An OGC Web Processing Service for assessing the quality of solar radiation measurements

International audienceA service is presented that assesses the quality of measurements of daily global irradiation or means of global irradi-ance acquired by a ground station. Measurements are checked against models resulting in a measure of plausibility. This on-line service obeys the WPS (Web Processing Service) standard of the Open Geospatial Consortium. It is free of use and can be integrated into routine operations and Web portals thanks due its interoperability capability

A Phenomenological Study of Professional and Practical Changes Experienced by Teachers Involved with Action Research in a Learning Community Master’s Program

In the United States, the majority of teachers have a master’s degree or higher. However, there exist concerns in the literature that having an advanced degree does not make teachers better. There thus needs to be a way to improve the outcome of a master’s degree in education so that teachers do advance their practice and bring change to their classrooms as a direct result of their experience in a master’s degree program. By focusing on the use of action research in a learning community, the intent of the present phenomenological study was to discover changes that occurred in teachers involved in action research in a learning community setting while obtaining their master’s degree. The sample consisted of teachers that have attained their master’s degree from a program involving both action research and the learning community setting offered at the same comprehensive regional university in the Upper Midwest. Based on the extant literature, it was expected that the changes experienced by the teachers may include variations in their teaching practice, professional development, collegial relationships, and leadership roles. The results of the study confirmed these changes and highlighted the development of personal control as an essential quality of effective teachers. The teachers involved in the study considered their perceived improvement as transformative and a direct result of their experience in the master’s degree program

PIXE analyses over a long period: The case of Neolithic variscite jewels from Western Europe (5th-3th millennium BC): The case of Neolithic variscite jewels from Western Europe (5th-3th millennium BC)

International audiencePIXE analysis of archeological variscite beads and pendants from the Neolithic period that were excavated in Spain, Portugal and France and of variscite geological references samples from European occurrences were carried out from 1999 to 2013 in order to trace back the circulation of this precious gemstone over three millennia. Transformations of the AGLAE external beam system and progress in spectrum processing have induced some apparent compositional variation, affecting in particular the phosphorus/aluminum ratio. This long term evolution has been taken into account with the help of geostandards to build a large and coherent geochemical database of minor and trace elements in variscite. This database allowed us to determine the provenance of the raw material and thus of the circulation of the jewels

High spatial resolution solar atlas in Provence-Alpes-Cote d'Azur

International audienceConsidering the spatial resolution of satellite-based databases of surface solar irradiation such as HelioClim-3, the geographic scale of solar mapping that can be derived is approx. 1 / 5 000 000. This geographic scale is suitable for continent or country solar mapping. Nevertheless, customers' feedback notably states that there is a need of spatial resolution improvement. In this context of spatial resolution improvement of solar resource estimation, the project solar atlas in Provence-Alpes-Côte d'Azur (PACA), finalized in December 2010, aims at increasing spatial resolution of HelioClim-3 to derive 250 m resolution solar maps. The solar atlas accounts for the global, direct and diffuse on inclined plane or in normal incidence irradiations and their temporal variations intra and inter-annual, on a monthly basis, since February 2004. The Digital Elevation Model SRTM-V4 is used to get topographic data with a spatial resolution of approximately 100 m and a localization accuracy of typically 10 m. This topographic data is used to estimate high resolution terrain effects on HelioClim-3 derived solar radiation fields, taking into account orographic effects: * Effects of optical path length variations due to terrain elevation; * Shadow effects on direct and circumsolar diffuse radiation computed from local horizon estimation; * Horizon effects on isotropic diffuse radiation with the sky view factor estimation. These orographic phenomena are indeed the source of significant local spatial variations in solar radiation values and potentially discriminating in choosing the location, the calculation of profitability or the sizing of photovoltaic or thermodynamic solar power systems. Solar mapping with a geographic scale of 1 / 3 000 000 or more does not represent properly these local phenomena. In order to establish an accurate mapping at 250 m with associated uncertainty using HelioClim-3 data, procedures of calibration has been established with meteorological ground stations. The global horizontal irradiation is calibrated thanks to the Météo France meteorological network comprising, in PACA, about 30 automatic ground stations delivering at least daily global irradiation on horizontal plane. A strict data quality control has been applied to these ground data to guarantee their quality as reference ground-based daily irradiation data. The diffuse and direct irradiations are calibrated thanks to three specific ground stations dedicated expressly to the project, delivering one year of simultaneous 10-min global and diffuse irradiations on the horizontal plan and direct irradiation on normal incidence. Statistical analysis of direct and cross-validation estimation errors after calibration with the pyranometric ground stations has been made to establish the uncertainties associated with the solar atlas. The root mean square error of monthly irradiation estimation is about 5% (c. 5 kWh / m2) for global, direct and diffuse components on horizontal plane, without significant bias error. The accuracy of monthly direct normal irradiation is about 10% (c. 15 kWh/m2). Data from the solar atlas in PACA is available for free at www.atlas-solaire.fr. In particular, a Web Map Service (WMS), based on the Open Geographical Consortium standards, has been set up to deliver maps from the solar atlas in an interoperable and standard way

