23,922 results for Thesis

  • The order of premodifiers in English nominal phrases

    Feist, James Murray (2008)

    Doctoral thesis
    The University of Auckland Library

    The research reported in this thesis sought an explanation for the order of premodifiers in English nominal phrases. It aimed to establish what validity there is in the quite divergent earlier explanations, to find any other valid forms of explanation that might exist, and to integrate them all. The method was to make a wide survey of as many varieties of current English as possible, by observation; to then analyse the order at all levels (semantics, syntax, and so on); and to check the accuracy of the results against the 100-million-word British National Corpus. From that research, the thesis asserts that parts of most past approaches can be integrated into a comprehensive explanation; and that there is a new and important element of the full explanation, namely that of words' semantic structure, which is the combination of types and dimensions of meaning that make up the sense of each premodifier. Other new elements in this treatment of the subject are analysis of long groups of premodifiers (up to 10 words), consideration of why premodifiers regularly occur in different positions in the order, and explanation from the historical development of premodifier order. After an introductory chapter and a survey of the relevant literature, the thesis argues that the explanation of premodifier order in English nominal phrases is as follows. There are four positions for premodifiers, as in "your (1) actual (2) tinny (3) round (4) percussion instrument" [i.e. a tambourine] (chapter 3). The regular, unmarked order (illustrated in the phrase just quoted) has several elements of explanation: primarily, the semantic structure (chapter 4); secondarily, the syntactic structure (chapter 5). In a second type of order (when two or more words occur in one position), stylistic considerations control the order, not grammatical ones (chapter 7). In a third type of order, a marked one, a premodifier may be put in a position different from the position that the word's usual semantic structure would require, changing its meaning and stylistic effect (chapter 8). Some features of all three types of order are to be explained partly by their historical development - for example, the existence of borderline uses (chapter 9). There are some supporting explanations, from discourse structure and psycholinguistics, for example (chapter 10). The relevance of the previous chapters to wider issues, such as grammaticalisation, is discussed (chapter 11); and conclusions are drawn (chapter 12).

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  • Purification, biochemical and somatogenic characterisation of ovine placental lactogen

    Singh, Kuljeet (1992)

    Doctoral thesis
    The University of Auckland Library

    Ovine placental lactogen (oPL) is secreted by the placenta into both the fetal and maternal compartments. Its biological function(s) during pregnancy and the mechanisms involved are still unclear. A purification procedure was developed for oPL from sheep placental cotyledons of late gestation. Four procedures were attempted to obtain homogeneous oPL. Recoveries of oPL and total protein were measured throughout the several procedures using a specific oPL RIA and the Bradford protein estimation respectively. The third and fourth procedures resulted in homogeneous oPL and a partial amino acid sequence was obtained from the fourth procedure. In the successful procedures, the placental tissue was extracted with 0.1 M ammonium bicarbonate pH 8.5. A pH precipitation of the soluble fraction was performed, followed by 60% saturation with ammonium sulphate. Further separation steps involved chromatogaphic procedures. Carboxymethylcellulose (CM32) cation exchange was performed batchwise at pH 5.6. Subsequently chromatofocusing was performed to elute proteins in order of their isoelectric points. This was carried out using a pH gadient of 0.9 to 6.0. The final chromatographic step was reverse-phase high performance liquid chromatography (RP-HPLC) using a C4 column. To obtain homogeneous oPL in the third procedure, the partially purified oPL was subjected to SDS polyacrylamide gel electrophoresis and the separated proteins were transferred to nitrocellulose membrane. The homogeneous oPL was eluted from the membrane, however, sequencing was unsuccessful. It was assumed that the N terminal of oPL was blocked. Homogeneous oPL was obtained in the fourth procedure by electrophoretic elution from the Hunkapiller gel system performed at 4°C. The oPL was digested with trypsin, the fragments were separated by RP-HPLC chromatography and two peptides were sequenced. Peptide 1: F D E Q Y G Q G I Peptide 2: Y I N C H T Several strategies were attempted to provide more homogeneous oPL to enable more sequencing. The partially purified oPL fractions from each of these attempts were pooled and electrophoresed on an SDS polyacrylamide gel. The section of acrylamide containing the oPL band was homogenised and a trypsin digest was performed. The digested oPL was separated from the gel pieces, filtered through a Sep-Pak filter and the fragments were separated by RP-HPLC. The yield of oPL was low, but sufficient homogeneous oPL was obtained to provide a partial amino acid sequence from tryptic peptides. A further two peptides provided sequences. Peptide 3: (L) A G E M V N R F D E Q Y G Q G I Peptide 4: (L) Q P G K C Q I P L Q S L F Collaborators from Genentech Inc (San Francisco USA) used partially purified oPL produced from the present study and also obtained homogeneous oPL (Colosi et al., 1989). Complementary DNA clones of oPL were isolated and expressed in mammalian cells by recombinant DNA techniques (Colosi et al., 1989). These clones were sequenced, demonstrating that the full sequence of oPL consists of 198 amino acids preceded by a 38 amino acid sequence signal. Recombinant oPL was generated by Colosi et al. (1989) which provided sufficient material to perform physiological studies in vivo. The somatogenic effects of recombinant oPL were investigated in the growth hormone (GH) deficient dwarf rat and compared to identical doses of recombinant bovine GH (bGH) in 3 independent studies. Both oPL and bGH treatments resulted in an increase (p<0.05) hepatic GH receptor mRNA compared to saline controls, but oPL treatment had no effect. Thus, oPL is a potent anabolic and lipolytic agent in the dwarf rat, exerting greater somatogenic effects on some parameters than bGH. The studies in this thesis have described biochemical and biological characterisitics of oPL. The amino acid sequence of oPL is more closely related to prolactin (PRL) than to GH (Colosi et al., 1989). However, oPL has potent somatogenic activities in the GH deficient dwarf rat. Our data suggest differences in receptor binding and effects on GH receptor and IGFBP-3 expression with these two treatments, raising the possibility of actions through different pathways or differential effects at the GH receptor level. These results do not fully resolve whether GH and PRL exert all effects through a single receptor or whether there is a separate PL receptor.

