Evaluation of the Behavior of Two CAD/CAM Fiber-Reinforced Composite Dental Materials by Immersion Tests

Fiber-reinforced composites are used as restorative materials for prosthetic oral rehabilitation. Gastroesophageal reflux disease (GERD) is an accustomed affection with various oral manifestations. This study aimed to evaluate the behavior of two high-performance CAD/CAM milled reinforced composites (Trinia™, TriLor) in artificial saliva at different pH levels through immersion tests, and to determine if changes in mass or surface morphology at variable pH, specific for patients affected by GERD, appear. After investigating the elemental composition and surface morphology, the specimens were immersed in Carter Brugirard artificial saliva for 21 days at different pH values (5.7, 7.6, and varying the pH from 5.7 to 3). The values of the weighed masses during the immersion tests were statistically processed in terms of mean and standard deviation. Results suggested that irrespective of the medium pH, the two composites presented a similar mass variation in the range of −0.18 (±0.01)–1.82 (±0.02) mg after immersion, suggesting their stability when in contact with artificial saliva, an aspect which was also highlighted by scanning electron microscope (SEM) analysis performed on the immersed surfaces. Novel composite biomaterials can be a proper alternative for metal alloys used for prosthetic frameworks in patients suffering from GERD.

The Cohomological Genus and Symplectic Genus for 4-Manifolds of Rational or Ruled Types

An important problem in low dimensional topology is to understand the properties of embedded or immersed surfaces in 4-dimensional manifolds. In this article, we estimate the lower genus bound of closed, connected, smoothly embedded, oriented surfaces in a smooth, closed, connected, oriented 4-manifold with the cohomology algebra of a rational or ruled surface. Our genus bound depends only on the cohomology algebra rather than on the geometric structure of the 4-manifold. It provides evidence for the genus minimizing property of rational and ruled surfaces.

Anti-algal activity of the 12-5-12 gemini surfactant results from its impact on the photosynthetic apparatus

A rapid amplification of algal population has a negative impact on the environment and the global economy. Thus, control of algal proliferation is an important issue and effective procedures which reduce algal blooms and control algal fouling are highly desired. Gemini surfactants are considered to have a low environmental impact, therefore they seem to be a promising group of detergents which could reduce algal blooms in water systems. Furthermore, due to their emulsifying properties they could replace algaecides added to antifouling paints and decrease algae adhesion to various surfaces. In this study the toxic effect of the 12-5-12 gemini surfactant was investigated on Chlorella cells and close attention was paid to a potential mechanism of its action. At the high cell density (10.05 × 107 cells/mL) a dose-dependent cell death was found and the IC50 value was reached at the concentration of 19.6 µmol/L after 72-h exposure to the surfactant. The decrease in chlorophyll autofluorescence shows that the photosynthetic apparatus seems to be the target of the tested compound. The presented studies indicate that gemini surfactants could effectively reduce algal blooms in water systems, and if added to paints, they could decrease algal growth on external building walls or other water immersed surfaces.

Ridge energy for thin nematic polymer networks

Minimizing the elastic free energy of a thin sheet of nematic polymer network among smooth isometric immersions is the strategy purported by the mainstream theory. In this paper, we broaden the class of admissible spontaneous deformations: we consider ridged isometric immersions, which can cause a sharp ridge in the immersed surfaces. We propose a model to compute the extra energy distributed along such ridges. This energy comes from bending; it is shown under what circumstances it scales quadratically with the sheet’s thickness, falling just in between stretching and bending energies. We put our theory to the test by studying the spontaneous deformation of a disk on which a radial hedgehog was imprinted at the time of crosslinking. We predict the number of folds that develop in terms of the degree of order induced in the material by external agents (such as heat and illumination). Graphic Abstract

Topology of Surfaces with Finite Willmore Energy

In this paper, we study the critical case of the Allard regularity theorem. Combining with Reifenberg’s topological disk theorem, we get a critical Allard–Reifenberg-type regularity theorem. As a main result, we get the topological finiteness for a class of properly immersed surfaces in $\mathbb{R}^n$ with finite Willmore energy. Especially, we prove the removability of the isolated singularity of multiplicity one surfaces with finite Willmore energy and a uniqueness theorem of the catenoid under no a priori topological finiteness assumption.

On the Plateau-Douglas Problem for the Willmore energy of surfaces with planar boundary curves

For a smooth closed embedded planar curve, we consider the minimization problem of the Willmore energy among immersed surfaces of a given genus greater than 1 having the given curve as boundary, without any prescription on the conormal. By general lower bound estimates, in case the curve is a circle we prove that such problem is equivalent if restricted to embedded surfaces, we prove that do not exist minimizers, and we calculate the infimum. Then we study the case in which the genus is 1 and the competitors are restricted to a suitable class of varifolds including embedded surfaces, and we prove that the non-existence of minimizers implies a lower bound on the infimum; therefore we use such criterion in order to explicitly find an infinite family of curves for which such problem does have minimizers in the corresponding class of varifolds.