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The combustion products released by fires in agrochemical warehouses are reviewed and a set of elemental conversion efficiencies for production of gases such as hydrogen chlorine and sulphur dioxide is recommended for fire hazard analysis. In the absence of better data, it is recommended that the toxicity of the resulting smoke plume is calculated as the sum of dangerous dose fractions for each toxic component irrespective of its action on the body. It is argued that the hazard from combustion products released by many warehouse fires is at least as great as that from vaporized parent compounds, but that actual hazard range is a complex function of warehouse inventory, the way it is distributed throughout the warehouse, the location of the seat of the fire and the rate of spread of the fire.

Most experimental fires, by nature, are small scale ([Formula: see text]100 m), and rate of spread measurements are taken over periods of several minutes. The aim of empirical fire modellers is to ascribe a single measure of rate of forward spread over a period to a single scalar measure of wind. The actual wind affecting the fire is unmeasurable; its value must be estimated from remote anemometry. Observation and consideration of the spatial and temporal statistics of the wind has allowed confidence limits to be placed upon the accuracy with which the measured wind reflects the wind acting on the fire front. Experimental data to verify these estimates was gathered during Project Vesta, a study into high-intensity fires in dry eucalypt forests. An equation that quantifies the accuracy of the estimate of wind affecting the fire front is given. The accuracy increases with time scale, size of the fire front, and density of anemometry. When applied to a measured wind speed taken some distance from the fire, it gives a useful estimate of the likely variation of the corresponding wind at the fire front.

In the United Kingdom, the primary method of preventing ice from forming on road surfaces is to spread rock salt with purpose-built spreaders that regulate both the rate of spread and the spread pattern. British Standards Institution Standard BS3247 requires that the rock salt contain no more than 4 percent moisture by weight. Although salt is an effective deicing chemical, its extensive and intensive use on roads has been found to corrode vehicles, damage highway structures, cause detrimental effects to vegetation, and increase groundwater pollution. Prewetted salt is under trial on minor roads by local authorities in England and Scotland. The U.K. Highways Agency commissioned TRL Limited to review the use and to determine the potential benefits of prewetted salt. The use of prewetted salt has been compared with the use of dry rock salt in terms of their environmental effects as well as their cost. Factors such as salt loss due to trafficking and climatic conditions, potential hazards and damage to structures, and safety issues arising from the use of prewetted salt have been investigated. Field trials are in progress in the winter of 2000–2001 to determine the efficacy of prewetted salt as a precautionary treatment. The trials will be used to assess specifications for materials and equipment, the cost and method of retrofitting brine tanks to a spreader, the accuracy of spread width and pattern, and salt residue on the road and verge. The final results of this study will enable the Highways Agency and local authorities to determine whether to introduce prewetted salt on U.K. roads and, if so, the climatic conditions under which it should be used.

Recent studies have demonstrated that speech perception with cochlear implants can be significantly affected by electrode configuration. Contrary to expectations, broader configurations (monopolar or broad bipolar) produced equal or better speech recognition compared with narrower configurations (narrow bipolar or common ground). One hypothesis that would account for these results is that broader configurations excite larger populations of neurons providing a more robust representation of information on each channel of the prosthesis. It is known that the number of neurons excited by an electrical stimulus increases considerably as the stimulus level increases. Furthermore, many types of discrimination improve as a function of stimulus level. If the discrimination improvements seen with increasing stimulus level are due to increasing the size of the neural population carrying the signal, and if broadening the electrode configuration also increases the size of the activated neural population, then one would expect level and electrode configuration to affect discrimination in similar ways. To test this hypothesis, we studied several types of discrimination as a function of level and electrode configuration in four nonhuman primates with cochlear implants. We tested electrode configurations that produced current fields ranging from very restricted (tripolar) to broad (parallel monopolar). For each configuration, pulse-rate discrimination, amplitude-modulation-frequency discrimination, and level discrimination were tested at current levels spanning much of the psychophysical dynamic range. Results showed large effects of current level on discrimination in many cases. However, effects of electrode configuration at comparable levels within the dynamic range were smaller or absent. Furthermore, the effect of level on discrimination was independent of electrode configuration in most cases even though the rate of spread of neural activation with level is expected to depend on electrode configuration. Possible interpretations of these results are that (1) the current level adjustments necessary to achieve comparable loudness for the various configurations significantly countered any effects of electrode configuration on the size of the activated neural population, or (2) the effects of level on discrimination do not result from its effects on the spatial extent of neural activation.

