Isolation and characterization of cryotolerant Saccharomyces strains

Cryotolerant Saccharomyces strains were isolated from grape must (Pinot noir) using the enrichment method (CASTELLARI et al. 1992). Eleven cryotolerant strains were collected which all belonged to the S. uvarum species (Melibiose test and karyotype). Fermentations were carried out at 10 and 25 °C, the level of fermentation products was compared with those produced by mesophilic yeasts. Regardless of temperature, cryotolerant yeasts (SY055 and 12233) produced twice as many isobutyl and isoamyl alcohols as mesophilic yeast (FB) and 2-phenethyl alcohol was produced by cryotolerant yeasts at levels 4 times as high as by mesophilic yeasts. The potential of these yeasts for oenological application is discussed

Origin and evolution of surface spin current in topological insulators

The Dirac surface states of topological insulators offer a unique possibility for creating spin polarized charge currents due to the spin-momentum locking. Here we demonstrate that the control over the bulk and surface contribution is crucial to maximize the charge-to-spin conversion efficiency. We observe an enhancement of the spin signal due to surface-dominated spin polarization while freezing out the bulk conductivity in semiconducting Bi1.5Sb0.5Te1.7Se1.3 below 100K. Detailed measurements up to room temperature exhibit a strong reduction of the magnetoresistance signal between 2 and 100K, which we attribute to the thermal excitation of bulk carriers and to the electron-phonon coupling in the surface states. The presence and dominance of this effect up to room temperature is promising for spintronic science and technology

Predicting drought and subsidence risks in France

The economic consequences of drought episodes are increasingly important although they are often difficult to apprehend, in part because of the complexity of the underlying mechanisms. In this article we will study one of the consequences of drought, namely the risk of subsidence (or more specifically clay-shrinkage-induced subsidence), for which insurance has been mandatory in France for several decades. Using data obtained from several insurers, representing about a quarter of the household insurance market over the past 20 years, we propose some statistical models to predict not only the frequency but also the intensity of these droughts for insurers. But even if we use more advanced models than standard regression-type models (here random forests to capture non-linearity and cross effects) and all geophysical and climatic information is available, it is still difficult to predict the economic cost of subsidence claims.</p

C-terminal phosphorylation of NaV1.5 impairs FGF13-dependent regulation of channel inactivation

International audienceVoltage-gated Na(+) (NaV) channels are key regulators of myocardial excitability, and Ca(2+)/calmodulin-dependent protein kinase II (CaMKII)-dependent alterations in NaV1.5 channel inactivation are emerging as a critical determinant of arrhythmias in heart failure. However, the global native phosphorylation pattern of NaV1.5 subunits associated with these arrhythmogenic disorders and the associated channel regulatory defects remain unknown. Here, we undertook phosphoproteomic analyses to identify and quantify in situ the phosphorylation sites in the NaV1.5 proteins purified from adult WT and failing CaMKIIδc-overexpressing (CaMKIIδc-Tg) mouse ventricles. Of 19 native NaV1.5 phosphorylation sites identified, two C-terminal phosphoserines at positions 1938 and 1989 showed increased phosphorylation in the CaMKIIδc-Tg compared with the WT ventricles. We then tested the hypothesis that phosphorylation at these two sites impairs fibroblast growth factor 13 (FGF13)-dependent regulation of NaV1.5 channel inactivation. Whole-cell voltage-clamp analyses in HEK293 cells demonstrated that FGF13 increases NaV1.5 channel availability and decreases late Na(+) current, two effects that were abrogated with NaV1.5 mutants mimicking phosphorylation at both sites. Additional co-immunoprecipitation experiments revealed that FGF13 potentiates the binding of calmodulin to NaV1.5 and that phosphomimetic mutations at both sites decrease the interaction of FGF13 and, consequently, of calmodulin with NaV1.5. Together, we have identified two novel native phosphorylation sites in the C terminus of NaV1.5 that impair FGF13-dependent regulation of channel inactivation and may contribute to CaMKIIδc-dependent arrhythmogenic disorders in failing hearts

Thermal Diffusion of a Two Layer System

In this paper thermal conductivity and thermal diffusivity of a two layer system is examined from the theoretical point of view. We use the one dimensional heat diffusion equation with the appropriate solution in each layer and boundary conditions at the interfaces to calculate the heat transport in this bounded system. We also consider the heat flux at the surface of the samle as boundary condition instead of using a fixed tempertaure. From this, we obtain an expression for the efective thermal diffusivity of the composite sample in terms of the thermal diffusivity of its constituent materials whithout any approximations.Comment: 16 pages, 1 figure, RevTeX v. 3.0 macro packag

Intermediate Tail Dependence: A Review and Some New Results

The concept of intermediate tail dependence is useful if one wants to quantify the degree of positive dependence in the tails when there is no strong evidence of presence of the usual tail dependence. We first review existing studies on intermediate tail dependence, and then we report new results to supplement the review. Intermediate tail dependence for elliptical, extreme value and Archimedean copulas are reviewed and further studied, respectively. For Archimedean copulas, we not only consider the frailty model but also the recently studied scale mixture model; for the latter, conditions leading to upper intermediate tail dependence are presented, and it provides a useful way to simulate copulas with desirable intermediate tail dependence structures.Comment: 25 pages, 1 figur

