Land degradation,natural resources and local knowledge in the sahel zone of Burkina Faso

This paper proposes a conceptual model that integrates physical and ecological aspects with human aspects of land degradation through a multidisciplinary approach. The model was applied at the local level in a case study in northern Burkina Faso. Assessments of the degradation of the vegetation cover from aerial photographs and a satellite image were analysed in the framework of the model. Another input to the model was results from interviews and field visits with peasants living in the area.The local knowledge of the physical symptoms of land degradation and of the physical variables, eg rainfall and wind, is very close to the scientific logic. However, people do not generally see the links between these variables and the symptoms. Likewise, they do not perceive land degradation to be influenced in any way by human actions. Instead, the cause of land degradation is attributed to God, Allah. Thus, an important field of intervention for governments and development agencies should be to make people aware of their role in land management.     

Seasonal abundance and vertical distribution of crab larvae in Delaware Bay

Larvae of 15 species or genera of crabs were collected and identified during a six month (May 26 to October 28, 1978) study in the mouth of Delaware Bay. Seasonal abundance and vertical distribution of each species were investigated. Most species studied had peak abundance in July and August except forCancer irroratus andOvalipes ocellatus which showed peak occurrence in May and June, respectively. Larvae of species strongly dependent on estuarine habitats, such asUca spp.,Pinnixa chaetopterana, andP. sayana, showed a tendency to congregate in near-bottom waters where net flow of water is landward, thus favoring retention within the estuary. Larvae ofOvalipes ocellatus, Cancer irroratus, andCallinectes sapidus were more common at the surface. This vertical distribution suggests that these larvae are flushed out of the estuary. The mechanisms of recruitment and replenishment of adult populations within the estuary would therefore depend on migration of megalopa and juveniles. *** DIRECT SUPPORT *** A01BY019 00006     

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Generalized Regularization Techniques with Constraints for the Analysis of Solar Bremsstrahlung X-ray Spectra

Hard X-ray spectra in solar flares provide knowledge of the electron spectrum that results from acceleration and propagation in the solar atmosphere. However, the inference of the electron spectra from solar X-ray spectra is an ill-posed inverse problem. Here, we develop and apply an enhanced regularization algorithm for this process making use of physical constraints on the form of the electron spectrum. The algorithm incorporates various features not heretofore employed in the solar flare context: Generalized Singular Value Decomposition (GSVD) to deal with different orders of constraints; rectangular form of the cross-section matrix to extend the solution energy range; regularization with various forms of the smoothing operator; and preconditioning of the problem. We show by simulations that this technique yields electron spectra with considerably more information and higher quality than previous algorithms.     

Acidic compounds in biodegraded petroleum

Twelve oil samples have been characterised by titration, FT-IR and chromatographic analysis to determine the differences between the organic acid composition of biodegraded and non-biodegraded oils. The biodegraded oils have higher total acid and total base contents, both by titration and extraction. The molecular weight ranges of the extracted acids are lowest in the biodegraded oils, and the equivalent weight calculations indicate a dominance of multi-functional molecules. Gel permeation chromatography gives a molecular weight range with most of the molecules between 300 and 500 g/mol. FT-IR shows that the extracted acids from biodegraded oils are more carboxylic and aliphatic while the non-degraded oils are more phenolic. Molecular analysis of the derivatised extracts give UCM envelopes for biodegraded oils, and no molecular identification. The results indicate that the acidic constituents in biodegraded oils are a product of the biodegradation, as the composition is very different from the non-biodegraded oils.     