A new algorithm for fire spread simulation is proposed by using a dynamic tool of the flame front change and a local spread model. The progression of fire, represented by a closed contour, is based on the determination of a parametric function. In order to compute this new parametric function, it is necessary to calculate the scalar field of the rate of spread at some points of the fire contour. A physical model has been introduced and is mainly based on the Cekirge model. This takes into account external conditions i.e. the wind, the topographic conditions and the fuel characteristics. This model provides then results with a moving boundary problem and can be used to evaluate forest fire propagation in real time. Validations are presented in order to demonstrate the soundness of this new approach.

The effect of winter temperature and forest susceptibility on the rate of gypsy moth Lymantria dispar (L.) range expansion in the lower peninsula of Michigan was analysed using historical data on moth counts in a grid of pheromone-baited traps collected from 1985 to 1994 by the Michigan Department of Agriculture. The rate of spread was measured by the distance between population boundaries in consecutive years. Boundaries were estimated for population thresholds of 1, 3, 10, 30, and 100 moths per trap using a polar coordinate system. 2 The average rate of spread estimated using all population thresholds was 15.8 km/yr. 3 The rate of spread was higher in the northern part of the lower peninsula than in the southern part, despite lower minimum January temperatures in the north. 4 The rate of spread was positively correlated with forest susceptibility, which was higher in the north than in the south.

The invasion of non-indigenous plant species poses a severe threat to native plant communities. Garlic mustard (Alliaria petiolata) is a naturalized European biennial herb that has spread rapidly through the eastern US and adjacent Canada. To determine garlic mustard rate of spread, eleven permanent plots (50×25 m) were located in seven high quality (relatively undisturbed) forests in the early stages of invasion. Garlic mustard presence was recorded within six 50×2 m permanent belt transects, and density and percent cover by age class were recorded in 36 permanent 1 m2 quadrats, between 1989 and 1992, and again in 1997. Garlic mustard spread at an average rate of 5.4 m per year between 1989 and 1992, in all plots combined. Within individual plots rate of spread varied substantially, with location of the front increasing up to 36 m and decreasing as much as 18 m between years. While the front alternately advanced and retreated, over time garlic mustard consistently advanced through all forests. Rate of spread was influenced by establishment of satellite populations, and disturbance (wind-throw and flooding). The pattern of spread within plots was one of a ragged advancing front, supplemented by establishment of satellite populations 6–40 m distant from the front, which then coalesced with the main population. Garlic mustard presence between 1989 and 1997 increased significantly within all plots, and in each age class within each plot. The greatest increases occurred in plots where this plant was initially rarest. Garlic mustard cover and density varied nonsignificantly during the same time period. These results indicate that after garlic mustard invades a forest it becomes a permanent part of the community, annually increasing in presence but fluctuating in cover and density. Garlic mustard maintains a low profile under low disturbance conditions, but increases rapidly with periodic disturbance. This study monitored garlic mustard invasion in high quality relatively undisturbed forests, and may underestimate the rate of spread in low quality highly disturbed forests.

Clinical Microbiology and Infection © 2015 The Authors. Published by El This is an open access arti Chikungunya emerged in the Pacific in 2011, and is now spreading throughout the region. In February 2011, CHIKV was detected for the first time in the Pacific in New Caledonia (33 autochthonous cases), subsequently to cases being imported from Indonesia [1]. In June 2012, a CHIKV outbreak started in Papua New Guinea; it lasted until 2013, with >1500 reported cases [1]. In 2013, an increase in the rate of spread of CHIKV was observed, with new outbreaks being reported: a second epidemic started in New Caledonia in April (30 autochthonous cases) following a new introduction from Indonesia, and another outbreak started in Yap State (Federated States of Micronesia) in August [1]. In 2014, CHIKV epidemics were reported in Tonga, American Samoa, Independent States of Samoa, and Tokelau [2]. In October 2014, a large CHIKV outbreak started in French Polynesia, with 66 000 estimated cases (~25% of the population) as of January 2015 [2,3]; this outbreak reached all of the archipelagoes of French Polynesia, and is still ongoing. Phylogenic studies demonstrated that CHIKV was probably introduced to French Polynesia from the Caribbean, and not from other Pacific countries [2]. CHIKV re-emerged in New Caledonia [2] following multiple introductions from French Polynesia; 27 imported and two autochthonous cases were reported in mid-December 2014. In January 2015, local transmission of CHIKV has been reported in the Cook Islands [3].

When attempts to eradicate an introduced pest species fail and it becomes established, barrier zones are often used to stop or to slow the spread of the population into uninfested areas. The U.S. Forest Service is currently conducting a Slow-the-Spread (STS) pilot project to evaluate the feasibility of slowing the spread of the gypsy moth (Lymantria dispar L.) in several areas along the population front. To predict the effect of barrier zones on the rate of gypsy moth spread we developed a model that assumes establishment of isolated colonies beyond the expanding population front. These colonies grow, coalesce, and thereby contribute to the movement of the population front. The model estimates the rate of spread from two functions: (1) colonization rate as a function of the distance from the population front and (2) population numbers in a colony as a function of colony age. Eradication of isolated colonies in a barrier zone was simulated by truncating the colonization rate function beyond a specific dist...

