Chemical structures and theoretical models of lean premixed atmospheric-pressure propene/O2/N2 flames

To better understand the chemistry involved in the lean-fuel combustion, the chemical structure of lean premixed propene-oxygen-nitrogen flames stabilized on a flat-flame burner at atmospheric pressure was determined experimentally. The species mole fraction profiles were also computed by the Premix code and three detailed reaction mechanisms. A very good agreement was observed for the main properties: reactants consumption, final products (CO2, H2O) and the main intermediates: CO and H2. Only a general agreement is also observed between predicted and measured mole fraction profiles for minor intermediates. Marked differences occurred in the prediction of active intermediate species present in small concentrations. Pathways analyses were performed to identify the origins of these discrepancies. It was shown that the same reactions were involved in the three mechanisms to describe the consumption of propene, but with marked differences in their importance. C2H5, C2H4, and C3H5 are the main species formed in the first step and their consumption increases the differences between the mechanisms either by the use of different kinetics data for common reactions or by differences in the nature of the consumption reactions. KEY WORDS: Flame structure, Lean flame, Propene, Combustion mechanisms Bull. Chem. Soc. Ethiop. 2012, 26(2), 211-226.DOI: http://dx.doi.org/10.4314/bcse.v26i2.

Formation of carbonyl compounds in lean premixed atmospheric-pressure Ethylene/O2/N2 flames

Motivated by a better understanding of lean-fuel combustion, the present study has determined experimentally the chemical structure of four lean ethylene-oxygen-nitrogen flames stabilized on the flat-flame burner at atmospheric pressure (φ = 0.47, 0.508, 0.693 and 0.81). Species mole fraction profiles were also computed by the Premix code (Chemkin II version) and three detailed reaction mechanisms .A very good agreement was observed between the main flame properties: reactants consumption, final products (CO2, H2O), main intermediates, and other hydrocarbons in small concentrations, and the modeling. A special care was brought to the examination of the relative importance of carbonyl compounds formation and consumption, mainly (CH2O and CH3CHO). Pathway analyses were performed to identify the formation from the direct consumption of ethylene through the C2H3 and CH2HCO. Sensitivity analyses were also performed in order to delineate the most sensitive reaction on the formation and consumption of these two carbonyl compounds.Keywords: Flame structure, lean flames, ethylene, carbonyl compounds, combustion, mechanisms

IL-18 Does not Increase Allergic Airway Disease in Mice When Produced by BCG

Whilst BCG inhibits allergic airway responses in murine models, IL-18 has adversary effects depending on its environment. We therefore constructed a BCG strain producing murine IL-18 (BCG-IL-18) and evaluated its efficiency to prevent an asthma-like reaction in mice. BALB/cByJ mice were sensitized (day (D) 1 and D10) by intraperitoneal injection of ovalbumin (OVA)-alum and primary (D20–22) and secondary (D62, 63) challenged with OVA aerosols. BCG or BCG-IL-18 were intraperitonealy administered 1 hour before each immunization (D1 and D10). BCG-IL-18 and BCG were shown to similarly inhibit the development of AHR, mucus production, eosinophil influx, and local Th2 cytokine production in BAL, both after the primary and secondary challenge. These data show that IL-18 did not increase allergic airway responses in the context of the mycobacterial infection, and suggest that BCG-IL-18 and BCG are able to prevent the development of local Th2 responses and therefore inhibit allergen-induced airway responses even after restimulation

Supersymmetric structure of the induced W gravities

We derive the supersymmetric structure present in W-gravities which has been already observed in various contexts as Yang-Mills theory, topological field theories, bosonic string and chiral W_{3}-gravity. This derivation which is made in the geometrical framework of Zucchini, necessitates the introduction of an appropriate new basis of variables which replace the canonical fields and their derivatives. This construction is used, in the W_{2}-case, to deduce from the Chern-Simons action the Wess-Zumino-Polyakov action.Comment: 17 pages, Latex. To appear in Class. Quantum. Gravit

A Comparative Study of the Formation of Aromatics in Rich Methane Flames Doped by Unsaturated Compounds

For a better modeling of the importance of the different channels leading to the first aromatic ring, we have compared the structures of laminar rich premixed methane flames doped with several unsaturated hydrocarbons: allene and propyne, because they are precursors of propargyl radicals which are well known as having an important role in forming benzene, 1,3-butadiene to put in evidence a possible production of benzene due to reactions of C4 compounds, and, finally, cyclopentene which is a source of cyclopentadienylmethylene radicals which in turn are expected to easily isomerizes to give benzene. These flames have been stabilized on a burner at a pressure of 6.7 kPa (50 Torr) using argon as dilutant, for equivalence ratios (?) from 1.55 to 1.79. A unique mechanism, including the formation and decomposition of benzene and toluene, has been used to model the oxidation of allene, propyne, 1,3 butadiene and cyclopentene. The main reaction pathways of aromatics formation have been derived from reaction rate and sensitivity analyses and have been compared for the three types of additives. These combined analyses and comparisons can only been performed when a unique mechanism is available for all the studied additives

Sucrose and starch intake contribute to reduced alveolar bone height in a rodent model of naturally occurring periodontitis

Funding: This research project was funded in part by the Strategic Research Excellence Initiative 2020 (SREI2020), University of Sydney to JE and the University of Sydney HMR + Implementation Funding Grant to VC, DLC and SS.Peer reviewedPublisher PD

Phylogenomic exploration of the relationships between strains of Mycobacterium avium subspecies paratuberculosis.

