Estudio comparativo in vitro de la resistencia a la tracción y compresión en restauraciones estandarizadas realizadas conresinas compuestas v/s vidrio ionómero de alta densidad en dientes temporales

Tesis (Cirujano Dentista)Actualmente la odontología pediátrica tiene un enfoque orientado principalmente a la promoción de la salud oral y prevención de enfermedades orales prevalentes en niños. La enfermedad bucal más prevalente en la población infantil es la caries dental, la cual está directamente relacionada con factores de riesgo tales como la dieta, biofilm, factores salivales, exposición al flúor, factores conductuales, estructura dentaria y experiencia previa de caries, entre otros. Estudios epidemiológicos nacionales realizados en el año 2007 en niños de 6 años demuestran que la prevalencia de caries sigue siendo alta (70,36%) en comparación a la estadística obtenida en el año 1992 (70,8%)1. Otros estudios han demostrado que la prevalencia de este tipo de lesiones cariosas en pacientes pediátricos menores a 48 meses es de 35%, porcentaje que aumenta con la edad2. La Academia Americana de Odontología Pediátrica (AAPD) define caries temprana de la infancia a la presencia, en dientes temporarios, de 1 o más superficies cariadas (cavitadas o no), perdidas (por caries) u obturadas en niños menores de 71 meses de edad (5 años y 11 meses), por lo que en menores de 3 años, cualquier signo de caries en una superficie lisa, es indicativo de presencia de caries temprana de la infancia severa (CTIs)3. Sin embargo en la mayoría de los casos es indispensable restaurar estas lesiones debido al gran compromiso de estructura dentaria que ellas presentan. Es este el motivo por el cual se ha intentado buscar o generar a través de los avances científicos materiales compatibles con las características de los tejidos dentales. Dentro de los materiales restauradores estéticos para este tipo de lesiones encontramos vidrios ionómeros convencionales, vidrios ionómeros modificados con resinas, vidrios ionómeros de alta densidad y resinas compuestas. 5 Los vidrios ionómeros han ido evolucionando en el tiempo, mejorando sus propiedades. Actualmente los vidrios ionómeros de alta densidad (Ketac Molar EM, 3M-ESPE; Fuji IX GP, GC; Ionofil Molar ART, VOCO) permiten tiempos de trabajo más convenientes, mejor resistencia compresiva, resistencia flexural y al desgaste, junto con una solubilidad mínima, manteniendo su activación química4. Por otro lado las resinas compuestas tienen un lugar fundamental en la odontología restauradora debido a sus múltiples propiedades y variadas indicaciones. La disponibilidad de sistemas adhesivos eficaces ofrecen alternativas conservadoras a los tratamientos, proporcionando mejor durabilidad, resistencia y estética satisfactoria5. El siguiente estudio tiene como objetivo comparar la resistencia a la tracción y compresión in vitro de la resina compuesta v/s vidrio ionómero de alta densidad como material de restauración en preparaciones cavitarias estandarizadas en dientes temporales extraídos

Graphs with few trivial characteristic ideals

We give a characterization of the graphs with at most three trivial characteristic ideals. This implies the complete characterization of the regular graphs whose critical groups have at most three invariant factors equal to 1 and the characterization of the graphs whose Smith groups have at most 3 invariant factors equal to 1. We also give an alternative and simpler way to obtain the characterization of the graphs whose Smith groups have at most 3 invariant factors equal to 1, and a list of minimal forbidden graphs for the family of graphs with Smith group having at most 4 invariant factors equal to 1

Constructions of cospectral graphs with different zero forcing numbers

Several researchers have recently explored various graph parameters that can or cannot be characterized by the spectrum of a matrix associated with a graph. In this paper we show that several NP-hard zero forcing numbers are not characterized by the spectra of several types of associated matrices with a graph. In particular, we consider standard zero forcing, positive semidefinite zero forcing, and skew zero forcing, and provide constructions of infinite families of pairs of cospectral graphs which have different values for these numbers. We explore several methods for obtaining these cospectral graphs including using graph products, graph joins, and graph switching. Among these, we provide a construction involving regular adjacency cospectral graphs; the regularity of this construction also implies cospectrality with respect to several other matrices including the Laplacian, signless Laplacian, and normalized Laplacian. We also provide a construction where pairs of cospectral graphs can have an arbitrarily large difference between their zero forcing numbers