This review considers the development of some of the models and modelling approaches designed to predict the spread and spatial behaviour of wildland fire events. Such events and their accurate prediction are of great importance to those seeking to understand and manage fire-prone ecosystems. The key problem which fire modelling seeks to address is outlined. Models predicting the rate of fire spread may be classified as physical, semi-physical or empirical according to the nature of their construction. The benefits and shortcomings of each type of model are considered with reference to specific examples of each type. It is shown that there are problems with current operational models which restrict their effective use. However, the development of rigorous physical models as replacements is impeded by conceptual and practical difficulties. Accurate estimation of the rate of spread and the intensity of a fire allows prediction of the final shape and area of a fire event. The modelling techniques used to estimate the shape and area of a fire are considered including the development of sophisticated computer-based simulations of fire spread. Spatial information technologies such as remote sensing and geographic information systems (GIS) offer great potential for the effective modelling of wildland fire behaviour. While such spatial information technologies have been frequently used in the evaluation of fire danger risk, their use for the simulation of the spatiotemporal behaviour of wildland fire is not common. The way in which spatial information technologies and decision-support systems are used for fire risk evaluation and fire spread simulation is discussed. Two research areas of great importance if fire modelling techniques are to improve are a better understanding of fire-dependent phenomena and the development of a ‘new generation’ of fire spread models; current trends in these areas of research are evaluated.

A survey was conducted on Banks Peninsula, Canterbury to determine the present distribution of the subterranean pasture pest Adoryphorus couloni and to assess its potential for further spread. A. couloni has spread from previously known infestations and is now estimated to occupy 7100 ha. In particular, several sites in Gebbies Valley and near McQueens Pass have been colonized by A. couloni and invasion of the Canterbury Plains is possible. Using historical survey data and a simple reaction diffusion model of dispersal the rate of spread of A. couloni was estimated as 1.14 km/year.

A large-scale epizootic occurred in the Australasian pilchard Sardinops sagax between March and September 1995. The deaths occurred along 5000km of the Australian coastline and 500km of the New Zealand coastline. Affected fish died within a few minutes of clinical signs of respiratory distress and death was associated with hypoxaemia and hypercapnia. Significant lesions were confined to the gills and comprised acute to subacute inflammation followed by epithelial hypertrophy and hyperplasia. The lesions were initially focal but progressed to become generalized over about 4days. Only a herpesvirus was consistently present in gills of affected fish and absent from unaffected pilchards. There was no correlation with oceanographic conditions or the presence of plankton. The rate of spread of the mortality front (approximately 30km/day) in relation to the migration rate of pilchards and prevailing currents suggested that a vector might be involved. The disease may be the result of a virus introduced into Australian waters, or of a newly emerged virus.

Diseases which can pass between animals and humans (zoonoses) have been headline news several times in the last ten years. This paper looks at bovine tuberculosis (bTB) in the United Kingdom, which, although not a major health hazard for humans, has been problematic for farmers and the veterinary health institutions. At its current rate of spread, the disease will cost the authorities £1 billion in compensation to farmers for slaughtered animals and in administrative expenses over the next decade. The present Coalition government is planning to cull badgers in England because they are the principal wildlife reservoir of bTB and are said to pass infection to cattle. We argue in five stories that the heterogeneities of bTB help explain the difficulties in dealing with it. In our opinion, the present reductive set of policies would be improved by taking this ontological multiplicity into account.

In fire research and forest firefighting, there is a need of robust metrological systems able to estimate the geometrical characteristics of outdoor spreading fires. In recent years, we assist to an increased interest in wildfire research to develop non destructive techniques based on computer vision. This paper presents a new approach for the estimation of fire geometrical characteristics using near infrared stereovision. Spreading fire information like position, rate of spread, height and surface, are estimated from the computed 3D fire points. The proposed system permits to track fire spreading on a ground area of 5mx10m. Keywords: near infrared, stereovision, spreading fire, geometrical characteristics

A model previously developed for the wind-borne spread by midges of bluetongue virus in NW Europe in 2006 is here modified and applied to the spread of Schmallenberg virus in 2011. The model estimates that pregnant animals were infected 113 days before producing malformed young, the commonest symptom of reported infection, and explains the spatial and temporal pattern of infection in 70% of the 3,487 affected farms, most of which were infected by midges arriving through downwind movement (62% of explained infections), or a mixture of downwind and random movements (38% of explained infections), during the period of day (1600-2100 h, i.e. dusk) when these insects are known to be most active. The main difference with Bluetongue is the higher rate of spread of SBV, which has important implications for disease control.

