Showing papers by "University of Canterbury published in 1995"

Diversity Patterns in Stream Benthic Invertebrate Communities: The Influence of Habitat Stability

Abstract: Invertebrate diversity patterns were examined in 11 freshwater habitats (10 streams and a windswept lake shore) of similar physicochemical nature but different thermal and hydrologic stability in the Cass-Craigieburn region, New Zealand. Species richness and density were markedly higher at the more stable sites, but species evenness peaked at sites of intermediate stability. Of the 20 environmental variables examined, a multivariate instability index incorporating temporal variation in depth, temporal variation in current speed, substrate stability, the Pfankuch channel stability index, temperature range, and stream reach tractive force was the single best predictor of the number of species, whereas epilithic pigment concentration was the single best predictor of invertebrate density. The pattern in species richness did not support any of three diversity hypotheses considered. In contrast, the pattern in species evenness suggested competitive exclusion may be occurring patchily and that Huston's dynamic equilibrium model may have some validity, at least at the level of the patch. However, the strong link between productivity and stability apparent in these habitats, and a lack of information on the effects of increased productivity on competition in stream benthic communities makes any firm assessment of the latter model difficult. The observed diversity patterns are, however, consistent with the idea that high diversity is maintained in these habitats by an interaction between low levels of disturbance and habitat patchiness.

Chronology and dynamics of a large silicic magmatic system: Central Taupo Volcanic Zone, New Zealand

Abstract: The central Taupo Volcanic Zone in New Zealand is a region of intense Quaternary silicic volcanism accompanying rapid extension of continental crust. At least 34 caldera-forming ignimbrite eruptions have produced a complex sequence of relatively short-lived, nested, and/or overlapping volcanic centers over 1.6 m.y. Silicic volcanism at Taupo is similar to the Yellowstone system in size, longevity, thermal flux, and magma output rate. However, Taupo contrasts with Yellowstone in the exceptionally high frequency, but small size, of caldera-forming eruptions. This contrast reflects the thin, rifted nature of the crust, which precludes the development of long-term magmatic cycles at Taupo. 11 refs., 4 figs., 1 tab.

The Cretaceous Separation Point batholith, New Zealand: granitoid magmas formed by melting of mafic lithosphere

Abstract: The Early Cretaceous Separation Point batholith of the South Island, New Zealand, represents the final magmatic stage of an extensive arc system located on the SW Pacific margin of Gondwana during the Mesozoic. The batholith consists of Na-rich, alkali-calcic diorite to biotite-hornblende monzogranite. The rocks are distinct from calc-alkaline subduction-related granitoids, but comparable with those of adakite and Archaean trondhjemite-tonalite-dacite suites. Primitive Sr and Nd isotopic ratios and the absence of inherited zircon, indicate that the granitoids experienced little, if any, interaction with felsic crust. Their geochemistry is consistent with melting of a basaltic protolith of amphibolite mineralogy, either young, hot, subducted oceanic crust or newly underplated material beneath a thickened continental arc. The latter model is preferred because Separation Point rocks do not posess MORB isotopic characteristics, and cannot be explained as mixtures of MORB-melt and continental crust. Most likely it involves melting of basal arc material in response to the collision and thrusting of the arc beneath the continental margin following subduction of a back-arc basin. On the basis of strong geochemical similarities, the Early Cretaceous Western Fiordland Orthogneiss of SW New Zealand is considered to be the lower crustal equivalent of the Separation Point batholith.

Experimental and theoretical studies on a distributed temperature sensor based on Brillouin scattering

Abstract: Results are reported from recent research on the use of the Brillouin gain/loss mechanism for distributed sensing. A theoretical model of the interaction of the pulsed and CW beams is described and compared with experiments. Results from a system with a 51 km sensing length are presented. We finally investigate issues related to the variation within the sensing fiber of the polarizations of the two beams. >

A Descriptive Model of the Offense Chain for Child Molesters

Abstract: A grounded theory approach was taken to the qualitative analysis of the descriptions of thoughts and feelings provided by 26 incarcerated child molesters while describing their most recent or typical offense. The resulting descriptive model comprised nine stages, with three contributing factors that describe the sequence of cognitive and behavioral events that form an offense chain. The model incorporates offender type, offense type, and offers a description of the possible interactions between the various stages and factors. The model was then applied to the offense descriptions of an independent sample of 12 incarcerated child molesters in order to ascertain its cross-sample validity and the reliability of classification. The results suggest that the model has provisional validity and adequate interrater reliability. The theoretical, research, and clinical implications of the descriptive model are then discussed.

