When solids meet solids: A glimpse into dust mixture explosions

Mixing an inert solid or a less flammable compound with a combustible dust can be regarded as a direct application of the inherent safety principle of moderation. An experimental investigation was carried out to determine the evolution of the ignition sensitivity and the explosion severity of such various mixtures as a function of their compositions. It demonstrates that the introduction of small amounts of highly combustible powders (such as sulphur or nicotinic acid) to a less flammable dust (such as microcrystalline cellulose or carbon black) can strongly influence the ignition sensitivity as well as the explosion severity.It has notably been shown that the ignition sensitivity of solid/solid mixtures significantly rises up when only 10–5%wt. of highly flammable dust is introduced. Simple models can often be applied to estimate the minimum ignition energy, minimum ignition temperature and minimum explosive concentration of such mixtures. Concerning the dust explosivity, three cases have been studied: mixtures of combustibles dusts without reaction, dusts with reactions between the powders, combustible dusts with inert solid. If the evolution of the maximum explosion pressure can be estimated by using thermodynamic calculations, the maximum rate of pressure rise is more difficult to predict with simple models, and both combustion kinetics and hydrodynamics of the dust clouds should be taken into account. These results were also extended to flammable dust/solid inertant mixture. They clearly show that the concentration of solid inertant at which the ignition is not observed anymore could reach 95%wt. As a consequence, the common recommendation of solid inertant introduction up to 50–80%wt. to prevent dust explosion/ignition should be reconsidered.     

A meta‐analysis of the antecedents of work–family enrichment

This study meta‐analytically examined theoretically derived antecedents of both directions of work–family enrichment (sometimes labeled facilitation or positive spillover), namely, work–family enrichment and family–work enrichment. Contextual and personal characteristics specific to each domain were examined. Resource‐providing (e.g., social support and work autonomy) and resource‐depleting (e.g., role overload) contextual characteristics were considered. Domain‐specific personal characteristics included the individuals' psychological involvement in each domain, the centrality of each domain, and work engagement. Results based on 767 correlations from 171 independent studies published between 1990 and 2016 indicate that several contextual and personal characteristics have significant relationships with enrichment. Although those associated with work tend to have stronger relationships with work–family enrichment and those associated with family tend to have stronger relationships with family–work enrichment, several antecedent variables have significant relationships with both directions of enrichment. Resource‐providing contextual characteristics tend to have stronger relationships with enrichment than do resource‐depleting characteristics. There was very little evidence of gender being a moderator of relationships between contextual characteristics and enrichment. Lastly, meta‐analytic structural equation modeling provided evidence that a theoretical path model wherein work engagement mediates between several contextual characteristics and enrichment is largely generalizable across populations.     

Mediterranean forests,land use and climate change: a social-ecological perspective

Regional Environmental Change - Mediterranean forests are found in the Mediterranean basin, California, the South African Cape Province, South and southwestern Australia and parts of Central Chile....     

Extended family structure in the ant Formica paralugubris: the role of the breeding system

In populations of various ant species, many queens reproduce in the same nest (polygyny), and colony boundaries appear to be absent with individuals able to move freely between nests (unicoloniality). Such societies depart strongly from a simple family structure and pose a potential challenge to kin selection theory, because high queen number coupled with unrestricted gene flow among nests should result in levels of relatedness among nestmates close to zero. This study investigated the breeding system and genetic structure of a highly polygynous and largely unicolonial population of the wood ant Formica paralugubris. A microsatellite analysis revealed that nestmate workers, reproductive queens and reproductive males (the queens' mates) are all equally related to each other, with relatedness estimates centring around 0.14. This suggests that most of the queens and males reproducing in the study population had mated within or close to their natal nest, and that the queens did not disperse far after mating. We developed a theoretical model to investigate how the breeding system affects the relatedness structure of polygynous colonies. By combining the model and our empirical data, it was estimated that about 99.8% of the reproducing queens and males originated from within the nest, or from a nearby nest. This high rate of local mating and the rarity of long-distance dispersal maintain significant relatedness among nestmates, and contrast with the common view that unicoloniality is coupled with unrestricted gene flow among nests. Received: 8 February 1999 / Received in revised form: 15 June 1999 / Accepted: 19 June 1999     

湿式氧化技术的应用现状与发展

湿式氧化技术是上世纪50年代发展起来的一项在高温高压下处理废水的技术。50年来,被广泛地应用于高浓度难降解有机废水和城市污水厂污泥的处理。着重介绍了当今世界上几种主要的湿式氧化工艺的工艺特点及应用现状,为我国湿式氧化技术的工业应用提供参考,并提出了今后的研究重点。     

