Large-scale Spread Research Articles

A priori prediction of disease invasion dynamics in a novel environment.

Directly transmitted infectious diseases spread through wildlife populations as travelling waves away from the sites of original introduction. These waves often become distorted through their interaction with environmental and population heterogeneities and by long-distance translocation of infected individuals. Accurate a priori predictions of travelling waves of infection depend upon understanding and quantifying these distorting factors. We assess the effects of anisotropies arising from the orientation of rivers in relation to the direction of disease-front propagation and the damming effect of mountains on disease movement in natural populations. The model successfully predicts the local and large-scale prevaccination spread of raccoon rabies through New York State, based on a previous spatially heterogeneous model of raccoon-rabies invasion across the state of Connecticut. Use of this model provides a rare example of a priori prediction of an epidemic invasion over a naturally heterogeneous landscape. Model predictions matched to data can also be used to evaluate the most likely points of disease introduction. These results have general implications for predicting future pathogen invasions and evaluating potential containment strategies.

Survey of cattle in northeast Colorado for evidence of chronic wasting disease: geographical and high-risk targeted sample.

A geographically targeted survey of potentially high-risk, adult cattle in chronic wasting disease (CWD)-endemic areas in Colorado was initiated to assess the possibility of the spread of CWD from deer to cattle under natural conditions. Surveyed cattle were sympatric with free-roaming deer in geographically defined areas where CWD occurs and where CWD prevalence has been estimated. To qualify for inclusion in the survey, cattle had to be at least 4 years old and had to have spent a minimum of 4 years in surveyed areas. Brains from culled cattle were examined microscopically and immunohistochemically for tissue alterations indicative of a transmissible spongiform encephalopathy (TSE). Two hundred sixty-two brains were suitable for evaluation and were found to lack changes indicative of a TSE infection. Prion deposition was not demonstrable using a method involving formic acid and proteinase-K treatment before application of monoclonal antibody to bovine prion protein (F99/97.6.1). Some incidental neuropathologic changes unrelated to those of TSEs were detected. Findings from this study suggest that large-scale spread of CWD from deer to cattle under natural range conditions in CWD-endemic areas of northeast Colorado is unlikely.

Invasion dynamics of the European shore crab, Carcinus maenas, in Australia

In Australia and most other invaded locations, rates of range expansion by the European shore crab, Carcinus maenas, are typically only a few kilometres per year, despite a planktonic duration upwards of 50 days and off-shore larval development. This relatively static distribution is punctuated by rare episodes of long-distance and large-scale spread, some of which appear to be related to unusual oceanographic conditions and some of which are likely to be human assisted. These observations suggest, first, that long planktonic duration and off-shore development in a marine invertebrate does not preclude very localised recruitment, and, second, that this recruitment norm may be punctuated by brief episodes of wide scale mixing of propagules. Punctuated dispersal has previously been suggested to account for large-scale biogeographic patterns of distribution and speciation, but may also have implications for the processes that stabilise structured spatial metapopulations.

A model of transmission of a viral epidemic among schools within a shoal of pilchards

Populations of animals are not uniformly distributed in space, but exhibit a variety of levels of organisation. The structure of this organisation has major implications for the interactions of animals, including the transmission of diseases. For example, clupeoid fishes form large shoals that subdivide into schools. Pilchards are forage fish that dominate the link in the food chain between plankton (both zoo- and phyto-) and larger fish, birds and mammals. In 1995, and again in 1998/1999, epidemics of a herpesvirus reduced stocks of Australian pilchards along 5000 km of coastline by up to 70%. As a part of a suite of studies into these phenomena, we have developed a model of the effect of the subdivision of shoals of the pilchard into schools on the transmission of this disease. Subdividing the population into schools can reduce the rate of transmission of infection. It may also make transmission rate independent of the shoal's population. However, viral transmission at the shoal level is shown to be only weakly sensitive to the details of local mixing processes between schools at realistic mixing rates. Schools do not serve as refuges to avoid the epidemic nor do they disrupt its large (hundreds to thousands of kilometres) scale spread. We can incorporate schooling into epidemic models simply by reducing the transmission rate by the number of schools in the shoal. Since we estimate infection transmission rate from the rate of spread of disease at large scale, we are implicitly already doing this in models without a schooling structure.

