Research for bioactive molecules and not resistant to infectious agents remains topical for science. The total polyphenols (TPP) and total flavonoids (TFv) of the hydroethanolic extracts and fractions obtained were qu...Research for bioactive molecules and not resistant to infectious agents remains topical for science. The total polyphenols (TPP) and total flavonoids (TFv) of the hydroethanolic extracts and fractions obtained were quantified according to the spectrophotometric method described in the literature using the Folin-Ciocalteu reagent and the colorless solutions of sodium nitrite 2.5% and aluminum chloride 10% respectively. The characterization of chemical compounds was made by coupling liquid chromatography (LC) and mass spectroscopy (MS). Thus, 15 chemical compounds were characterized, seven from Gnetum africanum (EBa) and eight from Gnetum buchholzianum (EBb). The majority of which were stilbens, such as Gnetupendin D, Dimethoxygnetulin, Methoxyparvifolol D, Isorhaponcitin from Eba and Gnetuhaidin P, Gnetupendin D, Gnetuhainin C, phenols (Alcohol Homovanillyl, Alcohol Erythro guaiacylglycerol-β-O-4'-coniferyl, and Alcohol Homovanillyl from EBb. The minority were flavonoids such as Dimethoxydihydropyraneriodictyol, Dimethoxyeriodictyol (EBa) and Dimethoxydihydropyraneriodictyol, Trimethoxyluteolin (EBb). The levels of total polyphenolics and total flavonoids content were respectively 14.520 ± 0.557 mg EAA/g Extract and 29.870 ± 2.485 mg EQ/g Extract for EBa. The levels of total polyphenolics and total flavonoids content for EBb were respectively 4.560 ± 0.010 mg EAA/g Extract and 2.233 ± 0.251 mg EQ/g Extract. The high levels of flavonoids content respectively 220.200 ± 35.500 and 335.300 ± 57.810 mg EQ/g Extract were shown in Dichlorometan fraction from EBa and EBb. These bioactive compounds identified and total phenolics compounds quantified can be exploited in pharmacological and pharmacokinetical activities to fight against multi-resistant infectious agents and as well as oxidative stress and antiinflammatory diseases.展开更多
The clay soils of the city of Douala are constantly saturated with water, which permanently favors the hydrodynamic behavior of the soils (swelling or consolidation). This phenomenon can cause serious disturbances in ...The clay soils of the city of Douala are constantly saturated with water, which permanently favors the hydrodynamic behavior of the soils (swelling or consolidation). This phenomenon can cause serious disturbances in the structure of buildings resulting in the appearance of cracks in structures (buildings, road bridge, viaduct, etc.). The foundation raft is a very important structure in the dimensioning of structures. Given the soil-structure interactions, its mechanical characteristics must be the subject of a special study linked to the building environment. In this article, we present a study of the mechanical behavior of a foundation raft anchored in a laminate floor. The aim is to highlight the influence of the mechanical properties of the foundation soil on the evolution of the mechanical behavior of the raft. The method used is a numerical simulation. A physical model taking into account a 5-storey building based in Douala in the Denver district is studied. The foundation on the raft foundation of this building follows an elastic constitutive law with Mazars damage, and rests on a laminated soil of plastic elastic model with Camclay plasticity criterion. The ground-raft and ground-ground interfaces are carried out with the finite elements joined to three nodes (JOI3), and obey the Coulomb model;it is an expansion joint model with Mohr-Coulomb type criterion and associated flow. The numerical resolution is carried out by the finite element method, and the numerical simulations via the Cast3M calculation code. The results from the simulations show that the mechanical characteristics of foundation soils, in this case the water content, the compactness, the state of consolidation, greatly influence the mechanical behavior of the foundation slab. There is indeed a significant settlement and a great deformation of the raft foundation when the water content of the soil layers increases, and when the states of consolidation and compactness are low. This article allows us to predict and control the evolution of the behavior of the ground-structure interface of a raft foundation and to adopt a new model appropriate for the sizing of civil engineering structures.展开更多
