22,076 results for Journal article

  • Revision of the genus Psammocinia (Porifera: Demospongiae: Dictyoceratida), with six new species from New Zealand

    Cook, S.D.C.; Bergquist, P.R. (1998)

    Journal article
    The University of Auckland Library

    An open access copy of this article is available from the publishers website. The status of species within the dictyoceratid sponge genus Psammocinia is reviewed. The separation of Psammocinia species from the closely related Ircinia species, which has been the subject of some dispute, is clarified. This distinction made on the basis of morphological evidence is supported by the limited chemotaxonomic and molecular phylogenetic data available. Six new species of Psammocinia are described from the New Zealand region.

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  • Evidence for long-term site fidelity of snapper (Pagrus auratus) within a marine reserve

    Willis, T.J.; Parsons, D.M.; Babcock, R.C. (2001)

    Journal article
    The University of Auckland Library

    An open access copy of this article is available from the publishers website. Increases in the density of exploited species on unfished reefs logically implies that some individuals are at least temporarily resident, or show fidelity to a particular area. We tagged snapper (Pagrus auratus (Bloch & Schneider 1801)) in the Leigh Marine Reserve, New Zealand using visible implant fluorescent elastomer tags, recoverable by diver visual sightings without the need to recapture the fish. Batch tagging of snapper (n = 907) was done during an angling survey in June and December 1996, and individually coded tags were implanted by divers (n = 117) in January 1999. Snapper tagged during both programmes were recovered on irregular intervals from 1997 to 2000. There were 71 recoveries of batch tags within 500 m of their tagging sites, and these recoveries were still being made >3 years after tagging. Of individually coded fish, 49 (42%) were seen, sometimes repeatedly over several months, close to their respective tagging sites. These observations included snapper as small as 23 cm fork length, contradicting the commonly held impression that only large snapper take up long-term residency on reefs. This preliminary evidence suggests that some snapper exhibit site fidelity to areas only a few hundred metres wide, and in the absence of fishing may occupy the same area for years.

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  • Retention and in situ detectability of visible implant fluorescent elastomer (VIFE) tags in Pagrus auratus (Sparidae)

    Willis, T.J.; Babcock, R.C. (1998)

    Journal article
    The University of Auckland Library

    An open access copy of this article is available from the publishers website. This paper assesses the potential effectiveness of the visible implant fluorescent elastomer (VIFE) tagging system for identifying groups of snapper (Pagrus auratus: Sparidae) in the field. Retention rate after surface tagging longline-caught fish was 93% over a 2-week period, with no mortality attributable to tagging. Incidence of fin or scale infection did not differ between tagged and control fish. A protocol for tagging snapper underwater was also developed. This technique caused less stress to the fish than remote fishing methods, but was labour intensive when large sample sizes were required. Orange VIFE tags were visible to divers at ranges of up to 6 m in water visibility of 8-10 m, when exposed to light frequencies capable of inducing fluorescent emissions. Red, green, and yellow tags were only identifiable at shorter ranges, depending on ambient light levels and direction. The range of tag detection increased with increasing water clarity. We suggest that VIFE tagging has better retention rates and is less intrusive compared with previously employed externally readable tags. Because tags are identifiable in situ without the necessity of recapture, this method has potentially wide-ranging applications in fish ecology and behavioural studies for adult as well as juvenile fishes.

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  • New species of Spongia (Porifera: Demospongiae: Dictyoceratida) from New Zealand, and a proposed subgeneric structure

    Cook, S.D.C.; Bergquist, P.R. (2001)

    Journal article
    The University of Auckland Library

    An open access copy of this article is available from the publishers website. This paper is the fifth in a series revising the taxonomy of New Zealand dictyoceratid sponges (phylum Porifera, subclass Ceractinomorpha, order Dictyoceratida). Six new species of the genus Spongia are added to New Zealand's known fauna. The use of subgenera within the genus Spongia is discussed, and two new subgenera are proposed. The genus Hippospongia is revised, and an emended generic diagnosis is proposed.

