The conversion of forest land to other types of land cover is one of the major issues in the global fight against climate change. Understanding the direct and indirect factors of these conversions from local studies i...The conversion of forest land to other types of land cover is one of the major issues in the global fight against climate change. Understanding the direct and indirect factors of these conversions from local studies in the tropics is essential to project the future impact of human activities on the preservation of tropical forests in general and the forests of the Republic of Congo in particular. This study, conducted in five localities with different socioeconomic contexts in the Republic of Congo, aims to analyze the variability of drivers of deforestation and forest degradation linked to urbanization in the Congo Basin. Using a series of land cover maps from the years 1986, 2003 and 2019 for the cities of Ouesso, Pokola, Ngombe, Impfondo and Dongou, as well as field data and socio-economic information collected from local and central administrations, a unique model has been developed to understand the explanatory patterns of forest loss. Deforestation around urban centers is mainly due to urban agriculture due to population growth, as well as the spatial expansion of cities, which have a major impact on the stability and integrity of forests. Shifting agriculture is the main direct cause of deforestation and forest degradation, representing 48% of the total sample, followed by the collection of wood fuel (22%), the collection of construction wood (19%), illegal logging (6%) and urban expansion (5%). Forecasts indicate that forest loss around major cities will increase by 487, 20 ha to 5266, 73 ha by 2050 compared to the base year of 2019. This study highlights the need for a new system of land management and poverty alleviation of local populations to ensure the stability of the Congo Basin tropical forests around large and small African cities.展开更多
Morphologies of deltaic strandplains are the result of multiple sedimentary dynamics interacting with climate,neotectonic and anthropic impacts.They record long-term evolution of coastal areas but also reveal past and...Morphologies of deltaic strandplains are the result of multiple sedimentary dynamics interacting with climate,neotectonic and anthropic impacts.They record long-term evolution of coastal areas but also reveal past and present hazards that can be essential to better predict risks in urbanised deltas.This paper aims to identify the effect of a long-term evolution of the prograded plain of the Tiber Delta in using current ground surface variations and geohistorical data.This study applies GIS(Geographic Information System)tools to LiDAR(Light Detection and Ranging)-derived DEM(Digital Elevation Model)data combined with stratigraphical data,aerial photography interpretation and old maps.The main outcome shows areas of subsidence are primarily located in the central part of the Tiber Delta.Lower heights at the river mouth are due to subsidence and specific lower morphologies associated with fast progradation phases,while similar low heights just north in the area of the international airport of Rome are due to subsidence alone.Subsidence under the airport is associated with the compaction of the silty clay infill of the Late Pleistocene Tiber Valley mostly deposited during the Holocene transgressive period.Only observed in the airport area,the presence of washover fans and the large extent of paleolagoons reveal the kind of risks that are increased by this subsidence.This study demonstrates that the densely urbanised central part of the Tiber Delta faces higher risks of marine submersion and coastal flooding considering ongoing relative sea level change.It also contributes to show the importance to better characterise past coastal morphologies to identify areas prone to subsidence.展开更多
Today, agricultural production is threatened by crop pathogens, including plant-parasitic nematodes. Because of their harmful effects on the environment and human health, synthetic nematicides are gradually being bann...Today, agricultural production is threatened by crop pathogens, including plant-parasitic nematodes. Because of their harmful effects on the environment and human health, synthetic nematicides are gradually being banned in several countries. This study evaluates the nematicidal activity of Datura metel oil. Datura metel seed oil was obtained using the Soxhlet extractor in hexane. The resulting oil was characterized by determining physicochemical parameters and molecular composition using GC-MS. The nematicidal activity of the oil was assessed by determining the number of dead nematodes. Physicochemical characterization gave an acidity index of 0.3% and a peroxide index of 10 meq.O2/Kg, while GC-MS analysis identified 30 molecules made up mainly of fatty acid esters, four of which represented over 74% of the oil’s total weight. The nematicidal activity of the oil, expressed in terms of mortality rate as a function of concentration, showed mortality rates of 58;69 and 79% over 48 hours of incubation at concentrations of 25, 50 and 100 µg/mL respectively. The activity observed could be linked to the high presence of the four compounds most commonly identified in the oil. These results suggest that Datura metel oil could be a promising alternative to synthetic pesticides for the control of crop pests.展开更多
