title: LSB - Live and Safe B: Alternative semantics for Event B

authors: Reeves, Steve

subjects: process refinement

abstract: We define two lifted, total relation semantics for Event B machines: Safe B for safety-only properties and Live B for liveness properties. The usual Event B proof obligations, Safe, are sufficient to establish Safe B refinement. Satisfying Safe plus a simple additional proof obligation ACT REF is sufficient to establish Live B refinement. The use of lifted, total relations both prevents the ambiguity of the unlifted relational semantics and prevents operations being clairvoyant.

text: LSB - Live and Safe B: Alternative semantics for Event B We define two lifted, total relation semantics for Event B machines: Safe B for safety-only properties and Live B for liveness properties. The usual Event B proof obligations, Safe, are sufficient to establish Safe B refinement. Satisfying Safe plus a simple additional proof obligation ACT REF is sufficient to establish Live B refinement. The use of lifted, total relations both prevents the ambiguity of the unlifted relational semantics and prevents operations being clairvoyant.

year: 2006-07-01

title: A validation study of phycocyanin sensors for monitoring cyanobacteria in cultures and field samples

authors: Hodges, Caroline Marie

subjects: Phycocycanin

abstract: Cyanobacteria are photosynthetic prokaryotes present in almost all terrestrial and aquatic environments. Under favourable conditions of high nutrient inputs, high water temperature and adequate light, they can rapidly multiply and form blooms. Cyanobacterial blooms are harmful to aquatic processes as they reduce the amount of irradiance within the water column and some have the ability to produce toxins which pose a risk to human and animal health. Cyanobacterial blooms are becoming prevalent worldwide as a result of increased anthropogenic influences. To enable accurate risk assessment of drinking water reservoirs, water bodies for recreational use and to assist in the understanding of bloom dynamics, cyanobacterial biomass must be quantified. Traditionally this was done via grab sampling, the use of microscopy and measurements of chlorophyll-a concentration using spectrophotometry. These methods do not allow samples to be collected and analysed at a frequency that provides meaningful spatial and temporal resolution. Additionally, they can be time consuming, expensive and require taxonomic expertise. 

Measurements of chlorophyll-a concentration can provide an estimate of overall phytoplankton biomass but cannot differentiate between eukaryotic cells and cyanobacteria. However, the fluorescent pigment phycocyanin is specific to cyanobacteria and has a unique fluorescence signature which can enable the estimation of cyanobacteria biomass. Methods to detect phycocyanin fluorescence have been integrated into handheld sensors which can be used as a proxy for estimation of cyanobacterial biomass in situ. However, robust validation of these sensors is rarely undertaken. Previous use of fluorescence sensors suggest that there may be multiple sources of interference of the optical signal. The aim of this study was to assess the performance of commercially-available phycocyanin sensors using a combination of culture-based laboratory experiments and a field investigation.

The laboratory studies showed strong linear relationships between phycocyanin and chlorophyll-a fluorescence from sensors and cyanobacterial biovolume obtained by microscopy. This was observed across a range of cell concentrations for solitary (e.g. Microcystis sp.) and filamentous species (e.g. Aphanizomenon sp.). However this linear relationship was not observed with colonial and some filamentous cyanobacteria (Microcystis sp., Nodularia spumigena, and Dolichospermum sp.). Further investigation suggested that the morphology of densely aggregated species inhibited the penetration of light into the colony, resulting in an underestimation of phycocyanin. These results highlight a potential limitation for the use of phycocyanin sensors in situ as colonial and filamentous cyanobacteria are often observed. Other potential limitations for the use of phycocyanin sensors include natural variations in light intensity which can cause photobleaching; reducing fluorescence, as well as increased variability of phycocyanin fluorescence with changes in temperature.  

Field experiments during this study showed that extracellular phycocyanin from lysed cells could in some instances account for more than 20% of the total phycocyanin fluorescence. The field study also showed a strong linear relationship between measurements of phycocyanin fluorescence and cyanobacterial biovolume. However measurements of chlorophyll-a were poorly correlated to cyanobacterial biovolume. The results from the field experiments indicate that phycocyanin sensors may be a valuable tool to monitor cyanobacteria biomass in the field. Collectively, this data highlights the potential for the use of phycocyanin sensors to obtain high frequency data on cyanobacterial biomass, while also demonstrating limitations for their use in situ. Further study is needed to determine more definitively the effects of these potential limitations on phycocyanin measurements and which supplementary parameters could be measured in order for the data collected to be more robust and informative.

