589 research outputs found
Guidance on Design and Construction of the Built Environment Against Wildland Urban Interface Fire Hazard: A Review
Wildland-Urban Interface (WUI) fires, a worldwide problem, are gaining more importance over time due to climate change and increased urbanization in WUI areas. Some jurisdictions have provided standards, codes and guidelines, which may greatly help planning, prevention and protection against wildfires. This work presents a wide systematic review of standards, codes and guidelines for the design and construction of the built environment against WUI fire hazard from North American, European, Oceanic countries, alongside with trans-national codes. The main information reviewed includes: the definition of WUI hazards, risk areas and related severity classes, the influence of land and environmental factors, the requirements for building materials, constructions, utilities, fire protection measures and road access. Some common threads among the documents reviewed have been highlighted. They include similar attempts at: (a) defining WUI risk areas and severity classes, (b) considering land factors including the defensible space (also known as ignition zones), (c) prescribing requirements for buildings and access. The main gaps highlighted in the existing standards/guidelines include lacks of detailed and widespread requirements for resources, fire protection measures, and lacks of taking into account environmental factors in detail. The main design and construction principles contained in the reviewed documents are largely based on previous research and/or good practices. Hence, the main contributions of this paper consist in: (a) systematically disseminate these guidance concepts, (b) setting a potential basis for the development of standards/guidelines in other jurisdictions lacking dedicated WUI fire design guidance, (c) highlighting gaps in existing standards/guidelines to be addressed by current and future research
Survival of an evasive prey
We study the survival of a prey that is hunted by N predators. The predators
perform independent random walks on a square lattice with V sites and start a
direct chase whenever the prey appears within their sighting range. The prey is
caught when a predator jumps to the site occupied by the prey. We analyze the
efficacy of a lazy, minimal-effort evasion strategy according to which the prey
tries to avoid encounters with the predators by making a hop only when any of
the predators appears within its sighting range; otherwise the prey stays
still. We show that if the sighting range of such a lazy prey is equal to 1
lattice spacing, at least 3 predators are needed in order to catch the prey on
a square lattice. In this situation, we establish a simple asymptotic relation
ln(Pev)(t) \sim (N/V)2ln(Pimm(t)) between the survival probabilities of an
evasive and an immobile prey. Hence, when the density of the predators is low
N/V<<1, the lazy evasion strategy leads to the spectacular increase of the
survival probability. We also argue that a short-sighting prey (its sighting
range is smaller than the sighting range of the predators) undergoes an
effective superdiffusive motion, as a result of its encounters with the
predators, whereas a far-sighting prey performs a diffusive-type motion.Comment: 6 pages, 5 figure
Morphological, physiological and pathogenic variability of small-spore Alternaria sp. causing leaf blight of Solanaceous plants in Algeria
Due to premature defoliation, early blight epidemics can cause major yield losses. Large-spore Alternaria species such as A. solani and A. tomatophila have long been recognized as important pathogens responsible for such blight disease in the family Solanaceae and thus represent a serious risk for crop production. Small-spore Alternaria species have also been frequently isolated from plant samples with typical blight symptoms but their incidence as primary pathogens is often controversial. In order to study the diversity of small-spore Alternaria species, 32 isolates were selected from a larger collection of 130 isolates from infected leaves, fruits and stems of tomato from various growing regions of North-West Algeria. Morphological characterization under standard conditions and polymerase chain reaction (PCR) analyses using specific primers to amplify a part of the ITS regions and the 5.8S gene were conducted to confirm their identification as members of the alternata section. They were then examined according to morphological characteristics of conidia and sporulation patterns on potato carrot agar (PCA) and were segregated into three morphological species: A. alternata, A. tenuissima and A. arborescens. Colony type, substrate colour, margin, zonation, pigmentation, colony diameter and conidia production were studied on potato sucrose agar (PSA). Physiological parameters and nutritional requirements of the isolates were also assessed and a data matrix based on cluster analysis and Euclidean distance was constructed. Results of pathogenicity test on tomato showed obvious diversity among the isolates and they could be separated into two groups based on their virulence. The dendrogram based on the influence of cultural, nutritional and physiological characters suggests moderate heterogeneity within the populations of A. alternata and A. tenuissima. The small-spore species formed five clusters that fundamentally paralleled the morphological groupings. However, the results provided no evidence for geographical and pathogenicity clustering of isolates
How do paediatricians use and monitor antithyroid drugs in the UK? A clinician survey
Objective
We aimed to document current practice in the medical management of paediatric hyperthyroidism in the UK and compare to international recommendations.