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  • Impact of pulp and paper mill effluent on water quality and fauna in a New Zealand hydro-electric lake

    Sharples, A.D.; Evans, C.W. (1998)

    Journal article
    The University of Auckland Library

    An open access copy of this article is available from the publishers website. The Kinleith pulp and paper mill discharges effluent into the Kopakorahi ann of Lake Maraetai (New Zealand) resulting in an effluent gradient defined by the effluent visibility (Secchi disc), transmittance (465 nm), temperature, and oxygen level that is discernible at least as far down stream as the adjoining Lake Waipapa. This effluent gradient is reflected in the composition of the fauna caught in fyke nets which at the most effluent-exposed sites is dominated by goldfish (Carassius auratus) and is depauperate in pollution-sensitive species such as freshwater crayfish (Paranephrops planifrons) and trout (Salmo trutta and Oncoryhynchus mykiss). In 1991 the Kinleith mill undertook substantial process modifications which have resulted in improvements in the water quality of the discharge. Secchi disc visibilities have increased markedly at the most effluent-exposed sites since modernisation of the mill and similar improvements have been observed in light transmittance. A seasonal trend in water temperature not previously observed was recorded at the most effluent-exposed sites following modernisation, and dissolved oxygen levels at these sites rose markedly. Improvements in the water quality of the recipient since the mill modernisation are reflected in changes in the sampled fauna in particular the occurrence of trout at sites from which they were previously absent.

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  • Variability in life history characters of the Chilean oyster Tiostrea chilensis (Philippi, 1845)

    Jeffs, A.G.; Hooker, S.H.; Creese, R.G. (1997)

    Journal article
    The University of Auckland Library

    An open access copy of this article is available from the publishers website. Differences in some life history characters of the Chilean oyster, Tiostrea chilensis, were examined for three populations in the northern North Island of New Zealand. Previous studies of oyster populations in the South Island have predicted that populations at lower latitudes would produce smaller-sized larvae and substantial numbers of planktonic larvae. For only one northern population was there some evidence of the release of planktonic larvae. However, larvae from all three northern study populations were smaller in size than reported for all other locations, both in New Zealand and Chile. This was because of a trend for larval size to vary inversely with sea water temperature. The results of this study indicate that life history characters of this species can vary greatly at both the individual and population level. Furthermore, this variability does not always conform to commonly proffered life history principles which assert that planktonic development and small larvae become more common at low latitudes.

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  • Revision of Southwest Pacific Polymastiidae (Porifera: Demospongiae: Hadromerida) with descriptions of new species of Polymastia Bowerbank, Tylexocladus Topsent, and Acanthopolymastia gen. nov. from New Zealand and the Norfolk Ridge, New Caledonia

    Kelly-Borges, M.; Bergquist, P.R. (1997)

    Journal article
    The University of Auckland Library

    An open access copy of this article is available from the publishers website. Specific diagnostic characters are reviewed and redefined for the genus Polymastia in northern New Zealand waters, to provide a framework for the recognition of new species, and for the revision and redefinition of other Polymastiidae. Eight new species of Polymastia are described, and Polymastia fusca Bergquist, P. hirsuta Berquist, and P. cf. massilis Carter are redescribed in the light of new material. Species of Polymastia which contain exotyles and centrotylote oxea in addition to the usual megasclere complement, provided the opportunity to redefine the polymastid genera Proteleia, and Tylexocladus, which would typically have been reserved respectively, for sponges with these spicules. A new species of Tylexocladus is described from the Chatham Rise in southern New Zealand, providing a first record of the genus from this location. A new genus Acanthopolymastia is established for southern ocean Polymastiidae with acanthose centrotylote oxea, with Atergia acanthoxa Koltun from Antarctica as the type species. Two additional species from New Zealand and the Norfolk Ridge, New Caledonia are described, and all are compared to Atlantic species of the same genera. Suggestions for partitioning of shallow-water Polymastia species are put forward.

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  • Ecology and environmental impact of Musculista senhousia (Mollusca: Bivalvia: Mytilidae) in Tamaki Estuary, Auckland, New Zealand

    Creese, R.; Hooker, S.; De, Luca, S.; Wharton, Y. (1997)

    Journal article
    The University of Auckland Library

    An open access copy of this article is available from the publishers website. The introduced, mytilid bivalve Musculista senhousia (Asian date mussel) occurs on the east coast of New Zealand in the Auckland region. Eighteen sites were searched within the Tamaki Estuary: six had extensive mats of mussels and three contained small, isolated clumps. Core samples were taken monthly during 1994/95 from two of the mat-forming populations. Densities reached 16 000 m-2 at Bucklands Beach and 5000 m-2 at Farm Cove. Both populations were dominated by a single cohort of mussels. Mussels grew to about 20 mm in 12 months, after which growth virtually ceased. Recruitment was sporadic into existing mats, but occurred adjacent to the monitored mat at Bucklands Beach in April 1995. The area occupied by the initial mussel bed at this site decreased by 60% over 1 year. Further core sampling revealed significantly fewer macrofaunal invertebrates under mussel mats compared to control samples taken from areas of beach without mussels. Infaunal bivalves were most adversely affected by M. senhousia, showing an 8-fold decrease in abundance within mats compared to cores in the control area. Our results reveal that M. senhousia in the Auckland area has similar life history features to those reported from populations outside New Zealand. We suggest that any adverse environmental effects caused by M. senhousia are likely to be local and short-lived.

