10,240 research outputs found

    Effect of grazing on ship rat density in forest fragments of lowland Waikato, New Zealand

    Get PDF
    Ship rat (Rattus rattus) density was assessed by snap-trapping during summer and autumn in eight indigenous forest fragments (mean 5 ha) in rural landscapes of Waikato, a lowland pastoral farming district of the North Island, New Zealand. Four of the eight were fenced and four grazed. In each set of four, half were connected with hedgerows, gullies or some other vegetative corridor to nearby forest and half were completely isolated. Summer rat density based on the number trapped in the first six nights was higher in fenced (mean 6.5 rats ha–1) than in grazed fragments (mean 0.5 rats ha–1; P = 0.02). Rats were eradicated (no rats caught and no rat footprints recorded for three consecutive nights) from all eight fragments in January–April 2008, but reinvaded within a month; time to eradication averaged 47 nights in fenced and 19 nights in grazed fragments. A second six-night trapping operation in autumn, 1–3 months after eradication, found no effect of fencing (P = 0.73). Connectedness to an adjacent source of immigrants did not influence rat density within a fragment in either season (summer P = 0.25, autumn P = 0.67). An uncalibrated, rapid (one-night) index of ship rat density, using baited tracking tunnels set in a 50 × 50 m grid, showed a promising relationship with the number of rats killed per hectare over the first six nights, up to tracking index values of c. 30% (corresponding to c. 3–5 rats ha–1). The index will enable managers to determine if rat abundance is low enough to achieve conservation benefits. Our results confirm a dilemma for conservation in forest fragments. Fencing protects vegetation, litter and associated ecological processes, but also increases number of ship rats, which destroy seeds, invertebrates and nesting birds. Maximising the biodiversity values of forest fragments therefore requires both fencing and control of ship rats

    Observation of soliton explosions in a passively mode-locked fiber laser

    Full text link
    Soliton explosions are among the most exotic dissipative phenomena studied in mode-locked lasers. In this regime, a dissipative soliton circulating in the laser cavity experiences an abrupt structural collapse, but within a few roundtrips returns to its original quasi-stable state. In this work we report on the first observation of such events in a fiber laser. Specifically, we identify clear explosion signatures in measurements of shot-to-shot spectra of an Yb-doped mode-locked fiber laser that is operating in a transition regime between stable and noise-like emission. The comparatively long, all-normal-dispersion cavity used in our experiments also permits direct time-domain measurements, and we show that the explosions manifest themselves as abrupt temporal shifts in the output pulse train. Our experimental results are in good agreement with realistic numerical simulations based on an iterative cavity map.Comment: 5 pages, 5 figures, submitte

    The NGC 5846 Group: Dynamics and the Luminosity Function to M_R=-12

    Full text link
    We conduct a photometric and spectroscopic survey of a 10 sq. deg. region surrounding the nearby NGC 5846 group of galaxies, using the Canada-France-Hawaii and Keck I telescopes to study the population of dwarf galaxies as faint as M_R=-10. Candidates are identified on the basis of quantitative surface brightness and qualitative morphological criteria. Spectroscopic follow up and a spatial correlation analysis provide the basis for affirming group memberships. Altogether, 324 candidates are identified and 83 have spectroscopic membership confirmation. We argue on statistical grounds that a total 251 +/- 10 galaxies in our sample are group members. The observations, together with archival Sloan Digital Sky Survey, ROSAT, XMM-Newton, and ASCA data, suggest that the giant ellipticals NGC 5846 and NGC 5813 are the dominant components of subgroups separated by 600 kpc in projection and embedded in a 1.6 Mpc diameter dynamically evolved halo. The galaxy population is overwhelmingly early type. The group velocity dispersion is 322 km/s, its virial mass is 8.4 x 10^13 M_sun, and M/L_R = 320 M_sun/L_sun. The ratio of dwarfs to giants is large compared with other environments in the Local Supercluster studied and, correspondingly, the luminosity function is relatively steep, with a faint end Schechter function slope of \alpha_d = -1.3 +/- 0.1 (statistical) +/- 0.1 (systematic) at our completeness limit of M_R = -12.Comment: 17 pages; accepted for publication in the Astronomical Journa

    CO-OPERATING TO COMPETE IN HIGH VELOCITY GLOBAL MARKETS: THE STRATEGIC ROLE OF FLEXIBLE SUPPLY CHAIN ARCHITECTURES

    Get PDF
    Continued value creation is paramount for the survival of firms competing in today's high velocity global business environment. This paper presents a conceptual framework for understanding how firms can create and capture value within a highly volatile and uncertain business environment by exploiting both performance gaps and opportunity gaps through the development and use of flexible supply chain architectures. The choice of flexible organizational architecture allows for the continued reconfiguration of the independent modular components of the supply chain so as to achieve optimal leverage of both the firms core competencies as well as their collaborative partners complementary resources. The case of Cellars of Canterbury, a New Zealand based International wine marketing and distribution cooperative enterprise provides empirical support.Industrial Organization, International Relations/Trade,

