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Spectroscopic and computational investigations of charge transfer excited states
Full text linkThe excited state properties of photoactive molecules govern their efficiency for a range of applications. In this thesis the excited states for a variety of compounds bearing different charge-transfer moieties were investigated. An assortment of spectroscopic techniques supported by density functional theory calculations were used to analyse these states.
The first series of complexes examined featured a 2,2'-bipyridine ligand with bulky triphenylamine substituents in the 6 and 6' positions (diTPAbpy) and demonstrated the importance of geometry on excited state photophysics. The ligand features a strong ILCT absorption which has a decreased intensity when complexed owing to an increased dihedral angle between the TPA and bpy moieties. Emission from a 1ILCT state is observed for the ligand and does not shift for the copper, silver, and rhenium complexes, with an additional 3MLCT emission observed for [Re(diTPAbpy)(CO3Cl]. Transient absorption measurements revealed the population of a 3ILCT for the homoleptic copper and silver complexes (τ = 80 ns). This is particularly notable for the copper complex as it shows that excited state reorganisation is minimised which is a common issue resulting in excited state quenching in other copper complexes.
Copper complexes were further investigated with either 2-pyridyl-1,2,3-triazole (pytri) or the triphenylamine (TPA) substituted (TPA-pytri) ligands alongside varied ancillary ligands. The TPA-pytri ligand introduced a strong ILCT absorption which was shown to be electronically disconnected from the MLCT state. The MLCT state was tuned to above or below the ILCT band (347 - 433 nm) with choice of ancillary ligand however no changes in the 1ILCT emission were observed.
A series of β-ferrocene-modified zinc porphyrins, with indandione and malononitrile based electron-withdrawing units appended to the ferrocene, were studied to investigate the interactions between π to π* and potential charge transfer states from the porphyrin to indandione. The ferrocene limited communication between the porphyrin and acceptor groups although its oxidation potential was able to be tuned by up to 0.3 V. The porphyrin singlet state was unaffected by ferrocene substitution, although the triplet state lifetime was lowered by up to 10.6 µs from that of the unsubstituted ferrocene porphyrin (18.1 µs). A loss in degeneracy of the porphyrin eg orbitals was found and accounted for the emission varying slightly in energy depending on the excitation wavelength.
Finally, a series of ruthenium and iridium complexes bearing ligands with a unique hydrogen-bonding moiety were investigated. A range of charge transfer states were identified which varied considerably in nature. Anionic ligands introduced LLCT transitions to the ancillary bipyridine or phenylpyridine ligands for the ruthenium and iridium complexes respectively which occurred at lower energy than the associated MLCT transitions. High energy ILCT transitions were introduced through pendant diaminotriazine units. Population of a longer lived 3ILCT state was shown for the iridium complexes while for the ruthenium complexes the lower energy MLCT states were shown to be rapidly populated. For all complexes no changes in their photophysical properties were observed in the presence of complimentary hydrogen-bonding species.
Throughout this thesis resonance Raman spectroscopy was used to support the assignments made for the excited states of the studied compounds These findings were further corroborated through DFT calculations. The species studied here demonstrated a range of excited state properties providing insights into the future design of photoactive materials
Searching for receptor(s) of the neuroprotective secreted Amyloid Precursor Protein alpha
Full text linkThe human brain protein, secreted amyloid precursor protein alpha (sAPPα), derived by proteolytic processing of a parent protein amyloid precursor protein (APP), contributes to healthy functioning of the brain as a neuroprotective protein. sAPPα is a counter to the neurotoxic effects of amyloid beta. Elucidating the molecular mechanisms by which sAPPα delivers these benefits to a healthy brain may be critical to developing meaningful therapies for Alzheimer’s disease.
