title: Sexual network random effects models of migration and spread of HIV and other STIs in South Africa

authors: Zuma, K.

abstract: South Africa is experiencing an explosive epidemic of Human Immunodeficiency Virus (HIV) and of Sexually Transmitted Infections (STI)s. Furthermore, South Africa has extraordinarily high rates of migration. The predominant type of migration is the circular migration in which young men migrate to work in urban areas leaving their sexual partners behind, to whom they return periodically. Conditions of migration bring men into sexual contact with prostitutes and other women at high risk of HIV /STIs. In this way, migrant men form sexual networks, which become a critical bridge for transmitting HIV /STIs between rural and urban areas. 
The thesis investigates the determinants of HIV and those of STIs, taking into account the migration status and sexual network clustering effect in the data. The data investigated is from cohorts of migrant men from Hlabisa district working in urban areas, non-migrant partner(s) of migrant men residing in Hlabisa district, non-migrant men and their non-migrant partner(s) residing in Hlabisa district in northern KwaZulu-Natal, South Africa. Initially, the expectation-maximization (EM) algorithm is used to estimate parameters of the logistic-mixed model investigating risk factors of STIs. The interval-censored time until HIV infection is investigated using the Cox proportional hazards model which includes sexual network random effects in addition to the fixed effect. The parameters of this model were initially estimated using the EM algorithm. The main parameter estimation was carried out using the Gibbs sampler, a Bayesian Markov chain Monte Carlo (MCMC) method. 
The results show that migration is a risk factor of HIV /STI. The results further show that age, marital status, age at first sexual intercourse, sexual contact partners, lifetime partners and other biomedical factors are important determinants of HIV /STIs. The study shows that ignoring sexual network random effects in the analysis of HIV /STIs biases the results. The Gibbs sampler is shown to be a plausible alternative to the EM algorithm in the analysis of correlated interval-censored data. It allows full Bayesian inference, which provides a natural framework with which to integrate the uncertainty about parameters and incorporate heterogeneity between sub-groups, without the need to evaluate high-dimensional integrals.

text: Sexual network random effects models of migration and spread of HIV and other STIs in South Africa South Africa is experiencing an explosive epidemic of Human Immunodeficiency Virus (HIV) and of Sexually Transmitted Infections (STI)s. Furthermore, South Africa has extraordinarily high rates of migration. The predominant type of migration is the circular migration in which young men migrate to work in urban areas leaving their sexual partners behind, to whom they return periodically. Conditions of migration bring men into sexual contact with prostitutes and other women at high risk of HIV /STIs. In this way, migrant men form sexual networks, which become a critical bridge for transmitting HIV /STIs between rural and urban areas. 
The thesis investigates the determinants of HIV and those of STIs, taking into account the migration status and sexual network clustering effect in the data. The data investigated is from cohorts of migrant men from Hlabisa district working in urban areas, non-migrant partner(s) of migrant men residing in Hlabisa district, non-migrant men and their non-migrant partner(s) residing in Hlabisa district in northern KwaZulu-Natal, South Africa. Initially, the expectation-maximization (EM) algorithm is used to estimate parameters of the logistic-mixed model investigating risk factors of STIs. The interval-censored time until HIV infection is investigated using the Cox proportional hazards model which includes sexual network random effects in addition to the fixed effect. The parameters of this model were initially estimated using the EM algorithm. The main parameter estimation was carried out using the Gibbs sampler, a Bayesian Markov chain Monte Carlo (MCMC) method. 
The results show that migration is a risk factor of HIV /STI. The results further show that age, marital status, age at first sexual intercourse, sexual contact partners, lifetime partners and other biomedical factors are important determinants of HIV /STIs. The study shows that ignoring sexual network random effects in the analysis of HIV /STIs biases the results. The Gibbs sampler is shown to be a plausible alternative to the EM algorithm in the analysis of correlated interval-censored data. It allows full Bayesian inference, which provides a natural framework with which to integrate the uncertainty about parameters and incorporate heterogeneity between sub-groups, without the need to evaluate high-dimensional integrals.

year: 2004

title: The role of trust in an effective school culture

authors: Colville, Kathryn Adeline

subjects: Trust

abstract: Much work and research has been carried out on effective school cultures, accountability and relationships. Underlying all that happens in schools, is the notion of trust. But what do we understand about trust? Is the definition of trust consistent amongst everyone? How is trust defined? Is trust a valued or even an identified component of successful leadership? Does trust underpin all that we do and what, if any, are the commonalities of trust?

Central to this thesis is the notion that trust and trusting relationships play a pivotal role in the culture of a school and that without trust a school ceases to be as effective as it has the potential to be. The purpose of this study was to consider existing research and information and to attempt to establish a definition of trust, while identifying the place that trust is perceived to have in an effective school culture. While seeking to establish a baseline understanding of trust and peoples' perceptions of trust, it was also the purpose of this study to examine the dichotomy of trust and accountability. This looked at the challenge of building and maintaining trust while meeting individual and school accountability tasks. Consideration was also given to high-trust/low-trust situations and to whether they are actually the same situation, just seen through different eyes. 