Attachment style and intimacy deficits in sexual offenders: A theoretical framework

Abstract: In the past few decades a number of theories have been developed to further our understanding of various aspects of sexual offending. Recent work has focused on the relationship between early interpersonal experiences and the presence of intimacy deficits in sexual offenders. The present paper develops a comprehensive attachment model of intimacy deficits in sexual offenders by drawing extensively upon the burgeoning interface between the attachment literature and social cognition research. In particular, the concept of an internal working model, as developed by Bowlby, is introduced as a bridge between early attachment experience and adult intimacy problems. It is suggested that a comprehensive model of intimacy deficits in relation to the sexual offender must pay attention to attachment style, the internal working model, and current behavioral strategies for gaining or avoiding intimacy. The clinical and research implications of this model are presented and discussed.

Mechanisms of calcium oscillations and waves: a quantitative analysis.

Abstract: Oscillations and waves of increased intracellular free calcium concentration ([Ca2+]i) are observed in a wide range of cell types. Because of their inherent nonlinear nature and the consequent unreliability of intuitive approaches, mathematical modeling has an important role to play in the study of these phenomena. One important class of oscillations and waves is dependent on the presence of inositol (1,4,5)-trisphosphate (IP3), which releases Ca2+ from internal stores via the IP3 receptor/Ca2+ channel. With the minimum possible mathematical formalism, we review mechanistic models for IP3-dependent Ca2+ oscillations and waves. These models are based on the regulation of the IP3 receptor by both IP3 and Ca2+, and incorporate experimental data on the steady-state and kinetic properties of the receptor. The extension of the models to describe intracellular and intercellular Ca2+ waves is considered.

Temperament in eating disorders

Abstract: This study examined dimensional personality and temperamental characteristics in women with eating disorders. Clinical symptoms, personality, and temperament were examined in 30 women with anorexia nervosa (AN), 32 women with bulimia nervosa with no history of anorexia nervosa (BN), and 20 women with comorbid anorexia and bulimia nervosa (AB). Temperament differed markedly across the groups on the Tridimensional Personality Questionnaire (TPQ) with AN women showing greater reward dependence, BN women scoring higher on novelty seeking subscales, and AB women showing high harm avoidance. The TPQ subscales also displayed higher classification accuracy than other personality and symptom measures. Temperamental features are distinct across eating disorder subtypes. Temperament could reflect differential vulnerabilities for the development of specific eating disorder symptom clusters. © 1995 by John Wiley & Sons, Inc.

Duration Dependence and Dispersion in Count-Data Models

Abstract: This article explores the relation between nonexponential waiting times between events and the distribution of the number of events in a fixed time interval. It is shown that within this framework the frequently observed phenomenon of overdispersion—that is, a variance that exceeds the mean—is caused by a decreasing hazard function of the waiting times, whereas an increasing hazard function leads to underdispersion. Using the assumption of iid gamma-distributed waiting times, a new count-data model is derived. Its use is illustrated in two applications, the number of births and the number of doctor consultations.

Cognitive Distortions and Affective Deficits in Sex Offenders: A Cognitive Deconstructionist Interpretation1

Abstract: Sexually aggressive behavior is often facilitated and justified by distorted thinking and affective deficits. However, there is no clear conceptual model that accounts for the mechanisms which generate these phenomena and informs treatment goals. Sex offenders frequently demonstrate a number of underexplained features such as denial or minimization of offending, victim blaming, passivity, covert planning, dependence on immediate consequences, empathy and other emotional regulation deficits, intimacy and other social competency deficits, and, finally, alcohol and other drug problems. These features are usually seen as offense precursors. We argue that Baumeister's construct of cognitive deconstruction, the process by which people attempt to reduce the negative implications of self-awareness, provides both a middle-level theoretical explanatory framework that integrates these puzzles in a parsimonious way and a mechanism that suggests that these features may be consequences of, as well as precursors to, an offense. Suggestions for research and clinical practice are offered.