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  • Purinergic signalling in peripheral auditory neurotransmission

    Salih, Salam Gheyath Al-Din (2002)

    Doctoral thesis
    The University of Auckland Library

    P2X receptors, forming ATP-gated ion channels, mediate fast neurotransmission in the central, peripheral and autonomic nervous systems. Preliminary evidence indicated the presence of P2X receptors in the cochlea, with a possible involvement in the neurohumoral regulation of hearing function. This study investigated the hypothesis that extracellular ATP acts as an auditory neurotransmitter or neuromodulator within the inner ear. RT-PCR analysis of rat spiral ganglion neurones (SGN), which innervate the sensory hair cells of the cochlea, detected the expression of three different isoforms of the P2X2 receptor subunit, including a novel functional isoform (designated P2X2-3R). Cellular localisation of the P2X2R subunit mRNA in SGN somata was demonstrated by direct in situ RT-PCR. Furthermore, immunocytochemistry studies using P2X2 receptor-specific antisera, confirmed the expression of the P2X2R protein by SGN somata, and also showed localisation at the region of spiral ganglion neurone synapse with the inner and outer hair cells. Whole-cell patch clamp recordings from cultured post-natal rat SGN demonstrated ATP-activated currents with heterogeneous phenotypes. This is consistent with the functional expression of P2X2R subunit isoforms, and co-expression of additional P2X receptor subunits. However, in situ recordings, using a rat cochlear slice preparation, demonstrated a homogeneous phenotype of ATP-gated current, suggesting heteromultimeric assembly of P2X receptor subunits that is specifically regulated in vivo. Employing a multi-disciplinary approach, the present study provides substantial evidence for a purinergic mode of neurotransmission within the peripheral auditory system. This occurs via ATP-gated ion channels in spiral ganglion neurones, arising from a tightly regulated expression of a specific P2X receptor phenotype.

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  • Māori parents at school: the role of the Māori parent community in the delivery of te reo Māori school curriculum

    Stewart, Alexander George (2000)

    Doctoral thesis
    The University of Auckland Library

    This thesis represents the results of a three-year intervention study of a group of Māori language teachers, their pupils and Māori parent communities in the Northland region of New Zealand. The study was motivated by the problem of continuing low academic achievement for Māori students in state mainstream schools. The assumption that existing teaching outputs of Māori language were quite strong and so could be used to model improvements for other school subjects and teachers to follow for Māori students was examined. In fact this was found to be a mistaken assumption as serious problems were located for the teaching of the Māori language. Two school policy areas were examined to locate possible solutions: Treaty of Waitangi policies in school charters and the operation of Māori Language Resourcing. It was found that the operation by school managements tended to exclude any active role for the Māori parent community. An action research model of intervention was designed and implemented to offer teachers in-service assistance in the provision of practice examinations to help better prepare students in their school certificate written examinations. Teachers were also encouraged to work directly with their Māori parent communities in order to improve teaching, student learning and outcomes. A case-study demonstrates that a dramatic rise in pupil performance occurred when parents worked along side the teacher in the classroom. The thesis argues that the nature of the Treaty of Waitangi provides a rationale for Māori parent participation, for direct involvement into school management (teaching issues) both for Māori students and the Māori language. It is concluded that a successful school for Māori students depends both the strength and shape of the tripartite relationship between the school, the home and the students.

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  • Natural products from New Zealand Latrunculia species sponges

    Grkovic, Tanja (2008)

    Doctoral thesis
    The University of Auckland Library

    In a survey of the secondary metabolite chemistry profiles of ten New Zealand, one Antarctic and one South African-sourced collections of Latrunculia spp. sponges, eighteen discorhabdin alkaloids have been isolated. Four of those, namely discorhabdin K, 3-dihydro discorhabdin A, 1-thiomethyl discorhabdin G*/I, and 16a,17a-dehydro discorhabdin W were fully characterized as new natural products in the series. In addition, for the first time, five enantiomeric pairs and two sets of diastereomers of the naturallyoccurring discorhabdin alkaloids were identified. The absolute configuration of all of the chiral compounds isolated, including new natural products, has been established upon comparison of the observed experimental data with the results of time dependant density functional theory calculations of the electronic circular dichroism spectra. A structure activity relationship study on discorhabdin B, the main natural product of the Wellington-sourced sponges, has identified four reactive centres on the molecule and yielded nine novel semi-synthetic derivatives. Consequently, a new discorhabdin biosynthetic tree was proposed which highlighted discorhabdin B as a crucial precursor to a number of other naturally-occurring analogues. The importance of the iminoquinone moiety and the spirodienone ring with respect to the bioactivity of the compounds in a range of naturally-occurring discorhabdins was demonstrated. A new semi-synthetic derivative, 1-discorhabdyl discorhabdin D, was identified as a potent anti-malarial agent and has opened new possibilities for the therapeutic development of the discorhabdin alkaloids.

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  • A Study of the pathogenesis and immunobiology of pyelonephritis

    Miller, Thomas (1975)

    Doctoral thesis
    The University of Auckland Library

    The experiments carried out during this investigation have studied the pathogenesis and immunobiology of pyelonephritis. Two experimental models of the disease were developed in laboratory animals and several new analytical procedures for studying biological changes during the course of the disease were established. In particular, methods for the determination of glomerular filtration rates in small animals, the automated analysis of antibacterial antibody and the in-vitro determination of the response of rat lymphocytes to phytohaemagglutinin (PHA) were established. The effect of chronic active pyelonephritis on renal function was studied and the effect of antibiotic treatment and elimination of infection on the pathological changes in pyelonephritis was determined. Eradication of infection did not affect the gross pathology and histopathological changes found at autopsy. These experiments have also investigated the role of bacterial interference as a determinant in the epidemiology of renal infection. It was shown that mixed renal infections with E.coli were uncommon and that the pattern of infection was determined by the resident pathogen. The relationship between bacterial infection or the renal parenchyma with E.coli and the establishment of pathological lesions was investigated and the conclusion reached that infection of the kidney is not always associated with pathological changes. The term "acquiescent infection" was then used to describe the host parasite relationship in which active persistent bacterial infection is not associated with pathological lesions. Antigen presentation as a factor in the protective immune response to renal infection was also studied and experiments carried out which demonstrated that immunological memory to the Somatic antigen of E.coli persisted for at least Six months after primary immunization and appeared to be carried by the B lymphocytes. The distribution of B lymphocytes in the peripheral blood and lymphoid sites and the functional capacity of T cells during the course of pyelonephritis were also investigated. Lymphocytes forming the lymphocytic infiltrate in the kidney were identified an thymus derived lymphocytes by their surface labelling characteristics but further experiments showed that T lymphocytes in the kidney, which would normally respond to stimulation with PHA in-vitro, were non-responsive and presumably non-functional. A unique factor associated with renal cells was found to be capable of blocking the PHA response of T lymphocytes, suggesting that ablation of cell-mediated immune mechanisms in the kidney may contribute to the persistence of infection in pyelonephritis. This concept was investigated by studying the effect of a selective deficiency of thymus derived lymphocytes on the course of pyelonephritis. The experiments showed, however, that ablation of T lymphocytes did not appreciably alter the course of the disease. Further experiments were then carried out investigating the role of B lymphocytes in the immune response by manipulation of the hosts immune capacity using immunosuppressive drugs. Animals with pyelonephritis did not produce antibacterial antibody but were able to eliminate organisms more readily from the infected kidney than untreated animals with a normal immune response. This suggests that blocking of the phenomenon of immunologic enhancement may explain these unexpected results and that the immune response to renal infection could have an enhancing role, protecting the bacterial cell from otherwise effective host defense mechanisms. Clinical aspects of antimicrobial resistance in pyelonephritis were also investigated in a study of urinary tract pathogens from 120 patients. The results showed that standard methods for testing antibiotic sensitivity may reject potentially useful antibiotics and that up to 75% of microorganisms considered resistant to individual antibiotics may in fact be sensitive to concentrations of antibiotic attainable in the tubular lumen. In certain circumstances the determination of minimum inhibitory concentration of selected antibiotics may be of considerable value in patient management.

