Evidence That Ultraviolet Radiation May Depress Short-Term Photosynthetic Rates of Intertidal Ulva lactuca and Consumption by a Generalist Feeder (Clibanarius vittatus)

This article considers the impact of ultraviolet radiation (UVR) on the photosynthesis and consumption of intertidal Ulva lactuca, an important producer and food resource in many coastal ecosystems. Algal fragments were exposed in the laboratory to either UVR and PAR (photosynthetically active radiation) simultaneously or PAR alone. The rates of photosynthesis and consumption by a generalist feeder, the stripped hermit crab (Clibanarius vittatus), were then compared between the two treatments. In both experiments, the biological weighted values for UVR in the laboratory indicate that the experimental set-up provided a level of UVR exposure that would occur in the field. The results show that UVR exposure depresses the photosynthetic rates of U. lactuca at light intensities between 1118 and 2206 μmol m-2 s-1. UVR also reduced the grazing intensity of C. vittatus on U. lactuca with non-UVR-exposed algal pieces supporting about five times more consumption than exposed pieces. The relevance and implications of this study, however, are limited because the results have been obtained with short-term, simple experiments. Studies encompassing a longer time scale and the community of consumers (e.g. exposing both the algae and main consumers simultaneously to experimental UVR levels) are needed to elucidate whether the algae can offset UVR-deleterious effects through the induction of protective compounds and how these compounds and UVR exposure affects the activity of consumers

Prospects For Gulf of Mexico Environmental Recovery and Restoration

Previous oil spills provide clear evidence that ecosystem restoration efforts are challenging, and recovery can take decades. Similar to the Ixtoc 1 well blowout in 1979, the Deepwater Horizon (DWH) oil spill was enormous both in volume of oil spilled and duration, resulting in environmental impacts from the deep ocean to the Gulf of Mexico coastline. Data collected during the National Resource Damage Assessment showed significant damage to coastal areas (especially marshes), marine organisms, and deep-sea habitat. Previous spills have shown that disparate regions recover at different rates, with especially long-term effects in salt marshes and deepsea habitat. Environmental recovery and restoration in the northern Gulf of Mexico are dependent upon fundamental knowledge of ecosystem processes in the region. PostDWH research data provide a starting point for better understanding baselines and ecosystem processes. It is imperative to use the best science available to fully understand DWH environmental impacts and determine the appropriate means to ameliorate those impacts through restoration. Filling data gaps will be necessary to make better restoration decisions, and establishing new baselines will require long-term studies. Future research, especially via NOAA’s RESTORE Science Program and the state-based Centers of Excellence, should provide a path to understanding the potential for restoration and recovery of this vital marine ecosystem

Plasmons polaritons de surface

La plasmonique est l’étude de l’interaction entre les électrons libres d’un métal et la lumière. Les plasmons polaritons de surface sont des modes plasmoniques localisés au niveau d’une interface entre un métal et un diélectrique. Ces ondes évanescentes, qui peuvent être obtenues expérimentalement par différentes approches, ont des propriétés de confinement du champ électrique qui trouvent de nombreuses applications dans le domaine des capteurs et de la spectroscopie

Supplement 1. Data set and list of references compiled.

