Predicting tropical forest stand structure parameters from Fourier transform of very high-resolution remotely sensed canopy images

1. Predicting stand structure parameters for tropical forests from remotely sensed data has numerous important applications, such as estimating above-ground biomass and carbon stocks and providing spatial information for forest mapping and management planning, as well as detecting potential ecological determinants of plant species distributions. As an alternative to direct measurement of physical attributes of the vegetation and individual tree crown delineation, we present a powerful holistic approach using an index of canopy texture that can be extracted from either digitized air photographs or satellite images by means of two-dimensional spectral analysis by Fourier transform. 2. We defined an index of canopy texture from the ordination of the Fourier spectra computed for 3545 1-ha square images of an undisturbed tropical rain forest in French Guiana. This index expressed a gradient of coarseness vs. fineness resulting from the relative importance of small, medium and large spatial frequencies in the Fourier spectra. 3. Based on 12 1-ha control plots, the canopy texture index showed highly significant correlations with tree density (R2 = 0·80), diameter of the tree of mean basal area (R2 = 0·71), distribution of trees into d.b.h. classes (R2 = 0·64) and mean canopy height (R2 = 0·57), which allowed us to produce reasonable predictive maps of stand structure parameters from digital aerial photographs. 4. Synthesis and applications. Two-dimensional Fourier analysis is a powerful method for obtaining quantitative characterization of canopy texture, with good predictive ability on stand structure parameters. Forest departments should use routine forest inventory operations to set up and feed regional databases, featuring both tree diameter figures and digital canopy images, with the ultimate aims of calibrating robust regression relationships and deriving predictive maps of stand structure parameters over large areas of tropical forests. Such maps would be particularly useful for forest classification and to guide field assessment of tropical forest resources and biodiversity

Impaired early B cell tolerance in patients with rheumatoid arthritis

Autoantibody production is a characteristic of most autoimmune diseases including rheumatoid arthritis (RA). The role of these autoantibodies in the pathogenesis of RA remains elusive, but they appear in the serum many years before the onset of clinical disease suggesting an early break in B cell tolerance. The stage of B cell development at which B cell tolerance is broken in RA remains unknown. We previously established in healthy donors that most polyreactive developing B cells are silenced in the bone marrow, and additional autoreactive B cells are removed in the periphery. B cell tolerance in untreated active RA patients was analyzed by testing the specificity of recombinant antibodies cloned from single B cells. We find that autoreactive B cells fail to be removed in all six RA patients and represent 35–52% of the mature naive B cell compartment compared with 20% in healthy donors. In some patients, RA B cells express an increased proportion of polyreactive antibodies that can recognize immunoglobulins and cyclic citrullinated peptides, suggesting early defects in central B cell tolerance. Thus, RA patients exhibit defective B cell tolerance checkpoints that may favor the development of autoimmunity

Spatial and temporal dynamics of suspended sediment concentrations in coastal waters of the South China Sea, off Sarawak, Borneo: ocean colour remote sensing observations and analysis

High-quality ocean colour observations are increasingly accessible to support various monitoring and research activities for water quality measurements. In this paper, we present a newly developed regional total suspended solids (TSSs) empirical model using MODIS Aqua's Rrs(530) and Rrs(666) reflectance bands to investigate the spatial and temporal variation in TSS dynamics along the southwest coast of Sarawak, Borneo, with the application of the Open Data Cube (ODC) platform. The performance of this TSS retrieval model was evaluated using error metrics (bias = 1.0, MAE = 1.47, and RMSE = 0.22, in milligrams per litre) with a log10 transformation prior to calculation as well as using a k-fold cross-validation technique. The temporally averaged map of the TSS distribution, using daily MODIS Aqua satellite datasets from 2003 until 2019, revealed that large TSS plumes were detected – particularly in the Lupar and Rajang coastal areas – on a yearly basis. The average TSS concentration in these coastal waters was in the range of 15–20 mg L−1. Moreover, the spatial map of the TSS coefficient of variation (CV) indicated strong TSS variability (approximately 90 %) in the Samunsam–Sematan coastal areas, which could potentially impact nearby coral reef habitats in this region. Study of the temporal TSS variation provides further evidence that monsoonal patterns drive the TSS release in these tropical water systems, with distinct and widespread TSS plume variations observed between the northeast and southwest monsoon periods. A map of relative TSS distribution anomalies revealed strong spatial TSS variations in the Samunsam–Sematan coastal areas, while 2010 recorded a major increase (approximately 100 %) and widespread TSS distribution with respect to the long-term mean. Furthermore, study of the contribution of river discharge to the TSS distribution showed a weak correlation across time at both the Lupar and Rajang river mouth points. The variability in the TSS distribution across coastal river points was studied by investigating the variation in the TSS pixels at three transect points, stretching from the river mouth into territorial and open-water zones, for eight main rivers. The results showed a progressively decreasing pattern of nearly 50 % in relation to the distance from shore, with exceptions in the northeast regions of the study area. Essentially, our findings demonstrate that the TSS levels on the southwest coast of Sarawak are within local water quality standards, promoting various marine and socio-economic activities. This study presents the first observation of TSS distributions in Sarawak coastal systems with the application of remote sensing technologies and aims at enhancing coastal sediment management strategies for the sustainable use of coastal waters and their resources.</p

