Biodiversity of epiphytic diatom community on seagrasses and corals from Saudi Arabian coasts of the Arabian Gulf: a taxonomical, ecological and environmental approach (oral presentation)

The microphytobenthic community significantly contributes to primary production in shallow waters, mainly along continental shelves where it can reach values exceeding phytoplankton biomass in the overlying water column. Diatom communities are among the dominant components in the microphytobenthos and their species composition is strongly influenced by the nature of substrate and by their biogeographic distribution. On the other hand, these communities appear to be composed by a limited number of genera, belonging to different growth forms that can be considered fully adapted to the epibenthic lifestyle. In spite of the important ecological role played in the food chain, the biodiversity of diatom communities on seagrasses and seaweeds is still poorly studied and highly underestimated while that on corals results virtually neglected as in the literature there are only two studies on this topic. Our study aimed to decrypt and document for the first time the hidden biodiversity of diatoms associated to seagrasses and hard corals along the Saudi coasts of Arabian Gulf. The diatom assemblages have been identified exclusively by electron microscopy so that their community structure has been analyzed in depth and the diversity have been documented at genus/species level. Preliminary results demonstrated that both seagrasses and corals collected along the Saudi Arabian coasts hosted benthic diatom communities, which in both the case constituted the major element of their epibenthic microalgal flora. Significant differences in terms of cell density, species composition and community structure were observed between the diatom communities of seagrasses and corals and within the different sampling locations analyzed. More in detail, cell densities of seagrass diatom communities resulted more than one hundred times higher than those of corals with mean values approximately of 6000-7000 cell/mm2 in the former vs 100-300 cell/mm2 in the latter. Noteworthy is that the specie composition of seagrasses diatom communities was characterized by the almost full dominance of adnate genus Cocconeis (represented by four species) exhibiting cell densities mean values more than one hundred times higher than those of all the other diatom genera present in the communities. The cell density values showed by Cocconeis communities epiphytic on Saudi Arabian gulf seagrasses analyzed in the present study are up to my knowledge the higher registered in any other environment and host organism studied, comparable only to some peculiar monospecific communities found onAntarctic macroalgae. Undoubtedly, the particularly challenging environmental conditions occurring in the different sampling stations selected along the Saudi coastal areas of Arabian Gulf could be responsible of some specific changes in the abundances and specie composition observed in the diatom communities of seagrasses

Building irregularity issues and architectural design in seismic areas

When designing buildings in seismic areas, choices of the architectural designer heavily influences seismic structural performances. Namely, building morphology may lead to complex seismic responses as it occurs when building plan and elevation become irregular. Typical irregularities are due to architectural, functional and distribution constraints, thus leading to plan or vertical or combined plan/vertical irregularities. A frequent plan-wise irregularity arises when earthquake resistant structures, such as cores and shear walls, are concentrated on one side of the building plan, while vertical irregularity often arises from the presence of soft stories especially located at the ground level or, less frequently, at an intermediate level. In the last decades, some trends in architectural design, such as Deconstructivism and other contemporary theories, worked in pursuing architectural solutions based on the concept of �deconstruction� in place of �construction�, favoring non-rigid schemes, non-regular shapes and, more generally, avoiding geometric rules and classical canons of symmetry and regularity. In this paper the above issues are investigated with the goal of assessing effects of irregularity conditions, introduced by the architectural design, on the building seismic performances with the aim at not forbidding the designer ambitions but at making him aware of the effects of his architectural choices

Effect of airborne particle abrasion on microtensile bond strength of total-etch adhesives to human dentin

Aim of this study was to investigate a specific airborne particle abrasion pretreatment on dentin and its effects on microtensile bond strengths of four commercial total-etch adhesives. Midcoronal occlusal dentin of extracted human molars was used. Teeth were randomly assigned to 4 groups according to the adhesive system used: OptiBond FL (FL), OptiBond Solo Plus (SO), Prime & Bond (PB), and Riva Bond LC (RB). Specimens from each group were further divided into two subgroups: control specimens were treated with adhesive procedures; abraded specimens were pretreated with airborne particle abrasion using 50 mu m Al2O3 before adhesion. After bonding procedures, composite crowns were incrementally built up. Specimens were sectioned perpendicular to adhesive interface to producemultiple beams, which were tested under tension until failure. Data were statistically analysed. Failure mode analysis was performed. Overall comparison showed significant increase in bond strength (p < 0.001) between abraded and no-abraded specimens, independently of brand. Intrabrand comparison showed statistical increase when abraded specimens were tested compared to no-abraded ones, with the exception of PB that did not show such difference. Distribution of failure mode was relatively uniform among all subgroups. Surface treatment by airborne particle abrasion with Al2O3 particles can increase the bond strength of total-etch adhesive

