Is the meander growth in the Brazil Current system off Southeast Brazil due to baroclinic instability?

Temporally-growing frontal meandering and occasional eddy-shedding is observed in the Brazil Current (BC) as it flows adjacent to the Brazilian Coast. No study of the dynamics of this phenomenon has been conducted to date in the region between 22 degrees S and 25 degrees S. Within this latitude range, the flow over the intermediate continental slope is marked by a current inversion at a depth that is associated with the Intermediate Western Boundary Current (IWBC). A time series analysis of 10-current-meter mooring data was used to describe a mean vertical profile for the BC-IWBC jet and a typical meander vertical structure. The latter was obtained by an empirical orthogonal function (EOF) analysis that showed a single mode explaining 82% of the total variance. This mode structure decayed sharply with depth, revealing that the meandering is much more vigorous within the BC domain than it is in the IWBC region. As the spectral analysis of the mode amplitude time series revealed no significant periods, we searched for dominant wavelengths. This search was done via a spatial EOF analysis on 51 thermal front patterns derived from digitized AVHRR images. Four modes were statistically significant at the 95% confidence level. Modes 3 and 4, which together explained 18% of the total variance, are associated with 266 and 338-km vorticity waves, respectively. With this new information derived from the data, the [Johns, W.E., 1988. One-dimensional baroclinically unstable waves on the Gulf Stream potential vorticity gradient near Cape Hatteras. Dyn. Atmos. Oceans 11, 323-350] one-dimensional quasi-geostrophic model was applied to the interpolated mean BC-IWBC jet. The results indicated that the BC system is indeed baroclinically unstable and that the wavelengths depicted in the thermal front analysis are associated with the most unstable waves produced by the model. Growth rates were about 0.06 (0.05) days(-1) for the 266-km (338-km) wave. Moreover, phase speeds for these waves were low compared to the surface BC velocity and may account for remarks in the literature about growing standing or stationary meanders off southeast Brazil. The theoretical vertical structure modes associated with these waves resembled very closely to the one obtained for the current-meter mooring EOF analysis. We interpret this agreement as a confirmation that baroclinic instability is an important mechanism in meander growth in the BC system. (C) 2008 Elsevier B.V. All rights reserved.

Low cost 3D global instability analysis and flow sensitivity based on dynamic mode decomposition and high-order numerical tools

We explore the recently developed snapshot-based dynamic mode decomposition (DMD) technique, a matrix-free Arnoldi type method, to predict 3D linear global flow instabilities. We apply the DMD technique to flows confined in an L-shaped cavity and compare the resulting modes to their counterparts issued from classic, matrix forming, linear instability analysis (i.e. BiGlobal approach) and direct numerical simulations. Results show that the DMD technique, which uses snapshots generated by a 3D non-linear incompressible discontinuous Galerkin Navier?Stokes solver, provides very similar results to classical linear instability analysis techniques. In addition, we compare DMD results issued from non-linear and linearised Navier?Stokes solvers, showing that linearisation is not necessary (i.e. base flow not required) to obtain linear modes, as long as the analysis is restricted to the exponential growth regime, that is, flow regime governed by the linearised Navier?Stokes equations, and showing the potential of this type of analysis based on snapshots to general purpose CFD codes, without need of modifications. Finally, this work shows that the DMD technique can provide three-dimensional direct and adjoint modes through snapshots provided by the linearised and adjoint linearised Navier?Stokes equations advanced in time. Subsequently, these modes are used to provide structural sensitivity maps and sensitivity to base flow modification information for 3D flows and complex geometries, at an affordable computational cost. The information provided by the sensitivity study is used to modify the L-shaped geometry and control the most unstable 3D mode.

Highly polymorphic microsatellite markers for the Mediterranean endemic fan mussel Pinna nobilis

Pinna nobilis is an endemic bivalve of the Mediterranean Sea whose populations have decreased in the last decades due to human pressure; as a consequence, it was declared a protected species in 1992. Despite its conservation status, few genetic studies using mitochondrial markers have been published. We report on the isolation and development of 10 microsatellite loci for the fan mussel, Pinna nobilis. All loci (2 di-nucleotide, 5 tri-nucleotide, 2 tetra-nucleotide and 1 penta-nucleotide) are characterized by high levels of polymorphism in 76 individuals tested from two populations in the Balearic Islands (Spain, Western Mediterranean Sea). The number of alleles ranged from 4 to 24 and expected heterozygosity ranged from 0.4269 to 0.9400. These microsatellites could be very useful for the assessment of the genetic diversity and connectivity patterns of P. nobilis and the establishment of new conservation strategies.

