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Catalina Peralesraya - One of the best experts on this subject based on the ideXlab platform.
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exploring the embryonic development of upper Beak in octopus vulgaris cuvier 1797 new findings and implications for age estimation
Fisheries Research, 2020Co-Authors: Enrico Nicola Armelloni, Maria Jesus Lagorouco, Aurora Bartolome, B C Felipe, E Almansa, Catalina PeralesrayaAbstract:Abstract The Beak of cephalopods (in particular octopods, where statoliths are not suitable) is a useful tool for age estimation and the aging method provides essential information on cephalopod growth and life cycles. These parameters are valuable in the assessment of population dynamics and stock management. The embryonic development of cephalopod Beaks is poorly known. The presence of pre-hatching increments on the reading areas (rostrum and lateral walls) is unclear and there are no data on temperature influence. In this study, egg clusters of Octopus vulgaris were reared at 16, 19, 21, 23, and 26 °C. The extracted upper jaws were observed in order to validate the age of first daily increment formation, assessing the accuracy of age inferred from the two reading areas. Jaw dimensions were also measured in order to explore the development at different temperature conditions. The growth rate was calculated for Beaks of rearing condition 21 °C, and the overall dimensions were compared among all incubation temperatures. Three ad hoc developmental stages are proposed for the upper Beak of O. vulgaris embryos. Increments on lateral walls appear during the second phase, whereas the first increment on the rostrum is visible only at hatching. Consequently, only the accuracy of age inferred from the rostrum surface is confirmed for the early stages. The growth rate of the rostrum region accounted for a drop in growth during the third phase. Conversely, the growth rate increased until hatching in lateral walls, suggesting that the heterogeneity of the growth rate could be due to the different role played by the Beak areas. Temperature influenced Beaks in terms of overall size, as embryos reared at a warm temperature (23 °C) were smaller than the others. These results confirm that the incubation environment could alter hatchling characteristics thus affecting the recruitment conditions.
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age of spent octopus vulgaris and stress mark analysis using Beaks of wild individuals
Hydrobiologia, 2014Co-Authors: Catalina Peralesraya, Aurora Bartolome, Alba Juradoruzafa, Veronica Duque, Maria Nazaret Carrasco, E FrailenuezAbstract:Age estimation of the cephalopod Octopus vulgaris by using Beaks has improved in recent years, but maximum age and longevity in the wild have not been confirmed due to the low availability of senescent wild octopuses. In this study, a Beak analysis of lateral wall surfaces (LWS) from 20 spent specimens confirmed the 1-year lifecycle of the species in Central East Atlantic waters. Stress marks (checks) were clearly located in the daily increment sequence of rostrum sagittal sections (RSS). The highest daily variations in sea surface temperature (ΔT) that occurred during the last months of their lifetimes coincided with the locations of the marks on the Beak, enabling confirmation of O. vulgaris Beaks as life recorders for the first time. It also supports the daily deposition of RSS Beak increments in the wild. Individuals were grouped into two main zones, at 20oN and 18oN, respectively. Both groups showed different thermal check patterns, in accordance with the oceanographic differences. Two other checks (not coinciding with high values of ΔT) were observed in RSS at averages of 15 and 28 days before death, respectively, which were interpreted as responding to senescent-related events.
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age estimation obtained from analysis of octopus octopus vulgaris cuvier 1797 Beaks improvements and comparisons
Fisheries Research, 2010Co-Authors: Catalina Peralesraya, Aurora Bartolome, Teresa M Garciasantamaria, Pedro Pascualalayon, E AlmansaAbstract:Two methods are currently available for age estimation in octopus Beaks. They have been applied to the same specimen from a sample of 30 individuals of Octopus vulgaris caught in central-eastern Atlantic waters. These techniques aim at revealing growth increments in the rostrum sagittal sections (RSS) and lateral wall surfaces (LWS) of octopus upper and lower Beaks. Both methods were improved to reduce the time of sample preparation and to enhance the appearance of the increments. For each individual, two independent readings were done for upper and lower Beak sections, as well as for the lateral wall surfaces. Vertical reflected light (epifluorescence) and image analysis system were shown to be useful in the observation and analysis of the sequence of increments. Precision of the ageing, increment counts obtained by both techniques, and increment widths were discussed. Using upper Beak RSS led to more precise age estimates, whereas preparing LWS was quicker and simpler, and revealed a higher number of increments. Therefore, our study recommends counting growth increments in LWS of Beaks to age adult common octopus.
K Sankaranarayanasamy - One of the best experts on this subject based on the ideXlab platform.