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  • A scanning electron microscopic and electrophysiological investigation of experimental acoustic trauma

    Thorne, Peter Rowland, 1954- (1982)

    Doctoral thesis
    The University of Auckland Library

    Investigations were undertaken to describe and quantitate the topographical abnormalities which develop in the organ of Corti as a result of acoustic trauma, and to determine their relationship to the associated losses of cochlear function assessed by the compound action Potential (N1) and cochlear microphonics (CM). Thirty guinea pigs were exposed, while anaesthetised, to a tone of 3 KHz at 125 dB SPL for 30 minutes. Both organs of Corti were examined by scanning electron microscopy either immediately or 1,3,7 or 14 days after exposure. In the second study 26 anaesthetised guinea pigs were exposed to 5 KHz at 125 dB SPL for 30 minutes. Cochlear potentials were recorded from the round window of the right cochlea and N1 audiograms (sound Pressure level required to elicit N1 Plotted against frequency) and 10 μv isopotential curves (sound pressure level required to produce 10 μv CM plotted against frequency) were produced for each animal either within one hour or 1,7,14 or 28 days later. The same organ of Corti was examined by scanning electron microscopy. Cochlear potentials were compared to mean values from 16 normal guinea pigs. Most animals developed topographical changes in one or both organs of Corti after exposure to 3 KHz (90%) and in the right organ of Corti after 5 KHz (92%). There was a wide variation in both the length (3 KHz: 0.1-4.15 mm; 5 KHz: 0.5-16.0 mm) of lesions and the number of hair cells affected. Both these indices of damage increased significantly (p <0.01) in the 24 hours following exposure to 5 KHz. Early damage to hair cells included either collapse, fusion or loss of stereocilia and there was an increase in the proportion of affected cells towards the centre of the lesions where supporting cells were damaged also. Subsequent to exposure, collapsed stereocilia appeared to become fused and some hair cells, particularly OHC, with stereocilia abnormalities were lost. However, others, particularly IHC, remained for up to 28 days despite abnormal stereocilia. Early changes occurred around the position of maximum displacement of the basilar membrane and subsequent extension of the lesions occurred equally in both apical and basal directions. Fusion was the only stereocilia change to develop after exposure. Regions of the organ of Corti showing supporting cell damage were replaced within 3-7 days by the proliferation of inner sulcus and Claudius’ cells. The substantial initial loss of both N1 thresholds and CM sensitivity partially recovered during the first 24 hours after exposure, but paradoxically, this was associated with the significant increase in the topographical changes in the organ of Corti. N1 threshold loss occurred over all frequencies and was maximum 1/2 – 1 octave higher than the exposure frequency (5 KHz). All lesions occurred within regions corresponding to changes in N1 thresholds. In the first 24 hours topographical changes occurred over a much smaller area of the organ of Corti than indicated by changes in N1 thresholds. Seven or more days later the longer lesions (30%) reflected the extent of changes in N1 but the remainder were smaller than indicated by this functional loss. This suggests that functionally important damage to the cochlea is more extensive than indicated by hair cell loss, stereocilia abnormality or supporting cell changes in the organ of Corti. Therefore, investigations of the effects of noise should not be based simply on topographical changes in the organ of Corti as these often underestimate the extent of injury to the cochlea.

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  • The Epidemiology of birthweight and placental weight in New Zealand

    Thompson, John Michael David (1997)

    Doctoral thesis
    The University of Auckland Library

    The introduction to this thesis is a literature review. Kramer, in a study commissioned by WHO, reviewed the literature prior to 1985 on low birthweight. This is extended, mainly in respect to infants who are small for gestational age with emphasis on important findings in relation to birthweight since that time. Work in New Zealand on birthweight is also summarised. The literature is also reviewed in respect to the mechanisms in the pathway between the placenta and the fetus, and in respect to recent work suggesting a link between birthweight and disease in adult life. This thesis examines factors that influence birthweight and placental weight. Birthweight for gestational age percentile curves for the New Zealand population were firstly defined. small for gestational age (SGA) infants could then be categorised. The thesis considers two sources of data, the first a cross-sectional sample of the New Zealand population from 1987 to 1990 (the control subjects of the New Zealand cot Death study, a national case-control study on sudden infant death syndrome), and the second a hospital population in Auckland (National Womens Hospital (l992)). These two datasets are investigated to determine factors that influence birthweight in a univariate situation and then in the multivariate situation. Independent variables are considered using a priori categorisations and where appropriate Quantile-Quantile (Q-Q) derived categorisations determined by producing plots of the quantiles of cases versus controls. A number of variables under the headings of socio-demographic, lifestyle, genetic, obstetric and nutrition are examined and found to be associated with the outcomes of interest at the univariate level. After controlling in multivariate analyses a number of variables are found to be no longer significant, however some show strong relationships. The variable relating to smoking in both datasets shows the greatest detrimental effect on the outcomes considered in respect to birthweight. This confirms that in New Zealand, as in other places in the world, smoking has significant consequences on birthweight. The data is also investigated for the timing of insult to the fetus from smoking, and is found to be most important during pregnancy. comparison of the results comparing those obtained using a binary outcome for SGA, and those obtained using birthweight continuously, show relatively consistent results. The odds ratios and the decreases in birthweight obtained from both datasets show a relatively linear relationship between the two. An examination into whether a distinct group of individuals exists in respect to having large placentae for birthweight, indentified an artefact in the dataset relating to recording of placental weight for twins. After removal of twins from the dataset, examination of factors that influence placental weight showed that the factors that influence placental weight are not the same as those that influence birthweight. In particular smoking is found not to influence placental weight, and haemoglobin, which has no influence on birthweight, is found to be inversely associated with placental weight. other factors such as parity are found to influence placental weight in the same proportion in which birthweight is affected. In conclusion this thesis shows that factors investigated in New Zealand are consistent with findings in the international literature in relation to birthweight. The results on factors that influence placental weight add to the international literature on a topic on which little work has been carried out. The results of this thesis point to areas where future research needs to be carried out, in particular in relation to maternal nutrition during pregnancy and maternal energy expenditure during pregnancy. There is also a need for further research into the relationships of factors on placental weight and the ratio of birthweight to placental weight, and how these relationships affect health outcomes in childhood and adult life.

