Detecting recent changes in the demographic parameters of drosophilid populations from western and central Africa

Previous genetic studies showing evidence of past demographic changes in African drosophilids suggested that these populations had strongly responded to Quaternary climate changes. We surveyed nine species of Zaprionus, a drosophilid genus mostly present in Africa, in forests located between southern Senegal and Gabon. The mitochondrial COI gene showed contrasted levels of sequence variation across species. Populations of the only cosmopolitan species of the genus, Z. indianus, and of its closely related sibling species, Z. africanus, are highly polymorphic and appear to have undergone a continuous population expansion beginning about 130,000 years ago. Five less variable species probably underwent a population expansion beginning only about 20,000–30,000 years ago. One of them, Z. taronus, was significantly structured between forest blocks. The last two species were nearly monomorphic, probably due to infection by Wolbachia. These results are similar to those obtained in three species from the melanogaster subgroup, and may be typical of the responses of African drosophilid populations to glacial cycles.     

Ground roll attenuation using the S and x-f-k transforms

Ground roll, which is characterized by low frequency and high amplitude, is an old seismic data processing problem in land‐based seismic acquisition. Common techniques for ground roll attenuation are frequency filtering, f‐k or velocity filtering and a type of f‐k filtering based on the time‐offset windowed Fourier transform. These techniques assume that the seismic signal is stationary. In this study we utilized the S, x‐f‐k and t‐f‐k transforms as alternative methods to the Fourier transform. The S transform is a type of time‐frequency transform that provides frequency‐dependent resolution while maintaining a direct relationship with the Fourier spectrum. Application of a filter based on the S transform to land seismic shot records attenuates ground roll in a time‐frequency domain. The t‐f‐k and x‐f‐k transforms are approaches to localize the apparent velocity panel of a seismic record in time and offset domains, respectively. These transforms provide a convenient way to define offset or time‐varying reject zones on the separate f‐k panel at different offsets or times.     

Non-adiabatic interactions in excitedC 2 H molecules and their relationship toC 2 formation in comets

A unified picture of the photodissociation of theC ₂ H radical has been developed using the results from the latest experimental and theoretical work. This picture shows that a variety of electronic states ofC ₂ are formed during the photodissociation of theC ₂ H radical even if photoexcitation accesses only one excited state. This is because the excited states have many avoided corssings and near intersections where two electronic states come very close to one another. At these avoided crossings and near intersections, the excited radical can hop from one electronic state to another and access new final electronic states of theC ₂ radical. The complexity of the excited state surfaces also explains the bimodal rotational distributions that are observed in all of the electronic states studied. The excited states that dissociate through a direct path are limited by dynamics to produceC ₂ fragments with a modest amount of rotational energy, whereas those that dissociate by a more complex path have a greater chance to access all of phase space and produce fragments with higher rotational excitation. Finally, the theoretical transition moments and potential energy curves have been used to provide a better estimate of the photochemical lifetimes in comets of the different excited states of theC ₂ H radical. The photochemically active states are the 2²₊, 2²II, 3²II, and 3²₊, with photodissociation rate constants of 1.0×10^–6, 4.0×10^–6, 0.7×10^–6, and 1.3×10^–6s^–1, respectively. These rate constants lead to a total photochemical lifetime of 1.4×10⁵ s.     

Incorporation of chitosan and glass substrate for improvement in adsorption,separation, and stability of TiO<Subscript>2</Subscript> photodegradation

It is demonstrated that single titanium dioxide (TiO₂) has high potential for photodegradation of pollutants. However, it is still far from becoming an effective photocatalyst system, due to issues of adsorption process, separation, as well as dissolution. Therefore, this study highlights the high adsorption capacity, simplified separation, and the promising stability of TiO_2(SY) (synthesized via sol–gel method) photocatalyst, fabricated using chitosan–TiO_2(SY) and supported by glass substrate (Cs–TiO_2(SY)/glass substrate) photocatalysts. Chitosan (Cs), with abundant –R–NH and NH₂ groups, promotes the adsorption sites of methyl orange (MO) and OH groups for major attachment to TiO_2(SY). Meanwhile, the glass substrate increases stability and assists separation of the photocatalysts. Initially, nano-TiO_2(SY) has been characterized using high-resolution transmission electron microscope. Cs–TiO_2(SY)/glass substrate was fabricated via dip-coating. The distribution and interface between the photocatalytic components were characterized by Fourier transform infrared absorption spectroscopy, UV–Vis diffuse reflectance spectroscopy, field emission scanning electron microscopy, and energy-dispersive spectrometer. UV–Vis analysis of the multilayer photocatalyst (2, 4, 6, and 8 layers) was further carried out by the adsorption–photodegradation, with MO as model of pollutant. Seventy percent of the total removal of MO via optimized eight layers of photocatalyst was achieved within 1 h of UV irradiation. The adsorption photocatalyst achieved 50 % with no exposure to UV light for 15 min of irradiation. It is concluded that suitable photocatalytic conditions and sample parameters possessing the multilayer photocatalyst of Cs–TiO_2(SY) are beneficial toward the adsorption–photodegradation process in wastewater treatment.     

