A community of practice or a working psychological group? Group dynamics in core and peripheral community participation

The concept of communities of practice (CoP) has become increasingly influential in management literature. Yet, many scholars regard the term as too homogenous and lacking in empirical support. Our study explores the Silver Academy, a project involving over 100 unemployed and self-employed managers over the age of 50, who came together with the purpose of sharing knowledge and experience in starting up their own businesses. The study shows how the Academy matches the notion of CoP including mutual relationships, shared engagement and a common consensus of membership. However, applying Bion’s (1961) theory of groups, we challenge the homogenous and consensual notion of a community of practice, illustrating how, through unconscious group processes, some group members exhibit workgroup mentality and the capacity for realistic hard work (and leadership), while others are caught in a basic-assumption mentality, prone to feelings of anxiety, guilt and depression. This is particularly so for a group that has gone through the recent trauma of unemployment

Characterisation of new analogues of palytoxin isolated from an Ostreopsis mascarenensis bloom in the south-western Indian Ocean

A preliminary screening of toxins of the crude extract of Ostreopsis mascarenensis Quod, a benthic dinoflagellate from the south-western Indian Ocean, revealed a neurotoxicity in mice similar to that induced by palytoxin,one of the most potent marine toxins involved in seafood poisoning. The highest toxicity was retained in the butanol-soluble fraction, revealing a strong haemolytic activity, as found for palytoxin. Analyses usinghigh-performance liquid chromatography with ultraviolet detection allowed the detection of two new toxins named mascarenotoxins (McTXs). Their mass spectrum profile and fragmentation pattern, obtained by advancednano-ESI-Q-TOF mass spectrometry of purified McTXs, were similar to those of a reference palytoxin. They were identified as palytoxin analogues, with the characterisation of a specific fragment ion m/z 327. O. mascarenensisis a species not previously known to produce palytoxin analogues

Quantifying location uncertainties in seismicity catalogues: application to the Pyrenees

International audienceLinearised least-square inversions are commonly used to locate small-magnitude earthquakes, as they are fast and simple to implement. These methods are based on minimising the root-mean-square (RMS) of travel time residuals to find the best-fitting location coordinates and origin time. There are two well-known problems that affect location estimates: (1) the linearisation of the inverse problem causes dependence on the initial guess; (2) regularisation produces solutions that depend on the chosen damping coefficient and biased uncertainty estimates. In this work, we propose a method to quantify unbiased uncertainties with a series of synthetic tests. We first generate travel times for events from all possible coordinates on a 3D grid and then locate each synthetic event by using HYPOCENTER software (this can be applied to any location method). We show that the uncertainties estimated from the standard linearised inversion are strongly underestimated, and we propose another method to compute uncertainties. We produce a 3D error map, where at each grid point we plot the location error, defined as the distance between the event at the given grid point and its inverted location. Moreover, we show how this error map varies with the quantity and quality of the data, and with user-defined parameters such as maximum event-station distance or station corrections. We also provide a methodology to tune the seismic location parameters and calculate the corresponding uncertainties for users who are using similar earthquake location software. Finally, we present an application to the Pyrenean region

Radiation-induced transient absorption in optical fibers

Transient absorption in optical fibers has been studied with emphasis on fast absorption components. Radiation damage was induced with a Febetron 706 electron accelerator, modified to deliver an electron pulse width of 1.1 ns. Dye lasers were synchronized to the accelerator to provide a light pulse through the fiber during the radiation pulse. The output light pulse was detected with a biplanar vacuum photodiode. Four scope traces were used on each electron pulse to monitor the Febetron output, the input drive pulse, and two records of the output pulse on two sweep speeds. Detailed data were acquired for times less than 100 ns after irradiation. An insulated enslosure was used to vary fiber temperature from -30/sup 0/C to + 250/sup 0/C. Several fibers were studied with emphasis on ITT T303 PCS fiber. Data were acquired at 600 and 850 nm. Theoretical modeling of the data is presented

Hydrocarbons in a coral reef ecosystem subjected to anthropogenic pressures (La Reunion Island, Indian Ocean)

Environmental context Hydrocarbons are among the most widespread and harmful pollutants found in the aquatic media. Although they have been investigated in various temperate coastal environments, their dynamics in coral reef tropical ecosystems, which are under increasing human pressure, remain poorly understood. It was found that hydrocarbons had moderate to high concentrations, multiple origins (biogenic and anthropogenic) and could be used to track inland intrusions in fore reef waters of the eutrophicated La Saline reef ecosystem (La Reunion Island, Indian Ocean). Abstract The La Saline fringing reef, which is the most important coral reef complex of La Reunion Island, (south-western Indian Ocean), is subjected to anthropogenic pressures through river and groundwater inputs. Salinity and biogeochemical parameters (silicates, nitrates, dissolved organic carbon, chlorophyll-a), as well as aliphatic hydrocarbons (AHs) and polycyclic aromatic hydrocarbons (PAHs) were analysed in particulate and dissolved material from groundwaters, rivers, harbour, back reef, fore reef and oceanic waters in the La Saline reef area during the rainy season (February-March 2012). Particulate and dissolved AH concentration ranges were 0.07-144 and 0.06-0.58 mu gL(-1) respectively. Particulate and dissolved PAH concentrations ranges were 4.3-326 and 28-350ng L-1 respectively. AHs, dominated by nC(15), nC(17), nC(18) compounds or nC(26), nC(27), nC(29), nC(31) compounds, were mainly of biogenic origin (phytoplankton, bacteria, higher-plant debris) although some anthropogenic (petroleum inputs) signatures were recorded in the dissolved phase from the harbour and fore reef areas. PAHs, dominated by two- to three-ring compounds and their alkylated homologues, reflected unburned petroleum inputs, but probably also biogenic sources. From the distribution of salinity, biogeochemical parameters and hydrocarbons, we found that inland waters flowed mainly in the surface and in the southern part of reef waters and that particulate PAHs allowed tracking these inland water intrusions in fore reef waters. Finally, this pilot study highlights the uncoupling between the dynamics of AHs and PAHs in tropical environments

Source Localization of Microseismic Emissions During Pneumatic Fracturing

Localization of signals is a widely applied technique used in different areas of science telecommunication, medicine, or seismology. In this work, we study microseismic emissions due to stick-slip events during pneumatic fracture in a transparent setup at laboratory scale and apply a localization method “Estimated Source Energy Homogeneity.” The seismic location results are compared with the image correlation results for displacement maps corresponding to the event times.We have observed (using optics and acoustics) that the movement starts inside the porous medium and progresses toward the channel tips, eventually causing channels to grow further. This finding could be of interest in understanding fluid-induced earthquake nucleation processes. Similar to in-site applications of pneumatic or fluid-related fracturing, it shows that the area influenced extends beyond the fracture tips. This also shows why even after the end of pumping, we may get earthquakes, such as in the Basel case (Haring et al., 2008, https://doi.org/10.1016/j.geothermics.2008.06.002). Plain Language Summary An uncompacted granular medium having a fixed grain size is placed between two glass plates as a very thin layer. Using air injection, this porous medium is compacted and fractured. This system is monitored using a camera capable of recording more than 100 images per second and accelerometers which can record vibrations in high frequencies. During this injection, earthquake-like vibrations are generated by the system. Sources of these vibrations are located using acoustic recordings and image processing.We have observed that the channeling starts with a compaction inside the medium; this compaction propagates toward the channel tips and cause them to advance further inside the medium

Le cavalier sur l'obstacle : étude complémentaire à "Saut d'obstacles et galop de course" avec films cinématographiques au ralenti... / L. de Sévy,...

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