Decomposition of Ruppia cirrhosa (Petagna) Grande in the sediment of a coastal lagoon

The decomposition process of Ruppia cirrhosa was studied in a Mediterranean coastal lagoon in the Delta of the River Ebro (NE Spain). Leaves and shoots of Ruppia were enclosed in 1 mm-mesh and 100 pm-mesh litter bags to ascertain the effect of detritivores, macroinvertebrates, and bacteria and fungi, respectively. Changes in biomass and carbon, and, nitrogen and phosphorus concentrations in the detritus were studied at the sediment-water interface and in the sediment. Significant differences in biomass decay were observed between the two bag types. Significant differences in decomposition were observed between the two experimental conditions studied using 100 pm-mesh bags. These differences were not significant when using the 1 mm-mesh bags. The carbon content in the detritus remained constant during the decomposition process. The percentage of nitrogen increased progressively from an initial 2.4 % to 3 %. The percentage of phosphorus decreased rapidly during the first two days of decomposition from an initial 0.26 % to 0.17 %. This loss is greater in the sediment than in the water column or at the sediment-water interface. From these results we deduce that the activity of microorganisms seems to be more important in the sediment than in the water-sediment interface, and that grazing by macroinvertebrates has less importance in the sediment than in the water column.

Characterisation of the LMS200 laser beam under the influence of blockage surfaces. Influence on 3D scanning of tree orchards

The geometric characterisation of tree orchards is a high-precision activity comprising the accurate measurement and knowledge of the geometry and structure of the trees. Different types of sensors can be used to perform this characterisation. In this work a terrestrial LIDAR sensor (SICK LMS200) whose emission source was a 905-nm pulsed laser diode was used. Given the known dimensions of the laser beam cross-section (with diameters ranging from 12 mm at the point of emission to 47.2 mm at a distance of 8 m), and the known dimensions of the elements that make up the crops under study (flowers, leaves, fruits, branches, trunks), it was anticipated that, for much of the time, the laser beam would only partially hit a foreground target/object, with the consequent problem of mixed pixels or edge effects. Understanding what happens in such situations was the principal objective of this work. With this in mind, a series of tests were set up to determine the geometry of the emitted beam and to determine the response of the sensor to different beam blockage scenarios. The main conclusions that were drawn from the results obtained were: (i) in a partial beam blockage scenario, the distance value given by the sensor depends more on the blocked radiant power than on the blocked surface area; (ii) there is an area that influences the measurements obtained that is dependent on the percentage of blockage and which ranges from 1.5 to 2.5 m with respect to the foreground target/object. If the laser beam impacts on a second target/object located within this range, this will affect the measurement given by the sensor. To interpret the information obtained from the point clouds provided by the LIDAR sensors, such as the volume occupied and the enclosing area, it is necessary to know the resolution and the process for obtaining this mesh of points and also to be aware of the problem associated with mixed pixels.

Outer membrane vesicles from cold-adapted antarctic bacteria

Many Gram-negative, cold-adapted bacteria from the Antarctic environment produce large amounts of extracellular matter with potential biotechnological applications. Transmission electron microscopy (TEM) analysis after high-pressure freezing and freeze substitution (HPF-FS) showed that this extracellular matter is structurally complex, appearing around cells as a netlike mesh, and composed of an exopolymeric substance (EPS) containing large numbers of outer membrane vesicles (OMVs). Isolation, purification and protein profiling via 1D SDS-PAGE confirmed the outer membrane origin of these Antarctic bacteria OMVs. In an initial attempt to elucidate the role of OMVs in cold-adapted strains of Gram-negative bacteria, a proteomic analysis demonstrated that they were highly enriched in outer membrane proteins and periplasmic proteins associated with nutrient processing and transport, suggesting that the OMVs may be involved in nutrient sensing and bacterial survival. OMVs from Gram-negative bacteria are known to play a role in lateral DNA transfer, but the presence of DNA in these vesicles has remained difficult to explain. A structural study of Shewanella vesiculosa M7T using TEM and Cryo-TEM revealed that this Antarctic Gram-negative bacterium naturally releases conventional one-bilayer OMVs, together with a more complex type of OMV, previously undescribed, which on formation drags along inner membrane and cytoplasmic content and can therefore also entrap DNA.

Outer membrane vesicles from cold-adapted antarctic bacteria

Many Gram-negative, cold-adapted bacteria from the Antarctic environment produce large amounts of extracellular matter with potential biotechnological applications. Transmission electron microscopy (TEM) analysis after high-pressure freezing and freeze substitution (HPF-FS) showed that this extracellular matter is structurally complex, appearing around cells as a netlike mesh, and composed of an exopolymeric substance (EPS) containing large numbers of outer membrane vesicles (OMVs). Isolation, purification and protein profiling via 1D SDS-PAGE confirmed the outer membrane origin of these Antarctic bacteria OMVs. In an initial attempt to elucidate the role of OMVs in cold-adapted strains of Gram-negative bacteria, a proteomic analysis demonstrated that they were highly enriched in outer membrane proteins and periplasmic proteins associated with nutrient processing and transport, suggesting that the OMVs may be involved in nutrient sensing and bacterial survival. OMVs from Gram-negative bacteria are known to play a role in lateral DNA transfer, but the presence of DNA in these vesicles has remained difficult to explain. A structural study of Shewanella vesiculosa M7T using TEM and Cryo-TEM revealed that this Antarctic Gram-negative bacterium naturally releases conventional one-bilayer OMVs, together with a more complex type of OMV, previously undescribed, which on formation drags along inner membrane and cytoplasmic content and can therefore also entrap DNA.

