Hyperspectral imaging to characterize table grapes

Table grape quality is of importance for consumers and thus for producers. Its objective quality is usually determined by destructive methods mainly based on sugar content. This study proposed to evaluate the possibility of hyperspectral imaging to characterize table grapes quality through its sugar (TSS), total flavonoid (TF), and total anthocyanin (TA) contents. Different data pretreatments (WD, SNV, and 1st and 2nd derivative) and different methods were tested to get the best prediction models: PLS with full spectra and then Multiple Linear Regression (MLR) were realized after selecting the optimal wavelengths thanks to the regression coefficients (coefficients) and the Variable Importance in Projection (VIP) scores. All models were good at showing that hyperspectral imaging is a relevant method to predict sugar, total flavonoid, and total anthocyanin contents. The best predictions were obtained from optimal wavelength selection based on coefficients for TSS and from VIPs optimal wavelength windows using SNV pre-treatment for total flavonoid and total anthocyanin content. Thus, good prediction models were proposed in order to characterize grapes while reducing the data sets and limit the data storage to enable an industrial use

Dissolved matter fluxes in the inner delta of the River Niger

Abstract This study is part of the EQUANIS programme, the objectives of which are (a) estimating inputs from the River Niger to the inner Delta; (b) computing the hydrological balance; and (c) monitoring the quality of water in the central lacustrine basin. Eleven sampling locations were selected near gauging stations, both on the Niger River and its main tributary, the Bani River. Those sites have been sampled weekly since July 1990. The inner delta of the Niger River is a system particularly subject to sahelian and sub-desert climatic conditions and characterized by large flood plains. Time series of input water volumes in the inner delta, and of the water losses within it, show that the water losses are high, due to the intense evaporation, and vary from 6 to 40 km3. The water .losses reach their maximum during the wettest years-up to 47%, and minimum during the driest years-only 32%, due to the reduction of the flooded area. The surface of the flooded area is inferred from the hydrological balance. The preliminary results of this study indicate that the Niger and Bani rivers have low levels of dissolved element concentrations. The mean conductivity values, ranging from 50-80 pS cm-', increase regularly during the low water stage and decrease drastically with rising water. The pH values are slightly basic, ranging from 7.1 to 8. Silica and bicarbonates are the main dissolved species; they always represent more than 75% of TDS. In May, when the rising water stage begins, the waters are poorly mineralized at the input of the delta, while they have been enriched during the dry season in the delta. A good mass balance is found between inputs and outputs through the delta. However, a disequilibrium appears at the sampling sites within the basin, which could be partially linked to poor mixing between the Niger and Bani river waters. The first results from the upper basin and below the inner delta, show low concentrations of matter. The specific dissolved loads vary between 10-12 t km-' year-' for the Niger River and 2.5 t km-2 year-' for the Bani River. The annual input in the inner delta was about 2.2 X lo6 t in 1992-1993. Chemical budgets show a saline deposit of 0.3 x lo6 t in the inner delta. Seasonal variations of the dissolved matter fluxes are very different between the upper and lower parts of the inner delta, due to the breaking of the annual flood and to the more important flood plains in the upper delta. Los flujos de materiales disueltos en el delta inerior del Niger Resumen Es presente estudio forma parte del programa EQUANIS, cuyos objetivos son (a) estimación de los aportes del río Niger al delta interior, (b) cómputo del balance gídrico, y (c) monitoreo de la calidad del agua en la cuenca lacustre central. Se seleccionaron once sitios de muestre0 próximos a las estaciones de aforo tanto en el Niger como en su principal afluente, el Bani. Desde julio de 1990 se llevaron a cabo allí muestreos semanales. EI delta interior del Niger is us sistema particular sometido a condiciones interior, y de pérdidas de agua en is mismo, muestran que las pérdidas son elevadas debido a la evaporación intensa, y fluctúan entre 40 y 6 km3. Las pérdidas de agua son máximas durante los años más húmedos (hasta un 47%) y mínimas durante los años más socos (solo 32%) debido a la reducción de las Breas inundadas. La superficie inundada se deduce del balance hídrico. Los resultados preliminares del estudio indican que los ríos Niger y Bani tienen un bajo nivel de concentración de elementos en disolución. Los valores medios de conductividad que van de 50 a 80 pS cm" se incrementan regularmente durante el período de estiaje y disminuyen drásticamente en períodos de avenidas y variacíon de niveles. Los valores de pH son ligeramente básicos, de 7.1 a 8. Los principales materiales dusueltos son el sílice y los bicarbonatos; siempre representan más del 75% del TDS. En mayo, cuando se inicia el período de crecida, las aguas contienen pocos minerales en la entrada del delta mientras que se han concentrado durante la estación seca del delta. Se observa un buen balance de masa en el delta entre los aportes y descargas, pero aparece un desequilibrio en los sitios de muestre0 dentro de la cuenca, que puede atribuirse parcialmente a una mala mezcla entre las aguals del Niger y del Bani. Los primeros resultados en la cuenca superior y baja del delta interior muestran bajas concentraciones de material. Las cargas disueltas específicas fluctúan entre 10 y 12 t km-2 año-' para el río Niger y 2.5 t km-* año-' para el río Bani. El aporte anual en el delta interior fue de unos 2.2 X lo6 t en 1992-1993. Los balances químicos presentan un depósito salino de 0.3 X lo6 t en el delta interior. Las variaciones estacionales de los flujos de materiales son muy diferentes entre las partes alta y baja del delta interior, debido al inicio de la crecida anual y a las más importantes planicies de inundación en la parte superior del delta