From the ethyl acetate extract of the medicinal plant Graptophyllum glandulosum Turrill, five known compounds: Lupeol (1), Oleanolic acid (2), Chrysoeriol (3), N-methyl-isonicotinamide (4) and β-sitosterol 3-O-β-D-g...From the ethyl acetate extract of the medicinal plant Graptophyllum glandulosum Turrill, five known compounds: Lupeol (1), Oleanolic acid (2), Chrysoeriol (3), N-methyl-isonicotinamide (4) and β-sitosterol 3-O-β-D-glucopyranoside (5) were isolated. In addition, oxidation reactions carried out on lupeol (1) yielded two semi-synthetic compounds, including a previously unreported: (20R)-formyloxy-29-nor-lupan-3-one (1b) and one other well-known Lupenone (1a). The structures of natural and semi-synthetic compounds were determined by analysis of 1D-(1H, 13C), 2D-(COSY, HSQC and HMBC) NMR data in conjunction with mass spectrometry (TOFESIMS and HR-TOFESIMS) and by comparison with the reported data. The evaluation of antimicrobial activities of substrate (1) as well as semi-synthetic derivatives (1a and 1b) using broth microdilution method showed that compound 1b was the most active (16 ≤ MIC ≤ 32 μg/mL) against Escherichia coli, Staphylococcus aureus and Candida albicans compared to the starting material 1 (16 ≤ MIC ≤ 64 μg/mL) and derivative 1a (32 ≤ MIC ≤ 64 μg/mL).展开更多
The effect of iron concentration on the microstructural and structural properties of ZnO for electrolysis and photodetector applications was investigated.The thin layers of un-doped and doped ZnO with different percen...The effect of iron concentration on the microstructural and structural properties of ZnO for electrolysis and photodetector applications was investigated.The thin layers of un-doped and doped ZnO with different percentages of Fe(2,4,and 6 wt.%)were deposited by spin-coating on glass substrates.Sample characterization was done by X-ray diffraction(XRD),atomic force microscopy(AFM),scanning electron microscopy(SEM),energy-dispersive X-ray spectroscopy(EDS),UV−Vis absorption spectra and X-ray photoelectron spectroscopy(XPS).Structural measurements by XRD showed that all the layers were composed of polycrystallines with a hexagonal Wurtzite structure.Two new peaks were also discovered after the doping process belonging to the Fe_(2)O_(4)(400)and(440)crystal phase.Morphological analysis showed that the surface roughness values of ZnO layers ranged between 8 and 45 nm.XPS studies confirmed the presence of Fe in 3+states in ZnO layers.An average transmittance of 90%was measured by UV−Vis in the wavelength range of 200−900 nm.The values of the energy gap(Eg)decreased with an increase in the concentration of Fe.AFM topography results confirmed that ZnO-based thin layers had a relatively uniform surface.The efficiency of these samples has been confirmed for their use in many electrical applications,including photodetectors and electrolysis of contaminated solutions.展开更多
采用熔盐顶部籽晶法从K 2 Mo 3 O 10-B 2 O 3助熔剂中生长出尺寸为20 mm的优质GdAl 3(BO 3)4(简称GAB)和Nd^3+激活的自变频激光晶体。确定了GAB晶体的透光波长范围、折射率和倍频系数随波长的变化,结果表明其在整个透光范围内均可实现...采用熔盐顶部籽晶法从K 2 Mo 3 O 10-B 2 O 3助熔剂中生长出尺寸为20 mm的优质GdAl 3(BO 3)4(简称GAB)和Nd^3+激活的自变频激光晶体。确定了GAB晶体的透光波长范围、折射率和倍频系数随波长的变化,结果表明其在整个透光范围内均可实现相位匹配。测定了Nd^3+∶GAB晶体在室温下的偏振吸收、荧光光谱和荧光寿命,进行了光谱计算,测试了晶体的自变频激光性能,实现了紫外-可见光-红外-中红外多波段激光输出。展开更多
文摘The conversion of forest land to other types of land cover is one of the major issues in the global fight against climate change. Understanding the direct and indirect factors of these conversions from local studies in the tropics is essential to project the future impact of human activities on the preservation of tropical forests in general and the forests of the Republic of Congo in particular. This study, conducted in five localities with different socioeconomic contexts in the Republic of Congo, aims to analyze the variability of drivers of deforestation and forest degradation linked to urbanization in the Congo Basin. Using a series of land cover maps from the years 1986, 2003 and 2019 for the cities of Ouesso, Pokola, Ngombe, Impfondo and Dongou, as well as field data and socio-economic information collected from local and central administrations, a unique model has been developed to understand the explanatory patterns of forest loss. Deforestation around urban centers is mainly due to urban agriculture due to population growth, as well as the spatial expansion of cities, which have a major impact on the stability and integrity of forests. Shifting agriculture is the main direct cause of deforestation and forest degradation, representing 48% of the total sample, followed by the collection of wood fuel (22%), the collection of construction wood (19%), illegal logging (6%) and urban expansion (5%). Forecasts indicate that forest loss around major cities will increase by 487, 20 ha to 5266, 73 ha by 2050 compared to the base year of 2019. This study highlights the need for a new system of land management and poverty alleviation of local populations to ensure the stability of the Congo Basin tropical forests around large and small African cities.