Sexual Dimorphism in Rissoides Pallidus (Giesbrecht) (Crustacea, Stomatopoda)

EnThirteen morphometric characters of Rissoides pallidus (Giesbrecht), a small stomatopod crustacean, were measured from 34 males and 32 females. The specimens were collected by means of bottom trawlers on the upper continental slope of the North Tyrrhenian Sea (mid-western Mediterranean Sea). Comparisons of the slopes between sexes indicated no significant difference in all studied dependent parameters (Y) with carapace length (X), except antennular length and scaphocerite width which were significantly longer and larger in females than in males, respectively. The hierarchical cluster analysis was also performed to identify similarity or dissimilarity among the morphometric characters measured. The biometric relationships considered in this work may prove useful during studies of feeding habits, and to reconstruct the size and biomass of the individuals of this small mantis shrimp from the remains of its exoskeleton.ItTredici caratteri morfometrici sono stati misurati in 34 maschi e 32 femmine di Rissoides pallidus (Giesbrecht), un piccolo crostaceo stomatopode. Gli esemplari sono stati raccolti per mezzo di motopescherecci che operano sulla scarpata continentale superiore del Mar Tirreno settentrionale (Mediterraneo occidentale). La comparazione del parametro b delle regressioni nei due sessi non ha mostrato alcuna differenza significativa tra tutti i parametri indagati, ad esclusione della lunghezza delle antennule e della larghezza dello scafocerite che rispettivamente sono risultati significativamente più lunghe e più larghe nelle femmine che nei maschi. È stata eseguita anche un’analisi di agglomerazione al fine di identificare similarità o dissimilarità tra i caratteri morfometrici utilizzati. Le relazioni biometriche considerate in questo lavoro possono risultare utili negli studi di alimentazione poiché dai resti degli individui di questo piccolo stomatopode è possibile risalire alla loro taglia e relativa biomassa

Evaluation of the American Approach for Detecting Plan Irregularity

The European seismic code 8 (Eurocode 8) classifies buildings as planwise regular according to four criteria which are mostly qualitative and a fifth one, which is based on parameters such as stiffness, eccentricity, and torsional radius, that can be only approximately defined for multistory buildings. Therefore, such plan-regularity criteria are in need of improvement. ASCE seismic code, according to a different criterion, considers plan (or “torsional”) irregularity in a building when the maximum story drift, at one end of the structure, exceeds more than 1.2 times the average of the story drifts at the two ends of the structure under equivalent static analysis. Nevertheless, both the ASCE approach and the threshold value of 1.2 need to be supported by adequate background studies, based also on nonlinear seismic analysis. In this paper, a numerical analysis is carried out, by studying the seismic response of an existing R/C school building taken as the reference structure. Linear static analysis is developed by progressively shifting the centre of mass, until the ratio between the maximum lateral displacement of the floor at the level is considered and the average of the horizontal displacements at extreme positions of the floor at the same level matches and even exceeds the value of 1.2. Then, nonlinear dynamic analyses are carried out to check the corresponding level of response irregularity in terms of uneven plan distribution of deformation and displacement demands and performance parameters. The above comparison leads to check the suitability of the ASCE approach and, in particular, of the threshold value of 1.2 for identifying buildings plan irregularity

Confinement of Masonry Columns with Natural Lime-Based Mortar Composite: An Experimental Investigation

The paper presents the results of an experimental campaign on the confinement of masonry square columns with fiber-reinforced lime mortar (FRLM) composites made of a natural lime-based matrix. The experimental results show the effectiveness of such a composite for increasing both strength and ductility performances of strengthened columns. Predictive formulas from the literature and from the Italian guidelines CNR-DT 215/2018 do not perfectly fit the experimental outcomes and do not confirm the strength increase of the confined columns. The reason can be attributed to the very low mechanical properties of the natural matrix used to form such a composite. Therefore, considering that the use of a natural and sustainable matrix fully compatible with the masonry substrate is a fundamental requirement for strengthening masonry columns of buildings belonging to architectural heritage, an additional future effort should be made by researchers involved in this field. In particular, for a reliable prediction of the strength of masonry columns confined with composites made of natural matrices, wider experimental campaigns are necessary to refine available formulas with respect to different substrates and component materials