text: A validation study of phycocyanin sensors for monitoring cyanobacteria in cultures and field samples Cyanobacteria are photosynthetic prokaryotes present in almost all terrestrial and aquatic environments. Under favourable conditions of high nutrient inputs, high water temperature and adequate light, they can rapidly multiply and form blooms. Cyanobacterial blooms are harmful to aquatic processes as they reduce the amount of irradiance within the water column and some have the ability to produce toxins which pose a risk to human and animal health. Cyanobacterial blooms are becoming prevalent worldwide as a result of increased anthropogenic influences. To enable accurate risk assessment of drinking water reservoirs, water bodies for recreational use and to assist in the understanding of bloom dynamics, cyanobacterial biomass must be quantified. Traditionally this was done via grab sampling, the use of microscopy and measurements of chlorophyll-a concentration using spectrophotometry. These methods do not allow samples to be collected and analysed at a frequency that provides meaningful spatial and temporal resolution. Additionally, they can be time consuming, expensive and require taxonomic expertise. 

Measurements of chlorophyll-a concentration can provide an estimate of overall phytoplankton biomass but cannot differentiate between eukaryotic cells and cyanobacteria. However, the fluorescent pigment phycocyanin is specific to cyanobacteria and has a unique fluorescence signature which can enable the estimation of cyanobacteria biomass. Methods to detect phycocyanin fluorescence have been integrated into handheld sensors which can be used as a proxy for estimation of cyanobacterial biomass in situ. However, robust validation of these sensors is rarely undertaken. Previous use of fluorescence sensors suggest that there may be multiple sources of interference of the optical signal. The aim of this study was to assess the performance of commercially-available phycocyanin sensors using a combination of culture-based laboratory experiments and a field investigation.

The laboratory studies showed strong linear relationships between phycocyanin and chlorophyll-a fluorescence from sensors and cyanobacterial biovolume obtained by microscopy. This was observed across a range of cell concentrations for solitary (e.g. Microcystis sp.) and filamentous species (e.g. Aphanizomenon sp.). However this linear relationship was not observed with colonial and some filamentous cyanobacteria (Microcystis sp., Nodularia spumigena, and Dolichospermum sp.). Further investigation suggested that the morphology of densely aggregated species inhibited the penetration of light into the colony, resulting in an underestimation of phycocyanin. These results highlight a potential limitation for the use of phycocyanin sensors in situ as colonial and filamentous cyanobacteria are often observed. Other potential limitations for the use of phycocyanin sensors include natural variations in light intensity which can cause photobleaching; reducing fluorescence, as well as increased variability of phycocyanin fluorescence with changes in temperature.  

Field experiments during this study showed that extracellular phycocyanin from lysed cells could in some instances account for more than 20% of the total phycocyanin fluorescence. The field study also showed a strong linear relationship between measurements of phycocyanin fluorescence and cyanobacterial biovolume. However measurements of chlorophyll-a were poorly correlated to cyanobacterial biovolume. The results from the field experiments indicate that phycocyanin sensors may be a valuable tool to monitor cyanobacteria biomass in the field. Collectively, this data highlights the potential for the use of phycocyanin sensors to obtain high frequency data on cyanobacterial biomass, while also demonstrating limitations for their use in situ. Further study is needed to determine more definitively the effects of these potential limitations on phycocyanin measurements and which supplementary parameters could be measured in order for the data collected to be more robust and informative.

year: 2016

title: Young Maori males experiences in a secondary school context as sporting, academic and cultural identities.