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  • Reproductive periodicity in Evechinus chloroticus in the Hauraki Gulf.

    Walker, M.M. (1982)

    Journal article
    The University of Auckland Library

    Gametogenesis began in the spring, and major spawning occurring in mid to late summer. The proportion of the gonads taken up by nutritive phagocyte cells increased from autumn to spring. During proliferation and growth of gametes and nutritive phagocytes declined in abundance and globulation, suggesting that reserves stored in these cells were transferred to developing gametes. Although synchronous gametogenesis occurred in the 3 populations studied, spawning occurred at different times, which suggests that spawning was induced by factors acting either within sea urchin populations or over distances of a few km or less.-

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  • Artificial nest box use by the North Island saddleback: Effects of nest box design and mite infestations on nest site selection and reproductive success

    Stamp R.K.; Brunton D.H.; Walter B. (2002)

    Journal article
    The University of Auckland Library

    An open access copy of this article is available from the publishers website. The importance of artificial nest boxes for North Island saddlebacks (Philesturnus carunculatus rufusater) on Tiritiri Matangi Island has increased significantly, suggesting that "natural" nesting cavities are now a limited resource for this growing population. The design and position of artificial nest boxes directly affects the likelihood of saddleback use for nesting: small boxes (0.005 and 0.01 m3) with large (140-160 mm high) north facing openings had the highest probability of being used. One of the disadvantages of using artificial nest boxes in conservation management is the potential for parasite build-up. Two species of mesostigmatid mites were found in the artificial nest boxes used by saddlebacks on Tiritiri Matangi Island. One was an undescribed species of Dermanyssid mite the other was Ornithonyssus bursa, the fowl mite. The numbers of mites detected increased over the saddleback nesting cycle from September to December. However, our results strongly suggest that, for saddlebacks, no negative correlations exist between mite abundance and chick weight, fledging date, or the number of fledglings produced. Mite abundance was extremely variable and did not correlate with nest box temperature or relative humidity.

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  • Bird and rat numbers on little barrier island, New Zealand, over the period of cat eradication 1976-80

    Girardet S.A.B.; Veitch C.R.; Craig J.L. (2001)

    Journal article
    The University of Auckland Library

    An open access copy of this article is available from the publishers website. Passerines were monitored on Little Barrier Island over 15 years (1975-89) spanning the period (1976-80) when feral cats were eradicated from the island. All birds seen and heard were recorded while walking three transects representing an altitudinal range from near sea level to approximately 550 m above sea level. Analysis of variance statistics were used to test for differences in bird numbers between transects and between years. Bird species were examined by transect to test for changes in numbers over time. Three species had increased on some transects, and two species had decreased on some transects, but it was difficult to attribute changes in bird numbers to the one cause which we were able to study: Reduced cat numbers. Examination of numbers of individuals of 14 species recorded between transects showed significant differences for some individual species, but not for all species grouped together. Four species did not show any significant differences between transects. This study demonstrates different patterns in bird distributions on Little Barrier Island which cannot be understood from these data. Index traplines were set for Pacific rats or kiore (Rattus exulans) between 1977 and 1984, before and after cat eradication. Rat numbers fluctuated widely, and there were no significant differences that could be attributed to the changes in cat numbers.

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  • Tuatara (Sphenodon punctatus) feeding ecology in the presence of kiore (Rattus exulans)

    Ussher G.T. (1999)

