Quel rôle peut-on imputer aux banques à charte canadiennes dans la transmission des chocs monétaires des années quatre-vingt?

Cette recherche s’inscrit dans la foulée de nombreux travaux entrepris suite aux publications de Bernanke et Blinder (1988, 1992) ayant remis à l’avant-plan le rôle joué par le système bancaire dans la transmission de la politique monétaire. Nous proposons d’examiner la dynamique inhérente à certains postes du bilan des banques à charte canadiennes suite aux mouvement des principaux taux d’intérêt, habituellement jugés révélateurs des conditions monétaires du moment. Pour ce faire, nous avons recours à un modèle VAR hebdomadaire comportant à la fois, des éléments de l’actif et du passif des banques ainsi que les taux de rendement associés à divers instruments financiers. Cependant, dans le but de bien encadrer cette analyse, nous développons un modèle formel du comportement d’une banque où les seuls changements aux postes de son bilan suite aux mouvements de taux d’intérêt sont dictés par des ajustements de portefeuille visant à tirer avantage des écarts se creusant entre ceux-ci. Ce modèle théorique est soumis aux variations de taux d’intérêt issues du modèle empirique VAR. Les mouvements observés aux postes du bilan de cette banque « témoin » fournissent un guide utile permettant d’interpréter de façon éclairée les résultats empiriques obtenus. À cet égard, l’exercice proposé montre qu’il est possible d’établir un parallèle assez étroit entre l’évolution des postes du bilan de la banque hypothétique et celle captée par le modèle VAR et ainsi apporte un certain support à l’approche traditionnelle sur le rôle joué par les banques dans la transmission des chocs monétaires.This paper can be seen as a contribution to a growing literature initiated by Bernanke and Blinder (1988, 1992) which have examined the role played by the banking system in the transmission of monetary policy. We propose to study the dynamic behaviour of the balance sheet of Canadian chartered banks following a shock to some key interest rates which are good indicators of the prevailing monetary conditions. More specifically, we estimate a weekly VAR model which comprises key asset and liabilities elements as well as rates of return on major financial instruments. However, to guide this empirical inquiry, we set up a model of a representative bank which adjusts its balance sheet elements according to the interest rate spreads arising in the financial markets. This theoretical model is then subjected to the same interest rate shocks than those imposed on the VAR model: the adjustments observed in this laboratory will prove quite useful to assess the significance of the empirical results uncovered by the VAR model. Overall, we find that both approaches give rise to quite similar dynamic responses which tends to support the traditional role of the banking sector in the transmission of monetary policy

A fully traits-based approach to modeling global vegetation distribution

Dynamic Global Vegetation Models (DGVMs) are indispensable for our understanding of climate change impacts. The application of traits in DGVMs is increasingly refined. However, a comprehensive analysis of the direct impacts of trait variation on global vegetation distribution does not yet exist. Here, we present such analysis as proof of principle. We run regressions of trait observations for leaf mass per area, stem-specific density, and seed mass from a global database against multiple environmental drivers, making use of findings of global trait convergence. This analysis explained up to 52% of the global variation of traits. Global trait maps, generated by coupling the regression equations to gridded soil and climate maps, showed up to orders of magnitude variation in trait values. Subsequently, nine vegetation types were characterized by the trait combinations that they possess using Gaussian mixture density functions. The trait maps were input to these functions to determine global occurrence probabilities for each vegetation type. We prepared vegetation maps, assuming that the most probable (and thus, most suited) vegetation type at each location will be realized. This fully traits-based vegetation map predicted 42% of the observed vegetation distribution correctly. Our results indicate that a major proportion of the predictive ability of DGVMs with respect to vegetation distribution can be attained by three traits alone if traits like stem-specific density and seed mass are included. We envision that our traits-based approach, our observation-driven trait maps, and our vegetation maps may inspire a new generation of powerful traits-based DGVMs

Global quantification of contrasting leaf life span strategies for deciduous and evergreen species in response to environmental conditions.

Aim Species with deciduous and evergreen leaf habits typically differ in leaf life span (LLS). Yet quantification of the response of LLS, within each habit, to key environmental conditions is surprisingly lacking. The aim of this study is to quantify LLS strategies of the two leaf habits under varying temperature, moisture and nutrient conditions, using a global database. We hypothesize that deciduous LLS reflects the length of the growing season, avoiding unfavourable conditions regardless of the cause. Evergreen species adjust to unfavourable periods and amortize lower net carbon gains over several growing seasons, with increasing LLS associated with increasingly short favourable versus unfavourable season lengths. Location Global. Methods Data on LLS and environmental variables were compiled from global datasets for 189 deciduous and 506 evergreen species across 83 study locations. Individual and combined effects of measures of seasonality of temperature, water and nutrient availability on length of the growing season and on LLS were quantified using linear mixed models. The best models for predicting LLS were obtained using Akaike's information criterion (AIC) and ΔAIC. Results The LLS of deciduous and evergreen species showed opposite responses to changes in environmental conditions. Under unfavourable conditions, deciduous LLS decreases while evergreen LLS increases. A measure of temperature alone was the best predictor of the growing season. The LLS of deciduous species was independent of environmental conditions after expressing LLS in relation to the number of growing seasons. Evergreen species, on the other hand, adjusted to unfavourable conditions by increasing LLS up to four growing seasons. Contrary to expectations, variation in LLS was best explained solely by temperature, instead of by combined measures of temperature, moisture and nutrient availability. Shifts in the photosynthesis to respiration balance might provide a physiological explanation. Main conclusions Temperature, and not drought or nutrient availability, is the primary driver of contrasting responses of LLS for different leaf habit types. © 2011 Blackwell Publishing Ltd

A novel way to understand plant species preferences in relation to groundwater discharge condtions using a trait-based approach