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some studies on weld bead geometries for laser spot welding process using finite element analysis
Materials & Design, 2012Co-Authors: Siva N Shanmugam, G Buvanashekaran, K SankaranarayanasamyAbstract:Abstract Nd:YAG laser beam welding is a high power density welding process which has the capability to focus the beam to a very small spot diameter of about 0.4 mm. It has favorable characteristics namely, low heat input, narrow heat affected zone and lower distortions, as compared to conventional welding processes. In this study, finite element method (FEM) is applied for predicting the weld bead geometry i.e. bead length (BL), bead width (BW) and depth of penetration (DP) in laser spot welding of AISI 304 stainless steel sheet of thickness 2.5 mm. The input parameters of laser spot welding such as beam power, incident angle of the beam and beam exposure time are varied for conducting experimental trials and numerical simulations. Temperature-dependent thermal properties of AISI 304 stainless steel, the effect of latent heat of fusion, and the convective and radiative aspects of boundary conditions are considered while developing the finite element model. The heat input to the developed model is assumed to be a three-dimensional conical Gaussian heat source. Finite-element simulations of laser spot welding were carried out by using Ansys Parametric Design Language (APDL) available in finite-element code, ANSYS. The results of the numerical analysis provide the shape of the weld beads for different ranges of laser input parameters that are subsequently compared with the results obtained through experimentation and it is found that they are in good agreement.
Jeffrey Podos - One of the best experts on this subject based on the ideXlab platform.
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Is Beak Morphology in Darwin’s Finches Tuned to Loading Demands?
2015Co-Authors: Joris Soons, Annelies Genbrugge, Jeffrey Podos, Peter Aerts, Dominique Adriaens, Joris Dirckx, Anthony HerrelAbstract:One of nature's premier illustrations of adaptive evolution concerns the tight correspondence in birds between Beak morphology and feeding behavior. In seed-crushing birds, Beaks have been suggested to evolve at least in part to avoid fracture. Yet, we know little about mechanical relationships between Beak shape, stress dissipation, and fracture avoidance. This study tests these relationships for Darwin's finches, a clade of birds renowned for their diversity in Beak form and function. We obtained anatomical data from micro-CT scans and dissections, which in turn informed the construction of finite element models of the bony Beak and rhamphotheca. Our models offer two new insights. First, engineering safety factors are found to range between 1 and 2.5 under natural loading conditions, with the lowest safety factors being observed in species with the highest bite forces. Second, size-scaled finite element (FE) models reveal a correspondence between inferred Beak loading profiles and observed feeding strategies (e.g. edge-crushing versus tip-biting), with safety factors decreasing for base-crushers biting at the Beak tip. Additionally, we identify significant correlations between safety factors, keratin thickness at bite locations, and Beak aspect ratio (depth versus length). These lines of evidence together suggest that Beak shape indeed evolves to resist feeding forces.
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mechanical stress fracture risk and Beak evolution in darwin s ground finches geospiza
Philosophical Transactions of the Royal Society B, 2010Co-Authors: Joris Soons, Annelies Genbrugge, Jeffrey Podos, Yoni De Witte, Peter Aerts, Dominique Adriaens, Patric JacobsAbstract:Darwin's finches have radiated from a common ancestor into 14 descendent species, each specializing on distinct food resources and evolving divergent Beak forms. Beak morphology in the ground finches (Geospiza) has been shown to evolve via natural selection in response to variation in food type, food availability and interspecific competition for food. From a mechanical perspective, however, Beak size and shape are only indirectly related to birds' abilities to crack seeds, and Beak form is hypothesized to evolve mainly under selection for fracture avoidance. Here, we test the fracture-avoidance hypothesis using finite-element modelling. We find that across species, mechanical loading is similar and approaches reported values of bone strength, thus suggesting pervasive selection on fracture avoidance. Additionally, deep and wide Beaks are better suited for dissipating stress than are more elongate Beaks when scaled to common sizes and loadings. Our results illustrate that deep and wide Beaks in ground finches enable reduction of areas with high stress and peak stress magnitudes, allowing birds to crack hard seeds while limiting the risk of Beak failure. These results may explain strong selection on Beak depth and width in natural populations of Darwin's finches.
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Beak morphology and song features covary in a population of darwin s finches geospiza fortis
Biological Journal of The Linnean Society, 2006Co-Authors: Sarah K. Huber, Jeffrey PodosAbstract:Animal mating signals evolve in part through indirect natural selection on anatomical traits that influence signal expression. In songbirds, for example, natural selection on Beak form and function can influence the evolution of song features, because of the role of the Beak in song production. In this study we characterize the relationship between Beak morphology and song features within a bimodal population of Geospiza fortis on Santa Cruz Island, Galapagos. This is the only extant population of Darwin’s finches that is known to possess a bimodal distribution in Beak size. We test the hypothesis that birds with larger Beaks are constrained to produce songs with lower frequencies and decreased vocal performance. We find that birds with longer, deeper, and wider Beaks produce songs with significantly lower minimum frequencies, maximum frequencies and frequency bandwidths. Results from the analysis of the relationship between Beak morphology and trill rate are mixed. Measures of Beak morphology correlated positively with ‘vocal deviation’, a composite index of vocal performance. Overall these results support a resonance model of vocal tract function, and suggest that Beak morphology, a primary target of ecological selection in Darwin’s finches, affects the evolution of mating signals. We suggest that differences in song between the two modes of the distribution may influence mate recognition and perhaps facilitate assortative mating by Beak size and population divergence. © 2006 The Linnean Society of London, Biological Journal of the Linnean Society, 2006, 88, 489–498.
