Heterogeneous model of schistosomiasis transmission and long-term control: the combined influence of spatial variation and age-dependent factors on optimal allocation of drug therapy

Parasitology ◽  
2004 ◽  
Vol 130 (1) ◽  
pp. 49-65 ◽  
Author(s):  
D. GURARIE ◽  
C. H. KING
Keyword(s):  
Large Scale ◽  
Optimal Allocation ◽  
Field Studies ◽  
Human Populations ◽  
Infection Prevalence ◽  
Snail Population ◽  
Extended Model ◽  
Heterogeneous Model ◽  
Age Dependent

Prior field studies and modelling analyses have individually highlighted the importance of age-specific and spatial heterogeneities on the risk for schistosomiasis in human populations. As long-term, large-scale drug treatment programs for schistosomiasis are initiated in subSaharan Africa and elsewhere, optimal strategies for timing and distribution of therapy have yet to be fully defined on the working, district-level scale, where strong heterogeneities are often observed among sublocations. Based on transmission estimates from recent field studies, we develop an extended model of heterogeneous schistosome transmission for distributed human and snail population clusters and age-dependent behaviour, based on a ‘mean worm burden+snail infection prevalence’ formulation. We analyse its equilibria and basic reproduction patterns and their dependence on the underlying transmission parameters. Our model allows the exploration of chemotherapy-based control strategies targeted at high-risk behavioural groups and localities, and the approach to an optimal design in terms of cost. Efficacy of the approach is demonstrated for a model environment having linked, but spatially-distributed, populations and transmission sites.

scholarly journals Short- and Long-Term Effects of Nonconsciously Processed Ambient Scents in a Servicescape: Findings From Two Field Experiments

2019 ◽  
Vol 22 (4) ◽  
pp. 440-455 ◽  
Author(s):  
Anna Girard ◽  
Marcel Lichters ◽  
Marko Sarstedt ◽  
Dipayan Biswas
Keyword(s):  
Large Scale ◽  
Field Experiments ◽  
Field Studies ◽  
Long Term Effects ◽  
Short Term ◽  
Railway Company ◽  
Short And Long Term ◽  
Ambient Scents ◽  
Short Term Effects

Ambient scents are being increasingly used in different service environments. While there is emerging research on the effects of scents, almost nothing is known about the long-term effects of consumers’ repeated exposure to ambient scents in a service environment as prior studies on ambient scents have been lab or field studies examining short-term effects of scent exposure only. Addressing this limitation, we examine the short- and long-term effects of ambient scents. Specifically, we present a conceptual framework for the short- and long-term effects of nonconsciously processed ambient scent in olfactory-rich servicescapes. We empirically test this framework with the help of two large-scale field experiments, conducted in collaboration with a major German railway company, in which consumers were exposed to a pleasant, nonconsciously processed scent. The first experiment demonstrates ambient scent’s positive short-term effects on consumers’ service perceptions. The second experiment—a longitudinal study conducted over a 4-month period—examines scent’s long-term effects on consumers’ reactions and demonstrates that the effects persist even when the scent has been removed from the servicescape.

On the interpretation of age—prevalence curves for schistosome infections of host snails

Parasitology ◽  
1989 ◽  
Vol 99 (1) ◽  
pp. 47-56 ◽  
Author(s):  
M. E. J. Woolhouse
Keyword(s):  
Survival Rate ◽  
Field Studies ◽  
Significant Loss ◽  
High Rate ◽  
Snail Population ◽  
Infection Rates ◽  
Force Of Infection ◽  
Age Dependent ◽  
The Relationship ◽  
Patent Infection

