In the early 2000’s scientists noticed an increase in biomass production in the Sahel for the period 1982-2002 (a process which is referred to as ‘greening’). The goal of this thesis was to investigate the greening phenomenon at the local scale in 4 villages in south-central Niger and compare results of the investigation with the already available regional scale studies. Theoretical starting points for this study were: the micro-macro scale paradox in the Sahelian studies and the critical research about ‘received wisdoms’ and environmental narratives of African landscapes. Methods for this study were: visual interpretation of remote sensing data (aerial photographs and satellite images) and collection of farmers’ knowledge during a fieldtrip (PRA and personal interviews). This study identified that greening was not a uniform or strong process in four villages. Greening primarily concerned appearance of new trees, whereas big old trees continued to disappear. Not only rainfall was a reason behind greening, but also human factor played a substantial role. The greening phenomenon should be investigated critically, as far as its meaning for the affected land users is not clear.

Pearl millet [Pennisetum glaucum (L.) R.Br.] production under subsistence farmer management on the sandy soils of southwestern Niger is faced with many challenges, including declining soil fertility, highly variable and scarce rainfall and poor resource base of the peasant farmers in the region. This study was conducted to evaluate the potential of management to increase yield and water use efficiency of pearl millet grown on two farmers’ fields in Niger during two growing seasons, 2003 and 2004. The management practices tested were: 1) Five manure treatments (no manure, transported manure, current corralling, a year after corralling, and two years after corralling); 2) The microdose technology (20 kg di-ammonium phosphate ha-1, and 20 kg di-ammonium phosphate ha-1 + 10 kg urea ha-1); and lastly, 3) Three different pearl millet cultivars (Heini Kirei, Zatib, and ICMV IS 89305). In both growing seasons, manure had the greatest effect on the yield and water use of pearl millet at both sites. In 2003 grain yields were 389 kg ha-1 in the NM treatment and 1495 kg ha-1 in the C0 treatment at Banizoumbou whereas at Bagoua, the NM treatment had 423 kg ha-1 vs. 995 kg ha-1 in the C0 treatment. In 2004, the NM treatment at Banizoumbou had 123 kg ha-1 grain yield and the C0 treatment had 957 kg ha-1 whereas at Bagoua the NM treatment had 506 kg ha-1 vs. 1152 kg ha-1 in the C0 treatment. Residual effects of manure led to grain yields in the C1 and C2 treatments which were more than twice as high as in the NM treatment. The improved cultivars were generally superior for grain yields, whereas the local landrace was superior for straw yields at both sites. Root zone drainage was decreased by between 50 to 100 mm, and water use increased by the same amount in the current corrals at the two sites during the two growing seasons. Increased water use under corralling and presence of residual profile moisture at the end of each of the two seasons suggested that water did not limit pearl millet production at the two sites.

Thèse de doctorat : Sciences économiques : Lyon 2 : 2000. / Titre provenant de l'écran-titre. Bibliogr.

Thèse de doctorat : Sociologie : Rennes 2 : 2008. / Bibliogr. f. 327-331. Annexes. Lexique Songhay.

Meren field, located offshore Niger Delta, is one of the most prolific oil-producing fields in the Niger Delta. The upper Miocene D-07, D-08 and E-01 oil sands comprise a series of stacked hydrocarbon reservoirs in Block 2 of Meren field. These reservoir sandstones were deposited in offshore to upper shoreface environments. Seven depositional facies were identified in the studied interval, each with distinct lithology, sedimentary structures, trace fossils, and wire-line log character. The dominant lithofacies are (1) locally calcite-cemented highly-bioturbated, fine-grained sandstones, (middle to lower shoreface facies); (2) cross-bedded, fine- to medium-grained well-sorted sandstones (upper shoreface facies); (3) horizontal to sub-horizontal laminated, very-fine- to fine-grained sandstone (delta front facies); (4) massive very-fine- to fine-grained poorly-sorted sandstone (delta front facies); (5) muddy silt- to fine-grained wavy-bedded sandstone (lower shoreface facies); (6) very-fine- to fine-grained sandy mudstone (lower shoreface facies); and (7) massive, silty shales (offshore marine facies). Lithofacies have distinct mean petrophysical properties, although there is overlap in the range of values. The highest quality reservoir deposits are cross-bedded sands that were deposited in high-energy upper shoreface environments. Calcite cements in lower shoreface facies significantly reduce porosity and permeability. Integration of core and wire-line log data allowed porosity and permeability to be empirically determined from bulk density. The derived equation indicated that bulk density values could predict 80% of the variance in core porosity and permeability values. Three parasequence sets were interpreted, including one lower progradational and two upper retrogradational parasequence sets. The progradational parasequence set consists of upward-coarsening delta front to upper shoreface facies, whereas the upward-fining retrogradational parasequence sets are composed of middle to lower shoreface deposits overlain by offshore marine shales. The limited amount of core data and the relatively small area of investigation place serious constraints on stratigraphic interpretations. Two possible sequence stratigraphic interpretations are presented. The first interpretation suggests the deposits comprise a highstand systems tract overlain by a transgressive systems tract. A lowstand systems tract is restricted to an incised valley fill at the southeastern end of the study area. The alternate interpretation suggests the deposits comprise a falling stage systems tract overlain by transgressive systems tract.

