Search results for "POPULATIONS"
showing 10 items of 493 documents
Modeling multiple taxis: Tumor invasion with phenotypic heterogeneity, haptotaxis, and unilateral interspecies repellence
2021
We provide a short review of existing models with multiple taxis performed by (at least) one species and consider a new mathematical model for tumor invasion featuring two mutually exclusive cell phenotypes (migrating and proliferating). The migrating cells perform nonlinear diffusion and two types of taxis in response to non-diffusing cues: away from proliferating cells and up the gradient of surrounding tissue. Transitions between the two cell subpopulations are influenced by subcellular (receptor binding) dynamics, thus conferring the setting a multiscale character. We prove global existence of weak solutions to a simplified model version and perform numerical simulations for the full se…
Exploring the application of the navigation model with people experiencing homelessness: a scoping review
2022
People experiencing homelessness are known to be at risk of disproportionately poor health outcomes and often face barriers in accessing healthcare. Patient navigation (PN) has been identified as a way to address health disparities and engage underserved populations with healthcare services . This scoping review aims to understand how PN models have been utilized with people experiencing homelessness and other comparable populations to date and more specifically identify (a) the defining features, (b) the barriers and facilitators in implementation, and (c) the outcomes associated with PN models. Database searches were conducted in Web of Science, PubMed and SCOPUS on 15th June 2021 and 21 …
Lead concentrations in feathers and blood of common blackbirds (Turdus merula) and in earthworms inhabiting unpolluted and moderately polluted urban …
2006
9 pages; International audience; Despite the dramatic decrease of atmospheric lead (Pb) concentrations in urban areas of most industrialised countries, we hypothesised that urban common blackbirds (Turdus merula) may still be contaminated by Pb concentrations of toxicological concern due to transfer from soil through the food chain. We sampled blackbirds and earthworms, one of their main preys, in Besan?, a middle-size city of Eastern France (where atmospheric Pb concentrations decreased from 0.5 microg/m(3) in 1987 to nearly 0 in 2002) and in a rural reference site. Lead concentrations were determined in the tissues of the different functional groups of earthworms (anecic, epigeous and end…
Schistosomiasis reaches Europe
2015
International audience; An outbreak of urogenital schistosomiasis has been detected in Europe, with patients affected in France,1,2 Germany,1,2 and Italy. The infection originated in Corsica, in a river north of Porto-Vecchio, a popular tourist destination (figure). The introduction of schistosomiasis is believed to be associated with infected people arriving from a region endemic for the exclusively African parasite, Schistosoma haematobium and disseminating parasite eggs through their urine into snail breeding sites along the river.
A New Approach of Sperm Motility Subpopulation Structure in Donkey and Horse
2021
This study aimed to characterize the sperm kinematic values with high frames per second, to define the subpopulation structure of a horse and a donkey and compare them. A total of 57 fresh semen ejaculates (26 Spanish and 16 Arabian horse breeds and 10 donkeys) were collected and subsequently analyzed for kinematic parameters using the Computer-aided sperm motility analysis ISAS®v1.2 system and using a Spermtrack® 10-μm depth counting chamber. Sequences were recorded at 250 frames per second, and eight kinematic parameters were automatically evaluated. All kinematic parameters showed significant differences between a donkey and a horse and between horse breeds. All ejaculates evaluated show…
A mathematical model for the therapy of the HIV infection
2005
In this paper we consider the evolution of the HIV infection under a highly effective treatment based on a combination of RTI and/or PI drugs. This is usually modelled with a set of ODEs where the drug efficacy is a constant. In this paper we consider the treatment efficacy as a dynamic variable which evolves during the treatment. To model the dynamics of the drug efficacy we use an evolutive type assumption. The resulting set of ODEs are able to reproduce the typical pattern of the illness evolution under treatment: a period of remission, which can last several years, followed by a progressive recrudescence and a viral rebound.
Cross-Diffusion Driven Instability in a Predator-Prey System with Cross-Diffusion
2013
In this work we investigate the process of pattern formation induced by nonlinear diffusion in a reaction-diffusion system with Lotka-Volterra predator-prey kinetics. We show that the cross-diffusion term is responsible of the destabilizing mechanism that leads to the emergence of spatial patterns. Near marginal stability we perform a weakly nonlinear analysis to predict the amplitude and the form of the pattern, deriving the Stuart-Landau amplitude equations. Moreover, in a large portion of the subcritical zone, numerical simulations show the emergence of oscillating patterns, which cannot be predicted by the weakly nonlinear analysis. Finally when the pattern invades the domain as a trave…
Well-posedness of a nonlinear evolution equation arising in growing cell population
2011
We prove that a nonlinear evolution equation which comes from a model of an age-structured cell population endowed with general reproduction laws is well-posed. Copyright © 2011 John Wiley & Sons, Ltd.
Genetic variation in the primary sex ratio in populations of the intertidal copepod, Tigriopus californicus, is widespread on Vancouver Island.
2011
Hypothesis: Genetic variation for the primary sex ratio is widespread in a copepodwith polygenic sex determination. Cytoplasmic sex ratio distorters (e.g. Wolbachia andmicrosporidians) influence the primary sex ratio in this copepod. Organism: The intertidal copepod, Tigriopus californicus; six populations from VancouverIsland, British Columbia. Study site: Quantitative genetics experiment in the laboratory. PCR and antibioticsexperiment to test for the presence of cytoplasmic sex ratio distorters. Results: Genetic variation for the primary sex ratio was found in five of the six populationssurveyed. The primary sex ratio was paternally transmitted. There was no evidence thatWolbachia or mic…
Sex-specific transgenerational effects of early developmental conditions in a passerine.
2007
Most studies dealing with the trade-off between offspring number and quality have overlooked the long-term consequences for the progeny. High investment in offspring number usually results in an increased competition among nest mates. The deterioration of the early developmental conditions, due to this increased competition, can impair individual quality over the long term, and subsequently affect survival and lifetime fecundity. Moreover, the consequences of the allocation rule to offspring number vs. quality can extend across generations and give raise to grandparental effects. These transgenerational trade-offs have been explored rarely. In the present study, we manipulated the breeding …