Surface initial characteristics and rainfall influence on fractal dimension of soil microrelief

[Abstract] The complex behavior of soil surface microrelief and its evolution is difficult to quantify. Several empirical roughness indices and geostatistical procedures currently used have been found to be sensitive to describe roughness differences between surfaces and changes within a surface due to rainfall. Such indices are simple, quantitative and synthetic descriptors of the complex soil surface organization, thought spatial indices provide some information about the association of main elements (biggest clods and aggregates) determining microrelief variations. Fractals are mathematical objects that show the same structure when examined at all possibles scales. Fractal dimension, the basic parameter characterizing a fractal object, is a potential index to quantify soil micorelief characteristics and changes induced by rainfall energy. A high resolution non-contact laser profile meter was used to measure microtopography on two artificial soil surfaces, before and after simulated rainfall. The experimental surfaces were reconstructed from aggregates of a plough layer and were thought to simulate two types of natural seedbeds, rough and fine. The calculation of the fractal dimension was performed through a variational method, by a numerical algorithm based on the roughness around the local root mean square (RMS), which develops a straight line roughnes (SLR). Plotting SLR values versus distance along a profile in a log-log scale results in a straight trend line over a limited range of distance, the slope of which is designed as Hurst exponent, related to the fractal dimension. Thus, the spatial organisation of the soil surface can be considered as a fractal structure over a finite range of scales. Mean values of the surface fractal dimension were 2.51 for the rough surface and the 2.72 for the fine one. The slow decrease of microrelief caused by surface sealing under rainfall was also described by the fractal index. This study showed that fractal analysis provides a relevant quantification of seedbed type and an assessment of microrelief changes in relation to rainfall amount

Performance analysis of Ti-Nb-Zr-Ta to development medium entropy alloys by powder metallurgy

The field of biomedical high entropy alloys has become a vital area because they can make human life easier. The most alloys used in biomedical application are Ti6Al4V due to the titanium element. Pure titanium (CP-Ti) has excellent corrosion resistance but the titanium and its alloys have high price [1, 2]. High Entropy Alloys (HEAs) are defined as alloys that consist of five main elements or more mixed in an equiatomic, near-equiatomic and equimasic fraction [3]. The behavior is being investigated for high entropy alloying elements and the design methods. Powder metallurgical techniques can be used to obtain HEA based on compatible alloy for biomedical applications with uncomplicated and inexpensive way to process. The demanded alloys for biomedical applications are excellent in plasticity, low in Young modulus, and high in strength; the alloy components are low-toxicity and are completely free from them. Many HEAs have superior mechanical properties, microstructure and good biocompatibility [4-7], in contrast to Ti6Al4V when used for bone implants; it has been shown that there is significant bone wear. Besides, aluminum and vanadium can have adverse effects on the human body [8]. In this work, a medium entropy alloys (MEA) base on Ti-Nb-Zr-Ta system (Ti25Nb25Zr25Ta25) has been studied using conventional powder metallurgy techniques. Their microstructure, mechanical properties and chemical properties have also been studied. The results obtained demonstrate the influence and performance of equiatomic and equimasic of these alloys and their ability to work successfully for possible use as biomedical implants

Fractal theory and scale change effect: application for studying soil porosity

[Abstract] In this article the fractal theory and its application to soil structure and porosity is rewieved.Fractal geometry may provide a reliable description of soil structure, particularly in the case of heterogeneous soil. The rewiev illustrates how the geometry of complex porous media may be represented with simple fractal scaling models. Furthermore, three main clases of models proposed in the literature for soil porous space representation are discussed. A case study was presented based on quantitative evaluation of pore size distributions carried on nine pairs of cultivated and uncultivated neighbour located soils. The fractal approach appears to be a useful tool for understanding domains of organization as found in soil aggregates

On the presence of Trachinus pellegrini (Trachinidae) in the Canary and Cape Verde Islands (north-eastern Atlantic)

Présence de Trachinus pellegrini (Trachinidae) aux îles Canaries etCanaries et aux îles du Cap-Vert (Atlantique nord-est). Trachinus pellegrini Cadenat, 1937 est signalée pour la première fois aux îles Canaries, ce qui représente sa limite de répartition la plus septentrionale. Les différences morphologiques entre adultes et juvéniles sont également présentées. La présence de cette espèce aux îles du Cap-Vert est aussi confirmée.Postprin

Assessing sea grass meadows condition at “El Río” Special Area of Conservation off “La Graciosa e Islotes del Norte de Lanzarote” Marine Reserve

