Cassini states for black hole binaries

Cassini states correspond to the equilibria of the spin axis of a body when its orbit is perturbed. They were initially described for planetary satellites, but the spin axes of black hole binaries also present this kind of equilibria. In previous works, Cassini states were reported as spin-orbit resonances, but actually the spin of black hole binaries is in circulation and there is no resonant motion. Here we provide a general description of the spin dynamics of black hole binary systems based on a Hamiltonian formalism. In absence of dissipation, the problem is integrable and it is easy to identify all possible trajectories for the spin for a given value of the total angular momentum. As the system collapses due to radiation reaction, the Cassini states are shifted to different positions, which modifies the dynamics around them. This is why the final spin distribution may differ from the initial one. Our method provides a simple way of predicting the distribution of the spin of black hole binaries at the end of the inspiral phase.

Curricular training report: pharmaceutical industry & spin-off company

O presente relatório expõe as atividades desenvolvidas durante o estágio curricular, frequentado na Bluepharma - Indústria Farmacêutica S.A. e na TREAT U, Lda. uma Spin-off da Universidade de Coimbra, no âmbito do Mestrado em Biomedicina Farmacêutica da Universidade de Aveiro. Esta foi uma experiência de 6 meses que teve duas componentes, uma multidisciplinar e outra monodisciplinar, as quais me permitiram desenvolver os conhecimentos e aptidões adquiridas ao longo do curso de mestrado e de as aplicar ao mundo real. Para além do desenvolvimento de competências profissionais, esta experiência possibilitou também a aquisição e desenvolvimento de várias aptidões, quer a nível pessoal como social. Nos primeiros dois meses desta minha experiência adquiri um conhecimento essencialmente teórico em várias áreas da indústria farmacêutica (financeira, desenvolvimento de negócio, assuntos regulamentares, investigação e desenvolvimento de medicamentos, garantia da qualidade, etc.) através da minha passagem pela Bluepharma. De seguida, na minha experiência de quatro meses na TREAT U, foi-me dada a oportunidade de realizar de forma mais independente, as funções inerentes ao cargo de assistente da gerência, com especial enfoque para atividades de gestão de projeto (incluindo assuntos regulamentares), tais como, apoio na preparação do plano de desenvolvimento não clínico e na preparação do pedido de aconselhamento científico. Este relatório começa assim por descrever os objectivos do estágio e uma breve descrição das instituições que me acolheram para a sua realização. De seguida, os conhecimentos adquiridos na vertente multidisciplinar do estágio e depois as atividades desenvolvidas no âmbito monodisciplinar. Por fim, apresenta uma análise das dificuldades e desafios encontrados bem como os esforços realizados para os ultrapassar.

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 (α, β and γ), Of special interest for various applications are non-centrosymmetric polymorphs: β-glycine and γ-glycine. The most useful β-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 β-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 β-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 β-glycine molecular systems by Piezoresponse Force Microscopy (PFM) and compare the results with molecular modeling and computer simulations. We show that β-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 β-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 β-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 β-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 β-glycine crystals in various applications are discussed in this work.