This project characterises the potential of a tri-functional crosslinking reagent Sulfo-N-hydroxysuccinimidyl-2-(6-[biotinamido]-2-(p-azido benzamido)-hexanoamido) ethyl-1,3'-dithioproprionate (Sulfo-SBED) to identify the elusive receptor(s) for sAPPα. This reagent has three functional groups on three arms: (i) an NHS-Ester which forms covalent bonds with primary amines and can be used to attach the reagent to a ‘bait’ protein, in this project, sAPP; (ii) a phenyl azide which forms a covalent bond under UV exposure to proximal molecules. This is used to UV-link interacting proteins such as receptor(s) of the bait protein. In this project the interaction would bring the putative receptor into proximity of the phenyl azide on the reagent that is attached to the sAPPmolecule; (iii) a biotin molecule which can be used either for purification of the captured interacting protein(s) on an avidin affinity column and/or for Western blot analysis.
For attachment of the reagent to sAPPα, 200 mM Hepes buffer with 1 mM of reagent gave the best results to achieve a combination of maximum reagent attached with minimal loss of protein from precipitation. At higher concentrations of SBED significant loss of protein occurred. Mass spectrometry showed that of the lysine residues detected the reagent was attached specifically within sAPPα, and not randomly.
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Of a number of methods tested, the most effective way to remove excess SBED reagent was with a Zeba Spin column to achieve maximum removal of reagent and highest recovery of SBED labelled sAPPα. Dialysis caps, dialysis tubing, Viva Spin columns or G50 columns by comparison gave poor results.
Sensitivity and specificity were modelled with known interacting proteins of sAPP (specific antibodies and amyloid beta). A number of potential negative controls were evaluated and none were adequate. Results from UV-linking the sAPPα:reagent conjugate to neuroblastoma and primary hippocampal cells did not show specificity when comparing positive and negative controls. As non-specific UV-linking had also been observed when UV-linking to specific versus non-specific antibodies, it is possible that specificity could be significantly improved by reducing the residual reagent even further with multiple consecutive Zeba Spin columns.
The SBED reagent may be a good tool for identifying interactions between proteins of relatively high abundance but not so useful to identify receptors that may at any one time be present on cells in low numbers
Pharmacist Prescribing in New Zealand: Slow but steady growth.
Full text linkIntroduction: Pharmacist Prescriber roles are more common overseas however New Zealand is yet to see these roles expand at the same rate.
Aim: The aim of this study is to explore the development and integration of pharmacist prescribing roles in New Zealand from initial concept to the current situation.
Methods: This study has two separate phases, firstly a nationwide survey conducted between September until November 2019 of all current Pharmacist Prescribers in NZ. Secondly a case study on integration of a new pharmacist prescriber role at a GP practice.
Results: 70% of the current cohort of Pharmacist Prescribers (PP) in New Zealand participated in the first phase of this study. They identified a wide range of activities they undertake in their positions. They work within multi-disciplinary teams and typically have post graduate qualifications and more than 10 years working in similar roles prior to gaining their prescribing qualification. This additional qualification and skill allows more timely access to medication and advice for patients. The acceptance of pharmacist prescribers has been positive and health funders are looking to develop further positions.
A GP practice investigated the addition of a PP role to their practice with positive results, continuing to utilise the role in the practice with ongoing feedback and development to ensure the potential benefits are recognised and expanded.
