title: Fish and macroinvertebrates in lowland drainage canals with and without grass carp

authors: Hicks, Brendan J.

subjects: biology

abstract: Diploid grass carp (Ctenopharyngodon idella
L.) were introduced to a lowland Waikato drainage canal at an initial density of 40-80 kg ha -1(83-167 fish ha -1) to control aquatic macrophytes and improve water flow. A near-by canal was left without grass carp to act as an untreated control. After 7 months, macrophytes occupied 17% of the  water column in the treated canal compared to 78% in the untreated canal. Fish and macroinvertebrates in both canals were examined before and after the release of grass carp by sampling with replacement by fyke netting on seven occasions. Brown bullhead catfish (Ameiurus nebulosus (Lesueur)) and shortfinned eels (Anguilla australis Richardson) comprised most of the
resident fish biomass in both canals;  however, before grass carp stocking, eels were more abundant than catfish in the 
treated canal. There was no change in the abundance of resident fish after stocking, but young-of-the-year catfish had greater mortality and grew faster in the treated canal than in the untreated canal. Macroinvertebrates were primarily associated
with aquatic macrophytes. Grass carp reduced aquatic macrophyte abundance in the treated canal by about 80%, which by inference reduced the abundance of associated macroinvertebrates, but there was no  observed impact of grass carp stocking on the resident fish assemblage. We examined
the relationship between head width and fish length, and from this determined that 70% of the grass carp could have escaped through the downstream retention screen. Despite
this possibility, grass carp remained in the canal and effectively controlled aquatic macrophytes for 18 months.

text: Fish and macroinvertebrates in lowland drainage canals with and without grass carp Diploid grass carp (Ctenopharyngodon idella
L.) were introduced to a lowland Waikato drainage canal at an initial density of 40-80 kg ha -1(83-167 fish ha -1) to control aquatic macrophytes and improve water flow. A near-by canal was left without grass carp to act as an untreated control. After 7 months, macrophytes occupied 17% of the  water column in the treated canal compared to 78% in the untreated canal. Fish and macroinvertebrates in both canals were examined before and after the release of grass carp by sampling with replacement by fyke netting on seven occasions. Brown bullhead catfish (Ameiurus nebulosus (Lesueur)) and shortfinned eels (Anguilla australis Richardson) comprised most of the
resident fish biomass in both canals;  however, before grass carp stocking, eels were more abundant than catfish in the 
treated canal. There was no change in the abundance of resident fish after stocking, but young-of-the-year catfish had greater mortality and grew faster in the treated canal than in the untreated canal. Macroinvertebrates were primarily associated
with aquatic macrophytes. Grass carp reduced aquatic macrophyte abundance in the treated canal by about 80%, which by inference reduced the abundance of associated macroinvertebrates, but there was no  observed impact of grass carp stocking on the resident fish assemblage. We examined
the relationship between head width and fish length, and from this determined that 70% of the grass carp could have escaped through the downstream retention screen. Despite
this possibility, grass carp remained in the canal and effectively controlled aquatic macrophytes for 18 months.

year: 2006-07

title: Theoretical Investigation of NMDA Effect on the Cerebral Cortex

authors: AL Saidi, Waleed Hamdan Khalfan

subjects: NMDA  Effect

abstract: This thesis examines the dynamical behaviour of incorporating NMDA (an excitatory
neurotransmitter) for the electrodynamic model of the cerebral cortex. The
model used is the mean-field model developed by Steyn-Ross et al. (2005) which
describes the behaviour of the cortex in terms of parameters averaged over spatially
localised populations. The behaviour of the model is determined by the four control
parameters: inhibitory effect li, subcortical drive s, and NMDA neurotransmitter
e ect set by an excitatory factor le and the magnesium concentration C. Adopting
this model could give a better understanding of the cortex functionality and the
anaesthetic mechanism.
The model predicts that there are either one or three stationary states available to
the cortex. We identify two of these with highly activated state and a quiescent
state and focus on the transition between the two. Theoretical stability predictions
(eigenvalue analysis) verified by a numerical simulation show that the system is
unstable between the two Hopf bifurcations. In addition, in the stable region the
steady states remains stable under a small perturbation, while in the unstable region
either a transition between states or a limit cycle (oscillation) occurs depending on
the position of the steady state.

text: Theoretical Investigation of NMDA Effect on the Cerebral Cortex This thesis examines the dynamical behaviour of incorporating NMDA (an excitatory
neurotransmitter) for the electrodynamic model of the cerebral cortex. The
model used is the mean-field model developed by Steyn-Ross et al. (2005) which
describes the behaviour of the cortex in terms of parameters averaged over spatially
localised populations. The behaviour of the model is determined by the four control
parameters: inhibitory effect li, subcortical drive s, and NMDA neurotransmitter
e ect set by an excitatory factor le and the magnesium concentration C. Adopting
this model could give a better understanding of the cortex functionality and the
anaesthetic mechanism.
The model predicts that there are either one or three stationary states available to
the cortex. We identify two of these with highly activated state and a quiescent
state and focus on the transition between the two. Theoretical stability predictions
(eigenvalue analysis) verified by a numerical simulation show that the system is
unstable between the two Hopf bifurcations. In addition, in the stable region the
steady states remains stable under a small perturbation, while in the unstable region
either a transition between states or a limit cycle (oscillation) occurs depending on
the position of the steady state.

year: 2008

title: Street health: Practitioner service provision for Māori homeless people in Auckland

authors: Nikora, Linda Waimarie

abstract: Homelessness is more than a transient crisis. While access to housing might solve the needs of some, research has shown that the needs of homeless people are much more complex and more a symptom of systematic structural inequalities than an unanticipated emergency (Hopper, 1998). As in other countries, the homeless population in New Zealand is made up of a diverse population of men, women and intersex groups of various ages, sexualities and ethnic backgrounds. Māori are over-represented among this population due to ongoing processes of colonisation and socioeconomic exclusion (Groot et al., 2011). When compared with domiciled citizens, homeless people are more likely to experience a raft of illnesses and unmet health needs, violence, a sense of insecurity, exclusion and fear, and are more likely to commit sui- cide (Hodgetts et al., 2007). Homeless people often experience diverse ill- nesses including asthma, heart disease, diabetes, hepatitis, renal disease, dermatological conditions, malnutrition, oral disease, depression, schizo- phrenia, substance misuse and broken bones (Ellison-Loschmann & Pearce, 2006; Joly et al., 2011; Moore et al., 2007).

text: Street health: Practitioner service provision for Māori homeless people in Auckland Homelessness is more than a transient crisis. While access to housing might solve the needs of some, research has shown that the needs of homeless people are much more complex and more a symptom of systematic structural inequalities than an unanticipated emergency (Hopper, 1998). As in other countries, the homeless population in New Zealand is made up of a diverse population of men, women and intersex groups of various ages, sexualities and ethnic backgrounds. Māori are over-represented among this population due to ongoing processes of colonisation and socioeconomic exclusion (Groot et al., 2011). When compared with domiciled citizens, homeless people are more likely to experience a raft of illnesses and unmet health needs, violence, a sense of insecurity, exclusion and fear, and are more likely to commit sui- cide (Hodgetts et al., 2007). Homeless people often experience diverse ill- nesses including asthma, heart disease, diabetes, hepatitis, renal disease, dermatological conditions, malnutrition, oral disease, depression, schizo- phrenia, substance misuse and broken bones (Ellison-Loschmann & Pearce, 2006; Joly et al., 2011; Moore et al., 2007).

year: 2016