BACKGROUND: Mycobacterium avium subspecies paratuberculosis (Map) is an infectious enteric pathogen that causes Johne's disease in livestock. Determining genetic diversity is prerequisite to understanding the epidemiology and biology of Map. We performed the first whole genome sequencing (WGS) of 141 global Map isolates that encompass the main molecular strain types currently reported. We investigated the phylogeny of the Map strains, the diversity of the genome and the limitations of commonly used genotyping methods. RESULTS: Single nucleotide polymorphism (SNP) and phylogenetic analyses confirmed two major lineages concordant with the former Type S and Type C designations. The Type I and Type III strain groups are subtypes of Type S, and Type B strains are a subtype of Type C and not restricted to Bison species. We found that the genome-wide SNPs detected provided greater resolution between isolates than currently employed genotyping methods. Furthermore, the SNP used for IS1311 typing is not informative, as it is likely to have occurred after Type S and C strains diverged and does not assign all strains to the correct lineage. Mycobacterial Interspersed Repetitive Unit-Variable Number Tandem Repeat (MIRU-VNTR) differentiates Type S from Type C but provides limited resolution between isolates within these lineages and the polymorphisms detected do not necessarily accurately reflect the phylogenetic relationships between strains. WGS of passaged strains and coalescent analysis of the collection revealed a very high level of genetic stability, with the substitution rate estimated to be less than 0.5 SNPs per genome per year. CONCLUSIONS: This study clarifies the phylogenetic relationships between the previously described Map strain groups, and highlights the limitations of current genotyping techniques. Map isolates exhibit restricted genetic diversity and a substitution rate consistent with a monomorphic pathogen. WGS provides the ultimate level of resolution for differentiation between strains. However, WGS alone will not be sufficient for tracing and tracking Map infections, yet importantly it can provide a phylogenetic context for affirming epidemiological connections

The quality of energy- and macronutrient-balanced diets regulates host susceptibility to influenza in mice

Modulation of individual macronutrients or caloric density is known to regulate host resistance to infection in mice. However, the impact of diet composition, independent of macronutrient and energy content, on infection susceptibility is unclear. We show that two laboratory rodent diets, widely used as standard animal feeds and experimental controls, display distinct abilities in supporting mice during influenza infection. Mice placed on the highly processed AIN93G showed increased mortality to infection compared with those on a grain-based chow diet, suggesting a detrimental role for highly processed food in host defense. We further demonstrate that the heightened susceptibility of AIN93G-fed mice was associated with the failure in homeostasis restoration mediated by the cytokine interferon (IFN)-γ. Our findings show that diet composition calibrates host survival threshold by regulating adaptive homeostasis and highlights a pivotal role for extrinsic signals in host phenotype and outcome of host-pathogen interaction

Restriction of essential amino acids dictates the systemic metabolic response to dietary protein dilution

Dietary protein dilution, where protein is reduced and replaced by other nutrient sources without caloric restriction, promotes metabolic health via the hepatokine Fgf21. Here, the authors show that essential amino acids threonine and tryptophan are necessary and sufficient to induce these effects

Occurrence of Mycobacterium avium subspecies paratuberculosis across host species and European countries with evidence for transmission between wildlife and domestic ruminants

<p>Abstract</p> <p>Background</p> <p><it>Mycobacterium avium </it>subspecies <it>paratuberculosis </it>(<it>Map</it>) causes an infectious chronic enteritis (paratuberculosis or Johne's disease) principally of ruminants. The epidemiology of <it>Map </it>is poorly understood, particularly with respect to the role of wildlife reservoirs and the controversial issue of zoonotic potential (Crohn's disease). Genotypic discrimination of <it>Map </it>isolates is pivotal to descriptive epidemiology and resolving these issues. This study was undertaken to determine the genetic diversity of <it>Map</it>, enhance our understanding of the host range and distribution and assess the potential for interspecies transmission.</p> <p>Results</p> <p>164 <it>Map </it>isolates from seven European countries representing 19 different host species were genotyped by standardized IS<it>900 </it>- restriction fragment length polymorphism (IS<it>900</it>-RFLP), pulsed-field gel electrophoresis (PFGE), amplified fragment length polymorphisms (AFLP) and mycobacterial interspersed repeat unit-variable number tandem repeat (MIRU-VNTR) analyses. Six PstI and 17 BstEII IS<it>900</it>-RFLP, 31 multiplex [SnaBI-SpeI] PFGE profiles and 23 MIRU-VNTR profiles were detected. AFLP gave insufficient discrimination of isolates for meaningful genetic analysis. Point estimates for Simpson's index of diversity calculated for the individual typing techniques were in the range of 0.636 to 0.664 but a combination of all three methods increased the discriminating power to 0.879, sufficient for investigating transmission dynamics. Two predominant strain types were detected across Europe with all three typing techniques. Evidence for interspecies transmission between wildlife and domestic ruminants on the same property was demonstrated in four cases, between wildlife species on the same property in two cases and between different species of domestic livestock on one property.</p> <p>Conclusion</p> <p>The results of this study showed that it is necessary to use multiple genotyping techniques targeting different sources of genetic variation to obtain the level of discrimination necessary to investigate transmission dynamics and trace the source of <it>Map </it>infections. Furthermore, the combination of genotyping techniques may depend on the geographical location of the population to be tested. Identical genotypes were obtained from <it>Map </it>isolated from different host species co-habiting on the same property strongly suggesting that interspecies transmission occurs. Interspecies transmission of <it>Map </it>between wildlife species and domestic livestock on the same property provides further evidence to support a role for wildlife reservoirs of infection.</p