Influence of Phases Content on Pt/TiO 2

Different Pt/TiO2 and Pd/TiO2 catalysts were prepared by sol-gel method. The influence of different amounts of noble metals (1–5 mol-%) present on the microstructure as well as the photocatalytic property under 4-chlorophenol degradation was evaluated. The anatase phase was favored at low Pt content; however, the apparition of new phases after 3 mol-% (PtO) suggests a saturation lattice considering our solubility limit at 1 mol-%. Similar trend was observed when Pd was added to the TiO2 lattice. The as-prepared catalysts were deeply characterized by X-ray diffraction (XRD) with the Rietveld Method, Raman spectroscopy, high resolution scanning electron microscopy (HRSEM), scanning transmission electron microscopy (STEM), Brunauer-Emmett-Teller (BET) adsorption analysis, and X-Ray photoelectron spectroscopy (XPS). Unit-cell parameter of TiO2 phases varied from 30 to 93 vol-% depending on the amount of Pt or Pd added to the composite. HRTEM and HRSEM identified the phases in the catalysts and confirmed the nanometric size and morphology of the catalysts. An improvement in removal efficiency of 4-chlorophenol was obtained in all the specimens compared with the commercial Degussa P25, which can be explained in terms of phase composition and modification of the band gap

Estimating Contact Process Saturation in Sylvatic Transmission of Trypanosoma cruzi in the United States

Although it has been known for nearly a century that strains of Trypanosoma cruzi, the etiological agent for Chagas' disease, are enzootic in the southern U.S., much remains unknown about the dynamics of its transmission in the sylvatic cycles that maintain it, including the relative importance of different transmission routes. Mathematical models can fill in gaps where field and lab data are difficult to collect, but they need as inputs the values of certain key demographic and epidemiological quantities which parametrize the models. In particular, they determine whether saturation occurs in the contact processes that communicate the infection between the two populations. Concentrating on raccoons, opossums, and woodrats as hosts in Texas and the southeastern U.S., and the vectors Triatoma sanguisuga and Triatoma gerstaeckeri, we use an exhaustive literature review to derive estimates for fundamental parameters, and use simple mathematical models to illustrate a method for estimating infection rates indirectly based on prevalence data. Results are used to draw conclusions about saturation and which population density drives each of the two contact-based infection processes (stercorarian/bloodborne and oral). Analysis suggests that the vector feeding process associated with stercorarian transmission to hosts and bloodborne transmission to vectors is limited by the population density of vectors when dealing with woodrats, but by that of hosts when dealing with raccoons and opossums, while the predation of hosts on vectors which drives oral transmission to hosts is limited by the population density of hosts. Confidence in these conclusions is limited by a severe paucity of data underlying associated parameter estimates, but the approaches developed here can also be applied to the study of other vector-borne infections

An Antibiotic Complex from \u3ci\u3eLysobacter enzymogenes\u3c/i\u3e Strain C3: Antimicrobial Activity and Role in Plant Disease Control

Lysobacter enzymogenes C3 is a bacterial biological control agent that exhibits antagonism against multiple fungal pathogens. Its antifungal activity was attributed in part to lytic enzymes. In this study, a heat-stable antifungal factor (HSAF), an antibiotic complex consisting of dihydromaltophilin and structurally related macrocyclic lactams, was found to be responsible for antagonism by C3 against fungi and oomycetes in culture. HSAF in purified form exhibited inhibitory activity against a wide range of fungal and oomycetes species in vitro, inhibiting spore germination, and disrupting hyphal polarity in sensitive fungi. When applied to tall fescue leaves as a partially-purified extract, HSAF at 25 μg/ml and higher inhibited germination of conidia of Bipolaris sorokiniana compared with the control. Although application of HSAF at 12.5 μg/ml did not reduce the incidence of conidial germination, it inhibited appressorium formation and suppressed Bipolaris leaf spot development. Two mutant strains of C3 (K19 and ΔNRPS) that were disrupted in different domains in the hybrid polyketide synthase-nonribosomal peptide synthetase gene for HSAF biosynthesis and had lost the ability to produce HSAF were compared with the wild-type strain for biological control efficacy against Bipolaris leaf spot on tall fescue and Fusarium head blight, caused by Fusarium graminearum, on wheat. Both mutant strains exhibited decreased capacity to reduce the incidence and severity of Bipolaris leaf spot compared with C3. In contrast, the mutant strains were as efficacious as the wild-type strain in reducing the severity of Fusarium head blight. Thus, HSAF appears to be a mechanism for biological control by strain C3 against some, but not all, plant pathogenic fungi

An Advanced Exergoeconomic Comparison of CO2-Based Transcritical Refrigeration Cycles

CO2-based transcritical refrigeration cycles are currently gaining significant research attention, as they offer a viable solution to the use of natural refrigerants (e.g., CO2). However, there are almost no papers that offer an exergoeconomic comparison between the different configurations of these types of systems. Accordingly, the present work deals with a comparative exergoeconomic analysis of four different CO2-based transcritical refrigeration cycles. In addition, the work is complemented by an analysis of the CO2 abatement costs. The influences of the variation of the evaporating temperature, the gas cooler outlet temperature, and the pressure ratio on the exergy efficiency, product cost rate, exergy destruction cost rate, exergoeconomic factor, and CO2 penalty cost rate are compared in detail. The results show that the transcritical cycle with the ejector has the lowest exergetic product cost and a low environmental impact