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In the absence of the selecting drugs, chromosomal mutations for resistance to antibiotics and other chemotheraputic agents commonly engender a cost in the fitness of microorganisms. Recent in vivo and in vitro experimental studies of the adaptation to these "costs of resistance" in Escherichia coli, HIV, and Salmonella typhimurium found that evolution in(More)
Policies aimed at alleviating the growing problem of drug-resistant pathogens by restricting antimicrobial usage implicitly assume that resistance reduces the Darwinian fitness of pathogens in the absence of drugs. While fitness costs have been demonstrated for bacteria and viruses resistant to some chemotherapeutic agents, these costs are anticipated to(More)
Mathematical models are used to ascertain the relationship between the incidence of antibiotic treatment and the frequency of resistant bacteria in the commensal flora of human hosts, as well as the rates at which these frequencies would decline following a cessation of antibiotic use. Recent studies of the population biology of plasmid-encoded and(More)
As a direct consequence of sex, organisms undergo a haploid and a diploid stage during their life cycle. Although the relative duration of haploid and diploid phases varies greatly among taxa, the diploid phase is more conspicuous in all higher organisms. Therefore it is widely believed that diploidy offers more evolutionary possibilities and is thus nearly(More)
Predictions that infectious diseases would be eliminated as a major threat to human health have been shattered by emerging and reemerging infections, among them acquired immunodeficiency syndrome (AIDS), hemorrhagic fevers, marked increases in infections caused by antimicrobial-resistant bacteria, and the resurgence of tuberculosis and malaria.(More)
We use mathematical models to investigate the within-host dynamics of mycobacterial infections. In particular, we investigate the mechanisms by which bacteria such as Mycobacterium tuberculosis and Mycobacterium leprae persist at low densities for extended periods, and attain high densities much later. We suggest that the persistence of bacteria in face of(More)
—This paper presents a new library called MHaptic for bimanual haptic interaction within generic virtual environments. It has been specifically designed to work with a Haptic Workstation TM. MHaptic provides tools for accelerated development of virtual environment applications with haptic feedback like device calibration, user comfort improvements and(More)
Eukaryotic sex leads to an alternation of haploid and diploid nuclear phases. Because all multicellular animals are diploid, diploidy is often considered a 'biological success' and many arguments have been advanced to explain the evolution of a prolonged diploid phase. Nevertheless, among eukaryotes three basic situations are encountered, where the(More)
Mercury undergoes several transformations that influence its stable isotope composition during a number of environmental and biological processes. Measurements of Hg isotopic mass-dependent (MDF) and mass-independent fractionation (MIF) in food webs may therefore help to identify major sources and processes leading to significant bioaccumulation of(More)