Spatiotemporal patterns of large-scale defoliation caused by the spruce budworm in Ontario since 1941

Survey records of spruce budworm (Choristneura fumiferana Clem.) defoliation in Ontario, taken annually since 1941, were analysed using geographic information systems (GIS), spatial statistics, and time-series methods. Cumulative frequency maps indicated that the 41 × 106 ha of Ontario that had been defoliated in at least one year since 1941 could be split into three zones of frequent defoliation separated by two approximately 100 km wide, longitudinally oriented corridors of lower frequency. Analysis of annual records of the total area defoliated showed that the fluctuations in this time series are the result of a basic oscillation of approximately 36 years, which is modified by secondary fluctuations and occasionally by sharp drops. The secondary fluctuations are at least partially due to asynchrony in otherwise remarkably similar long-wave oscillations in the eastern (25.5 × 106 ha) and western (9.6 × 106 ha) zones of frequent defoliation. Analysis of this asynchrony showed that outbreaks in the eastern zone occurred 5 or 6 years before outbreaks in the central (6.6 × 106 ha) and western zones, which were synchronous. These observations contradict previous reports of the large-scale spread of outbreaks from west to east.

Spatial Scale and the Spread of a Fungal Pathogen of Gypsy Moth

cies forms a wavefront that moves across the landscape at For reasons of logistics, most ecological studies focus on a constant speed (fig. 1), and for an interspecific interacsmall spatial scales, in study plots that typically range in tion the speed of the wavefront depends on the densities size from 0.1 m to 1 ha (Kareiva and Andersen 1990), of both interacting species. This means that small inyet many interesting ecological phenomena occur at creases in the density of the host or the pathogen can scales that range from square kilometers to the size of the lead to large increases in the speed of the wavefront of globe (Mooney and Drake 1986; Vitousek 1994). If disease, and the long-term rate of spread of the disease small-scale studies are to have relevance for large-scale will be higher than the initial rate of spread. We therephenomena, the ability to extrapolate between scales is fore use the model to ask whether the higher rate of critical. One way of extrapolating between spatial scales is spread of the disease at the larger scale may have been through the use of mathematical models that incorporate due to a combination of higher densities of both host explicit spatial structure. In this note, we use data from a and pathogen at the larger scale. The density of the host field experiment on the spatial spread of an insect pathoin the region in which large-scale spread occurred was gen (Hajek et al. 1996) to try to understand the spread of higher than it was where the pathogen was experimenthe pathogen over a large area of central New York and tally introduced, and pathogen densities were higher in Pennsylvania (Elkinton et al. 1991). the region of large-scale spread because the disease had The disease in our study is the fungal pathogen Entobuilt up to high levels in the previous season’s epidemic. mophaga maimaiga that infects larvae of the gypsy moth Our question is then, What fraction of the higher rate at Lymantria dispar. This pathogen was first introduced into the regional scale can be explained by the wavefront of North America between 1910 and 1911 as a biological disease reaching its long-term spread rate in a higher control agent to be used against gypsy moth (Hajek et al. density population? In other words, to what extent is the 1995). For unknown reasons, it then apparently disaphigher rate at the larger scale due simply to density efpeared until it caused a massive epidemic among northfects, rather than to a different mechanism of spread at eastern gypsy moth populations in 1989 (Hajek et al. the larger scale? 1990a). The large-scale data that we use track the spread

A two-dimensional model for large-scale bushfire spread

AbstractA model for bushfire spread is proposed, in which radiative heat transfer, species consumption and flammable gas production are taken into account. It is shown that fire propagation in this model does not occur as a one-dimensional travelling wave, except for smouldering combustion of wet bushland. Numerical solutions for the evolution of a line fire are obtained using a diagonally implicit finite difference scheme, and the effects of firebreaks and uncleared combustible debris are studied. An energy theorem is presented for the case of a spreading two-dimensional fire, and numerical results are illustrated.