Fitness Impact of Obligate Intranuclear Bacterial Symbionts Depends on Host Growth Phase

According to text book definition, parasites reduce the fitness of their hosts whereas mutualists provide benefits. But biotic and abiotic factors influence symbiotic interactions, thus under certain circumstances parasites can provide benefits and mutualists can harm their host. Here we addressed the question which intrinsic biotic factors shape a symbiosis and are crucial for the outcome of the interaction between the obligate intranuclear bacterium Holospora caryophila (Alphaproteobacteria; Rickettsiales) and its unicellular eukaryotic host Paramecium biaurelia (Alveolata; Ciliophora). The virulence of H. caryophila, i.e., the negative fitness effect on host division and cell number, was determined by growth assays of several P. biaurelia strains. The performances of genetically identical lines either infected with H. caryophila or symbiont-free were compared. Following factors were considered as potentially influencing the outcome of the interaction: (1) host strain, (2) parasite strain, and (3) growth phases of the host. All three factors revealed a strong effect on the symbiosis. In presence of H. caryophila, the Paramecium density in the stationary growth phase decreased. Conversely, a positive effect of the bacteria during the exponential phase was observed for several host × parasite combinations resulting in an increased growth rate of infected P. biaurelia. Furthermore, the fitness impact of the tested endosymbionts on different P. biaurelia lines was not only dependent on one of the two involved strains but distinct for the specific combination. Depending on the current host growth phase, the presence of H. caryophila can be harmful or advantageous for P. biaurelia. Thus, under the tested experimental conditions, the symbionts can switch from the provision of benefits to the exploitation of host resources within the same host population and a time-span of less than 6 days

On quality control procedures for solar radiation and meteorological measures, from subhourly to montly average time periods

International audienceMeteorological data measured by ground stations are often a key element in the development and validation of methods exploiting satellite images. These data are considered as a reference against which satellite-derived estimates are compared. Long-term radiation and meteorological measurements are available from a large number of measuring sta- tions. However, close examination of the data often reveals a lack of quality, often for extended periods of time. This lack of quality has been the reason, in many cases, of the rejection of large amount of available data. The quality data must be checked before their use in order to guarantee the inputs for the methods used in modelling, monitoring, forecast, etc. To control their quality, data should be submitted to several conditions or tests. After this checking, data that are not flagged by any of the test is released as a plausible data. In this work, it has been performed a bibliographical research of quality control tests for the common meteoro- logical variables (ambient temperature, relative humidity and wind speed) and for the usual solar radiometrical variables (horizontal global and diffuse components of the solar radiation and the beam normal component). The different tests have been grouped according to the variable and the average time period (sub-hourly, hourly, daily and monthly averages). The quality test may be classified as follows: * Range checks: test that verify values are within a specific range. There are two types of range checks, those based on extrema and those based on rare observations. * Step check: test aimed at detecting unrealistic jumps or stagnation in the time series. * Consistency checks: test that verify the relationship between two or more time series. The gathered quality tests are applicable for all latitudes as they have not been optimized regionally nor seasonably with the aim of being generic. They have been applied to ground measurements in several geographic locations, what result in the detection of some control tests that are no longer adequate, due to different reasons. After the modification of some test, based in our experience, a set of quality control tests is now presented, updated according to technology advances and classified. The presented set of quality tests allows radiation and meteorological data to be tested in order to know their plausibility to be used as inputs in theoretical or empirical methods for scientific research. The research leading to those results has partly receive funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under Grant Agreement no. 262892 (ENDORSE projec