Recognition of the U.S. pellagra ``epidemic'' in the early part of this century occurred in stages. The recognition process distorted impressions of magnitude, rate of spread, and virulence. Unrecognized cases: Endemic pellagra developed from dietary deficiencies after the Civil War. Initially, cases were misdiagnosed as other more traditional disorders. Tradition and authority inhibited recognition. Recognition of severe cases: Beginning in 1907, outbreaks were reported in asylums. Existing severe cases came rapidly to medical attention, inflating the apparent rate of spread. Recognized cases had a fulminant course and a high case fatality. Expanded spectrum: Milder cases were increasingly recognized, leading to an exaggerated rate of increase in number of cases and a decrease in case fatality and apparent virulence. Greater sensitivity resulted largely from a shift in diagnostic thresholds, with loss of specificity and increase in false positive diagnoses. Standardization of diagnosis: Although no suitable diagnostic marker test was developed, diagnosis was ultimately standardized by development of a workable case definition and by assessment of response to an effective therapy (nicotinic acid) applied to presumptive cases.NEUROLOGY 1996;47: 829-834

This paper includes an estimate of what we need to know for predicting the spreading rates of introduced animal and plant species. The models although catching the principal aspects of the spreading process, still prove to be too simple. Yet even in their initial state of development, they require an amount of biological and environmental information that cannot be reasonably supplied. However, as such, they can indicate the kind of information needed to make statistical prediction reliable. These models also indicate the limits of prediction beyond which extrapolations from simpler models should not be made. It thus appears that the limits of prediction are very restrictive about the fate of species accidentally or deliberately introduced into an area.

The rate of spread of Armillariaostoyae (Romagnesi) Herink was calculated from observations over 20 years on plots in two Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) plantations in the southern interior of British Columbia. Average rates of spread in active disease centers ranged from 0.7 to 1.3 m/year.

Prescribed burns are increasingly being used in ecological restoration and vegetation management. Despite the accumulation of scientific information on fire behavior and fire effects, however, in many cases fires are prescribed without consideration of such information and often simply because of evidence of past fires. Rather than basing fire management plans on ideas of the historical “natural” occurrence of fire, we present the case for fire management being based on the fire effects desired. Effective fire management and development of proper fire prescriptions require an understanding of fire processes and heat transfer that explain fire behavior characteristics, as well as an understanding of how fire behavior is coupled to specific fire effects. We provide a basic introduction to these concepts and processes, which will help in understanding the importance of having a more technical understanding of fire. The discussion includes the processes of heat transfer and the relative role of various fuel variables in these processes, as well as the concepts of fire intensity, rate of spread, fuel consumption, duff consumption, fire frequency, and the ecological effects associated with variation in these characteristics of fire behavior.

SUMMARY The decrease in the prevalence of Corynebacterium pseudotuberculosis after two generations of vaccination against the disease it causes, was used to estimate the rate of control of caseous lymphadenitis (CLA). Three groups of 150 sheep, of which 50 in each group were artificially infected with C pseudotuberculosis and 100 in each group were uninfected sheep, were run separately for 40 months and shorn 5 times to promote the spread of CLA. One lot of 50 infected sheep and 2 lots of 100 uninfected sheep were vaccinated against CLA. The rate of spread of CLA was recorded. Sheep vaccinated against CLA and naturally exposed to infection had a 74% lower infection rate than unvaccinated sheep. Sheep vaccinated against CLA and exposed to only vaccinated infected sheep had a 97% lower infection rate. Unvaccinated sheep had a 76% infection rate, with 77% of the transmission occurring at the 4th and 5th shearings, without any discharging CLA abscesses being observed. This study supports the view that in Australian wool producing flocks, CLA spreads mainly from sheep with discharging lung abscesses to sheep with shearing cuts. Vaccinated sheep infected with CLA have 96% fewer lung abscesses compared with unvaccinated infected sheep and are therefore less likely to spread this disease to other sheep.