Temperament, character, and personality disorder in bulimia nervosa.

Abstract: In a sample of 76 women participating in a clinical treatment trial for bulimia nervosa, we examined the clinical differences between subjects with and without concurrent personality disorders and the ability of “self-directedness” (a character scale of Cloninger's Temperament and Character Inventor

Effects of contrasting land use on physico‐chemical conditions and benthic assemblages of streams in a Canterbury (South Island, New Zealand) river system

Abstract: Physico‐chemical conditions and benthic invertebrate assemblages in streams draining catchments dominated by different land use activities were investigated near Hanmer Springs, South Island. Four streams in pastoral, scrubland, exotic pine plantation forest (primarily Pinus spp.), and native beech forest (Nothofagus spp.) catchments were sampled in four seasons. Alkalinity, pH, and calcium concentrations were highest among scrubland streams, whereas iron and potassium concentrations were highest in pastoral streams. Both taxonomic richness and invertebrate biomass were greatest in the beech forest streams where most species of Ephe‐meroptera, Plecoptera, Coleoptera, and Diptera were found. Forest streams were dominated by the mayflies Deleatidium and Coloburiscus humeralls, the stonefly Stenoperla prasina, and the caddisfly Olinga feredayi. The facultative shredder Austroperla cyrene was also abundant in pine forest streams. However, mayfly, stonefly and caddisfly taxa were poorly represented in...

Late Pleistocene and Holocene vegetation history, Central Otago, South Island, New Zealand

Abstract: Pollen diagrams from upland blanket bogs and mire‐pool complexes on the southern Garvie Mountains and the Old Man Range, and from a sag pond mire on the slopes of the Kawarau Gorge, record the vegetation history of the last 12 000 years in Central Otago, the driest region of New Zealand. During the late‐glacial/early Holocene these subalpine sites supported grassland/shrubland vegetation. Trees or tall scrub were absent. Tree ferns became increasingly common in the early Holocene, most likely as small stands in damp, sheltered locations. At 7500 yr B.P. a coniferous forest of Prumnopitys taxifolia, Dacrycarpus dacrydioides and Podocarpus abruptly replaced the previous grassland communities at lower altitudes, while a coniferous scrub of Phyllocladus alpinus and Halocarpus bidwillii formed the upper treeline. The reafforestation of Central Otago and adjacent regions was completed 2000 years after podocarp‐dominant forest began to occupy coastal regions. The delay is attributed to drier climates in the inte...

The Harmonic Domain. A frame of reference for power system harmonic analysis

Abstract: The Harmonic Domain is a general frame of reference for power system analysis in the steady state which models the coupling between phases and between harmonics. In this frame of reference the nonlinear components, converted into harmonic Norton equivalents, are combined with the rest of the system and solved iteratively by the Newton-Raphson technique. This paper describes the structure of the new domain and illustrates its potential applications in a small power system with multiple nonlinearities. >

Maximum likelihood decoding of uncoded and coded PSK signal sequences transmitted over Rayleigh flat-fading channels

Abstract: The problem of maximum likelihood (ML) detection for uncoded and coded M-PSK signals on Rayleigh fading channels is investigated. It is shown that, if the received signal is sampled at baud-rate, a ML receiver employing per-survivor processing can be implemented. The error rate performance of this receiver is evaluated by means of computer simulations and its limitations are discussed. In addition, it is shown that, on a fast fading channel, the error floor in the BER curve can be appreciably lowered if more than one received signal sample per symbol interval is processed by the receiver algorithm, Finally, a sub-optimum two-stage receiver structure for interleaved coded PSK systems is proposed. Its error rate performance is assessed for simple trellis-coded modulation schemes and compared to that provided by other receiver structures.

Spatial patterns in benthic invertebrate community structure: products of habitat stability or are they habitat specific?

