Effect of carbon nanotube amount on polyethylene welding process induced by laser source

This paper reports a study of the laser welding of polymeric joints composed by two polyethylene sheets, one pristine and the other filled by carbon nanotubes. In order to know the material modifications occurring during the laser exposure and the phenomena that seal the polymeric sheets, the physical, chemical and mechanical features of the welded area were analysed. The mechanical resistance of the welded joint and the structural changes of the polymer were checked by mechanical shear tests, absorption coefficient measurements, calorimetric analyses, mass quadrupole spectrometry and electron microscopy. The welding effectiveness was investigated as a function of the filler concentration.     

Design of Nanotechnological Carriers for Ocular Delivery of Mangiferin: Preformulation Study

(1) Background: Mangiferin (MGN) is a natural compound, showing anti-inflammatory and antioxidant activities for the potential treatment of eye diseases. The poor physicochemical features of MGN (low solubility and high instability) justify its nanoencapsulation into nanostructured lipid carriers (NLC) to improve its ocular bioavailability. (2) Methods: Firstly, MGN-NLC were prepared by the high shear homogenization coupled with the ultrasound (HSH−US) method. Finally, unloaded and MGN-loaded NLC were analyzed in terms of ocular tolerance. (3) Results: MGN-NLC showed good technological parameters suitable for ocular administration (particle size below 200 nm). The ORAC assay was performed to quantify the antioxidant activity of MGN, showing that the antioxidant activity of MGN-NLC (6494 ± 186 μM TE/g) was higher than that of the free compound (3521 ± 271 μM TE/g). This confirmed that the encapsulation of the drug was able to preserve and increase its activity. In ovo studies (HET-CAM) revealed that the formulation can be considered nonirritant. (4) Conclusions: Therefore, NLC systems are a promising approach for the ocular delivery of MGN.     

Shockwave and spallation in silver and other materials by sub-ns laser pulse at 1016 W/cm2 intensity

The laser spallation effect due to intense shockwaves caused by a brief and intense laser pulse irradiating a target surface, 2 mm thick, has been investigated for silver and other materials. For 300 ps IR laser pulse, at intensities of the order of 10¹⁶ W/cm², the shockwave may produce deformations of the back-face in ductile materials, such as Ag, Cu and Al. In heavy materials with high tensile strength, such as Ta, the shockwave produces cracks in the bottom of the laser crater but not deformation in the back-face, while in brittle materials, such as monocrystalline Ge, it produces only superficial cracks and flaking, but not deformation and spallation of the back-face. In thick polymeric materials, such as high-density polyethylene, the ablated crater shape is well defined and the shockwave is strongly damped, and no deformation has been observed in the back-face. The laser ablation yield and the ion acceleration in the backward direction have been measured by mass lost and time-of-flight measurements. SEM microscopy of the different irradiated targets, showing details of the crater size, edges, flaking and deformation in the back-face, useful for a discussion on the shockwave propagation and shock pressure calculation, is presented.     

Large deviations of Poisson shot noise processes under heavy tail semi-exponential conditions

In this note we provide a large deviation principle for Poisson shot noise processes under heavy tail semi-exponential conditions on the total shot per arrival. As in the light tail case, our result shows an insensitivity property of the model.     

Bounds in Total Variation Distance for Discrete-time Processes on the Sequence Space

Potential Analysis - Let $mathbb {P}$ and $widetilde {mathbb {P}}$ be the laws of two discrete-time stochastic processes defined on the sequence space $S^{mathbb N}$, where S is a finite set of...     

Symmetry methods in mathematical modeling of Aedes aegypti dispersal dynamics

A model of Aedes aegypti, the main vector of the yellow fever, is considered. The Lie point symmetries are found and some classes of exact solutions are shown.