The literature review examined what an effective school culture might look like and how trust impacts on this culture and, ultimately, on student learning. The literature review also defined trust and the skills, actions or emotions which contribute to trust and for whom these aspects of trust are a reality. The understanding that trust in the school situation is based on having common values and goals was evident in the literature. Trust was defined as being critical in the role of leadership and it is inherent in the way that principals act and lead and that it impacts greatly on the effectiveness of the relationships within a school and on student learning. 

Eight principals from a range of school sizes, with a gender balance of participants, took part in this research. All were involved in separate, semi-structured interviews, which provided the data for grounded theory analysis. Three distinct findings emerged from this process. These were the notion of what it means to be trustworthy, the role of the principal in extending trust and the dichotomy of trust. The results of this qualitative study suggested that the modelling of trust through daily actions and the empowering of staff were found to be important aspects in developing and maintaining trust within schools as was the competence, experience and knowledge of the principal.  Walking the talk  and valuing staff as individuals as well as professional members of the school organisation, were critical aspects to effective leadership. Prior experiences in which low trust was evident, informed the practice of these principals to develop philosophies of high trust. 

Within the final chapter in the Recommendations for Further Study which could add to current research by considering in more depth, specific relationships involving high trust. Six recommendations for further study were discussed in this final section. 
	
This study concludes that trust is significant in effective school cultures. It is a fragile emotion and action that can quickly be undermined and decimated and conversely, needs to be actively worked on to be maintained and developed to a high trust model. Being aware of and considering trust will assist principals and their colleagues to enhance effective school cultures, which will impact positively on student learning outcomes.

text: The role of trust in an effective school culture Much work and research has been carried out on effective school cultures, accountability and relationships. Underlying all that happens in schools, is the notion of trust. But what do we understand about trust? Is the definition of trust consistent amongst everyone? How is trust defined? Is trust a valued or even an identified component of successful leadership? Does trust underpin all that we do and what, if any, are the commonalities of trust?

Central to this thesis is the notion that trust and trusting relationships play a pivotal role in the culture of a school and that without trust a school ceases to be as effective as it has the potential to be. The purpose of this study was to consider existing research and information and to attempt to establish a definition of trust, while identifying the place that trust is perceived to have in an effective school culture. While seeking to establish a baseline understanding of trust and peoples' perceptions of trust, it was also the purpose of this study to examine the dichotomy of trust and accountability. This looked at the challenge of building and maintaining trust while meeting individual and school accountability tasks. Consideration was also given to high-trust/low-trust situations and to whether they are actually the same situation, just seen through different eyes. 

The literature review examined what an effective school culture might look like and how trust impacts on this culture and, ultimately, on student learning. The literature review also defined trust and the skills, actions or emotions which contribute to trust and for whom these aspects of trust are a reality. The understanding that trust in the school situation is based on having common values and goals was evident in the literature. Trust was defined as being critical in the role of leadership and it is inherent in the way that principals act and lead and that it impacts greatly on the effectiveness of the relationships within a school and on student learning. 

Eight principals from a range of school sizes, with a gender balance of participants, took part in this research. All were involved in separate, semi-structured interviews, which provided the data for grounded theory analysis. Three distinct findings emerged from this process. These were the notion of what it means to be trustworthy, the role of the principal in extending trust and the dichotomy of trust. The results of this qualitative study suggested that the modelling of trust through daily actions and the empowering of staff were found to be important aspects in developing and maintaining trust within schools as was the competence, experience and knowledge of the principal.  Walking the talk  and valuing staff as individuals as well as professional members of the school organisation, were critical aspects to effective leadership. Prior experiences in which low trust was evident, informed the practice of these principals to develop philosophies of high trust. 

Within the final chapter in the Recommendations for Further Study which could add to current research by considering in more depth, specific relationships involving high trust. Six recommendations for further study were discussed in this final section. 
	
This study concludes that trust is significant in effective school cultures. It is a fragile emotion and action that can quickly be undermined and decimated and conversely, needs to be actively worked on to be maintained and developed to a high trust model. Being aware of and considering trust will assist principals and their colleagues to enhance effective school cultures, which will impact positively on student learning outcomes.

year: 2007

title: Dating of recent low sea level and Maori rock carvings Ongari Point

authors: Schofield, J.C.

subjects: carving

abstract: A sea level of at least 1.5ft below the present one, and contemporaneous rock carvings have a radiocarbon date of 180±50 years B.P.

text: Dating of recent low sea level and Maori rock carvings Ongari Point A sea level of at least 1.5ft below the present one, and contemporaneous rock carvings have a radiocarbon date of 180±50 years B.P.

year: 1968