HSC-CLAUDS survey: The star formation rate functions since z ~ 2 and comparison with hydrodynamical simulations

Star formation rate functions (SFRFs) give an instantaneous view of the distribution of star formation rates (SFRs) in galaxies at different epochs. They are a complementary and more stringent test for models than the galaxy stellar mass function, which gives an integrated view of the past star formation activity. However, the exploration of SFRFs has been limited thus far due to difficulties in assessing the SFR from observed quantities and probing the SFRF over a wide range of SFRs. We overcome these limitations thanks to an original method that predicts the infrared luminosity from the rest-frame UV/optical color of a galaxy and then its SFR over a wide range of stellar masses and redshifts. We applied this technique to the deep imaging survey HSC-CLAUDS combined with near-infrared and UV photometry. We provide the first SFR functions with reliable measurements in the high- and low-SFR regimes up to $z=2$ and compare our results with previous observations and four state-of-the-art hydrodynamical simulations.Comment: 29 pages, 19 figure

Modélisation conceptuelle globale du régime du transport particulaire sur les fleuves tropicaux d'Afrique : application aux bassins du Niger supérieur et du Bani, Mali

Sur le fleuve Niger, les relations entre concentrations en Matières En Suspension (MES) et débits liquides montrent, à l'échelle d'une crue annuelle, des cycles d'hystérésis orthogrades. Le modèle présenté dans cet article reproduit les variations saisonnières de ces MES à partir du seul débit liquide. Il suppose que les MES proviennent de deux sources distinctes : le système " versants + réseau hydrographique secondaire ", siège d'une érosion saisonnière temporaire et le réseau hydrographique principal, siège d'une érosion permanente. Le modèle représente schématiquement la production de MES provenant de ces deux sources par le biais de deux réservoirs de MES. Le premier contient un stock en MES temporaire et limité. Ce stock, maximum au début de la crue annuelle (stock initial), est mobilisé et entraîné au cours de la saison pluvieuse en produisant un flux journalier, supposé être, à un instant donné, proportionnel au stock restant et à une fonction de puissance du débit. Le second, contient un stock de MES illimité et disponible en permanence. La mobilisation de ce stock produit un flux journalier, supposé être aussi une fonction de puissance du débit, et dont l'importance sera limité par la capacité du cours d'eau. Les cinq paramètres du modèle sont calibrés à l'aide des données acquises durant huit années hydrologiques (1991/92 à 1998/99) sur deux stations du Niger amont (Banankoro et Douna). Malgré les limites d'utilisation actuelles liées à la détermination du stock initial, le modèle présenté reconstitue de façon satisfaisante les variations annuelles des concentrations en MES et offre des perspectives intéressantes pour modéliser l'évolution temporelle des MES observées tant pour les fleuves tropicaux unimodaux que pour les petits bassins versants africains. En termes de flux annuels, le modèle n'apporte pas d'amélioration sensible par rapport à un ajustement statistique simple entre les volumes écoulés et les flux de MES. Cependant, il permet aussi de déterminer les variations de flux au cours de l'année, information qui ne peut être obtenue avec un modèle de régression statistique.Estimating temporal variability of suspended sediment concentrations in a watershed is important for a number of reasons (e.g., sediment yield estimation, provision of input data for reservoir sediment-deposition models and water quality models). Three different approaches have been adopted for modelling erosion and sediment transport: physical erosion models (Wicks and Bathurst, 1996); conceptual models (Negev, 1967; Pinheiro and Caussade, 1996); and empirical models (Walling, 1977; Asselman, 1977). Physical and conceptual models usually require rainfall intensity data. In African tropical river catchments, however, temporal and spatial variability of rainfall are not well known; in case of the Niger, water discharge is the only reliable hydrological parameter. This study proposes a model of temporal changes in suspended sediment concentrations using only water discharge data, thereby eliminating the need for rainfall parameters.Daily discharge and weekly suspended sediment concentration data (from 1991/92 to 1998/99) gathered at two monitoring