One of the most widely cited cases of cultural transmission in animals is the opening of milk bottles by British birds. Bottle opening was first reported in Swaythling in 1921 and its spread from that date to 1947 was mapped by Fisher and Hinde (1949). Using data from Fisher and Hinde, this paper tests two quantitative models of cultural transmission: (1) the logistic model describing the cumulative number of bottle opening sites in the Belfast area and in the whole of the UK, and (2) the linear wave-of-advance model describing the progressive spread over time of bottle opening from its presumed single point of origin, Swaythling. For both the UK and Belfast, the logistic provides a poorer fit than alternative accelerating functions: the positive exponential and the reverse S-shaped hyperbolic sine respectively yield the best corrected fits to the Belfast and UK data. Neither functions have the terminal deceleration phase typical of the logistic, but both have an accelerating phase consistent with the cultural assumption of an auto-catalytic increase in the rate of spread over time. For both Belfast and the whole UK, the wave-of-advance model can clearly be rejected, even with the addition of a second source of innovation in County Durham. The results support the view that bottle opening originated from several independent sites, but spread through an accelerating process that could have included direct and/or indirect social influences.

Computational simulations of wildfires require a model for the two-dimensional expansion of a fire perimeter. Although many expressions exist for the one-dimensional rate of spread of a fire front, there are currently no agreed mathematical expressions for the two-dimensional outward speed of a fire perimeter. Multiple two-dimensional shapes such as elliptical and oval-shaped perimeters have been observed and reported in the literature, and several studies have attempted to classify these shapes using geometric approximations. Here we show that a two-dimensional outward speed based on a power series results in a perimeter that can match many of these observed shapes. The power series is based on the dot product between the vector normal to the perimeter and a fixed wind vector. The formulation allows the evolution and shape of a fire perimeter to be expressed using a small set of scalar coefficients. The formulation is implemented using the level set method, and computed perimeters are shown to provide a good match to perimeters of small-scale experimental fires. The method could provide a framework for statistical matching of wildfire shapes or be used to improve current wildfire prediction systems.

Fire managers around the world commonly use visual assessment of forest fuels to aid prediction of fire behaviour and plan for hazard reduction burning. In Australia, fuel hazard assessment guides also allow conversion of visual assessments to indicative fuel loads, which is essential for some rate of spread models and calculation of fireline intensity or emissions. The strength of correlation between fuel hazard and destructively sampled (directly measured) fuel load was tested using a comprehensive dataset of >500 points from across a range of eucalypt forests in Australia. Overall, there was poor correlation between the assigned fuel hazard rating and measured biomass for surface, near-surface and elevated fuel components, with a clear tendency for these systems to under-predict fuel load at low hazard ratings, and over-predict it at high hazard ratings. Visual assessment of surface fuels was not statistically different from a random allocation of hazard level. The considerable overlap in fuel load between hazard ratings at higher ranges suggests the need to reduce the number of hazard classes to provide clearer differentiation of fuel hazard. To accurately assess forest fuel condition, improvements in fuel hazard descriptions and calibration of visual assessment with destructively measured fuels is essential.

The behaviour and spread of a wildfire are driven by a range of processes including convection, radiation and the transport of burning material. The combination of these processes and their interactions with environmental conditions govern the evolution of a fire’s perimeter, which can include dynamic variation in the shape and the rate of spread of the fire. It is difficult to fully parametrise the complex interactions between these processes in order to predict a fire’s behaviour. We investigate whether the local curvature of a fire perimeter, defined as the interface between burnt and unburnt regions, can be used to model the dynamic evolution of a wildfire’s progression. We find that incorporation of curvature dependence in an empirical fire propagation model provides closer agreement with the observed evolution of field-based experimental fires than without curvature dependence. The local curvature parameter may represent compounded radiation and convective effects near the flame zone of a fire. Our findings provide a means to incorporate these effects in a computationally efficient way and may lead to improved prediction capability for empirical models of rate of spread and other fire behaviour characteristics.

The basic principles in the management of seed-transmitted viruses are generally more or less similar regardless of type of virus involved. There are five approaches, namely, (1) avoidance of the virus from the seeds, (2) prevention/minimising the rate of spread through vector management, (3) legislation, (4) production of healthy seeds through certification programmes and (5) modern diagnostic molecular and biochemical approaches.

Several researchers have reported that under certain conditions, forest fires with normal behavior suddenly start to propagate at unusual and very high rate of spread. Over the last decades, these accelerating forest fires were responsible for many fatalities in Europe. A thermochemical approach, based on the ignition of a volatile organic compounds (VOCs) cloud, has been proposed previously to explain this phenomenon. Indeed, some vegetal species emit volatile substances when they are heated. A typical Mediterranean plant, Rosmarinus officinalis, emits 14 components, mainly α-pinene and limonene. The acceleration of the rate of spread can be the consequence of the ignition of these emitted gases. The determination of α-pinene/air and limonene/air premixed flame speeds is essential to take into account this approach in forest fire modeling. It is the main purpose of this article. The spherical expanding flames methodology coupled with a nonlinear model was used to determine the unstretched premixed flame ...

