Nonlinear TE waves in a dielectric slab waveguide with two optically nonlinear layers

Properties of TE waves in a slab waveguide composed of five layers, including two Kerr-like nonlinear layers, are analyzed and examined. We find in particular the occurrence of an asymmetric mode, in addition to the expected symmetric and antisymmetric modes, though the waveguide geometry is symmetric. For the TE0symmetric mode, TE1antisymmetric and asymmetric modes, the dispersion curves, the relations between the effective index and the optical power density, and the variations of the transverse electric field patterns are illustrated and discussed in detail. As a result of this analysis, the regions in which the respective modes mainly reside are elucidated. We find that the effective index value of the symmetric mode at which the guide power vanishes is larger than that of the antisymmetric mode. For the case in which the effective indexes of the asymmetric and antisymmetric modes are identical, the power in the former mode is found to be larger than that in the latter.     

Natural tubule clay template synthesis of silver nanorods for antibacterial composite coating

Halloysite is naturally available clay mineral with hollow cylindrical geometry and it is available in thousands of tons. Silver nanorods were synthesized inside the lumen of the halloysite by thermal decomposition of the silver acetate, which was loaded into halloysite from an aqueous solution by vacuum cycling. Images of individual ca. 15 nm diameter silver nanorods and nanoparticles were observed with TEM. The presence of silver inside the tubes was also verified with STEM-EDX elemental mapping. Nanorods had crystalline nature with [111] axis oriented ~68° from the halloysite tubule main axis. The composite of silver nanorods encased in clay tubes with the polymer paint was prepared, and the coating antimicrobial activity combined with tensile strength increase was demonstrated. Coating containing up 5% silver loaded halloysite did not change color after light exposure contrary to the sample prepared with loading with unshelled silver nanoparticles. Halloysite tube templates have a potential for scalable manufacturing of ceramic encapsulated metal nanorods for composite materials.     

Influence of gas adsorption on optical transition energies of single-walled carbon nanotubes

The photoluminescence (PL) spectra of suspended single-walled carbon nanotubes (SWNTs) were measured in an ethanol gas atmosphere. When the gas pressure was decreased, the PL peaks were initially blue-shifted to a small extent before a rapid blue-shift took place at a transition pressure that depended on the temperature and diameter of the SWNT being measured. This pressure dependence is due to the adsorption of ethanol molecules on the SWNT surface. The optical transition energies measured below the transition pressure are intrinsic to the SWNT.     

Degradation of bisphenol A using sonochemical reactions

The sonochemical degradation of bisphenol A in aqueous solution, a suspected endocrine disruptor, which can cause several damages for humans, animals and the environment, was investigated at different ultrasonic intensities under air atmosphere. Bisphenol A (0.50mM) was completely degraded after 10, 3 and 2h of ultrasonic irradiation at a frequency of 404kHz, and intensities of 3.5, 9.0 and 12.9kW/m(2), respectively. During ultrasonic irradiation, some aromatic intermediates such as 2-(4-hydroxyphenyl)-2-(3,4-dihydroxyphenyl)propane, commonly known as 3-hydroxybisphenol A were detected. Further cleavage of the aromatic rings resulted in other products, like formaldehyde and organic acids, also being detected. The proposed pathways of bisphenol A degradation by ultrasonic irradiation are based on the above-mentioned intermediates. The relationship between bisphenol A degradation and formation of hydrogen peroxide and nitric acid was taken into account, correlating this to the radicals that take part in the degradation process. In order to optimize the performance of the ultrasonic system, additional experiments using Fenton-like reactions were also carried out. However, the addition of iron (II) sulfate (FeSO(4)) did not increase bisphenol A degradation rates. Compared with the system without iron (II) sulfate, the total organic carbon concentration (TOC) was reduced by about 30%, at 404kHz and 9.0kW/m(2).     

Tetraphenylporphyrin Enters the Ring: First Example of a Complex between Highly Bulky Porphyrins and a Protein**

Tetraphenylporphyrin (TPP) is a symmetrically substituted synthetic porphyrin whose properties can be readily modified, providing it with significant advantages over naturally occurring porphyrins. Herein, we report the first example of a stable complex between a native biomolecule, the haemoprotein HasA, and TPP as well as its derivatives. The X-ray crystal structures of nine different HasA-TPP complexes were solved at high resolutions. HasA capturing TPP derivatives was also demonstrated to inhibit growth of the opportunistic pathogen Pseudomonas aeruginosa. Mutant variants of HasA binding FeTPP were shown to possess a different mode of coordination, permitting the cyclopropanation of styrene.