Abstract: SUMMARY 1. The effects of habitat stability on benthic invertebrate community structure were examined at eleven sites (ten streams and a wind-swept lake shore) with similar physicochemical characteristics but differing stability. 2. Habitat characteristics were assessed to place the study sites within the framework of the disturbance-productivity-diversity model, the intermediate disturbance hypothesis and a variant of the habitat templet model to examine their predictions with respect to community structure. 3. Many of the most common invertebrate species were present at all the study site, although their relative abundance and density differed markedly between sites. Thus, while stability did not appear to affect colonization of the study sites by these taxa, it did affect their relative success. 4. Communities at unstable sites were very similar and shared a number of taxa such as Deleatidium, Austrosimulium and several species of chironomid, presumably well-adapted to surviving and recolonizing after flood events. 5. Communities at the stable sites differed markedly, both from each other and the group of unstable sites. The characteristic fauna at each of the stable sites seemed to be a result of the site's intrinsic character and possibly biotic interactions. 6. Although stability was a pervading influence on community structure, acting as a bottleneck to the development of a site-specific suite of taxa, none of the above models could adequately explain the observed patterns.

Fragmentation, Disturbance, and Plant Distribution: Mistletoes in Woodland Remnants in the Western Australian Wheatbelt

Abstract: Spatial heterogeneity and patchy distributions of species in intact landscapes are likely to lead to complex and unpredictable distribution patterns in remnants following fragmentation. We examined this proposition in relation to the mistletoe Amyema miquelii, which exhibits a clumped distribution in Eucalyptus salmonophloia woodlands in the Western Australian wheatbelt. We sampled mistletoe distribution and abundance in 14 woodland fragments ranging from 2.4 to 60.5 ha and in 14 sections of roadside corridors. These sites represent all known fragments and corridors containing E. salmonophloia in a 1680-km2 study area. We found that large fragments were more likely to have mistletoes than small fragments, but that small fragments either contained many or few to no mistletoes, reflecting the way fragmentation lsamplesr the pre-existing distribution. Superimposed on this sampling effect is the influence of disturbance. Fragments subjected to stock grazing contained no mistletoes. This indicates that grazing modified the habitat either for the mistletoe itself, through changed water relations, or for the frugivorous birds which may disperse mistletoe fruit, through removal of the shrubby understory. Only one A. miquelii plant was found on 26.3 km of roadside corridor, despite tree densities in corridors being similar to those in fragments. Roadside areas are generally considered good habitat for mistletoes, and their absence suggested that fruit-dispersing birds either did not use the corridors or did not stay in them long enough to deposit mistletoe seeds. These results indicate that, in order to predict biotic responses to fragmentation, information on distribution patterns and scales of patchiness in the prefragmentation landscape is required and the effects of fragmentation per se are likely to be confounded by other factors such as disturbance. Furthermore, quantifying fragmentation effects is difficult because of the small sample sizes typical of highly fragmented landscapes. La heterogeneidad espacial y la distribucion en parches de especies en paisajes intactos son proclives a conducir a patrones de distribucion complejos e impredecibles en los remanentes que suceden a la fragmentation. Examinamos este tema en relacion al muerdago Amyema miquelii, una especie que exhibe una distribucion contagiosa en los bosques de Eucalyptus salmonophloia del cinturon de trigo de Australia occidental. Muestreamos la distribucion y abundancia del muerdago, en 14 fragmentos de bosques que oscilaban entre 2.4 y 60.5 ha y en 14 secciones de corredores de los bordes de rutas. Estes sitios representan todos los fragmentos y corredores conocidos que contienen E. salmonophloia en los 1680 km2 del area de estudio. Encontramos que los fragmentos mas grandes eran mas proclives a tener muerdago que los fragmentos mas chicos, pero los fragmentos mas pequenos contenian mucho, poco o ningun muerdago, reflejando el modo en que la fragmentation lmuestrear la distribucion pre-existente. Superpuesto a este efecto de muestreo esta la influencia de las perturbaciones. Los fragmentos sujetos a pastoreo de ganado no tuvieron muerdagos. Esta situacion indica que el pastoreo modifico el habitat para los muerdagos, a traves del cambio en las relaciones hidricas, o bien para los pajaros frugivoros que pueden dispersar los frutos del muerdago, a traves de la remocion de las area arbustivas del sotobosque. Solamente una planta de A. miquelii fue encontrada en los 26.3 km de corredor a lo largo de la ruta, a pesar que la densidad de arboles en los corredores fue similar a la encontrada en los fragmentos. Las areas a lo largo de las rutas son generalmente consideradas como buenos habitats para los muerdagos, pero su ausencia sugiere que los pajaros dispersores de los frutos no utilizaron los corredores o bien no estuvieron un tiempo suficiente como para dspositar las semillas de muerdago. Estos resultados indican que, a efecto de predecir las respuestas bioticas de la fragmentacion, se requiere informacion sobre los patrones de distribution y las escalas de la distribution contagiosa del paisaje previo a la fragmentacion. Los resultados tambien indican que los efectos de la fragmentacion en si mismos tienden a confundirse con otros factores tales como la perturbacion. Mas aun, la cuantificacion de los efectos de la fragmentacion resulta dificil debidio al pequeno tamano de muestra tipico en los paisajes altamente fragmentados.

