Existence of financial equilibria with restricted participation

We consider a two-date model of a financial exchange economy with finitely many agents having nonordered preferences and portfolio constraints. There is a market for physical commodities at any state today or tomorrow and financial transfers across time and across states are allowed by means of finitely many nominal assets or num´eraire assets. We prove a general existence result of equilibria for such a financial exchange economy in which portfolios are defined by linear constraints, extending the framework of linear equality constraints by Balasko et al. (1990), and the existence results in the unconstrained case by Cass (1984, 2006), Werner (1985), Duffie (1987), and Geanakoplos and Polemarchakis (1986). Our main result is a consequence of an auxiliary result, also of interest for itself, in which agents’ portfolio constraints are defined by general closed convex sets and the financial structure is assumed to satisfy a ”nonredundancy-type” assumption, weaker than the ones in Radner (1972) and Siconolfi (1989).Restricted participation, portfolio constraints, financial exchange economy, equilibrium, existence, arbitrage-free asset prices

Existence of financial equilibria with restricted participation

We consider a two-date model of a financial exchange economy with finitely many agents having nonordered preferences and portfolio constraints. There is a market for physical commodities at any state today or tomorrow and financial transfers across time and across states are allowed by means of finitely many nominal assets or numeraire assets. We prove a general existence result of equilibria for such a financial exchange economy in which portfolios are defined by linear constraints, extending the framework of linear equality constraints by Balasko et al. (1990) and the existence results in the unconstrained case by Cass (1984, 2006), Werner (1985), Duffie (1987) and Geanakoplos and Polemarchakis (1986). Our main result is a consequence of an auxiliary result, also of interest for itself, in which agents' portofolio constraints are defined by general closed convex sets and the financial structure is assumed to satisfy a "nonredundancy-type" assumption, weaker than the ones in Radner (1972) and Siconolfi (1989).Restricted participation; portfolio constraints; financial exchange economy; equilibrium; existence; arbitrage-free asset prices

Symbiotic performance of Medicago ciliaris lines in association with different Sinorhizobium strains

We analyzed nodulation and nitrogen fixation efficiency for seven lines of Medicago ciliaris in association with two references strains of Sinorhizobium medicae (M104) and S. meliloti (RCR2011). These M. ciliaris lines were collected in Northern-East (Enfidha and Soliman) and Western (Rhayet and Mateur) Tunisian areas. The M. truncatula reference line Jemalong A17 (JA17) was also included. Plants were harvested after a culture period of 60 days. Two quantitative traits were measured at the harvest including the mean number of nodules per plant and the aerial dry weight (ADW). Analysis of variance showed that nodulation and nitrogen fixation efficiency (NFE) were dependent on the effects of line, strain and their interaction. The highest levels were observed for strain (45.07%) and line (53.24%) effects, respectively, for nodulation and NFE. While studied lines showed generally more number of nodules with RCR2011, they were more efficient with M104 strain. No significant difference in number of nodules was detected between M. ciliaris lines and JA17 with M104, whereas RCR2011 was generally most infective with JA17. Overall, JA17 line exhibited the largest NFE with both strains. Furthermore, there was no significant (P>0.05) correlation between nodulation and NFE for M. ciliaris line by strain associations