Discussion: The current cohort of PP are demonstrating that their roles are beneficial to the teams they are working with, with a view to both broaden existing roles and develop additional roles around New Zealand
Chronic exercise and neuropsychological function in healthy, young adults: A randomised controlled trial investigating a running intervention
No full textRegular exercise is a well-known preventative measure against a multitude of mental and physical health issues. Despite this many of the world’s population do not currently engage in the recommended amount of physical activity. Chronic exercise (i.e., exercise repeated on multiple occasions over a prolonged period) has been identified as a key factor in driving biological mechanisms that improve cognitive performance and affect in most age groups. However, there is currently a poverty of relevant research in young adults. To address this, the current research investigated the effects of a running intervention on neuropsychological function in young adults. It was predicted that following a running intervention, participant’s neuropsychological performance would improve in line with increases in aerobic fitness. Thirty-two healthy and sedentary young adults were recruited from the University of Otago and randomised into either an intervention or control group, with the intervention group (n = 24) asked to run three times a week for 30 minutes at a time and the control group (n = 8) asked to remain sedentary over a 6-week period. Cognitive flexibility, visuospatial and verbal short-term memory and visuospatial and verbal working memory were tested at baseline and follow up, as well as positive and negative affect. The environmental conditions of the exercise and the participant’s enjoyment of the running were also recorded. For the most part repeated measures ANCOVAs failed to find significant effects on the neuropsychological measures or improvements in fitness after the running intervention. An improvement was observed in the runner group’s verbal working memory, although this cannot be related to improved fitness as was hypothesised. Whilst some interesting avenues for further research were identified relating to environment and enjoyment, overall the running intervention proved ineffective. Potential improvements to the design of the study are discussed, such as the use of a maximal fitness test, technology and targeting full-time workers who may have less access to exercise facilities
Effects of Hot and Cold Sports Drinks on Performance and Hydration in Cold Environments
No full textBackground: Winter sports and cold environments can present multiple challenges to athletes. Although, in cold temperatures, athletes will still sweat leading to increased rates of dehydration. If left unchecked, dehydration can negatively affect the performance of an athlete, even in cold environments. Sports drinks have been found to be effective in improving performance and limiting dehydration, however, most of this evidence is in hot environments with cold sports drinks. There is currently little research on cold sport drinks in cold environments and no research on hot sports drinks in cold environments.
Objective: The objective of this study was to investigate the performance and hydration effects of a hot sports drink (~50 °C) compared to a cold sports drink (~5 °C) during cycling exercise in a cold environment (~10 °C).
Design: This project was a randomised crossover intervention study where 14 participants consented to three separate trials. Participants VO2max was collected on cycle ergometer followed by 10 km time trial. In the main trials, participants were randomised either a hot or cold sports drink. The hot sports drink was served at 51.0 °C in an average environmental temperature 13.1 °C. The cold sports drink was served at 5.3 °C in an average environmental temperature of 12.9 °C. Participants completed four 15-minute bouts at a power consistent to 80% their respective VO2max. In the final minute of each bout, a maximal sprint was performed. A 10-minute break followed each bout where participants completed questionnaires (thermal comfort, thirst, and gastrointestinal questionnaires) and were supplied with their respective sports drink. Following the last bout and break, participants completed a 10 km time trial where they were blinded to time taken. Afterwards, participants completed questionnaires and were instructed to drink ad libitum of their sports drink for 30 minutes post exercise. One-week later participants undertook the exact same procedure with the opposite sports drink.
Results: Participants consumed significantly more of the ad libitum cold sports drink during the 30-minute post exercise. Thirst scores also significantly increased from baseline in both sport drink conditions but were not different from each other. The temperature of the sports drink had no significant effect on performance. There was no significant difference in percentage weight loss between both sports drinks.
Conclusion: The hot sports drink was no better or worse than the cold sports drink for performance and thirst scores in a cold environment. Although, a larger volume of the cold sports drink was consumed post exercise, this did not lead to a better hydration status compared to the hot sports drink in a cold environment
The Impact of Tidal Forcing on the Oceanography of the Northern Continental Shelf of New Zealand
No full textThe northern continental shelf is a unique region of the Aotearoa New Zealand shelf seas. The shelf ( 2.0 m s-1) and despite lying adjacent to warm, poleward flows of the East Auckland Current, the shelf is often enveloped by a large (>1000 km2) relatively cold pool of water. To date, the processes that generate this cold pool have not been fully resolved, with “upwelling” of the East Auckland Current onto the shelf previously put forward as a likely mechanism. However, the presence of strong tidal currents moving over shallow bathymetry on the shelf led to an alternative hypothesis that the cold pool may be the result of vertical mixing of the water column driven by the regional tidal circulation. The current study uses a combination of a regional tidal solution, high-resolution satellite ocean temperature data, and a regional ocean circulation model, to investigate the role that tidal forcing plays in generating and modulating this cold- water pool.
