Temperature dependence of the nitrogen-vacancy magnetic resonance in diamond

The temperature dependence of the magnetic resonance spectra of nitrogen-vacancy (NV-) ensembles in the range of 280-330 K was studied. Four samples prepared under different conditions were studied with NV- concentrations ranging from 10 ppb to 15 ppm. For all of these samples, the axial zero-field splitting (ZFS) parameter, D, was found to vary significantly with temperature, T, as dD/dT = -74.2(7) kHz/K. The transverse ZFS parameter, E, was non-zero (between 4 and 11 MHz) in all samples, and exhibited a temperature dependence of dE/(EdT) = -1.4(3) x 10^(-4) K^(-1). The results might be accounted for by considering local thermal expansion. The observation of the temperature dependence of the ZFS parameters presents a significant challenge for room-temperature diamond magnetometers and may ultimately limit their bandwidth and sensitivity.Comment: 5 pages, 2 figures, 1 tabl

From time series to superstatistics

Complex nonequilibrium systems are often effectively described by a `statistics of a statistics', in short, a `superstatistics'. We describe how to proceed from a given experimental time series to a superstatistical description. We argue that many experimental data fall into three different universality classes: chi^2-superstatistics (Tsallis statistics), inverse chi^2-superstatistics, and log-normal superstatistics. We discuss how to extract the two relevant well separated superstatistical time scales tau and T, the probability density of the superstatistical parameter beta, and the correlation function for beta from the experimental data. We illustrate our approach by applying it to velocity time series measured in turbulent Taylor-Couette flow, which is well described by log-normal superstatistics and exhibits clear time scale separation.Comment: 7 pages, 9 figure

Cité créative et économie sociale culturelle: étude de cas de Montréal

Suivant en cela le thème de la « cité créative » développé par Richard Florida (2002), la culture est vue par les décideurs publics comme pouvant s’inscrire dans une volonté accrue de rendre attractifs certains territoires. Dans ce cadre, l’économie sociale, représentant une part majoritaire des organisations culturelles, a un rôle majeur à jouer en raison de ses rapports particuliers au territoire. À partir d’une étude de cas de Montréal, nous soulignons les potentialités du développement de l’économie sociale culturelle ainsi que les enjeux soulevés à propos des politiques publiques

Numerical Schemes for Multivalued Backward Stochastic Differential Systems

We define some approximation schemes for different kinds of generalized backward stochastic differential systems, considered in the Markovian framework. We propose a mixed approximation scheme for a decoupled system of forward reflected SDE and backward stochastic variational inequality. We use an Euler scheme type, combined with Yosida approximation techniques.Comment: 13 page

Optical quenching and recovery of photoconductivity in single-crystal diamond

We study the photocurrent induced by pulsed-light illumination (pulse duration is several nanoseconds) of single-crystal diamond containing nitrogen impurities. Application of additional continuous-wave light of the same wavelength quenches pulsed photocurrent. Characterization of the optically quenched photocurrent and its recovery is important for the development of diamond based electronics and sensing

Plant community structure mediates potential methane production and potential iron reduction in wetland mesocosms.

Abstract Wetlands are the largest natural source of methane to the atmosphere, but factors controlling methane emissions from wetlands are a major source of uncertainty in greenhouse gas budgets and projections of future climate change. We conducted a controlled outdoor mesocosm experiment to assess the effects of plant community structure (functional group richness and composition) on potential methane production and potential iron reduction in freshwater emergent marshes. Four plant functional groups (facultative annuals, obligate annuals, reeds, and tussocks) were arranged in a full-factorial design and additional mesocosms were assigned as no-plant controls. Soil samples from the top 10 cm were collected three times during the growing season to determine potential methane production and potential iron reduction (in unamended soils and in soils amended with 200 mM formate). These data were compared to soil organic matter, soil pH, and previously published data on above and belowground plant biomass. We found that functional group richness was less important than the presence of specific functional groups (reeds or tussocks) in mediating potential iron reduction. In our mesocosms, where oxidized iron was abundant and electron donors were limiting, iron reducing bacteria outcompeted methanogens, keeping methane production barely detectable in unamended lab incubations. When the possibility of re-oxidizing iron was eliminated via anaerobic incubations and the electron donor limitation was removed by adding formate, potential methane production increased and followed the same patterns as potential iron reduction. Our findings suggest that in the absence of abundant oxidized iron and/or the presence of abundant electron donors, wetlands dominated by either reeds or tussocks may have increased methane production compared to wetlands dominated by annuals. Depending on functional traits such as plant transport and rhizospheric oxygenation capacities, this could potentially lead to increased methane emissions in some wetlands. Additional research examining the role these plant functional groups play in other aspects of methane dynamics will be useful given the importance of methane as a greenhouse gas