title: Efficient algorithms for conditional independence inference

authors: Bouckaert, Remco R.

subjects: computer science

abstract: The topic of the paper is computer testing of (probabilistic) conditional independence (CI) implications by an algebraic method of structural imsets. The basic idea is to transform (sets of) CI statements into certain integral vectors and to verify by a computer the corresponding algebraic relation between the vectors, called the independence implication. We interpret the previous methods for computer testing of this implication from the point of view of polyhedral geometry. However, the main contribution of the paper is a new method, based on linear programming (LP). The new method overcomes the limitation of former methods to the number of involved variables. We recall/describe the theoretical basis for all four methods involved in our computational experiments, whose aim was to compare the efficiency of the algorithms. The experiments show that the LP method is clearly the fastest one. As an example of possible application of such algorithms we show that testing inclusion of Bayesian network structures or whether a CI statement is encoded in an acyclic directed graph can be done by the algebraic method.

text: Efficient algorithms for conditional independence inference The topic of the paper is computer testing of (probabilistic) conditional independence (CI) implications by an algebraic method of structural imsets. The basic idea is to transform (sets of) CI statements into certain integral vectors and to verify by a computer the corresponding algebraic relation between the vectors, called the independence implication. We interpret the previous methods for computer testing of this implication from the point of view of polyhedral geometry. However, the main contribution of the paper is a new method, based on linear programming (LP). The new method overcomes the limitation of former methods to the number of involved variables. We recall/describe the theoretical basis for all four methods involved in our computational experiments, whose aim was to compare the efficiency of the algorithms. The experiments show that the LP method is clearly the fastest one. As an example of possible application of such algorithms we show that testing inclusion of Bayesian network structures or whether a CI statement is encoded in an acyclic directed graph can be done by the algebraic method.

year: 2010

title: Do ship rats display predatory behaviour towards house mice?

authors: Bridgman, Lucy Jade

subjects: black rat

abstract: Control operations for invasive ship rats, Rattus rattus, in New Zealand forests are often followed by increased house mouse, Mus musculus, detections suggesting rats suppress mice. A potential mechanism is intraguild predation, either by interference competition or as simple predatory behaviour. If aggression by rats towards mice is mainly competitive, it should include threat and display features associated with, for example, intraspecific fighting. If predatory, it should lack these features and be associated with feeding. In the first of two captive experiments we observed interactions between paired, live rodents, either side of a wire-mesh screen, and found that most rats were aggressive to mice. This aggression lacked threat and display characteristics typical of encounters with conspecifics and was rarely reciprocated by mice. In a second experiment, euthanized mice were drawn by a line through cages occupied by rats fed either a restricted or unrestricted diet. Rats of both groups attacked and restrained the euthanized mice, and all rats that interacted with the mice ate at least part of them, although food-restricted rats tended to eat more. As the aggressive response of ship rats towards mice lacked threat and display features and was related to feeding, we conclude that it resembles predatory behaviour. Our findings provide a better understanding of the interactions between ship rats and house mice, which hinder their management where they coexist as damaging invaders. However, further research is required to determine whether the results of our captive experiments are consistent with wild rat behaviour.

text: Do ship rats display predatory behaviour towards house mice? Control operations for invasive ship rats, Rattus rattus, in New Zealand forests are often followed by increased house mouse, Mus musculus, detections suggesting rats suppress mice. A potential mechanism is intraguild predation, either by interference competition or as simple predatory behaviour. If aggression by rats towards mice is mainly competitive, it should include threat and display features associated with, for example, intraspecific fighting. If predatory, it should lack these features and be associated with feeding. In the first of two captive experiments we observed interactions between paired, live rodents, either side of a wire-mesh screen, and found that most rats were aggressive to mice. This aggression lacked threat and display characteristics typical of encounters with conspecifics and was rarely reciprocated by mice. In a second experiment, euthanized mice were drawn by a line through cages occupied by rats fed either a restricted or unrestricted diet. Rats of both groups attacked and restrained the euthanized mice, and all rats that interacted with the mice ate at least part of them, although food-restricted rats tended to eat more. As the aggressive response of ship rats towards mice lacked threat and display features and was related to feeding, we conclude that it resembles predatory behaviour. Our findings provide a better understanding of the interactions between ship rats and house mice, which hinder their management where they coexist as damaging invaders. However, further research is required to determine whether the results of our captive experiments are consistent with wild rat behaviour.

