Vector-borne pathogens may alter traits of their primary hosts in ways that influence the frequency and nature of interactions between hosts and vectors. Previous work has reported enhanced mosquito attraction to host organisms infected with malaria parasites but did not address the mechanisms underlying such effects. Here we document malaria-induced changes in the odor profiles of infected mice (relative to healthy individuals) over the course of infection, as well as effects on the attractiveness of infected hosts to mosquito vectors. We observed enhanced mosquito attraction to infected mice during a key period after the subsidence of acute malaria symptoms, but during which mice remained highly infectious. This attraction corresponded to an overall elevation in the volatile emissions of infected mice observed during this period. Furthermore, data analyses-using discriminant analysis of principal components and random forest approachesrevealed clear differences in the composition of the volatile blends of infected and healthy individuals. Experimental manipulation of individual compounds that exhibited altered emission levels during the period when differential vector attraction was observed also elicited enhanced mosquito attraction, indicating that compounds being influenced by malaria infection status also mediate vector host-seeking behavior. These findings provide important insights into the cues that mediate vector attraction to hosts infected with transmissible stages of malaria parasites, as well as documenting characteristic changes in the odors of infected individuals that may have potential value as diagnostic biomarkers of infection.
SignificanceMalaria elimination efforts are hindered by the prevalence of asymptomatic infections, which frequently go undetected and untreated. Consequently, there is a pressing need for improved diagnostic screening methods. Based on extensive collections of skin odors from human populations in Kenya, we report broad and consistent effects of malaria infection on human volatile emissions. Furthermore, we found that predictive models based on machine learning algorithms reliably determined infection status based on volatile biomarkers and, critically, identified asymptomatic infections with 100% sensitivity, even in the case of low-level infections not detectable by microscopy. These findings suggest that volatile biomarkers have significant potential for the development of robust, noninvasive screening methods for detecting symptomatic and asymptomatic malaria infections under field conditions.
The low vapor pressure solvent 1-chloropentane was used to directly spincast polystyrene (PS) films onto poly(methyl methacrylate) (PMMA) with smooth surfaces and sharp interfaces. Interface roughness after removal of the PS layer with cyclohexane was determined with scanning force microscopy to be <1 nm. Dynamic secondary mass spectroscopy revealed an interfacial width below the resolution limit of $10 nm. Large area bilayers with smooth surfaces could be created. In addition, direct spincasting with 1-chloropentane allows the production of thin PS films (<15 nm) and films of low molecular weight (<5 kDa) PS, all of which would be impossible to produce for this important model system by the traditional watertransfer method. 1-chloropentane was confirmed to be a sufficiently selective solvent for PS by measuring the Flory-Huggins v parameters of 1-chloropentane with PS and PMMA, respectively, with inverse gas chromatography. In the search for a suitable selective solvent, the authors have also examined the role of vapor pressure in spin casting smooth films over a wider molecular weight (4.3-190 kDa) and thickness range ($5-500 nm) than previously reported. Only solvents with low vapor pressure produced high quality PS films. Methylcyclohexene can also be used to produce excellent, directly cast PS/PMMA bilayers, but with a smaller molecular weight and thickness window compared with 1-chloropentane. Figure 7. SIMS depth profile reveals a sharp interface between the 15/85 w/w dPS-58/PS-59 and PMMA-34 layer.
Cyclohexane has been frequently used as a selective solvent to remove PS layers or domains from polystyrene:poly(methyl methacrylate) (PS:PMMA) blends and for reorganization or self-assembly of polymer brushes and block copolymers. We have found that cyclohexane is not efficient at PS removal, observing significant residual PS at PMMA surfaces. In contrast, 1-chloropentane was found to be a far greater selective solvent (i.e., residual PS was essentially nonexistent). These results were compared to PMMA surfaces after PS was allowed to adsorb to the surface from a dilute theta solution in cyclohexane. Using near-edge X-ray absorption fine structure spectroscopy and inverse gas chromatography, coupled with self-consistent mean-field theory calculations, we have demonstrated that selectively washing a polymer from a polymer blend is nearly identical to adsorption of a polymer to a "soft" surface from a dilute solution. Improved knowledge about the effects of selective solvents will improve experimental analysis of washed systems as well as manipulation of block copolymers and polymer brushes for reorganization or self-assembly.
The Dow Chemical Company has recently introduced a new family of copolymers of ethylene and styrene identified as ethylene-styrene interpolymers (ESIs). The ability of the groupcontribution lattice-fluid equation of state (GCLF EoS) to predict the volumetric properties of a series of ESIs of different compositions, the solubility parameter of a given copolymer, and the solubility of toluene was tested. The two latter experiments were conducted in the temperature range 50-150 °C. On average, the error in density was less than 1.1% in the temperature and pressure ranges of 100-250 °C and 6.9-690 bar, respectively. The solubility parameter of the polymer was measured using inverse gas chromatography. The solubility parameter was found to have a strong temperature dependency that the model could not reproduce accurately. At 25 °C, however, the model predictions were found to be in the range of the literature data. The GCLF EoS gave good predictions for the solubilities of the vapors at low styrene contents. Discrepancies at high styrene contents were attributed to a less accurate description of the sorption of solvents in pure polystyrene. The investigation shows that crystallinity has an influence on the solvent solubilities even if they are treated on a crystal-free basis.
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