Dynamique spatio-temporelle du couvert forestier dans le bassin de la rivière Kara au Nord Togo (Afrique de l’Ouest)

Cette étude examine l'évolution de l'occupation des sols dans le bassin de la Kara sur 50 ans, de 1972 à 2021, en utilisant des images Landsat. Ce bassin, affecté par l'augmentation de la population, subit des changements notables au niveau de son couvert forestier. L'objectif est d'évaluer la dynamique à travers l'analyse de données de télédétection. Les étapes incluent la cartographie de l'occupation du sol pour les années 1972, 1987, 2005 et 2021, ainsi qu'une prédiction pour 2050 basée sur un scénario tendanciel. Le VHI a été calculé pour suivre la santé de la végétation et sa corrélation avec les paramètres météorologiques. Les résultats montrent une diminution significative des forêts de 1972 à 2005, suivie d'une légère augmentation jusqu'en 2021, indiquant une tendance positive vers la conservation. Cependant, la conversion des savanes en terres agricoles est préoccupante, avec une dégradation rapide de 9,22 % entre 2005 et 2021. L'analyse de la matrice de Markov a permis d'évaluer les probabilités de transition entre les classes d'occupation du sol pour la période 2021-2050, révélant une tendance à une conversion des savanes en forêts. L'analyse de l'indice VHI montre une variabilité interannuelle de la santé de la végétation, avec des conditions humides et sèches alternant entre 1972 et 2005, et une variabilité réduite entre 2005 et 2021. Ces résultats fournissent des bases pour comprendre et anticiper l'évolution des paysages face aux migrations des populations et au développement agricole.   This study examines land use changes in the Kara basin over a 50-year period, from 1972 to 2021, using Landsat imagery. This basin, impacted by population growth, is experiencing notable changes in its forest cover. The aim is to assess this dynamic through remote sensing data analysis. The steps include mapping land use for the years 1972, 1987, 2005, and 2021, as well as making a prediction for 2050 based on a trend scenario. The Vegetation Health Index (VHI) was calculated to track vegetation health and its correlation with meteorological parameters. The results show a significant decrease in forests from 1972 to 2005, followed by a slight increase until 2021, indicating a positive trend towards conservation. However, the conversion of savannas to agricultural land is concerning, with a rapid degradation of 9.22% between 2005 and 2021. The Markov matrix analysis assessed the probabilities of transition between land use classes for the period 2021-2050, revealing a trend towards the conversion of savannas into forests. The VHI analysis indicates interannual variability in vegetation health, with alternating wet and dry conditions between 1972 and 2005, and reduced variability between 2005 and 2021. These results provide a foundation for understanding and anticipating the evolution of landscapes in response to population migrations and agricultural development

Strengthening forest landscape restoration through understanding land use dynamics: case study of Tchamba Prefecture (Togo)

Land use and land cover (LULC) change remains a major concern in many countries. To examine how land is used for increased actions on forest landscape restoration (FLR) issues, this study analyses LULC changes from 1991 to 2022 and predict future patterns for the years 2050 in Tchamba Prefecture, Togo, using remote sensing and the Cellular Automata-Markov modelling technique. Results show that dense forests and gallery forests (18.85%), open forest/woodland (20.17%), and tree and shrub savannah (50.04%) were the predominant classes of the landscape in 1991. However, by 2022, most tree and shrub savannah had been converted to mosaic crop/fallow land (52.27%), open forest/woodland (19.32%), and plantation (7.09%). Thus, between 1991 and 2022, forest area decreased from 89.87% to 48.96%; a 45.52% reduction in coverage. Predictions are that open forest/woodland, tree and shrub savannah will decline, while mosaic crop/fallow land will increase (51.66%). However, slight increases were recorded in plantation (9.43%) and a slight balance in dense forests/gallery forests (16.17%). Consequently, forest area will slightly change between 2022 (48.96%) and 2050 (47.41%). These changes in LULC are associated to socio-economic pressures and political instability in the 1990s. So, the return to stability, the promotion of community forests as a key restoration model, and the valorisation of agroforestry species allows for the stabilisation of dense forests/gallery forests areas and an increase in plantation. Thus, it is therefore for all stakeholders involved in restoration processes to consider this information when planning FLR activities

Effets d’un acide fort sur la réaction de la DPPH avec deux huiles essentielles de deux plantes aromatiques acclimatées au Togo