Analysis of a regional tidal solution shows that the M2, N2, and S2 are the three largest tidal constituents over the northern continental shelf. As the largest constituent, the characteristics of the M2 tide (amplitude, phase, velocity, and tidal ellipses) were examined in more detail. The amplitude of the M2 tidal velocity was also used to calculate a contoured map of the Simpson-Hunter (SH) parameter, as a proxy for the strength of stratification over the shelf. This map revealed low SH values (e.g. weak stratification) around the Three Kings Islands, Cape Maria van Diemen, above King Bank, and above Middlesex Bank. The SH values in these areas were similar to those found in other regions within New Zealand and globally that experience cool, well-mixed conditions due to tidal stirring. Charts of an adjusted SH parameter were also calculated at peak spring and neap tide, but these showed little change, due to the relatively small amplitude of the S2 relative to the M2 tidal constituent in this area.
A seasonal composite analysis of satellite-derived sea surface temperature (SST) data revealed three distinct cold-water pools over the northern continental shelf. These are located around the Three Kings Islands (inner pool), Cape Maria van Diemen (cape pool), and over the remainder of the shelf (outer pool). All three pools are visible during summer, but only the inner pool was visible during winter. Compositing of satellite SST data over the spring-neap and semi-diurnal cycle was then used to quantify the variability of the cold pools at tidal frequencies. The inner pool cooled (warmed) significantly during spring (neap) tides and this change became more evident when the cooling (heating) lagged peaked spring (neap) tides by two to four days. The edges of both the inner and cape cold-water pools were also found to advect horizontally consistent with the pattern expected from the strength and direction of the M2 tidal ellipse on the shelf.
Analysis of output from a regional ocean circulation model that included tidal forcing revealed similar patterns to the satellite observations on seasonal and spring-neap time scales. However, a model run without tidal forcing lacked any cold-water pool on the shelf. This highlights the dominant role played by tidal processes in generating the shelf cold pool. Full-depth transects extracted across the shelf showed significantly cooler waters in the upper and lower water column at spring compared to neap tides. Bottom water temperature on the shelf edge also appears to fluctuate at a semi-diurnal frequency consistent with forcing by the M2 tide and is suggestive of cold water being pumped onto and off the shelf by the internal tide.
Collectively, these analyses suggest that the cold-water pools observed on the northern continental shelf of New Zealand are primarily generated by tidal forcing. A dominant process
appears to be tidal mixing, where strong tidal currents vertically mix the water column above the shallow bathymetry. Several other processes, including horizontal advection by tidal currents, mesoscale eddies, boundary currents, and subsurface processes associated with the internal tide likely play an important role in controlling the cold pools' position and temperature. Distinguishing the processes driving and modulating these cold pools allows insight into the underlying biogeochemistry on the shelf. The nature of tidal mixing regimes can increase nutrient concentrations within the photic zone, increasing primary production. However, the patchy distribution of these nutrients and the pools' distribution across the shelf may cause high variability in primary productivity, both spatially and temporally
When my parents tell their stories: The investigation of vicarious memories in the family context
No full textStories that have not been personally experienced by children and are only told by their parents are called vicarious family stories (e.g., Pillemer et al., 2015). A burgeoning body of literature has shown that vicarious family stories are an important part of children’s narrative ecology (e.g., Fivush & Merrill, 2016; Merrill & Fivush, 2016). However, to date, only a handful of studies have examined the role of vicarious family stories in adulthood years. The primary aim of the present thesis was to extend the boundaries of research by examining the role of individual, familial, and cultural characteristics in vicarious family stories of young, middle-aged, and older adults.
In the first study, we investigated the characteristics of vicarious family stories in the Turkish cultural context. Seventy-two Turkish families including three generations of women and men from different samples of families were recruited. Results can be described in three main sections: a) intrafamilial similarities; b) gender differences; and c) cross-generational differences. For intrafamilial similarities, members of the same family showed similarities in terms of the volume and number of other-related words. For gender differences, women focused more on social interactions, used more other-related words and subjective perspective terms, and made more identity connections between others and parents than men. When describing their parents’ reasons for telling family stories, women were also less likely to report development and teaching reasons and more likely to report emotional reasons compared to men. For cross-generational differences, the oldest generation’s stories were less coherent than the youngest and middle generations’, and less voluminous than the middle generation’s. Additionally, the youngest generation reported entertainment reasons more often than the oldest generation. Emotional reasons were more common for the middle generation than for the youngest and oldest generations.
