This investigation elucidates for the first time electrically controllable random lasers below the threshold voltage in dye-doped liquid crystal (DDLC) cells with and without adding an azo-dye. Experimental results show that the lasing intensities and the energy thresholds of the random lasers can be decreased and increased, respectively, by increasing the applied voltage below the Fréedericksz transition threshold. The below-threshold-electric-controllability of the random lasers is attributable to the effective decrease of the spatial fluctuation of the orientational order and thus of the dielectric tensor of LCs by increasing the electric-field-aligned order of LCs below the threshold, thereby increasing the diffusion constant and decreasing the scattering strength of the fluorescence photons in their recurrent multiple scattering. This can result in the decrease in the lasing intensity of the random lasers and the increase in their energy thresholds. Furthermore, the addition of an azo-dye in DDLC cell can induce the range of the working voltage below the threshold for the control of the random laser to reduce.
This study investigates, for the first time, an all-optically controllable random laser based on a dye-doped liquid crystal (DDLC) cell added with a photoisomerizable dye. Experimental results indicate that the lasing intensity of this random laser can be all-optically controlled to decrease and increase sequentially with a two-step exposure of one UV and then one green beam. All-optically reversible controllability of the random lasing emission is attributed to the isothermal nematic(N)-->isotropic(I) and I-->N phase transitions for LCs due to the UV-beam-induced trans-->cis and green-beam-induced cis-->trans back isomerizations of the photoisomerizable dye, respectively. The former and the latter can decrease and increase the spatial fluctuations of the order and thus of the dielectric tensor of LCs, respectively, subsequently increasing and decreasing the diffusion constant (or transport mean free path), respectively, and thus decaying and rising the scattering strength for the fluorescence photons in their recurrent multi-scattering process, respectively. The consequent decrease and increase of the lasing intensity for the random laser and thus the rise and descent of its energy threshold are generated, respectively.
To determine the expression of ␣ subunits and different isozymes of Na + ,K + -adenosine triphosphatase (ATPase) in human corneal endothelial cells (HCECs).Methods: Immunoblot and RNA analysis of Na + ,K + -ATPase ␣ subunit expression were performed in preparations from HCECs that had been immortalized by transformation with simian virus 40. Na + ,K + -ATPase activity was determined by constructing dose-response curves for the ouabain inhibition of Na + ,K + -ATPase activity in human corneal endothelial cells.Results: Both messenger RNA analysis and immunoblot studies indicated that HCECs express ATPase catalytic ␣1 and ␣3, but not ␣2 and ␣4, subunits. A limited amount of ␣3 subunit was expressed in HCECs compared with the ␣1 subunit. Biochemical analyses of Na + ,K + -ATPase activity revealed 2 independently active Na + ,K + -ATPase isoenzymes, a low-affinity site with a kinetic parameter for ouabain inhibition constant (K i ) in the micromolar range and a high-affinity site with a constant K i in the nanomolar range. These 2 sites may be associated with ␣1 and ␣3 isoforms, respectively, expressed in HCECs.Conclusions: Human corneal endothelial cells express ␣1 and ␣3 isoforms of Na + ,K + -ATPase, and both polypeptides are catalytically competent in these cells. Defining the components of Na + ,K + -ATPase in HCECs is an important step toward elucidating the mechanisms that regulate corneal endothelial ionic pump function as well as the pathogenesis of corneal diseases associated with corneal edema.
Excimer laser-based refractive surgery techniques have been the most popular forms to correct myopia, hyperopia, and astigmatism. However, development of non-excimer based refractive surgery such as thermal techniques provides a viable alternative to laser vision correction. Earlier forms of thermal techniques showed a lack of predictability and stability, resulting in the abandonment of the further development of these techniques. Recently, conductive keratoplasty, a laserless, radiofrequency-based technique, has been approved by the FDA for the correction of low to moderate hyperopia. Preliminary data showed that conductive keratoplasty seems to be safe, effective, and showed good refractive stability. This review will discuss recent studies on conductive keratoplasty technique in terms of its efficacy, safety, refractive predictability, and stability.
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