Richness of drilling sludge taken from an oil field quagmire: potentiality and environmental interest

The drilling sludge represents a complex environment, containing several types of pollutants that can be even used as nutrients by indigenous microorganisms, like hydrocarbon-degrading bacteria, having good potentialities for the biodegradation of petroleum products. In this study, a drilling sludge was collected from drilling quagmire. Physicochemical characterization of the drilling sludge was done. Its mineralogy was obtained by diffractometry. The indigenous aerobic sludge hydrocarbon-degrading bacteria were checked by counting on Bushnell–Haas medium, and their isolation and purification were performed by the selective microbial enrichment technique in a batch-enriched Bushnell–Haas culture, with crude oil as the sole carbon source. Isolates were characterized, and their power to emulsify crude oil was determined by emulsification index and oil spreading tests. Environmental conditions in the quagmire, like temperature, pH and moisture, were suitable for bacterial development. Physicochemical characteristics of the drilling sludge showed richness in chemical elements and promote microbial life. Fifteen different colonies of hydrocarbon-degrading bacteria were isolated and purified; they have diversified morphological and microscopic aspects. Most isolates had a good emulsification index (between 31 and 76 %). Oil spreading test gave clear zone diameters >28 mm, with a maximum of 60 mm. The results of these investigations prove the elementary, mineralogy and microbiology richness of drilling sludge and reveal the high diversity of its indigenous hydrocarbon-degrading bacterial flora. These properties can be exploited for the own restoration of petroleum quagmires in oil fields, by means of bioremediation applications and by integrating indigenous microorganisms.     

Relationship between geo-structural evolution and development of karstic systems in the culminating area of Ouarsenis (West Algeria)

The Ouarsenis area is one of the most developed karstic systems of Algeria. It is a karst reservoir drinking water with a population of more than 50,000 people taking fully benefit from it. To understand the development of this karstic system, the local tectonic history of the four main mountain ranges of this culminating area (Ouarsenis) has been analyzed. Although previously identified primarily Cenozoic tectonic activities have been observed, a set of NW-SE joints intersecting the Jurassic limestone has been associated to a post-nappes tectonic events. Moreover, numerous joint sets oriented NNE/SSW have been identified almost over the entire culminating area. These joints are the direct consequence of the following stress history: (i) a NW/SE shortening responsible for a major overlap and the first fold (P1) phase, (ii) a second NNE/SSW shortening stage responsible for the second folding (P2) phase associated with 70° N sinistral strike-slip trend, (iii) a WNW/ESE extension phase resulting from the change of σ ₃ stress vertical axis, and (iv) a shearing stress creating a 120° N sinistral strike-slip fault. Only the late phases are responsible of the development of joints, which have been karstified later on. Indeed, significant families of karstified joints, i.e., 20° and 70° N have been found. These joints are related to the extensional and shearing modes, respectively, and linked to a particular in situ karstogenesis. Moreover, this study suggests an ancient establishment of the karstic systems in the Ouarsenis region in at least two stages: pre-figured and activated behaviors during the Cenozoic.     

Role of construction of large dams on river morphology (case study: the Karkheh dam in Iran)

Unfortunately in developing countries, human activities without attention to the environmental aspects damage to nature. For example, construction of large dams dries wetlands in southwest of Iran. Also, construction of dams is a very important factor for morphological changes. The case study of this research is downstream of the Karkheh dam. This dam is the largest Earth dam in Iran and locates in southwest of Iran. It was constructed in 1999. Small sinuosity coefficient of zone near to dam has been illustrated by satellite images in 2002 and 2014. This subject shows instability of this part of reach; also, the results of Shulits equation illustrate that this part is instable. But, increasing of morphological characteristics (sinuosity coefficient, central angle, and relative radius) show that stability of this reach is increasing. Surveying confirm this matter and shows that severe erosion in upstream and sedimentation in downstream of reach is finishing. Also, it is observed that flow discharge reduced (?56 %) after construction of dam and average width of river reduced (?21 %) from 2002 to 2014. In the early years after the construction of the dam, sediment discharge reduced considerably (?14 %) from Pay-e-Pol to Abdol Khan hydrometric stations. Increasing of morphological characteristics (especially at zones near to dam) and decreasing changes of bed level (sedimentation and erosion) prove that effects of dam are overcoming on effects of other factors, and these effects are permanent in long term.