SUMMARYThe prevalence of schistosome infections in intermediate host snails varies with snail age. The relationship between age and prevalence, the age—prevalence curve, is complex and may vary in space and time, and among parasite—host species. Field studies show that the shape of the age—prevalence curve may be seasonally variable, and that at some times there may be a decline in prevalence among older snails. This paper attempts to explain these observations in terms of the underlying epidemiological processes. A discrete-time version of Muench's catalytic model for age-dependent infection is developed. Model simulations were carried out using life-history and epidemiological parameters derived from studies ofSchistosoma haematobium—Bulinus globususin Zimbabwe. Analysis of model behaviour identifies aspects of the schistosome— snail interaction that affect the shape of the age—prevalence curve. The following features can result in a decline in prevalence among older snails. (1) A decrease in the survival rate of patent infected snails with age. (2) A decrease in the force of infection with age. (3) A high rate of loss of infection. (4) A heterogeneity in the snail population such that the probability of infection is correlated with snail fecundity. (This would occur if there existed a spatial correlation between force of infection and fecundity, or if there were a correlation between fecundity and susceptibility.) The evidence for the occurrence of these features in the field is assessed. Survival rate is related more closely to the duration of patent infection than to ageper se. The evidence for age-dependent force of infection is equivocal. Significant loss-of-infection rates have yet to be demonstrated. Heterogeneities in force of infection and fecundity have been reported and, for the Zimbabwe data, this mechanism can explain seasonally in the age—prevalence curve as a function of known seasonal variation in the force of infection and snail fecundity.

scholarly journals Anthropogenic Biomes: 10,000 BCE to 2015 CE

Land ◽  
2020 ◽  
Vol 9 (5) ◽  
pp. 129 ◽  
Author(s):  
Erle C. Ellis ◽  
Arthur H.W. Beusen ◽  
Kees Klein Goldewijk
Keyword(s):  
Land Use ◽  
Large Scale ◽  
Substantial Reduction ◽  
Human Populations ◽  
Major Advance ◽  
Terrestrial Biosphere ◽  
Environmental Consequences ◽  
History Of ◽  
Time Periods

Human populations and their use of land have reshaped landscapes for thousands of years, creating the anthropogenic biomes (anthromes) that now cover most of the terrestrial biosphere. Here we introduce the first global reconstruction and mapping of anthromes and their changes across the 12,000-year interval from 10,000 BCE to 2015 CE; the Anthromes 12K dataset. Anthromes were mapped using gridded global estimates of human population density and land use from the History of the Global Environment database (HYDE version 3.2) by a classification procedure similar to that used for prior anthrome maps. Anthromes 12K maps generally agreed with prior anthrome maps for the same time periods, though significant differences were observed, including a substantial reduction in Rangelands anthromes in 2000 CE but with increases before that time. Differences between maps resulted largely from improvements in HYDE’s representation of land use, including pastures and rangelands, compared with the HYDE 3.1 input data used in prior anthromes maps. The larger extent of early land use in Anthromes 12K also agrees more closely with empirical assessments than prior anthrome maps; the result of an evidence-based paradigm shift in characterizing the history of Earth’s transformation through land use, from a mostly recent large-scale conversion of uninhabited wildlands, to a long-term trend of increasingly intensive transformation and use of already inhabited and used landscapes. The spatial history of anthropogenic changes depicted in Anthromes 12K remain to be validated, especially for earlier time periods. Nevertheless, Anthromes 12K is a major advance over all prior anthrome datasets and provides a new platform for assessing the long-term environmental consequences of human transformation of the terrestrial biosphere.

scholarly journals Metals Leak from Tilled Soil in a Century – A Review

2015 ◽  
Vol 7 (12) ◽  
pp. 15
Author(s):  
Gunnar Bengtsson
Keyword(s):  
Large Scale ◽  
Penetration Rate ◽  
Modern Society ◽  
Field Studies ◽  
Basic Set ◽  
Metal Contents ◽  
Significant Difference ◽  
Supplementary Material ◽  
The Mean

<p>Toxic metals are mobilized on a large scale in modern society. Many of those metals end up in sewage sludge. The objective of this review was to elucidate the threat to groundwater due to a few metals lost from tilled sludge amended soils. It is sometimes suggested that these metals are immobilized in the topsoil and do not move downward. In contrast, dozens of long term field studies around the world indicate that penetration depths for metals increase with time since deposition.</p><p>Such studies were examined in depth in the current analysis. An equation was developed for calculation of long term mean metal penetration rates into the topsoil for copper and silver. The equation is valid for about a century but not much longer. The mean depths of a basic set of 11 cases from studies over 4 years to 100 years were predicted with a standard deviation of 11%. A typical penetration rate was 3 mm per year. There was no significant difference in penetration rate between several cations. Extremely large amendments were associated with larger penetration rates.</p><p>When metals have traversed the topsoil, the groundwater will be contaminated. The European Groundwater Pollution Directive stipulates that pesticide levels should be kept below 0.1 µg/l. When sludge is applied to agricultural soil, this level may by far be exceeded for many metals, even if strict limitations are applied to the metal contents of the sludge. This calls for careful assessment of the groundwater consequences of sludge amendment.</p><p>Extensive supplementary material provides many detailed tables, texts and references.</p>

