1,721,620 research outputs found
Portfolio Selection with Transaction Costs and Default Risk
No full textPurpose: The purpose of this paper is to investigate the effect of default risk and transaction costs on the investor's asset allocation and the liquidity premium. More precisely, it aims at answering the following question: can default risk generate a first-order effect on the investor's asset allocation and a liquidity premium of the same order of magnitude as transaction costs?
Design/methodology/approach: The author proposes a very simple consumption-investment model in which an infinitely-lived investor allocates her wealth between a risky asset and a riskless security, and incurs in proportional transaction costs when exchanging them. In addition, the risky asset
may default at some random time, thus reducing the available wealth of the agent. Two different scenarios of default risk are considered. In the total default scenario, the value of the risky asset drops to zero when default occurs whereas, in the partial default case, the proceeds from the liquidation of the risky asset amount to 50% of its value.
Findings: The paper shows that default risk can generate a first-order effect on the investor's asset allocation. On the contrary, the liquidity premium is one order of magnitude smaller than the transaction costs, implying that the additional source of risk determined by the possibility of default is not able to generate a first-order effect on asset pricing.
Originality/value: To the author knowledge, this is the first paper that investigates the interaction of default risk and transaction costs on the investor's asset allocation and its effects on the liquidity premium
Microbial biocontrol agents: developing effective biopesticides
No full textThe negative impact of chemical pesticides on human wellbeing and the environment has encouraged the development of eco-friendly alternatives for the management of plant pathogens. However, only a small number of microbial biocontrol agents (mBCAs) have been developed, registered and used in the management of plant diseases. This book analyses the deployment of mBCAs for the development of novel microbial biopesticides, considering the main plant-beneficial traits, procedures needed for effective formulations and the processes used for their validation. To guide the readers through the world of microbial biopesticides, the book starts with a chapter dedicated to the regulations that need to be followed for the development of final products. Readers will understand the importance of formulation and mode of action of mBCAs in developing microbial biopesticides. They will become familiar with key mBCAs such as Ampelomyces quisqualis, Bacillus spp., Trichoderma spp., and Pseudomonas spp., understanding the importance of formulation for their application in the field. This book explains the use of mBCAs to control post-harvest diseases and the potential of endophytic microorganisms as next-generation microbial biopesticides. A final chapter provides a useful workflow for the selection of new mBCAs and describes microbial species including promising mBCAs that might be developed as new microbial biopesticide
Key impact of an uncommon plasmid on bacillus amyloliquefaciens subsp. plantarum S499 developmental traits and lipopeptide production
Full text linkpeer reviewedThe rhizobacterium Bacillus amyloliquefaciens subsp. plantarum S499 (S499) is particularly efficient in terms of the production of cyclic lipopeptides, which are responsible for the high level of plant disease protection provided by this strain. Sequencing of the S499 genome has highlighted genetic differences and similarities with the closely related rhizobacterium B. amyloliquefaciens subsp. plantarum FZB42 (FZB42). More specifically, a rare 8008 bp plasmid (pS499) harboring a rap-phr cassette constitutes a major distinctive element between S499 and FZB42. By curing this plasmid, we demonstrated that its presence is crucial for preserving the typical physiology of S499 cells. Indeed, the growth rate and extracellular proteolytic activity were significantly affected in the cured strain (S499 P-). Furthermore, pS499 made a significant contribution to the regulation of cyclic lipopeptide production. Surfactins and fengycins were produced in higher quantities by S499 P-, whereas lower amounts of iturins were detected. In line with the increase in surfactin release, bacterial motility improved after curing, whereas the ability to form biofilm was reduced in vitro. The antagonistic effect against phytopathogenic fungi was also limited for S499 P-, most probably due to the reduction of iturin production. With the exception of this last aspect, S499 P- behavior fell between that of S499 and FZB42, suggesting a role for the plasmid in shaping some of the phenotypic differences observed in the two strains. © 2017 Molinatto, Franzil, Steels, Puopolo, Pertot and Ongena
Variation of seasonal mean ratings from the overall sample mean ratings for Paul Puopolo and Ben Jacobs.