Copper metallothionein (Cu-MT) was extracted from the induced biomass of Aspergillus niger. The crude extract (FI), obtained by cell homogenization, was partially purified by heat treatment (FII) and ultrafiltration (FIII). Further purification of the Cu-MT extract by affinity chromatography resulted in three major fractions, FIVa, FIVb and FIVc, of which fraction FIVc was considered to be the Cu-MT extract fraction. Fraction FIVc was re-chromatography on affinity chromatography and the eluted fraction showed a single peak (FIVc'). Spectrophotometric analysis of fraction FIVc' demonstrated a maximum absorption peak at 268 nm. Native and denatured electrophoretic analysis of fraction FIVc ' showed the presence of a single band with an estimated molecular weight of 9.5 and 10.0 kDa, respectively. Inhibition of mushroom tyrosinase (PPO) by the Cu-MT extracts was investigated, using selected phenolic substrates, including catechin, chlorogenic acid, catechol, 4-methylcatechol, caffeic acid, L-3,4-dihydroxyphenylalanine, 3,4-dihydroxyphenylacetic acid, 3-( p-hydroxyphenyl) propionic acid, p-hydroxyphenylpyruvic acid, p- and m-cresol. The results showed that the inhibitory effect of the Cu-MT extract increased with the degree of purification. The results revealed that the Cu-MT extracts were effective inhibitors of PPO activity and the best inhibitory effect was demonstrated with catechin as substrate; however, PPO activity was not inhibited by the Cu-MT extract when p-hydroxyphenylpyruvic acid and p- and m-cresol were used as substrates. The results also showed that the Cu-MT extracts exhibited different types of inhibition, including mixed, competitive and uncompetitive on PPO activity. In addition, the experimental findings indicated that the nature and degree of enzymatic inhibitions by the Cu-MT extracts were dependent upon the structural nature of the substrates as well as the methods including, spectrophotometer and polarograph, used for the detection of enzyme

Two natural enzymatic browning inhibitors, copper-metallothionein (Cu-MT) and polyphenol esterase (PPE), were obtained from A. niger and investigated. Reflectance measurements, expressed as L (lightness variable) and a (red to green degree of color) were used to compare, over extended periods of time, the relative inhibitory effectiveness of Cu-MT and PPE to those observed with the use of selected chemicals including ascorbic acid (AA), citric acid (CA), ethylenediaminetetraacetic acid (EDTA), sodium bisulfite (NaHSO3) and 4-hexylresorcinol (4HR), in the prevention of browning on the cut surfaces of selected food products such as apple and potato slices as well as freshly prepared apple juice. Treatment of each food product required an optimum concentration of the selected inhibitor for the inhibition of browning. (Abstract shortened by UMI.)

While a lot of ink has been spilled and numerous papers devoted to the variegated causes of the Niger Delta conflict, what has been conspicuously moot in the literature is their integration into a sufficient explanatory system to facilitate the intelligibility of empirical data and support effective policy intervention. Also, while writers have investigated the internal dimensions of the conflict, little systematic attention has been paid to its international dimensions. The study proposes to fill these gaps in existing literature through a two-level analysis of the Niger Delta Conflict: (1) internal (2) international. The internal level is anchored on a four-dimensional explanation which argues that political and economic factors are the root causes of the Niger Delta conflict, with environmental and social-security factors as the proximate causes. At the international level, the study probes the role of the international community in the moderation of the Niger Delta conflict and concludes with an appraisal of the extent to which the internationalisation of the conflict engendered both attitudinal and policy shifts on the parts of key players. Problematising the usefulness of majoritarian democracy for resource starved plural societies, the study canvasses, inter alia, the implementation of consociational mechanisms in the Nigerian political process as a more effective way of mitigating the seething cauldron of conflicts in the Niger Delta, and promoting inter-ethnic equity and amity in Nigeria as a whole. / Thesis (M.A.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.

No description available.

A crude enzyme extract (FI) of polyphenol esterase (PPE), obtained from the microbial culture of Aspergillus niger, was partially purified by ammonium sulfate precipitation. The partially purified fraction (FII) was subjected to further purification by ion-exchange chromatography, which resulted in five separated fractions, FIIIa, FIIIb, FIIIc, FIIId and FIIIe), where FIIIa showed the highest PPE activity towards chlorogenic acid, as substrate. The biocatalysis of the PPE with a wide range of mono- and diphenols, as substrates, was shown to inhibit mushroom tyrosinase (PPO) activity. Fraction FIIIa exhibited an inhibitory effect, measured spectrophotometrically, on PPO activity with the monophenols, including 4-hydroxyphenylpyruvic acid and m- and p-cresols and the diphenols, including chlorogenic acid, catechin, 3,4-dihydroxyphenylacetic acid (DHPAA), L-3,4-dihydroxyphenylalanine (L-DOPA), 4-methylcatechol, catechol and caffeic acid; however, using the polarographic method, the inhibition of PPO activity by PPE biocatalysis occurred with the diphenols but not with the monophenols. The selected enzymatic fraction FIIIa was further purified, using size-exclusion chromatography, which resulted in three fractions FIVa, FIVb and FIVc. Although fraction FIVc contained the highest PPE activity, it showed a lack of enzyme stability. Fraction FIIIa was therefore, subjected to further purification by hydrophobic interaction chromatography thereby yielding fractions FVa, FVb, FVc, FVd, FVe, FVf and FVg, where fraction FVc showed the highest PPE activity. The denatured electrophoretic analysis of fraction FVc showed the presence of one major band, with a molecular weight of 60 kDa. The successive purification of PPE resulted in a marked increase in the inactivation of PPO activity with diphenols, as demonstrated by both the lower I50 and inhibition dissociation constant (Ki) values. The purified fraction FVc was shown to exhibit, spectrophotometrically, a competitive and un