In order to recommend the use of the masonry of chipboards with eviscerated bed joints and hollow vertical joints, we did a comparative study using simulation of the behavior of walls with traditional blocs and those ...In order to recommend the use of the masonry of chipboards with eviscerated bed joints and hollow vertical joints, we did a comparative study using simulation of the behavior of walls with traditional blocs and those of the new model of blocs. Thus, using Solidworks, we built up walls of 2.40 m length and 1.30m height following strictly the real constraints of elevation. Using finite elements method, the meshing, loading and the observation of the behavior are done through CosmosWorks. We can define a study used by Solidworks and Cosmos Works interface, and introduce parameters of walls;the meshing is then done (here we have volumic elements with three noses);then the big rigidity matrix is defined;the equations are also defined and solved and results are presented in numerical and graphical form. Since that form of results is not easy to analyse, we passed them to MATLAB in order to have usual curves more easily to analyse. The difficulty here is based on the conception of geometry of piece which must have same constraints and dimensions corresponding exactly to the real model. The other difficulty is to define parameters to use for a heterogeneous material like masonry. Once those difficulties are solved, the logical follows fully the steps of finite elements method until the solution in terms of noses repartition constraints, displacements and deformations. Then, we simulated the behavior on vertical static load, vertical static load and horizontal applied load and composed loads (vertical and horizontal) which are real conditions generally known in masonry walls. It has been shown that the new kind of masonry has a better behavior than the traditional one when loaded in its plan;in contrary, the behavior is less when loaded in the perpendicular plan.展开更多
A survey was conducted in the Sudano-Sahelian, High Savannah, and Western Highlands agroecological zones of Cameroon to assess the morphometric features and to determine the population structure of the native common g...A survey was conducted in the Sudano-Sahelian, High Savannah, and Western Highlands agroecological zones of Cameroon to assess the morphometric features and to determine the population structure of the native common guinea fowl breed. A total of 1021 adult common guinea fowls were sampled in the dominant pastoral production system. The main results showed that there was a phenotypic variability (p < 0.01) of the morphometric characteristics of common guinea fowls with a dominance of pearl gray coloring of the plumage (23.02%), bluish red barbels (29.09%), black eyes (36.04%) and tarsi (39.18%). The development of the barbels and the shape of the comb are determinants of the sex (p < 0.01), as well as the live weight which presents a dimorphism in favor of the females (p < 0.01). The average measurements (in cm) were: Crest height (2.07 ± 0.03), Crest length (2.79 ± 0.03), Barbel length (3.35 ± 0.04), Barbel height (2.28 ± 0.02), Spout length (2.11 ± 0.01), Caruncle length (0.69 ± 0.01), Baleen length (4.32 ± 0.04), Chest circumference (31.81 ± 0.99), Wing length (25.99 ± 0.18), wingspan (41.82 ± 0.32), Thigh diameter (9.17 ± 0.10), Thigh length (11.30 ± 0.07), Tarsus length (6.62 ± 0.04), Tarsus diameter (1.20 ± 0.07), Body length (40.13 ± 0.15), and Live weight (1.68 ± 0.02 kg). The highest positive correlation (r < 0.70) was observed between thigh and ridge length. The PCR revealed that three (3) components (F1, F2 and F3) make it possible to better explain phenotypic variability (50.21%). The variables that contributed most to the explanation of the observed total variability are the length of the crest (0.70%), the beak (0.61%), the wattle (0.70%), the body (0.44%), the wing (0.35%), thigh (0.68%), tarsus (0.29%) and wing span (0.41%) for the main component F1 while the F2 and F3 components mainly concern the length of the barbel (0.43%) and the height of the crest (0.48%) respectively. The F1 factor constitutes the most discriminating variable (89.40%). The AFD and the CAH made it possible to detect 03 sub-populations (T1, T2, and T3) which can be grouped into 2 subgroups on the basis of intra/inter population variations and genetic distances. Morphometric assessment coupled with genomics would increase the efficiency of selection, improvement, and conservation of common guinea fowl in Cameroun.展开更多