Genetic evidence for polygynandry in the black-striped pipefish syngnathus abaster: a microsatellite-based parentage analysis

Sexual selection theory predicts that, in organisms with reversed sex roles, more polyandrous species exhibit higher levels of sexual dimorphism. In the family Syngnathidae (pipefish, seahorses, and seadragons), males provide all parental care by carrying developing embryos on their ventral surfaces, and females develop secondary sex characters. Syngnathids exhibit a variety of genetic mating patterns, making them an ideal group to test predictions of sexual selection theory. Here, we describe the mating system of the black-striped pipefish Syngnathus abaster, using 4 highly variable microsatellites to analyze parentage of 102 embryos. Results revealed that 1) both sexes mate multiple times over the course of a pregnancy (polygynandrous mating system), 2) eggs are spatially segregated by maternity within each brood pouch, and 3) larger females have higher mating success (Kolmogorov–Smirnov test; P < 0.05). Together with similar studies of other syngnathid species, our results support the hypothesis that the mating system is related to the intensity of sexual dimorphism.

Characterization of 10 new tetranucleotide microsatellite markers for the European eagle owl, Bubo bubo: Useful tools for conservation strategies

Bubo bubo is the largest owl in the world, showing a wide geographical distribution throughout the Palaearctic region. It underwent a demographic decline in many European countries during the last century and was considered “vulnerable” (Annex II of the CITES). Nowadays, it is classified as “Least Concern” according to IUCN. Despite its ecological importance and conservation status, few polymorphic molecular markers are available to study its diversity and population genetics. We report on the isolation and development of 10 new microsatellites for the Eagle owl, B. bubo. All loci (10 tetra-nucleotide) are characterized by high polymorphism levels. Number of alleles ranged from 5 to 13 and expected heterozygosity varied from 0.733 to 0.840. These microsatellites would be very useful to assess the genetic diversity, connectivity patterns and parentage of B. bubo. This information will allow to establish new conservation strategies and improve the management of the species.

Is financial instability male-driven? Gender and cognitive skills in experimental asset markets

The hypothesis that price stability would reliably increase with the fraction of women operating in financial markets has been frequently suggested in policy discussions. To test this hypothesis we conducted 10 male-only, 10 female-only and 10 mixed-gender experimental asset markets, and compared the effects of gender composition, confidence, risk attitude and cognitive skills. Male and female markets have comparable volatility and deviations from fundamentals, whereas mixed-gender markets are substantially more stable. On the other hand, higher average cognitive skills of the group are associated with reduced market volatility. Individual-level analysis shows that subjects with higher cognitive skills trade at prices closer to fundamental values and earn significantly higher profits; similarly, mixed markets exhibit lower mispricing, particularly for traders with lower cognitive skills. Our results are demonstrated to hold in other experimental asset market studies, suggesting that a mixed-gender composition reduces mispricing across different types of asset markets.

Transcriptome analysis of Euterpe edulis and identification of microsatellite markers.

2016

Microsatellite analysis of pacu broodstocks used in the stocking program of Paranapanema River, Brazil

O monitoramento da diversidade genética é fundamental em um programa de repovoamento. Avaliouse a diversidade genética de pacu Piaractus mesopotamicus (Holmberg, 1887) em duas estações de piscicultura em Andirá -Paraná, Brasil, utilizadas no programa de repovoamento do Rio Paranapanema. Foram amplificados seis loci microssatélite para avaliar 60 amostras de nadadeira. O estoque de reprodutores B apresentou maior número de alelos e heterozigose (alelos: 22 e H O: 0,628) que o estoque de reprodutores A (alelos: 21 e H O: 0,600). Alelos com baixos níveis de frequência foram observados nos dois estoques. Os coeficientes positivos de endogamia no locus Pme2 (estoque A: F IS = 0,30 e estoque B: F IS = 0,20), Pme5 (estoque B: F IS = 0,15), Pme14 (estoque A: F IS = 0,07) e Pme28 (estoque A: F IS = 0,24 e estoque B: F IS = 0,20), indicaram deficiência de heterozigotos. Foi detectada a presença de um alelo nulo no lócus Pme2. As estimativas negativas nos loci Pme4 (estoque A: F IS = -0,43 e estoque B: F IS= -0,37), Pme5 (estoque A: F IS = - 0,11), Pme14 (estoque B: F IS = - 0,15) e Pme32 (estoque A: F IS = - 0,93 e estoque B: F IS = - 0,60) foram indicativas de excesso de heterozigotos. Foi evidenciado desequilíbrio de ligação e riqueza alélica baixa só no estoque A. A diversidade genética de Nei foi alta nos dois estoques. A distância (0,085) e identidade (0,918) genética mostraram similaridade entre os estoques, o qual reflete uma possível origem comum. 6,05% da variância genética total foi devida a diferenças entre os estoques. Foi observado um recente efeito gargalo nos dois estoques. Os resultados indicaram uma alta diversidade genética nos estoques de reprodutores e baixa diferenciação genética entre eles, o que foi causado pelo manejo reprodutivo das pisciculturas, redução do tamanho populacional e intercâmbio genético entre as pisciculturas.