Heroin Epidemics Revisited

This paper reviewed heroin use data from the US government's epidemiologic monitoring system for substance abuse. The monitoring system has multiple components, i.e., the Drug Abuse Warning Network of reporting emergency rooms (9), annual surveys of high school and post-high school youth (3, 4), annual National Household Surveys of Substance Abuse (7, 8, 50), Drug Use Forecasting (51), the Community Epidemiology Work Group (52), and law enforcement systems not reviewed here. These monitoring systems should identify any major increase in heroin incidence in this country relatively early. This is important, because the early stages of heroin epidemics are often hidden from society, and the epidemics are already full-blown by the time health and other agencies become aware of the size of the affected population and are required to respond. The hidden or underground nature of heroin epidemics is caused by 1) the need of each user to hide an illegal activity and 2) the delay between the time when heroin is first used and the onset of physical dependence and other adverse consequences, which bring new heroin addicts to the attention of treatment and enforcement systems. Despite an epidemiologic surveillance system which should rapidly identify large-scale heroin spread in this country, our treatment and law enforcement systems are not organized to respond rapidly to contain an epidemic. Substance abuse treatment services are not structured for rapid expansion and contraction based on fluctuating need. Apart from HIV prevention programs, we do not have outreach teams attached to treatment programs that could quickly identify local outbreaks and involve new heroin abusers in treatment (10).(ABSTRACT TRUNCATED AT 250 WORDS)

Flame spread over horizontal surfaces of polymethylmethacrylate

The U.S. Bureau of Mines conducted a large-scale study to determine the horizontal flame spread rates over the top surface of polymethylmethacrylate (PMMA) sheets. This study is part of the Bureau's program to gain a better understanding of the fire propagation of combustible materials in ventilated mine entries. The experiments were performed in a fire gallery at airflows of 0.80, 1.4, and 3.8 m s −1 with samples 9.75 m long by 1.07 m wide by 6.35 mm thick. The PMMA sheets were placed on top of 12.5-mm-thick calcium silicate boards and the upstream edge ignited with a 1 liter heptane tray fire. Pyrolysis front spread rates were calculated from temperature measurements obtained from thermocouples mounted with their beads about 1 mm above the PMMA surface and spaced along the centerline. Gas temperatures and average downstream concentrations of CO, CO 2 , and O 2 were also measured and peak heat release rates estimated. The experimentally measured pyrolysis front rates of 6±2 cm s −1 were essentially independent of airflow, and are an order of magnitude higher than those of large-scale experiments reported by other investigators whose sample lengths were too limited. These largescale spread rates are also about three orders of magnitude greater than those measured in small-scale studies where laminar flow and diffusion control the pyrolysis front rate. The rapid pyrolysis front rates reported here give good agreement with theoretical predictions based on a radiation dominated heat transfer mechanism from an optically thick flame plume, a realistic ignition temperature and physical properties for the PMMA solid.

The Politics of The Grain Trade in Iraq c. 1840-1917

Anyone who watched the televison coverage of, or read about the African famine some years ago could not help but be appalled by the many obstacles erected to impede the progress of getting food to the starving millions in Ethiopia, Somalia and the Sudan. While it is true that the difficult terrain, an inhospitable climate and the lack of rain were partly responsible for the large-scale spread of famine and dearth in the African sub-continent, it is also true that local governments were responsible for creating impediments to the alleviation of mass hunger and starvation. Governments waging war against secessionist regimes and rebel armies used political means—primarily blockades of grain and other foodstuffs—to starve the enemy forces, creating misery among the military as well as civilian populations in the rebel areas.

Response to Sean Wilentz,“Against Exceptionalism: Class Consciousness and the American Labor Movement, 1790–1920”

As a European labor historian interested in American labor history, I find Sean Wilentz's essay both informative and stimulating. Wilentz focuses on the issue of class consciousness and looks at the language of protest in Europe and America. He maintains that American labor historians have exaggerated the class conscious ness of European workers while underestimating that of American workers. On this point, I find his arguments plausible and compelling. I am more skeptical about his conclusion that the failure of a socialist party to develop in the United States is not an interesting historical question. Wilentz's description of American radicalism in the period between the Amer ican Revolution and the Civil War suggests a parallel with developments in Western Europe between the French Revolution and the Revolutions of 1848. In the first half of the nineteenth century, in both Europe and and the United States, far-reaching criticisms of large-scale industrial capitalism spread widely among small shopkeep ers, artisans, and industrial workers. This period witnessed a florescence of socialist, trade unionist, feminist, and radical republican ideas among large strata of the population. In Britain Chartism found a wider constituency for radical ideas than did any other mass working-class movement for a century.1 It is possible, as some historians have suggested, that France never again came so near to a revolutionary socialist transformation as it did during the Second Republic between 1848 and 1851.2 The rediscovery of early nineteenth-century popular militancy has led to a reexamination of the ideals that inspired these movements. It is now widely accepted that the harsh working conditions of the industrial revolution and the spread of factory labor cannot alone explain the spread of class consciousness. Work expe rience may well produce frustration and a sense of injustice but the manner of expression of such feelings, whether they are turned internally against other workers or channeled in some political direction, is a consequence of the variety of political alternatives available to workers. In nineteenth-century America the republican tradition, as transformed by its artisans, was one readily available political tradi tion.3 Wilentz's paper is most interesting and intriguing in dealing with the trans

Scale of dispersal in varying environments and its implications for life histories of marine invertebrates.

