Biodiversity and molecular evolution of malacostraca

No actual cen��rio de perda acelerada de biodiversidade, o nosso conhecimento dos ecossistemas marinhos, apesar da sua extens��o e complexidade, continua muito inferior ao dos ecossistemas terrestres. A classe Malacostraca (Arthropoda, Crustacea), um grupo dos mais representativos nos ecossistemas marinhos, apresenta um elevado n��vel de diversidade morfol��gica e ecol��gica, mas dif��cil sua identifica����o ao n��vel de esp��cie requer frequentemente a ajuda de especialistas em taxonomia. A utiliza����o recente do ���barcoding��� (c��digo de barras do ADN), revelou ser um m��todo r��pido e eficaz para a identifica����o de esp��cies em diversos grupos de metazo��rios, incluindo os Malacostraca. No ��mbito desta tese foi constru��da uma base de dados de c��digo de barras de ADN envolvendo 132 esp��cies de Malacostraca v��rios locais de amostragem no Atl��ntico Nordeste e Mediterr��neo. As sequ��ncias de ADN mitocondrial provenientes de 601 esp��cimes formaram, em 95% dos casos, grupos congruentes com as identifica����es baseadas em caracter��sticas morfol��gicas. No entanto, foi detectado polimorfismo em seis casos e a diverg��ncia intra-espec��fica foi elevada em exemplares pertencentes a duas esp��cies morfol��gicas, sugerindo, neste caso, a ocorr��ncia de especia����o cr��ptica. Este estudo confirma a utilidade do c��digo de barras de ADN para a identifica����o de Malacostraca marinhos. Apesar do sucesso obtido, este m��todo apresenta alguns problemas, como por exemplo a poss��vel amplifica����o de pseudogenes. A ocorr��ncia de pseudogenes e as poss��veisabordagens para a detec����o e resolu����o deste tipo de problemas s��o discutidas com base em casos de estudo: an��lises dos c��digos de barras ADN na esp��cie Goneplax rhomboides (Crustacea, Decapoda). A an��lise dos c��digos de barras ADN revelou ainda grupos priorit��rios de dec��podes para estudos taxon��micos e sistem��ticos, nomeadamente os dec��podes dos g��neros Plesionika e Pagurus. Neste ��mbito s��o discutidas as rela����es filogen��ticas entre esp��cies seleccionadas dos g��neros Plesionika e Pagurus. Este trabalho aponta para v��rias quest��es no ��mbito da biodiversidade e evolu����o molecular da classe Malacostraca que carecem de um maior esclarecimento, podendo ser considerado como a base para estudo futuros. An��lises filogen��ticas adicionais integrando dados morfol��gicos e moleculares de um maior n��mero de esp��cies e de fam��lias dever��o certamente conduzir a uma melhor avalia����o da biodiversidade e da evolu����o dentro da classe.

Complete spin and orbital evolution of close-in bodies using a Maxwell viscoelastic rheology

In this paper, we present a formalism designed to model tidal interaction with a viscoelastic body made of Maxwell material. Our approach remains regular for any spin rate and orientation, and for any orbital configuration including high eccentricities and close encounters. The method is to integrate simultaneously the rotation and the position of the planet as well as its deformation. We provide the equations of motion both in the body frame and in the inertial frame. With this study, we generalize preexisting models to the spatial case and to arbitrary multipole orders using a formalism taken from quantum theory. We also provide the vectorial expression of the secular tidal torque expanded in Fourier series. Applying this model to close-in exoplanets, we observe that if the relaxation time is longer than the revolution period, the phase space of the system is characterized by the presence of several spin-orbit resonances, even in the circular case. As the system evolves, the planet spin can visit different spin-orbit configurations. The obliquity is decreasing along most of these resonances, but we observe a case where the planet tilt is instead growing. These conclusions derived from the secular torque are successfully tested with numerical integrations of the instantaneous equations of motion on HD 80606 b. Our formalism is also well adapted to close-in super-Earths in multiplanet systems which are known to have non-zero mutual inclinations.

Secular and tidal evolution of circumbinary systems

We investigate the secular dynamics of three-body circumbinary systems under the effect of tides. We use the octupolar non-restricted approximation for the orbital interactions, general relativity corrections, the quadrupolar approximation for the spins, and the viscous linear model for tides. We derive the averaged equations of motion in a simplified vectorial formalism, which is suitable to model the long-term evolution of a wide variety of circumbinary systems in very eccentric and inclined orbits. In particular, this vectorial approach can be used to derive constraints for tidal migration, capture in Cassini states, and stellar spin���orbit misalignment. We show that circumbinary planets with initial arbitrary orbital inclination can become coplanar through a secular resonance between the precession of the orbit and the precession of the spin of one of the stars. We also show that circumbinary systems for which the pericenter of the inner orbit is initially in libration present chaotic motion for the spins and for the eccentricity of the outer orbit. Because our model is valid for the non-restricted problem, it can also be applied to any three-body hierarchical system such as star���planet���satellite systems and triple stellar systems.

Piezoelectricity and ferroelectricity in amino acid glycine

Bioorganic ferroelectrics and piezoelectrics are becoming increasingly important in view of their intrinsic compatibility with biological environment and biofunctionality combined with strong piezoelectric effect and switchable polarization at room temperature. Here we study piezoelectricity and ferroelectricity in the smallest amino acid glycine, representing a broad class of non-centrosymmetric amino acids. Glycine is one of the basic and important elements in biology, as it serves as a building block for proteins. Three polymorphic forms with different physical properties are possible in glycine (��, �� and ��), Of special interest for various applications are non-centrosymmetric polymorphs: ��-glycine and ��-glycine. The most useful ��-polymorph being ferroelectric took much less attention than the other due to its instability under ambient conditions. In this work, we could grow stable microcrystals of ��-glycine by the evaporation of aqueous solution on a (111)Pt/Ti/SiO2/Si substrate as a template. The effects of the solution concentration and Pt-assisted nucleation on the crystal growth and phase evolution were characterized by X-ray diffraction analysis and Raman spectroscopy. In addition, spin-coating technique was used for the fabrication of highly aligned nano-islands of ��-glycine with regular orientation of the crystallographic axes relative the underlying substrate (Pt). Further we study both as-grown and tip-induced domain structures and polarization switching in the ��-glycine molecular systems by Piezoresponse Force Microscopy (PFM) and compare the results with molecular modeling and computer simulations. We show that ��-glycine is indeed a room-temperature ferroelectric and polarization can be switched by applying a bias to non-polar cuts via a conducting tip of atomic force microscope (AFM). Dynamics of these in-plane domains is studied as a function of applied voltage and pulse duration. The domain shape is dictated by both internal and external polarization screening mediated by defects and topographic features. Thermodynamic theory is applied to explain the domain propagation induced by the AFM tip. Our findings suggest that ��-glycine is a uniaxial ferroelectric with the properties controlled by the charged domain walls which in turn can be manipulated by external bias. Besides, nonlinear optical properties of ��-glycine were investigated by a second harmonic generation (SHG) method. SHG method confirmed that the 2-fold symmetry is preserved in as-grown crystals, thus reflecting the expected P21 symmetry of the ��-phase. Spontaneous polarization direction is found to be parallel to the monoclinic [010] axis and directed along the crystal length. These data are confirmed by computational molecular modeling. Optical measurements revealed also relatively high values of the nonlinear optical susceptibility (50% greater than in the z-cut quartz). The potential of using stable ��-glycine crystals in various applications are discussed in this work.