456 research outputs found
Modelling the impact of policies to reduce environmental impacts in the New Zealand dairy sector
Agriculture remains a major sector of the New Zealand economy, with the vast majority of farm and food production exported. The accelerating intensification of farming in New Zealand over recent decades raises concern over the current sustainability of New Zealand farming, and whether it can remain so in the future. In this study, we focus on the impacts of policies to reduce environmental impacts of dairy farming, with a particular focus on nitrogen pollution and greenhouse gases (GHG) emissions. We use a modified version of the Global Trade Analysis Project (GTAP) model and database, with improved specification of the agricultural sector and land-use. We augment the model with environmental indicators for New Zealand, including nitrogen balances and GHG emissions.
We simulate a range of scenarios involving reductions in fertiliser use and stocking rates on dairy farms, from an updated 2010 database. In particular, we consider seven scenarios, with the objective of exploring reductions in the dairy stocking rate and the application of nitrogenous fertiliser to dairy farms to target reductions in the dairy sector’s nitrogen balance of 10%, 20% and 30%. Reducing fertiliser use and stocking rates are two of the approaches that dairy farmers can take in order to reduce their emissions of nitrogen and GHGs. Our results suggest that the nitrogen balance could be reduced by 10% with a 16% cut in nitrogenous fertiliser and a 5% fall in the stocking rate. Reducing fertiliser use and stocking rate by 31% and 11% respectively could result in a 20% cut to the dairy sector’s nitrogen balance. To achieve a 30% reduction in the nitrogen balance, our results suggest that the cut back in fertiliser use would need to be 45%, with the stocking rate reduced by 19%. Across these scenarios, our results indicate that value added in the dairy farm sector could fall by between 2% and 13%, while export earnings from dairy products may fall by between US1,145 million
Retromer controls planar polarity protein levels and asymmetric localization at intercellular junctions
The coordinated polarization of cells in the plane of a tissue, termed planar polarity, is a characteristic feature of epithelial tissues [1]. In the fly wing, trichome positioning is dependent on the core planar polarity proteins adopting asymmetric subcellular localizations at apical junctions, where they form intercellular complexes that link neighboring cells [1-3]. Specifically, the seven-pass transmembrane protein Frizzled and the cytoplasmic proteins Dishevelled and Diego localize to distal cell ends, the four-pass transmembrane protein Strabismus and the cytoplasmic protein Prickle localize proximally, and the seven-pass transmembrane spanning atypical cadherin Flamingo localizes both proximally and distally. To establish asymmetry, these core proteins are sorted from an initially uniform distribution; however, the mechanisms underlying this polarized trafficking remain poorly understood. Here, we describe the identification of retromer, a master controller of endosomal recycling [4-6], as a key component regulating core planar polarity protein localization in Drosophila. Through generation of mutants, we verify that loss of the retromer-associated Snx27 cargo adaptor, but notably not components of the Wash complex, reduces junctional levels of the core proteins Flamingo and Strabismus in the developing wing. We establish that Snx27 directly associates with Flamingo via its C-terminal PDZ binding motif, and we show that Snx27 is essential for normal Flamingo trafficking. We conclude that Wash-independent retromer function and the Snx27 cargo adaptor are important components in the endosomal recycling of Flamingo and Strabismus back to the plasma membrane and thus contribute to the establishment and maintenance of planar polarization
Gaussian random waves in elastic media
Similar to the Berry conjecture of quantum chaos we consider elastic analogue
which incorporates longitudinal and transverse elastic displacements with
corresponding wave vectors. Based on that we derive the correlation functions
for amplitudes and intensities of elastic displacements. Comparison to numerics
in a quarter Bunimovich stadium demonstrates excellent agreement.Comment: 4 pages, 4 figure
The Mersey Estuary : sediment geochemistry
This report describes a study of the geochemistry of
the Mersey estuary carried out between April 2000 and
December 2002. The study was the first in a new programme
of surveys of the geochemistry of major British estuaries
aimed at enhancing our knowledge and understanding of the
distribution of contaminants in estuarine sediments.