The objective of this article is to make a contribution relating to the modeling, control, simulation and stabilization of a complex system, with six degrees of freedom of a particular drone which presents many advant...The objective of this article is to make a contribution relating to the modeling, control, simulation and stabilization of a complex system, with six degrees of freedom of a particular drone which presents many advantages and challenges. On the technological, military, political and other levels with an enormous and beneficial social contribution</span><span style="font-family:Verdana;">, </span><span style="font-family:Verdana;">it is a quadrotor which is a nonlinear, strongly coupled and unstable system. Such a structure is difficult to master</span><span style="font-family:Verdana;">, </span><span style="font-family:Verdana;">because the control is multivariable in the sense that six degrees of freedom are to be controlled simultaneously and operating in an environment subject to disturbances. Two commands, in particular Backstepping and </span><span style="font-family:Verdana;"></span><span style="font-family:Verdana;">PID, will be applied to obtain the stabilization of the quadcopter at the desired values, in attitude and in altitude. This article presents the comparative results of the performance of the quadcopter under the two controls. The effect of the parameters of each command on the response time of the system is elucidated under the Matlab/Simulink environment. For a simulation time of up to 10 seconds minimum with a less good response time of almost 2 seconds for the PID control</span><span style="font-family:Verdana;">, </span><span style="font-family:Verdana;">these results prove the robustness of the Backstepping command.展开更多
The objective of this work was to draw up an inventory of environmental and anthropogenic factors linked to indigenous breeding practices of guinea fowl (Numida meleagris) influenced by plumage characteristics. The in...The objective of this work was to draw up an inventory of environmental and anthropogenic factors linked to indigenous breeding practices of guinea fowl (Numida meleagris) influenced by plumage characteristics. The information was collected using the snowball technique and using a formal questionnaire developed (AU-IBAR, 2015). The dominant plumage is pearl gray with a frequency of 38.89% followed by black (13.85%). In total, 154 adult animals were lost by operators with a frequency of 22.95%. According to plumage, white comes first with a frequency of 51.61% followed by Lavender plumage (36.58%). Predation is the major constraint with a frequency of 35.72%. The guinea fowl most targeted by predators are the white guinea fowl with a frequency of 56.25%, while predation is low for black plumage (25%), royal purple (33.34) and pearl gray (34.69). The pearl gray guinea fowl and the royal purple guinea fowl appear to have a more developed wild instinct, which explains the frequency of recorded escapes. White plumage is perceived as being more docile during breeding and tends to exhibit better resistance to heat stress compared to other phenotypes, making it more valued for traditional rituals. Dark plumage seems more sought after in breeding for its supposed prolificacy, its resistance to infections and its weight. According to breeders, the dominance relationship mainly depends on the number of individuals of the same plumage. Dark plumage in significant numbers in most flocks seems to have dominance in terms of food and choice of sexual partners, which would explain their large numbers.展开更多
This study was conducted to assess the toxic effect of hydroethanolic extract combinations of Gnetum africanum Welv. leaves and Gnetum buchholzianum Engl. (Gnetaceae) in experimental rats to test the validity of the t...This study was conducted to assess the toxic effect of hydroethanolic extract combinations of Gnetum africanum Welv. leaves and Gnetum buchholzianum Engl. (Gnetaceae) in experimental rats to test the validity of the treatment of liver disorders related to oxidative stress. The Combinations (m/m) 50-50 for E2 and 75-25 for E3 of ethanol-water extracts from plant leaves at the respective doses of 100, 200, and 400 mg/kg of body weight were used for 32-day toxicity. They were obtained after harvesting leaves, sorting, drying in the air cover for three weeks, and grinding. The resulting powder was doubly macerated with 70% ethanol for 48 hours and filtered. The filtrate was concentrated with the Heidolph-brand rotary rotavapor and each extract obtained was preserved. The administrations were carried out by gavage to wistar, male and non-pregnant female albino rats. In the end, the animals were sacrificed. The serum and organ homogenates were obtained for biochemical, tissue, and histopathological analyses respectively. The analyses revealed insignificant variations at the 5% probability threshold of the weight growth of experimental animals. These variations were found to be statistically significant at the same probability for biochemical and tissue parameters based on the dose of plant extracts and compared to control animals. Histopathological analysis of liver tissue showed leukodate infiltration that indicates extract-induced inflammation of the hepatocytes at the 400 mg/kg dose of body weight in females. However, this infiltration of the cells would have improved the regeneration of hepatocytes justified by the normal rate of transaminases. These results showed that combinations of hydroethanolic extracts of G. africanum and G. buchholzianumare non-toxicand may be potential candidates in the Cameroonian flora medicinal plant database shown in the monitoring of oxidative stress-related diseases.展开更多
