title: Assessment of roughness and chemical modification in determining the hydrophobic properties of metals

authors: Larmour, Iain A.

subjects: chemistry

abstract: “Etch and coat” methods, potentially useful for large scale production of superhydrophobic surfaces on metals, have been extended by introduction of a thin 20 nm Au interlayer which allowed thiol surface modifiers to be investigated. Fe, Ti and Zn surfaces modified in this way with a polyfluorothiol generally had lower contact angles, θ, than their silane modified equivalents but were more uniform and reproducible. The higher θ values for silanes appear to be associated with an increased effective roughness that is not seen in the thiol coatings, which follow the underlying surface. For Fe, Ti and Zn, θ increased to a maximum with etching time but then decreased significantly. Electron microscopy of samples etched for long times showed fewer grain boundaries, suggesting that the loss of hydrophobicity was related to reduced roughness. This was confirmed through quantitative measurements of roughness parameters which were directly correlated with the observed contact angles through the Wenzel equation. The observation of this behaviour for 3 different metals suggests it is a general effect and the assumption that increased etch times will give increased roughness is incorrect. Although etching , Au coating and thiol modification did not provide sufficient roughness for superhydrophobicity, electrodeposition of a Cu layer onto the metal substrates followed by electroless deposition of silver gave uniform surfaces with very high contact angles (up to θ = 168.9°) and low roll-off angles (α < 1°). This method is sufficiently simple and inexpensive to be suitable for application on industrial scales, for example in marine or aeronautical engineering.

text: Assessment of roughness and chemical modification in determining the hydrophobic properties of metals “Etch and coat” methods, potentially useful for large scale production of superhydrophobic surfaces on metals, have been extended by introduction of a thin 20 nm Au interlayer which allowed thiol surface modifiers to be investigated. Fe, Ti and Zn surfaces modified in this way with a polyfluorothiol generally had lower contact angles, θ, than their silane modified equivalents but were more uniform and reproducible. The higher θ values for silanes appear to be associated with an increased effective roughness that is not seen in the thiol coatings, which follow the underlying surface. For Fe, Ti and Zn, θ increased to a maximum with etching time but then decreased significantly. Electron microscopy of samples etched for long times showed fewer grain boundaries, suggesting that the loss of hydrophobicity was related to reduced roughness. This was confirmed through quantitative measurements of roughness parameters which were directly correlated with the observed contact angles through the Wenzel equation. The observation of this behaviour for 3 different metals suggests it is a general effect and the assumption that increased etch times will give increased roughness is incorrect. Although etching , Au coating and thiol modification did not provide sufficient roughness for superhydrophobicity, electrodeposition of a Cu layer onto the metal substrates followed by electroless deposition of silver gave uniform surfaces with very high contact angles (up to θ = 168.9°) and low roll-off angles (α < 1°). This method is sufficiently simple and inexpensive to be suitable for application on industrial scales, for example in marine or aeronautical engineering.

year: 2008

title: Coupling constant metamorphosis and Nth-order symmetries in classical and quantum mechanics

authors: Kalnins, Ernie G.

subjects: mathematics

abstract: We review the fundamentals of coupling constant metamorphosis (CCM) and the Stäckel transform, and apply them to map integrable and superintegrable systems of all orders into other such systems on different manifolds. In general, CCM does not preserve the order of constants of the motion or even take polynomials in the momenta to polynomials in the momenta. We study specializations of these actions which preserve polynomials and also the structure of the symmetry algebras in both the classical and quantum cases. We give several examples of non-constant curvature third- and fourth-order superintegrable systems in two space dimensions obtained via CCM, with some details on the structure of the symmetry algebras preserved by the transform action.

text: Coupling constant metamorphosis and Nth-order symmetries in classical and quantum mechanics We review the fundamentals of coupling constant metamorphosis (CCM) and the Stäckel transform, and apply them to map integrable and superintegrable systems of all orders into other such systems on different manifolds. In general, CCM does not preserve the order of constants of the motion or even take polynomials in the momenta to polynomials in the momenta. We study specializations of these actions which preserve polynomials and also the structure of the symmetry algebras in both the classical and quantum cases. We give several examples of non-constant curvature third- and fourth-order superintegrable systems in two space dimensions obtained via CCM, with some details on the structure of the symmetry algebras preserved by the transform action.

year: 2010

title: Tukua Kia Rere! Maori Adult Students Succeeding at University

authors: Williams, Daphne Christina (Tina)

subjects: Maori students in higher education

abstract: A considerable amount of research has focussed on Māori underachievement in mainstream education. There is, however, much less research that celebrates Māori academic success. Even less has been written about the experiences of adult Māori students who return to study long after leaving school and go on to become academically successful in higher education. This study contributes to the growing body of knowledge regarding Māori academic success at university. It sought to explore the experiences of sixteen adult Māori students who entered university via special admission and went on to attain undergraduate degrees. The study examined the challenges that these individual’s experienced on their way to becoming academically successful and identified the main factors that helped them to achieve educational success. An overarching Kaupapa Māori theoretical framework was employed in this study. A qualitative research methodology was implemented and Kaupapa Māori research principles informed both the research processes and the interpretation of research outcomes. The findings suggest four major factors contributed to the success of the participants in this study: a strong determination to succeed (whāia te iti kahurangi), the extended family (whānau), strong social support networks with peers and faculty (whakawhanaungatanga) and Te Ao Māori (the Māori World). However, some of these same factors were also found to hinder academic success in the university setting. The Manu Tukutuku (kite) model was developed directly from the research findings. In addition to providing a theoretical frame for understanding the experiences of Māori special admission students at university, this model also provides a useful ‘toolkit’ for those wanting to support Māori students within the university context. The implications of this study suggest that New Zealand Universities can better support Māori special admission students by being more inclusive of their cultural capital, by eliminating racism and discrimination in the university environment and by fostering better relationships between staff and students. Creating opportunities for Māori students to develop social networks at University was also identified as important.

text: Tukua Kia Rere! Maori Adult Students Succeeding at University A considerable amount of research has focussed on Māori underachievement in mainstream education. There is, however, much less research that celebrates Māori academic success. Even less has been written about the experiences of adult Māori students who return to study long after leaving school and go on to become academically successful in higher education. This study contributes to the growing body of knowledge regarding Māori academic success at university. It sought to explore the experiences of sixteen adult Māori students who entered university via special admission and went on to attain undergraduate degrees. The study examined the challenges that these individual’s experienced on their way to becoming academically successful and identified the main factors that helped them to achieve educational success. An overarching Kaupapa Māori theoretical framework was employed in this study. A qualitative research methodology was implemented and Kaupapa Māori research principles informed both the research processes and the interpretation of research outcomes. The findings suggest four major factors contributed to the success of the participants in this study: a strong determination to succeed (whāia te iti kahurangi), the extended family (whānau), strong social support networks with peers and faculty (whakawhanaungatanga) and Te Ao Māori (the Māori World). However, some of these same factors were also found to hinder academic success in the university setting. The Manu Tukutuku (kite) model was developed directly from the research findings. In addition to providing a theoretical frame for understanding the experiences of Māori special admission students at university, this model also provides a useful ‘toolkit’ for those wanting to support Māori students within the university context. The implications of this study suggest that New Zealand Universities can better support Māori special admission students by being more inclusive of their cultural capital, by eliminating racism and discrimination in the university environment and by fostering better relationships between staff and students. Creating opportunities for Māori students to develop social networks at University was also identified as important.

year: 2010