Financial Economies With Restricted Participation

An abundant literature is concerned with the existence of equilibrium in incomplete markets where participation to financial markets is not restricted. To mention a few, Cass (1984), Werner (1985), Geanakoplos and Polemarchakis (1986), Duffie (1987), Duffie and Shafer (1985) and Magill and Quinzii (1996). Financial economies with incomplete markets assume (in general) a symmetric participation structure, i.e. each consumer is confronted with the same restrictions on her portfolio trades. This is a very limiting assumption: in reality, people get to know about different investment opportunities and not all investors are able to trade in the same markets. In this work we consider institutional restrictions on trading activity in the financial markets. Following Siconolfi (1989), Angeloni and Cornet (2006), and Hahn and Won (2007), the broadest formulation of such restricted participation is to assume that households face financial constraints modeled by closed convex subsets of the portfolio space. Our contribution to the literature on general equilibrium of financial markets is threefold. In Chapter 2 we refine the definition of reduced financial structure to accommodate the case of financial structures with restricted participation. We then provide a characterization of reduced financial structures in terms of arbitrage-free prices and by the compactness of a set of ``admissible'' portfolio allocations. In Chapter 3 we introduce an equivalence relation on the set of financial structures and we show that, under mild assumptions, every financial structure is equivalent to a reduced financial structure, and that subsequently, all equilibria in a financial economy are in one-to-one correspondence with the equilibria of an economy where the financial structure is replaced by an equivalent reduced one. Finally, in Chapter 4 we prove a general existence result of equilibria for financial exchange economies with restricted participation in which agents may have nonordered preferences. Our result extends the results by Radner (1972), and Siconolfi (1989), and also extends to the restricted participation case the results by Cass (1984), Werner (1985), and Duffie (1987)

Variability salt stress response analysis of Tunisian natural populations of Medicago truncatula (Fabaceae) using salt response index (SRI) ratio

We evaluated the responses to salt stress of 106 Medicago truncatula lines from 11 Tunisian natural populations collected from areas that varied in soil composition, salinity and water availability. Five references lines were also included in this study. Plants were cultivated in two treatments (0 and 50 mM of NaCl) during a period of 60 days. At harvest, we measured 14 quantitative traits of the aerial and root growth to identify genotypic variability in salt response. Analysis of variance showed that, the response to salt lines within populations was dependent on the effects of treatment, population, line within population and their interaction with maximum value recorded for treatment (93.78%). This study also analyzed heritability of the salt response index (SRI), defined as the ratio between the observed values with and without salt treatment. SRI of most measured traits had high broad-sense heritability (H²). Most of established correlations among SRI values of measured traits were positive. SRI means revealed that, Soliman and Bulla Regia are the most salt-tolerant populations. Based on Ward’s estimated distance, all lines were classified into 4 clusters showing similarity and dissimilarity in response to salt stress. The eco-geographical factors that influence more the variation of SRI of measured traits among populations are assimilated P2O5, % organic matter and carbon and mean annual rainfall. Findings from this study will provide the basis for identifying and breeding of salt-tolerant lines in M. truncatula.Key words: Environmental factors, lines, Medicago truncatula, NaCl stress, populations, quantitative traits

Optical-fiber-microsphere for remote fluorescence correlation spectroscopy

International audienceFluorescence correlation spectroscopy (FCS) is a versatile method that would greatly benefit to remote optical-fiber fluorescence sensors. However, the current state-of-the-art struggles with high background and low detection sensitivities that prevent the extension of fiber-based FCS down to the single-molecule level. Here we report the use of an optical fiber combined with a latex microsphere to perform FCS analysis. The sensitivity of the technique is demonstrated at the single molecule level thanks to a photonic nanojet effect. This offers new opportunities for reducing the bulky microscope setup and extending FCS to remote or in vivo applications

Genetic diversity and salt tolerance of bacterial communities from two Tunisian soils

Microbial ecology studies on arid soils are particularly important for the analysis of biological functions during desertification. Although much is known about the arid saline flora, few researches have directly compared the bacterial communities of saline arid soils with cultivated soils in Northern Africa. Bacterial communities present in two soils from Soliman (north of Tunisia), one salty and neglected, and the other cultivated, were investigated by using both cultivation dependent and independent approaches. The first approach was used to assess the presence of salt tolerant bacteria and the relationships among salt (NaCl) resistance phenotype, soil characteristics and phylogenetic assignment of strains. Total community analysis, performed by T-RFLP on total DNA, was carried out to investigate the relationships between total community fingerprinting with cultivated isolates diversity. The cultivated isolates from salty soil were more genetically diverse, harbouring strains that can grow at high salt concentration. Moreover, the salt resistance of isolates was found not to be related to any particular phylogenetic group, being widespread among isolates belonging to different bacterial subdivisions. Ribotype richness, evaluated as number of different T-RFLP bands (TRFs), was shown to be higher in the agricultural soil than in the salty soil and several agricultural soil-specific TRFs were detected