Flexural uplift of a lithospheric slab near the Vema transform (Central Atlantic): Timing and mechanisms

The Vema Transverse Ridge (VTR) is a prominent, long and narrow topographic anomaly that runs for over 300 km along a sea floor spreading flow line south of the Vema transform at 11° N in the Atlantic. It rises abruptly about 140 km from the axis of the Mid-Atlantic Ridge (MAR) in 10 Myr old crust and runs continuously up to 25 Myr old crust. It reaches over 3 km above the predicted lithospheric thermal contraction level. It is absent in crust younger than 10 Myr; thus, the uplift of the VTR must have ended roughly 10 Ma. The VTR is interpreted as the exposed edge of a flexured and uplifted slab of oceanic lithosphere that was generated at an 80 km long MAR segment. Based on satellite gravimetry imagery this MAR segment was born roughly 50 Ma and increased its length at an average rate of 1.6 mm/yr. Multibeam data show that the MAR-parallel sea floor fabric south of the VTR shifts its orientation by 5° to 10° clockwise in 11–12 Myr old crust, indicating a change at that time of the orientation of the MAR axis and of the position of the Euler rotation pole. This change caused extension normal to the transform, followed between 12 and 10 Ma by flexure of the edge of the lithospheric slab, uplift of the VTR at a rate of 2 to 4 mm/yr, and exposure of a lithospheric section (Vema Lithospheric Section or VLS) at the northern edge of the slab, parallel to the Vema transform. Ages of pelagic carbonates encrusting ultramafic rocks sampled at the base of the VLS at different distances from the MAR axis suggest that the entire VTR rose vertically as a single block within the active transform offset. A 50 km long portion of the crest of the VTR rose above sea level, subsided, was truncated at sea level and covered by a carbonate platform. Subaerial and submarine erosion has gradually removed material from the top of the VTR and has modified its slopes. Spreading half rate of the crust south of the transform decreased from 17.2 mm/yr between 26 and 19 Ma to 16.9 mm/yr between 19 and 10 Ma, to 13.6 mm/yr from 10 Ma to present. The slowing down of spreading occurred close in time to the change in ridge/transform geometry, suggesting that the two events are related. A numerical model relates lithospheric flexure to extension normal to the transform, suggesting that the extent of the uplift depends on the thickness of the brittle layer, consistent with the observed greater uplift of the older lithosphere along the VTR.     

Adsorbable Organic Halogens (AOX) in Polish Rivers – Levels and Changes

This paper presents results of a study on the concentration of adsorbable organic halogens (AOX) in water samples of the Oder River and its tributaries collected from 1998 to 2002. The Vistula River water for AOX was analysed in the period 2001–2002. The investigated waters of the Vistula near the mouth (Kiezmark) were more contaminated with AOX than the Oder near the mouth (Widuchowa, Krajnik Dolny). In general, AOX levels in the Polish rivers are comparable to the values found in the European rivers, e.g. the Rhine and the Ton. The research has shown that AOX were correlated with pH, total suspended solids, and the riverine flow. No relation between dissolved oxygen and redox potential and AOX was found out. During the flood period AOX, inorganic halogens (TIX), and mineral substances (sulfates) were analysed.     

盐下特低孔渗碳酸盐岩油藏高产带地震预测方法研究

肯吉亚克油田石炭系油藏属持低孔渗、异常高压碳酸盐岩油藏，它除了具有埋深大，非均质性强，油气成藏控制因素复杂等特点外，其上还覆盖巨厚盐丘，造成盐下地震反射时间和振幅畸变严重，地震成像差、信噪比低和分辨率低，给储层预测工作带来极大困难。如何正确预测油藏高产带分布规律是高效开发这类油藏的关键，本文研究从分析形成碳酸盐岩油藏高产带的主控因素入手，通过井震标定，优选反映碳酸盐岩岩相、岩溶、物性和裂缝的地震属性，结合地震、地质、测井、油藏工程和钻井资料，把盐下特低孔渗碳酸盐岩油藏高产带预测问题分解成构造解释、岩相预测、岩溶预测、物性预测、裂缝预测和综合评价等六个环节。宏观上，通过建立断裂、岩相、岩溶模式，定性预测储层分布有利区带；微观上，通过多参数储层特征反演和多属性综合分析，定量、半定量预测有利储层分布，有效解决盐下碳酸盐岩油藏高产带预测难题，基本搞清本区碳酸盐岩油藏高产带分布规律，为优选有利勘探和开发目标提供依据。文中提出的方法和技术对解决国内外碳酸盐岩油藏高产带预测和其他复杂储层预测问题有借鉴作用。