stations of the Upper Niger (Banankoro and Douna) (Figure 1) were used to study relationships between suspended sediment concentration and river discharge.At each gauging station on the Niger, the relationship between water discharge and suspended sediment concentration during the annual flood is characterized by clockwise hysteresis (Figure 3). Moreover, several other African single-annual-flood rivers-unimodal rivers-also exhibit this type of relationship (Kattan et al., 1987; Olivry et al., 1988; Orange, 1992). This cyclicity suggests a three-stage description of sediment transport dynamics: (1) At the beginning of the rainfall season, sediments are imported by hill-slope surface runoff, re-entrainment of deposits in the channel network, and riverbed erosion. The first two sources consist of easily mobilizable material available throughout the catchment at the beginning of the hydrological year. (2) Sediment availability decreases with time as the soil becomes stabilised by vegetation during the rainy season. Erosion is consequently reduced, despite increased discharge. (3) During the period represented by the falling limb of the flood hydrograph, mobilizable material has been depleted or cannot be entrained; what suspended sediment there is originates upstream and from bank and bed erosion-permanently available sources. Non-seasonal sediment sources are grouped under the label of "continuous erosion."We propose a lumped conceptual model of suspended-sediment concentration variations over the hydrological year. The model divides the erosion, transport and deposition processes into those acting on hill-slopes and those acting in the channel network, and assumes that both are explainable by water discharge Q(t) alone. The hill-slope/channel distinction is based on the fact that suspended sediment transport in a river depends not only on transport, bank and bed-erosion capacity, but also on the amount of available material in the drainage catchment.Sediment transport (in tons per day) for the hydrological year is thus computed as the sum of two independent daily contributions of sediment discharge. The first, Fmob(t), originates from a limited reservoir which is full at the beginning of the flood and available only temporarily, during the rainy season. At a given time t, the sediment input Fmob(t) is proportional to the amount remaining in the limited reservoir and to a power function of water discharge (Eq. (1), Eq. (2)). The second reservoir, temporally and quantitatively unlimited, injects a daily sediment discharge Fec(t) which is a power function of water discharge (Eq. (3)); Fec(t) is limited only by river capacity. The final concentration is obtained from Equation (4).The five model parameters were calibrated with concentration and discharge data from hydrological years 1991/92 to 1995/96. The unlimited reservoir parameters were estimated using Equation (6) with data taken during the decreasing stage. Initial sediment in the limited reservoir was estimated with Equation (7), using observed concentrations and concentrations derived from continuous erosion (Eq. (3)). Two parameters related to the decrease in initial sediment loads were obtained by optimization of the mean Nash criterion between observed and calculated concentrations (Figure 6). Some physical interpretations were ascribed to coefficients related to the limited reservoir.Despite the limitations of assuming a single initial mobilizable reservoir, predictions of temporal sediment-concentration patterns during the annual flood were satisfactory (Figure 7, Table 2). The model also simulated some observed sediment concentration peaks associated with sudden water discharge variations during the rising limb of the annual flood. Best results were obtained by varying initial sediment reservoir estimates for different hydrological years (Table 3)-the model could therefore be improved by highlighting parameters that determine sediment loads at the beginning of the hydrological year.The model does not give better estimates of annual sediment yield than simple regression of annual water volume (Table 4). However, it is able to reproduce the temporal variability of the sediment flux during the annual flood. The small size of the data set makes evaluation of the performance of this model difficult; for better assessment, it should applied to other data gathered on the same catchments or on other large tropical rivers. Model parameter values could also be explained by drainage basin characteristics