L'increment de CO2 pot tenir efectes imprevisibles en el clima del planeta

L'ús de combustibles fòssils ha incrementat el CO2 a l'atmosfera i, en conseqüència, l'acidificació dels oceans al llarg dels últims cent anys. I això ha afectat els ecosistemes marins, especialment els organismes amb esquelet calcari com els coralls i certes microalgues. Un equip internacional d'investigadors, amb la participació de la UAB, ha examinat, per primer cop a escala global, com reaccionen en el seu hàbitat natural aquestes microalgues, i han observat que l'efecte és més sever de l'esperat: redueixen el gruix del seu esquel·let i empren més energia per construir-lo. Aquestes petites diferències fisiològiques les situen en desavantatge respecte a espècies competidores i poden arribar a ser substituides parcialment per d'altres. Donat que la captació del diòxid de carboni atmosfèric depèn en gran mesura de l'activitat d'aquests organismes, els efectes observats poden tenir conseqüències imprevisibles per al cicle global del carboni i, per tant, per al clima del planeta. La recerca ha estat publicada a Nature.El uso de combustibles fósiles ha incrementado el CO2 en la atmósfera y, en consecuencia, la acidificación de los océanos en los últimos cien años, lo que ha afectado a los ecosistemas marinos, especialmente a los organismos con esqueleto calcáreo como los corales y ciertas microalgas. Un equipo internacional de investigadores, con la participación de la UAB, ha examinado, por primera vez a escala global, cómo reaccionan en su hábitat natural estas microalgas, y han observado que el efecto es más severo de lo esperado: reducen el grueso de su esqueleto y emplean más energía para construirlo. Estas pequeñas diferencias fisiológicas las sitúan en desventaja respecto a especies competidoras, pudiendo llegar a ser sustituidas parcialmente por otras. Dado que la captación del dióxido de carbono atmosférico depende en gran medida de la actividad de estos organismos, los efectos observados pueden tener consecuencias imprevisibles para el ciclo global del carbono y, por tanto, para el clima del planeta. La investigación ha sido publicada en Nature

ABC likelihood-freee methods for model choice in Gibbs random fields

Gibbs random fields (GRF) are polymorphous statistical models that can be used to analyse different types of dependence, in particular for spatially correlated data. However, when those models are faced with the challenge of selecting a dependence structure from many, the use of standard model choice methods is hampered by the unavailability of the normalising constant in the Gibbs likelihood. In particular, from a Bayesian perspective, the computation of the posterior probabilities of the models under competition requires special likelihood-free simulation techniques like the Approximate Bayesian Computation (ABC) algorithm that is intensively used in population genetics. We show in this paper how to implement an ABC algorithm geared towards model choice in the general setting of Gibbs random fields, demonstrating in particular that there exists a sufficient statistic across models. The accuracy of the approximation to the posterior probabilities can be further improved by importance sampling on the distribution of the models. The practical aspects of the method are detailed through two applications, the test of an iid Bernoulli model versus a first-order Markov chain, and the choice of a folding structure for two proteins.Comment: 19 pages, 5 figures, to appear in Bayesian Analysi

Group 8 metal alkynyl complexes for nonlinear optics

International audienceStudies of the nonlinear optical (NLO) properties of Group 8 metal alkynyl complexes are summarized, with particular focus on results since 2003; structure-NLO property relationships are developed, optical nonlinearities of multipolar alkynyl complexes are described, and switching of the NLO response of molecules and molecular materials derived from Group 8 metal alkynyl complexes is discussed

Combined use of seismic, isotopic and piezometrics data to reduce uncertainty in models

