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Laterites developed from the weathering of chlorite schists have been studied in Tchollire region, North Cameroon. They include two profiles: a 5.5 m depth profile in Doudja site and a 12.3 m profile in Fimbe site.
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Decomposition processes of guild classes - groups of plant species with a similar ecology and way of life in the tropical rainforest are poorly understood. Leaf litter decomposition and nutrient dynamics of the following three gui...
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Decomposition processes of guild classes - groups of plant species with a similar ecology and way of life in the tropical rainforest are poorly understood. Leaf litter decomposition and nutrient dynamics of the following three guild classes were studied in the tropical rainforest of Ebom, Southwest Cameroon: the shade tolerant (ST), non-pioneer light demanding (NP) and pioneer (PI) species. The litterbag technique was used to assess mass loss and decay rate. During the 23 weeks of the field experiment, mean dry mass remaining of litter samples with standard error was between 29.16 +/- 18.17 and 60.19 +/- 18.81 % of initial litter dry mass for ST and PI, respectively. Decomposition rate constant (k) significantly ranged from 0.02 (PI) to 0.08 % week(-1) (ST). Initial nutrient contents widely varied among guild classes and revealed low nutrient contents in pioneer species and high contents in the other groups, except for Ca. Mean nutrient release from initial contents was significantly 50.62 % and 85.11 % respectively for N and Ca in ST; it varied significantly from 80.68 (NP) to 95.13 % (PI) for K and no significant nutrient releases were observed for Mg, Na and P. Thus, while litter decomposition was significantly influenced by guild classes, nutrient loss, with the exception of K, was not, and this should be explained by the short term of litter decomposition.
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This paper presents the first petro-structural data as well as morphological characterization of alluvial gold nuggets and related heavy minerals, from the Guiwa-Yangamo area within the Batouri goldfield (Cameroon). This area comp...
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This paper presents the first petro-structural data as well as morphological characterization of alluvial gold nuggets and related heavy minerals, from the Guiwa-Yangamo area within the Batouri goldfield (Cameroon). This area comprises metamorphic rocks including various gneisses and amphibolite, intruded by granite and granodiorite. Structural analysis reveals four main tectonic phases: the early (D-1) and D-2 deformations show ductile behavior, while D-3 and D-4 are ductile-brittle and late brittle respectively. Two main shear zones comprising the NW-SE- to NNW-SSE-trending ductile shear and ENE-WSW-trending ductile-brittle shear zone related respectively to D-2 and D-3 deformations are distinguished. These shear zones are well known in the Batouri goldfield as hosting gold-bearing quartz veins. Evidences for hydrothermal alteration such as chloritization, sericitization, and silification were identified in gold-bearing granitoids of the Batouri goldfield. Morphological characterization of alluvial gold grains and analysis of related heavy minerals indicate both long transport (> 1000m) and relatively short transport (0-300m), suggesting that they come from either the neighboring Lom group rocks or a local source (probably from the surrounding magmatic and metamorphic rocks). A shear zone-related origin is also proposed.
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Ulcerative colitis is a form of inflammatory bowel disease that is characterized by acute and chronic inflammation. The aim of this work was to evaluate the efficacy of hydroethanolic extract of Maesa lanceolata leaves on acetic a...
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Ulcerative colitis is a form of inflammatory bowel disease that is characterized by acute and chronic inflammation. The aim of this work was to evaluate the efficacy of hydroethanolic extract of Maesa lanceolata leaves on acetic acid-induced colitis in rats. Colitis was induced by rectal administration of 1 mL of acetic acid (4%) in 25 male rats except the normal control group which received distilled water after 18 h of fasting followed by Ketamine (50 mg/kg)/Valium (10 mg/kg) anesthesia. Five hours later, the normal control and the negative control received distilled water, the positive control received prednisolone (5 mg/kg) and the three test groups received extract at 100, 200 and 400 mg/kg bw for eight days. During treatment, rectal temperature, the number and quality of the stools, and changes in body weight were assessed. At the end of the treatment, the animals were sacrificed, blood, colon, liver and spleen were collected for evaluation of hematological, inflammatory, antioxidant and histological parameters. Rectal temperature and the number of diarrheal, mucus and bloody stools were significantly reduced (P < 0.01) during treatment in the test and positive control groups with an increase in body weight change. The extract significantly (P < 0.01) reduced myeloperoxidase, TNF-alpha, interleukin 6, NO and MDA levels and significantly (P < 0.01) increased SOD levels, of GSH and catalase activity in the colon and blood. This extract also increased (P < 0.01) levels of red blood cells, hemoglobin, hematocrit, total white blood cells and blood platelets, prevented leukocyte infiltration in the liver and colon.