Antler velvet is thicker in adult than in yearling pampas deer (Ozotoceros bezoarticus): a histological study

Background: Antlers are lined by soft velvet tissue during antler growth. Later, the velvet is shed before rut onset. There are no detailed histological descriptions of the growing velvet, nor whether the velvet changes according to stag age. Our aims were to: 1) describe the basic histology of pampas deer antler velvet from adult and yearling males; and 2) determine the influence of age and time of antler growth on velvet’s tissues morphometry. Materials and methods: Samples were collected from 10 stags allocated in two groups, either adult (3–5 years old, n = 5) or yearling males (2 years old, n = 5). The day of antler cast was recorded for each animal. In spring, the stags were anaesthetised and velvet samples were collected from the third tine’s distal end. Samples were described qualitatively and a restricted morphometrical analysis of the antler velvet was performed. Results: The number of keratinocyte layers and the thicknesses of: total epidermis, corneum, intermediate and basale epidermal strata, total dermis, superficial and deep dermis were determined. Age and days after antler casting positively influenced in conjunction epidermal thickness (p = 0.037), and tended to influence both stratum intermedium (p = 0.076) and stratum corneum (p = 0.1) thicknesses. Age influenced stratum corneum thickness (p = 0.04). The pampas deer antler velvet lacked both sweat glands and arrector pili muscles. Conclusions: The deep dermis was densely irrigated but displayed abundant and well developed collagen bundles. Both total epidermal and stratum corneum thicknesses related positively to the age of the animals but were not to the time since antler cast.

The Strong Spectral Property of Graphs: Graph Operations and Barbell Partitions

The utility of a matrix satisfying the Strong Spectral Property has been well established particularly in connection with the inverse eigenvalue problem for graphs. More recently the class of graphs in which all associated symmetric matrices possess the Strong Spectral Property (denoted $G^{SSP}$) were studied, and along these lines we aim to study properties of graphs that exhibit a so-called barbell partition. Such a partition is a known impediment to membership in the class $G^{SSP}$. In particular we consider the existence of barbell partitions under various standard and useful graph operations

Solution and Asymptotic Behavior for a Nonlocal Coupled System of Reaction-Diffusion

This paper concerns with existence, uniqueness and asymptotic behavior of the solutions for a nonlocal coupled system of reaction-diffusion. We prove the existence and uniqueness of weak solutions by the Faedo-Galerkin method and exponential decay of solutions by the classic energy method. We improve the results obtained by Chipot-Lovato and Menezes for coupled systems. A numerical scheme is presented

Prioritized Sweeping Neural DynaQ with Multiple Predecessors, and Hippocampal Replays

During sleep and awake rest, the hippocampus replays sequences of place cells that have been activated during prior experiences. These have been interpreted as a memory consolidation process, but recent results suggest a possible interpretation in terms of reinforcement learning. The Dyna reinforcement learning algorithms use off-line replays to improve learning. Under limited replay budget, a prioritized sweeping approach, which requires a model of the transitions to the predecessors, can be used to improve performance. We investigate whether such algorithms can explain the experimentally observed replays. We propose a neural network version of prioritized sweeping Q-learning, for which we developed a growing multiple expert algorithm, able to cope with multiple predecessors. The resulting architecture is able to improve the learning of simulated agents confronted to a navigation task. We predict that, in animals, learning the world model should occur during rest periods, and that the corresponding replays should be shuffled.Comment: Living Machines 2018 (Paris, France

Ionic Liquid-Based Microemulsions in Catalysis

The design and properties of surface-active ionic liquids that are able to form stable microemulsions with heptane and water are presented, and their promise as reaction media for thermomorphic palladium-catalyzed cross-coupling reactions is demonstrated

Analycity and smoothing effect for the coupled system of equations of Korteweg - de Vries type with a single point singularity

We study that a solution of the initial value problem associated for the coupled system of equations of Korteweg - de Vries type which appears as a model to describe the strong interaction of weakly nonlinear long waves, has analyticity in time and smoothing effect up to real analyticity if the initial data only has a single point singularity at $x=0.