文摘Research for bioactive molecules and not resistant to infectious agents remains topical for science. The total polyphenols (TPP) and total flavonoids (TFv) of the hydroethanolic extracts and fractions obtained were quantified according to the spectrophotometric method described in the literature using the Folin-Ciocalteu reagent and the colorless solutions of sodium nitrite 2.5% and aluminum chloride 10% respectively. The characterization of chemical compounds was made by coupling liquid chromatography (LC) and mass spectroscopy (MS). Thus, 15 chemical compounds were characterized, seven from Gnetum africanum (EBa) and eight from Gnetum buchholzianum (EBb). The majority of which were stilbens, such as Gnetupendin D, Dimethoxygnetulin, Methoxyparvifolol D, Isorhaponcitin from Eba and Gnetuhaidin P, Gnetupendin D, Gnetuhainin C, phenols (Alcohol Homovanillyl, Alcohol Erythro guaiacylglycerol-β-O-4'-coniferyl, and Alcohol Homovanillyl from EBb. The minority were flavonoids such as Dimethoxydihydropyraneriodictyol, Dimethoxyeriodictyol (EBa) and Dimethoxydihydropyraneriodictyol, Trimethoxyluteolin (EBb). The levels of total polyphenolics and total flavonoids content were respectively 14.520 ± 0.557 mg EAA/g Extract and 29.870 ± 2.485 mg EQ/g Extract for EBa. The levels of total polyphenolics and total flavonoids content for EBb were respectively 4.560 ± 0.010 mg EAA/g Extract and 2.233 ± 0.251 mg EQ/g Extract. The high levels of flavonoids content respectively 220.200 ± 35.500 and 335.300 ± 57.810 mg EQ/g Extract were shown in Dichlorometan fraction from EBa and EBb. These bioactive compounds identified and total phenolics compounds quantified can be exploited in pharmacological and pharmacokinetical activities to fight against multi-resistant infectious agents and as well as oxidative stress and antiinflammatory diseases.
文摘The clay soils of the city of Douala are constantly saturated with water, which permanently favors the hydrodynamic behavior of the soils (swelling or consolidation). This phenomenon can cause serious disturbances in the structure of buildings resulting in the appearance of cracks in structures (buildings, road bridge, viaduct, etc.). The foundation raft is a very important structure in the dimensioning of structures. Given the soil-structure interactions, its mechanical characteristics must be the subject of a special study linked to the building environment. In this article, we present a study of the mechanical behavior of a foundation raft anchored in a laminate floor. The aim is to highlight the influence of the mechanical properties of the foundation soil on the evolution of the mechanical behavior of the raft. The method used is a numerical simulation. A physical model taking into account a 5-storey building based in Douala in the Denver district is studied. The foundation on the raft foundation of this building follows an elastic constitutive law with Mazars damage, and rests on a laminated soil of plastic elastic model with Camclay plasticity criterion. The ground-raft and ground-ground interfaces are carried out with the finite elements joined to three nodes (JOI3), and obey the Coulomb model;it is an expansion joint model with Mohr-Coulomb type criterion and associated flow. The numerical resolution is carried out by the finite element method, and the numerical simulations via the Cast3M calculation code. The results from the simulations show that the mechanical characteristics of foundation soils, in this case the water content, the compactness, the state of consolidation, greatly influence the mechanical behavior of the foundation slab. There is indeed a significant settlement and a great deformation of the raft foundation when the water content of the soil layers increases, and when the states of consolidation and compactness are low. This article allows us to predict and control the evolution of the behavior of the ground-structure interface of a raft foundation and to adopt a new model appropriate for the sizing of civil engineering structures.