    CO-OPERATING TO COMPETE IN HIGH VELOCITY GLOBAL MARKETS: THE STRATEGIC ROLE OF FLEXIBLE SUPPLY CHAIN ARCHITECTURES

    Get PDF
    Continued value creation is paramount for the survival of firms competing in today's high velocity global business environment. This paper presents a conceptual framework for understanding how firms can create and capture value within a highly volatile and uncertain business environment by exploiting both performance gaps and opportunity gaps through the development and use of flexible supply chain architectures. The choice of flexible organizational architecture allows for the continued reconfiguration of the independent modular components of the supply chain so as to achieve optimal leverage of both the firms core competencies as well as their collaborative partners complementary resources. The case of "Cellars of Canterbury," a New Zealand based International wine marketing and distribution cooperative enterprise provides empirical support. Keywords: value creation, flexible supply chain architectures, leverage, core competencies.value creation, flexible supply chain architectures, leverage, core competencies., Industrial Organization, Marketing,

    Monitoring sediment transfer processes on the desert margin

    Get PDF
    LANDSAT Thematic Mapper and Multispectral Scanner data have been used to construct change detection images for three playas in south-central Tunisia. Change detection images have been used to analyze changes in surface reflectance and absorption between wet and dry season (intra-annual change) and between different years (inter-annual change). Change detection imagery has been used to examine geomorphological changes on the playas. Changes in geomorphological phenomena are interpreted from changes in soil and foliar moisture levels, differences in reflectances between different salt and sediments and the spatial expression of geomorphological features. Intra-annual change phenomena that can be detected from multidate imagery are changes in surface moisture, texture and chemical composition, vegetation cover and the extent of aeolian activity. Inter-annual change phenomena are divisible into those restricted to marginal playa facies (sedimentation from sheetwash and alluvial fans, erosion from surface runoff and cliff retreat) and these are found in central playa facies which are related to the internal redistribution of water, salt and sediment

    Effects of pore modification on the templating of guest molecules in a 2D honeycomb network

    Get PDF
    This work was supported by the UK Engineering Physical Sciences Research Council (EPRSC) and the EU.1,7-Diadamantanethioperylene-3,4:9,10-tetracarboxylic diimide, (Ad-S)(2)-PTCDI, adsorbed on Au (111) from solution was investigated by scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). (Ad-S)(2)-PTCDI forms a well-ordered monolayer whose structure is described by a (2 root 63 x root 19) R19.1 degrees chiral unit cell containing four molecules. Codeposition of (Ad-S)(2)-PTCDI with 1,3,5-triazine-2,4,6-triamine (melamine) yields a honeycomb network whose (7 root 3 x 7 root 3)R30 degrees unit cell is identical to the unsubstituted PTCDI/melamine analogue. The effect of the adamantyl thioether moieties on the adsorption of guest molecules is investigated using adamantane thiol and C-60. While the thioether units do not affect the packing of adamantane thiol molecules a pronounced influence is seen in the case of fullerene. Pore modification involving different combinations of enantiomers of (Ad-S)(2)-PTCDI give rise to distinctly different arrangements of C-60 molecules. The diversity of patterns is further increased by the presence of unsubstituted PTCDI molecules.PostprintPeer reviewe

    Low-Energy Effective Theory, Unitarity, and Non-Decoupling Behavior in a Model with Heavy Higgs-Triplet Fields

    Get PDF
    We discuss the properties of a model incorporating both a scalar electroweak Higgs doublet and an electroweak Higgs triplet. We construct the low-energy effective theory for the light Higgs-doublet in the limit of small (but nonzero) deviations in the rho parameter from one, a limit in which the triplet states become heavy. For small deviations in the rho parameter from one, perturbative unitarity of WW scattering breaks down at a scale inversely proportional to the renormalized vacuum expectation value of the triplet field (or, equivalently, inversely proportional to the square-root of the deviation of the rho parameter from one). This result imposes an upper limit on the mass-scale of the heavy triplet bosons in a perturbative theory; we show that this upper bound is consistent with dimensional analysis in the low-energy effective theory. Recent articles have shown that the triplet bosons do not decouple, in the sense that deviations in the rho parameter from one do not necessarily vanish at one-loop in the limit of large triplet mass. We clarify that, despite the non-decoupling behavior of the Higgs-triplet, this model does not violate the decoupling theorem since it incorporates a large dimensionful coupling. Nonetheless, we show that if the triplet-Higgs boson masses are of order the GUT scale, perturbative consistency of the theory requires the (properly renormalized) Higgs-triplet vacuum expectation value to be so small as to be irrelevant for electroweak phenomenology.Comment: Revtex, 11 pages, 7 eps figures included; references updated and three footnotes adde
    corecore