International audienceTo improve modelling of complex multi-aquifer systems, a better understanding of To improve modelling of complex multi-aquifer systems, a better understanding of reservoirs’s geometry and an improvement of calibration are required. Combining seismic data, isotopic analysis and piezometrics measurements is a way to improve flow simulation.In Gironde (France), many hydrodynamics models have been developed to guide choices in groundwaters exploitation. They put into evidence a lack of knowledge on the Villagrains-Landiras structure corresponding to a potential recharge area for the aquifers of the region. To correct these shortcomings, a detailed study of this area was undertaken to measure its potential for exploitation.Three exploratory wells reaching depths ranging from 200 to 350 m have been drilled to refine the structural vision of the region and to delimitate the various erosional gaps.To improve significantly the knowledge of the reservoirs’s geometry, seismic reflection has been used to obtain a high-resolution image of the subsoil. A total of 15 seismic lines have been used, representing a total length of 248 km. At first, 13 old lines, coming from oil prospecting, have been reprocessed to maximize the definition of hydrostratigraphic units in the first 300 meters. Then, two news high-resolution seismic lines have been achieved in September 2007 on a total length of 17.5 km. This geological survey has helped us to constrain the pattern of the various aquifers of the structure. It has also enabled us to adjust the elevation of the tops and bottoms used in the hydrodynamic model.The aim of the hydrogeological study was to characterize the hydrodynamic mechanisms affecting the Villagrains-Landiras structure. The design of water level maps allowed us to study the distribution of hydraulic heads in comparison to the structure and to measure its potential influence on the recharge of groundwaters. The analysis of the piezometrics fluctuations underlined many similar variations which characterize locals behaviour. Isotopic analysis (18O, 2H, 3H, 13C, 14C), allow us to study the recharge, to confirm the influence of the structure in this process and to constrain residence time in the model. This important part of the study involves the interpretation of analysis coming from 4 different aquifers, sampled in 21 wells located on the structure and its near vicinity.This multidisciplinary approach, based on the interpretation of seismic, isotopic and piezometric data, helped us to improve the knowledge of the structural arrangement of the aquifers and the understanding of the hydrodynamic processes to simulate more efficiently flows in the model

Are research methods shaping our understanding of microplastic pollution? A literature review on the seawater and sediment bodies of the Mediterranean Sea

Altres ajuts: Acord transformatiu CRUE-CSICUnidad de excelencia María de Maeztu CEX2019-000940-MThe lack of standardization on the definition and methods in microplastic (MP) research has limited the overall interpretation and intercomparison of published data. This has presented different solutions to assess the presence of these pollutants in the natural environment, bringing the science forward. Microplastics have been reported worldwide across different biological levels and environmental compartments. In the Mediterranean Sea, numerous research efforts have been dedicated to defining the MP pollution levels. The reported MP concentrations are comparable to those found in the convergence zone of ocean gyres, pointing to this basin as one of the world's greatest plastic accumulation areas. However, to what extent are the data produced limited by the methods? Here, we present the results of a systematic review of MP research methods and occurrence targeting the seawater and sediment bodies of the Mediterranean Sea. Based on this dataset, we 1) assess the discrepancies and similarities in the methods, 2) analyze how these differences affect the reported concentrations, and 3) identify the limitations of the data produced for the Mediterranean Sea. Moreover, we reaffirm the pressing need of developing a common reporting terminology, and call for international collaboration between Mediterranean countries, especially with North African countries, to provide a complete picture of the MP pollution status in this basin

Sediment budgets 1

Flood plains can act as important sinks of sediment and associated heavy metals, such as mercury. In this study, we present an estimate of the role of an Amazonian flood plain in sediment storage. The Curuai flood plain is located on the right bank of the Amazon River, 900 km upstream of the mouth. It is a complex system of more than 30 interconnected lakes, with a maximum inundated area of 2300 km2, representing 0.8% of the total flooded area of the Central Amazon basin. For the period 2000-2003, a mean average sediment deposition of 380 000 (±7.82%) t year-1 was determined using a box model calibrated using a network of gauging, meteorological and sediment monitoring stations operated over a 4 year period and analysis of multitemporal remote sensing images. This storage represents approximately 0.6% of the total annual sediment flux transported by the Amazon River. The associated mean specific sedimentation rate approaches 165 t km-2 year-1 if only the flooded area is considered

Coccolithophore community response to ocean acidification and warming in the Eastern Mediterranean Sea : results from a mesocosm experiment