文摘In order to recommend the use of the masonry of chipboards with eviscerated bed joints and hollow vertical joints, we did a comparative study using simulation of the behavior of walls with traditional blocs and those of the new model of blocs. Thus, using Solidworks, we built up walls of 2.40 m length and 1.30m height following strictly the real constraints of elevation. Using finite elements method, the meshing, loading and the observation of the behavior are done through CosmosWorks. We can define a study used by Solidworks and Cosmos Works interface, and introduce parameters of walls;the meshing is then done (here we have volumic elements with three noses);then the big rigidity matrix is defined;the equations are also defined and solved and results are presented in numerical and graphical form. Since that form of results is not easy to analyse, we passed them to MATLAB in order to have usual curves more easily to analyse. The difficulty here is based on the conception of geometry of piece which must have same constraints and dimensions corresponding exactly to the real model. The other difficulty is to define parameters to use for a heterogeneous material like masonry. Once those difficulties are solved, the logical follows fully the steps of finite elements method until the solution in terms of noses repartition constraints, displacements and deformations. Then, we simulated the behavior on vertical static load, vertical static load and horizontal applied load and composed loads (vertical and horizontal) which are real conditions generally known in masonry walls. It has been shown that the new kind of masonry has a better behavior than the traditional one when loaded in its plan;in contrary, the behavior is less when loaded in the perpendicular plan.
文摘A survey was conducted in the Sudano-Sahelian, High Savannah, and Western Highlands agroecological zones of Cameroon to assess the morphometric features and to determine the population structure of the native common guinea fowl breed. A total of 1021 adult common guinea fowls were sampled in the dominant pastoral production system. The main results showed that there was a phenotypic variability (p < 0.01) of the morphometric characteristics of common guinea fowls with a dominance of pearl gray coloring of the plumage (23.02%), bluish red barbels (29.09%), black eyes (36.04%) and tarsi (39.18%). The development of the barbels and the shape of the comb are determinants of the sex (p < 0.01), as well as the live weight which presents a dimorphism in favor of the females (p < 0.01). The average measurements (in cm) were: Crest height (2.07 ± 0.03), Crest length (2.79 ± 0.03), Barbel length (3.35 ± 0.04), Barbel height (2.28 ± 0.02), Spout length (2.11 ± 0.01), Caruncle length (0.69 ± 0.01), Baleen length (4.32 ± 0.04), Chest circumference (31.81 ± 0.99), Wing length (25.99 ± 0.18), wingspan (41.82 ± 0.32), Thigh diameter (9.17 ± 0.10), Thigh length (11.30 ± 0.07), Tarsus length (6.62 ± 0.04), Tarsus diameter (1.20 ± 0.07), Body length (40.13 ± 0.15), and Live weight (1.68 ± 0.02 kg). The highest positive correlation (r < 0.70) was observed between thigh and ridge length. The PCR revealed that three (3) components (F1, F2 and F3) make it possible to better explain phenotypic variability (50.21%). The variables that contributed most to the explanation of the observed total variability are the length of the crest (0.70%), the beak (0.61%), the wattle (0.70%), the body (0.44%), the wing (0.35%), thigh (0.68%), tarsus (0.29%) and wing span (0.41%) for the main component F1 while the F2 and F3 components mainly concern the length of the barbel (0.43%) and the height of the crest (0.48%) respectively. The F1 factor constitutes the most discriminating variable (89.40%). The AFD and the CAH made it possible to detect 03 sub-populations (T1, T2, and T3) which can be grouped into 2 subgroups on the basis of intra/inter population variations and genetic distances. Morphometric assessment coupled with genomics would increase the efficiency of selection, improvement, and conservation of common guinea fowl in Cameroun.
