title: New insights into the role of pH and aeration in the bacterial production of calcium carbonate (CaCO₃)

authors: Seifan, Mostafa

subjects: Science & Technology

abstract: Over recent years, the implementation of microbially produced calcium carbonate (CaCO₃) in different industrial and environmental applications has become an alternative for conventional approaches to induce CaCO₃ precipitation. However, there are many factors affecting the biomineralization of CaCO₃, which may restrict its application. In this study, we investigated the effects of pH and aeration as the main two influential parameters on bacterial precipitation of CaCO₃. The results showed that the aeration had a significant effect on bacterial growth and its rise from 0.5 to 4.5 SLPM could produce 4.2 times higher CaCO₃ precipitation. The increase of pH to 12 resulted in 6.3-fold increase in CaCO₃ precipitation as compared to uncontrolled-pH fermentation. Morphological characterization showed that the pH is an effective parameter on CaCO₃ morphology. Calcite was found to be the predominant precipitate during aeration-controlled fermentations, while vaterite was mainly produced at lower pH (up to 10) over controlled-pH fermentations. Further increase in pH resulted in a morphological transition, and vaterite transformed to calcite at the pH ranges between 10 and 12.

text: New insights into the role of pH and aeration in the bacterial production of calcium carbonate (CaCO₃) Over recent years, the implementation of microbially produced calcium carbonate (CaCO₃) in different industrial and environmental applications has become an alternative for conventional approaches to induce CaCO₃ precipitation. However, there are many factors affecting the biomineralization of CaCO₃, which may restrict its application. In this study, we investigated the effects of pH and aeration as the main two influential parameters on bacterial precipitation of CaCO₃. The results showed that the aeration had a significant effect on bacterial growth and its rise from 0.5 to 4.5 SLPM could produce 4.2 times higher CaCO₃ precipitation. The increase of pH to 12 resulted in 6.3-fold increase in CaCO₃ precipitation as compared to uncontrolled-pH fermentation. Morphological characterization showed that the pH is an effective parameter on CaCO₃ morphology. Calcite was found to be the predominant precipitate during aeration-controlled fermentations, while vaterite was mainly produced at lower pH (up to 10) over controlled-pH fermentations. Further increase in pH resulted in a morphological transition, and vaterite transformed to calcite at the pH ranges between 10 and 12.

year: 2017

title: An algorithmic approach to OpenFlow ruleset transformation

authors: Sanger, Richard

abstract: In an ideal development cycle for an OpenFlow application, a developer designs a pipeline to suit their application's needs and installs rules to that pipeline. Their application will run on any OpenFlow switch, whether software or hardware based. A network operator deploying this application would assess their network's requirements and purchase OpenFlow hardware to meet these requirements; such as bandwidth, port density, and flow table size. In reality, this level of interoperability does not exist as many OpenFlow switches are built on a fixed-function pipeline. Fixed-function pipelines limit the matches and actions available to rules depending on the table, but in doing so make more efficient use of expensive hardware resources such as TCAM.

This thesis investigates improving OpenFlow device interoperability by developing a method to rewrite existing rulesets to new complex fixed-function pipelines. Additionally, this thesis developed the tools to assess and verify the interoperability and equivalence of OpenFlow rulesets and pipelines. 

This thesis developed a library and tools for working with descriptions of fixed-function pipelines, specifically, the Table Type Pattern description. This library provides a method to check if an existing ruleset is compatible with a new pipeline. Additionally, this thesis designed and implemented a pragmatic approach to compare if the forwarding behaviour of two OpenFlow 1.3 rulesets is equivalent. Equivalence checking provides a tool to verify that an OpenFlow application rewritten to program a new pipeline maintains the correct forwarding behaviour.

Finally, this thesis investigates the problem of algorithmically rewriting an existing OpenFlow ruleset, programmed by an existing application, to fit a different fixed-function pipeline. Solving this problem allows an OpenFlow application to be written once and run on any OpenFlow switch. This research aimed to solve this problem in a comprehensive manner that did not rely on the target pipeline supporting features such as OpenFlow metadata. This thesis developed and implemented a general method to convert an OpenFlow 1.3 to a complex constrained fixed-function.

text: An algorithmic approach to OpenFlow ruleset transformation In an ideal development cycle for an OpenFlow application, a developer designs a pipeline to suit their application's needs and installs rules to that pipeline. Their application will run on any OpenFlow switch, whether software or hardware based. A network operator deploying this application would assess their network's requirements and purchase OpenFlow hardware to meet these requirements; such as bandwidth, port density, and flow table size. In reality, this level of interoperability does not exist as many OpenFlow switches are built on a fixed-function pipeline. Fixed-function pipelines limit the matches and actions available to rules depending on the table, but in doing so make more efficient use of expensive hardware resources such as TCAM.

