Accelerated storage testing of freeze-drying Pseudomonas fluorescens BTP1, BB2 and PI9 strains

in African Journal of Biotechnology (2012), 11

Freeze-dried cultures of P.fluorescens are used in agriculture and microbiological industry. However, P. fluorescens is very susceptible to damage during freeze-drying and subsequent storage and it would ... [more ▼]

Freeze-dried cultures of P.fluorescens are used in agriculture and microbiological industry. However, P. fluorescens is very susceptible to damage during freeze-drying and subsequent storage and it would be useful to increase culture viability during storage. The viability of freeze-dried P. fluorescens strains (BTP1, PI9 and BB2) was evaluated by using the Arrhenius model. This model was described by measuring of reaction rate constants (D or k) and temperature sensitivity of rate constant (z or Ea). The freeze-dried P.fluorescens strains was stored in glass tubes at 60°C, 37°C and 4°C for 8 h, 28 days and 2 months, respectively. D value decreased or k increased with an increase of the storage temperature. By comparing their decimal reduction time (D), we observed that BB2 strain was more resistant than BTP1 and PI9 at 37 °C and 60 °C. The activation energy of all P. fluorescens strains are not significantly different and thermal inactivation may occur by the same mechanism. Thus it was possible to compare rate constants of survival for the freeze-dried P. fluorescens strains. These results will be useful to the development of improved reference materials and samples held in culture collections. [less ▲]

A study of Electra posidoniae Gautier (Cheleistomata, Anasca), a bryozoan strictly found as epiphyte of the seagrass Posidonia oceanica (L.) Delile.

Poster (2012, November 26)

Species living as epiphytes of marine macrophytes have often important role in ecosystem functioning, such as food web suppliers. Some animal or algae species may be considered as really specialised in ... [more ▼]

Species living as epiphytes of marine macrophytes have often important role in ecosystem functioning, such as food web suppliers. Some animal or algae species may be considered as really specialised in the colonization of plant substrate and often dominates epiphytic community, particularly, on long life-span seagrass and macroalgae species. Because epiphytic compartment dysfunction is often implied in seagrass human-induced declining, it is important to understand dynamics and life traits of its specific component in pristine area. In our study, colonization dynamics, biomass seasonality, diet composition of Electra posidoniae, an epiphytic bryozoa, strictly found on the leaves of the seagrass Posidonia oceanica and dominating the leaf epifauna, were assessed monthly at 10 metre depth in the Revellata Bay (Corsica, Mediterranean sea). Aiming to delineate their trophic role in the ecosystem, we have performed bulk stable isotopes measurements and gut content analysis. [less ▲]

A brief review of auroral emissions of the outer planets

Conference (2012, November 26)

Comparison Between Mornigstar Ratings And Traditional Performance Measures Ratings

E-print/Working paper (2012)

In this paper, we compare Morningstar ratings with those obtained using the same methodology of rating attribution with a set of commonly used performance measures. We look at three types of investment ... [more ▼]

In this paper, we compare Morningstar ratings with those obtained using the same methodology of rating attribution with a set of commonly used performance measures. We look at three types of investment horizons: 3-year, 5-year and 10-year ratings. Our analysis focuses on Open-End US Mutual Funds available in Morningstar Direct Database from which we create three sets of 16,617, 13,505 and 7,992 funds corresponding respectively to the three investment horizons analyzed. Our results show that Morningstar ratings are very close (correlation around 80%) to ratings obtained with Sharpe’s alpha, Jensen’s alpha, Four-factor alpha and Excess returns. And less significantly, we also observe that ratings given by the Sortino ratio, Sharpe MVaR, M-squared, Sharpe ratio, One-factor information ratio, Four-factor information ratio, Prospect ratio and Stutzer index are quite similar to Morningstar’s ratings (correlation lying between 70% and 78%). At the other end of the spectrum, however, ratings obtained with Annual return diverge widely from Morningstar ratings. We also analyse which explanatory variables can explain the differences between ratings computed with Morningstar as compared with the alternative performance measures using a probit regression. We find that Load adjustments, tax and risk included by Morningstar in the computation of MRAR are often determining. Expense ratio, Return Skewness and the three factors of the Fama-French model (Beta, Size load and Book-to-market loading) can be significant determinants depending on the performance measure analyzed and on the selected investment horizon. Fund characteristics such as Age, Fund size, Turnover rate and Manager tenure are not statistically significant in determining the differences in ratings. Besides, we analyze differences between ratings (in terms of number of STARs) and we confirm previous results (i.e. the link between Morningstar’s and the alternative performance measures, but also the explanatory capacity of the load for lots of differences between ratings). Finally, we test all possible combinations of our set of performance measures, and observe that Sharpe’s alpha, excess return, Sharpe MVaR, Four-factor alpha and Jensen’s alpha are part of the best combinations. As a conclusion, Morningstar ratings can be replicated using simple and traditional performance measures but the replication is less accurate when tax and loads features are important. Therefore, Morningstar data management and access bring the most of its ratings’ value added. [less ▲]