Mathematical models for cellular aggregation: the chemotactic instability and clustering formation

In this thesis we present a mathematical formulation of the interaction between microorganisms such as bacteria or amoebae and chemicals, often produced by the organisms themselves. This interaction is called chemotaxis and leads to cellular aggregation. We derive some models to describe chemotaxis. The first is the pioneristic Keller-Segel parabolic-parabolic model and it is derived by two different frameworks: a macroscopic perspective and a microscopic perspective, in which we start with a stochastic differential equation and we perform a mean-field approximation. This parabolic model may be generalized by the introduction of a degenerate diffusion parameter, which depends on the density itself via a power law. Then we derive a model for chemotaxis based on Cattaneo's law of heat propagation with finite speed, which is a hyperbolic model. The last model proposed here is a hydrodynamic model, which takes into account the inertia of the system by a friction force. In the limit of strong friction, the model reduces to the parabolic model, whereas in the limit of weak friction, we recover a hyperbolic model. Finally, we analyze the instability condition, which is the condition that leads to aggregation, and we describe the different kinds of aggregates we may obtain: the parabolic models lead to clusters or peaks whereas the hyperbolic models lead to the formation of network patterns or filaments. Moreover, we discuss the analogy between bacterial colonies and self gravitating systems by comparing the chemotactic collapse and the gravitational collapse (Jeans instability).

Genetic diversity of mango accessions (Mangifera indica) using new microsatellite markers and morphological descriptors.

Genetic diversity estimates based on morphological and molecular data can provide different information on the relationship between cultivars of a species. This study aimed to develop new microsatellite markers as additional tools in genetic studies on mangoes (Mangifera indica L.), and to analyze the genetic variability of 20 mango cultivars based on morphological descriptors and microsatellite markers. We aimed to better understand the cultivars enhanced breeding histories and to support crossbreeding planning. Positive clones were selected from a DNA library enriched for microsatellite regions for sequencing and primer design. Four plants of each of the 20 accessions were used for observations, based on 48 morphological descriptors. Twenty accessions were analyzed using 27 microsatellite markers, of which 16 were developed during this study. The clusters, based on the morphological descriptors by Ward - MLM strategy and the microsatellite markers, suggested that Brazilian mango cultivars have extensive genetic diversity and are related to cultivars with different provenances, demonstrating their different enhanced breeding histories.

Polymorphic microsatellite loci from the endangered Giant Otter (Pteronura brasiliensis).

We describe the first microsatellite loci isolated from the giant otter (Pteronura brasiliensis), an endangered mustelid endemic to South America. Fourteen di- and trinucleotide polymorphic loci were characterised in fourteen individuals from the Pantanal wetlands, Central Brazil. Number of alleles per locus ranged from 2 to 5, and average observed heterozygosity was 0.577. Two loci were in linkage disequilibrium, and one further locus deviated from Hardy?Weinberg equilibrium, probably due to the presence of null alleles. The transferability of these markers to two other mustelids (Lontra longicaudis and Eira barbara) and to the mephitid Conepatus semistriatus was also evaluated. These loci are useful to study the ecology and evolution of these species.

Linear and nonlinear thermal instability of Newtonian and non-Newtonian fluid saturated porous media

The present work aims to investigate the influence of different aspects, such as non-standard steady solutions, complex fluid rheologies and non-standard porous-channel geometries, on the stability of a Darcy-Bénard system. In order to do so, both linear and nonlinear stability theories are considered. A linear analysis focuses on studying the dynamics of the single disturbance wave present in the system, while its nonlinear counterpart takes into consideration the interactions among the single modes. The scope of the stability analysis is to obtain information regarding the transition from an equilibrium solution to another one, and also information regarding the transition nature and the emergent solution after the transition. The disturbance governing equations are solved analytically, whenever possible, and numerical by considering different approaches. Among other important results, it is found that a cylinder cross-section does not affect the thermal instability threshold, but just the linear pattern selection for dilatant and pseudoplastic fluid saturated porous media. A new rheological model is proposed as a solution for singular issues involving the power-law model. Also, a generalised class of one parameter basic solutions is proposed as an alternative description of the isoflux Darcy--Bénard problem. Its stability is investigated.

