365 research outputs found
Australian national residue survey â closing the loop on pesticide residue risk management for Australian grain
Australia exports a major proportion of its agricultural production and is highly dependent on maintaining and developing access to, and competitiveness in, export markets. To preserve Australiaâs status as a provider of high quality grain, the majority of Australian primary producers rely on pesticides to protect their crops from pests and diseases, particularly in post-harvest situations. The Australian Pesticides and Veterinary Medicines Authority (APVMA) supports Australian agriculture by registering and allowing the supply of safe and effective animal health and crop protection products. A residue risk management continuum is established when the effectiveness of chemical registration and control of chemical use regulations is assessed through residue monitoring programs. Programs assess good agricultural practice and provide traceback capacity to investigate areas of concern. Risk communication provides opportunities for continuous improvement. In the early 1960s, the Australian Government established a non-regulatory body, the national residue survey (NRS). In 2008-2009, random monitoring programs were conducted for over 50 commodities (21 grains, five horticultural commodities, 11 fish species, 12 animal species, honey and egg with over 20,000 samples collected for analytical testing. The NRS grain residue monitoring program is presented as a case study of the residue risk management continuum demonstrating to overseas markets the high level of residue integrity of Australian grain. Over 4,000 grain samples are collected and analysed per annum. Most of the samples are collected in the bulk export program where samples are collected from every hatch of every ship loaded at the seventeen Australian grain export terminals. The chemical screens have expanded beyond the multi-residue screen (MRS) insecticides, fungicides and herbicides, to include phosphine, additional herbicides (not included in the MRS), heavy metals and mycotoxins. In its current form, the NRS grains program provides 15 years of residue testing data which demonstrates a very high degree of conformance with Australian MRLs and the import tolerances of overseas trading partners. In addition, trends in residue testing data demonstrate a decline in the frequency of residue detections and the levels of residue detected. To be confident that residue testing results meet the requisite standards, the reliability of the Australian analyses must be assured. The NRS laboratory performance evaluation system has been developed to provide that assurance, using a range of proficiency tests and other techniques in the selection of laboratories for NRS work. Residue testing results are reported against both Australian MRLs and the international MRLs which apply in the relevant export market. NRS maintains databases of overseas MRLs and compares its residue testing results of exported commodities against those standards. Grain marketers receive certificates of analysis, in the form of NRS residue testing results, for each shipment prior to arrival at the overseas market.Keywords: Grain, Pesticide, residue, monitoring program, residue risk managemen
Apolarity, Hessian and Macaulay polynomials
A result by Macaulay states that an Artinian graded Gorenstein ring R of
socle dimension one and socle degree b can be realized as the apolar ring of a
homogeneous polynomial f of degree b. If R is the Jacobian ring of a smooth
hypersurface g=0, then b is just equal to the degree of the Hessian polynomial
of g. In this paper we investigate the relationship between f and the Hessian
polynomial of g.Comment: 12 pages. Improved exposition, minor correction
The neutron halo of He in a microscopic model
The two--neutron separation energy of He has been reproduced for the
first time in a realistic parameter--free microscopic multicluster model
comprising the and clusterizations, with cluster
breathing excitations included. The contribution of the channel is
substantial. A very thick (0.85 fm) neutron halo has been found in full
agreement with the results of the latest phenomenological analysis.Comment: Submitted to Phys. Rev. C, 8 pages, Latex with Revtex, 2 figures (not
included) available on request, 08-03-9
Total Photoabsorption Cross Sections of A=6 Nuclei with Complete Final State Interaction
The total photoabsorption cross sections of 6He and 6Li are calculated
microscopically with full inclusion of the six-nucleon final state interaction
using semirealistic nucleon-nucleon potentials. The Lorentz Integral Transform
(LIT) method and the effective interaction approach for the hyperspherical
formalism are employed. While 6Li has a single broad giant resonance peak,
there are two well separated peaks for 6He corresponding to the breakup of the
neutron halo and the alpha core, respectively. The comparison with the few
available experimental data is discussed.Comment: LaTeX, 8 pages, 3 ps figure
Comment on ``Large-space shell-model calculations for light nuclei''
In a recent publication Zheng, Vary, and Barrett reproduced the negative
quadrupole moment of Li-6 and the low-lying positive-parity states of He-5 by
using a no-core shell model. In this Comment we question the meaning of these
results by pointing out that the model used is inadequate for the reproduction
of these properties.Comment: Latex with Revtex, 1 postscript figure in separate fil
Searching for three-nucleon resonances
We search for three-neutron resonances which were predicted from pion double
charge exchange experiments on He-3. All partial waves up to J=5/2 are
nonresonant except the J=3/2^+ one, where we find a state at E=14 MeV energy
with 13 MeV width. The parameters of the mirror state in the three-proton
system are E=15 MeV and Gamma=14 MeV. The possible existence of an excited
state in the triton, which was predicted from a H(He-6,alpha) experiment, is
also discussed.Comment: LaTex with RevTe
Occupation probability of harmonic-oscillator quanta for microscopic cluster-model wave functions
We present a new and simple method of calculating the occupation probability
of the number of total harmonic-oscillator quanta for a microscopic
cluster-model wave function. Examples of applications are given to the recent
calculations including -model for He, -model for
Li, and -model for Be as well as the classical
calculations of -model for Li and -model
for C. The analysis is found to be useful for quantifying the amount of
excitations across the major shell as well as the degree of clustering. The
origin of the antistretching effect is discussed.Comment: 9 page
Indications for the Nonexistence of Three-Neutron Resonances near the Physical Region
The pending question of the existence of three-neutron resonances near the
physical energy region is reconsidered. Finite rank neutron-neutron forces are
used in Faddeev equations, which are analytically continued into the unphysical
energy sheet below the positive real energy axis. The trajectories of the
three-neutron S-matrix poles in the states of total angular momenta and parity
J^\pi=1/2 +- and J^\pi= 3/2 +- are traced out as a function of artificial
enhancement factors of the neutron-neutron forces. The final positions of the
S-matrix poles removing the artificial factors are found in all cases to be far
away from the positive real energy axis, which provides a strong indication for
the nonexistence of nearby three-neutron resonances. The pole trajectories
close to the threshold E=0 are also predicted out of auxiliary generated
three-neutron bound state energies using the Pad\'e method and agree very well
with the directly calculated ones.Comment: 20 pages, 7 Postscript figures, fig.1 is corrected, uses relax.st
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