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  • Psychological investigations of the experience of chronic pain

    James, Frances Ruth (1991)

    Doctoral thesis
    The University of Auckland Library

    Whole document restricted, but available by request, use the feedback form to request access. This thesis is based on two theoretical models of chronic illness: Large, Butler, James, and Peters (1990) introduced a systems model of musculo-skeletal pain which incorporated many of the variables believed to be important in the development and maintenance of pain. Feldman’s model (1974) addressed the difficulties of adapting to chronic illness. Five studies evaluated specific aspects of these models. The epidemiology of pain in New Zealand (NZ) was derived from a psychiatric epidemiology project. Approximately 80% of NZ adults had experienced a life disrupting episode of pain which had required medical consultation. Subjects who reported episodes of pain were more likely to have psychiatric diagnoses of anxiety, depression, and phobia. They were more likely to describe their health as poor and were currently consulting their doctor more than people who did not report an experience of pain. The estimated average cost of health consulting by people attending Auckland Hospital Pain Clinic (AHPC) for the previous year was $1333(NZ). Most people had some subsidy of costs. The health consulting of the AHPC group was higher than that reported in the NZ health literature. Self image and the experience of pain were assessed in two studies. The first asked subjects at AHPC to describe the typical thoughts, feelings, and behaviours, of someone with chronic pain. Subjects described loss of self esteem, alienation from family and friends, fear of the future, frustration and anger. The descriptions focused on psychological aspects of the experience of pain. The second study of self image used repertory grid technique. Two standardised Illness Self Construct Repertory Grids (ISCRG) were evaluated. Issues in the use of standardised grids are discussed and some aspects of ISCRG application are explored. The two ISCRG indicated subjects often identified themselves as a physically ill person and felt isolated from others. People with pain and their "closest other” (CO) completed the ISCRG(A) and questionnaires on the quality of their relationship. Closest others overestimated the role of the physical illness in their partners’ life and believed that they understood them better than the individual with pain thought they did. The personality dimensions of alexithymia and hypnotisability have been hypothesised as pathways for the development of psychosomatic illness. Individuals with chronic pain were tested to establish whether they weremore alexithymic and more hypnotisable than subjects in a general population control group. This was not verified. The constructs of alexithymia and hypnotisability require critical examination. The experience of pain is common and is associated with psychological distress and high health service use. Self construct appears to be a major factor determining response to pain and to treatment programmes. Chronic pain appears to be a particular challenge for individuals who must accept alteration in their lifestyle with perhaps little understanding of what the future may hold.

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  • Myocardial force and intracellular Ca2+ in an animal model of hypertensive heart failure

    Ward, Marie-Louise (2003)

    Doctoral thesis
    The University of Auckland Library

    Hypertensive heart failure has long been associated with diminished cardiac contractile function, yet the underlying cellular mechanisms are not well understood. The aim of this Thesis was to investigate the relationship between intracellular calcium ([Ca2+]i) and isometric force during the relatively narrow time frame in which long-standing compensated hypertrophy progresses to decompensated end-stage heart failure in an animal model of human essential hypertension. In order to carry out this aim, left ventricular trabeculae were utilized from failing hearts of spontaneously hypertensive rats (SHR) and their normotensive Wistar-Kyoto (WKY) controls. At a physiological stimulation frequency (5 Hz), and temperature (37 °C), the peak stress of SHR trabeculae was significantly reduced compared to WKY, although no differences in the time-course of the twitch were detected. Measurements using fura-2/AM as an index of intracellular [Ca2+] showed that, for SHR, both the peak of the Ca2+ transient and the resting [Ca2+]i were increased and the decay of the Ca2+ transient was prolonged compared to WKY. This unexpected result, i.e. depression of twitch force despite an increased Ca2+ transient, was investigated further by utilizing experimental protocols known to affect [Ca2+]i and force. Varying extracellular calcium ([Ca2+]o) between 0.5 and 5 mM showed that the reduction of force development by SHR trabeculae was not associated with reduced myofilament Ca2+ sensitivity, since, although peak [Ca2+]i continued to increase with increasing [Ca2+]o, peak stress reached a plateau. Investigation of the force-frequency response between 0.2 and 10 Hz showed that the mismatch in peak Ca2+ and peak force was apparent across all frequencies for SHR. A consistent finding of studies that have made measurement of [Ca2+]i in failing myocardium is that the decay of intracellular Ca2+ following SR release is prolonged. Additionally, expression levels of the SR Ca2+ -ATPase have been reported as reduced, in conjunction with increased expression of the sarcolemmal Na+/Ca2+ exchanger. Although the decay of fluorescence was slower for SHR in this study, no experimental evidence was found to suggest that sarcolemmal Ca2+ extrusion was increased in SHR in comparison to WKY. The re-circulation fraction of activator Ca2+ during recovery from potentiation was not different between rat strains, indicating that SL Ca2+ extrusion was not increased in SHR. Additionally, the decay of fluorescence remained slower for SHR even when the SR Ca2+ -ATPase contribution was functionally removed. Inhibition of the SL Ca2+ -ATPase, together with the functional removal of the SR, removed the differences in the decay of fluorescence between rat strains. A decrease in the sarcolemmal extrusion of [Ca2+]i by the Ca2+ -.ATPase might therefore explain the observed differences in the resting [Ca2+]i and in the amplitude of the Ca2+ transient between rat strains. In summary, this study has provided the first measurements of [Ca2+]i and isometric force carried out at physiological temperature and stimulation frequency in LV trabeculae from failing SHR hearts and their age-matched, normotensive, WKY controls. Most importantly, for this animal model the contractile dysfunction typical of heart failure is not associated with reduced availabilty of [Ca2+]i. Instead it is suggested that contractile function is compromised in these LV trabeculae by the increased collagen, and its three-dimensional organisation.

