Violation of the Cauchy-Schwarz inequality with matter waves

The Cauchy-Schwarz (CS) inequality -- one of the most widely used and important inequalities in mathematics -- can be formulated as an upper bound to the strength of correlations between classically fluctuating quantities. Quantum mechanical correlations can, however, exceed classical bounds.Here we realize four-wave mixing of atomic matter waves using colliding Bose-Einstein condensates, and demonstrate the violation of a multimode CS inequality for atom number correlations in opposite zones of the collision halo. The correlated atoms have large spatial separations and therefore open new opportunities for extending fundamental quantum-nonlocality tests to ensembles of massive particles.Comment: Final published version (with minor changes). 5 pages, 3 figures, plus Supplementary Materia

Non-enzymatic hydrolysis of fluorescein diacetate (FDA) in a Mediterranean oak (Quercus ilex L.) litter

International audienceWe show the presence of interfering substances when the total microbial activity in litter samples is measured with fluorescein diacetate (FDA), and we propose some methodological modifications to avoid such interference. Three distinct litter layers (the OhLn, the OhLv and the OhLf) of evergreen oak (Quercus ilex L.) were characterized by 13 C CPMAS NMR and the spectra show that the recalcitrant aromatic and phenolic compounds increase with the degree of degradation of litter. A wide range of sources of interference in the hydrolysis of FDA was found. To understand the origin of this interference, sterilized litter materials (i.e. g-irradiated or autoclaved) and a wide range of organic substances (i.e. amino acids, glucose, sorbitol and organic humic acids) were investigated. Insignificant differences on the FDA hydrolysis activity (FDA activity) were found in the g-irradiated and non-irradiated OhLn litter, indicating that g-irradiation does not destroy enzymes. Conversely, after heat-sterilization of litter, samples showed FDA activity corresponding to 60, 34.8 and 30.8% (in the OhLn, the OhLv and the OhLf layers, respectively) of that of control litters. This indicates the presence of non-enzymatic interfering substances in the FDA assays. As the humification and litter depth increased, hydrolysis of FDA due to interferences decreased, indicating degradation and/or chelation of interfering substances. We hypothesize that lysine, arginine, histidine and cysteine are mainly responsible for the hydrolysis of FDA. We suggest that the use of phosphate buffer (50 mM, pH 7.0) with incubation < 30 minutes, in combination with a temperature between 30 and 40°C, produces insignificant interference in the determination of the final FDA activity in litter samples

Does anthracene affect microbial activities and organic matter decomposition ? A comparative study in Pinus halepensis litters from Mediterranean coastal and inland areas

The widespread concern about pollution caused by Polycyclic Aromatic Hydrocarbons (PAHs) raises the question of how they affect soil microbial communities which are potentially involved in the transformation of these pollutants. Using microcosms, we describe the effect of anthracene, a model PAH, on microbial communities inhabiting a Pinus halepensis litter from both coastal (COS) and inland (INL) Mediterranean sites. The microcosms were incubated over 3 months (25 degrees C, 60% WHC) and the effects of anthracene on microbial activities of both litters were monitored. Different enzyme activities (laccase, cellulase, beta-glucosidase and acid phosphatase) and microbial respiration were measured and variations in litter chemical composition over incubation were determined using C-13 Nuclear Magnetic Resonance (NMR) from both sites. Our results show that lignocellulolytic enzymes increased markedly after a 3-month incubation in COS microcosms, especially in the presence of anthracene, whereas INL microcosms were not similarly affected. These results show that anthracene not only has no toxic effect on the microbial activities tested but actually enhances the lignocellulolytic activities of the fungal communities from coastal litters, demonstrating the detoxification potential and resistance of stressed Mediterranean coastal ecosystems

Polycyclic aromatic hydrocarbon transformation with laccases of a white-rot fungus isolated from a Mediterranean schlerophyllous litter

International audienceThis study was conducted to investigate whether a laccase from a white-rot fungus isolated from Mediterranean forest litters was able to oxidise widespread pollutants such as polycyclic aromatic hydrocarbons (PAH). Six different isoforms from the constitutive laccase of Marasmius quercophilus strain19 were revealed using isoelectric focusing. In vitro studies showed that these laccase isoforms were able to transform anthracene and benzo(a)pyrene while naphthalene and phenantrene were not oxidised. This result on PAH transformation is linked to the ionisation potential (IP) of PAH: the laccases under study are able to oxidise PAH with IP b 7.55 eV. 2,2′-azino-bis-3-ehtylbenzothiazoline-6-sulfonicacid (ABTS) and hydroxybenzotriazole (HBT), were also used as mediators: percentages of anthracene and benzo(a)pyrene transformation were higher when ABTS was used and when mediators were pre-oxidised with laccases whatever the mediator used. Moreover, after an eight or fifteen-day culture of strain 19 with anthracene, the percentage of disappearance was 73 and 79% respectively. This study also highlights the fact that ABTS or one of its oxidised form, ABTS radical cation (ABTS U+), can be respectively oxidised or reduced through abiotic reactions. Thus, ABTS, because of its electrochemical characteristics, can hardly be considered as a relevant substrate to measure laccase activities in complex environments such as soils or litters where various abiotic reactions are likely to occur