<h2>File List</h2><blockquote> <p><a href="DataSet.txt">DataSet.txt</a> <br> </p> <p><a href="ReferenceList.txt">ReferenceList.txt</a> </p> </blockquote><h2>Description</h2><p>Notes relevant to the data set compiled:</p> <p>1. Columns correspond to:</p> <blockquote> <p>1^st column: Reference</p> <p>2^nd column:  Community type</p> <p>3^rd column: Ecosystem type</p> <p>4^th column: Net primary production (NPP); in gC m^-2 yr^-1</p> <p>5^th column: Leaf production (leaf P); in gC m^-2 yr^-1</p> <p>6^th column: Detrital production (DP); in gC m^-2 yr^-1</p> <p>7^th column: Leaf detrital production (leaf DP); in gC m^-2 yr^-1</p> <p>8^th column: Decomposition (D); in gC m^-2 yr^-1</p> <p>9^th column: Biomass of detritus consumers (DB); in gC m^-2</p> <p>10^th column: Consumption by herbivores (H); in gC m^-2 yr^-1</p> <p>11^th column: Percentage of production consumed by herbivores (%NPP consumed) </p> <p>12^th column: Herbivore biomass (HB); in gC m^-2</p> <p>13^th column: Total consumption by first-order consumers (TC); in gC m^-2 yr^-1</p> <p>14^th column: Carbon accumulation (CA); in gC m^-2 yr^-1</p> <p>15^th column: Nitrogen concentration in producer biomass (Nbiomass); in % of dry weight </p> <p>16^th column: Phosphorus concentration in producer biomass (Pbiomass); in % of dry weight</p> <p>17^th column: Decomposition rate (k); in day^-1</p> <p>18^th column: Nitrogen concentration in producer detritus (Ndetritus); in % of dry weight</p> <p>19^th column: Phosphorus concentration in producer detritus (Pdetritus); in % of dry weight</p> <p>20^th column: Producer nitrogen concentration used in the regressions vs. Detrital Production and Decomposition (Ndp); in % of dry weight- see note 5</p> <p>21^st column: Producer phosphorus concentration used in the regressions vs. Detrital Production and Decomposition (Pdp); in % of dry weight- see note 5   </p> </blockquote> <p>2. Cells with a dot and no numbers denote variables not provided in the reports.</p> <p>3. Entries marked with # contain our indirect estimates of net primary production, and entries marked with @ our indirect estimates of decomposition, with the highest uncertainty, which still seems unimportant for the results obtained (see text).</p> <p> 4. Reports of communities dominated by rooted macrophytes (i.e., freshwater macrophyte meadows, seagrass meadows and terrestrial communities) having an asterisk (*) include both the above- (leaves and stems) and belowground (roots) compartments.  Reports with two asterisks (**) only include the belowground compartment, and reports with no asterisk refer to the aboveground compartment.</p> <p>5. We did not find many reports with concomitant values of detrital production and nutrient concentrations in producer detritus, or values of decomposition and nutrient concentrations in producer detritus.  Therefore, to test the independence between detrital production and producer nutritional quality (Fig. 8), and between decomposition and producer nutritional quality (Fig. 10), we used values of nutrient concentration in producer biomass or detritus indistinctly (columns 20th and 21st). The results should be similar to those obtained if we had only used concentrations in producer detritus, because, for a given type of ecosystem, nutrient concentrations do not differ between producer biomass and detritus (see Figs. 1b,c and 6c,d).</p> <p>6. In the reports marked with ¶, decomposition rates refer to leaves.  Hence, in those reports values of leaf detrital production have been used for the relationship between decomposition rates and detrital production (Fig. 11b).  Values of total detrital production (both above- and belowground if marked with one asterisk, or only aboveground if marked with no asterisk) have been used for all the other relationships and Figs. (except for Megonigal and Day [1988], see note 8).</p> <p>7. In the reports marked with $, decomposition rates referring to different compartments (e.g., leaves and stems; above- and belowground) have been weighted and averaged into a single value for the relationship between decomposition rates and detrital production (Fig. 11b).  Similarly, in the same reports values of nutrient concentration in producer detritus referring to different compartments have been weighted and averaged into a single value for the relationships between producer nutrient concentration and detrital production (Fig. 8)  and producer nutrient concentration and decomposition (Fig. 10).  Thus, to avoid redundancies, those mean values have been ignored in the histograms (Figs. 6c,d, and e) and relationship between decomposition rates and detritus nutrient concentrations (Fig. 9).</p> <p>8. In the terrestrial reference Megonigal and Day (1988), values of producer nutrient concentrations refer to leaves.  Hence, in this report values of leaf detrital production have also been used in the relationship between detrital production and producer nutrient concentrations (Fig. 8).</p> <p>9. In the terrestrial reference McNaughton (1985), values of net primary production in parentheses include both the above- and belowground compartments, whereas those with no parentheses refer to the aboveground compartment only.  The aboveground values have been used in this paper.</p

Insights into Photopolymerization at the Nanoscale Using Surface Plasmon Resonance Imaging

Near-field photopolymerization (NFPP) driven by surface plasmon resonance has attracted increasing attention in nanofabrication. This interest comes from the nanometer-scale control of polymer thickness, due to the confinement of the evanescent wave within a highly restricted volume at the surface. In this study, a novel approach using a multi-spectral surface plasmon resonance instrument is presented that gives access to real-time images of polymer growth during NFPP with nanometer sensitivity. Using the plasmonic evanescent wave for both polymerization and real-time sensing, the influence of irradiance, concentration of dye, and initiator are investigated on the threshold energy and kinetics of NFPP. How oxygen inhibition in the near field strongly affects photopolymerization is highlighted, more than in the far field

A Novel Conservative Lagrangian Immersed Boundary Method For Wind Turbine Simulations