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  • Thermoreception, thermoregulation and the early thermal environment

    Young, Andrew (1985)

    Doctoral thesis
    The University of Auckland Library

    Previous investigations1,2 have shown that the capacity of rats and rabbits reared at an elevated environmental temperature to thermoregulate in the cold is impaired. This impairment appears permanent and is associated with other thermoregulatory dysfunction (altered febrile response and altered response to intrahypothalamic noradrenaline injection). The present study investigated the role of the thermal environment in the development of thermoregulatory function by studying the performance of the intact thermoregulatory system and components thereof at different levels of processing of thermal information (thermoreceptive, early integrative and effector levels). The present study confirmed the impaired capacity of heat-reared rats to maintain colonic temperature in the cold and future indicated that this was likely to be attributable to active rather than passive components of the thermoregulatory system. Exposure to an environmental temperature of 20°C for 20 days was able to prevent thermoregulatory dysfunction (as assessed by intrahypothalamic noradrenaline injection) if it occurred after about 14 days of age. Exposure to 20°C was progressively less effective in averting thermoregulatory dysfunction after about 60-80 days of age. The experimental design identified these effects as being of environmental rather than genetic origin. Thermal information processing at the level of the caudal trigeminal nucleus resembled that described at thermoreceptors. The static and dynamic responses of thermoreceptive neurones at this level were quantified and found not to differ between 20°C – and 30°C-reared rats. The distribution of facial thermal receptive fields and the projections of these at the caudal trigeminal nucleus were mapped and also found not to differ. Thermal information originating from truncal skin was intercepted at a midline midbrain level. Data presented here suggested that the sites at which this thermal information could be intercepted included but probably were not restricted to the raphe nuclci. Both warm- and cold-responsive units were present at the midbrain. The abundance of thermoresponsive units was the same in 20°C- and 30°C-reared rat as was the ratio of warm:cold-responsive units. The stimulus configurations by which responses of midbrain thermoresponsive units could be characterised were more complex than at the caudal trigeminal nuclcus. Thermal responses were principally static with little response to temperature change. The pooled static responses of warm- and cold-responsive units over the 5-45°C range were the same in 20°C- and 30°C-reared rats. The cutaneous receptive fields at the midbrain level were diffuse, covering most of the truncal surface. There was an almost universal and consistent interaction with noxious input at midbrain thermoresponsive units. Warm-responsive units were inhibited by simultaneous noxious stimulation at almost any body site while the activity of cold-responsive units was augmented by such stimulation. At the thermoeffector level, noradrenaline-induced thermogenesis was equal in 20°C- and 30°C- reared rats. Heat-rearing was not observed to produce identifiable effects on the peripheral processing of thermal information, either at the afferent or efferent limbs of the thermoregulatory system. Heat-rearing does however produce changes in thermophysiological responses that are primarily mediated via a central mechanism (responses to intrahypothalamic noradrenaline, febrile response). It is therefore surmised that alterations in thermoregulatory function following heat-rearing are attributable to changes in central rather than peripheral processing of thermal information. 1 Cooper et al., (1980) J Physiol [ Lond ] 303: 165-172 2 Ferguson et al., (1981) Can J Physiol Pharmacol 59: 91-95

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  • The Development and efficacy of cognitive behaviour therapy for multiple sclerosis fatigue: a randomised controlled trial

    Van Kessel, Kirsten (2007)

    Doctoral thesis
    The University of Auckland Library

    Whole document restricted, but available by request, use the feedback form to request access. Aim Multiple Sclerosis (MS) is an unpredictable demyelinating disease of the central nervous system (CNS), with fatigue being one of the least understood symptoms. Based on a systematic review of the literature, a cognitive behavioural model of MS fatigue was developed and used to design a manualised eight session cognitive behaviour therapy (CBT) intervention to treat MS fatigue. The purpose of the randomized controlled trial (RCT) was to investigate the efficacy of CBT compared to relaxation training (RT) to treat fatigue in MS. Methods Seventy-two patients with MS fatigue were randomly assigned to either eight sessions of CBT or eight sessions of RT, designed to control for therapist time and attention. Participants were assessed before and after treatment, and at three and six months follow-up. Primary outcomes included the Fatigue Questionnaire (FQ) and the Clinical Global Impression Scale (CGIS). Secondary outcomes included measures of fatigue related impairment, mood, stress, sleep problems and daytime sleepiness. Seventy of the 72 participants completed all therapy sessions and 69 participants completed all assessments. Results Analyses were carried out by intention-to-heat. There was a significant group by time interaction for fatigue, indicating that the CBT group had significantly greater reductions in fatigue severity than the RT group (p<.05). Conclusions CBT appears to be an effective treatment for MS fatigue, with CBT participants improving significantly more on fatigue than RT participants between baseline and end of treatment. Obtained effect sizes for fatigue in both CBT and RT were considerably larger than those in previous controlled trials of pharmacological and non-pharmacological interventions. Both groups improved on almost all of the secondary outcomes. Findings support the relevance of a cognitive behavioural model for MS fatigue.

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  • Intrauterine growth retardation in the rat: effects on the somatotrophic axis and postnatal sequelae

    Woodall, Sonja Mary (1998)