A method to quantify transesterification activities of lipases in litters

International audienceLipases are glycerol ester hydrolases (EC 3.1.1.3) produced by a wide range of microorganisms. They catalyse the hydrolysis of different esters but this reaction is reversible, depending on the water content of the reaction medium, via esterification and transesterification. The synthetic activity of lipases can be of major importance in natural ecosystems since it can be involved in carbon stockage in soils or litters. Here, the detection of transesterification activities of lipases in litter is reported for the first time. We used two different litters: litter of Quercus pubescens (QP) and litter of both Q. pubescens and Q. ilex. Different pnitrophenyl esters and pentanol were used to test transesterification in a reaction medium with an organic solvent (heptane). We showed that these activities were proportional to the amount of litter, the incubation time and the substrate concentration and that they increased with temperature. Furthermore, the lipases from the litters studied were very thermostable since they were still active after 2 h at 70°C. These activities showed common properties of lipases: the highest activities were obtained with a medium acyl-chain substrate p-nitrophenyl caprylate and transesterification activities were correlated to water activity, a w. The following parameters are recommended to quantify transesterification activities in litter: 10 mM of pnitrophenyl caprylate, 1 g of litter, 500 µL of pentanol, q.s.p. 4 mL of heptane incubated at 30°C for 2 h

5000 years of lacustrine ecosystem changes from Lake Petit (Southern Alps, 2200m a.s.l.) : regime shift and resilience of algal communities

Sediments from Lake Petit (2200m a.s.l., Southern Alps) are particularly relevant for analysis of coupled landscape palaeoecology and palaeolimnology. Diatom assemblages, organic matter composition of sediments (total nitrogen and organic carbon) and Pediastrum boryanum concentrations were obtained from a 144-cm-long core, enabling the reconstruction of the aquatic ecosystem over nearly the last 5000 cal. BP. From 4800 to 4300 cal. BP, Lake Petit was a stable diatom-productive water body dominated by alkaliphilous diatoms (Staurosirella pinnata). During this period, nutrients and cations were supplied by the chemical weathering of podzols that developed under conifer woodlands. This overall stability was suddenly interrupted at 4200 cal. BP by a major detrital pulse that was probably climate linked (4200 cal. BP event) and that triggered a drop in diatom productivity and diversity. From 4100 to 2400 cal. BP, diatom productivity progressively decreased, whereas Pediastrum developed. Diatom assemblages were more diversified (predominance of Pseudostaurosira robusta, P. brevistriata and P. pseudoconstruens) and reflected a regime of continuous erosion, whereas slopes were colonised by grazed grasslands. Finally, from 2400 cal. BP to the present day, diatom assemblages reveal a slight acidification and nutrient enrichment of waters concomitant with increasing human pressure in the catchment. These results demonstrate the close links between ecosystems and the ready propagation of disturbances throughout watersheds that might lead to abrupt regime shifts in such alpine environments

A modified method based on p-nitrophenol assay to quantify hydrolysis activities of lipases in litters

Lipases are glycerol ester hydrolases (EC 3.1.1.3) produced by a wide range of microorganisms. They catalyse the hydrolysis of different esters depending on the water content of the reaction medium. Here, we developed a simple methodology to quantify lipase hydrolysis activities using two different litters: a litter of Quercus pubescens (QP) and a litter of both Q. pubescens and Q. ilex. Different p-nitrophenyl esters were used to test hydrolysis in a reaction medium with an organic solvent (heptane). We showed that these activities depended on the amount of litter, the incubation time and the substrate concentration and that they increased with temperature. Furthermore, the lipases from the studied litters were still active after 2 h at 70 degrees C. These activities showed common properties of lipases: the highest activities were obtained with a medium-acyl chain substrate, p-nitrophenyl laurate. Moreover abiotic hydrolysis with short-chain acyl substrates was observable. The following parameters are recommended to quantify hydrolysis activities of lipases in litters: 10 mM of p-nitrophenyl laurate in 2 ml of heptane, 1 g of litter, 2 ml of water incubated at 30 degrees C for 2 h