Design
A 27âquestion online survey distributed via an electronic newsletter in August 2018.
Participants
Responses from 48 members (11%) of the British Society for Paediatric Endocrinology and Diabetes.
Measurements
Information about antithyroid drug (ATD) preference, treatment duration, monitoring of full blood count (FBC), management of neutropaenia, agranulocytosis screening and patient education.
Results
Carbimazole is favoured by 98% of respondents and a âdose titrationâ regimen preferred over âblock and replaceâ (65% vs 29%). TRAbs (thyroidâstimulating hormone receptor antibodies) are used for diagnostic purposes by 85% and by 33% to look for evidence of disease remission. The majority (81%) treat for a minimum of 2 years before considering a trial off ATD. All respondents reported that they âalways/usuallyâ warn their patients about the risk of agranulocytosis before starting ATD, but written information is ârarely/neverâ provided by 63%. Sore throat (98%) and fever (92%) are the most commonly cited symptoms used to alert a patient to possible agranulocytosis. FBC is measured prior to treatment by 65% and measured periodically during treatment by 70%.
Conclusions
The management of paediatric hyperthyroidism with ATDs in the UK is not consistent with all international recommendations because a block and replace ATD regimen remains widely used. TRAbs are utilized at presentation, but underused for detecting disease remission. National consensus guidelines and written patient information may refine the management of paediatric patients on ATDs
Alternaria dauci, agent causal des brûlures foliaires est pathogÚne sur différentes espÚces végétales
Conformal Current Algebra in Two Dimensions
We construct a non-chiral current algebra in two dimensions consistent with
conformal invariance. We show that the conformal current algebra is realized in
non-linear sigma-models on supergroup manifolds with vanishing dual Coxeter
number, with or without a Wess-Zumino term. The current algebra is computed
using two distinct methods. First we exploit special algebraic properties of
supergroups to compute the exact two- and three-point functions of the currents
and from them we infer the current algebra. The algebra is also calculated by
using conformal perturbation theory about the Wess-Zumino-Witten point and
resumming the perturbation series. We also prove that these models realize a
non-chiral Kac-Moody algebra and construct an infinite set of commuting
operators that is closed under the action of the Kac-Moody generators. The
supergroup models that we consider include models with applications to
statistical mechanics, condensed matter and string theory. In particular, our
results may help to systematically solve and clarify the quantum integrability
of PSU(n|n) models and their cosets, which appear prominently in string
worldsheet models on anti-deSitter spaces.Comment: 33 pages, minor correction
Evaluating aggressiveness and host range of Alternaria dauci in a controlled environment
The aggressiveness of Alternaria dauci isolates was investigated in greenhouse conditions. Twenty-seven isolates were pre-selected from a large collection to represent high diversity according to geographic or host origins and intergenic spacer (IGS) polymorphism. IGS sequence analysis revealed that isolates were grouped within three different clusters. Eleven isolates were selected and inoculated on a susceptible carrot cultivar. Three criteria (mean lesion number, mean necrotic leaf area and mean disease index) were used to assess the aggressiveness of isolates. Continuous variation in aggressiveness was shown and no clear division into isolate classes was evident. For the host range study, two isolates were inoculated under greenhouse conditions onto nine cultivated Apiaceae species, two wild Daucus species and six cultivated non-Apiaceae species representing six botanical families. Lesions varying in severity were observed on all dicot species (Apiaceae and non-Apiaceae), but no symptoms developed on the two monocots studied (leek and sweetcorn). Plant species were also differentiated on the basis of expanding lesions (cultivated and wild carrot, dill and fennel) or non-expanding lesions (other dicot species). Typical A. dauci conidia were observed after in vitro incubation of leaves with symptoms. Fungal structures were isolated from lesions and A. dauci was confirmed on the basis of conidial morphology and specific conventional PCR results. Genotyping of individual isolates performed with microsatellite markers confirmed the presence of the inoculated isolate. The results clearly showed that, in controlled conditions, the host range of A. dauci is not restricted to carrot
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