title: Mass-loading and parallel magnetized shocks

authors: Zank, Gary P.

subjects: MHD

abstract: Recent observations at comets Giacobini-Zinner and Halley suggest that simple non-reacting gas dynamics or MHD is an inappropriate description for the bow shock. The thickness of the observed (sub)shock implies that mass-loading is an important dynamical process within the shock itself, thereby requiring that the Rankine-Hugoniot conditions possess source terms. This leads to shocks with properties similar to those of combustion shocks. We consider parallel magnetized shocks subjected to mass-loading, describe some properties which distinguish them from classical MHD parallel shocks, and establish the existence of a new kind of MHD compound shock. These results will be of importance both to observations and numerical simulations of the comet-solar wind interaction.

text: Mass-loading and parallel magnetized shocks Recent observations at comets Giacobini-Zinner and Halley suggest that simple non-reacting gas dynamics or MHD is an inappropriate description for the bow shock. The thickness of the observed (sub)shock implies that mass-loading is an important dynamical process within the shock itself, thereby requiring that the Rankine-Hugoniot conditions possess source terms. This leads to shocks with properties similar to those of combustion shocks. We consider parallel magnetized shocks subjected to mass-loading, describe some properties which distinguish them from classical MHD parallel shocks, and establish the existence of a new kind of MHD compound shock. These results will be of importance both to observations and numerical simulations of the comet-solar wind interaction.

year: 1991

title: Investigation of Microcystin Processing, Production and Export by Microcystis sp.

authors: Rogers, Shelley

subjects: microcystin

abstract: During this study, the effect of different processing methods on the microcystin quota (microcystins per cell) was investigated.  Microcystins from two Microcystis strains and one Planktothrix strain were quantified using liquid chromatography-mass spectrometry (LC-MS) after processing via; (1) direct freezing (no prior cell concentration) and extraction by freeze-thaw cycles, (2) cell concentration by centrifugation and extraction in methanol and (3) cell concentration by filtration and extraction in methanol. Microcystin quotas were lower for samples concentrated by filtration compared with the other two methods.  

In order to distinguish between extracellular microcystins actively exported from cells and those that are present as a result of cell lysis, a comparative microcystin export (CME) assay was developed using LC-MS to compare the proportion of extracellular microcystins with the proportion of extracellular non-ribosomal peptide which does not get actively exported. A culture-based experiment using the CME assay demonstrated the utility of this method and indicated that export from one of the Microcystis strains had occurred. With further validation experiments, the CME assay has the potential to be a valuable new tool for determining the occurrence of microcystin export. 

An in situ experiment was carried out in Lake Rotorua, Kaikoura, New Zealand, using mesocosms to study the effect of Microcystis sp. cell density on microcystin production, while measuring a wide array of abiotic parameters (temperature, light intensity, pH, dissolved oxygen and nutrients). Lake water was added to ‘control’ mesocosms in which cells were concentrated to different levels and added to ‘medium cell addition’ and ‘high cell addition’ mesocosms. The microcystin quota remained relatively constant throughout the study, despite induced changes in cell density and associated environmental parameters. These results indicate that cell density is not the only factor responsible for increased microcystin synthesis and that further investigation into the effect of stress inducing abiotic parameters such as pH and dissolved oxygen concentration may be required.

text: Investigation of Microcystin Processing, Production and Export by Microcystis sp. During this study, the effect of different processing methods on the microcystin quota (microcystins per cell) was investigated.  Microcystins from two Microcystis strains and one Planktothrix strain were quantified using liquid chromatography-mass spectrometry (LC-MS) after processing via; (1) direct freezing (no prior cell concentration) and extraction by freeze-thaw cycles, (2) cell concentration by centrifugation and extraction in methanol and (3) cell concentration by filtration and extraction in methanol. Microcystin quotas were lower for samples concentrated by filtration compared with the other two methods.  

In order to distinguish between extracellular microcystins actively exported from cells and those that are present as a result of cell lysis, a comparative microcystin export (CME) assay was developed using LC-MS to compare the proportion of extracellular microcystins with the proportion of extracellular non-ribosomal peptide which does not get actively exported. A culture-based experiment using the CME assay demonstrated the utility of this method and indicated that export from one of the Microcystis strains had occurred. With further validation experiments, the CME assay has the potential to be a valuable new tool for determining the occurrence of microcystin export. 