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The potential energy surface (PES) for the CP(X Sigma(+))-He(S) complex has been calculated at the RCCSD(T)-F12/VTZ-F12 level of theory. The analytic fit of the PES was obtained by using global analytical method. The fitted PES wa...
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The potential energy surface (PES) for the CP(X Sigma(+))-He(S) complex has been calculated at the RCCSD(T)-F12/VTZ-F12 level of theory. The analytic fit of the PES was obtained by using global analytical method. The fitted PES was used subsequently in the close-coupling approach for the computation of the state-to-state collisional excitation cross sections of the fine-structure levels of the CP-He complex. Collision energies were taken up to 1500 cm and they yield after thermal averaging, state-to-state rate coefficients up to 200 K. The propensity rules between the lowest fine-structure levels were studied. These rules show, on one hand, a strong propensity in favour of even AN transitions, and the other hand, that cross sections and collisional rate coefficients for Delta j = Delta N transitions are larger than those for Delta j not equal Delta N transitions.
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BACKGROUND An electrocoagulation process using iron electrodes was applied for chlorophyll and tannins removal from ethanol extract of aerial parts of Anthocleista schweinfurthii Gilg. A second-order regression using Central Compo...
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BACKGROUND An electrocoagulation process using iron electrodes was applied for chlorophyll and tannins removal from ethanol extract of aerial parts of Anthocleista schweinfurthii Gilg. A second-order regression using Central Composite Design (CCD) was used to investigate the main effects of four independent variables, namely supporting electrolyte concentration (in g L-1), ethanol percentage (%), current intensity (in amps) and electrolysis time (in minutes) and their interactions. The chlorophyll removal (CR), total tannins content (TTC) and total phenols content (TPC) were analyzed using response surface methodology (RSM) and CCD. Crude and optimized extracts were characterized by UV-visible spectrometry and Fourier-transform infrared spectroscopy.
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Accurate post Hartree-Fock methods have been used to investigate electronic structure, spectroscopy, stability and metastability of low-lying electronic states of HNO, HON, NO, NO-, HNO- and HON-. Accurate vertical transition ener...
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Accurate post Hartree-Fock methods have been used to investigate electronic structure, spectroscopy, stability and metastability of low-lying electronic states of HNO, HON, NO, NO-, HNO- and HON-. Accurate vertical transition energies between lowest electronic states of HNO and HON isomers have been determined. The HNO vertical transition energy of the (X) over tilde (1)A'-(a) over tilde (3)A '' transition is shown to be 0.87 eV. Core-valence correlations and relativistic corrections have been taken into account to determine accurately spectroscopic constants of electronic states of NO- and NO. Adiabatic excitation energies and dipole moments of low-lying electronic states of NO- have also been calculated. The adiabatic electron affinity of NO has been deduced to be 0.0289 eV, which is in excellent agreement with the experimental value of 0.026 +/- 0.05 eV. The comparison of potential energy curves of low-lying states of NO/NO-, HNO/HNO- and HON/HON- reveals short-lived excited electronic states. The HON- anion appears as an unbound anion unlike to HNO- which is a bound anion. Three-dimensional potential energy surfaces (3D-PESs) for both HNO ((X) over tilde (1)A') and HNO-(X(2)A '') ground states, have been generated and fitted by second order perturbation theory to produce accurate spectroscopic constants. Spectroscopic data of HNO-(X(2)A '') deduced from this work is computed for the first time. (C) 2016 Elsevier B.V. All rights reserved.
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Colocasia esculenta L. Schott and Xanthosoma sagittifolium L. Schott are two tropical tubers species commonly referred as cocoyams. Colocasia esculenta tuber is usually used for the preparation of achu (smooth paste food), but not...
