1,929 research outputs found
Comparison of Various Theoretical Measures of Aromaticity Within Monosubstituted Benzene
The effects of monosubstitution on the aromaticity of benzene are assessed using a number of different quantitative schemes. The ability of the mobile π-electrons to respond to an external magnetic field is evaluated using several variants of the NICS scheme which calculate the shielding of points along the axis perpendicular to the molecule. Another class of measures is related to the drive toward the uniformity of C-C bond lengths and strengths. Several energetic quantities are devised to approximate an aromatic stabilization energy and the tendency of the molecule to maintain planarity. There is a lack of consistency in that the various measures of aromaticity lead to differing conclusions as to the effects of substituents on the aromaticity of the ring
Hadronic interactions, precocious unification, and cosmic ray showers at Auger energies
At Auger energies only model predictions enable us to extract primary cosmic
ray features. The simulation of the shower evolution depends sensitively on the
first few interactions, necessarily related to the quality of our understanding
of high energy hadronic collisions. Distortions of the standard ``soft
semi-hard'' scenario include novel large compact dimensions and a string or
quantum gravity scale not far above the electroweak scale. Na\"{\i}vely, the
additional degrees of freedom yield unification of all forces in the TeV range.
In this article we study the influence of such precocious unification during
atmospheric cascade developments by analyzing the most relevant observables in
proton induced showers.Comment: 16 pages latex. 4 eps figure
A comparison of the effect of genetic improvement, seed source and seedling seed orchard variables on progeny growth in Eucalyptus nitens in South Africa
Eucalyptus nitens is an important forestry species
grown for pulp and paper production in the temperate,
summer-rainfall regions of South Africa. A tree improvement
programme has been ongoing at the Institute for Commercial
Forestry Research for two decades, but genetic improvement
in the species has been slow due to delayed and infrequent
flowering and seed production. Three trials were established,
firstly, to quantify the gains that have been made in the first
generation of improvement in the breeding programme and,
secondly, to establish whether a number of seed source and
orchard variables influence the performance of the progeny.
These variables were the amount of flowering trees in the seed
orchard, year of seed collection, seed orchard origin and
composition of seed orchard bulks. Diameter at breast height
and tree heights were measured in the trials at between 87 and
97 months after establishment, and timber volumes and survival
were calculated. Improved seed orchard bulks performed
significantly better (p<0.01) than unimproved controls in the
field trials. Genetic gains ranging from 23.2 to 164.8 m3ha−1
were observed over the unimproved commercial seed. There
were significant differences (p<0.01) in progeny growth between
the levels of seed orchard flowering, with higher levels
of flowering (≥40 %) producing substantially greater progeny
growth than lower flowering levels (≤20 %). The seed orchard
had no effect on progeny growth in this trial series. This
suggests that seed collected from any of the four seed
orchards tested will produce trees with significant improvement
in growth.http://link.springer.com/journal/11295hj201
Genetic characterisation of a Eucalyptus nitens base breeding population in South Africa
The measurement and statistical analysis of data from eight Eucalyptus nitens trials, established in the summer
rainfall forestry region of South Africa during the 1980s and 1990s, have enabled the characterisation of the Institute
for Commercial Forestry Research’s breeding population. Provenance testing showed that the more northerly New
South Wales (Australia) Eucalyptus nitens provenances of Barren Mountain and Barrington Tops are distinctly
better suited to the summer rainfall areas of South Africa than the southern New South Wales provenances and the
Victorian provenance, Penny Saddle. Generally, the species was not badly affected by Coniothyrium canker. High
type B genetic correlations for all site pairs, except one comparison, ranged from 0.75 to 0.99 for diameter at breast
height (dbh), indicating very little or no genotype environment interaction for dbh for the genotypes tested in this
study. Narrow-sense heritability coefficients ranged from 0.01 to 0.34, indicating that the species generally exhibited
sufficient breeding opportunity for improvement of diameter growth. High genetic correlations of greater than 0.90
between diameter measurements at 52 to 62 months after establishment and diameter measurements at 94 or 113
months were found, indicating that selections can be reliably made at five or six years. Predicted genetic gains were
highest in the trials at Goedehoop and Arthur’s Seat, with increases in dbh of 3.07 cm (17.1%) and 3.17 cm (20.7%),
respectively, at full rotation.http://www.tandfonline.com/loi/tsfs20hj201
Manipulating Gibberellin Control Over Growth and Fertility as a Possible Target for Managing Wild Radish Weed Populations in Cropping Systems