Des études ont montré que les extraits de certaines plantes médicinales ainsi que leurs huiles essentielles (HE) sont sources de substances bioactives avec de potentiels antioxydants remarquables. L’objectif de ce travail est l’étude de l’influence du milieu réactionnel sur l’action des HE des plantes, de O. basilicum et O. gratissimum acclimatées au Togo, sur la 2,2-diphényl-1-picrylhydrazyle. Les constituants chimiques des HE sont identifiés par la chromatographie en phase gazeuse. Le test de réduction de la 2,2-diphényl-1-picrylhydrazyle (DPPH) et celui de réduction de l’ion ferreux Fe2+ (FRAP) sont utilisés pour déterminer la capacité antioxydante. Les propriétés antioxydantes des HE ont été mises en évidence par la recherche de l’intensité colorante (IC50) et la détermination de l’équivalent en Fe2+ des solutions testées. L’introduction d’un acide fort (acide chlorhydrique) influence les paramètres cinétiques. Les huiles essentielles étudiées contiennent le thymol et l'eugénol et sont anti oxydants. Toutefois, en se référant à la classification de Sanchez-Moreno, ces huiles essentielles ont un pouvoir anti-radicalaire faible. Dans l’intervalle de concentrations étudié [0,025-0,1] M, la réaction est accélérée les cinq premières minutes avec un taux de conversion, comme la vitesse de réaction très élevés. Le mécanisme (electron transfer – proton transfer) est prédominant. L’augmentation de la concentration en HCl et le temps ont favorisé le mécanisme SPLET. Cette étude a montré que les huiles essentielles étudiées ont un pouvoir anti-radicalaire faible mais, elles ont des vitesses de réaction intermédiaires avec la DPPH.© 2015 International Formulae Group. All rights reserved.Mots clés: O. basilicum et O. gratissimum, DPPH, antioxydant, facteurs cinétiques, huiles essentiellesEnglish Title: Effects of a strong acid on the reaction of DPPH with two essential oils from two aromatic plants acclimatized in TogoEnglish AbstractStudies have shown that extracts of certain medicinal plants as their HE are sources of bioactive substances with potential remarkable antioxidants. The objective of this work is to study the influence of the reaction medium on the essential oils, O basilicum and O gratissimum, from Togo, their action on 2,2-dipheny-1-picrylhydrazyl. The chemical constituents of essential oils are identified using gas chromatography. The reduction tests with DPPH and reduction of Fe2+ ion (FRAP) are used to determine the antioxidant capacity. Antioxidant properties of the essential oils are shown up by the detection of colored intensity (IC50) and by the determination of Fe2+ ion equivalent in the solutions. The addition of a strong acid (HCl) influences the kinetic parameters. The studied essential oils contain thymol and eugenol and are antioxidants. Although, based on the Sanchez-Moreno classification, these essential oils have weak antiradical activity. Within the studied concentration range from 0.025M to 0.1M, the reaction runs fast in the first five minutes as well as a high reaction speed. The mechanism (electron-proton transfer) is predominant. Increasing time and HCl concentration favored SPLET mechanism. This study showed that essential oils studied have low anti-radical power, but they have intermediate reaction rates with DPPH.© 2015 International Formulae Group. All rights reserved.Keywords: O. basilicum, O. gratissimum, DPPH, antioxidant, kinetic factors, essential oil

Que sont devenues les plantes autrefois consommées par les divers groupes ethnoculturels du Togo?

L'alimentation végétale chez l'homme a subi beaucoup de mutations dues essentiellement à l'adoption de régimes alimentaires dits évolués dans lesquels les ressources végétales locales rustiques occupent de moins en moins de place. Une étude ethnobotanique sur les plantes alimentaires mineures ou menacées de disparition a été menée entre 2003 et 2006 dans 280 localités distribuées sur toute l'étendue du territoire togolais en tenant compte des 5 zones écologiques et des différents groupes ethnoculturels. Cent trente deux espèces alimentaires mineures ou menacées de disparition ont été recensées. Elles sont classées en 85 espèces spontanées (64 %) et 47 espèces cultivées (36 %). Quarante-quatre espèces de plantes ont été signalées comme menacées de disparition au niveau de tous les groupes ethnoculturels du pays. Tandis que la menace de disparition ne pèse sur d'autres qu'au niveau régional, voire local. Suivant la réduction de la zone d'occurrence et / ou de leurs implications l'alimentation des populations, 6 plantes sont considérées comme très menacées, 19 comme assez menacées, 86 comme menacées et 129 comme peu menacées. Le nombre de plantes alimentaires menacées de disparition a varié de 2 à 40, suivant les localités et de 10 à 50 chez la plupart des ethnies.Nowadays, traditional plants are less used for food by human because of more sophisticated eating habits. An ethno botanical study was carried out on both minor and food plants threatened for extinction in 280 localities in Togo throughout the 5 ecological zones and socio-ethnic groups. The study revealed 132 species of minor or threatened food plants. They were distinguished in 85 spontaneous species (64 %) and 141 varieties belonging to 47 cultivated ones (36 %). Twenty-fourth cultivated species have only one variety, while 23 other species have 2 to 18. Forty-four plants species are considered as threatened throughout the whole country. According to the reduction in areas of occurrence or in the usage, 6, 19, 86 and 129 plant species were considered as very, somewhat and less threatened, respectively. The number of threatened food plants varied from 2 to 40, according to localities and from 10 to 50 local varieties and species at the majority of the ethnic groups, except for the Éwe, Lamba, Nawdba, Ife and Moba groups, which numbered more than 50 plants.Keywords: Threatened food plants, ethnobotanic, ethnocultural groups, Tog