文摘The objective of this article is to make a contribution relating to the modeling, control, simulation and stabilization of a complex system, with six degrees of freedom of a particular drone which presents many advantages and challenges. On the technological, military, political and other levels with an enormous and beneficial social contribution</span><span style="font-family:Verdana;">, </span><span style="font-family:Verdana;">it is a quadrotor which is a nonlinear, strongly coupled and unstable system. Such a structure is difficult to master</span><span style="font-family:Verdana;">, </span><span style="font-family:Verdana;">because the control is multivariable in the sense that six degrees of freedom are to be controlled simultaneously and operating in an environment subject to disturbances. Two commands, in particular Backstepping and </span><span style="font-family:Verdana;"></span><span style="font-family:Verdana;">PID, will be applied to obtain the stabilization of the quadcopter at the desired values, in attitude and in altitude. This article presents the comparative results of the performance of the quadcopter under the two controls. The effect of the parameters of each command on the response time of the system is elucidated under the Matlab/Simulink environment. For a simulation time of up to 10 seconds minimum with a less good response time of almost 2 seconds for the PID control</span><span style="font-family:Verdana;">, </span><span style="font-family:Verdana;">these results prove the robustness of the Backstepping command.
文摘The objective of this work was to draw up an inventory of environmental and anthropogenic factors linked to indigenous breeding practices of guinea fowl (Numida meleagris) influenced by plumage characteristics. The information was collected using the snowball technique and using a formal questionnaire developed (AU-IBAR, 2015). The dominant plumage is pearl gray with a frequency of 38.89% followed by black (13.85%). In total, 154 adult animals were lost by operators with a frequency of 22.95%. According to plumage, white comes first with a frequency of 51.61% followed by Lavender plumage (36.58%). Predation is the major constraint with a frequency of 35.72%. The guinea fowl most targeted by predators are the white guinea fowl with a frequency of 56.25%, while predation is low for black plumage (25%), royal purple (33.34) and pearl gray (34.69). The pearl gray guinea fowl and the royal purple guinea fowl appear to have a more developed wild instinct, which explains the frequency of recorded escapes. White plumage is perceived as being more docile during breeding and tends to exhibit better resistance to heat stress compared to other phenotypes, making it more valued for traditional rituals. Dark plumage seems more sought after in breeding for its supposed prolificacy, its resistance to infections and its weight. According to breeders, the dominance relationship mainly depends on the number of individuals of the same plumage. Dark plumage in significant numbers in most flocks seems to have dominance in terms of food and choice of sexual partners, which would explain their large numbers.
文摘This study was conducted to assess the toxic effect of hydroethanolic extract combinations of Gnetum africanum Welv. leaves and Gnetum buchholzianum Engl. (Gnetaceae) in experimental rats to test the validity of the treatment of liver disorders related to oxidative stress. The Combinations (m/m) 50-50 for E2 and 75-25 for E3 of ethanol-water extracts from plant leaves at the respective doses of 100, 200, and 400 mg/kg of body weight were used for 32-day toxicity. They were obtained after harvesting leaves, sorting, drying in the air cover for three weeks, and grinding. The resulting powder was doubly macerated with 70% ethanol for 48 hours and filtered. The filtrate was concentrated with the Heidolph-brand rotary rotavapor and each extract obtained was preserved. The administrations were carried out by gavage to wistar, male and non-pregnant female albino rats. In the end, the animals were sacrificed. The serum and organ homogenates were obtained for biochemical, tissue, and histopathological analyses respectively. The analyses revealed insignificant variations at the 5% probability threshold of the weight growth of experimental animals. These variations were found to be statistically significant at the same probability for biochemical and tissue parameters based on the dose of plant extracts and compared to control animals. Histopathological analysis of liver tissue showed leukodate infiltration that indicates extract-induced inflammation of the hepatocytes at the 400 mg/kg dose of body weight in females. However, this infiltration of the cells would have improved the regeneration of hepatocytes justified by the normal rate of transaminases. These results showed that combinations of hydroethanolic extracts of G. africanum and G. buchholzianumare non-toxicand may be potential candidates in the Cameroonian flora medicinal plant database shown in the monitoring of oxidative stress-related diseases.