    Doctoral thesis
    The University of Auckland Library

    Over the past decade, a number of epidemiological studies have provided significant evidence that certain major adult noncommunicable diseases, such as hypertension, ischaemic heart disease and non-insulin dependent diabetes mellitus, may be associated with impaired fetal growth. This phenomenon has been termed "programming" which is essentially the term used for persisting changes in structure and function caused by undernutrition or other adverse influences acting during critical periods of early development. Programming has been used as the mechanistic basis to explain the long term sequelae of intrauterine growth retardation (IUGR). The mechanisms underlying the epidemiological observations remain to be elucidated and developed. While it is well established that severe maternal undernutrition during pregnancy leads to IUGR, there has been relatively little well defined animal studies of the somatotrophic axis and postnatal development of growth retarded offspring. The major objectives of this thesis were to establish a model in the rat of IUGR by nutritional restriction of the dam throughout gestation and to examine the effects of fetal growth retardation on endocrine, molecular and growth parameters during postnatal development. In addition, the development of an animal model for IUGR enabled well defined studies testing distinct hypotheses suggested by the epidemiological observations of professor David Barker and colleagues. Timed matings were performed in Wistar rats and dams were randomly assigned to one of two dietary treatment groups. A control group was fed ad libitum throughout pregnancy and a restricted group was fed 30% of ad libitum intake. Restricted fed dams were observed to lose a significant amount of body weight throughout gestation, due to undernutrition, but caught up to the ad libitum group during the lactating period. Maternal undernutrition significantly reduced fetal and placental weights without altering litter size. Postnatally, body weights of offspring from undernourished dams continued to be reduced until at least 18 weeks of age, although they were observed to be growing at the same rate as ad libitum offspring by 2 weeks of age. A cohort of animals from undernourished dams were maintained to measure blood pressure by tail cuff plethysmography. Offspring from undernourished dams were found to have significantly elevated systolic blood pressures from 18 weeks of age. This observation provides direct experimental support for the hypothesis, derived from human epidemiological studies, that the origin of adult hypertension may originate during fetal life as a result of exposure to a sub-optimal intrauterine environment. Parallel reductions in plasma IGF-I and hepatic IGF-I mRNA concentrations before 15 days of age were also observed in growth retarded offspring. Hepatic IGF-I transcription start sites within exon 1 and exon 2 were coordinately reduced with IUGR up to 15 days of age without changes in GHR and GHBP mRNA abundance. The lack of catch-up growth observed in the IUGR offspring despite normalization of their plasma IGF-I and IGF-I mRNA levels from 15 days of age may be due to a state of partial resistance to GH. This observation lead to a series of treatment studies in which neonatal and juvenile offspring from ad libitum and undernourished dams were treated with growth factors to investigate somatic growth responses as a measure for hormone sensitivity. In both treatment studies, ad libitum offspring from both age groups and juvenile IUGR offspring responded to GH treatment However, neonatal IUGR offspring did not exhibit any response to GH treatment.. Analysis of IGF-I gene expression in neonatal offspring showed that GH treatment elevated IGF-I Eb mRNA in ad libitum but not IUGR offspring. These results suggest a possible mechanism for transient GH resistance in that a post-receptor defect in GH action may contribute to the development of temporary postnatal GH resistance as a consequence of IUGR and fetal programming of IGF-I gene expression. In summary, the development of a model of IUGR in the rat using maternal undernutrition throughout gestation has enabled detailed investigation of nutritional regulation of the somatotrophic axis during fetal development and postnatal sequelae. The studies in this thesis have shown that the somatotrophic axis is markedly altered postnatally by nutritional restriction of the dam throughout gestation, leading to prolonged postnatal growth retardation and elevated blood pressure The mechanisms which lead to the induction of such fetal programming and whether these changes may contribute to the development of subsequent adult-onset disease remain to be addressed in future studies.

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  • High frequency power transistor model

    Egan, Brian (1976)

    Doctoral thesis
    The University of Auckland Library

    The development of a large-signal power transistor model applicable at radio frequencies is described. This model which has its basis in the classical large-signal models is valid for cut-off and active region operation but does not include saturation operation. The model is intended primarily for use in broadband linear radio frequency amplifier applications and is useful up to frequencies of the order of 1/15 f┬. The model is described by two first order nonlinear differential equations and a number of algebraic equations. Equation coefficients are determined from measurements made on the devices under study. Two methods are described for the solution of the model equations. The first and principal method is an iterative one requiring computer assistance whilst the second is analytical and depends upon piecewise linearisation of the device transfer characteristic. This analytical method whilst in some respects inadequate, e.g. distortion level predictions, is easy to implement and despite its limitations affords useful insight into output power capability and frequency limitations of specific devices. The model contains all transistor nonlinearities and parasitic elements of significance and an important feature is the inclusion of device temperature as a model variable, resulting in good accuracy over a wide range of operating conditions. A simplified input impedance representation is evolved and it is demonstrated that input impedance measurements provide a useful window on model structure and aid in the evaluation of parameter values.

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  • Development of active filters: including design limitations imposed by operational amplifier characteristics

    Kay, John Stephen (1977)

    Doctoral thesis
    The University of Auckland Library

    Whole document restricted, but available by request, use the feedback form to request access. The aim of this thesis is the development of an understanding of some of the Limitations involved in the design of active filters. This introduces the idea of imposing an upper bound on the amplitude of the input voltage to an active filter such that the distortion, introduced, in the input stage of the operational amplifier, is Less then a value specified in the design, and investigating theoretically the errors in the frequency response of the actual circuit, caused by the operational amplifier which is considered linear but nonideal in that the analysis includes the finite input impedance and output conductance as well as the single-pole rolloff characteristic. The results of this theoretical research have been incorporated into a package of highly interactive computer programs, collectively called the Active Filter synthesis program, for the design of minimum-phase lowpass, highpass, bandpass, and bandstop active filters, the group-delay equalization of these filters and also of both unloaded, and loaded telephone Lines, and the displaying of their ideal frequency responses. The above-mentioned research arose from the design and construction of an experimental 600/1200 Baud, Modem, the filters in which provide a practical application of these developments.

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  • New Zealand's London: The metropolis and New Zealand's culture, 1890-1940

    Barnes, Felicity (2008)

    Doctoral thesis
    The University of Auckland Library

    Whole document restricted, but available by request, use the feedback form to request access. The role of London in forming New Zealand’s culture and identity is a significant feature of New Zealand’s cultural history that has, until now, been overlooked. Ties with London and with ‘Home’ generally, have received little study, and ‘Britishness’ in New Zealand is largely considered a legacy of demography to be eventually outgrown. This thesis suggests something different. During the period 1890-1940, technology changed cultural perceptions of time and space, and it changed the relationship between metropole and former colony too. These technologies drew New Zealand and London closer together. London was constructed as an active part of the New Zealand cultural landscape, rather than as a nostalgic remnant of a predominantly British-born settler population. London was New Zealand’s metropolis too, with consequences for the way New Zealand culture was shaped. This thesis considers the cultural impact of London using four tropes linked to those changing perceptions of time and space. ‘Greater New Zealand’ is concerned with space, whilst ‘“New” New Zealand’ is concerned with time. ‘London’s Farm’ and the ‘Imaginative Hinterland’ consider propinquity and simultaneity respectively. Each theme draws from different bases of evidence in order to suggest London’s broad impact. Collectively, they argue for a shift away from a core and periphery relationship, towards one better described as a city and hinterland relationship. This approach draws upon existing national, imperial, and cultural historiography, whilst at the same time questioning some of their conventions and conceptions. New Zealand as hinterland challenges the conceptual borders of ‘national history’, exploring the transnational nature of cultural formations that otherwise have been considered as autochthonous New Zealand (or for that matter, British) developments. At the same time, whilst hinterlands may exist as part of empire, they are not necessarily products of it. Nor are they necessarily formed in opposition to the metropole, even though alterity is often used to explain colonial relationships. ‘New Zealand’s London’ is, instead a reciprocal creation. Its shared cultural landscape is specific, but at the same time, it offers an alternative means for understanding other white settler colonies. Like New Zealand, their cultural histories may be more complex cultural constructions than national or imperial stories allow.