We present several models concerning the short term consequences of spreading offspring in varying environments. Our goal is to determine what patterns of spatial and temporal variation yield an advantage to increasing scale of dispersal. Of necessity, the models are somewhat artificial but we feel they are a reasonable approximation of and hence generalizable to natural systems. With these models we examine consequences of dispersal arising from environmental variation: increased environmental variance, different degrees of spatial and temporal correlation, some arbitrary spatial patterns of favorability and finally some patterns derived from long-term, large-scale weather data collected along a contiguous stretch of coastline from southern Oregon to northern Washington (USA). We examine the costs and benefits of increasing sclae of dispersal in both density dependent and density independent models.Several conclusions may be drawn from the results of these models. In the absence of any spatial or temporal order to favorability (where favorability is directly proportional to either fitness or carrying capacity) increasing scale of spread produces a higher tate of population increase. At larger scales, though, an asymptote of maximum relative advantage is approached, so each added increment of spread has a smaller contribution to fitness. This asymptote is higher and the approach to it relatively slower with increasing environmental variance. For a given environmental variance, increasing spatial correlation results in a slower approach to the same asymptote. In density independent models, increasing temporal correlation of fitness selects against increased dispersal if expected differences between sites are sufficiently great relative to variation within sites; but in this instance, density dependence yields a somewhat different result: dispersers have a refuge at sites of low carrying capacity or sites lacking non-dispersers. Finally, optimum intermediate scales of dispersal can occur where differences in expected fitness increase with increasing distance from the parental site, such as in a gradient, but where the environmental variation at a given site is fairly large relative to differences in expected fitness between adjacent sites.The foregoing results are extended for the following predictions. When greater longevity in a resistant phase of the life cycle reduces temporal variation in survival and fecundity, increased generation time should decrease the benefits of spreading offspring in an environment that would otherwise favor spread and could either increase or decrease the costs of spreading offspring in an environment selecting against spread. We speculate that if large scale patterns of varying survival and fecundity are similar to the variation in the physical environment which we examined with weather data, there should be little or no short term advantage to large scale spread of offspring (on the order of 50 kilometers or more) because expected differences increase and seldom if ever decrease with increasing distance between sites.This suggests that feeding larvae of benthic invertebrates with their concomitant long planktonic period, receive little if any advantage from increased scale of dispersal, and consequently that the advantages to planktotrophy over lecithotrophy must lie in other life history aspects, such as the ability to produce a greater number of smaller eggs.

Nonlinear equatorial spread F: Spatially large bubbles resulting from large horizontal scale initial perturbations

Motivated by the observations of large horizontal scale length equatorial spread F ‘bubbles,’ we have performed numerical simulations of the nonlinear evolution of the collisional Rayleigh‐Taylor instability in the nighttime equatorial ionosphere, using large horizontal scale length initial perturbations. The calculations were performed using a new, improved numerical code which utilizes the recently developed, fully multidimensional flux‐corrected transport (FCT) techniques. We find that large horizontal scale initial perturbations evolve nonlinearly into equally large horizontal scale spread F bubbles, on a time scale as fast as that of the corresponding small horizontal scale length perturbations previously used. Further, we find the level of plasma depletion inside the large‐scale bubbles to be appreciably higher than that of the smaller‐scale bubbles, approaching 100%, in substantial agreement with the observations. This level of depletion is due to the fact that the plasma comprising the large‐scale bubbles has its origin at much lower altitudes than that comprising the smaller scale bubbles. Analysis of the polarization electric fields produced by the vertically aligned ionospheric irregularities show this effect to be due to fringe fields similar in structure to those produced at the edge of a parallel plate capacitor.