year: 2013

title: Brown bodies, white coats: Postcolonialism, Māori women, and science

authors: McKinley, Elizabeth

abstract: This project investigates the historical construction of 'Māori woman' and the constitution of the subjectivities of Maori women scientists today. The central question that is raised by the thesis is 'Do discourses of 'race' and gender found in Enlightenment science at the time of Aotearoa New Zealand's colonization continue to affect the contemporary subjectivity of Māori women scientists, and if so, how?' I have used literary historical techniques and feminist narrative interviews to collect the research data. Deconstruction, and its technique of 'double reading', has been applied through out the thesis to both the literary historical texts (imperial archives) and the transcripts of the interviews. I have argued that a poststructuralist view of the 'splitting the subject' to enable multiple positions must be read alongside the postcolonial view of a contemporary 'colonized subject' of an already 'split' subjectivity. 
This thesis is divided into two sections. Section A investigates Māori women as the objects of science. I argue that in Aotearoa New Zealand journeys of discovery and colonization were also scientific journeys that brought 'Māori woman' under the intellectual control of the emerging 'scientific' academy. At the same time, drawing on the 'imperial archives', I show that stereotypical signifiers are incorporated within scientific discourses and shape the fictions that these texts represent. In Section B I draw on open-ended interviews with 16 Māori women scientists who were asked to discuss their identity in relation to their schooling and workplaces. I explore the conditions by which the subject 'Māori women scientist' emerges and how the Maori women experience these conditions in relation to how they see themselves. I conclude by arguing that the identity of 'Māori woman scientist' appears to be 'impossible fiction' due to the fragmented nature of the sign - 'Māori, 'woman' and 'scientist' - that can be 'traced' to the historical construction of the signs.

text: Brown bodies, white coats: Postcolonialism, Māori women, and science This project investigates the historical construction of 'Māori woman' and the constitution of the subjectivities of Maori women scientists today. The central question that is raised by the thesis is 'Do discourses of 'race' and gender found in Enlightenment science at the time of Aotearoa New Zealand's colonization continue to affect the contemporary subjectivity of Māori women scientists, and if so, how?' I have used literary historical techniques and feminist narrative interviews to collect the research data. Deconstruction, and its technique of 'double reading', has been applied through out the thesis to both the literary historical texts (imperial archives) and the transcripts of the interviews. I have argued that a poststructuralist view of the 'splitting the subject' to enable multiple positions must be read alongside the postcolonial view of a contemporary 'colonized subject' of an already 'split' subjectivity. 
This thesis is divided into two sections. Section A investigates Māori women as the objects of science. I argue that in Aotearoa New Zealand journeys of discovery and colonization were also scientific journeys that brought 'Māori woman' under the intellectual control of the emerging 'scientific' academy. At the same time, drawing on the 'imperial archives', I show that stereotypical signifiers are incorporated within scientific discourses and shape the fictions that these texts represent. In Section B I draw on open-ended interviews with 16 Māori women scientists who were asked to discuss their identity in relation to their schooling and workplaces. I explore the conditions by which the subject 'Māori women scientist' emerges and how the Maori women experience these conditions in relation to how they see themselves. I conclude by arguing that the identity of 'Māori woman scientist' appears to be 'impossible fiction' due to the fragmented nature of the sign - 'Māori, 'woman' and 'scientist' - that can be 'traced' to the historical construction of the signs.

year: 2003