The report first summarises the physical setting, historical
development, geology, hydrography and bathymetry of the
Mersey estuary and its catchment. Details of the sampling
and analytical programmes are then given followed by a
discussion of the sedimentology and geochemistry. The
chemistry of the water column and suspended particulate
matter have not been studied, the chief concern being with
the geochemistry of the surface and near-surface sediments
of the Mersey estuary and an examination of their likely
sources and present state of contamination
Fractional Klein-Kramers equation for superdiffusive transport: normal versus anomalous time evolution in a differential L{\'e}vy walk model
We introduce a fractional Klein-Kramers equation which describes
sub-ballistic superdiffusion in phase space in the presence of a
space-dependent external force field. This equation defines the differential
L{\'e}vy walk model whose solution is shown to be non-negative. In the velocity
coordinate, the probability density relaxes in Mittag-Leffler fashion towards
the Maxwell distribution whereas in the space coordinate, no stationary
solution exists and the temporal evolution of moments exhibits a competition
between Brownian and anomalous contributions.Comment: 4 pages, REVTe
Growth in densely populated Asia: implications for primary product exporters
Economic growth and integration in Asia is rapidly increasing the global economic importance of the region. To the extent that this growth continues and is strongest in natural resource-poor Asian economies, it will add to global demand for imports of primary products, to the benefit of (especially nearby) resource-abundant countries. How will global production, consumption and trade patterns change by 2030 in the course of such economic developments and structural changes? We address this question using the GTAP model and Version 8.1 of the 2007 GTAP database, together with supplementary data from a range of sources, to support projections of the global economy from 2007 to 2030 under various scenarios. Factor endowments and real gross domestic product are assumed to grow at exogenous rates, and trade-related policies are kept unchanged to generate a core baseline, which is compared with an alternative slower growth scenario. We also consider the impact of several policy changes aimed at increasing China's agricultural self-sufficiency relative to the 2030 baseline. Policy implications for countries of the Asia-Pacific region are drawn out in the final section
A new class of semiclassical wave function uniformizations
We present a new semiclassical technique which relies on replacing
complicated classical manifold structure with simpler manifolds, which are then
evaluated by the usual semiclassical rules. Under circumstances where the
original manifold structure gives poor or useless results semiclassically the
replacement manifolds can yield remarkable accuracy. We give several working
examples to illustrate the theory presented here.Comment: 12 pages (incl. 12 figures
Charge Fluctuation Forces Between Stiff Polyelectrolytes in Salt Solution: Pairwise Summability Re-examined
We formulate low-frequency charge-fluctuation forces between charged
cylinders - parallel or skewed - in salt solution: forces from dipolar van der
Waals fluctuations and those from the correlated monopolar fluctuations of
mobile ions. At high salt concentrations forces are exponentially screened. In
low-salt solutions dipolar energies go as or ; monopolar
energies vary as or , where is the minimal separation
between cylinders. However, pairwise summability of rod-rod forces is easily
violated in low-salt conditions. Perhaps the most important result is not the
derivation of pair potentials but rather the demonstration that some of these
expressions may not be used for the very problems that originally motivated
their derivation.Comment: 8 pages and 1 fig in ps forma
Calculation of atomic spontaneous emission rate in 1D finite photonic crystal with defects
We derive the expression for spontaneous emission rate in finite
one-dimensional photonic crystal with arbitrary defects using the effective
resonator model to describe electromagnetic field distributions in the
structure. We obtain explicit formulas for contributions of different types of
modes, i.e. radiation, substrate and guided modes. Formal calculations are
illustrated with a few numerical examples, which demonstrate that the
application of effective resonator model simplifies interpretation of results.Comment: Cent. Eur. J. Phys, in pres
Normal modes of a small gamelan gong
© 2014 Acoustical Society of America. Studies have been made of the normal modes of a 20.7 cm diameter steel gamelan gong. A finite-element model has been constructed and its predictions for normal modes compared with experimental results obtained using electronic speckle pattern interferometry. Agreement was reasonable in view of the lack of precision in the manufacture of the instrument. The results agree with expectations for an axially symmetric system subject to small symmetry breaking. The extent to which the results obey Chladni's law is discussed. Comparison with vibrational and acoustical spectra enabled the identification of the small number of modes responsible for the sound output when played normally. Evidence of non-linear behavior was found, mainly in the form of subharmonics of true modes. Experiments using scanning laser Doppler vibrometry gave satisfactory agreement with the other methods
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