Efeitos do etil-cianoacrilato ou do octil-cianoacrilato sobre lesões corneais experimentais em coelhos

The use of ethyl-cyanoacrylate and octyl-cyanoacrylate were clinically and histopathologically compared on the corneas of 36 rabbits after lamellar keratectomy (standardized diameter and depth). The animals were distributed into two groups, one for each type of adhesive. From each group, six subgroups were histopathologically evaluated on the 3rd, 7th, 14th, 21st, 30th, and 60th day post-operative. General (daily) and ophthalmic (days 0, 1, 3, 5, 7, 14, 21, 30, 44, and 60) evaluations clinically indicated that there were significant differences for the variables water intake, attitude, blepharitis, corneal edema, and fluorescein test. The adhesive permanence time for octyl-cyanoacrylate (17.22 days) was greater than that for ethyl-cyanoacrylate (7.66 days). With respect to the histopathological evaluation, corneal epithelization and collagen organization occurred without severe complications. However, treatment with ethyl-cyanoacrylate led to a moderate inflammatory reaction in the initial phases. With octyl-cyanoacrylate, re-epithelization and collagen organization proceeded more slowly with a discrete inflammatory reaction in the initial phases. From clinical and histopathologic points of view, octyl-cyanoacrylate showed advantages over ethyl-cyanoacrylate, whereas wound healing was achieved in both groups without major complications.Comparou-se o uso do etil-cianoacrilato e do octil-cianoacrilato em córneas de 36 coelhos após ceratectomia lamelar (diâmetro e profundidade padronizados). Os animais foram distribuídos em dois grupos, segundo o tipo de adesivo, e redistribuídos em seis subgrupos com três animais cada, para as avaliações histológicas aos 3, 7, 14, 21, 30 e 60 dias de pós-operatório. As avaliações clínicas gerais (diárias) e as oftálmicas (dias 0, 1, 3, 5, 7, 14, 21, 30, 44 e 60), indicaram diferença entre os dois grupos, quanto ao consumo de água, atitude, blefarite, edema da córnea e teste da fluoresceína. O Tempo de permanência, sobre o leito corneal, do adesivo octil-cianoacrilato (17,22 dias), foi maior que o do etil-cianoacrulato (7,66 dias). A histopatologia, para ambos os grupos, mostrou que a re-epitelização e a organização do colágeno ocorreram sem graves intercorrências. O grupo tratado com o etil-cianoacrilato apresentou, nas fases iniciais, reação inflamatória mais evidente que o tratado com octil-cianoacrilato. Neste, a re-epitelização e a organização do colágeno ocorreram mais lentamente e com reação inflamatória discreta. Sob os pontos de vista clínico e de avaliação histológica simples, os resultados mostraram vantagens do octil-cianoacrilato, entretanto, a cicatrização da córnea ocorreu em ambos os grupos

A characterization of quadric constant mean curvature hypersurfaces of spheres

Let $\phi:M\to\mathbb{S}^{n+1}\subset\mathbb{R}^{n+2}$ be an immersion of a complete $n$-dimensional oriented manifold. For any $v\in\mathbb{R}^{n+2}$, let us denote by $\ell_v:M\to\mathbb{R}$ the function given by $\ell_v(x)=\phi(x),v$ and by $f_v:M\to\mathbb{R}$, the function given by $f_v(x)=\nu(x),v$, where $\nu:M\to\mathbb{S}^{n}$ is a Gauss map. We will prove that if $M$ has constant mean curvature, and, for some $v\ne{\bf 0}$ and some real number $\lambda$, we have that $\ell_v=\lambda f_v$, then, $\phi(M)$ is either a totally umbilical sphere or a Clifford hypersurface. As an application, we will use this result to prove that the weak stability index of any compact constant mean curvature hypersurface $M^n$ in $\mathbb{S}^{n+1}$ which is neither totally umbilical nor a Clifford hypersurface and has constant scalar curvature is greater than or equal to $2n+4$.Comment: Final version (February 2008). To appear in the Journal of Geometric Analysi

Curved Flats, Pluriharmonic Maps and Constant Curvature Immersions into Pseudo-Riemannian Space Forms

We study two aspects of the loop group formulation for isometric immersions with flat normal bundle of space forms. The first aspect is to examine the loop group maps along different ranges of the loop parameter. This leads to various equivalences between global isometric immersion problems among different space forms and pseudo-Riemannian space forms. As a corollary, we obtain a non-immersibility theorem for spheres into certain pseudo-Riemannian spheres and hyperbolic spaces. The second aspect pursued is to clarify the relationship between the loop group formulation of isometric immersions of space forms and that of pluriharmonic maps into symmetric spaces. We show that the objects in the first class are, in the real analytic case, extended pluriharmonic maps into certain symmetric spaces which satisfy an extra reality condition along a totally real submanifold. We show how to construct such pluriharmonic maps for general symmetric spaces from curved flats, using a generalised DPW method.Comment: 21 Pages, reference adde