A fusion method for creating sub-hourly DNI-based TMY from long-term satellite-based and short-term ground-based irradiation data

International audienceIn order to correctly perform Concentrated Solar Power (CSP) plant electric energy output estimation, a standard approach is to consider Typical Meteorological Year (TMY) as a reference input data in CSP simulation software such as System Advisor Model or Greenius. These TMYs may be built from satellite derived irradiation databases. In order to correctly estimate the CSP electricity production, it is highly recommended to use sub-hourly DNI information. Due to limitation in spatial and temporal resolution of geostationary satellite images, satellite-based irradiation data lack good representativity in term of any sub-hourly temporal variability. To overcome this limitation, we propose an innovative fusion method to combine a one year short time series of ground-based sub-hourly irradiation data and the long-term satellite-based one to create calibrated, sub-hourly and long-term based TMY irradiation data. This method has been successfully applied in the planning of the CSP plant project in Morocco: one year and a half of high quality 10-minute irradiation data from pyranometric ground stations belonging to the Moroccan Agency for Solar Energy (MASEN) has been used with long-term hourly satellite-based irradiation data to create calibrated 10-minute DNI based TMY. The ground-based irradiation data have passed the standard quality check procedure recommended by the Baseline Solar Radiation Network for the World Climate Research Program. The satellite hourly irradiation data has been calibrated on a one year learning period of ground station data and this calibration has been verified on a subsequent half year ground station data. This calibration has been applied to the hourly long-term satellite irradiation time series from which a TMY was computed. The final and innovative step consists in introducing the site specific sub-hourly variability into the whole set of hourly daily profiles of irradiation of the TMY time series, as needed to obtain a better estimation of the CSP producible. The method uses the whole 10-minute measured irradiation data as a store of available days, normalized in terms of time between sunrise and sunset

Physical realization of a quantum spin liquid based on a novel frustration mechanism

Unlike conventional magnets where the magnetic moments are partially or completely static in the ground state, in a quantum spin liquid they remain in collective motion down to the lowest temperatures. The importance of this state is that it is coherent and highly entangled without breaking local symmetries. Such phenomena is usually sought in simple lattices where antiferromagnetic interactions and/or anisotropies that favor specific alignments of the magnetic moments are "frustrated" by lattice geometries incompatible with such order e.g. triangular structures. Despite an extensive search among such compounds, experimental realizations remain very few. Here we describe the investigation of a novel, unexplored magnetic system consisting of strong ferromagnetic and weaker antiferromagnetic isotropic interactions as realized by the compound Ca$_{10}$Cr$_7$O$_{28}$. Despite its exotic structure we show both experimentally and theoretically that it displays all the features expected of a quantum spin liquid including coherent spin dynamics in the ground state and the complete absence of static magnetism.Comment: Modified version accepted in Nature Physic

HelioClim-3: a near-real time and long-term surface solar irradiance database

International audienceHelioClim-3 is a database containing surface solar irradiance assessed every 15 min from images taken by the Meteosat series of satellites since 2004. It covers Europe, Africa and Atlantic Ocean. In average, comparison with hourly measurements made in meteorological stations yields a correlation coefficient greater than 0.9, a relative root mean square error (rRMSE) around 20% of the mean measured irradiance and a relative mean bias error (rMBE) below 2%. HelioClim-3 can be accessed via the SoDa Service (www.soda- is.org). The availability and quality of HelioClim-3 data should help in performing steps towards a better knowledge of the surface solar irradiance and its variations over recent years