to indigenous scholarship by providing a spatial perspective.

text: Mana Wahine Geographies: Spiritual, Spatial and Embodied Understandings of Papatūānuku This thesis is a theoretical and empirical exploration of Māori women's knowledges and understandings of Papatūānuku in contemporary Aotearoa. The primary focus of this research is on the complexities, connections, and contradictions of Māori women's embodied relationships with the spaces of Papatūānuku - spaces that are simultaneously material, discursive, symbolic, and spiritual. In doing so, I displace the boundaries between coloniser/colonised, self/other, rational/irrational and scientific/spiritual. I demonstrate that Māori women's colonised realities produce multiple, complex and hybrid understandings of Papatūānuku. 

This thesis has three main strands. The first is theoretical. I offer mana wahine (Māori feminist discourses) as another perspective for geography that engages with the complex intersections of colonisation, race and gender. A mana wahine geography framework is a useful lens through which to explore the complexities of Māori women's relationships to space and place. This framework contributes to, and draws together, feminist geographies and Māori and indigenous academic scholarship.

Autobiographical material is woven with joint and individual semi-structured in-depth interviews conducted with nine Māori women in the Waikato region. The second strand, woven into this thesis, is a critical examination of the colonisation of Māori women's spiritual and embodied relationships to Papatūānuku. The invisibility of Māori women's knowledges in dominant conceptualisations of mythology, tikanga and wairua discourses is not a harmless omission rather it contains a political imperative that maintains the hegemony of colonialism and patriarchy. I argue that to understand further Māori women's relationships to space and place an examination of wairua discourses is necessary.

The third strand reconfigures embodied and spatial conceptualisations of Papatūānuku. Māori women's maternal bodies are intimately tied to Papatūānuku in a way that challenges the oppositional distinctions between mind/body and biology/social inscription. Māori women's maternal bodies (and the representation of them in te reo Māori) are constructed by, and in turn, construct Papatūānuku. Furthermore, women's spatial relationship to tūrangawaewae, home space and wider environmental concerns demonstrates the co-constitution of subjectivities, bodies and space/place. 

My hope is that this thesis will add to geographical literature by addressing previously ignored knowledges and that it will contribute to indigenous scholarship by providing a spatial perspective.

year: 2009