Unidad de excelencia María de Maeztu CEX2019-000940-MMesocosm experiments have been fundamental to investigate the effects of elevated CO and ocean acidification (OA) on planktic communities. However, few of these experiments have been conducted using naturally nutrient-limited waters and/or considering the combined effects of OA and ocean warming (OW). Coccolithophores are a group of calcifying phytoplankton that can reach high abundances in the Mediterranean Sea, and whose responses to OA are modulated by temperature and nutrients. We present the results of the first land-based mesocosm experiment testing the effects of combined OA and OW on an oligotrophic Eastern Mediterranean coccolithophore community. Coccolithophore cell abundance drastically decreased under OW and combined OA and OW (greenhouse, GH) conditions. Emiliania huxleyi calcite mass decreased consistently only in the GH treatment; moreover, anomalous calcifications (i.e. coccolith malformations) were particularly common in the perturbed treatments, especially under OA. Overall, these data suggest that the projected increase in sea surface temperatures, including marine heatwaves, will cause rapid changes in Eastern Mediterranean coccolithophore communities, and that these effects will be exacerbated by OA

Synthesis, reactivity, and some photochemistry of ortho-N,N-dimethylaminomethyl substituted aryl and ferrocenyl pentamethylcyclopentadienyl dicarbonyl iron complexes

Supplementary materials: CCDC 928736, 928273, 928738, 928275, 928274 and 928737 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via http://www.ccdc.cam.ac.uk/data_request/cifInternational audienceOrtho-lithiated N,N-dimethylaminomethyl ferrocene and benzyldimethylamine react with Cp*Fe(CO)2I to give the new complexes ((Cp*Fe(CO)2)-2-(CH2NMe2)C5H3)Fe(Cp) and Cp*Fe(CO)2-C6H4(o-CH2NMe2). Access to a wide variety of alkoxy-substituted complexes ((Cp*Fe(CO)2)-2-(CH2OR)C5H3)Fe(Cp) can be easily achieved by tandem quaternization/alcoholysis of ((Cp*Fe(CO)2)-2-(CH2NMe2)C5H3)Fe(Cp). Preliminary results show that chelated complexes can be obtained by displacement of one of the carbonyl ligands by photolysis. Crystal structures of ((Cp*Fe(CO)2)-2-(CH2NMe2)C5H3)Fe(Cp), ((Cp*Fe(CO)2)-2-(CH2OR)C5H3)Fe(Cp) (R = Ph, Bz, CHPh2 and d-menthyl) and [Cp*Fe(CO)2-C6H4(o-CH2NMe2)][I] are reported

A Zinc(II) Tetraphenylporphyrin Peripherally Functionalized with Redox-Active "trans-[(η5-C5H5)Fe(η5-C5H4)C≡C](κ2- dppe)2Ru(C≡C)-" Substituents: Linear Electrochromism and Third-Order Nonlinear Optics

Dedicated to Dr. Claude Lapinte on the occasion of his retirement, in memory of the good times spent together in France and Australia.International audienceA nonametallic organometallic-coordination complex (4), assembled from redox-active ferrocenyl (Fc) and Ru(κ2-dppe)2 fragments (dppe = 1,2-bis(diphenylphosphino)ethane) as peripheral donor groups and a central Zn(II) tetraphenylporphyrin (ZnTPP) core, has been prepared and characterized. Complex 4 is obtained in one step from a pentametallic organometallic porphyrin precursor following substitution of the peripheral chloride ligands by ferrocenylalkynyl moieties (Ctriple bond; length of mdashCFc). The spectroelectrochemistry of 4, and that of previously reported porphyrins featuring related peripheral electron-rich d6-transition metal alkynyl units, has been investigated; the optical and redox properties of 4 are briefly discussed, and its potential, and that of a related pentanuclear tetraferrocenyl ZnTPP complex, to function as redox-switchable chromophores is examined. Preliminary studies of the cubic NLO properties of 4 have been undertaken by Z-scan studies at 560 nm and 630 nm, the results from which are also reported