3,373 research outputs found
Modelling Urine Nitrogen Production and Leaching Losses for Pasture-Based Dairying Systems
Urine from dairy cattle grazing pastures with high crude protein (CP) concentrations is a major source of N lost in drainage water from New Zealand farms. This paper provides predictions of urinary N leaching losses for a range of stocking rates and levels of supplementation
Isolation and identification of Aspergillus spp. from brown kiwi (Apteryx mantelli) nocturnal houses in New Zealand
Aspergillosis, a disease caused by infection with Aspergillus spp., is a common cause of death in birds globally and is an irregular cause of mortality of captive kiwi (Apteryx spp.). Aspergillus spp. are often present in rotting plant material, including the litter and nesting material used for kiwi in captivity. The aim of this study was to survey nocturnal kiwi houses in New Zealand to assess the levels of Aspergillus currently present in leaf litter. Samples were received from 11 nocturnal kiwi houses from throughout New Zealand, with one site supplying multiple samples over time. Aspergillus was isolated and quantified by colony counts from litter samples using selective media and incubation temperatures. Isolates were identified to the species level by amplification and sequencing of ITS regions of the ribosomal. Aspergillus spp. were recovered from almost every sample; however, the levels in most kiwi houses were below 1000 colony-forming units (CFU)/g of wet material. The predominant species was Aspergillus fumigatus, with rare occurrences of Aspergillus niger, Aspergillus nidulans, and Aspergillus parasiticus. Only one site had no detectable Aspergillus. The limit of detection was around 50 CFU/g wet material. One site was repeatedly sampled as it had a high loading of A. fumigatus at the start of the survey and had two recent clinical cases of aspergillosis diagnosed in resident kiwi. Environmental loading at this site with Aspergillus spp. reduced but was not eliminated despite changes of the litter. The key finding of our study is that the background levels of Aspergillus spores in kiwi nocturnal houses in New Zealand are low, but occasional exceptions occur and are associated with the onset of aspergillosis in otherwise healthy birds. The predominant Aspergillus species present in the leaf litter was A. fumigatus, but other species were also present. Further research is needed to confirm the optimal management of leaf litter to minimize Aspergillus spore counts. However, in the interim, our recommendations are that leaf litter should be freshly collected from areas of undisturbed forest areas and spread immediately after collection, without interim storage
Exchange Splitting and Charge Carrier Spin Polarization in EuO
High quality thin films of the ferromagnetic semiconductor EuO have been
prepared and were studied using a new form of spin-resolved spectroscopy. We
observed large changes in the electronic structure across the Curie and
metal-insulator transition temperature. We found that these are caused by the
exchange splitting of the conduction band in the ferromagnetic state, which is
as large as 0.6 eV. We also present strong evidence that the bottom of the
conduction band consists mainly of majority spins. This implies that doped
charge carriers in EuO are practically fully spin polarized.Comment: 4 pages, 5 figure
Heights of one- and two-sided congruence lattices of semigroups
The height of a poset is the supremum of the cardinalities of chains in
. The exact formula for the height of the subgroup lattice of the symmetric
group is known, as is an accurate asymptotic formula for the
height of the subsemigroup lattice of the full transformation monoid
. Motivated by the related question of determining the heights
of the lattices of left- and right congruences of , we develop a
general method for computing the heights of lattices of both one- and two-sided
congruences for semigroups. We apply this theory to obtain exact height
formulae for several monoids of transformations, matrices and partitions,
including: the full transformation monoid , the partial
transformation monoid , the symmetric inverse monoid
, the monoid of order-preserving transformations
, the full matrix monoid , the partition
monoid , the Brauer monoid and the
Temperley-Lieb monoid
Completeness for a First-order Abstract Separation Logic
Existing work on theorem proving for the assertion language of separation
logic (SL) either focuses on abstract semantics which are not readily available
in most applications of program verification, or on concrete models for which
completeness is not possible. An important element in concrete SL is the
points-to predicate which denotes a singleton heap. SL with the points-to
predicate has been shown to be non-recursively enumerable. In this paper, we
develop a first-order SL, called FOASL, with an abstracted version of the
points-to predicate. We prove that FOASL is sound and complete with respect to
an abstract semantics, of which the standard SL semantics is an instance. We
also show that some reasoning principles involving the points-to predicate can
be approximated as FOASL theories, thus allowing our logic to be used for
reasoning about concrete program verification problems. We give some example
theories that are sound with respect to different variants of separation logics
from the literature, including those that are incompatible with Reynolds's
semantics. In the experiment we demonstrate our FOASL based theorem prover
which is able to handle a large fragment of separation logic with heap
semantics as well as non-standard semantics.Comment: This is an extended version of the APLAS 2016 paper with the same
titl
Exchange bias in GeMn nanocolumns: the role of surface oxidation
We report on the exchange biasing of self-assembled ferromagnetic GeMn
nanocolumns by GeMn-oxide caps. The x-ray absorption spectroscopy analysis of
this surface oxide shows a multiplet fine structure that is typical of the Mn2+
valence state in MnO. A magnetization hysteresis shift |HE|~100 Oe and a
coercivity enhancement of about 70 Oe have been obtained upon cooling (300-5 K)
in a magnetic field as low as 0.25 T. This exchange bias is attributed to the
interface coupling between the ferromagnetic nanocolumns and the
antiferromagnetic MnO-like caps. The effect enhancement is achieved by
depositing a MnO layer on the GeMn nanocolumns.Comment: 7 pages, 5 figure
Spitzer Observations of Centaurus A: Infrared Synchrotron Emission from the Northern Lobe
We present measurements obtained with the Spitzer Space Telescope in five
bands from 3.6-24 microns of the northern inner radio lobe of Centaurus A, the
nearest powerful radio galaxy. We show that this emission is synchrotron in
origin. Comparison with ultraviolet observations from GALEX shows that diffuse
ultraviolet emission exists in a smaller region than the infrared but also
coincides with the radio jet. We discuss the possibility, that synchrotron
emission is responsible for the ultraviolet emission and conclude that further
data are required to confirm this.Comment: 4 pages, accepted by ApJ
Using conceptual metaphor and functional grammar to explore how language used in physics affects student learning
This paper introduces a theory about the role of language in learning
physics. The theory is developed in the context of physics students' and
physicists' talking and writing about the subject of quantum mechanics. We
found that physicists' language encodes different varieties of analogical
models through the use of grammar and conceptual metaphor. We hypothesize that
students categorize concepts into ontological categories based on the
grammatical structure of physicists' language. We also hypothesize that
students over-extend and misapply conceptual metaphors in physicists' speech
and writing. Using our theory, we will show how, in some cases, we can explain
student difficulties in quantum mechanics as difficulties with language.Comment: Accepted for publication in Phys. Rev. ST:PE
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