Effect of a zinc oxide, at the cathode interface, on the efficiency of inverted organic photovoltaic cells based on the CuPc/C60 couple

The effect of ZnO buffer layer on the performances of inverted multilayers organic solar cells has been studied. ZnO:Al conductive films and insulating ZnO films deposited by spin coating have been probed. The ZnO buffer layer has been introduced between the ITO cathode and the Organic acceptor. The cells are based on the multilayer junctions bathocuproine/fullerene/copper phthalocyanine. The organic photovoltaic cells performances improvement depends of the ZnO layer introduced. ZnO:Al conductive layers decreases the potential barrier at the interface cathode/organic. This allows decreasing the series resistance which improves significantly the cell efficiency. Insulating ZnO increases only slightly the solar cells performance by increasing significantly the shunt resistance and therefore the open circuit voltage of the cells

Kentucky bluegrass invaded rangeland: ecosystem implications and adaptive management approaches

USDA-NRCS National Resources Inventory data indicates that between 2011 and 2015 Kentucky bluegrass (Poa pratensis) was present in 14.5% on non-Federal rangelands nationally and 86% in North Dakota, 63% in South Dakota, 40% in Kansas, 38% in Nebraska, and 32% in Montana. Native grasslands provide important services such as nutrient cycling, forage and habitat for wildlife and livestock, pollinator habitat, carbon capture, and regulation of hydrologic cycles, among others. Therefore, grassland degradation due to invasive plant species has far-ranging consequences for both human and ecological systems. We present information from a symposium at the 2019 Society for Range Management Annual Meeting. The symposium covered three topic areas that have been the foci of NGP Kentucky bluegrass research in the last five years: (1) impacts of Kentucky bluegrass on ecosystem services (especially soil water regulation, pollinator services, and forage production); (2) opportunities for using adaptive management approaches that include natural disturbances (such as fire and livestock grazing) for restoring and maintaining diverse grasslands; and (3) how to effectively overcome social barriers to treatment options aimed at restoring these grasslands. We present brief summaries of research progress on these topics. We conclude that despite great advances in knowledge related to Kentucky bluegrass invaded ecosystems there are still knowledge gaps regarding management of this novel ecosystem under changing climatic conditions as well as challenges regarding large scale adoption of management practices needed to manage these systems appropriately

Biophysical and electrochemical studies of protein-nucleic acid interactions

This review is devoted to biophysical and electrochemical methods used for studying protein-nucleic acid (NA) interactions. The importance of NA structure and protein-NA recognition for essential cellular processes, such as replication or transcription, is discussed to provide background for description of a range of biophysical chemistry methods that are applied to study a wide scope of protein-DNA and protein-RNA complexes. These techniques employ different detection principles with specific advantages and limitations and are often combined as mutually complementary approaches to provide a complete description of the interactions. Electrochemical methods have proven to be of great utility in such studies because they provide sensitive measurements and can be combined with other approaches that facilitate the protein-NA interactions. Recent applications of electrochemical methods in studies of protein-NA interactions are discussed in detail

Conformational Changes in DNA upon Ligand Binding Monitored by Circular Dichroism

Circular dichroism (CD) spectroscopy is an optical technique that measures the difference in the absorption of left and right circularly polarized light. This technique has been widely employed in the studies of nucleic acids structures and the use of it to monitor conformational polymorphism of DNA has grown tremendously in the past few decades. DNA may undergo conformational changes to B-form, A-form, Z-form, quadruplexes, triplexes and other structures as a result of the binding process to different compounds. Here we review the recent CD spectroscopic studies of the induction of DNA conformational changes by different ligands, which includes metal derivative complex of aureolic family drugs, actinomycin D, neomycin, cisplatin, and polyamine. It is clear that CD spectroscopy is extremely sensitive and relatively inexpensive, as compared with other techniques. These studies show that CD spectroscopy is a powerful technique to monitor DNA conformational changes resulting from drug binding and also shows its potential to be a drug-screening platform in the future