Fast building – increasing the geometrical freedom of textile reinforced concrete systems

Apresentação efetuada na 9th International Conference Mechanics and Materials in Design - Theory, Experiments and Applications in Engineering (M2D2021), no Funchal, Portugal, 2022[Excerpt] Introduction Textile technology is highly innovative, and several techniques are already being used to act as building parts for fast building, interior design, architectural details and offshore structures. However, such potential still fails when complex geometrical structures or multifunctionality are required.Fundação para a Ciência e a Tecnologia - grant SFRH/BD/144201/2019European Regional Development Fund (FEDER), Operational Program for Competitiveness Factors (COMPETE) POCI-01-0247-312 FEDER-03973

Parabolic stable surfaces with constant mean curvature

We prove that if u is a bounded smooth function in the kernel of a nonnegative Schrodinger operator $-L=-(\Delta +q)$ on a parabolic Riemannian manifold M, then u is either identically zero or it has no zeros on M, and the linear space of such functions is 1-dimensional. We obtain consequences for orientable, complete stable surfaces with constant mean curvature $H\in\mathbb{R}$ in homogeneous spaces $\mathbb{E}(\kappa,\tau)$ with four dimensional isometry group. For instance, if M is an orientable, parabolic, complete immersed surface with constant mean curvature H in $\mathbb{H}^2\times\mathbb{R}$, then $|H|\leq 1/2$ and if equality holds, then M is either an entire graph or a vertical horocylinder.Comment: 15 pages, 1 figure. Minor changes have been incorporated (exchange finite capacity by parabolicity, and simplify the proof of Theorem 1)

Constructive and destructive use of compilers in elliptic curve cryptography

Although cryptographic software implementation is often performed by expert programmers, the range of performance and security driven options, as well as more mundane software engineering issues, still make it a challenge. The use of domain specific language and compiler techniques to assist in description and optimisation of cryptographic software is an interesting research challenge. In this paper we investigate two aspects of such techniques, focusing on Elliptic Curve Cryptography (ECC) in particular. Our constructive results show that a suitable language allows description of ECC based software in a manner close to the original mathematics; the corresponding compiler allows automatic production of an executable whose performance is competitive with that of a hand-optimised implementation. In contrast, we study the worrying potential for naïve compiler driven optimisation to render cryptographic software insecure. Both aspects of our work are set within the context of CACE, an ongoing EU funded project on this general topic

Topological and geometrical restrictions, free-boundary problems and self-gravitating fluids

Let (P1) be certain elliptic free-boundary problem on a Riemannian manifold (M,g). In this paper we study the restrictions on the topology and geometry of the fibres (the level sets) of the solutions f to (P1). We give a technique based on certain remarkable property of the fibres (the analytic representation property) for going from the initial PDE to a global analytical characterization of the fibres (the equilibrium partition condition). We study this analytical characterization and obtain several topological and geometrical properties that the fibres of the solutions must possess, depending on the topology of M and the metric tensor g. We apply these results to the classical problem in physics of classifying the equilibrium shapes of both Newtonian and relativistic static self-gravitating fluids. We also suggest a relationship with the isometries of a Riemannian manifold.Comment: 36 pages. In this new version the analytic representation hypothesis is proved. Please address all correspondence to D. Peralta-Sala

Densidade da madeira de árvores em savanas do norte da Amazônia brasileira

Densidade da madeira (DM) é uma variável importante para estimativas de estoques de carbono arbóreo em ecossistemas terrestres. Este tema é pobremente investigado em áreas de savana da Amazônia brasileira. O objetivo deste estudo foi investigar a DM das oito principais espécies arbóreas que ocorrem na savana aberta de Roraima, a maior área de savana do norte do bioma Amazônia. Foram verificadas as variações na DM em função da espécie e dos diferentes diâmetros observados ao longo da dimensão vertical de 75 indivíduos amostrados em seis sítios de coleta. Foi utilizado o método direto para obtenção de peças de madeira do fuste e da copa. Os resultados indicaram discrepância significativa interespecífica, sendo Roupala montana Aubl. a espécie de maior DM média (0,674 g cm-3). Foi detectado que existe variação significativa da DM entre as peças do fuste e da copa, independente da espécie e do sítio de coleta. A densidade da madeira de peças da copa com diâmetro entre 5 e 10 cm pode ser utilizada como preditora da DM média do indivíduo arbóreo. Nós concluimos que a DM das oito espécies arbóreas investigadas possui variabilidade interespecífica, com discrepâncias entre a DM do fuste e das partes lenhosas da copa. As distinções aqui detectadas devem ser considerados como uma importante ferramenta para melhorar as estimativas de estoque de carbono em áreas de savanas na Amazônia