title: Review: Marine natural products

authors: Blunt, John W.

subjects: review

abstract: This review covers the literature published in 2009 for marine natural products, with 857 citations (588 for the period January to December 2009) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1011 for 2009), together with the relevant biological activities, source organisms and country of origin. Biosynthetic studies, first syntheses, and syntheses that lead to the revision of structures or stereochemistries, have been included.

text: Review: Marine natural products This review covers the literature published in 2009 for marine natural products, with 857 citations (588 for the period January to December 2009) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1011 for 2009), together with the relevant biological activities, source organisms and country of origin. Biosynthetic studies, first syntheses, and syntheses that lead to the revision of structures or stereochemistries, have been included.

year: 2011

title: Interacting Turing-Hopf Instabilities Drive Symmetry-Breaking Transitions in a Mean-Field Model of the Cortex: A Mechanism for the Slow Oscillation

authors: Steyn-Ross, Moira L.

subjects: biological physics

abstract: Electrical recordings of brain activity during the transition from wake to anesthetic coma show temporal and spectral alterations that are correlated with gross changes in the underlying brain state. Entry into anesthetic unconsciousness is signposted by the emergence of large, slow oscillations of electrical activity (≲1  Hz) similar to the slow waves observed in natural sleep. Here we present a two-dimensional mean-field model of the cortex in which slow spatiotemporal oscillations arise spontaneously through a Turing (spatial) symmetry-breaking bifurcation that is modulated by a Hopf (temporal) instability. In our model, populations of neurons are densely interlinked by chemical synapses, and by interneuronal gap junctions represented as an inhibitory diffusive coupling. To demonstrate cortical behavior over a wide range of distinct brain states, we explore model dynamics in the vicinity of a general-anesthetic-induced transition from “wake” to “coma.” In this region, the system is poised at a codimension-2 point where competing Turing and Hopf instabilities coexist. We model anesthesia as a moderate reduction in inhibitory diffusion, paired with an increase in inhibitory postsynaptic response, producing a coma state that is characterized by emergent low-frequency oscillations whose dynamics is chaotic in time and space. The effect of long-range axonal white-matter connectivity is probed with the inclusion of a single idealized point-to-point connection. We find that the additional excitation from the long-range connection can provoke seizurelike bursts of cortical activity when inhibitory diffusion is weak, but has little impact on an active cortex. Our proposed dynamic mechanism for the origin of anesthetic slow waves complements—and contrasts with—conventional explanations that require cyclic modulation of ion-channel conductances. We postulate that a similar bifurcation mechanism might underpin the slow waves of natural sleep and comment on the possible consequences of chaotic dynamics for memory processing and learning.

text: Interacting Turing-Hopf Instabilities Drive Symmetry-Breaking Transitions in a Mean-Field Model of the Cortex: A Mechanism for the Slow Oscillation Electrical recordings of brain activity during the transition from wake to anesthetic coma show temporal and spectral alterations that are correlated with gross changes in the underlying brain state. Entry into anesthetic unconsciousness is signposted by the emergence of large, slow oscillations of electrical activity (≲1  Hz) similar to the slow waves observed in natural sleep. Here we present a two-dimensional mean-field model of the cortex in which slow spatiotemporal oscillations arise spontaneously through a Turing (spatial) symmetry-breaking bifurcation that is modulated by a Hopf (temporal) instability. In our model, populations of neurons are densely interlinked by chemical synapses, and by interneuronal gap junctions represented as an inhibitory diffusive coupling. To demonstrate cortical behavior over a wide range of distinct brain states, we explore model dynamics in the vicinity of a general-anesthetic-induced transition from “wake” to “coma.” In this region, the system is poised at a codimension-2 point where competing Turing and Hopf instabilities coexist. We model anesthesia as a moderate reduction in inhibitory diffusion, paired with an increase in inhibitory postsynaptic response, producing a coma state that is characterized by emergent low-frequency oscillations whose dynamics is chaotic in time and space. The effect of long-range axonal white-matter connectivity is probed with the inclusion of a single idealized point-to-point connection. We find that the additional excitation from the long-range connection can provoke seizurelike bursts of cortical activity when inhibitory diffusion is weak, but has little impact on an active cortex. Our proposed dynamic mechanism for the origin of anesthetic slow waves complements—and contrasts with—conventional explanations that require cyclic modulation of ion-channel conductances. We postulate that a similar bifurcation mechanism might underpin the slow waves of natural sleep and comment on the possible consequences of chaotic dynamics for memory processing and learning.

