Mechanical Properties of a Library of Low-Band-Gap Polymers

The mechanical properties of low-band-gap polymers are important for the long-term survivability of roll-to-roll processed organic electronic devices. Such devices, e.g., solar cells, displays, and thin-film transistors, must survive the rigors of roll-to-roll coating and also thermal and mechanical forces in the outdoor environment and in stretchable and ultraflexible form factors. This paper measures the stiffness (tensile modulus), ductility (crack-onset strain), or both of a combinatorial library of 51 low-band-gap polymers. The purpose of this study is to systematically screen a library of low-band-gap polymers to better understand the connection between molecular structures and mechanical properties in order to design conjugated polymers that permit mechanical robustness and even extreme deformability. While one of the principal conclusions of these experiments is that the structure of an isolated molecule only partially determines the mechanical propertiesanother important codeterminant is the packing structuresome general trends can be identified. (1) Fused rings tend to increase the modulus and decrease the ductility. (2) Branched side chains have the opposite effect. Despite the rigidity of the molecular structure, the most deformable films can be surprisingly compliant (modulus ≥ 150 MPa) and ductile (crack-onset strain ≤ 68%). This paper concludes by proposing a new composite merit factor that combines the power conversion efficiency in a fully solution processed device obtained via roll and roll-to-roll coating and printing (as measured in an earlier paper) and the mechanical deformability toward the goal of producing modules that are both efficient and mechanically stable

Inverted finite elements for div-curl systems in the whole space

We use inverted finite element method (IFEM) for computing three-dimensional vector potentials and for solving div-curl systems in the whole space . IFEM is substantially different from the existing approaches since it is a non truncature method which preserves the unboundness of the domain. After developping the method, we analyze its convergence in term of weighted norms. We then give some three-dimensional numerical results which demonstrate the efficiency and the accuracy of the method and confirm its convergence

Database Of Weeds In Cultivation Fields Of France And Uk, With Ecological And Biogeographical Information