Sequestration of CO2 in Geological Media: A Case Study of the Saline Reservoir Using Parallel Computing for Multi-Well Injection

2013 ◽  
Vol 284-287 ◽  
pp. 1468-1472 ◽  
Author(s):  
Chien Hao Tseng ◽  
Chia Chen Kuo ◽  
Wei Chih Su ◽  
Chuan Lin Lai
Keyword(s):  
Carbon Dioxide ◽  
Parallel Computing ◽  
Large Scale ◽  
Scale Model ◽  
Heterogeneous Model ◽  
Injection Model ◽  
And Storage ◽  
Saline Reservoir

Carbon-Dioxide Capture and Storage (CCS) in deep saline aquifers is one of the most feasible techniques for reducing anthropogenic emission of carbon dioxide (CO2). In this paper, a high-performance parallel computing is used to simulate the large-scale and long-term CO2 geologic storage in the saline aquifer (Sleipner Vest field in the Norwegian) based on the ECO2N module of the flow/transport simulator TOUGH2-MP, which is the parallel version of TOUGH2 implemented by the MPI. We have developed a complex three-dimensional heterogeneous model to study the spatial and temporal distribution and storage of CO2 injection into the sands of the Utsira formation, at the Sleipner Vest field in the Norway. Simulation results demonstrate that the high-speed parallel computing enhanced the capability on handling the large-scale model and the long-term studies. Furthermore, in order to avoid the problems of overpressure in the saline reservoir, the case study employs multi-well (ten-well) injection model, which has been proven to be able to reduce the reservoir pressure effectively when compared to the single-well injection model.

Evolution of Large-Scale Coronal Structures

1994 ◽  
Vol 144 ◽  
pp. 29-33
Author(s):  
P. Ambrož
Keyword(s):  
Magnetic Field ◽  
Field Line ◽  
Large Scale ◽  
Coronal Magnetic Field ◽  
Source Surface ◽  
Solar Cycles ◽  
Characteristic Relationship ◽  
The Magnetic Field ◽  
Coronal Structures

AbstractThe large-scale coronal structures observed during the sporadically visible solar eclipses were compared with the numerically extrapolated field-line structures of coronal magnetic field. A characteristic relationship between the observed structures of coronal plasma and the magnetic field line configurations was determined. The long-term evolution of large scale coronal structures inferred from photospheric magnetic observations in the course of 11- and 22-year solar cycles is described.Some known parameters, such as the source surface radius, or coronal rotation rate are discussed and actually interpreted. A relation between the large-scale photospheric magnetic field evolution and the coronal structure rearrangement is demonstrated.

Computer Analyses in Preventive Health Research

1967 ◽  
Vol 06 (01) ◽  
pp. 8-14 ◽  
Author(s):  
M. F. Collen
Keyword(s):  
Medical Research ◽  
Preventive Medicine ◽  
Health Research ◽  
Large Scale ◽  
Preventive Health ◽  
New Era ◽  
Large Numbers ◽  
Normal Test ◽  
Computer Analyses

The utilization of an automated multitest laboratory as a data acquisition center and of a computer for trie data processing and analysis permits large scale preventive medical research previously not feasible. Normal test values are easily generated for the particular population studied. Long-term epidemiological research on large numbers of persons becomes practical. It is our belief that the advent of automation and computers has introduced a new era of preventive medicine.

COVID - 19 AND THE PROBLEM OF PERSONALITY

2020 ◽  
pp. 31-35
Author(s):  
Mazaeva N.A. ◽  
Golovina A.G.
Keyword(s):  
General Population ◽  
Age Groups ◽  
Personal Transformation ◽  
Personality Changes ◽  
Age Dependent

In order to determine possible trends in the dynamics and characterological structure of personality in the General population caused by the COVID-19 pandemic, which is a long-term strong stressful effect and clinically and psychopathologically comparable to chronic personality changes after experiencing a disaster, the conditions predisposing to personal transformation, including clinical and prognostic patterns, are analyzed. The age-dependent nature of these changes is shown, and a number of features identified for different age groups are discussed.

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