title: Scaling up semi-supervised learning: An efficient and effective LLGC variant

authors: Pfahringer, Bernhard

subjects: computer science

abstract: Domains like text classification can easily supply large amounts of unlabeled data, but labeling itself is expensive. Semi- supervised learning tries to exploit this abundance of unlabeled training data to improve classification. Unfortunately most of the theoretically well-founded algorithms that have been described in recent years are cubic or worse in the total number of both labeled and unlabeled training examples. In this paper we apply modifications to the standard LLGC algorithm to improve efficiency to a point where we can handle datasets with hundreds of thousands of training data. The modifications are priming of the unlabeled data, and most importantly, sparsification of the similarity matrix. We report promising results on large text classification problems.

text: Scaling up semi-supervised learning: An efficient and effective LLGC variant Domains like text classification can easily supply large amounts of unlabeled data, but labeling itself is expensive. Semi- supervised learning tries to exploit this abundance of unlabeled training data to improve classification. Unfortunately most of the theoretically well-founded algorithms that have been described in recent years are cubic or worse in the total number of both labeled and unlabeled training examples. In this paper we apply modifications to the standard LLGC algorithm to improve efficiency to a point where we can handle datasets with hundreds of thousands of training data. The modifications are priming of the unlabeled data, and most importantly, sparsification of the similarity matrix. We report promising results on large text classification problems.

year: 2007

title: The molecular basis of the effect of temperature on enzyme activity

authors: Daniel, Roy M.

subjects: adaptation

abstract: Experimental data show that the effect of temperature on enzymes cannot be adequately explained in terms of a two-state model based on increases in activity and denaturation. The Equilibrium Model provides a quantitative explanation of enzyme thermal behaviour under reaction conditions by introducing an inactive (but not denatured) intermediate in rapid equilibrium with the active form. The temperature midpoint (Teq) of the rapid equilibration between the two forms is related to the growth temperature of the organism, and the enthalpy of the equilibrium (ΔHeq) to its ability to function over various temperature ranges. In the present study, we show that the difference between the active and inactive forms is at the enzyme active site. The results reveal an apparently universal mechanism, independent of enzyme reaction or structure, based at or near the active site, by which enzymes lose activity as temperature rises, as opposed to denaturation which is global. Results show that activity losses below Teq may lead to significant errors in the determination of ΔG*cat made on the basis of the twostate (‘Classical’) model, and the measured kcat will then not be a true indication of an enzyme’s catalytic power. Overall, the results provide a molecular rationale for observations that the active site tends to be more flexible than the enzyme as a whole, and that activity losses precede denaturation, and provide a general explanation in molecular terms for the effect of temperature on enzyme activity.

text: The molecular basis of the effect of temperature on enzyme activity Experimental data show that the effect of temperature on enzymes cannot be adequately explained in terms of a two-state model based on increases in activity and denaturation. The Equilibrium Model provides a quantitative explanation of enzyme thermal behaviour under reaction conditions by introducing an inactive (but not denatured) intermediate in rapid equilibrium with the active form. The temperature midpoint (Teq) of the rapid equilibration between the two forms is related to the growth temperature of the organism, and the enthalpy of the equilibrium (ΔHeq) to its ability to function over various temperature ranges. In the present study, we show that the difference between the active and inactive forms is at the enzyme active site. The results reveal an apparently universal mechanism, independent of enzyme reaction or structure, based at or near the active site, by which enzymes lose activity as temperature rises, as opposed to denaturation which is global. Results show that activity losses below Teq may lead to significant errors in the determination of ΔG*cat made on the basis of the twostate (‘Classical’) model, and the measured kcat will then not be a true indication of an enzyme’s catalytic power. Overall, the results provide a molecular rationale for observations that the active site tends to be more flexible than the enzyme as a whole, and that activity losses precede denaturation, and provide a general explanation in molecular terms for the effect of temperature on enzyme activity.

year: 2010

title: Ngā Whanaketanga: Minimising contradictions and maximising opportunities for teacher learning.

authors: Hohepa, Margie Kahukura

subjects: Māori medium teacher professional development

abstract: In 2010 the assessment of student progress and achievement against National Standards became mandatory in English medium schooling in Aotearoa New Zealand. In that same year information gathering and revision work was carried out on the then draft Whanaketanga, developed in 2009. The Whanaketanga are deemed to be the equivalent to National Standards for classrooms implementing Te Marautanga o Aotearoa, the curriculum for immersion Māori medium settings. The information gathering and revision work was carried out in readiness for mandatory implementation of the Whanaketanga in 2011. The work also provided important opportunities for Māori medium teacher professional learning and development. The introduction of National Standards has been controversial. The development of Whanaketanga has also been controversial and challenging in nature. The first half of this paper provides an overview of Whanaketanga development and the challenges its developers worked hard to address. The second part discusses implications for Māori medium teacher professional learning and development, drawn from findings from research case studies of the information gathering and revision work.

text: Ngā Whanaketanga: Minimising contradictions and maximising opportunities for teacher learning. In 2010 the assessment of student progress and achievement against National Standards became mandatory in English medium schooling in Aotearoa New Zealand. In that same year information gathering and revision work was carried out on the then draft Whanaketanga, developed in 2009. The Whanaketanga are deemed to be the equivalent to National Standards for classrooms implementing Te Marautanga o Aotearoa, the curriculum for immersion Māori medium settings. The information gathering and revision work was carried out in readiness for mandatory implementation of the Whanaketanga in 2011. The work also provided important opportunities for Māori medium teacher professional learning and development. The introduction of National Standards has been controversial. The development of Whanaketanga has also been controversial and challenging in nature. The first half of this paper provides an overview of Whanaketanga development and the challenges its developers worked hard to address. The second part discusses implications for Māori medium teacher professional learning and development, drawn from findings from research case studies of the information gathering and revision work.

year: 2012