Effect of human chorionic gonadotropin on duration of estrous cycle and fertility of normally cycling, nonlactating mares

The novel Coronavirus disease (COVID-19) in Wuhan, China, became a pandemic after its outbreak in January 2020. Countries one after the other are witnessing peak effects of the disease, and they need to learn from the experience of others already affected or peaked countries. Thus, this paper aims to analyse the effect of the COVID-19 pandemic on different countries through COVID-19 cases, resulting in deaths and recoveries.This study analyses quantitatively the lethal effects of the pandemic through the study of infections, deaths, and recoveries on the 13 most-affected COVID-19 countries as of 1 s t June. The daily change in cases, deaths, and recoveries for all the 13 countries were considered. Combined analysis for comparison and separate analysis for the detailed study were both taken for every country. All the graphs were made in RStudio using the R programming language, as it is best for statistical analysis.The casual and ignorant behaviour of people is a major reason for such a large scale spread of the coronavirus. The government of every country should be strict as well as considerate to all sections of people while making policies. There is no room for mistakes, as one wrong decision or one delayed decision can worsen the situation. However, some countries which were once the epicentre of this pandemic are now corona-free, proving that this global threat can be tackled and we should all keep our morale high.The coronavirus disease is not any ordinary viral infection; it has become a pandemic as it has an impact on health, mortality, economy and social well being of the entire world. Qualitative and Quantitative analysis of the statistics related to COVID-19 in different countries is done based on their officials' data. The primary objective of this analysis is to learn about the relationships of various countries in containing the spread of COVID-19 and the various factors such as government policies, the cooperation of people, economy, and tourism.

Wave-like structures of large-scale equatorial spread- F irregularities

By means of non-great-circle propagation on the transequatorial path Lindau-Tsumeb, the equatorial spread- F occurrence in the African area is investigated. The observations yield the spatial and temporal distribution, the mean downward velocity, and the distribution of the eastward velocity of equatorial spread- F irregularities. Irregularity patches are found to be tilted to the east. Quasi-periodical structures in west-east extension are observed and can be explained by atmospheric gravity waves.

Design and Operation of Land-Treatment Systems for Minimum Contamination of Groundwater: ABSTRACT

The increasing interest in land-treatment systems for sewage effluent and other liquid wastes, as well as some solid wastes, poses a threat to the quality of the native groundwater even though the waste water itself undergoes a marked improvement in quality as it moves through the ground and becomes water. To avoid large-scale spread of the renovated water into the groundwater basin, the renovated water should be collected again at some point by wells (deep aquifers) or drains (shallow aquifers) for reuse or release into the surface water. For the Salt River Valley, the effective transmissibility of the aquifer for recharge was evaluated from a pilot project and then used in the design of a full-scale system. This effective transmissibility was less than the a uifer transmissibility. End_of_Article - Last_Page 1592------------

Evaluation of lung burden following acute inhalation exposure to highly insoluble PuO2.

On 15 October 1965, a fire in a plutonium fabrication plant resulted in a large-scale spread of plutonium oxide. The Rocky Flats body counter was used to measure the plutonium in the lungs of all employees working in the area. Of approximately 400 employees counted, 25 were found to have enough plutonium in their lungs to deliver a dose of 15 rem/yr or greater. Data from each employee were obtained with two scintillation detectors in contact with the subject's chest. The 60-keV photon peak of 241Am was used in the measurements. The 241Am content of the plutonium released in the fire was determined and the plutonium quantity was then determined from calibrations done on a chest phantom with similar 241Am:239Pu ratios. The plutonium consisted of “high-fired” PuO2. Particle size measurements of air samples collected after the fire indicated a 0.32-μ mass median diameter (MMD) with a geometric deviation (rg) of 1.83. Lung data so far show very slow clearance. This confirms the high degree of insolubility and the small particle size. On the average, 30 per cent of material initially deposited was cleared in 2–3 months. The remaining material is clearing very slowly with little or no measurable absorption into the bloodstream.

High Accuracy Heterodyne Oscillators

The accuracy of a heterodyne oscillator after the low frequency check is made is of the same order of magnitude as that of an ordinary type of oscillator in which circuit elements of the same stability are used. It depends on the constants of the variable frequency oscillator only. This accuracy can be improved by a ratio of 10 to 1 by adding another and higher check frequency. The temperature coefficient of the circuit elements can be kept down to less than 6 parts per million. Scale errors can be reduced to a value comparable with the oscillator accuracy by spreading the scale. A precision oscillator having a frequency range up to 150 kc. and an accuracy of ±25 cycles including a scale mechanism whereby a large scale spread is obtained on a direct reading scale is described.