No full textVariation of seasonal mean ratings from the overall sample mean ratings for Paul Puopolo and Ben Jacobs.</p
Functional heterogeneity of periglomerular cells in the rat olfactory bulb
No full textThe periglomerular cells of the rat olfactory bulb, a virtually unknown population of interneurons, have been studied applying the whole-cell patch-clamp technique to thin slices. A prominent result, obtained under current-clamp conditions, is that these cells appear to be functionally heterogeneous, and show distinct excitability profiles. Voltage-clamp analysis allows the identification of the ionic basis of these differences and suggests a division into at least two classes, based on the characteristics of the K+ conductances. The first group displays two K+ conductances (delayed rectifier, gKV, and fast transient, gA) of similar amplitude, and under current-clamp conditions shows the usual outward rectifying behaviour at depolarized potentials. The second group has a large gA, and a small or absent gKV. Consequently, following sustained depolarizations under current-clamp conditions leading to inactivation of gA, these neurons do not show any sign of outward rectification and behave as ohmic elements, as normally observed only at hyperpolarized potentials. The transition ion zinc (10-300 microM) affects gA but not gKV The inactivation process (steady-state curve and rate constant) is strongly altered by Zn2+, the activation process less so; open-channel conductance is not affected. The Zn2+ effect is unlikely to be due to surface charge screening or to a mechanism involving channel block. In view of the substantial presence of zinc ions in the olfactory nerve terminals, its actions on the A-current could be of some relevance for physiological function
Returns Volatility and Correlation in Asset Pricing: A Review
No full textIn this paper we provide a survey of the role of equity returns volatility and correlation within the asset pricing literature. In general, the literature of the second moments of stock returns can be classified in three main “phases”. In the first one, which started with the pioneering work of Markowitz (1952, 1959) and (building on this) culminated in what has come to be known as the Capital Asset Pricing Model (CAPM), variances and covariances were assumed to be constant over time. Only at the beginning of the '80s, and in particular with the leading contribution of Engle (1982), a new generation of approaches appeared. This literature abandoned the hypothesis of constant volatility and modeled the variance of the current error term to be a function of the variances of the previous time-period's error terms. However, in this “phase”, multivariate ARCH (GARCH) models were either assuming that equity correlations are constant over time or specifying the covariance term as a unique unknown, without differentiating the several components of the covariance matrix. Only in more recent years (the third “phase”), the asset pricing literature, recognizing that stock returns correlations are not stable over time but fluctuate dramatically, started separating volatility shocks from correlation shocks
Pseudomonas chlororaphis metabolites as biocontrol promoters of plant health and improved crop yield
No full textThe Pseudomonas fluorescens complex contains at least eight phylogenetic groups and each of these includes several bacterial species sharing ecological and physiological traits. Pseudomonas chlororaphis classified in a separate group is represented by three different subspecies that show distinctive traits exploitable for phytostimulation and biocontrol of phytopathogens. The high level of microbial competitiveness in soil as well as the effectiveness in controlling several plant pathogens and pests can be related to the P. chlororaphis ability to implement different stimulating and toxic mechanisms in its interaction with plants and the other micro- and macroorganisms. Pseudomonas chlororaphis strains produce antibiotics, such as phenazines, pyrrolnitrine, 2-hexyl, 5-propyl resorcinol and hydrogen cyanide, siderophores such as pyoverdine and achromobactine and a complex blend of volatile organic compounds (VOCs) that effectively contribute to the control of several plant pathogens, nematodes and insects. Phenazines and some VOCs are also involved in the induction of systemic resistance in plants. This complex set of beneficial strategies explains the high increasing interest in P. chlororaphis for commercial and biotechnological applications. The aim of this review is to highlight the role of the different mechanisms involved in the biocontrol activity of P. chlororaphis strains
Sodium current in periglomerular cells of rat olfactory bulb in vitro
No full textThe capacity of periglomerular cells (PGc) to give fast, Na-dependent action potentials is a crucial and debated issue for the comprehension of how sensory information is processed in the olfactory bulb (OB). Using patchclamp whole cell recording in thin slices of rat OB (P8-P20) we showed that fast sodium conductance is present in all the PGc studied, that this current is sufficiently large to generate action potentials and that action potentials can be evoked in these cells by direct stimulation of the olfactory nerve. A comprehensive kinetic characterization of INa is also presented
The biocontrol agent Pseudomonas chlororaphis subsp. aureofaciens M71 originates natural mutants impaired in the ability to control Fusarium oxysporum f. sp. radicis-lycopersici on tomato
No full textPseudomonas chlororaphis subsp. aureofaciens M71 differentiated three natural mutants distinguishable for morphological traits. P. chlororaphis subsp. aureofaciens M71 mutants were impaired in persisting on tomato roots and controlling tomato crown rot. Mutants were characterised by a reduced ability in production of autoinducer signals and antibiotic
Thermo-Mechanical Properties of Injection Molded Components Manufactured by Engineered Biodegradable Blends
No full textEngineering of ductile, tough and thermal resistant PLA-based materials requires blending of PLA with other constituents by reactive twin-screw co-rotating extrusion to achieve compounds with adequate thermo-mechanical properties. Then, the compound of the polymeric blends must be melt processed to the final shape with an additional technology, namely the injection molding. The two-stage process the polymeric blends must undergo and the different rheological properties the blends must feature to be suitable to the different processing steps make extremely difficult to engineer the material. Extrusion compounding requires high viscous materials low melt flow index (MFI), while injection molding requires materials with low viscosity (high MFI). To overcome these shortcomings, this manuscript deals with the design of novel biodegradable PLA-based blends that rely on mixing PLA grades with different MFI (i.e. very low for extrusion and high for injection molding), each chosen to feature the rheological characteristics needed for each step of the two-stage transformation process. The ratio of the two PLA-grades inside the blends was the matter of the present investigation. The blends were subsequently tested for the manufacturing of single-use biodegradable and thermal resistant injection molded small cups, specifically designed for brewing of hot beverages. Lastly, the thermo-mechanical performance of the as-is and annealed cups were studied. Experimental evidences show blending of two-different grades of PLA is a promising route to formulate low impact polymeric materials suitable for demanding packaging solutions
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