This thesis investigates improving OpenFlow device interoperability by developing a method to rewrite existing rulesets to new complex fixed-function pipelines. Additionally, this thesis developed the tools to assess and verify the interoperability and equivalence of OpenFlow rulesets and pipelines. 

This thesis developed a library and tools for working with descriptions of fixed-function pipelines, specifically, the Table Type Pattern description. This library provides a method to check if an existing ruleset is compatible with a new pipeline. Additionally, this thesis designed and implemented a pragmatic approach to compare if the forwarding behaviour of two OpenFlow 1.3 rulesets is equivalent. Equivalence checking provides a tool to verify that an OpenFlow application rewritten to program a new pipeline maintains the correct forwarding behaviour.

Finally, this thesis investigates the problem of algorithmically rewriting an existing OpenFlow ruleset, programmed by an existing application, to fit a different fixed-function pipeline. Solving this problem allows an OpenFlow application to be written once and run on any OpenFlow switch. This research aimed to solve this problem in a comprehensive manner that did not rely on the target pipeline supporting features such as OpenFlow metadata. This thesis developed and implemented a general method to convert an OpenFlow 1.3 to a complex constrained fixed-function.

year: 2020

title: Indigenous people in Aotearoa New Zealand are overrepresented in cannabis convictions

authors: Rapana, Wetini

subjects: Cannabis

abstract: Background: Previous work has demonstrated that cannabis laws have had a disproportionate impact on Māori, the Indigenous people of Aotearoa New Zealand. In 2019, the New Zealand Government amended cannabis laws, providing police with the power to determine whether a therapeutic or health-centred approach would be more beneficial than a conviction. In the current study, we use population level data to assess whether this law change has ameliorated the bias in cannabis convictions for Māori. Methods: Data were drawn from the Integrated Data Infrastructure (IDI), a large government database hosted by Aotearoa New Zealand’s national statistics office. In the IDI, we selected individuals who (1) were between 18 and 65, (2) were Māori or Pākehā (New Zealanders of European descent) and, (3) had any cannabis charges that proceeded to the courts. Results: Māori ethnicity was a significant predictor of the odds of receiving a cannabis conviction for Māori males (Odds: 1.56), with a marginally significant effect for Māori females (Odds: 1.57). Further, for Māori, there was no reduction in the number of cannabis charges before vs. after the amendment to cannabis laws. Conclusion: The current study demonstrates that the bias in cannabis convictions for Māori remain. Given this, the New Zealand Government must follow other countries around the world and move forward on cannabis law reform.

text: Indigenous people in Aotearoa New Zealand are overrepresented in cannabis convictions Background: Previous work has demonstrated that cannabis laws have had a disproportionate impact on Māori, the Indigenous people of Aotearoa New Zealand. In 2019, the New Zealand Government amended cannabis laws, providing police with the power to determine whether a therapeutic or health-centred approach would be more beneficial than a conviction. In the current study, we use population level data to assess whether this law change has ameliorated the bias in cannabis convictions for Māori. Methods: Data were drawn from the Integrated Data Infrastructure (IDI), a large government database hosted by Aotearoa New Zealand’s national statistics office. In the IDI, we selected individuals who (1) were between 18 and 65, (2) were Māori or Pākehā (New Zealanders of European descent) and, (3) had any cannabis charges that proceeded to the courts. Results: Māori ethnicity was a significant predictor of the odds of receiving a cannabis conviction for Māori males (Odds: 1.56), with a marginally significant effect for Māori females (Odds: 1.57). Further, for Māori, there was no reduction in the number of cannabis charges before vs. after the amendment to cannabis laws. Conclusion: The current study demonstrates that the bias in cannabis convictions for Māori remain. Given this, the New Zealand Government must follow other countries around the world and move forward on cannabis law reform.

year: 2022