    Journal article
    The University of Auckland Library

    An open access copy of this article is available from the publishers website. The diet of tuatara was investigated on kiore-inhabited Lady Alice Island in the Hen and Chickens Group, northern New Zealand, between 1993 and 1994. Both dietary (targeted) and inedible (incidental) items were eaten by tuatara. Dietary items recorded were exclusively invertebrate in origin. Estimates of environmental availability of invertebrates and indicated that the prey consumed were strongly selected by size and by taxa. Beetles, insect larvae, arachnids and weta comprised the greatest proportion of total diet, appeared in the greatest number of stomachs and were taken in excess of their abundance. Most prey were >10 mm in length, despite an abundance of smaller prey in the environment. The risk of predation by tuatara was greatest for terrestrial invertebrates and least for arboreal species. The composition of diets by habitat was largely similar between mid-successional kanuka (Kunzea ericoides) and late successional mixed broadleaf forest. The size distribution of prey eaten by tuatara in kanuka habitat during autumn, and the low number of tuatara yielding dietary samples, are discussed in terms of food competition with kiore. Overall, the foraging behaviour of tuatara was not obviously different on rodent-free compared to kiore-inhabited islands, either indicating that food competition is insufficient to influence diet, or that tuatara are unable to change their feeding behaviour under a higher degree of competitive pressure for prey items. Clear support for either hypothesis is lacking.

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  • Origin of oscillatory convection in a porous medium heated from below

    Horne, R.N.; O'Sullivan, M.J. (1978)

    Journal article
    The University of Auckland Library

    An open access copy of this article is available and complies with the copyright holder/publisher conditions. In order to investigate the significance of cyclic interaction in the evolution of fluctuating convective flow in a rectangular cell of porous material, the behavior of confined and unconfined flows are compared. In the latter case the constant pressure boundary condition at the top surface does not force the fluid to recirculate around the cell. However, regular oscillatory flow similar to that which occurs in an enclosed cell is still observed. This indicates that the oscillatory flow arises from the instability of the thermal boundary layer on the heated bottom surface. In both cases the frequency of the oscillatory flow is proportional to the Rayleigh number to the power of 3/2.

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  • Nonlinear trans-resonant waves, vortices and patterns: From microresonators to the early universe

    Galiev, Sh.U.; Galiyev, T.Sh. (2001)

    Journal article
    The University of Auckland Library

    An open access copy of this article is available and complies with the copyright holder/publisher conditions. Perturbed wave equations are considered. Approximate general solutions of these equations are constructed, which describe wave phenomena in different physical and chemical systems. Analogies between surface waves, nonlinear and atom optics, field theories and acoustics of the early Universe can be seen in the similarities between the general solutions that govern each system. With the help of the general solutions and boundary conditions and/or resonant conditions we have derived the basic highly nonlinear ordinary differential equation or the basic algebraic equation for traveling waves. Then, approximate analytic resonant solutions are constructed, which describe the trans-resonant transformation of harmonic waves into traveling shock-, jet-, or mushroom-like waves. The mushroom-like waves can evolve into cloud-like and vortex-like structures. The motion and oscillations of these waves and structures can be very complex. Under parametric excitation these waves can vary their velocity, stop, and change the direction of their motion. Different dynamic patterns are yielded by these resonant traveling waves in the x-t and x-y planes. They simulate many patterns observed in liquid layers, optical systems, superconductors, Bose - Einstein condensates, micro-and electron resonators. The harmonic excitation may be compressed and transformed inside the resonant band into traveling or standing particle-like waves. The area of application of these solutions and results may possibly vary from the generation of nuclear particles, acoustical turbulence, and catastrophic seismic waves to the formation of galaxies and the Universe. In particular, the formation of galaxies and galaxy clusters may be connected with nonlinear and resonant phenomena in the early Universe.

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  • A point-charge model for the nuclear quadrupole moment: Coupled-cluster, Dirac-Fock, Douglas-Kroll, and nonrelativistic Hartree-Fock calculations for the Cu and F electric field gradients in CuF

    Pernpointner, M.; Seth, M.; Schwerdtfeger, P. (1998)

    Journal article
    The University of Auckland Library

    An open access copy of this article is available and complies with the copyright holder/publisher conditions. A point charge model for the nuclear quadrupole moment tensor (PCNQM) is developed in order to determine accurate electric field gradients (EFG) at the relativistic and correlated levels. The symmetric s contributions arising from the Poisson equation are avoided by using an appropriate point charge distribution in three-dimensional space. It is shown that the PCNQM model yields virtually the same EFGs compared to the conventional method of expectation values, if the point charges are set at small displacements from the nucleus (d<10-13 m) and the SCF energy is converged out to 12 significant figures. We further demonstrate that the choice of the point charge ? is not very critical to the PCNQM perturbation, and that the correlation energy at both the nonrelativistic and relativistic level of theory depends linearly on ?. This suggests that accurate EFG tensors can be obtained by performing only two correlated calculations for each atom and tensor component. The PCNQM model is tested on one-electron atoms and on the Cu and F EFG in CuF Relativistic and correlation effects on EFGs are discussed in detail. A Z-expansion on one-electron systems demonstrates that the relativistic correction scales ?Z5. For the CuF molecule Douglas-Kroll and Dirac-Fock coupled cluster calculations are in good agreement with each other. At the best level of theory (coupled cluster Dirac-Fock plus correction from basis set incompleteness) we obtain a nuclear quadrupole coupling constant for 63Cu of 23 Mhz. This is in very good agreement with the experimental result of 22 MHz considering the large standard deviation of the 63Cu nuclear quadrupole moment applied, 220(10) mb.

