Effects of Post Treatments on Bismuth-Doped and Bismuth/ Erbium Co-doped Optical Fibres

Bismuth-doped and bismuth/erbium co-doped optical fibres have attracted much attention for their great potential in the photonic applications at ultrawide O, E, S, C and L bands. The effects of post treatments, including various heating, high energy ray radiation, laser radiation and H2 loading processes, on these fibres’ performance, functionality and stability have been experimentally studied. Experimental results demonstrate that these post treatments could allow us to get insights regarding the formation and the structure of bismuth active centre (BAC) and be used to control and regulate the formation of BAC

High intrinsic sensitivity etched polymer fiber Bragg grating pair for simultaneous strain and temperature measurements

A sensing configuration for simultaneous measurement of strain and temperature with enhanced intrinsic sensitivity based on a fiber Bragg grating (FBG) pair with one grating inscribed in the etched and the other in unetched polymer fiber region is demonstrated. A poly (methyl methacrylate) based single-mode polymer fiber is etched to different diameters, and it is observed that etching can lead to change in the material properties of the fiber, such as Young\u27s modulus and thermal expansion coefficient, which can play a vital role in improving its intrinsic sensing capabilities. Thus, exploiting the different strain and temperature sensitivities exhibited by etched and unetched polymer FBGs, strain and temperature can be simultaneously measured with very high sensitivity. Experimental results show that rms deviations of ±8.42 μ∈ and ±0.39 °C for strain and temperature, respectively, in a real simultaneous measurement. The effect of individual thermal and strain sensitivity coefficients on measurement accuracy is also analyzed

Radiation Effect on Optical Properties of Bi-Related Materials Co-Doped Silica Optical Fibers

Three kinds of Bi-related materials co-doped silica optical fibers (BRDFs), including Bi/Al, Bi/Pb, and Bi/Er co-doped fibers, were fabricated using atomic layer deposition (ALD) and modified chemical vapor deposition (MCVD). Then, the effect of irradiation on the optical properties of BRDFs was investigated. The experimental results showed that the fluorescence intensity, the fluorescence lifetime of BRDFs at the 1150 nm band, increased significantly with low-dose treatment, whereas it decreased with a further increase in the radiation dose. In addition, the merit Mα values of the BRDFs, a ratio of useful pump absorption to total pump absorption, decreased with an increase of the radiation doses. The Verdet constants of different doped fibers increased up to saturation level with increases in the radiation dose. However, for a Bi-doped fiber, its Verdet constant decreased and the direction of Faraday’s rotation changed under low-dose radiation treatment. In addition, the Verdet constant increase of the Bi-doped silica fiber was much faster than that of other single mode fiber (SMF) and Pb-doped silica fibers treated with high-dose radiation. All of these findings are of great significance for the study of the optical properties of BRDFs

Local Microstructure Characterization of Rare Earth-Doped PMMA with Low-Ion Content by Fluorescence EXAFS

ABSTRACT: Fluorescence-extended X-ray absorption fine structure (EXAFS), and emission spectrum and excitation spectrum (ESES) were used to characterize the local structure of rare earth-doped poly(methyl methacrylate)s (RePMMAs) with ion concentration of 600 -1000 ppm

Dynamic placement of the linker histone H1 associated with nucleosome arrangement and gene transcription in early Drosophila embryonic development

The linker histone H1 is critical to maintenance of higher-order chromatin structures and to gene expression regulation. However, H1 dynamics and its functions in embryonic development remain unresolved. Here, we profiled gene expression, nucleosome positions, and H1 locations in early Drosophila embryos. The results show that H1 binding is positively correlated with the stability of beads-on-a-string nucleosome organization likely through stabilizing nucleosome positioning and maintaining nucleosome spacing. Strikingly, nucleosomes with H1 placement deviating to the left or the right relative to the dyad shift to the left or the right, respectively, during early Drosophila embryonic development. H1 occupancy on genic nucleosomes is inversely correlated with nucleosome distance to the transcription start sites. This inverse correlation reduces as gene transcription levels decrease. Additionally, H1 occupancy is lower at the 5\u27 border of genic nucleosomes than that at the 3\u27 border. This asymmetrical pattern of H1 occupancy on genic nucleosomes diminishes as gene transcription levels decrease. These findings shed new lights into how H1 placement dynamics correlates with nucleosome positioning and gene transcription during early Drosophila embryonic development