Geochemistry And Organic Petrology Of Boreal And Subarctic Peats In Canada

Five peat-forming environments were investigated for their organic petrological, mineralogical and geochemical characteristics. Wetlands studied included a salt marsh (Nova Scotia) and four peatlands: a freshwater domed bog (Nova Scotia), a fen (Alberta) and two peat plateau bogs (Northwest Territories). These diverse localities provided the opportunity to assess the influence of natural and anthropogenic factors on peat geochemistry in different depositional environments. Core samples were analyzed using the following methods: organic petrology (maceral analysis and reflectance measurements), low and high temperature ashing, x-ray diffraction, INAA and sulfur analysis, ICP-MS, radiocarbon and cesium dating.;Changes in maceral composition generally correlate with shifts in reflectance, and are useful indicators of the degree of degradation and oxidation in various depositional environments. A downcore decrease of fluorescing and red reflecting huminite macerals shows an increase in the degree of degradation, while an abundance of pyrofusinite in certain intervals is indicative of periods of drought and fire activity. In the salt marsh, oxyfusinite and algae are common.;Br, Cl, I and Se exhibit a strong affinity with the organic fraction and are consequently enriched in peat. Distribution of elements associated with the inorganic fraction on the other hand, can generally be explained in terms of mineral matter distribution.;Peat acts as a sink for air- and waterborne elements. Main factors affecting elemental concentration and distribution are geology of the substratum, proximity to the marine environment, elemental affinity, permafrost, redox changes in the zone of water table fluctuation, tephra incorporation, botanical composition, plant bioaccumulation, degree of degradation of peat, and anthropogenic activity. In particular, a substantial enrichment immediately above the permafrost boundary reflects the influence of permafrost on the mobilization of elements.;Framboidal and anhedral pyrite crystals occurring in association with organic matter are observed in both brackish and freshwater peat-forming systems.;A model was developed in the domed bog, showing that pH, botanical, mineralogical and geochemical composition of peat are related and dependent on the trophic conditions. Furthermore, this model can be useful to help understand characteristics of coal deposits

Conditional Betas: Asymmetric Responses to Good and Bad News

In this dissertation we propose a theoretical model for conditional betas. Within a rational expectation equilibrium model, we provide a precise characterization of the dynamics of betas and the price of beta risk in terms of the model's primitive parameters and state variables. The expressions reveal that during periods of higher uncertainty, the investor requires a higher market premium. Likewise, the conditional betas also respond to levels of uncertainty; depending on the cash-flow properties of the asset, the asset's beta can increase or decrease on higher uncertainty. Because of the connection with uncertainty, conditional betas derive the stochastic properties from investor beliefs. One of such properties is the asymmetric response to positive and negative news. We also provide empirical evidence of the model's predictions about the dynamics of betas. For this empirical investigation, we propose an econometric specification that provides time-varying estimates of betas and relates them, non-linearly, to investor beliefs. As a by-product, we suggest proxies for investor beliefs and uncertainty that can be extracted from stock returns. The dynamics implied by the estimated parameters confirms the model's prediction that value and growth betas have opposing sensitivity to the levels of uncertainty.Doctor of Philosoph

Differentiated management of alfalfa fields: a positive impact on butterfly populations (Lepidotera: Rhopalocera)

The impact of differentiated management of alfalfa fields on butterfly populations (Rhopalocera) was investigated in 2009 and 2010 on 18 sites in Champagne-Ardennes and 6 in Haute-Normandie (France), in comparison with both conventionally managed alfalfa and cereal crops. The STERF method (Suivi Temporel des Rhopalocères de France), the national French program for butterfly populations follow up, was used. Alfalfa itself (classical management) and moreover a flowered strip maintaining (7 m-wide band alternating non-swath in each cut) are significantly favourable to richness (31 species on the 43 observed, compared with 15 in and on the edge of cereal fields) and the abundance of butterflies (53 ± 6 butterflies per 10 minutes of counting in the non-mown strip, against 15 ± 2 on the edge of mowed alfalfa crops and 6 ± 1 on the edge of cereal fields). The most abundant species were Vanessa cardui (amazing position linked to the exceptional migration of 2009, with a particular concentration on alfalfa), Pieris rapae, Polyommatus icarus, Colias croceus, Pieris brassicae, Aglais io and Pieris napi. The more the species were common, the more they seemed to be favoured by these alfalfa blooms. Bloom alfalfa condition is an essential parameter, especially in the second half of the season, when wildflowers are less numerous. There is an additional interest of the flowering bands of alfalfa for species such as P. icarus (sedentary) and C. croceus (migratory), whose caterpillars can feed with alfalfaL'intérêt de la gestion différenciée des parcelles de luzerne pour les populations de Rhopalocères a été étudié en 2009 et 2010 sur 18 sites en Champagne-Ardennes et 6 en Haute-Normandie, en comparaison avec des luzernières traitées classiquement et des cultures de céréales d'hiver. La méthode du Suivi Temporel des Rhopalocères (papillons de jour) de France (STERF), programme national de comptage des papillons sans capture a été utilisée. La luzerne en elle-même (gestion classique) et plus encore le maintien d'une bande fleurie (bande de 7 m alternée non fauchée à chaque coupe) s'avèrent significativement favorables à la richesse spécifique (31 espèces sur 43 observées, contre 15 dans et en bordure de champs de céréales) et à l'abondance des papillons (53 ± 6 papillons par 10 minutes de comptage dans la bande non fauchée, contre 15 ± 2 en bordure des parcelles de luzerne témoins et 6 ± 1 en bordure des champs de céréales) ; les espèces les plus abondantes étaient Vanessa cardui (première position étonnante liée aux migrations massives et exceptionnelles de 2009, avec une concentration particulière sur les luzernes), Pieris rapae, Polyommatus icarus, Colias croceus, Pieris brassicae, Aglais io et Pieris napi. Plus les espèces sont communes, plus elles semblent favorisées par ces floraisons de luzerne. L'état de floraison de la luzerne est un paramètre essentiel, surtout en deuxième moitié de saison, lorsque les fleurs sauvages sont moins nombreuses. Il ressort un intérêt supplémentaire des bandes non fauchées de luzerne pour les espèces comme P. icarus (sédentaire) et C. croceus (migrateur) dont les chenilles peuvent se nourrir de luzerne