The nuclear physics of OHe

in Mankoc (Ed.) Proceedings of the 15th Bled Workshop "What Comes Beyond the Standard Models" (2012, November 24)

A recent composite-dark-matter scenario assumes that the dominant fraction of dark matter consists of O-helium (OHe) dark atoms, in which a lepton-like doubly charged particle O is bound with a primordial ... [more ▼]

A recent composite-dark-matter scenario assumes that the dominant fraction of dark matter consists of O-helium (OHe) dark atoms, in which a lepton-like doubly charged particle O is bound with a primordial helium nucleus. It liberates the physics of dark matter from unknown features of new physics, but it demands a deep understanding of the details of known nuclear and atomic physics, which are still unclear. Here, we consider in detail the physics of the binding of OHe to various nuclei of interest for direct dark matter searches. We show that standard quantum mechanics leads to bound states in the keV region, but does not seem to provide a simple mechanism that stabilizes them. The crucial role of a barrier in the OHe-nucleus potential is confirmed for such a stabilization. [less ▲]

FORMATION: "La mesure de l'efficacité de la prise en charge neuropsychologique. Pourquoi mesurer et comment faire?"

Conference (2012, November 24)

Integration/blending of external information into genetic/genomic evaluations

Diverse speeche and writing (2012)

Mechanical Processes of a Single Synthetic Molecular Machine Studied by AFM-based Force Spectroscopy

Doctoral thesis (2012)

Some biomolecules are able to generate directional forces by rectifying random thermal motions. This allows these molecular machines to perform mechanical tasks such as intracellular cargo transport or ... [more ▼]

Some biomolecules are able to generate directional forces by rectifying random thermal motions. This allows these molecular machines to perform mechanical tasks such as intracellular cargo transport or muscle contraction in plants and animals. Although some artificial molecular machines have been synthesized and used collectively to perform mechanical tasks, so far there have been no direct measurements of mechanical processes at the single-molecule level. Here we report measurements of the mechanical work performed by a synthetic molecule less than 5 nm long. We show that biased Brownian motion of the submolecular components in a hydrogen-bonded [2]rotaxane -a molecular ring threaded onto a molecular axle- can be harnessed to generate significant directional forces. We used the cantilever of an atomic force microscope to apply a mechanical load to the ring during single-molecule pulling-relaxing cycles. The ring was pulled along the axle, away from the thermodynamically favoured binding site, and was then found to travel back to this site against an external load of 30 pN. Using fluctuation theorems, we were able to relate the measurements of the work done at the level of individual molecules to the free energy change measured previously by ensemble measurements. Finally, we used dynamic single-molecule force spectroscopy to probe kinetic information of the interaction between the molecular ring and the preferred binding site. The results also demonstrate that AFM-based single-molecule force spectroscopy, which has been widely used to investigate the mechanochemical behaviour of (bio)macromolecules, can be applied to a molecule that is less than 5 nm in its extended form. [less ▲]

Intervention dans le cadre du Workshop Studien zur Struktur des Bewusstseins

Conference (2012, November 23)

Usages politiques du temps et visions de l'avenir, quelles conséquences sur l'action publique liée aux changements climatiques? Analyse de contenu sur plusieurs échelles politiques

Conference (2012, November 22)