An in situ experiment was carried out in Lake Rotorua, Kaikoura, New Zealand, using mesocosms to study the effect of Microcystis sp. cell density on microcystin production, while measuring a wide array of abiotic parameters (temperature, light intensity, pH, dissolved oxygen and nutrients). Lake water was added to ‘control’ mesocosms in which cells were concentrated to different levels and added to ‘medium cell addition’ and ‘high cell addition’ mesocosms. The microcystin quota remained relatively constant throughout the study, despite induced changes in cell density and associated environmental parameters. These results indicate that cell density is not the only factor responsible for increased microcystin synthesis and that further investigation into the effect of stress inducing abiotic parameters such as pH and dissolved oxygen concentration may be required.

year: 2014

title: Examining the effects of Ki-o-Rahi on the development of fundamental movement skills by children in Aotearoa New Zealand

authors: Daveta, Wiliame

subjects: fundamental movement skills

abstract: Children with poor fundamental movement skills might have challenges when engaging in activities that require specific skills to help them perform effectively. Development of those skills through targeted training has the potential to build the foundation for fundamental movement skills. This study examined whether Ki-o-Rahi can enhance learning fundamental movement skills (FMS) and cognitive and social skills in Aotearoa New Zealand children. A quasi-experimental pre-post design was conducted over 8 weeks with 86 primary school children from five separate classes that were allocated to treatment conditions via cluster sampling: two classes to the intervention group, two to the control group, and one to the legend-only control group. The intervention group learned the legend and played Ki-o-Rahi over 8 sessions, whereas the control groups continued with their regular physical activities, but only one of the control groups learned the legend. FMS were measured using the Test of Gross Motor Development—Third Edition (TGMD-3) and the Motor Assessment Battery for Children (MABC-2). Cognitive skills were measured using the Head-Toes-Knees-Shoulders test (HTKS), forward and backward digit span, and forward and backward corsi block. Researchers measured social skills using the Early Childhood Social Relationship with Peers (ECSRP) teacher-proxy questionnaire. The results demonstrated that the intervention and control group gained improvements in the FMS and social skills but not cognitive skills. The legend-only group showed no significant changes. The findings suggest that Ki-o-rahi can contribute to developing FMS, cognitive, and social skills in Aotearoa New Zealand children. Future research should consider extending the duration of the study to assess long-term effects and include a larger cohort of Pacific or Māori children to explore potential benefits of Ki-o-Rahi in greater depth.

text: Examining the effects of Ki-o-Rahi on the development of fundamental movement skills by children in Aotearoa New Zealand Children with poor fundamental movement skills might have challenges when engaging in activities that require specific skills to help them perform effectively. Development of those skills through targeted training has the potential to build the foundation for fundamental movement skills. This study examined whether Ki-o-Rahi can enhance learning fundamental movement skills (FMS) and cognitive and social skills in Aotearoa New Zealand children. A quasi-experimental pre-post design was conducted over 8 weeks with 86 primary school children from five separate classes that were allocated to treatment conditions via cluster sampling: two classes to the intervention group, two to the control group, and one to the legend-only control group. The intervention group learned the legend and played Ki-o-Rahi over 8 sessions, whereas the control groups continued with their regular physical activities, but only one of the control groups learned the legend. FMS were measured using the Test of Gross Motor Development—Third Edition (TGMD-3) and the Motor Assessment Battery for Children (MABC-2). Cognitive skills were measured using the Head-Toes-Knees-Shoulders test (HTKS), forward and backward digit span, and forward and backward corsi block. Researchers measured social skills using the Early Childhood Social Relationship with Peers (ECSRP) teacher-proxy questionnaire. The results demonstrated that the intervention and control group gained improvements in the FMS and social skills but not cognitive skills. The legend-only group showed no significant changes. The findings suggest that Ki-o-rahi can contribute to developing FMS, cognitive, and social skills in Aotearoa New Zealand children. Future research should consider extending the duration of the study to assess long-term effects and include a larger cohort of Pacific or Māori children to explore potential benefits of Ki-o-Rahi in greater depth.

year: 2024