Asymmetric Ligands Derived from Carbohydrates

This thesis describes the incorporation of carbohydrate groups in thiourea, 1, or iminophosphorane, 2, ligands. Several carbohydrate acyl thioureas, 3, were synthesised from the reaction of protected and unprotected D‐glucosamine with acyl isothiocyanates, RCONCS. Internal hydrogen‐bonding forms a planar six‐membered ring, which locks the thiourea into an Z,E,Z‐anti conformation as shown by 1H NMR spectroscopy and confirmed by X‐ray structure determination of two examples. As neutral ligands to Rh(III), Rh(I), Ru(II), Pd(II), Pt(II) and Au(I) they bond through the sulfur atom with retention of the six‐membered ring and the Z,E,Z‐anti conformation. This was confirmed by two X‐ray structure determinations on Rh(III) and Pd(II) examples which also showed the new hydrogen‐bond formed by HN2 to a halide on the metal. Deprotonation of the ligands 3 with NaOAc gave anionic species which formed bidentate chelating complexes with metals. When attached to Rh(III), Ru(II) or with two thiourea bonding to Pd(II) it forms a four‐membered ring through the S and N2 atoms which retains the hydrogen‐bond. If Rh(I) or (C,Ndimethylbenzylamine‐ Pd) is used a six‐membered ring is formed through the S and O atoms which disrupts the hydrogen‐bond. This disruption of the hydrogenbond is apparent from the chemical shift of HN1. For examples where coordination led to a chiral metal complex (e.g. for Cp*RhCl(N,S‐thiourea)) NMR measurements showed that the natural chirality of the ligand did not provide any selectivity with equal proportions of the two diastereoisomers formed. Iminophosphoranes were produced by the reaction of protected sugar azides with phosphines via the Staudinger reaction. Cyclometalated complexes, 4, could not be formed directly which an X‐ray structure determination suggested was because of steric crowding of the nitrogen. An indirect transmetalation route was developed where the sugar azides were reacted with the mercurated diphosphine, Hg(2‐C₆H₄PPh₂)₂, and the resulting iminophosphoranes transmetalated with [NMe₄][AuCl₄] to produce cyclometalated Au(III) dichloride complexes. Two X‐ray structure determinations showed that the five‐membered metalocyclic ring was in an envelope conformation. The chlorides were labile and able to be displaced by PPh3 and thiosalicylic acid. A series of N‐sugar and N‐phenyl iminophosphorane Au(III) complexes were shown to catalyse the addition of 2‐methyl furan to methyl vinyl ketone

Light-output enhancement of InGaN light emitting diodes regrown on nanoporous distributed Bragg reflector substrates

Utilising our novel wafer-scale electrochemical porosification approach which proceeds through the top surface by means of nanoscale vertical etching pathways, we have prepared full 2 inch wafers containing alternating solid GaN and nanoporous GaN (NP-GaN) layers that form distributed Bragg reflectors (DBRs), and have regrown InGaN-based light emitting diode (LED) heterostructures on these wafers. The NP-GaN DBR wafer is epi-ready and exhibits a peak reflectance of 95% at 420 nm prior to growth of the LED heterostructure. We observe a 1.8× enhancement in peak intensity of LED electroluminescence from processed devices, and delayed onset of efficiency droop with increased injection current.This work was supported partly by the UK Engineering and Physical Sciences Research Council Grant No. EP/M011682/1 and the EPSRC Impact Acceleration Account Follow on Fund of the University of Cambridge

The Behaviour of Feral Pigs in North-West New South Wales and its Implications for the Epidemiology of Foot and Mouth Disease

A population of feral pigs was monitored by radio-telemetry at at Nocoleche Nature Reserve, in the semi-arid rangelands of north-west New South Wales, Australia to see how high temperature and spatio-temporal variability in food supply influenced habitat utilisation, home-range size, hourly distance moved and adult body weight. Radio-telemetry data was collected during seven intensive tracking sessions between November 1991 and July 1993. This period covered a period of drought and subsequent good seasons following heavy rains in late 1992. Food supply was indexed by estimating pasture biomass in four distinct habitats. These habitats were shrubland, riverine woodland, woodland and ephemeral swamp. Shelter from high temperatures was indexed by the amount of cover estimated from Daubenmire Cover Scale estimates for each habitat. Riverine woodland had the most cover ephemeral swamps the least cover and shrubland and woodland intermediate cover. Habitat utilisation was significantly influenced by pasture biomass in the shrubland and high temperature. Use of shrubland increased with increasing pasture biomass in shrubland and decreasing temperature. Use of riverine woodland increased with decreasing pasture biomass in woodland and increasing temperature. Use of woodland increased with decreasing pasture biomass in shrubland. Use of ephemeral swamps increased with decreasing temperature. Habitat utilisation by feral pigs therefore responds to changes in pasture biomass in shrubland while also responding to temperature with habitats with more cover used more during hot weather

Reintroduction of the Mala to Aboriginal land in the Tanami Desert, Northern Territory: A case study of the reintroduction process as a research and management tool

The Rufous Hare-wallaby or mala 'Lagorchestes hirsutus' is one of a suite of Australia's arid zone species which have suffered badly in the 200 years since European settlement. Within the Northern Territory alone at least 15 species of arid zone vascular plants and vertebrate animals have become extinct since settlement, and a further 75 species are classified as either endangered or vulnerable. From being one of the most abundant and widespread macropods of central Australia, the mala has declined to the point where it is now one of the rarest and most limited in its distribution. Wild populations of mala are currently known only from Bernier and Dorre Islands off the Western Australian coast. Reintroduction is therefore seen as one of the key elements of the recovery plan which has been prepared for the species