Deep space orbit determination and guidance of the LICIACube microsatellite mission

Recently, the JPL's MarCO mission demonstrated that these probes are also mature enough to be employed in the deep space, even though with the limitations related to the employed commercial components. Currently, other deep space CubeSats are planned either as stand-alone missions or as companions of a traditional large probe. Therefore, developing a dedicated navigation suite is crucial to reaching the mission's goals, considering the limitations of the onboard components compared to typical deep space missions. In this framework, the LICIACube mission represents an ideal candidate test-bench, as it performs a flyby of the Didymos asteroid system subject to a strong position, epochs, and pointing requirements. This mission will also allow us to infer the capabilities of such microsatellites and highlight their limitations compared with the benefits of a lighter design and tailoring efforts. In this work, the OD and guidance methods and tools adopted for classical deep space missions have been tailored for the CubeSat applications and validated through extensive analyses. In addition, navigation procedures and interfaces have been designed in view of the operations foreseen in late 2022. The pre-launch covariance analysis has been performed to assess the mission's feasibility for the nominal trajectory and its associated uncertainties, based on conservative assumptions on the main parameters. Extensive sensitivity analyses have been carried out to understand the main mission parameters affecting the performance and to demonstrate the robustness of the designed trajectory and operation schedule in fulfilling the mission requirements. The developed system was also stressed by tuning the models to access different reconstruction methods for the maneuvers. The analysis demonstrated the feasibility of the LICIACube mission navigation in compliance with the mission requirements, compatible with the limited resources available, both in space and on the ground.

Nuclear shape instability caused by lamin A deregulation promotes invasiveness in pediatric bone sarcomas: from nucleo-cytoskeleton dynamics to novel therapeutic opportunities

Osteosarcoma (OS) and Ewing sarcoma (EWS) are the two most frequent primary bone tumors, in which metastases remain the most relevant adverse prognostic factor. Lamin A is the main constituent of the nuclear lamina, with a fundamental role in maintaining the connection between nucleus and cytoskeleton (through LINC complex proteins interactions), and its alterations can be implicated in tumor progression. We investigated how nucleo-cytoskeleton dynamics is influenced by lamin A modulation in OS and EWS, demonstrating that both these cancer models had low levels of lamin A, which are linked to a significantly more marked nuclear misshaping. In our in vitro studies, reduced levels of lamin A promoted migratory abilities in these tumors. Moreover, these findings were corroborated by gene expression analyses on EWS patient samples, showing that LMNA levels were significantly lower in metastatic lesions compared to primary tumors and that patients with low LMNA had a significant worse overall survival. We also found that LMNA expression significantly impaired EWS metastases formation in vivo. We demonstrated that low lamin A expression was linked to a severe mislocalization of LINC complex proteins, thus disrupting nucleo-cytoskeleton interactions, with a corresponding gain in malignant properties, which resulted in increased invasiveness. Lamin A overexpression or its accumulation by a statin-based pharmacological treatment allowed us to reconstitute a functional nucleo-cytoskeleton interplay, which resulted in significant downmodulation of ROCK2 and YAP, two crucial drivers of EWS aggressiveness. Our study demonstrated that lamin A is a favorable mediator of nuclear shape stability in bone sarcomas, and its modulation rescues LINC complex protein localization and regulates mechano-signaling pathways, thus promoting a less aggressive cancer phenotype. We also identified statins, already employed in clinical practice, as a tool capable to increase lamin A levels, and to reconstitute functional nucleo-cytoskeletal dynamics, resulting in reduced cellular migration.

Experimental and numerical characterization of flame instability in hydrogen-containing flames

In the framework of the energy transition, the acquisition of proper knowledge of fundamental aspects characterizing the use of alternative fuels is paramount as well as the development of optimized know-how and technologies. In this sense, the use of hydrogen has been indicated as a promising route for decarbonization at the end-users stage in the energy supply chain. However, the elevated reactivity and the low-density at atmospheric conditions of hydrogen pose new challenges. Among the others, the dilution of hydrogen with carbon dioxide from carbon capture and storage systems represents a possible route. However, the interactions between these species have been poorly studied so far. For these reasons, this thesis, in collaboration between the University of Bologna and Technische Universität Bergakademie of Freiberg in Saxony (Germany), investigates the laminar flame of hydrogen-based premixed gas with the dilution of carbon dioxide. An experimental system, called a heat flux burner, was adopted ad different operating conditions. The presence of the cellularity phenomenon, forming the so-called cellular flame, was observed and analysed. Theoretical and visual methods have allowed for the characterization of the investigated flames, opening new alternatives for sustainable energy production via hydrogen transformation.