In the second study, we examined whether vicarious family stories are linked to family climate and well-being among young, middle-aged, and older adults across two different samples from Turkey. In total, there were 168 triads of Turkish families (N = 504). Across Sample 1 (written narratives) and Sample 2 (spoken narratives), we found a significant link between family climate and well-being. In addition, participants from Sample 2 who experienced a more positive family climate narrated more coherent family stories. The results also revealed that participants from Sample 1 who rated their stories as more emotionally positive and participants from Sample 2 who included more identity connections in their stories reported higher levels of well-being.
In the third study, we examined the characteristics of vicarious family stories about mothers across Turkish and New Zealand (NZ) cultures and investigated individual variations in cultures with regards to the internalisation of cultural orientations (i.e., self-construals). There were 108 Turkish and 79 NZ women in this study. We found that Turkish women’s stories were more thematically coherent and included more social interactions and other-related words than NZ women’s. In addition, when reporting reasons for why they think family members told stories, didactic purposes and expressing emotions were more common reasons for Turkish women, whereas sharing family history and entertainment were more common reasons for NZ women. However, Turkish and NZ women’s vicarious stories were similar in terms of identity connections and affective tone. Counter to our expectations, we did not find a significant role of individuals’ self-construals in the link between culture and vicarious stories about mothers.
Overall, the present thesis: a) contributes to the growing area of research on family narratives by examining the elements of narrative identity in family stories across three generations; b) emphasises the links to well-being for family climate and family stories, and highlights the importance of capturing different characteristics of vicarious stories (elicited via different methods) across generations; c) extends our knowledge by showing the commonalities and differences in the construction of vicarious family stories across cultures; and d) supports the ecological system approach to family narratives (see Fivush & Merrill, 2016) by demonstrating that vicarious family stories are heard and internalised by younger generations (see also Reese, Fivush, et al., 2017; Zaman & Fivush, 2011)
Phylogenetics of the D1 protein family in Cyanobacteria and the characterisation of novel D1 variants
No full textCyanobacteria perform oxygenic photosynthesis using the water:plastoquinone oxidoreductase Photosystem II (PS II), a catalyst responsible for water splitting. A core protein of PS II is D1 which provides the majority of the ligands to the water splitting complex and binds several other key ligands within PS II. The D1 protein is highly conserved in Cyanobacteria and photosynthetic eukaryotes. Phylogenetic analyses have shown that there are multiple, distinct types of the D1 protein in Cyanobacteria which are upregulated in response to a variety of physiological and environmental conditions. These forms of the D1 protein may fine-tune photosynthetic activity in response to environmental conditions ranging from high light to the subjective dark. In this study, these previous phylogenetic analyses were expanded to include the D1 proteins from 206 cyanobacterial strains. This extended analysis of the D1 protein family identified distinct D1 sequences that separates into two additional sub-groups.
One of these sub-groups (D1INT) predominantly occurs in the genomes of nitrogen-fixing heterocystous cyanobacteria and the psbA gene encoding this D1 was shown in this study to be upregulated during nitrogen induced hormogonia differentiation in the heterocystous cyanobacterium, Nostoc punctiforme. The second sub-group (D1FR) is associated with the far-red light photoacclimation (FaRLiP) response which allows cyanobacteria to utilise far-red / near infrared light, unavailable to the majority of oxygenic photosynthetic organisms.
