Thermally resettable laser transmission induced transparency in polymer waveguides at 635†nm.

Laser transmission induced transparency (LTIT) has been observed in a polymer waveguide using commercial perfluorinated acrylate-based materials when a continuous-wave laser at 635 nm is injected. The transmitted optical power increases continuously and follows a non-linear curve with respect to the laser injection time. Loss reduction over 13 dB is observed within 60 min at a moderate laser power of 5 mW. While higher injection power leads to a quicker change of the waveguide transparency, this loss reduction tends to saturate at a level irrelevant to the injection power. Further experiments demonstrate that a laser injection at 635 nm can also slightly improve the transparency at near-infrared wavelengths from 1500 nm to 1600 nm which is also the target wavelength range for this material. The state after a certain laser injection dose of 635 nm proves to be stable and the transmission characteristics of the polymer waveguide can be maintained and will continue after being stored at room temperature over a long period of time. By baking the waveguide at 200 °C for 20 min, the transparency property can be reset and the waveguide will return to the original high-loss state of 635 nm. These unique properties can be attributed to the photo-induced generation and thermally induced recombination of free radicals in the organic material. Our discovery may trigger interesting applications of polymer waveguides in the development of optical memory, clock, and encryption devices, beyond their target applications in optical communication.

Membrane-damaging activities of mannosylated ovalbumin are involved in its antibacterial action.

Mannosylated ovalbumin (Man-OVA) prepared by modification of carboxyl groups with p-aminophenyl α-d-mannopyranoside shows an increase of net positive charge, which may enhance its binding to bacterial membrane. Thus, we aimed to investigate whether Man-OVA exerts antibacterial activity on Escherichia coli and Staphylococcus aureus via membrane-perturbing effect. Man-OVA inhibited the growth of E. coli and S. aureus, whereas ovalbumin (OVA) did not show any antibacterial activity. Moreover, Man-OVA induced an increase in the membrane permeability of E. coli and S. aureus, which was positively correlated to its bactericidal action. Morphological examination using scanning electron microscopy revealed that Man-OVA disrupted the bacterial membrane integrity. Destabilization of the lipopolysaccharide (LPS) layer and inhibition of lipoteichoic acid (LTA) biosynthesis in the cell wall increased the bactericidal effect of Man-OVA. In contrast to OVA, Man-OVA also induced leakage of bacterial membrane-mimicking liposomes. Color transformation of phospholipid/polydiacetylene membrane assay revealed that the membrane-interaction mode of Man-OVA was distinct from that of OVA. LPS and LTA suppressed the membrane-damaging activity of Man-OVA, whereas an increase in the Man-OVA concentration attenuated the inhibitory action of LPS and LTA. Taken together, our data indicate that the bactericidal activity of Man-OVA depends strongly on its ability to induce membrane permeability.

The association of prolonged QT interval on electrocardiography and chronic lead exposure.

OBJECTIVES: The aim of this study was to examine the association of lead exposure with cardiac conduction disturbance among lead-exposed and nonexposed workers in Taiwan. METHODS: The participants comprised 312 lead workers and 329 referents who had no known occupational lead exposure. During their annual health examination, they were invited to take part in the survey. Standard resting 12-lead electrocardiograms were obtained and the electrocardiographic features studied were related to blood lead levels (BLLs). RESULTS: The mean BLLs were 26.05 (SD = 13.98) and 2.62 (SD = 1.42) µg/dL in lead-exposed and reference groups, respectively. Compared with the referents, lead workers had significantly shorter PR interval and longer QTc interval. Especially, workers with BLL > 30 µg/dL had the highest risk after adjusting for age, sex, body mass index, and other potential confounders. CONCLUSION: The data suggest that lead exposure is positively associated with prolonged QTc interval.