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  • The complaints and disciplinary process in New Zealand and the effect of complaints on doctors

    Cunningham, Wayne Kenneth (2005)

    Doctoral thesis
    The University of Auckland Library

    New Zealand society assumes that the medical complaints process enhances the delivery of medical care, although the literature suggests that complaints may impact negatively on doctors, and their ability to practice. This thesis examines the impact of the complaints process on doctors in New Zealand. It considers the practice of medicine from the viewpoints of the epistemology of medicine; the doctor-patient relationship; and the notion of professionalism. It presents the results of research methods investigating New Zealand doctors using focus groups; a cross sectional questionnaire based survey; and in-depth semi-structured interviews. Findings include: One in three doctors has received a complaint. The annual rate of complaint is 5.70%, 15% of complaints are upheld. Complaints impact negatively on the person of the doctor, the doctor-patient relationship, and doctors’ ability to practice. The purposes of a complaints system include: the maintenance of trust and professional standards; being a voice for patients; and learning from mistakes and errors. Doctors’ attitudes are consistent with notions of professionalism. Defensive medicine is an adverse outcome of the complaints process. Doctors suggest a Complaints Tribunal as a single point of entry into the complaints process. The current complaints process is not improving the delivery of medical care to New Zealand society. New Zealand doctors are aware of both the biomedical and bio-psychosocial paradigms underlying modern medicine, and the results confirm the importance of the self of the doctor and the doctor-patient relationship in medical practice. The emergence of defensive medicine indicates that doctors may respond to complaints by practicing in a way that is not in their patients’ best interests, but which serves to protect doctors themselves. Defensive medicine risks being unrecognised and becoming normalised into mainstream medical practice. The negative impact of complaints on doctors’ values and beliefs indicate an erosion of values based professionalism. This thesis suggests that an appropriate model for considering medical professionalism is as a state of relationship between doctors and society. Appropriate change to the complaints process may enhance the doctor-society relationship and ultimately enhance the delivery of medical care in New Zealand.

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  • The Effect of Substrate Parameters on the Morphology of Thermally Sprayed PEEK Splats

    Withy, Benjamin Paul (2008)

    Doctoral thesis
    The University of Auckland Library

    Thermal spray is a well established technology that is commonly used in the aerospace and automotive industries. This thesis reports on the effect that substrate surface chemistry, morphology and temperature has on the morphology of PEEK single splats on aluminium substrates. PEEK single splats were deposited by HVAF and plasma spraying on aluminium substrates with 6 different pretreatments. Substrates were either sprayed at room temperature, or 323°C, and a subset of substrates was held at incremental temperatures up to 363°C. HVAF deposited splats on room temperature substrates showed sensitivity to surface chemistry, with increased circularity and area associated with low levels of hydroxide and chemisorbed water on the aluminium surface. Substrates held at 323°C were more sensitive to substrate morphology, where rough surfaces resulted in decreased circularity and area apparently independent of surface chemistry. Substrate temperature trials revealed a significant step in the results, equating to greater circularity, and lower splat area, perimeter and Feret diameter. This step occurred between 123°C and 163°C, the two points bracketing the glass transition temperature of PEEK (143°C). This result was due to the relaxation of splats deposited on surfaces above 143°C, whilst splats on cooler substrates quench through the glass transition and do not relax. PEEK splats deposited by plasma spray on room temperature and 323°C substrates showed sensitivity to the amount of hydroxide and chemisorbed water present on the aluminium substrates, with low levels resulting in more circular and larger area splats. Plasma splats did not show the same temperature effects as HVAF splats, thought to be due to the more molten state of plasma splats upon impact compared to the HVAF splats. The primary conclusions reached were that plasma sprayed polymers were sensitive to surface chemistry, and that as such the surface chemistry of a substrate should be considered when forming plasma spray polymer coatings. It was also concluded that the kinetic energy of particles in HVAF thermal spray contributed significantly to the thermal energy of a particle on impact, allowing for improved splat properties without overheating the particles in flight. Finally it was concluded that substrate temperature is far more important for HVAF thermal spray of polymers than plasma spray of polymers, but that it improves splat properties for both techniques.

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  • Assessment of ductile endurance of earthquake resisting steel members

    Hyland, Clark (2008)