datatsetThe database includes a list of 1577 weed plant taxa found in cultivated fields of France and UK, along with basic ecological and biogeographical information.The database is a CSV file in which the columns are separated with comma, and the decimal sign is ".".It can be imported in R with the command "tax.discoweed <- read.csv("tax.discoweed_18Dec2017_zenodo.csv", header=T, sep=",", dec=".", stringsAsFactors = F)"Taxonomic information is based on TaxRef v10 (Gargominy et al. 2016),- 'taxref10.CD_REF' = code of the accepted name of the taxon in TaxRef,- 'binome.discoweed' = corresponding latine name,- 'family' = family name (following APG III),- 'taxo' = taxonomic rank of the taxon, either 'binome' (species level) or 'infra' (infraspecific level),- 'binome.discoweed.noinfra' = latine name of the superior taxon at species level (different from 'binome.discoweed' for infrataxa),- 'taxref10.CD_REF.noinfra' = code of the accepted name of the superior taxon at species level.The presence of each taxon in one or several of the following data sources is reported:- Species list from a reference flora (observations in cultivated fields over the long term, without sampling protocol),* 'jauzein' = national and comprehensive flora in France (Jauzein 1995),- Species lists from plot-based inventories in cultivated fields,* 'za' = regional survey in 'Zone Atelier Plaine & Val de Sèvre' in SW France (Gaba et al. 2010),* 'biovigilance' = national survey of cultivated fields in France (Biovigilance, Fried et al. 2008),* 'fse' = Farm Scale Evaluations in England and Scotland, UK (Perry, Rothery, Clark et al., 2003),* 'farmbio' = Farm4Bio survey, farms in south east and south west of England, UK (Holland et al., 2013)- Reference list of segetal species (species specialist of arable fields),* 'cambacedes' = reference list in France (Cambacedes et al. 2002)Life form information is extracted from Julve (2014) and provided in the column 'lifeform'.The classification follows a simplified Raunkiaer classification (therophyte, hemicryptophyte, geophyte, phanerophyte-chamaephyte and liana). Regularly biannual plants are included in hemicryptophytes, while plants that can be both annual and biannual are assigned to therophytes.Biogeographic zones are also extracted from Julve (2014) and provided in the column 'biogeo'.The main categories are 'atlantic', 'circumboreal', 'cosmopolitan, 'Eurasian', 'European', 'holarctic', 'introduced', 'Mediterranean', 'orophyte' and 'subtropical'.In some cases, a precision is included within brackets after the category name. For instance, 'introduced(North America)' indicates that the taxon is introduced from North America.In addition, some taxa are local endemics ('Aquitanian', 'Catalan', 'Corsican', 'corso-sard', 'ligure', 'Provencal').A single taxon is classified 'arctic-alpine'.Red list status of weed taxa is derived for France and UK:- 'red.FR' is the status following the assessment of the French National Museum of Natural History (2012),- 'red.UK' is based on the Red List of vascular plants of Cheffings and Farrell (2005), last updated in 2006.The categories are coded following the IUCN nomenclature.A habitat index is provided in column 'module', derived from a network-based analysis of plant communities in open herbaceous vegetation in France (Divgrass database, Violle et al. 2015, Carboni et al. 2016).The main habitat categories of weeds are coded following the Divgrass classification,- 1 = Dry calcareous grasslands- 3 = Mesic grasslands- 5 = Ruderal and trampled grasslands- 9 = Mesophilous and nitrophilous fringes (hedgerows, forest edges...)Taxa belonging to other habitats in Divgrass are coded 99, while the taxa absent from Divgrass have a 'NA' value.Two indexes of ecological specialization are provided based on the frequency of weed taxa in different habitats of the Divgrass database.The indexes are network-based metrics proposed by Guimera and Amaral (2005),- c = coefficient of participation, i.e., the propensity of taxa to be present in diverse habitats, from 0 (specialist, present in a single habitat) to 1 (generalist equally represented in all habitats),- z = within-module degree, i.e., a standardized measure of the frequency of a taxon in its habitat; it is negatve when the taxon is less frequent than average in this habitat, and positive otherwise; the index scales as a number of standard deviations from the mean.The database includes a list of 1577 weed plant taxa found in cultivated fields of France and UK, along with basic ecological and biogeographical information.The database is a CSV file in which the columns are separated with comma, and the decimal sign is ".".It can be imported in R with the command "tax.discoweed <- read.csv("tax.discoweed_18Dec2017_zenodo.csv", header=T, sep=",", dec=".", stringsAsFactors = F)"Taxonomic information is based on TaxRef v10 (Gargominy et al. 2016),- 'taxref10.CD_REF' = code of the accepted name of the taxon in TaxRef,- 'binome.discoweed' = corresponding latine name,- 'family' = family name (following APG III),- 'taxo' = taxonomic rank of the taxon, either 'binome' (species level) or 'infra' (infraspecific level),- 'binome.discoweed.noinfra' = latine name of the superior taxon at species level (different from 'binome.discoweed' for infrataxa),- 'taxref10.CD_REF.noinfra' = code of the accepted name of the superior taxon at species level.The presence of each taxon in one or several of the following data sources is reported:- Species list from a reference flora (observations in cultivated fields over the long term, without sampling protocol),* 'jauzein' = national and comprehensive flora in France (Jauzein 1995),- Species lists from plot-based inventories in cultivated fields,* 'za' = regional survey in 'Zone Atelier Plaine & Val de Sèvre' in SW France (Gaba et al. 2010),* 'biovigilance' = national survey of cultivated fields in France (Biovigilance, Fried et al. 2008),* 'fse' = Farm Scale Evaluations in England and Scotland, UK (Perry, Rothery, Clark et al., 2003),* 'farmbio' = Farm4Bio survey, farms in south east and south west of England, UK (Holland et al., 2013)- Reference list of segetal species (species specialist of arable fields),* 'cambacedes' = reference list in France (Cambacedes et al. 2002)Life form information is extracted from Julve (2014) and provided in the column 'lifeform'.The classification follows a simplified Raunkiaer classification (therophyte, hemicryptophyte, geophyte, phanerophyte-chamaephyte and liana). Regularly biannual plants are included in hemicryptophytes, while plants that can be both annual and biannual are assigned to therophytes.Biogeographic zones are also extracted from Julve (2014) and provided in the column 'biogeo'.The main categories are 'atlantic', 'circumboreal', 'cosmopolitan, 'Eurasian', 'European', 'holarctic', 'introduced', 'Mediterranean', 'orophyte' and 'subtropical'.In some cases, a precision is included within brackets after the category name. For instance, 'introduced(North America)' indicates that the taxon is introduced from North America.In addition, some taxa are local endemics ('Aquitanian', 'Catalan', 'Corsican', 'corso-sard', 'ligure', 'Provencal').A single taxon is classified 'arctic-alpine'.Red list status of weed taxa is derived for France and UK:- 'red.FR' is the status following the assessment of the French National Museum of Natural History (2012),- 'red.UK' is based on the Red List of vascular plants of Cheffings and Farrell (2005), last updated in 2006.The categories are coded following the IUCN nomenclature.A habitat index is provided in column 'module', derived from a network-based analysis of plant communities in open herbaceous vegetation in France (Divgrass database, Violle et al. 2015, Carboni et al. 2016).The main habitat categories of weeds are coded following the Divgrass classification,- 1 = Dry calcareous grasslands- 3 = Mesic grasslands- 5 = Ruderal and trampled grasslands- 9 = Mesophilous and nitrophilous fringes (hedgerows, forest edges...)Taxa belonging to other habitats in Divgrass are coded 99, while the taxa absent from Divgrass have a 'NA' value.Two indexes of ecological specialization are provided based on the frequency of weed taxa in different habitats of the Divgrass database.The indexes are network-based metrics proposed by Guimera and Amaral (2005),- c = coefficient of participation, i.e., the propensity of taxa to be present in diverse habitats, from 0 (specialist, present in a single habitat) to 1 (generalist equally represented in all habitats),- z = within-module degree, i.e., a standardized measure of the frequency of a taxon in its habitat; it is negatve when the taxon is less frequent than average in this habitat, and positive otherwise; the index scales as a number of standard deviations from the mean