Sovereign default history: evidence of supranationals' preferred creditor status

Low Default Rate to Supranationals: Fitch Ratings’ study of sovereign defaults to different groups of creditors (bilateral official, private, and supranational) in 1999-2018 shows that most defaults to Fitch-rated supranationals are accompanied by defaults to other groups of creditors. Our annual observations show that there have been only three cases of default to multilateral development banks (MDBs) not accompanied by a default to another official or private creditor: Iran (2013), Syria (2002) and Yugoslavia (until 2003). For the survey we used the Bank of Canada database and our own default statistics on MDBs. Joint Default Rates: Scenarios involving a joint default to a supranational and another official creditor are more frequent, while there was no joint default to both a supranational and private creditor. This indicates that countries defaulting to supranationals are in most cases ones with limited or no access to capital markets, and relying largely on assistance from public development agencies. Evidence of Preferred Creditor Status: These statistics provide evidence of MBDs’ preferred creditor status (PCS). PCS is a widely accepted principle under which MDBs are given priority for repayment of debt in the event of a sovereign borrower experiencing financial stress. The servicing of MDBs’ non-sovereign loans is also protected against restrictions on foreign exchange

La Juste Valeur en normes IFRS et la performance financière dans un contexte de marché non efficient

International audienc

Provisionnement des pertes attendues sous IFRS 9 et conservatisme comptable : le cas des banques multilatérales de développement

International audienceLes banques multilatérales de développement ont pour vocation de financer les Etats et les économies des pays en développement en levant des fonds sur les marchés. Elles bénéficient d’un statut supranational. Le nouveau modèle d'identification et d'évaluation des prêts non performants (Non Performing Assets) qui est promu par la norme IFRS 9 (Phase 2) — et prochainement par les US GAAP (ASC 450 & 310, FASB) — devrait a priori profondément impacter l’évaluation des provisions pour dépréciation de leur portefeuille de prêts. Abandonnant la méthode de provisionnement fondée sur les pertes encourues (IAS 39), les normalisateurs comptables requièrent désormais l’utilisation d’une méthode prospective reposant sur une évaluation des pertes de crédit attendues (Expected Credit Loss, ECL). La norme IFRS 9 (Phase 2) est entrée en vigueur au 1er janvier 2018 et les US GAAP introduiront l’ECL en 2020.- Nous proposons une méthode spécifique visant à estimer les ECL sur le portefeuille de prêts des banques multilatérales de développement, de l’appliquer au portefeuille de prêts d’un panel et d’effectuer une comparaison avec les provisions pour pertes sur crédits actuellement constatées. Cette étude exploratoire a pour objectif d’évaluer l’impact prévisible de la mise en œuvre du modèle de provisionnement fondé sur les ECL, en termes d’impact sur la qualité de l’information comptable, au regard des acteurs du marché et des agences de notation

Provisionnement des pertes attendues sous IFRS 9 et conservatisme comptable : le cas des banques multilatérales de développement

International audienceLes banques multilatérales de développement ont pour vocation de financer les Etats et les économies des pays en développement en levant des fonds sur les marchés. Elles bénéficient d’un statut supranational. Le nouveau modèle d'identification et d'évaluation des prêts non performants (Non Performing Assets) qui est promu par la norme IFRS 9 (Phase 2) — et prochainement par les US GAAP (ASC 450 & 310, FASB) — devrait a priori profondément impacter l’évaluation des provisions pour dépréciation de leur portefeuille de prêts. Abandonnant la méthode de provisionnement fondée sur les pertes encourues (IAS 39), les normalisateurs comptables requièrent désormais l’utilisation d’une méthode prospective reposant sur une évaluation des pertes de crédit attendues (Expected Credit Loss, ECL). La norme IFRS 9 (Phase 2) est entrée en vigueur au 1er janvier 2018 et les US GAAP introduiront l’ECL en 2020.- Nous proposons une méthode spécifique visant à estimer les ECL sur le portefeuille de prêts des banques multilatérales de développement, de l’appliquer au portefeuille de prêts d’un panel et d’effectuer une comparaison avec les provisions pour pertes sur crédits actuellement constatées. Cette étude exploratoire a pour objectif d’évaluer l’impact prévisible de la mise en œuvre du modèle de provisionnement fondé sur les ECL, en termes d’impact sur la qualité de l’information comptable, au regard des acteurs du marché et des agences de notation

L'impact de la structure du capital sur l'activité du microcrédit en Côte d’Ivoire

International audienc