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Summary: North Africa has a great diversity of indigenous sheep breeds whose origin is linked to its environmental characteristics and to certain historical events that took place in the region. To date, few genome‐wide studies have been conducted to investigate the population structure of North African indigenous sheep. The objective of the present study was to provide a detailed assessment of the genetic structure and admixture patterns of six Maghreb sheep populations using the Illumina 50K Ovine BeadChip and comparisons with 22 global populations of sheep and mouflon. Regardless of the method of analysis used, patterns of multiple hybridization events were observed within all North African populations, leading to a heterogeneous genetic architecture that varies according to the breed. The Barbarine population showed the lowest genetic heterogeneity and major southwest Asian ancestry, providing additional support to the Asian origin of the North African fat‐tailed sheep. All other breeds presented substantial Merino introgression ranging from 15% for D'man to 31% for Black Thibar. We highlighted several signals of ancestral introgression between North African and southern European sheep. In addition, we identified two opposite gradients of ancestry, southwest Asian and central European, occurring between North Africa and central Europe. Our results provide further evidence of the weak global population structure of sheep resulting from high levels of gene flow among breeds occurring worldwide. At the regional level, signs of recent admixture among North African populations, resulting in a change of the original genomic architecture of minority breeds, were also detected. [ABSTRACT FROM AUTHOR]

This paper describes an experimental and modeling study of the oxidation of methyl and ethyl butanoates in a shock tube. The ignition delays of these two esters mixed with oxygen and argon for equivalence ratios from 0.25 to 2 and ester concentrations of 0.5% and 1% were measured behind a reflected shock wave for temperatures from 1250 to 2000 K and pressures around 8 atm. To extend the range of studied temperatures in the case of methyl butanoate, two sets of measurements were also made in a jet-stirred reactor at 800 and 850 K, at atmospheric pressure, at residence times varying between 1.5 and 9 s and for equivalence ratios of 0.5 and 1. Detailed mechanisms for the combustion of methyl and ethyl butanoates have been automatically generated using a version of EXGAS software improved to take into account these oxygenated reactants. These mechanisms have been validated through comparison of simulated and experimental results in both types of reactor. The main reaction pathways have been derived from reaction flux and sensitivity analyses performed at different temperatures. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 226–252, 2010 [ABSTRACT FROM AUTHOR]

Ignition delay times of cyclopentene–oxygen–argon mixtures were measured behind reflected shock waves. Mixtures contained 0.5% or 1% of hydrocarbons for equivalence ratios ranging from 0.5 to 1.5. Reflected shock wave conditions were as follows: temperatures from 1300 to 1700 K and pressures from 7 to 9 atm. When compared with the previous results obtained under similar conditions, it can be observed that the reactivity of cyclopentene is much lower than that of cyclohexene, but very close to that of cyclopentane. A kinetic mechanism recently proposed for the combustion of cyclopentene in a flame has been used to model these results, and a satisfactory agreement is obtained. The main reaction pathways have been derived from the flow rate, simulated temporal profiles of products, and sensitivity analyses. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 40: 25–33, 2008 [ABSTRACT FROM AUTHOR]

The oxidation of several binary mixtures 1-hexene/toluene has been investigated both in a shock tube and in a jet-stirred reactor (JSR). The self-ignition behavior of binary mixtures was compared to that of neat hydrocarbons studied under the same conditions. Furthermore, molecular species concentration profiles were measured by probe-sampling and GC/MS, FID, TCD analyses for the oxidation of the mixtures in a JSR. Experiments were carried out over the temperature range 750–1860 K. Mixtures were examined under two pressures 0.2 and 1 MPa, with 0.1% initial concentration of fuel. The equivalence ratio was varied from 0.5 to 1.5. The experiments were modeled using a detailed chemical kinetic reaction mechanism. The modeling study showed that interactions between hydrocarbons submechanisms were not limited to small reactive radicals. Other types of interactions involving hydrocarbon fragments derived from the oxidation of the fuel components must be considered. These interactions mainly consist of hydrogen abstraction reactions. For example, benzyl radical that is the major radical produced from the oxidation of toluene at high temperature can abstract hydrogen from 1-hexene and their products such as hexenyl radicals. Similarly, propyl, allyl, and hexenyl radicals that are the major radicals produced during 1-hexene oxidation at high temperature can abstract hydrogen from toluene. Improved modeling was achieved when such interaction reactions were included in the model. Good agreement between experimental and calculated data was obtained using the proposed detailed chemical kinetic scheme. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 518–538, 2007 [ABSTRACT FROM AUTHOR]