Forecasting the Brazilian yield curve using forward-looking variables

This paper proposes a forecasting model that combines a factor augmented VAR (FAVAR) methodology with the Nelson and Siegel (NS) parametrization of the yield curve in order to predict the Brazilian term structure of interest rates. Importantly, we extract the principal components for the FAVAR from a large data set containing a range of forward-looking macroeconomic and financial variables. Our forecasting model improves on the predictive accuracy of extant models in the literature significantly, particularly at short-term horizons. For instance, the mean absolute forecast errors are 15–40% lower than those of the random walk benchmark on predictions at the three-month horizon. The out-of-sample analysis shows that the inclusion of forward-looking indicators is the key to improving the predictive ability of the model

Securities Lending and Short Selling

Purpose – The aim of this study is to offer the current view on the subject, placing emphasis on studies that use Brazilian data and that could motivate new research. Design/methodology/approach –A bibliographic review of related studies and a secondary database. Findings – The contribution is to introduce this topic for the academic community in Brazil. We also present the main descriptive information for this market and its economic and policy implications. Originality/value – We contribute to the literature by summarizing the main works in the field, focusing on the Brazilian market, which has very detailed data and great potential for further studies

A microsatellite marker for yellow rust resistance in wheat

Bulk segregant analysis (BSA) was used to identify molecular markers associated with yellow rust disease resistance in wheat (Triticum aestivum L.). DNAs isolated from the selected yellow rust tolerant and susceptible F-2 individuals derived from a cross between yellow rust resistant and susceptible wheat genotypes were used to established a "tolerant" and a "susceptible" DNA pool. The BSA was then performed on these DNA pools using 230 markers that were previously mapped onto the individual wheat chromosomes. One of the SSR markers (Xgwm382) located on chromosome group 2 (A, B, D genomes) was present in the resistant parent and the resistant bulk but not in the susceptible parent and the susceptible bulk, suggesting that this marker is linked to a yellow rust resistance gene. The presence of Xgwm382 was also tested in 108 additional wheat genotypes differing in yellow rust resistance. This analysis showed that 81% of the wheat genotypes known to be yellow rust resistant had the Xgwm382 marker, further suggesting that the presence of this marker correlates with yellow rust resistance in diverse wheat germplasm. Therefore, Xgwm382 could be useful for marker assisted selection of yellow rust resistances genotypes in wheat breeding programs

Anti-Apoptotic Machinery Protects the Necrotrophic Fungus Botrytis cinerea from Host-Induced Apoptotic-Like Cell Death during Plant Infection

Necrotrophic fungi are unable to occupy living plant cells. How such pathogens survive first contact with living host tissue and initiate infection is therefore unclear. Here, we show that the necrotrophic grey mold fungus Botrytis cinerea undergoes massive apoptotic-like programmed cell death (PCD) following germination on the host plant. Manipulation of an anti-apoptotic gene BcBIR1 modified fungal response to PCD-inducing conditions. As a consequence, strains with reduced sensitivity to PCD were hyper virulent, while strains in which PCD was over-stimulated showed reduced pathogenicity. Similarly, reduced levels of PCD in the fungus were recorded following infection of Arabidopsis mutants that show enhanced susceptibility to B. cinerea. When considered together, these results suggest that Botrytis PCD machinery is targeted by plant defense molecules, and that the fungal anti-apoptotic machinery is essential for overcoming this host-induced PCD and hence, for establishment of infection. As such, fungal PCD machinery represents a novel target for fungicides and antifungal drugs

Seed-Derived Ethylene Facilitates Colonization but Not Aflatoxin Production by Aspergillus flavus in Maize

Ethylene (ET) emitted by plant tissues has been broadly reported to play important roles in plant development, response to environmental stresses and defense against certain pathogens. Recent evidence obtained from using in vitro fungal cultures exposed to ET suggested that exogenous ET may regulate the production of aflatoxin by Aspergilli. However, the function of endogenous, seed-derived ET has not been explored. In this study, we found that the maize lipoxygenase lox3 mutant, previously reported to be susceptible to Aspergillus spp., emitted greater levels of ET upon A. flavus infection, suggesting the potential involvement of endogenous ET in the susceptibility of maize to A. flavus. Supporting this idea, both colonization and conidiation of A. flavus were reduced in wild-type (WT) kernels treated with AgNO(3), an ET synthesis inhibitor. There was no ET emission from non-viable kernels colonized by A. flavus, suggesting that living seed but not the fungus itself was the primary source of ET released upon infection with A. flavus. The kernels of acs2 and acs6, two ET biosynthetic mutants carrying Mutator transposons in the ACC synthase genes, ACS2 and ACS6, respectively, displayed enhanced seed colonization and conidiation, but not the levels of aflatoxin, upon infection with A. flavus. Surprisingly, both acs2 and acs6 mutant kernels emitted greater levels of ET in response to infection by A. flavus as compared with WT seed. The increased ET in single mutants was found to be due to overexpression of functional ACS genes in response to A. flavus infection. Collectively, these findings suggested that ET emitted by infected seed facilitates colonization by A. flavus but not aflatoxin production