Biogenic and Synthetic Polyamines Bind Cationic Dendrimers

Biogenic polyamines are essential for cell growth and differentiation, while polyamine analogues exert antitumor activity in multiple experimental model systems, including breast and lung cancer. Dendrimers are widely used for drug delivery in vitro and in vivo. We report the bindings of biogenic polyamines, spermine (spm), and spermidine (spmd), and their synthetic analogues, 3,7,11,15-tetrazaheptadecane.4HCl (BE-333) and 3,7,11,15,19-pentazahenicosane.5HCl (BE-3333) to dendrimers of different compositions, mPEG-PAMAM (G3), mPEG-PAMAM (G4) and PAMAM (G4). FTIR and UV-visible spectroscopic methods as well as molecular modeling were used to analyze polyamine binding mode, the binding constant and the effects of polyamine complexation on dendrimer stability and conformation. Structural analysis showed that polyamines bound dendrimers through both hydrophobic and hydrophilic contacts with overall binding constants of Kspm-mPEG-G3 = 7.6×104 M−1, Kspm-mPEG-PAMAM-G4 = 4.6×104 M−1, Kspm-PAMAM-G4 = 6.6×104 M−1, Kspmd-mPEG-G3 = 1.0×105 M−1, Kspmd-mPEG-PAMAM-G4 = 5.5×104 M−1, Kspmd-PAMAM-G4 = 9.2×104 M−1, KBE-333-mPEG-G3 = 4.2×104 M−1, KBe-333-mPEG-PAMAM-G4 = 3.2×104 M−1, KBE-333-PAMAM-G4 = 3.6×104 M−1, KBE-3333-mPEG-G3 = 2.2×104 M−1, KBe-3333-mPEG-PAMAM-G4 = 2.4×104 M−1, KBE-3333-PAMAM-G4 = 2.3×104 M−1. Biogenic polyamines showed stronger affinity toward dendrimers than those of synthetic polyamines, while weaker interaction was observed as polyamine cationic charges increased. The free binding energies calculated from docking studies were: −3.2 (spermine), −3.5 (spermidine) and −3.03 (BE-3333) kcal/mol, with the following order of binding affinity: spermidine-PAMAM-G-4>spermine-PAMMAM-G4>BE-3333-PAMAM-G4 consistent with spectroscopic data. Our results suggest that dendrimers can act as carrier vehicles for delivering antitumor polyamine analogues to target tissues

Effect of SGLT2 inhibitors on stroke and atrial fibrillation in diabetic kidney disease: Results from the CREDENCE trial and meta-analysis

BACKGROUND AND PURPOSE: Chronic kidney disease with reduced estimated glomerular filtration rate or elevated albuminuria increases risk for ischemic and hemorrhagic stroke. This study assessed the effects of sodium glucose cotransporter 2 inhibitors (SGLT2i) on stroke and atrial fibrillation/flutter (AF/AFL) from CREDENCE (Canagliflozin and Renal Events in Diabetes With Established Nephropathy Clinical Evaluation) and a meta-Analysis of large cardiovascular outcome trials (CVOTs) of SGLT2i in type 2 diabetes mellitus. METHODS: CREDENCE randomized 4401 participants with type 2 diabetes mellitus and chronic kidney disease to canagliflozin or placebo. Post hoc, we estimated effects on fatal or nonfatal stroke, stroke subtypes, and intermediate markers of stroke risk including AF/AFL. Stroke and AF/AFL data from 3 other completed large CVOTs and CREDENCE were pooled using random-effects meta-Analysis. RESULTS: In CREDENCE, 142 participants experienced a stroke during follow-up (10.9/1000 patient-years with canagliflozin, 14.2/1000 patient-years with placebo; hazard ratio [HR], 0.77 [95% CI, 0.55-1.08]). Effects by stroke subtypes were: ischemic (HR, 0.88 [95% CI, 0.61-1.28]; n=111), hemorrhagic (HR, 0.50 [95% CI, 0.19-1.32]; n=18), and undetermined (HR, 0.54 [95% CI, 0.20-1.46]; n=17). There was no clear effect on AF/AFL (HR, 0.76 [95% CI, 0.53-1.10]; n=115). The overall effects in the 4 CVOTs combined were: Total stroke (HRpooled, 0.96 [95% CI, 0.82-1.12]), ischemic stroke (HRpooled, 1.01 [95% CI, 0.89-1.14]), hemorrhagic stroke (HRpooled, 0.50 [95% CI, 0.30-0.83]), undetermined stroke (HRpooled, 0.86 [95% CI, 0.49-1.51]), and AF/AFL (HRpooled, 0.81 [95% CI, 0.71-0.93]). There was evidence that SGLT2i effects on total stroke varied by baseline estimated glomerular filtration rate (P=0.01), with protection in the lowest estimated glomerular filtration rate (45 mL/min/1.73 m2]) subgroup (HRpooled, 0.50 [95% CI, 0.31-0.79]). CONCLUSIONS: Although we found no clear effect of SGLT2i on total stroke in CREDENCE or across trials combined, there was some evidence of benefit in preventing hemorrhagic stroke and AF/AFL, as well as total stroke for those with lowest estimated glomerular filtration rate. Future research should focus on confirming these data and exploring potential mechanisms