© 2012 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting /republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works Wildfire infrared monitoring is nowadays applied to different problems related to fire prevention, fire suppression and fire behaviour analysis. In terms of research, infrared thermography offers unique capabilities although it is constantly challenging the scientific community to develop sound process imagery methodologies in order to obtain valuable and reliable information about fire phenomena. In this paper we show some infrared thermography applications that we have recently developed to provide solutions on fuel mapping, fire behaviour analysis, fire suppression and fire effects assessment. We highlight the advantages and drawbacks of all of them and present future problems that can be tackled with this type of fire monitoring techniques.

International audience; Fuel bulk density and fuel moisture content effects on fire rate of spread were assessed in shrub fuels, comparing experimental data observed in outdoor wind tunnel burns and predictions from the physically-based model FIRETEC. Statistical models for the combined effects of bulk density and fuel moisture content were fitted to both the experimental and the simulated rate of spread values using non-linear regression techniques. Results confirmed a significant decreasing effect of bulk density on rate of spread in a power law in both laboratory burns and simulations. However, experimental data showed a lesser effect than simulations, suggesting a difference in the effective drag. Fuel moisture content effect was highly consistent, showing a similar exponential relationship with rate of spread in laboratory and in simulations. FIRETEC simulations showed similar orders of magnitude with predictions of two field-based empirical models, finding a significant correlation between rate of spread values. The study confirms the efficacy of the combined approach through experimental data and simulations to study fire behaviour.

The nuclear polyhedrosis virus of Anticarsia gemmatalis (Hubner) was released into soybean fields at two sites in Louisiana. The spread of the virus outside release plots was monitored by sampling A. gemmatalis larvae, predatory arthropods and parasitoids of A. gemmatalis , and soil. According to A. gemmatalis sampling, the virus spread at a rate of 0.8 and 1.2 m/d at the Crowley and Baton Rouge sites, respectively, within ≍6 wk after it was released. The virus spread distances of up to 44 and 58 m at Crowley and Baton Rouge, respectively, during that season. The rate of spread detected in A. gemmatalis was significantly ( P > 0.01) correlated with the rate detected by sampling and bioassay of predatory arthropods and parasitoids, primarily the former. There also was circumstantial evidence implicating birds and farm machinery in viral transport; 80% ( n = 15) of bird droppings sampled at the Baton Rouge site during viral spread contained viable A. gemmatalis nuclear polyhedrosis virus. The rate of spread did not differ by direction from release plots. The prevalence of viral disease decreased at increasing distances from release plots for 3 yr after release at the Crowley site and during the 1st yr at Baton Rouge. The amount of virus in soil after the first season at the Crowley site decreased from 3,598 polyhedral inclusion bodies per gram in the release plots to 131 and

Summary Equations were fitted to the tables and graphs developed by Alan Mc Arthur (1923–1978) to predict low intensity fires suitable for control burning in mature eucalypt forest. These equations were used here to evaluate the suitability of McArthur's burning guide for predicting low-intensity fire behaviour and scorch damage in E. sieben regrowth forests of coastal New South Wales. The predicted values are compared with the observed fire behaviour data from 37 experimental fires. The burning guide predicted the moisture content of dead, fine surface fuel reasonably well within the range commonly used for prescribed burning, but over-predicted wind speed in the forest, and under-predicted rate of spread, flame height and scorch height. The guide is not recommended for use in the regrowth forest.

Many spatial models of ecological processes achieve analytical tractability by neglecting variability among individuals, in their patterns of movement, and among locations, in their favorability for colonization or persistence. We develop a series of simulations, based on standard metapopulation and partial differential equation models, that explicitly track variability among individuals or locations, and compare the results with what would be obtained by ignoring such variability. We find, first, that variability among patches can have a strong influence on the outcome of community dynamics, by promoting the coexistence of species that would otherwise exclude one or the other through competition. Second, variability among individuals in their rates of movement can markedly increase the rate of spread of a population. Construction and analysis of a modified PDE (partial differential equation) model for a population that consists of two classes of individuals, dispersed and nondispersers, confirms the seco...

There are large differences in the prevalence of HIV infection between different regions in sub-Saharan Africa, ranging from less than 10% in pregnant women in most of West Africa, to over 25% in pregnant women in large cities in Eastern and Southern Africa. These differences in HIV prevalence are in many instances due to differences in rate of spread of the virus. The multicenter study on factors determining the differential spread of HIV in four African cities tried to identify factors that could explain differences in spread of HIV between different regions in sub-Saharan Africa. The study was conducted in four cities, including two cities with a relatively low HIV prevalence (Cotonou in Bénin and Yaoundé in Cameroon) and two cities with a high HIV prevalence (Kisumu in Kenya and Ndola in Zambia). The difference in HIV prevalence between the four cities could not be explained by differences in sexual behavior. Any differences in sexual behavior were outweighed by differences in factors that influence HIV transmission, i.e. male circumcision and HSV-2 infection. These findings have important implications for the design of interventions.

