2,742 research outputs found
The occurrence of mustard oil glucosides in Lepidium hyssopifolium Desv., L. bonariense (L.) and Capsella bursa pastoris (L.) Medic
The annual crucifers, Lepidium hyssopifolium Desv. and L. bonariense (L.) (pepperwort or peppercress), and Capsella bursa pastoris (L.) ;Medic. (shepherd's purse) are common weeds of farm and pasture in south-east Queensland. These and other cruciferous weeds are frequently grazed by livestock during dry winter months and when ingested can impart objectionable flavours to the milk of dairy cattle, or to chicken and beef flesh.l.2 The incidence of "weed taints" in milk and other dairy produce can be quite severe during unfavourable seasonal conditions and is of considerable economic concern to the dairy industry in Queensland
Paired and altruistic kidney donation in the UK: algorithms and experimentation
We study the computational problem of identifying optimal
sets of kidney exchanges in the UK. We show how to expand an integer
programming-based formulation [1, 19] in order to model the criteria that
constitute the UK definition of optimality. The software arising from this
work has been used by the National Health Service Blood and Transplant
to find optimal sets of kidney exchanges for their National Living Donor
Kidney Sharing Schemes since July 2008.We report on the characteristics
of the solutions that have been obtained in matching runs of the scheme
since this time. We then present empirical results arising from the real
datasets that stem from these matching runs, with the aim of establishing
the extent to which the particular optimality criteria that are present
in the UK influence the structure of the solutions that are ultimately
computed. A key observation is that allowing 4-way exchanges would be
likely to lead to a significant number of additional transplants
The horizon and its charges in the first order gravity
In this work the algebra of charges of diffeomorphisms at the horizon of
generic black holes is analyzed within first order gravity. This algebra
reproduces the algebra of diffeomorphisms at the horizon, (Diff(S^1)), without
central extension
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A 4D feature tracking algorithm: a multidimensional view of cyclone systems
An objective 4D algorithm developed to track extratropical relative vorticity anomaly 3D structure over time
is introduced and validated. The STACKER algorithm, structured with the TRACKER single level tracking
algorithm as source of the single-level raw tracks, objectively combines tracks from various levels to
determine the 3D structure of the cyclone (or anticyclone) events throughout their life cycle. Stacker works
progressively, beginning with two initial levels and then adding additional levels to the stack in a bottom-up
and/or top-down approach. This allows an iterative stacking approach, adding one level at a time, resulting in
an optimized 4D determination of relative vorticity anomaly events.
A two-stage validation process is carried out with the ERA-Interim dataset for the 2015 austral winter. First
the overall tracking capability during an austral winter, taking into account a set of climate indicators and
their impacts on Southern Hemisphere circulation, was compared to previous climatologies, in order to
verify the density and distribution of the cyclone events detected by STACKER. Results show the cyclone
density distribution is in very good agreement with previous climatologies, after taking into account potential
differences due to climate variability and different tracking methodologies. The second stage focuses on
three different long-lived events over the Southern Hemisphere, during the winter of 2015 spanning seven
different pressure levels. Both GOES satellite imagery, infrared and water vapour channels, and ERAInterim
cloud cover products are used in order to validate the tracks obtained as well as the algorithm’s
capability and reliability. The observed 3D cyclone structures and their time evolution are consistent with
current understanding of cyclone system development. Thus, the two-stage validation confirms that the
algorithm is suitable to track multilevel events, and can follow and analyse their 3-D life cycle and develop
full 3D climatologies and climate variability studie
JAK2V617F promotes replication fork stalling with disease-restricted impairment of the intra-S checkpoint response
Cancers result from the accumulation of genetic lesions, but the cellular consequences of driver mutations remain unclear, especially during the earliest stages of malignancy. The V617F mutation in the JAK2 non-receptor tyrosine kinase (JAK2V617F) is present as an early somatic event in most patients with myeloproliferative neoplasms (MPNs), and the study of these chronic myeloid malignancies provides an experimentally tractable approach to understanding early tumorigenesis. Introduction of exogenous JAK2V617F impairs replication fork progression and is associated with activation of the intra-S checkpoint, with both effects mediated by phosphatidylinositide 3-kinase (PI3K) signaling. Analysis of clonally derived JAK2V617F-positive erythroblasts from MPN patients also demonstrated impaired replication fork progression accompanied by increased levels of replication protein A (RPA)-containing foci. However, the associated intra-S checkpoint response was impaired in erythroblasts from polycythemia vera (PV) patients, but not in those from essential thrombocythemia (ET) patients. Moreover, inhibition of p53 in PV erythroblasts resulted in more gamma-H2Ax (γ-H2Ax)–marked double-stranded breaks compared with in like-treated ET erythroblasts, suggesting the defective intra-S checkpoint function seen in PV increases DNA damage in the context of attenuated p53 signaling. These results demonstrate oncogene-induced impairment of replication fork progression in primary cells from MPN patients, reveal unexpected disease-restricted differences in activation of the intra-S checkpoint, and have potential implications for the clonal evolution of malignancies
