title: Equilibration of D-Glucaric Acid in Aqueous Solution

authors: Brown, Jolene Mary

subjects: D-glucaric acid

abstract: Abstract

The equilibrium of aqueous D-glucaric acid was investigated via Nuclear Magnetic Resonance (NMR) spectroscopy. The NMR spectra of all four species (D-glucaric acid, D-glucaro-1,4-lactone, D-glucaro-6,3- lactone and D-glucaro-1,4;6,3-lactone) were assigned.

A 1H NMR spectroscopy method was developed to investigate the kinetics of equilibration of the starting species (D-glucaro-1,4-lactone and D-glucaro-1,4;6,3-dilactone). The equilibration was investigated under neutral conditions as well as conditions with increasing acidity. 

Each experiment set contained 50-100 1HNMR spectroscopy experiments that were run on the same sample using a program that built in delays. Dimethyl sulfoxide was used as an internal standard, and its signal size was used as a scale to report the changes in relative concentration of the four species throughout the experiment sets.

Under neutral conditions D-glucaro-1,4-lactone is relatively stable against equilibration, while D-glucaro-1,4;6,3-dilactone is not. Under acidic conditions both compounds equilibrate within approximately 30,000 seconds. After equilibration under acidic conditions D-glucaric acid is the dominant species, while the relative concentration of D-glucaro-1,4-lactone is slightly higher than that of D-glucaro-6,3-lactone. The relative equilibrium concentration of D-glucaro-1,4;6,3-dilactone is low.

A mechanism for the equilibration of aqueous D-glucaric acid was proposed and equilibrium constants and estimates of rate constants were derived from the experimental data. These rate constants were used in MATLAB simulations that were compared to the experimental data. MATLAB simulations were used to alter the rate constants to improve the fits between experimental data and simulated data.

text: Equilibration of D-Glucaric Acid in Aqueous Solution Abstract

The equilibrium of aqueous D-glucaric acid was investigated via Nuclear Magnetic Resonance (NMR) spectroscopy. The NMR spectra of all four species (D-glucaric acid, D-glucaro-1,4-lactone, D-glucaro-6,3- lactone and D-glucaro-1,4;6,3-lactone) were assigned.

A 1H NMR spectroscopy method was developed to investigate the kinetics of equilibration of the starting species (D-glucaro-1,4-lactone and D-glucaro-1,4;6,3-dilactone). The equilibration was investigated under neutral conditions as well as conditions with increasing acidity. 

Each experiment set contained 50-100 1HNMR spectroscopy experiments that were run on the same sample using a program that built in delays. Dimethyl sulfoxide was used as an internal standard, and its signal size was used as a scale to report the changes in relative concentration of the four species throughout the experiment sets.

Under neutral conditions D-glucaro-1,4-lactone is relatively stable against equilibration, while D-glucaro-1,4;6,3-dilactone is not. Under acidic conditions both compounds equilibrate within approximately 30,000 seconds. After equilibration under acidic conditions D-glucaric acid is the dominant species, while the relative concentration of D-glucaro-1,4-lactone is slightly higher than that of D-glucaro-6,3-lactone. The relative equilibrium concentration of D-glucaro-1,4;6,3-dilactone is low.

A mechanism for the equilibration of aqueous D-glucaric acid was proposed and equilibrium constants and estimates of rate constants were derived from the experimental data. These rate constants were used in MATLAB simulations that were compared to the experimental data. MATLAB simulations were used to alter the rate constants to improve the fits between experimental data and simulated data.

year: 2007

title: Line mesh distributions: An alternative approach for multivariate environmental extremes

authors: Bardsley, W. Earl

subjects: Line mesh distribution

abstract: Copulas and other multivariate models can give joint exceedance probabilities for multivariate events in the naturalenvironment. However, the choice of the most appropriate multivariate model may not always be evident in the absence ofknowledge of dependence structures. A simple nonparametric alternative is to approximate multivariate dependenciesusing ‘‘line mesh distributions’’, introduced here as a data-based finite mixture of univariate distributions defined on a meshof L =C(m, 2) lines extending through Euclidean n-space. That is, m data points in n-space define a total of L lines, whereC() denotes the binomial coefficient. The utilitarian simplicity of the method has attraction for joint exceedance proba-bilities because just the data and a single bandwidth parameter within the 0, 1 interval are needed to define a line meshdistribution. All bivariate planes in these distributions have the same Pearson correlation coefficients as the correspondingdata. Marginal means and variances are similarly preserved. Using an example from the literature, a 5-parameter bivariateGumbel model is replaced with a 1-parameter line mesh distribution. A second illustration for three dimensions applies linemesh distributions to data simulated from a trivariate copula.

text: Line mesh distributions: An alternative approach for multivariate environmental extremes Copulas and other multivariate models can give joint exceedance probabilities for multivariate events in the naturalenvironment. However, the choice of the most appropriate multivariate model may not always be evident in the absence ofknowledge of dependence structures. A simple nonparametric alternative is to approximate multivariate dependenciesusing ‘‘line mesh distributions’’, introduced here as a data-based finite mixture of univariate distributions defined on a meshof L =C(m, 2) lines extending through Euclidean n-space. That is, m data points in n-space define a total of L lines, whereC() denotes the binomial coefficient. The utilitarian simplicity of the method has attraction for joint exceedance proba-bilities because just the data and a single bandwidth parameter within the 0, 1 interval are needed to define a line meshdistribution. All bivariate planes in these distributions have the same Pearson correlation coefficients as the correspondingdata. Marginal means and variances are similarly preserved. Using an example from the literature, a 5-parameter bivariateGumbel model is replaced with a 1-parameter line mesh distribution. A second illustration for three dimensions applies linemesh distributions to data simulated from a trivariate copula.

year: 2019

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