The "Swine flu" pandemic of 2009 caused world-wide infections and deaths. Early efforts to understand its rate of spread were used to predict the probable future number of cases, but by the end of 2009 it was clear that these predictions had substantially overestimated the pandemic's eventual impact. In England, the Health Protection Agency made announcements of the number of cases of the disease, which turned out to be surprisingly low for an influenza pandemic. The agency also carried out a serological survey half-way through the English epidemic. In this study, we use a mathematical model to reconcile early estimates of the rate of spread of infection, weekly data on the number of cases in the 2009 epidemic in England and the serological status of the English population at the end of the first pandemic wave. Our results reveal that if there are around 19 infections (i.e., seroconverters) for every reported case then the three data-sets are entirely consistent with each other. We go on to discuss when in the epidemic such a high ratio of seroconverters to cases of disease might have been detected, either through patterns in the case reports or through even earlier serological surveys.

The increasing rate of spread of HIV, especially among the age range of 14 and 21 is becoming disturbing to the nongovernmental organizations and world governments in general. Therefore, this study was to determine the significant relationship among self esteem and religiosity, on premarital sex. Using convenience sampling, the participants were students from Olabisi Onabanjo University, Ago-Iwoye Ogun State. There were 247 participants, which were made up of 126 (51.0%) males and 121 (49.9%) females, with a mean age of 26years (SD=6.12) The participants filled out a demographic questionnaire and three surveys: the Rosenberg Self-Esteem Scale, a Religiosity Scale, and the premarital sex scale. No significant interaction was found between religiosity and self-esteem. [F (1, 243) = 2.26, P>.05] The result also revealed the significantly influence of religiosity on premarital sex. [t (245) = -3.32, P people to engage in their religious believes. The university should have a standard church and mosque on school campus.

International audience; This paper presents a new instrumentation system, based on stereovision, for the visualization and quantitative characterization of fire fronts in outdoor conditions. The system consists of a visible pre-calibrated stereo camera and a computer with dedicated software. In the proposed approach, images are captured simultaneously and processed using specialized algorithms. These algorithms permit to model three-dimensional fire fronts and extract geometric characteristics like volume, surface area, heading direction and length. Experiments were carried out in outdoor scenarios and the obtained results show the efficiency of the proposed system. This system successfully measures three-dimensional geometric parameters of fire fronts over a range of combustible and environmental conditions.

We wish to thank Mr. Gonsolin for his English reviewing; International audience; The first aim of this work is to provide an analytical expression to calculate the rate of spread of surface fires under no wind and no slope conditions. A previous simplified model was improved for this particular case of fire propagation. The test of this proposed model was performed by using two complete sets of experimental results with several fuel beds and variable parameters such as moisture content or bulk density. The second aim of this article is to highlight two conditions that allow stopping a fire: the low leaf area and the high value of the moisture content.

We correct the variance for the rate of spread of a fire through a non-homogeneous fuel as described in Catchpole et al. (1989, Ecol. Modelling, 48: 101–112). The spatial dependence of the fuel types can greatly influence this variance; a phenomenon not expressed by the analysis in Catchpole et al. The model is then expanded to include other sources of variation, such as uncertainty concering the fire spread rates in the different fuel types, which can dominate our uncertainty concerning the fire spread rate. The numerical example of fire spread in sagebrush and grass fuels from Catchpole et al. is re-examined.

It has long been common practice for firefighters to test wildfire potential by lighting single strands or leaves (sheltered from the wind) and observing the rate of spread. This paper discusses single-element fire spread and its potential as a method for determining fine- fuel moisture content and for estimating the likely rate of spread through a fuel complex. Earlier laboratory studies of spread rate along single pine needles and in beds composed of needles have been extended to the case of thin sheet fuels. These include cardboard and Eucalyptus globulus leaves. The dependence of rate of spread on moisture content, fuel orientation and fuel dimensions agrees with previous findings. In addition, the predicted variation of spread rate with moisture content has been tested using experimental data from fine fuels. From the resulting model, the value of single-element testing as a field tool can be assessed.

A new, sophisticated analysis of hundreds of genetic sequences of HIV from different time points and locations adds fascinating insights to the origin of the AIDS epidemic. The study, which appears in this issue of Science (see p. 56), confirms earlier analyses that an HIV-infected person came to what today is Kinshasa around 1920, but it then shows for the first time how the virus went from there to two cities in the southeastern portion of the country, likely aided by the extensive rail system that then existed. The researchers also note that 13 documented cases exist of different simian viruses jumping from chimpanzees, gorillas, and monkeys into humans, but only one—known has HIV-1 group M—sparked a global epidemic. They show that group M and another strain, group O, expanded at the same rate until about 1960, but then group M nearly tripled its rate of spread. Possible reasons include public health campaigns that had contaminated needles and an increase in the number of clients of sex workers.