Model selection criteria: an investigation of relative accuracy, posterior probabilities, and combinations of criteria

Abstract: We investigate the performance of empirical criteria for comparing and selecting quantitative models from among a candidate set. A simulation based on empirically observed parameter values is used to determine which criterion is the most accurate at identifying the correct model specification. The simulation is composed of both nested and nonnested linear regression models. We then derive posterior probability estimates of the superiority of the alternative models from each of the criteria and evaluate the relative accuracy, bias, and information content of these probabilities. To investigate whether additional accuracy can be derived from combining criteria, a method for obtaining a joint prediction from combinations of the criteria is proposed and the incremental improvement in selection accuracy considered. Based on the simulation, we conclude that most leading criteria perform well in selecting the best model, and several criteria also produce accurate probabilities of model superiority. Computationally intensive criteria failed to perform better than criteria which were computationally simpler. Also, the use of several criteria in combination failed to appreciably outperform the use of one model. The Schwarz criterion performed best overall in terms of selection accuracy, accuracy of posterior probabilities, and ease of use. Thus, we suggest that general model comparison, model selection, and model probability estimation be performed using the Schwarz criterion, which can be implemented given the model log likelihoods using only a hand calculator.

Ecotourism: towards a key elements approach to operationalising the concept.

Abstract: Increasing usage of the term ecotourism has done little to clarify the concept. Indeed, a wide range of definitions now exist, with much of the debate in the field occurring at a conceptual or semantic level. This paper presents a new approach to operationalising the concept, one based on classification using a set of measurable key elements covering the participant, operator and resource management perspectives. The approach is illustrated by a survey of 22 nature‐based tourism operators in British Columbia. Less than a quarter of the operations surveyed were subsequently classified as ecotourism, the majority of the ventures being excluded on the protected area criterion. Classification in this way enables the importance of specific key elements to be assessed and highlights the sorts of issues, both conceptual and methodological, which systematic field testing generates.

Immobilization of 15N in forest litter studied by 15N CPMAS NMR spectroscopy.

Abstract: Solutions labelled with 15 N were applied as ( 15 NH 4 ) 2 SO 4 or K 15 NO 3 to isolated microplots in the floor of mountain beech forest (Nothofagus solandri var cliffortioides) and incubated for 135 days under field conditions of moisture and temperature Solid state 15 N CPMAS NMR spectra of the forest litter layer showed that more than 80% of the total signal intensity was attributable to the secondary amide-peptide peak The degree of 15 N enrichment or form of N did not alter the relative intensity of signals attributable to 15 N in peptides, nucleic acids and aliphatic amine groups (amino sugars and free NH 2 on amino acids) Combinations of 13 C and 15 N-NMR spectra, edited by a process that exploited differences in proton spin properties between distinct categories of organic matter, indicated incorporation of 15 N in humified organic matter rather than partly degraded plant material This application demonstrated that solid state 15 N CPMAS NMR has potential for use in studies of N immobilization under field conditions and with materials containing little N and small 15 N enrichment

Turning Teachers on to Computers: Evaluation of a Teacher Development Program.

Abstract: This study evaluated a teacher development program designed to introduce educational uses of computers to teachers and to facilitate their integration into classroom activities. The model involved teachers in a school-based, action-research project supported by visits from resource personnel, with clusters of teachers attending two meetings to evaluate their experiences, share ideas, and discuss relevant issues. The model proved to be very successful. Dramatic increases in teacher confidence and, to a lesser extent, competence in computer use were the major outcomes. A strong commitment to continue their use of computers in their teaching was common. Teachers reported their students gaining noticeable cognitive and social benefits from the experience.