Carbon cycle during the late Aptian–early Albian OAE 1b: A focus on the Kilian–Paquier levels interval

This is the final version. Available on open access from Elsevier via the DOI in this recordData availability: Data will be made available on request.The Oceanic Anoxic Event (OAE) 1b took place over a protracted time interval during the Aptian/Albian boundary interval, at the dawn of the mid-Cretaceous climatic optimum. OAE 1b is characterized by the occurrence of several sub-events recorded by organic matter-rich levels, which can be traced on regional-to-global scale. Previous studies have highlighted that the climax of the event occurred around the Kilian – Paquier interval, with this latter sub-event being the most extended and pronounced stratigraphic interval. Numerous studies on OAE 1b have however only focused on high-precision investigations of the Kilian and/or Paquier levels, leaving vast uncertainties about the environmental changes and their drivers during the entire OAE 1b, and hence also on the mechanisms leading to the formation of the sub-events themselves. In this study, we have performed a high-resolution multi-proxy analysis of the Briers section, a well-exposed section in the Blue Marls Formation of the SE France Vocontian Basin, continuously covering the Kilian – Paquier interval. Pyrolysis analyses show that most of the organic matter in this section is immature and of continental origin, averaging 1.5% TOC. The Kilian and Paquier levels are characterized by higher TOC values and a substantial increase in the amount of marine organic matter. Comparing TOC values with changes in Al or Ti concentration (proxies for continental weathering) and Hydrogen index (HI values, tracer for the type of organic matter) reveals that the background long-term change in TOC is linked to change in the continental organic matter delivery to the Vocontian Basin tied to changes in continental weathering rates. Sporadic increases in TOC values associated with the Kilian, HN 8, and Paquier levels, are most likely the result of short-lived events of increased marine primary productivity and organic matter preservation superimposed on the background influx of continental organic matter. A high-resolution bulk organic matter carbon isotope record shows that, apart from the Paquier level, all the fluctuations observed in the carbonate carbon isotope ratios are also mirrored in the organic matter record, although with higher amplitudes. This discrepancy in amplitude can be resolved by correcting the bulk organic matter carbon isotope record for fluctuations in the type of organic matter, demonstrating that both oceanic and atmospheric reservoirs were affected by similar carbon isotope fluctuations, which were hence of global extent. The abnormal bulk organic matter carbon isotope record of the Paquier level further confirms the large geographical expansion of unusual organic matter production and/or accumulation during this peculiar event. Overall, this study suggests that Milankovitch-paced (long eccentricity) changes in monsoonal activity and their effect on the accumulation of organic matter in continental wetlands best explains the rhythmic change in the global carbon isotope record across the OAE 1b interval.Aarhus Universitets Forskningsfon

Horizontal DNA transfer mechanisms of bacteria as weapons of intragenomic conflict

Horizontal DNA transfer (HDT) is a pervasive mechanism of diversification in many microbial species, but its primary evolutionary role remains controversial. Much recent research has emphasised the adaptive benefit of acquiring novel DNA, but here we argue instead that intragenomic conflict provides a coherent framework for understanding the evolutionary origins of HDT. To test this hypothesis, we developed a mathematical model of a clonally descended bacterial population undergoing HDT through transmission of mobile genetic elements (MGEs) and genetic transformation. Including the known bias of transformation toward the acquisition of shorter alleles into the model suggested it could be an effective means of counteracting the spread of MGEs. Both constitutive and transient competence for transformation were found to provide an effective defence against parasitic MGEs; transient competence could also be effective at permitting the selective spread of MGEs conferring a benefit on their host bacterium. The coordination of transient competence with cell-cell killing, observed in multiple species, was found to result in synergistic blocking of MGE transmission through releasing genomic DNA for homologous recombination while simultaneously reducing horizontal MGE spread by lowering the local cell density. To evaluate the feasibility of the functions suggested by the modelling analysis, we analysed genomic data from longitudinal sampling of individuals carrying Streptococcus pneumoniae. This revealed the frequent within-host coexistence of clonally descended cells that differed in their MGE infection status, a necessary condition for the proposed mechanism to operate. Additionally, we found multiple examples of MGEs inhibiting transformation through integrative disruption of genes encoding the competence machinery across many species, providing evidence of an ongoing "arms race." Reduced rates of transformation have also been observed in cells infected by MGEs that reduce the concentration of extracellular DNA through secretion of DNases. Simulations predicted that either mechanism of limiting transformation would benefit individual MGEs, but also that this tactic's effectiveness was limited by competition with other MGEs coinfecting the same cell. A further observed behaviour we hypothesised to reduce elimination by transformation was MGE activation when cells become competent. Our model predicted that this response was effective at counteracting transformation independently of competing MGEs. Therefore, this framework is able to explain both common properties of MGEs, and the seemingly paradoxical bacterial behaviours of transformation and cell-cell killing within clonally related populations, as the consequences of intragenomic conflict between self-replicating chromosomes and parasitic MGEs. The antagonistic nature of the different mechanisms of HDT over short timescales means their contribution to bacterial evolution is likely to be substantially greater than previously appreciated