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  • The chemistry of superheavy elements. III. Theoretical studies on element 113 compounds

    Seth, M.; Schwerdtfeger, P.; Faegri, K. (1999)

    Journal article
    The University of Auckland Library

    An open access copy of this article is available and complies with the copyright holder/publisher conditions. The chemistry of element 113 is investigated by theoretical methods. The results of fully relativistic calculations for (113)H and (113)F are compared with those derived by other techniques to obtain an indication of the accuracy of the more approximate models as well as the importance of including scalar and/or spin-orbit relativistic effects. Both of these effects are found to be important. The spin-orbit coupled pseudopotential approximation yields results of satisfactory accuracy, but the two relativistic methods that do not include spin-orbit coupling (Douglas-Kroll and scalar relativistic pseudopotential method) do not agree so well with each other. The calculated properties of (113)H and (113)F and a number of other hydrides and halides of element 113 are compared with the properties of the equivalent compounds of the lighter group 13 elements. In general, element 13 exhibits behavior that is consistent with its placement in group 13 of the periodic table. Some of its properties are found to be somewhat unusual however, e.g., the element is relatively electronegative, the molecules (113)H3, (113)F3, and (113)C13 are predicted to be T-shaped rather than trigonal planar, and the 6d electrons of element 113 participate to a significant extent in chemical bonding. Compounds where element 113 is present in the +5 oxidation state are considered as well but are predicted to be thermodynamically unstable.

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  • The direct Monte Carlo method applied to the homogeneous nucleation problem

    Hettema, H.; McFeaters, J.S. (1996)

    Journal article
    The University of Auckland Library

    An open access copy of this article is available and complies with the copyright holder/publisher conditions. We discuss the application of the direct Monte Carlo method to the theory of cluster formation. Fractal relationships for the kernels appearing in the Smoluchowski equation are implemented in this method and the scaling behavior of the kernels is investigated using computer simulation. We study the effects of cluster disintegrations and also investigate the effects of "magic" numbers in cluster formation.

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  • Unequal mass spinor-spinor Bethe-Salpeter equation

    Brennan, B.J. (1974)

    Journal article
    The University of Auckland Library

    An open access copy of this article is available and complies with the copyright holder/publisher conditions. Coupled radial equations are derived for the ladder approximation Bethe-Salpeter equation describing a system of two spin-(1/2) particles of unequal masses interacting to form a bound state of total mass zero. The numerical behavior of the coupling parameter ? as a function of the mass ratio is examined for known analytical equal-mass solutions. In addition a perturbation method is employed to investigate the behavior of ? for small values of the exchange mass. Copyright

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  • Tunnel diode-transistor binary scaler

    Tan, Z.C.; Maxwell, P.C. (1968)

    Journal article
    The University of Auckland Library

    An open access copy of this article is available and complies with the copyright holder/publisher conditions. This paper describes a new type of tunnel diode-transistor binary scaler which is very simple in concept and in design. It is capable of operating reliably at input pulse repetition rates in excess of 200 MHz. A significant feature of the scaler is that there is no maximum input pulse width restriction. Input and output circuits which allow the scaler to operate over a wide range of input driving conditions and to be cascaded directly with similar scalers are also presented.

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  • Tunnel diode-transistor twisted ring counter

    Tan, Z.C. (1969)

    Journal article
    The University of Auckland Library

    An open access copy of this article is available and complies with the copyright holder/publisher conditions. A new tunnel diode-transistor twisted ring counter is described. Each stage of the counter consists of a tunnel diode controlling a long tailed pair which switches current into the following stage. Rectangular input pulses are "differentiated" by a shorted delay cable and the tunnel diodes are progressively switched to high voltage states by the positive pulses and then progressively reverse switched to low voltage states by the negative pulses. The scaling capacity of the counter for rectangular input pulses is (2n-1) where n is the number of stages. A maximum scaling rate of 450 MHz was observed for a practical three stage quinary counter.

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