Noncollinear third-harmonic Maker fringes for the determination of third-order nonlinear optical susceptibilities.

We describe noncollinear third-harmonic Maker fringes for the determination of third-order optical nonlinearities. This method builds on the same principles as conventional Maker fringes experiments, but thanks to the limited interaction length of two intersecting beams, it allows to eliminate the requirement of taking into account the contribution of air to the third-harmonic signal. Thus, third-order susceptibilities can be accurately determined without the need for a vacuum chamber. We review the theoretical underpinnings of the method, and discuss the dependence of the coherence length for harmonic generation on the intersection angle between the beams and the sample orientation, and the effect this has on the Maker fringes pattern.

Development of antimicrobial coatings by atmospheric pressure plasma using a guanidine-based precursor.

Antimicrobial coatings deposited onto ultra high molecular weight polyethylene (UHMWPE) films were investigated using an atmospheric pressure - plasma enhanced chemical vapor deposition (AP-PECVD) process. Varying concentrations of a guanidine-based liquid precursor, 1,1,3,3-tetramethylguanidine, were used, and different deposition conditions were studied. Attenuated total reflectance - Fourier Transform Infrared (ATR-FTIR) spectroscopy and X-ray Photoelectron Spectroscopy (XPS) were used to study the chemical structure and elemental composition of the coatings. Conformity, morphology, and coating thickness were assessed through SEM and AFM. Optimal AP-PECVD parameters were chosen and applied to deposit guanidine coatings onto woven fabrics. The coatings exhibited high antimicrobial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) based on a modified-AATCC 100 test standard, where 2-5 log reductions were achieved.

Modification of silicon carbide surfaces by atmospheric pressure plasma for composite applications.

In this study, we explore the use of atmospheric pressure plasmas for enhancing the adhesion of SiC surfaces using a urethane adhesive, as an alternative to grit-blasting. Surface analysis showed that He-O2 plasma treatments resulted in a hydrophilic surface mostly by producing SiOx. Four-point bending tests and bonding pull tests were carried out on control, grit-blasted, and plasma-treated surfaces. Grit-blasted samples showed enhanced bonding but also a decrease in flexural strength. Plasma treated samples did not affect the flexural strength of the material and showed an increase in bonding strength. These results suggest that atmospheric pressure plasma treatment of ceramic materials is an effective alternative to grit-blasting for adhesion enhancement.