authors: Porteous, Erin

subjects: Male Maori

abstract: This research focused on the journey of male Māori through secondary school and the effect on their identities in terms of sport, culture and academia. The two key areas of focus were how the culture of the school, including cultural stereotypes, impacts on male Māori learner self-concept, and whether the effect of creating an all Māori boys form class has resulted in an increased sense of belonging and engagement. 
The research was conducted as a case study underpinned by an interpretive methodology, using a focus group interview. The group was made up of five boys, chosen from a newly formed all boys’ Year 11 Māori form class. The boys were selected in conjunction with their form teacher and the schools Kaitiaki, in order to reflect a range of sporting, academic and cultural levels. 
The research findings found that although the boys view of their experiences in school seemed positive overall, they described common incidences and reactions to racial discrimination. The exposure to embedded racial stereotypes and behaviours caused them to create their own solutions, often through threatening violence or aggressive reactions. It appears that when young male Māori are more closely connected to Māori culture, they are more likely they are to create these responses. 
Teachers remain integral to the engagement and belonging of a young male Māori in secondary school. In support of the findings from Kia Eke Panuku (2013), this study found that male Māori require positive relationships with their teachers to engage in the subject and school in a general sense. Relationships based on ako and manaakitanga are key to these students viewing their experiences in school as successful.
Another finding showed the importance of sport and physical activity to young male Māori, though success in this area has been a limiting factor in contributing to overall success in secondary school. The placing of male Māori as a ‘physical being’ (Hokowhitu, 2003a; Hokowhitu, 2003b; Hokowhitu, 2004) creates spaces where Māori can be successful, such as practical based subjects like physical education. This success is perceived as acceptable yet often isolates them away from success in other areas (Erueti & Palmer, 2014), feeding into the stereotype itself.
The success of the all boys’ Māori form class was scrutinised by this study, and found the intended outcomes had not necessarily been met. The overall impact was that the boys had been grouped with a Māori form teacher and the intentions of additional support had been overlooked due to time pressures and deficit thinking in terms of capabilities of the class members.  For the Māori boys in this study, the challenges of overcome historical cultural stereotypes added to the challenge of succeeding at secondary school. The expectation that they walk successfully between the realms of Māori and pākehā to achieve in the current education system coupled with the feeling they needed to act ‘pākehā’ in order to achieve is particularly disturbing. The inequity for them in denying part of their identity seems a hefty price to pay for educational success.
This study highlights the need for schools, communities and individual teachers to recognise these racial and systemic inequities and work tirelessly to develop strategies to eliminate them, in order to create to take a giant step towards equity for all New Zealanders within education.

text: Young Maori males experiences in a secondary school context as sporting, academic and cultural identities. This research focused on the journey of male Māori through secondary school and the effect on their identities in terms of sport, culture and academia. The two key areas of focus were how the culture of the school, including cultural stereotypes, impacts on male Māori learner self-concept, and whether the effect of creating an all Māori boys form class has resulted in an increased sense of belonging and engagement. 
The research was conducted as a case study underpinned by an interpretive methodology, using a focus group interview. The group was made up of five boys, chosen from a newly formed all boys’ Year 11 Māori form class. The boys were selected in conjunction with their form teacher and the schools Kaitiaki, in order to reflect a range of sporting, academic and cultural levels. 
The research findings found that although the boys view of their experiences in school seemed positive overall, they described common incidences and reactions to racial discrimination. The exposure to embedded racial stereotypes and behaviours caused them to create their own solutions, often through threatening violence or aggressive reactions. It appears that when young male Māori are more closely connected to Māori culture, they are more likely they are to create these responses. 
Teachers remain integral to the engagement and belonging of a young male Māori in secondary school. In support of the findings from Kia Eke Panuku (2013), this study found that male Māori require positive relationships with their teachers to engage in the subject and school in a general sense. Relationships based on ako and manaakitanga are key to these students viewing their experiences in school as successful.
Another finding showed the importance of sport and physical activity to young male Māori, though success in this area has been a limiting factor in contributing to overall success in secondary school. The placing of male Māori as a ‘physical being’ (Hokowhitu, 2003a; Hokowhitu, 2003b; Hokowhitu, 2004) creates spaces where Māori can be successful, such as practical based subjects like physical education. This success is perceived as acceptable yet often isolates them away from success in other areas (Erueti & Palmer, 2014), feeding into the stereotype itself.
The success of the all boys’ Māori form class was scrutinised by this study, and found the intended outcomes had not necessarily been met. The overall impact was that the boys had been grouped with a Māori form teacher and the intentions of additional support had been overlooked due to time pressures and deficit thinking in terms of capabilities of the class members.  For the Māori boys in this study, the challenges of overcome historical cultural stereotypes added to the challenge of succeeding at secondary school. The expectation that they walk successfully between the realms of Māori and pākehā to achieve in the current education system coupled with the feeling they needed to act ‘pākehā’ in order to achieve is particularly disturbing. The inequity for them in denying part of their identity seems a hefty price to pay for educational success.
This study highlights the need for schools, communities and individual teachers to recognise these racial and systemic inequities and work tirelessly to develop strategies to eliminate them, in order to create to take a giant step towards equity for all New Zealanders within education.

year: 2016