Evidence for a significant contribution of wood burning aerosols to PM2.5 during the winter season in Paris,France

Although particulate emissions from residential wood burning have become a subject of great scientific concern for a few years, data related to their impact on the air quality of large European urban centres are still missing. In the present study, we investigated the chemical and optical properties of fine (PM_2.5) carbonaceous aerosols in Paris during the 2005 winter season in order to track the presence of wood burning emissions in such a large city. The use of a seven wavelength Aethalometer allowed us to document shortwave light absorption by brown-carbon-containing organic aerosols of biomass burning origin. In particular, a well-marked diurnal pattern of the spectral dependence of light absorption, with maxima during the night, could be observed every day of the campaign and attributed to wood burning emissions. Relatively high absorption Ångstrom exponents and WSOC/OC ratios (respectively 1.25 and 0.35 on average for the period of study) also indicated the importance of biomass burning aerosols in the Paris atmosphere in winter. Finally, a rough estimate of the contribution of wood burning carbonaceous aerosols to PM_2.5 could be achieved. This contribution was found to be as high as 20 ± 10% on average at the Paris background site investigated here.     

Extra-pair paternity in the monogamous Alpine marmot revealed by nuclear DNA microsatellite analysis

The genetic parentage and pedigrees of 35 litters from 12 family groups of monogamous Alpine marmot (Marmota marmota) in the French Alps were analyzed using six hypervariable sequence repeat nuclear loci (microsatellites). All of the members of these family groups were sampled during a 5-year period. Hairs taken directly from animals served as a source of DNA for amplification of the loci. Our results indicate that the genetic mating system of the Alpine marmot is quite different from a strictly monogamous breeding system. Extra-pair paternity occurred in 11 of the 35 litters (31.4%). Of the 134 juveniles typed, 26 (19.4%) could be attributed to extra-pair copulation (EPC). We examine hypotheses which could explain the evolution of EPC and discuss the different patterns of extra-pair mating. Received: 11 July 1997 / Accepted after revision: 23 May 1998     

Fate of RDX and TNT in agronomic plants

Phytoremediation is of great interest to remediate soil contaminated with hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and 2,4,6-trinitrotoluene (TNT). The ability of 4 agronomic plants (maize, soybean, wheat and rice) to take up these explosives and their fate in plants were investigated. Plants were grown for 42 days on soil contaminated with [(14)C]RDX or [(14)C]TNT. Then, each part was analyzed for its radioactivity content and the percentage of bound and soluble residues was determined following extractions. Extracts were analyzed by radio-HPLC. More than 80% of uptaken RDX was translocated to aerial tissues, up to 64.5 mgg(-1) of RDX. By contrast, TNT was little translocated to leaves since less than 25% of uptaken TNT was accumulated in aerial parts. Concentrations of TNT residues were 20 times lower than for RDX uptake. TNT was highly metabolized to bound residues (more than 50% of radioactivity) whereas RDX was mainly found in its parent form in aerial parts.     

Uranium oxide and other airborne particles deposited on cypress leaves close to a nuclear facility

Enhanced activity of actinides and some decay products has been reported for the leaves of cypress trees (Chamaecyparis nootkatensis) at the edge of the Malvési uranium-processing facility, southwestern France. The enhanced activity is due to the release of actinides via the smokestacks and from artificial ponds inside the facility. This study was conducted to characterize airborne particulate matter deposited on the leaf surfaces and to investigate whether or not radioactive particles may be identified. Air-dried leaf samples were examined by scanning electron microscopy, in combination with energy-dispersive X-ray spectrometry. The samples were scanned systematically in both secondary and backscattered electron modes. Particles ranging in size from <200 nm to ~40 μm were found on most portions of the adaxial leaf surface, but they are especially abundant at the boundary between facial and lateral leaves. The majority of the analyzed particles could be attributed to five principal classes: carbonates, silicates, sulfates, oxides/hydroxides, and halides. In addition, other types of particles were found, including Fe alloys; scheelite-group phases; phosphates; sulfides; and fly ash spheres. Similar particles were also observed on the surface of a wheat sample used for comparison. Of special interest are U-rich particles, which were observed on the cypress leaves only and which were identified as U oxides, except for one particle, which was a U-oxide-fluoride. These U-rich particles were released into the atmosphere by the nuclear facility prior to their deposition on the leaf surfaces. As most of the U-rich particles are <2.5 μm across, they are respirable. Once inhaled, particles containing alpha-emitting isotopes represent a potentially long-term source of ionizing radiation inside the lungs and thus, pose a threat to the health of people living nearby.