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Colocasia esculenta L. Schott and Xanthosoma sagittifolium L. Schott are two tropical tubers species commonly referred as cocoyams. Colocasia esculenta tuber is usually used for the preparation of achu (smooth paste food), but not always available. This work is aimed at evaluating the effect of mixing two cocoyam flours on the physicochemical and sensory characteristics of precooked composite flours and achu. In this respect, a factorial design was realized. This factorial design was 2 varieties of Xanthosoma sagittifolium (white-flesh and red-flesh) coded as WX and RX and 5 levels of substitutions (0, 25, 50, 75 and 100%) in the Colocasia esculenta (Ibo coco) coded as IC. Precooked flours showed significant (p < 0.05) differences in the contents of ash (2.09 +/- 0.33 to 4.21 +/- 0.03%), fiber (1.33 +/- 0.04 to 1.57 +/- 0.43%), total sugar (71.12 +/- 0.85 to 74.02 +/- 1.42%), starch (47.26 +/- 0.95 to 66.59 +/- 1.09%), proteins (3.20 +/- 0.14 to 4.35 +/- 0.07%) and total oxalate (0.41 +/- 0.16 to 0.82 +/- 0.11%). The water absorption capacity and water solubility index also shown a significant difference (p < 0.05). The highest gelatinization temperature, final viscosity, setback, and consistency during the heating time were recorded for Xanthosoma sagittifolium flours, meanwhile the peak viscosity and breakdown indexes were higher in Colocasia esculenta flour. It was also observed that there was least difference (p < 0.05) in the overall acceptability (4.54 +/- 1.96 to 5.74 +/- 1.40) of the sensory attributes of reconstituted achu by the participants. Elsewhere, the results revealed that more than 35% of the participants like very much the achu made from cocoyam flour mixtures while 44.65% of them just like it. These results indicate the potential of Xanthosoma sagittifolium precooked flours for substituting Colocasia esculenta flour at varying proportions in achu making.
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Optomechanical systems are known to exhibit self-sustained limit cycles once driven above the parametric instability point. This breaks down the linearized approximation and induces novel nonlinear effects such as dynamical multis...
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Optomechanical systems are known to exhibit self-sustained limit cycles once driven above the parametric instability point. This breaks down the linearized approximation and induces novel nonlinear effects such as dynamical multistability, staircase behavior, and the generation of optical high-order sideband combs (HOSCs). Here, we study the classical nonlinear dynamics of optomechanical systems. We combine numerical simulations and analytical investigation to predict dynamical multistability in the resolved sideband regime. A way to predict the onset of the period doubling process and to control the multistability is analytically provided by tuning the optical linewidth. Indeed, the multistability behavior first changes to a staircase shape and gradually disappears as the system approaches the unresolved sideband limit. We exploit the multistable attractors to generate optical HOSCs by acting solely on the initial values instead of increasing the driving strength. This is the figure of merit of our proposal to relate multistability to the HOSC. As a result, the properties (bandwidth, intensity) of the combs are improved as the mechanical resonator moves towards upper attractors. This work opens a way for low-power HOSCgeneration in optomechanics and the related technological applications. (C) 2020 Optical Society of America
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The Ngaoundere granite pluton, in Central-North Cameroon, located near the Central Cameroon Shear zone (CCSZ), and previously studied for its petrography and geochemistry, is characterized by the absence of macroscopic markers of ...
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The Ngaoundere granite pluton, in Central-North Cameroon, located near the Central Cameroon Shear zone (CCSZ), and previously studied for its petrography and geochemistry, is characterized by the absence of macroscopic markers of deformation. In this study, we report microstructures and magnetic fabrics (AMS) of this pluton and discuss the relationship with the Pan-African evolution of the CCSZ. The pluton consists of a porphyritic Hbl-Bt-monzogranite at its rim and a porphyritic biotite-granite at its core, a petrographic distribution denoting a normal zoning pattern, i.e. more silicic toward the centre. As expected, magnetic susceptibilities values also exhibit a zoning pattern in agreement with petrographic zonation. Thermomagnetic data indicate that this pluton is dominantly ferromagnetic in behaviour. As indicated by its microstructures, the pluton has suffered a continuum of deformation from the magmatic state to the high temperature solid-state during magma crystallization and solidification. The magnetic foliations dominantly strike NE-SW and dip moderately to steeply and the lineations mostly plunge shallowly to the NE or SW, roughly parallel to NE-to ENE-trending Central Cameroun Shear Zone (CCSZ). The foliation poles define a girdle pattern with a zone axis (52 degrees/11 degrees) rather close to the best line of the lineations (44 degrees/21 degrees). These fabrics correlate with the structures of the country rocks ascribed by several workers to a regional transpression. Toward the margins of the pluton, particularly the northern one, the lineations tend to rotate from NE to N in azimuth. This change is interpreted as due to strain partitioning, simple shearing with NE-SW extension being relayed by compression toward the northern pluton border. This new magnetic fabric study suggests that the Ngaoundere pluton (poorly dated at c. 575 Ma) was emplaced during the late stages of the CCSZ dextral transpressive movement. It also provides some more constraints on the correlation between the CCSZ system and the shear zone system of NE-Brazil. (C) 2017 Elsevier Ltd. All rights reserved.
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