year: 2013

title: Contextualising Māori writing: a study of prose fiction written in English by Witi Ihimaera, Patricia Grace, Keri Hulme and Alan Duff

authors: Calvert, Julia Helen

abstract: All prose fiction written in English by Māori is political on one level or another. The authors considered in this thesis, Witi Ihimaera, Patricia Grace, Keri Hulme and Alan Duff, choose to identify as Māori, but for each writer exactly what this entails implies something different. The diverse range of Māori characters represented in their work illustrates the heterogeneity of contemporary Māori identity. Whilst bearing in mind that there is no fixed Māori identity, this thesis proposes that all fiction written in English by Māori is motivated by a belief that Māori are a disadvantaged group within New Zealand society. 

Three of the four writers, Ihimaera, Grace and Hulme, write against a background of colonisation. Their fiction confronts grievances based on perceived injustices committed against Māori in the past by European colonists and is concerned with the restoration of Māori rights pertaining to land, language, identity and political voice. While all three engage with these issues in their fiction, this thesis specifically considers the way in which Ihimaera treats the theme of land, Grace focuses on issues of education and Hulme explores Māori mythology.

Alan Duff stands apart from the other three writers in his belief that colonisation is not to blame for contemporary Māori disadvantage. Rather, Duff considers the situation to be the result of inherent flaws within Māori society. Through his often didactic writing he proposes that improved Māori socioeconomic levels can only be achieved through a radical structural and economic re-evaluation of Māori culture.

This thesis contextualises the work of the four authors and explores the ways in which their fiction engages with historical and contemporary issues of “race relations” and cultural identity in New Zealand. A sociological approach has been applied to the texts. This approach derives from the Māori writers’ own insistent reading of contemporary Māori identity as the product of historical encounter between Māori and Pākehā. The authors work in a dialectical relationship to previous Pākehā representations of Māori in literature, are historically revisionist, and are frequently adversarial. 

Despite the differences in personal and political perspectives held by the authors, their fictions share a common goal in their search for Māori pathways to empowerment. This thesis argues that prose fiction written in English by Māori writers contributes to the political activism of the Māori people and helps to foster an environment in which new perspectives on Māori culture and bicultural relations can be articulated.

text: Contextualising Māori writing: a study of prose fiction written in English by Witi Ihimaera, Patricia Grace, Keri Hulme and Alan Duff All prose fiction written in English by Māori is political on one level or another. The authors considered in this thesis, Witi Ihimaera, Patricia Grace, Keri Hulme and Alan Duff, choose to identify as Māori, but for each writer exactly what this entails implies something different. The diverse range of Māori characters represented in their work illustrates the heterogeneity of contemporary Māori identity. Whilst bearing in mind that there is no fixed Māori identity, this thesis proposes that all fiction written in English by Māori is motivated by a belief that Māori are a disadvantaged group within New Zealand society. 

Three of the four writers, Ihimaera, Grace and Hulme, write against a background of colonisation. Their fiction confronts grievances based on perceived injustices committed against Māori in the past by European colonists and is concerned with the restoration of Māori rights pertaining to land, language, identity and political voice. While all three engage with these issues in their fiction, this thesis specifically considers the way in which Ihimaera treats the theme of land, Grace focuses on issues of education and Hulme explores Māori mythology.

Alan Duff stands apart from the other three writers in his belief that colonisation is not to blame for contemporary Māori disadvantage. Rather, Duff considers the situation to be the result of inherent flaws within Māori society. Through his often didactic writing he proposes that improved Māori socioeconomic levels can only be achieved through a radical structural and economic re-evaluation of Māori culture.

This thesis contextualises the work of the four authors and explores the ways in which their fiction engages with historical and contemporary issues of “race relations” and cultural identity in New Zealand. A sociological approach has been applied to the texts. This approach derives from the Māori writers’ own insistent reading of contemporary Māori identity as the product of historical encounter between Māori and Pākehā. The authors work in a dialectical relationship to previous Pākehā representations of Māori in literature, are historically revisionist, and are frequently adversarial. 

Despite the differences in personal and political perspectives held by the authors, their fictions share a common goal in their search for Māori pathways to empowerment. This thesis argues that prose fiction written in English by Māori writers contributes to the political activism of the Māori people and helps to foster an environment in which new perspectives on Māori culture and bicultural relations can be articulated.

year: 2002