Groundwater discharge sites harbour characteristic and often rare plant communities that differ substantially from groundwater recharge sites. It is not known which abiotic conditions at these sites drive the differences in community composition. A trait-based approach, which relates species traits to abiotic conditions, may provide insight in this relationship and improve conservation management of these characteristic communities. We used this approach to identify the following: (i) dominant abiotic conditions that shape plant communities at discharge sites and (ii) characteristic traits associated with these abiotic conditions. First, we performed a (qualitative) literature survey to relate plant traits to various abiotic conditions at discharge sites. Second, we performed a meta-analysis to quantitatively test the trait selection at discharge sites. For the meta-analysis, we compiled a species discharge preference database (n=170), based on literature and field data. We performed linear regression to relate traits to species discharge preference. Only 5 out of the 11 traits tested (low leaf phosphorus content, high leaf N:P, low rate of clonal reproduction, low maximum height and high seed mass) were significantly related to discharge preference, while the explained variance was low (

Global quantification of contrasting leaf life span strategies for deciduous and evergreen species in response to environmental conditions

Aim Species with deciduous and evergreen leaf habits typically differ in leaf life span (LLS). Yet quantification of the response of LLS, within each habit, to key environmental conditions is surprisingly lacking. The aim of this study is to quantify LLS strategies of the two leaf habits under varying temperature, moisture and nutrient conditions, using a global database. We hypothesize that deciduous LLS reflects the length of the growing season, avoiding unfavourable conditions regardless of the cause. Evergreen species adjust to unfavourable periods and amortize lower net carbon gains over several growing seasons, with increasing LLS associated with increasingly short favourable versus unfavourable season lengths. Location Global. Methods Data on LLS and environmental variables were compiled from global datasets for 189 deciduous and 506 evergreen species across 83 study locations. Individual and combined effects of measures of seasonality of temperature, water and nutrient availability on length of the growing season and on LLS were quantified using linear mixed models. The best models for predicting LLS were obtained using Akaike's information criterion (AIC) and ΔAIC. Results The LLS of deciduous and evergreen species showed opposite responses to changes in environmental conditions. Under unfavourable conditions, deciduous LLS decreases while evergreen LLS increases. A measure of temperature alone was the best predictor of the growing season. The LLS of deciduous species was independent of environmental conditions after expressing LLS in relation to the number of growing seasons. Evergreen species, on the other hand, adjusted to unfavourable conditions by increasing LLS up to four growing seasons. Contrary to expectations, variation in LLS was best explained solely by temperature, instead of by combined measures of temperature, moisture and nutrient availability. Shifts in the photosynthesis to respiration balance might provide a physiological explanation. Main conclusions Temperature, and not drought or nutrient availability, is the primary driver of contrasting responses of LLS for different leaf habit types.</p

Differential modulation of enterocyte-like Caco-2 cells after exposure to short-chain fatty acids

The response of intestinal epithelial cells to short-chain fatty acids, which are increasingly used as food additives, was investigated. Human small intestinal epithelial cell model Caco-2 cells were exposed to formate, propionate and butyrate to assess their effect on cellular growth, metabolism, differentiation and protection against bacteria. The Caco-2 cells were entirely grown in the different short-chain fatty acids and respective growth patterns were determined. Differentiated cells were exposed to 0-20 mM short-chain fatty acids for 48 h and changes in DNA, RNA, (glyco)protein syntheses, sucrase isomaltase activity, transepithelial electrical resistance and protection against Salmonella enteritidis were measured. The short-chain fatty acids, altered linearly and differentially the growth pattern ranging from stimulation by formate to inhibition by butyrate. Formate inhibited cellular metabolism. Low concentrations of up to 5 mM propionate and 2 mM butyrate stimulated metabolism, while higher doses were inhibitory. Formate had no effect on sucrase isomaltase enzyme activity and transepithelial electrical resistance, whereas propionate and butyrate increased these markers of differentiation. Infection with S. enteritidis did not benefit from the short-chain fatty acid-induced transepithelial electrical resistance. It is concluded that formate, propionate and butyrate selectively and differentially modulate growth characteristics, cellular metabolism, sucrase isomaltase activity and transepithelial electrical resistance in a concentration- and carbon atom-related fashion. The short-chain fatty acid-induced transepithelial electrical resistance does not confer protection against S. enteritidis

Age-adjusted d-dimer cut-off levels increase the clinical utility of ruling out pulmonary embolism in elderly patients

Background: The D-Dimer (DD) test, used to rule out pulmonary embolism (PE), is less useful in elderly patients due to a lower specificity. We retrospectively derived and validated the efficacy of an age- dependent DD cut-off combined with clinical probability for the exclusion of PE in four large management studies. Methods: The derivation set consisted of consecutive outpatients > 50 years with suspected PE. The DD cut-off was based on ROC-curve analyses. The proportion of patients with a normal DD test and the false negative rates were calculated. The age-adjusted DD cut-off was then validated in patients > 50 years with an unlikely Wells score (> 4) or a non-high Revised Geneva Score (> 10) from two independent cohorts of consecutive patients, respectively. The Vidas DD test was used in all cohorts (combined with Tinaquant in validation set 1). Results: The new DD cut-off was defined as patient's age x 10 μg/L. Using the new cut-off PE could be excluded in a higher number of patients > 50 years (Table). Among patients > 70 years, the increase in the proportion of patients with a DD below the new cut-off compared to the old cut-off was 2.3-fold in the derivation set, 2.0-fold in validation set 1 and 2.2-fold in validation set 2, respectively. [Table represented ]Conclusion: An age-adjusted cut-off of the D-dimer combined with clinical probability greatly increases the proportion of elderly patients in whom PE can be safely excluded. Disclosure of interest: none declared