title: Cross-helically forced and decaying hydromagnetic turbulence

authors: Brandenburg, Axel

subjects: Science & Technology

abstract: We study the evolution of kinetic and magnetic energy spectra in magnetohydrodynamic flows in the presence of strong cross helicity. For forced turbulence, we find a weak inverse transfer of kinetic energy toward the smallest wavenumber. This is plausibly explained by the finiteness of scale separation between the injection wavenumber and the smallest wavenumber of the domain, which here is a factor of 15. In the decaying case, there is a slight increase at the smallest wavenumber, which is probably explained by the dominance of kinetic energy over magnetic energy at the smallest wavenumbers. Within a range of wavenumbers covering almost an order of magnitude, the decay is purely exponential, which is argued to be a consequence of a suppression of nonlinearity due to the presence of strong cross helicity.

text: Cross-helically forced and decaying hydromagnetic turbulence We study the evolution of kinetic and magnetic energy spectra in magnetohydrodynamic flows in the presence of strong cross helicity. For forced turbulence, we find a weak inverse transfer of kinetic energy toward the smallest wavenumber. This is plausibly explained by the finiteness of scale separation between the injection wavenumber and the smallest wavenumber of the domain, which here is a factor of 15. In the decaying case, there is a slight increase at the smallest wavenumber, which is probably explained by the dominance of kinetic energy over magnetic energy at the smallest wavenumbers. Within a range of wavenumbers covering almost an order of magnitude, the decay is purely exponential, which is argued to be a consequence of a suppression of nonlinearity due to the presence of strong cross helicity.

year: 2018

title: Antimicrobial Peptides in Jawed and Jawless Vertebrates

authors: Gibbons, Olivia Robyn

subjects: Antimicrobial Peptides

abstract: Antimicrobial peptides (AMPs) are a major part of the innate immune defence system which shows a broad spectrum of activity, defending the host against invading microbes. The aim of this work was to identify the AMPs present in yellowtail kingfish (Seriola lalandi) and pouched lamprey (Geotria australis) and use molecular techniques to fully sequence their cDNA and quantify their expression in adult individuals.

Using bioinformatic approaches candidate AMP genes were ascertained from available S. lalandi and G. australis RNA-seq transcriptomic databases, obtained from various tissues. Selected AMPs were chosen to have their full cDNA sequence amplified using RACE-PCR, which were then cloned and sequenced. Complete cDNA sequences were obtained for S. lalandi hepcidin and moronecidin, whereas attempts to complete the G. australis defensin-like cDNA were unsuccessful. Comparison of the S. lalandi hepcidin and moronecidin protein sequences with proteins already characterised in other fish showed good homology and conservation of important features. In addition, specific primers were designed to examine the expression levels of S. lalandi hepcidin and moronecidin in gill, liver or spleens of three fish. Analysis showed hepcidin expression to be highest in liver tissues, whereas moronecidin expression was highest in the gills and spleens.

This study provides a comprehensive overview of the AMP genes present in S. lalandi and G. australis and some initial characterisation of S. lalandi hepcidin and moronecidin, which will permit the development of future research applications. Overall, characterising AMP genes in jawed and jawless vertebrates is vital for economical and successful fish farming, while also providing possible therapeutic benefits associated with AMP research in biomedicine and disease in wild fish stocks.

text: Antimicrobial Peptides in Jawed and Jawless Vertebrates Antimicrobial peptides (AMPs) are a major part of the innate immune defence system which shows a broad spectrum of activity, defending the host against invading microbes. The aim of this work was to identify the AMPs present in yellowtail kingfish (Seriola lalandi) and pouched lamprey (Geotria australis) and use molecular techniques to fully sequence their cDNA and quantify their expression in adult individuals.

Using bioinformatic approaches candidate AMP genes were ascertained from available S. lalandi and G. australis RNA-seq transcriptomic databases, obtained from various tissues. Selected AMPs were chosen to have their full cDNA sequence amplified using RACE-PCR, which were then cloned and sequenced. Complete cDNA sequences were obtained for S. lalandi hepcidin and moronecidin, whereas attempts to complete the G. australis defensin-like cDNA were unsuccessful. Comparison of the S. lalandi hepcidin and moronecidin protein sequences with proteins already characterised in other fish showed good homology and conservation of important features. In addition, specific primers were designed to examine the expression levels of S. lalandi hepcidin and moronecidin in gill, liver or spleens of three fish. Analysis showed hepcidin expression to be highest in liver tissues, whereas moronecidin expression was highest in the gills and spleens.

This study provides a comprehensive overview of the AMP genes present in S. lalandi and G. australis and some initial characterisation of S. lalandi hepcidin and moronecidin, which will permit the development of future research applications. Overall, characterising AMP genes in jawed and jawless vertebrates is vital for economical and successful fish farming, while also providing possible therapeutic benefits associated with AMP research in biomedicine and disease in wild fish stocks.

year: 2016

title: Assessment of fish populations in Lake Horowhenua, Levin

authors: Tempero, Grant Wayne

subjects: Lake Horowhenua

abstract: Lake Horowhenua (Waipunahau) is of substantial historical, cultural and recreational value to the people of the Horowhenua region. However, water quality and biodiversity within the lake has been in decline for a number of years. As part of lake restoration efforts by Horizons Regional Council and the Lake Horowhenua Trustees, a survey of fish species in Lake Horowhenua was conducted by the University of Waikato using boat electrofishing and fyke netting. A lake restoration plan had previously identified invasive fish species such as koi carp (Cyprinus carpio) and European perch (Perca fluviatilis) as being potential barriers to rehabilitation of the lake. The purpose of this survey was to determine the abundance and diversity of fish species within the lake and to ascertain if pest fish species were present at biomasses high enough to be negatively impacting on lake ecology. Recommendations would then be made as to the potential methods and necessity for pest fish removal.

text: Assessment of fish populations in Lake Horowhenua, Levin Lake Horowhenua (Waipunahau) is of substantial historical, cultural and recreational value to the people of the Horowhenua region. However, water quality and biodiversity within the lake has been in decline for a number of years. As part of lake restoration efforts by Horizons Regional Council and the Lake Horowhenua Trustees, a survey of fish species in Lake Horowhenua was conducted by the University of Waikato using boat electrofishing and fyke netting. A lake restoration plan had previously identified invasive fish species such as koi carp (Cyprinus carpio) and European perch (Perca fluviatilis) as being potential barriers to rehabilitation of the lake. The purpose of this survey was to determine the abundance and diversity of fish species within the lake and to ascertain if pest fish species were present at biomasses high enough to be negatively impacting on lake ecology. Recommendations would then be made as to the potential methods and necessity for pest fish removal.

year: 2013