Cymodosea nodosa meadows, known as ‘sebadales’ or ‘manchones’ at Canary Islands, represent EUNIS habitat type code A5.5311, called Macaronesian Cymodocea beds. As it’s described at European Union Habitats Directive (92/43/CEE) Annex 1, sea grass meadows belong to 1110 Sandbanks which are slightly covered by seawater all the time, within Natura 2000 Network. Several ‘sebadales’ throughout the archipelago are included in this Network as Special Areas of Conservation. Cymodosea nodosa is regionally included within the Canary Islands Protected Species List (Ley 4/2010), as a species ‘of interest to ecosystems of Canary Islands”, is usually found at a narrow depth range (10 to 20 m of depth) and, on the whole, best structured meadows are settled at sheltered bays, away from wave and current beating, flimsier at exposed areas. Deeper meadows are also sparser, being C. nodosa replaced by green algae Caulerpa prolifera and Caulerpa racemosa, although mixed algae-sea grass meadows are often found at different depths. The project Assessment of marine flora (‘sebadal’, ma¨erl, ‘mujo’) of ‘La Graciosa e Islotes del Norte de Lanzarote’ Marine Reserve, funded by ‘Viceconsejer´ıa de Pesca y Aguas de la Consejer´ıa de Agricultura, Ganader´ıa, Pesca y Aguas’, Canary Islands Government, has had the aim of assessing sea grass meadows condition and distribution at ‘El R´ıo’ Natura 2000 Network Special Area of Conservation, the channel between La Graciosa and Lanzarote. ‘LA GRACIOSA 1311’ cruise was performed within the framework of the project. First of all previous information on sea grass shallow distribution (up to a depth of 20 m) in the study area was reviewed. Afterwards, a tugged underwater video camera was used onboard of the Marine Reserve Surveillance Vessel to update cartographic info performing a grid of sampling stations, covering previously known distribution limits and verifying current presence/absence data and density. Furthermore, population parameters were obtained in order to assess ‘sebadal’ condition. Fixed stations were selected in regards to this process, and methodology applied on them was as follows: five radial arranged transects were performed, identifying fragmentation (it estimates meadow continuity regarding observed cover), density (mean value of several shoots number counts with 20 x 20 cm grids placed every 2 m), height (mean value in cm of 10 independent samples by transect) and fish and macroinvertebrate species richness for each transect. Graphic picture of sea grass density was made depending on two levels: low density level transects ( 10 shoots/grid ( 50 shoots/m2) and medium density level transects ( 10 shoots/grid ( 50 shoots/m2). Main study result is an estimate for the study region (‘El R´ıo’) and time of year of Cymodocea nodosa population total distribution cover which comes to 1.640.076 m2, including a higher density ‘sebadal’ of 178.256 m2

Effects of the anthropogenics pressures (marine litter) on the coastal ecosystems of the Marine Reserve “Isla de La Graciosa e islotes del norte de Lanzarote”

The European Marine Strategy Framework Directive (2008/56/EC) considers marine litter as one of its environmental descriptors, requiring the development and standardization of criteria and methodologies for its use to test the good environmental status of marine conditions. The assessment of the impact caused by litter accumulation in the shoreline lacked specific monitoring planning and had not been systematically performed to date in Canary Islands. During the project ”Evaluation of the effect of the anthropogenic pressures (marine litter in beaches and alteration of shallow seabed by boats anchoring) on the coastal ecosystems of the “Marine Reserve of Isla de La Graciosa e islotes del norte de Lanzarote (MRLG)” developed with the financial help of the Canary Islands Government (Council of Agriculture, Ranching, Fishing and Waters), two surveys were carried out, ”LA GRACIOSA 1310” and “LA GRACIOSA 1311”, both developed at MRLG and its vicinities. The aim has been to depict MRLG shoreline and to locate marine litter accumulation points the most, contributing with some tools to assess and manage the coastal ecosystems of the marine reserve. Total shoreline sampled at both surveys together was 38326 m, 1834 m at Alegranza, 1366 m at Monta˜na Clara, 24656 m at La Graciosa Island, and the rest, 10470 m, at the Lanzarote’s shoreline portion bathed by MRLG waters. Shoreline sampling was made qualitatively sorting the sampling stations, according to litter presence and distribution, by means of a upward numerical coding related to the type of waste or garbage found. Moreover, each station was additionally depicted according to the type of substrate as well as to the prevailing type of waste, defining what we named “transects”. To validate methodology to European standards, a more exhaustive experimental sampling was made in four transects identified as high density or high concentration of marine litter, following guidelines of a method developed for OSPAR maritime area during the first half of 2000 decade (OSPAR, 2007). It involves evaluating the possibilities and needs of adjustment of this methodology to the particular conditions of our region (Gonz´alez, et al., 2013 a and b). As preliminary results, the spatial distribution of garbage coastal accumulation will be shown in a cartographic base, expressed as relative abundance by island, according to a 4 degrees scale (no litter, low, medium and high litter presence) and according to the dominant kind of garbage in each transect. An example with one of the most densely occupied with trash transects is shown to illustrate a sampling method without the requirement of trash collection. This method uses a sampling unit of 1x1 m grid, divided in 10x10 cm subgrids. This grid is set parallel to sampling direction repeatedly. Distance between grids is determined by a randomizing software. Sampling direction zigzags from sea border to beach back shore, making 45° degrees angles. Subgrids occupied by trash are counted once the grid is set. Waste is depict and identified following a guide developed for this purpose by OSPAR in 2010