This project characterised how both D1INT and D1FR alter photosynthetic performance when expressed in the model cyanobacterium, Synechocystis sp. PCC 6803. Both proteins were incorporated into PS II centres, but retarded the performance of PS II. D1INT-containing PS II centres were assembled at lower levels and more prone to photoinhibition than PS II centres with the native D1 protein. A strain with only D1FR-containing centres was not photoautotrophic, both in the presence and absence of chlorophyll f synthase and a variant of the D2 protein associated with the FaRLiP response, D2FR. Insertion of characteristic residues associated with the D1FR protein in the native D1 protein of Synechocystis sp. PCC 6803 showed that alterations to the D1 protein impact the physiological performance of PS II and provide a rationale for the abolishment of photoautotrophy in the D1FR background
Temporal Effects of Thwarted Belonging and Perceived Burden on Suicidal Ideation
No full textSuicide is one of the leading causes of death worldwide. The incidence rate of suicide, particularly among young people, is still high in New Zealand. A great amount of research on suicidality has identified some risk factors for suicidal ideation and suicide attempts. However, these research results have not yet been translated into effective strategies of prevention or intervention. The interpersonal theory of suicide—one of the most studied theories of suicide—attempts to integrate risk factors of suicide into a causal pathway. The theory assumes that thwarted belonging and perceived burden are equally important and are the most proximal mental states in the development of suicidal ideation. Although a number of studies have provided evidence to support the interpersonal theory, the results have been mixed. The present thesis aimed to examine the controversial parts of the interpersonal theory regarding the relationships among thwarted belonging, perceived burden, and active suicidal ideation using a 4-wave longitudinal survey among 298 undergraduate students.
In Study 1, a cross-sectional analysis of baseline data was conducted to test the proposed hypotheses. The results showed that thwarted belonging had no direct influence on active ideation. Perceived burden was found to both mediate and moderate the relationship between thwarted belonging and active ideation. In Study 2, the cross-lagged panel model (CLPM) and single-level random-effects CLPM (RE-CLPM) were used to test the mediation hypothesis with longitudinal data. The cross-sectional results, however, could not be confirmed in this longitudinal mediation analysis. Similarly, in Study 3, the moderation effect in the cross-sectional study could not be confirmed using either the CLPM or RE-CLPM analyses. In Study 4, a post-hoc analysis of the longitudinal data used in Study 2 and Study 3 was conducted to test whether the follow-up interval between perceived burden and active ideation could influence the relationship between perceived burden and active ideation, and also the mediation and moderation effects. When the follow-up period was shortened to concurrency, the relationship between perceived burden and active ideation was stronger, and the moderation and mediation effects showed significant in the RE-CLPM models, after controlling autoregression for each variable.
Overall, these results provide support that thwarted belonging has an indirect effect on active ideation. Additionally, the new mediation hypothesis—that the relationship between thwarted belonging and active ideation was mediated by perceived burden—obtained support only when the time interval between perceived burden and active ideation was concurrent. Similarly, the moderation hypothesis—that the interaction of thwarted belonging and perceived burden influences active ideation—also obtained support under the same circumstance. The findings in the thesis have significant implications in the psychological mechanisms and the prevention and intervention of suicide. Finally, it will be a fruitful avenue for future studies to confirm the results and overcome the issues raised in the thesis
Standardisation and Data Augmentation in Genetic Programming
Full text linkUnder review at IEEE Transactions on Evolutionary ComputationGenetic programming (GP) is a common method for performing symbolic regression that relies on the use of ephemeral random constants in order to adequately scale predictions. Suitable values for these constants must be drawn from appropriate, but typically unknown, distributions for the problem being modelled. While rarely used with GP, Z-score standardisation of feature and response spaces often significantly improves the predictive performance of GP by removing scale issues and reducing error due to bias. However, in some cases it is also associated with erratic error due to variance. This paper demonstrates that this variance component increases in the presence of gaps at the boundaries of the training data explanatory variable intervals. An initial solution to this problem is proposed that augments training data with pseudo instances located at the boundaries of the intervals. When applied to benchmark problems, particularly with small training samples, this solution reduces error due to variance and therefore total error. Augmentation is shown to also stabilise error in larger problems, however results suggest that standardised GP works well on such problems with little need for training data augmentation