文摘Morphologies of deltaic strandplains are the result of multiple sedimentary dynamics interacting with climate,neotectonic and anthropic impacts.They record long-term evolution of coastal areas but also reveal past and present hazards that can be essential to better predict risks in urbanised deltas.This paper aims to identify the effect of a long-term evolution of the prograded plain of the Tiber Delta in using current ground surface variations and geohistorical data.This study applies GIS(Geographic Information System)tools to LiDAR(Light Detection and Ranging)-derived DEM(Digital Elevation Model)data combined with stratigraphical data,aerial photography interpretation and old maps.The main outcome shows areas of subsidence are primarily located in the central part of the Tiber Delta.Lower heights at the river mouth are due to subsidence and specific lower morphologies associated with fast progradation phases,while similar low heights just north in the area of the international airport of Rome are due to subsidence alone.Subsidence under the airport is associated with the compaction of the silty clay infill of the Late Pleistocene Tiber Valley mostly deposited during the Holocene transgressive period.Only observed in the airport area,the presence of washover fans and the large extent of paleolagoons reveal the kind of risks that are increased by this subsidence.This study demonstrates that the densely urbanised central part of the Tiber Delta faces higher risks of marine submersion and coastal flooding considering ongoing relative sea level change.It also contributes to show the importance to better characterise past coastal morphologies to identify areas prone to subsidence.
文摘Today, agricultural production is threatened by crop pathogens, including plant-parasitic nematodes. Because of their harmful effects on the environment and human health, synthetic nematicides are gradually being banned in several countries. This study evaluates the nematicidal activity of Datura metel oil. Datura metel seed oil was obtained using the Soxhlet extractor in hexane. The resulting oil was characterized by determining physicochemical parameters and molecular composition using GC-MS. The nematicidal activity of the oil was assessed by determining the number of dead nematodes. Physicochemical characterization gave an acidity index of 0.3% and a peroxide index of 10 meq.O2/Kg, while GC-MS analysis identified 30 molecules made up mainly of fatty acid esters, four of which represented over 74% of the oil’s total weight. The nematicidal activity of the oil, expressed in terms of mortality rate as a function of concentration, showed mortality rates of 58;69 and 79% over 48 hours of incubation at concentrations of 25, 50 and 100 µg/mL respectively. The activity observed could be linked to the high presence of the four compounds most commonly identified in the oil. These results suggest that Datura metel oil could be a promising alternative to synthetic pesticides for the control of crop pests.
文摘From the ethyl acetate extract of the medicinal plant Graptophyllum glandulosum Turrill, five known compounds: Lupeol (1), Oleanolic acid (2), Chrysoeriol (3), N-methyl-isonicotinamide (4) and β-sitosterol 3-O-β-D-glucopyranoside (5) were isolated. In addition, oxidation reactions carried out on lupeol (1) yielded two semi-synthetic compounds, including a previously unreported: (20R)-formyloxy-29-nor-lupan-3-one (1b) and one other well-known Lupenone (1a). The structures of natural and semi-synthetic compounds were determined by analysis of 1D-(1H, 13C), 2D-(COSY, HSQC and HMBC) NMR data in conjunction with mass spectrometry (TOFESIMS and HR-TOFESIMS) and by comparison with the reported data. The evaluation of antimicrobial activities of substrate (1) as well as semi-synthetic derivatives (1a and 1b) using broth microdilution method showed that compound 1b was the most active (16 ≤ MIC ≤ 32 μg/mL) against Escherichia coli, Staphylococcus aureus and Candida albicans compared to the starting material 1 (16 ≤ MIC ≤ 64 μg/mL) and derivative 1a (32 ≤ MIC ≤ 64 μg/mL).
基金the support received from the Researchers Supporting Project(No.RSP2024R404),King Saud University,Riyadh,Saudi Arabia。
文摘The effect of iron concentration on the microstructural and structural properties of ZnO for electrolysis and photodetector applications was investigated.The thin layers of un-doped and doped ZnO with different percentages of Fe(2,4,and 6 wt.%)were deposited by spin-coating on glass substrates.Sample characterization was done by X-ray diffraction(XRD),atomic force microscopy(AFM),scanning electron microscopy(SEM),energy-dispersive X-ray spectroscopy(EDS),UV−Vis absorption spectra and X-ray photoelectron spectroscopy(XPS).Structural measurements by XRD showed that all the layers were composed of polycrystallines with a hexagonal Wurtzite structure.Two new peaks were also discovered after the doping process belonging to the Fe_(2)O_(4)(400)and(440)crystal phase.Morphological analysis showed that the surface roughness values of ZnO layers ranged between 8 and 45 nm.XPS studies confirmed the presence of Fe in 3+states in ZnO layers.An average transmittance of 90%was measured by UV−Vis in the wavelength range of 200−900 nm.The values of the energy gap(Eg)decreased with an increase in the concentration of Fe.AFM topography results confirmed that ZnO-based thin layers had a relatively uniform surface.The efficiency of these samples has been confirmed for their use in many electrical applications,including photodetectors and electrolysis of contaminated solutions.
文摘采用熔盐顶部籽晶法从K 2 Mo 3 O 10-B 2 O 3助熔剂中生长出尺寸为20 mm的优质GdAl 3(BO 3)4(简称GAB)和Nd^3+激活的自变频激光晶体。确定了GAB晶体的透光波长范围、折射率和倍频系数随波长的变化,结果表明其在整个透光范围内均可实现相位匹配。测定了Nd^3+∶GAB晶体在室温下的偏振吸收、荧光光谱和荧光寿命,进行了光谱计算,测试了晶体的自变频激光性能,实现了紫外-可见光-红外-中红外多波段激光输出。