Wild radish is a major weed of Australian cereal crops. A rapid establishment, fast growth, and abundant seed production are fundamental to its success as an invasive species. Wild radish has developed resistance to a number of commonly used herbicides increasing the problem. New innovative approaches are needed to control wild radish populations. Here we explore the possibility of pursuing gibberellin (GA) biosynthesis as a novel molecular target for controlling wild radish, and in doing so contribute new insights into GA biology. By characterizing ga 3-oxidase (ga3ox) mutants in Arabidopsis, a close taxonomic relative to wild radish, we showed that even mild GA deficiencies cause considerable reductions in growth and fecundity. This includes an explicit requirement for GA biosynthesis in successful female fertility. Similar defects were reproducible in wild radish via chemical inhibition of GA biosynthesis, confirming GA action as a possible new target for controlling wild radish populations. Two possible targeting approaches are considered; the first would involve developing a species-specific inhibitor that selectively inhibits GA production in wild radish over cereal crops. The second, involves making crop species insensitive to GA repression, allowing the use of existing broad spectrum GA inhibitors to control wild radish populations. Toward the first concept, we cloned and characterized two wild radish GA3OX genes, identifying protein differences that appear sufficient for selective inhibition of dicot over monocot GA3OX activity. We developed a novel yeast-based approach to assay GA3OX activity as part of the molecular characterization, which could be useful for future screening of inhibitory compounds. For the second approach, we demonstrated that a subset of GA associated sln1/Rht-1 overgrowth mutants, recently generated in cereals, are insensitive to GA reductions brought on by the general GA biosynthesis inhibitor, paclobutrazol. The location of these mutations within sln1/Rht-1, offers additional insight into the functional domains of these important GA signaling proteins. Our early assessment suggests that targeting the GA pathway could be a viable inclusion into wild radish management programs that warrants further investigation. In drawing this conclusion, we provided new insights into GA regulated reproductive development and molecular characteristics of GA metabolic and signaling proteins.The work was supported by the CRC for Australian Weed Management and the Australian Research Council Centre of Excellence for Translational Photosynthesis (CE140100015)
New alleles of the wheat domestication gene Q reveal multiple roles in growth and reproductive development
The advantages of free threshing in wheat led to the selection of the domesticated Q allele, which is now present in almost all modern wheat varieties. Q and the pre-domestication allele, q, encode an AP2 transcription factor, with the domesticated allele conferring a free-threshing character and a subcompact (i.e. partially compact) inflorescence (spike). We demonstrate that mutations in the miR172 binding site of the Q gene are sufficient to increase transcript levels via a reduction in miRNA-dependent degradation, consistent with the conclusion that a single nucleotide polymorphism in the miRNA binding site of Q relative to q was essential in defining the modern Q allele. We describe novel gain- and loss-of-function alleles of Q and use these to define new roles for this gene in spike development. Q is required for the suppression of ‘sham ramification’, and increased Q expression can lead to the formation of ectopic florets and spikelets (specialized inflorescence branches that bear florets and grains), resulting in a deviation from the canonical spike and spikelet structures of domesticated wheat.This work was supported by an Australian National University (ANU) University
Research Scholarship and a Commonwealth Scientific and Industrial Research
Organisation (CSIRO) OCE PhD Top-up Scholarshi
Managing alcohol-related attendances in emergency care: can diversion to bespoke services lessen the burden?
Acute alcohol intoxication (AAI) has a long history of burdening emergency care services. Healthcare systems around the world have explored a variety of different services that divert AAI away from EDs to better manage their condition. Little formal evaluation has been undertaken, particularly in the UK where alcohol misuse is one of the highest in the world. In this article, we outline a brief history of diversionary services, introduce the concept of Alcohol Intoxication Management Services (AIMS) and describe examples of AIMS in the UK. We then describe Evaluating the Diversion of Alcohol-Related Attendances, a natural experiment including six cities with AIMS compared with six cities without, that involves an ethnographic study, records patient experiences in both AIMS and EDs, assesses impact on key performance indicators in healthcare and evaluates the cost-effectiveness of AIMS
A novel isolator-based system promotes viability of human embryos during laboratory processing
In vitro fertilisation (IVF) and related technologies are arguably the most challenging of all cell culture applications. The starting material is a single cell from which one aims to produce an embryo capable of establishing a pregnancy eventually leading to a live birth. Laboratory processing during IVF treatment requires open manipulations of gametes and embryos, which typically involves exposure to ambient conditions. To reduce the risk of cellular stress, we have developed a totally enclosed system of interlinked isolator-based workstations designed to maintain oocytes and embryos in a physiological environment throughout the IVF process. Comparison of clinical and laboratory data before and after the introduction of the new system revealed that significantly more embryos developed to the blastocyst stage in the enclosed isolator-based system compared with conventional open-fronted laminar flow hoods. Moreover, blastocysts produced in the isolator-based system contained significantly more cells and their development was accelerated. Consistent with this, the introduction of the enclosed system was accompanied by a significant increase in the clinical pregnancy rate and in the proportion of embryos implanting following transfer to the uterus. The data indicate that protection from ambient conditions promotes improved development of human embryos. Importantly, we found that it was entirely feasible to conduct all IVF-related procedures in the isolator-based workstations
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