    Doctoral thesis
    The University of Auckland Library

    Whole document restricted, but available by request, use the feedback form to request access. This thesis provides a structural and materials engineering explanation for many of the running fractures that occurred in steel structures during the destructive Kobe and Northridge earthquakes in the mid 1990s. A method is developed that allows the ductile endurance of structural steel members subjected to cyclic plastic deformation during earthquakes to be assessed and for pre-necking running fractures to be avoided. The study commenced following the 2000 World Earthquake Conference in Auckland. The conference brought together the findings of the huge research effort, in America, Japan, Europe and New Zealand, that followed the Kobe and Northridge earthquakes. The running fractures that had occurred in steel structures represented an unpredicted failure mode that structural engineers have not known how to predict or suppress through the engineering design process. A clear fundamental understanding of the causes and how to prevent the fractures did not arise from the conference. In fact apparently conflicting results were reported. Full scale cyclic tests in New Zealand on structural assemblies had not resulted in running fractures, whereas tests in American and Japan had. Structural engineers designing earthquake resistant structures rely on constructional steel to be materially homogeneous and nominally tri-linear in behaviour. Steel is expected to behave elastically under regular in-service loading, have a reliable and flat yield stress-strain characteristic, and under overload then develop predictable levels of strain-hardening in conjunction with significant plastic elongation up to its ultimate tensile strength. Steel is expected to eventually fracture after further plastic elongation and necking. Ductile design strategies and methods utilise the plastic elongation characteristics of steel to protect structures in earthquake. Plastic deformation is considered to beneficially dissipate energy generated in the structure by a severe earthquake and also dampen the structure’s response. The occurrence of running fracture without significant cyclic plastic deformation and before section necking in steelwork, therefore undermines the basis of the ductile seismic design approach. The initial part of the thesis is devoted to bringing together the fundamental aspects of materials engineering related to fracture of constructional steel. This is intended to provide a bridge of knowledge for structural engineering practitioners and researchers not fully conversant with materials engineering aspects of fracture. Fracture behaviour in steel is a broad and complex topic that developed rapidly in the twentieth century driven by the demands of technological growth. The unexpected fracture of welded liberty ships at sea in World War 2; the need for reliable long term containment for the nuclear reactors in the 1950s and 1960s; and prevention of fatigue failures in aircraft frames since the 1950s all drove engineering research into steel fracture behaviour. There are many subtle variations in definitions in the published literature on fracture that can be confusing. Therefore an attempt has been made to clarify terminology. The term brittle fracture in particular is only used in this thesis as applying to running fracture when the general or far field tensile stresses are below the yield stress of the steel. The term pre-necking or running fracture is preferred to describe the condition more broadly which may occur prior to and also after general yielding, but before section necking. Running fracture is a manifestation of pre-necking fracture in which insufficient plastic flow is available in the assembly to absorb the energy released upon fracture. The experimental studies investigated the behaviour of constructional steel commonly used in New Zealand, at various levels of plastic strain. This started with Charpy V-Notch (CVN) testing which revealed that a significant transition temperature shift and curve shape change occurs with increasing plastic strain and the associated strain-hardening. This showed that the ability of steel to avoid pre-necking or running fracture reduces as the level of plastic strain-hardening increases. Temperature controlled Crack Tip Opening Displacement (CTOD) testing was then undertaken. The setting of testing temperatures for the CTOD tests were guided by review of the CVN test results, using published CVN to fracture toughness correlation methods. However running cleavage fractures developed in the CTOD specimens at higher than predicted temperatures of 10 oC and 20 oC. These are typical service temperatures for structures in New Zealand and so are very likely to occur at the time of an earthquake. The implication from this is that there are levels of strain-hardening and conditions of material notching constraint that can lead to pre-necking and running fracture in New Zealand fabricated steel structures, under severe earthquake loading. Care was taken in the CTOD testing to monitor and maximise the capture of data electronically using a specially developed Direct Current Potential Drop method. This allowed the test results to be analysed and considered in varying ways, leading to a consistent assessment of the CTOD, crack growth, and the specific work of fracture in each test piece. While CTOD test results have sometimes been published by structural and welding engineering researchers in the wake of Kobe and Northridge, the results were typically of little use for this study as the CTOD initiation point was generally not identified effectively. The effect of remote plastic flow in the specimens was also not adequately accounted for. The CTOD test results were often simply used to help correlate other factors observed by the researchers. Side-grooving of specimens was not reported as having been used in any of the published results reviewed. When conducting CTOD test with highly ductile constructional steels it is very difficult to get useful CTOD results if the specimens are not side-grooved, as significant necking and tunnelling will otherwise occur and limit the usefulness of the results. Work by Knott and also by McRobie and Smith was seminal in terms of identifying some critical aspects of plane strain development in CTOD tests, and the links to non-metallic particle density with respect to fracture toughness and CTOD at initiation. Some of their findings with regards to the effect of pre-strain on CTOD initiation were subsequently found to confirm the experimental findings in this study. No effective methodology for prediction of pre-necking or running fracture in a structural member or assembly when subjected to gross plastic cyclic deformation was found to exist in the literature. It was concluded however that the principles of specific work of fracture, and monotonic and cyclic fracture similitude were particularly relevant. These were therefore utilised in the development of the design method proposed in this thesis. The CTOD test results were reviewed, isolating the remote plastic flow component, to determine the critical specific work of fracture property Rc of the steels tested. A meeting with Professor Kuwamura at the University of Tokyo was providential, allowing discussion of his similitude principle, and observations in person of some of the fractured specimens developed during his full scale test series’. Running fractures with cleavage were evident in the specimens, with their tell-tale chevron markings. He had predicted running fracture problems in structures in Japan ahead of the Kobe earthquake and been largely ignored. His insights were subsequently seriously considered in Japan after the earthquake. He and his colleagues developed the principle of structural similitude that relates monotonic fracture displacement ductility to cyclic fracture displacement ductility for a particular assembly. This arose from their observation that running fractures developed from ductile crack formation at blunt notches in structures. The similitude principle has echoes of the Coffin-Manson approach to ductile crack initiated low cycle fracture. The principle of similitude has a log–log relationship as does the Manson-Coffin relationship. So where notch plasticity controls the initiation of fracture in a structural assembly it is conceptually reasonable to expect that the number of cycles to initiation of fracture from a notch will have a log–log relationship to the amplitude of the cyclic strain developed in the notch. Kuwamura found that steel assemblies with lower CVN energy had reduced cyclic fracture endurance than the same assemblies made with steel with higher CVN impact energy. However no method of predicting performance of any particular assembly could be developed from his observations. The benefit of his method primarily relates to the minimising of testing necessary to assess the fracture limited cyclic displacement ductility of a structural assembly. However it doesn’t provide a means for designing a structural assembly to achieve specific levels of ductile endurance other than clearly identifying the need to use steel with good CVN characteristics. The most significant development arising from this thesis is therefore the development of a design method to assess cyclic ductile endurance. The method utilises the specific work of fracture properties obtained from CTOD specimens of the steel in conjunction with a relatively simple fracture mechanics assessment and an elasto-plastic finite element analysis (FEA). The FEA model is used to determine the displacement ductility of the assembly at the calculated onset of pre-necking fracture. The elasto-plastic stress–strain properties of the steel in various pre-strain states required for the FEA may be derived from tensile testing. Kuwamura’s similitude principle is then used to predict cyclic plastic endurance at various constant displacement ductility amplitudes. The method is extended using Miner’s rule to allow for the effects of increasing variable amplitude cyclic plastic loading. In summary the thesis explains why pre-necking and running fractures occur in steel members subjected to cyclic plastic deformation during a severe earthquake. In addition a method for consistently assessing the ability of structural steel assemblies to achieve a specified level of ductile endurance during earthquakes is proposed. The method is verified against published results for a cyclic test of a simple steel member with a crack at mid-span.

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  • Network event detection with entropy measures

    Eimann, Raimund E. A. (2008)

    Doctoral thesis
    The University of Auckland Library

    Information measures may be used to estimate the amount of information emitted by discrete information sources. Network streams are an example for such discrete information sources. This thesis investigates the use of information measures for the detection of events in network streams. Starting with the fundamental entropy and complexity measures proposed by Shannon and Kolmogorov, it reviews a range of candidate information measures for network event detection, including algorithms from the Lempel-Ziv family and a relative newcomer, the T-entropy. Using network trace data from the University of Auckland, the thesis demonstrates experimentally that these measures are in principle suitable for the detection of a wide range of network events. Several key parameters influence the detectability of network events with information measures. These include the amount of data considered in each traffic sample and the choice of observables. Among others, a study of the entropy behaviour of individual observables in event and non-event scenarios investigates the optimisation of these parameters. The thesis also examines the impact of some of the detected events on different information measures. This motivates a discussion on the sensitivity of various measures. A set of experiments demonstrating multi-dimensional network event classification with multiple observables and multiple information measures concludes the thesis.

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