International audienceThis work presents a novel conservative Lagrangian immersed boundary method (CLIB) to solve incompressible viscous fluid flow problems around solid geometries. Classical immersed boundary methods (IBM) are known to face mass and momentum conservation issues at the frontier between solid and fluid. This original method couples the penalty IBM with a Lagrangian volume of solid (VOS) formulation introducing some extra source terms in the governing equations. These terms serve to represent the existence of a solid body inside the fluid domain and give rise to a fully conservative system of equations. Solid mass conservation is guaranteed thanks to a Lagrangian representation of the solid volume fraction field and is proven effectively independent of the grid resolution. The accuracy of the present method is demonstrated by the good agreement of aerodynamic quantities for two-dimensional flows around stationary and mobile (rotating, oscillating) rigid solid bodies with the values found in literature

Intégration d'un critère de fluidité en génération de trajectoires 5 axes par flanc d'outil

International audienceLa réalisation des pièces en usinage sur le flanc s'avère d'une très grande rentabilité par rapport à l'usinage en bout par balayage des formes complexes. C'est pourquoi les industriels se tournent de plus en plus vers ce procédé pour gagner des parts de marché même si les surfaces considérées ne sont pas développables ni même réglées. Aussi cet article présente l'application d'une approche qui permet de produire une trajectoire d'usinage minimisant les écarts géométriques par rapport à la surface nominale mais aussi les oscillations. Cette approche se base sur un modèle surfacique de la trajectoire d'usinage qui montre tout son intérêt pour assurer une trajectoire fluide et continue en courbure. Après avoir effectué un état de l'art des différentes méthodes de positionnement d'un outil sur le flanc, nous présentons notre approche et un exemple d'application sur lequel un logiciel de FAO a échoué. Les deux approches sont comparées en termes d'écarts géométriques et de fluidité de la trajectoire. Enfin des pistes de progrès permises par l'approche surfacique sont proposées

Evaluation of load estimation approaches for different immersed boundary methods

International audienceRenewable energy production units, such as wind turbines, involve geometrically complex bodies (rigid or flexible) in contact with fluids. State of the art computations in wind energy are based on Large-Eddy simulations (LES) coupled with actuator line methods (ALM). This framework requires the geometry and the airfoil aerodynamic coefficients of the turbine’s blades to model the influence of the structure to the fluid. Although valid in a wide range of configurations, its specific assumptions render it irrelevant in some cases like with yaw misalignment. Therefore we propose the use of another numerical tool, namely the immersed boundary methods (IBM). These methods allow to avoid body-fitted meshes by representing the geometry of the immersed body in the mesh via ‘solid nodes’ with imposed velocity. Due to the lack of body conforming nodes, the computation of forces acting on the body is not trivial.This work aims to compare two force computation approaches for IB methods. The first one is based on the pressure integral over a locally reconstructed fictive body surface (local approach). The second one is based on the formulation of Noca et al. [1], where, thanks to the velocity and vorticity fields in a finite region enclosing the body, we are able to compute the instantaneous forces acting on it (global approach). These methods will be evaluated for two types of penalization IB methods for unstructured grids: i) a sharp-interface IBM where the penalization terms are located in a narrow band around the solid/gas interface, ii) a smoothed-interface IBM where the added forces are regularized in the vicinity of the interface. [2]. Both methods will be examined and validated against resolved body-fitted simulations of well-documented academic cases with stationary and moving bodies. Mesh-dependancy of the methods will also be investigated. The simulations will be performed by the low Mach-number massively-parallel finite-volume unstructured LES flow solver YALES2 [3, 4]

The impact of salinity fluctuations on net oxygen production and inorganic nitrogen uptake by Ulva lactuca (Chlorophyceae). Aquatic Botany,75:

Abstract In this study, we investigate the impact of rapid fluctuations in salinity on short-term net oxygen production and ammonium (NH 4 + ) and nitrate (NO 3 − ) uptake by Ulva lactuca collected within the Mobile Bay estuary (AL). The salinity regime at the study site was highly variable, remaining mostly between 20 and 30 psu with changes over 3 psu occurring rapidly and frequently. Periodic water sampling revealed a significant inverse relationship between NO 3 − concentration and salinity, but not between NH 4 + concentration and salinity. Experimental changes in salinity modelled on those observed at the study site resulted in a decline in net oxygen production, while NH 4 + and NO 3 − uptake rates remained similar. These results suggest that U. lactuca maintains the ability to take up NH 4 + and NO 3 − under conditions of rapidly changing salinity within the salinity range tested and over the short-term scale examined in this study