Crustacean and aquatic insect assemblages in the Mediterranean coastal ecosystems of Empord`a wetlands (NE Iberian peninsula)

Coastal wetlands are characterized by high biodiversity, which is one of the main criteria considered when establishing protection policies or when proposing adequate management actions. In this study, the crustacean and aquatic insect composition of the Empord`a wetlands is described. These two faunal groups contribute highly to the total biodiversity in these wetlands but are seldom considered when managing natural areas. A selection (84 sampling points) of all water body types present in the Empord`a wetlands were sampled monthly (surber and dip net with a 250 μm mesh). Sampling was carried out during 3 surveys (1991-92, 1996-97 and 1999-2000). A rich fauna of 125 crustacean and 295 aquatic insect taxa was identified. We characterized each water body type using the most abundant species and the relative species richness of the taxonomic groups. A classification of the water body types, according to similarity between inventories, groups the brackish and hyperhaline systems in one cluster and the various freshwater systems in another one. Among freshwater systems, lotic waters and freshwater wetlands have a high similarity, whereas rice fields and freshwater springs have a low similarity

High-Performance-Tensile-Strength Alpha-Grass Reinforced Starch-Based Fully Biodegradable Composites

Though there has been a great deal of work concerning the development of natural fibers in reinforced starch-based composites, there is still more to be done. In general, cellulose fibers have lower strength than glass fibers; however, their specific strength is not far from that of fiberglass. In this work, alpha-fibers were obtained from alpha-grass through a mild cooking process. The fibers were used to reinforce a starch-based biopolymer. Composites including 5 to 35% (w/w) alpha-grass fibers in their formulation were prepared, tested, and subsequently compared with those of wood- and fiberglass-reinforced polypropylene (PP). The term “high-performance” refers to the tensile strength of the studied composites and is mainly due to a good interphase, a good dispersion of the fibers inside the matrix, and a good aspect ratio. The tensile strength of the composites showed a linear evolution for fiber contents up to 35% (w/w). The strain at break of the composites decreased with the fiber content and showed the stiffening effects of the reinforcement. The prepared composites showed high mechanical properties, even approaching those of glass fiber reinforced composites

Bio-based composites from stone groundwood applied to new product development

This paper deals with the product design, engineering, and material selection intended for the manufacturing of an eco-friendly chair. The final product is expected to combine design attributes with technical and legal feasibility with the implementation of new bio-based materials. Considering the industrial design, a range of objectives and trends were determined after setting the market requirements, and the final concept was proposed and modeled. The product geometry, production technology, and legal specifications were the input data for product engineering. The material selection was based on the technical requirements. Polypropylene (PP) composite materials based on coupled-fiberglass, sized-fiberglass, and coupled-stone ground wood reinforcements were prepared and characterized. Final formulations based on these PP composites are proposed and justified

Determination of corn stalk fibers' strength through modeling of the mechanical properties of its composites

Worldwide cultivation of corn is expanding, due in part to the increasing production of bioethanol. In consequence, huge amounts of corn stalks residues are been produced. Instead of incineration, we transformed the corn stalks into a semichemical pulp and successfully applied it as reinforcement in polypropylene composites. PP composites reinforced with 40% wt corn stalk single fibers were prepared, and their mechanical properties were evaluated. Through mechanical properties modeling of the composites, the intrinsic tensile strength of the cellulosic fibers that constitute the corn stalk have been determined

Splat-based surface reconstruction from defect-laden point sets

We introduce a method for surface reconstruction from point sets that is able to cope with noise and outliers. First, a splat-based representation is computed from the point set. A robust local 3D RANSAC-based procedure is used to filter the point set for outliers, then a local jet surface - a low-degree surface approximation - is fitted to the inliers. Second, we extract the reconstructed surface in the form of a surface triangle mesh through Delaunay refinement. The Delaunay refinement meshing approach requires computing intersections between line segment queries and the surface to be meshed. In the present case, intersection queries are solved from the set of splats through a 1D RANSAC procedure

On the Rule of Mixtures for Predicting Stress-Softening and Residual Strain Effects in Biological Tissues and Biocompatible Materials

In this work, we use the rule of mixtures to develop an equivalent material model in which the total strain energy density is split into the isotropic part related to the matrix component and the anisotropic energy contribution related to the fiber effects. For the isotropic energy part, we select the amended non-Gaussian strain energy density model, while the energy fiber effects are added by considering the equivalent anisotropic volumetric fraction contribution, as well as the isotropized representation form of the eight-chain energy model that accounts for the material anisotropic effects. Furthermore, our proposed material model uses a phenomenological non-monotonous softening function that predicts stress softening effects and has an energy term, derived from the pseudo-elasticity theory, that accounts for residual strain deformations. The model’s theoretical predictions are compared with experimental data collected from human vaginal tissues, mice skin, poly(glycolide-co-caprolactone) (PGC25 3-0) and polypropylene suture materials and tracheal and brain human tissues. In all cases examined here, our equivalent material model closely follows stress-softening and residual strain effects exhibited by experimental data