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correlated evolution of morphology and vocal signal structure in darwin s finches
Nature, 2001Co-Authors: Jeffrey PodosAbstract:Speciation in many animal taxa is catalysed by the evolutionary diversification of mating signals. According to classical theories of speciation, mating signals diversify, in part, as an incidental byproduct of adaptation by natural selection to divergent ecologies, although empirical evidence in support of this hypothesis has been limited. Here I show, in Darwin's finches of the Galapagos Islands, that diversification of Beak morphology and body size has shaped patterns of vocal signal evolution, such that birds with large Beaks and body sizes have evolved songs with comparatively low rates of syllable repetition and narrow frequency bandwidths. The converse is true for small birds. Patterns of correlated evolution among morphology and song are consistent with the hypothesis that Beak morphology constrains vocal evolution, with different Beak morphologies differentially limiting a bird's ability to modulate vocal tract configurations during song production. These data illustrate how morphological adaptation may drive signal evolution and reproductive isolation, and furthermore identify a possible cause for rapid speciation in Darwin's finches.
F. Sarri - One of the best experts on this subject based on the ideXlab platform.
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laser beam welding of dissimilar stainless steels in a fillet joint configuration
Journal of Materials Processing Technology, 2012Co-Authors: M.m.a. Khan, Luca Romoli, M. Fiaschi, Gino Dini, F. SarriAbstract:Abstract This paper investigates laser beam welding of dissimilar AISI 304L and AISI 430 stainless steels. Experimental studies were focused on effects of laser power, welding speed, defocus distance, beam incident angle, and line energy on weld bead geometry and shearing force. Metallurgical analysis was conducted on a selected weld only to show various microstructures typically formed at different zones and consequent change in microhardness. Laser power and welding speed were the most significant factors affecting weld geometry and shearing force. All the bead characteristics but radial penetration depth decreased with increased beam incident angle. The focused beam allowed selecting lower laser power and faster welding speed to obtain the same weld geometry. Weld shape factor increased rapidly due to keyhole formation for line energy input ranging from 15 kJ/m to 17 kJ/m. Fusion zone microstructures contained a variety of complex austenite–ferrite structures. Local microhardness of fusion zone was greater than that of both base metals.
Madhusudhan G Reddy - One of the best experts on this subject based on the ideXlab platform.
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process parameters weld bead geometry interactions and their influence on mechanical properties a case of dissimilar aluminium alloy electron beam welds
Defence Technology, 2018Co-Authors: P Mastanaiah, Abhay Sharma, Madhusudhan G ReddyAbstract:Abstract Prediction of weld bead geometry is always an interesting and challenging research topic as it involves understanding of complex multi input and multi output system. The weld bead geometry has a profound impact on the load bearing capability of a weld joint, which in-turn decides the performance in real time service conditions. The present study introduces a novel approach of detecting a relationship between weld bead geometry and mechanical properties (e.g. tensile load) for the purpose of catering the best the process could offer. The significance of the proposed approach is demonstrated by a case of dissimilar aluminium alloy (AA2219 and AA5083) electron beam welds. A mathematical model of tensile braking load as a function of geometrical attributes of weld bead geometry is presented. The results of investigation suggests the effective thickness of weld – a geometric parameter of weld bead has the most significant influence on tensile breaking load of dissimilar weld joint. The observations on bead geometry and the mechanical properties (microhardness, ultimate tensile load and face bend angle) are correlated with detailed metallurgical analysis. The fusion zone of dissimilar electron beam weld has finer grain size with a moderate evaporation and segregation of alloying elements magnesium and copper respectively. The mechanical properties of weld joint are controlled by optimum bead geometry and HAZ softening in weaker AA5083 Al alloy.
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Process parameters-weld bead geometry interactions and their influence on mechanical properties: A case of dissimilar aluminium alloy electron beam welds
Elsevier, 2018Co-Authors: P Mastanaiah, Abhay Sharma, Madhusudhan G ReddyAbstract:Prediction of weld bead geometry is always an interesting and challenging research topic as it involves understanding of complex multi input and multi output system. The weld bead geometry has a profound impact on the load bearing capability of a weld joint, which in-turn decides the performance in real time service conditions. The present study introduces a novel approach of detecting a relationship between weld bead geometry and mechanical properties (e.g. tensile load) for the purpose of catering the best the process could offer. The significance of the proposed approach is demonstrated by a case of dissimilar aluminium alloy (AA2219 and AA5083) electron beam welds. A mathematical model of tensile braking load as a function of geometrical attributes of weld bead geometry is presented. The results of investigation suggests the effective thickness of weld – a geometric parameter of weld bead has the most significant influence on tensile breaking load of dissimilar weld joint. The observations on bead geometry and the mechanical properties (microhardness, ultimate tensile load and face bend angle) are correlated with detailed metallurgical analysis. The fusion zone of dissimilar electron beam weld has finer grain size with a moderate evaporation and segregation of alloying elements magnesium and copper respectively. The mechanical properties of weld joint are controlled by optimum bead geometry and HAZ softening in weaker AA5083 Al alloy. Keywords: Electron beam welding, AA2219, AA5083, Bead geometry, Tensile breaking loa