Competitively tight graphs
The competition graph of a digraph is a (simple undirected) graph which
has the same vertex set as and has an edge between two distinct vertices
and if and only if there exists a vertex in such that
and are arcs of . For any graph , together with sufficiently
many isolated vertices is the competition graph of some acyclic digraph. The
competition number of a graph is the smallest number of such
isolated vertices. Computing the competition number of a graph is an NP-hard
problem in general and has been one of the important research problems in the
study of competition graphs. Opsut [1982] showed that the competition number of
a graph is related to the edge clique cover number of the
graph via . We first show
that for any positive integer satisfying , there
exists a graph with and characterize a graph
satisfying . We then focus on what we call
\emph{competitively tight graphs} which satisfy the lower bound, i.e.,
. We completely characterize the competitively tight
graphs having at most two triangles. In addition, we provide a new upper bound
for the competition number of a graph from which we derive a sufficient
condition and a necessary condition for a graph to be competitively tight.Comment: 10 pages, 2 figure
Kondo effect of non-magnetic impurities and the co-existing charge order in the cuprate superconductors
We present a theory of Kondo effect caused by an induced magnetic moment near
non-magnetic impurities such as Zn and Li in the cuprate superconductors. Based
on the co-existence of charge order and superconductivity, a natural
description of the induced moment and the resulting Kondo effect is obtained in
the framework of bond-operator theory of microscopic t-J-V Hamiltonian. The
local density of state near impurities is computed in a self-consistent
Bogoliubov-de Gennes theory which shows a low-energy peak in the middle of
superconducting gap. Our theory also suggests that the charge order can be
enhanced near impuries.Comment: 5 pages, 4 figure
Stoichiometry control of magnetron sputtered BiSrCaYCuO (0x0.5) thin film, composition spread libraries: Substrate bias and gas density factors
A magnetron sputtering method for the production of thin-film libraries with
a spatially varying composition, x, in Bi2Sr2Ca1-xYxCu2Oy (0<=x<=0.5) has been
developed. Two targets with a composition of Bi2Sr2YCu2O_{8.5 + \delta} and
Bi_2Sr_2CaCu_2O_{8 + \delta} are co-sputtered with appropriate masks. The
target masks produce a linear variation in opposite, but co-linear radial
direction, and the rotation speed of the substrate table is sufficient to
intimately mix the atoms. EDS/WDS composition studies of the films show a
depletion of Sr and Bi that is due to oxygen anion resputtering. The depletion
is most pronounced at the centre of the film (i.e. on-axis with the target) and
falls off symmetrically to either side of the 75 mm substrate. At either edge
of the film the stoichiometry matches the desired ratios. Using a 12 mTorr
process gas of argon and oxygen in a 2:1 ratio, the strontium depletion is
corrected. The bismuth depletion is eliminated by employing a rotating carbon
brush apparatus which supplies a -20 V DC bias to the sample substrate. The
negative substrate bias has been used successfully with an increased chamber
pressure to eliminate the resputtering effect across the film. The result is a
thin film composition spread library with the desired stoichiometry.Comment: 16 pages, 12 figures, 4 tables, submitted to Physica C -
Superconductivity (April 15, 2005), elsart.st
Scaling analysis of a divergent prefactor in the metastable lifetime of a square-lattice Ising ferromagnet at low temperatures
We examine a square-lattice nearest-neighbor Ising quantum ferromagnet
coupled to -dimensional phonon baths. Using the density-matrix equation, we
calculate the transition rates between configurations, which determines the
specific dynamic. Applying the calculated stochastic dynamic in Monte Carlo
simulations, we measure the lifetimes of the metastable state. As the magnetic
field approaches at low temperatures, the lifetime prefactor diverges
because the transition rates between certain configurations approaches zero
under these conditions. Near and zero temperature, the divergent
prefactor shows scaling behavior as a function of the field, temperature, and
the dimension of the phonon baths. With proper scaling, the simulation data at
different temperatures and for different dimensions of the baths collapse well
onto two master curves, one for and one for .Comment: published versio
Hydrogen-bonded Silica Gels Dispersed in a Smectic Liquid Crystal: A Random Field XY System
The effect on the nematic to smectic-A transition in octylcyanobiphenyl (8CB)
due to dispersions of hydrogen-bonded silica (aerosil) particles is
characterized with high-resolution x-ray scattering. The particles form weak
gels in 8CB creating a quenched disorder that replaces the transition with the
growth of short range smectic correlations. The correlations include thermal
critical fluctuations that dominate at high temperatures and a second
contribution that quantitatively matches the static fluctuations of a random
field system and becomes important at low temperatures.Comment: 10 pages, 4 postscript figures as separate file
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