Optimal dividend and capital structure with debt covenants

We consider an optimal dividend and capital structure problem for a firm which holds a certain amount of debt to which is associated a financial-ratio covenant between the creditors and the firm. We study optimal policies under a bankruptcy framework using a mixed reduced and structural approach in modelling default and liquidation times. Once in default, the firm is given a grace period during which it may inject more capital to correct the situation. The firm is liquidated if, by the end of the grace period, assets do not exceed the debt. Under this setup, we maximize the discounted amount of dividends distributed minus the capital injected up to the time of bankruptcy. It gives rise to a two-dimensional singular control problem leading to a non-standard system of variational inequalities. Beyond the usual viscosity characterization, we completely solve this problem and obtain a description of the continuation, dividend and capital injection regions enabling us to fully characterize the optimal policies. We conclude the paper with numerical results and illustrations

Brugada Type 1 Pattern and Risk Stratification for Sudden Death: Does the Key Hide in the ECG Analysis?

Primary prevention of ventricular fibrillation is at the heart of the management of Brugada syndrome. Several recent studies have shown that the analysis of simple electrocardiographic criteria could help to stratify the risk of sudden death. In the present work, 12 markers were studied: spontaneous and permanent type 1 pattern, first-degree atrioventricular block, sinus node dysfunction, wide QRS in V2, aVR sign, fragmented QRS, S-waves in DI, early repolarization pattern, atrial fibrillation, type 1 in peripheral leads pattern, and long Tpeak-Tend interval. These electrical markers reflect abnormalities in conduction, depolarization, and repolarization that may indicate the severity of the disease. In this chapter, we carry out a review of these markers, their method of determination on the surface ECG, and the main studies highlighting their prognostic impact. We also review the main underlying pathophysiological hypotheses of Brugada syndrome

Structural transformations of bioactive glass 45S5next term with thermal treatments

International audienceWe report on the structural transformations of Bioglass® during thermal treatments. Just after the glassy transition, at 550 °C, a glassy phase separation occurs at 580 °C, with the appearance of one silicate- and one phosphate-rich phase. It is followed by the crystallization of the major phase Na2CaSi2O6, from 610 to 700 °C and of the secondary phase, silico-rhenanite, at 800 °C. The latter evolves from the phosphate-rich glassy phase, which is still present after the first crystallization. In order to control the processing of glass-ceramic products from Bioglass®, crystallization kinetics were studied via differential scanning calorimetry measurements in the range of 620–700 °C and temperature–time–transformation curves were established

Influence of substrate types and morphological traits on movement behavior in a toad and newt species

Background Inter-patch movements may lead to genetic mixing, decreasing both inbreeding and population extinction risks, and is hence a crucial aspect of amphibian meta-population dynamics. Traveling through heterogeneous landscapes might be particularly risky for amphibians. Understanding how these species perceive their environment and how they move in heterogeneous habitats is an essential step in explaining metapopulation dynamics and can be important for predicting species’ responses to climate change and for conservation policy and management. Methods Using an experimental approach, the present study focused on the movement behavior (crossing speed and number of stops) on different substrates mimicking landscape components (human-made and natural substrates) in two amphibian species contrasting in locomotion mode: the common toad (Bufo bufo), a hopping and burrowing anuran and the marbled newt (Triturus marmoratus), a walking salamander. We tested the hypothesis that species reaction to substrate is dependent on specific ecological requirements or locomotion modes because of morphological and behavioral differences. Results In both species, substrate type influenced individual crossing speed, with individuals moving faster on soil than on concrete substrate. We also demonstrated that long-legged individuals moved faster than individuals with short legs. In both species, the number of stops was higher in females than in males. In common toads, the number of stops did not vary between substrates tested, whereas in marbled newts the number of stops was higher on concrete than on soil substrate. Discussion We highlighted that concrete substrate (mimicking roads) negatively affect the crossing speed of both studied species, with an effect potentially higher in marbled newts. Our findings corroborate negative effects of such heterogeneous landscapes on movement behavior of two amphibian species, which may have implications for the dynamics of metapopulations

An improved whole life cycle culture protocol for the hydrozoan genetic model Clytia hemisphaerica

The jellyfish species Clytia hemisphaerica (Cnidaria, Hydrozoa) has emerged as a new experimental model animal in the last decade. Favorable characteristics include a fully transparent body suitable for microscopy, daily gamete production and a relatively short life cycle. Furthermore, whole genome sequence assembly and efficient gene editing techniques using CRISPR/Cas9 have opened new possibilities for genetic studies. The quasi-immortal vegetatively-growing polyp colony stage provides a practical means to maintain mutant strains. In the context of developing Clytia as a genetic model, we report here an improved whole life cycle culture method including an aquarium tank system designed for culture of the tiny jellyfish form. We have compared different feeding regimes using Artemia larvae as food and demonstrate that the stage-dependent feeding control is the key for rapid and reliable medusa and polyp rearing. Metamorphosis of the planula larvae into a polyp colony can be induced efficiently using a new synthetic peptide. The optimized procedures detailed here make it practical to generate genetically modified Clytia strains and to maintain their whole life cycle in the laboratory