Utilisation of remnant Brigalow communities and adjacent pastures by the Black-striped Wallaby ('Macropus dorsalis')

This study arose out of the perceived problem that densities of the Black-striped Wallaby ('Macropus dorsalis') in fragmented patches of Brigalow ('Acacia harpophylla') vegetation were too high, causing detrimental impacts to their shelter habitat and competing with adjacent agricultural enterprises. The need for management of the Black-striped Wallaby has increased, with many primary producers within the Central Queensland (CQ) Brigalow Belt concerned that the species is a pest. Effective management of a species relies upon knowledge of its requirements and functioning. The objectives of this study were to determine the sheltering and dietary preferences of a Black-striped Wallaby population at supposed pest density. The various components of the study were undertaken in the remnant scrub and adjacent pasture paddocks on Brigalow Research Station, near Theodore, Central Queensland

Associations Between Koala Faecal Pellets and Trees at Dorrigo

Surveys are an important component of the legislative basis of protection and management of the koalas and their habitat in New South Wales. The search for faecal pellets provides a substantial source of information about the koala. At Dorrigo on the north coast of New South Wales, the forests are quite variable and have a composition that reflects a long and varied history of timber harvesting. Koalas appear to be widespread in the area, but at low population levels. The distribution and abundance of pellets are associated with tree density, size and species, and types of forest. Specifically, koala faecal pellets are associated with trees in less dense forests of 75-100 stems per hectare. Trees with pellet presence were not statistically associated with tree size, although trees with many pellets tended to be larger trees and medium-sized trees (60-90cm DBHOB) were the most preferred and important size to koalas. Tallowwood was the most preferred and important tree species to koalas

The effects of roads and their edges on the movement patterns and community composition of understorey rainforest birds in central Amazonia, Brazil

Understorey rainforest birds appear to be exceptionally sensitive to habitat fragmentation and disturbance. This study aims to examine the responses of understorey birds to roads and their edges in the lowland rainforests of central Amazonia. A two-year mist-net study captured 3681 birds at six study sites, along a small (30 - 40m wide) unpaved road. Bird movement across the road and bird composition within the forest was compared among three road-verge treatments: cleared, moderate regrowth and tall regrowth. Understorey birds varied considerably in their ability to cross a small road. Of the seven understorey guilds studied, the frugivorous and the edge/gap guilds appeared unaffected by the road at all sites. The five insectivorous guilds, however, demonstrated significantly fewer movements across a cleared road. While forest regrowth along road verges facilitated the movements of some insectivorous bird guilds, the solitary understorey birds still showed significant inhibition. Radio-tracking experiments of translocated birds were undertaken across a highway (45 - 65 m), a large farm clearing (250 m wide), and in continuous forest. Translocated birds returned to their home ranges across the highway and in continuous forest, but not across the large farm clearing. Edge effects, caused by the road clearing, were found to significantly alter the distribution of many understorey birds. Total bird captures declined significantly near forest edges irrespective of the type of habitat bordering the edge. Of all the bird guilds, the understorey insectivores showed the strongest pattern of edge avoidance. Captures of army-ant followers, solitary species, mixed-species flocks and terrestrial species declined dramatically near borders whereas edge/gap specialists increased. Frugivores, nectivores, and canopy and mid-storey insectivores did not vary as a function of edge distance. These thesis data were integrated with two other bird datasets from the BDFFP, to examine six species-traits which could predispose understorey birds to decline and possible extinction in forest fragments. Three significant traits were identified as predictors of post-fragmentation abundance: edge response, natural abundance, and foraging guild. The relative fragmentation response was also examined, and edge response was found to be a highly significant predictor explaining almost 50% of the variability in the data. The implications of this study for reserve design and bird conservation are discussed

Resource-Partitioning between Three Synoptic Thornbills (Acanthizidae : 'Acanthiza' Vigors and Horsfield)

Resource-partitioning among three syntopic species of thornbill ('Acanthiza pusilla', 'A. reguloides' and 'A. lineata') were studied at Wollomombi on the Northern Tablelands of New South Wales. All three species are mainly insectivorous and weigh about 7 grams. Abundance of arthropods, on foliage and grass, was measured monthly. There were great differences between summer peaks and winter troughs (> 10:1) and also between the 'normal' year of 1978/79 and the two drought years that followed (ca. 4:1). ... The three species were ecologically separated as they fed on different substrates and on different species of plants and at different heights. 'A. pusilla' foraged mainly on dense foliage of understorey shrubs, 'A. reguloides' foraged mainly on the ground or on the bark of trees and shrubs, and 'A. lineata' foraged mainly on the foliage of eucalypts. Foraging behaviour changed seasonally and with the size and composition of the group. For example 'A. reguloides' fed high in trees when in small groups but on the ground when in large groups. All three species foraged differently when in mixed-species flocks, even in areas where they were the nuclear species. ... The monthly overlap in foraging, between species, ranged from 3 to 43%. Overlaps were lowest when food was scarce but during prolonged periods of scarcity rose to comparatively high levels well before food increased. I believe that at such times either that a species is forced by intra-specific competition, in its specialised foraging role, to broaden its niche; or that overall scarcity is so severe that all species have to abandon specialisation and search for whatever prey is available, with a consequent increase in overlap