International audience; This paper presents a three dimensional vision based instrumentation system for the measurement of the rate of spread and height of complex fire fronts. The proposed 3D imaging system is simple, does not require calibration, easily deployable in indoor and outdoor environment and can handle complex fire fronts. New approaches for measuring the position, the rate of spread and the height of a fire front during its propagation are introduced. Experiments were conducted in indoor and outdoor conditions with fires of different scales. Linear and curvilinear fire front spreading were studied. The obtained results are promising and show the interesting performance of the proposed system in operational and complex fire scenarios.

International audience; This paper presents a stereovision framework developed to monitor and to measure laboratory fire spreads. New algorithms were developed for the estimation of fire characteristics like position, rate of spread, height, depth and the distance between the fire front and metrological instruments

Background We used 32,297 HIV/AIDS patients’ records obtained from different Midwest clinics (and published in our web portal http://hivdatamining.com) to study the effect of CD4 count and RNA level fluctuation on patients’ response to HIV regimens. We had two aims: 1. to investigate if controlling the range of spread of RNA level is more important than controlling the rate of spread of CD4 count. 2. To investigate if there is enough evidence that there exist RNA and CD4 correlation distribution that lead to better therapeutic responses.

Host genetic diversity is thought to reduce the likelihood that disease will spread in natural populations. In this study, I present an epidemiological model for the intrinsic rate of spread ( \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $R_{0}$ \end{document} ) for an infectious disease. The results show that the average value for \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} ...

As an introduction to this series of papers, a brief history is given of swollen-shoot disease of cacao in the Gold Coast, and the nomenclature for cacao viruses is discussed. The symptoms of four virus diseases of cacao are described in detail, together with experimental data under the headings: cross-immunity reactions, latent period, seed transmission, staining reaction, heat inactivation and rate of spread.

A virus disease of cacao, discovered in Trinidad towards the end of 1943, is apparently confined to the north-western corner of the is land and does not occur in the main cacaogrowing areas of eastern, central and southern Trinidad; nor has it been found in Venezuela, Tobago or the Windward Islands of Grenada, St Vincent, St Lucia and Dominica. The symptoms resemble those of West African swollen shoot disease, consisting of vein-clearing or mosaic of the leaves and red-mottle of the leaves and pods. No swellings are formed, but recent observations indicate that the disease may cause both dieback and reduction in yield. There are two strains closely resembling each other. The spread of the disease under field conditions has been demonstrated, and although the rate of spread has varied somewhat, a mean increase of 41 % over the original number of infected trees has been found over a 10-month period. As with swollen shoot disease, existing diseased areas have increased in size and new outbreaks at short distances have occurred. Both strains were readily transmitted by budding, the incubation period varying from 34 to 136 days, with a mean around 90 days, but no insect vectors have been found. There is at present little reason to believe that any varieties of cacao are immune to the disease or are even symptomless carriers. The question of eradicating this virus, while its distribution remains limited, should be seriously considered.

Summary The distribution and spread of hop latent viroid (HLVd) in two adjacent plantings of the hop cultivars Omega and Wye Challenger have been studied for three seasons. The planting of cv. Omega was heavily infected at the start of the survey and spread was rapid; the density of infection was lower in the planting of cv. Wye Challenger and spread was much slower. It is not known whether the difference in rate of spread was a varietal effect or because of the higher density of infection in the Omega planting. The distribution of known infections in 1991 suggests that plant-to-adjacent-plant spread, either by contact or on tools, does occur. However, the overall distribution of infection and the occurrence of new infections not adjacent to existing ones, suggests that this is not the only means of transmission; whether a vector is involved is not known.

The potential distribution of the herbaceous weed Senecio madagascariensis Poir. (fireweed) in Australia was estimated using the Bioclimate Prediction System, BIOCLIM. Climate profiles for S. madagascariensis predicted that suitable areas occurred only in the south-eastern region of Australia. Its potential to spread outside these areas was assessed by comparing the present African and South American distributions of this species with that observed in Australia. The rate of spread of S. madagascariensis in New South Wales was exponential, although in some regions, such as the Gloucester River Valley, the rates had decreased because all farms had become infested. The results indicate that S. madagascariensis may spread and increase in abundance along the far south coast of New South Wales and in south-eastern Queensland. Coastal areas in eastern Victoria and as far north in Queensland as the Tropic of Capricorn may be invaded.