Sub-nano resolution fiber-optic static strain sensor using a sideband interrogation technique

We propose a novel sideband interrogation technique with multiplex radio frequency intensity and phase modulation to measure the resonance frequency difference between two optical resonators. Based on this new technique, an ultrahighly sensitive fiber-optic static strain sensor system consisting of a pair of identical fiber Fabry-Perot interferometers is built by incorporating a cross-correlation data processing algorithm. A static strain resolution down to 0.8 nε is demonstrated experimentally, which makes the sensor system a useful tool for geophysical research applications.     

Nonlinear absorption microspectroscopy of single perylene nanocrystals with a multichannel double lock-in amplifier

Nonlinear confocal absorption microspectroscopy of single nanocrystals at low temperatures was introduced in the study of perylene nanocrystals. By the stationary pump-probe method, single nanocrystals were photoexcited into metastable excited states, and difference absorption spectra due to excited-state absorption and ground-state depletion were simultaneously recorded using a multichannel lock-in amplifier. It was revealed that the free Frenkel exciton band for single perylene nanocrystals is broader in width than that for the bulk crystal at low temperatures, suggesting that the exciton band is inhomogeneously broadened even for single perylene nanocrystals.     

Application of fourth‒order difference method to prediction of turbulence control in two‒dimensional channel with surface roughness

The fourth‒order finite difference method is combined with the vorticity–streamfunction formulation in generalized co‒ordinates. Direct numerical simulations are performed for channel flows with and without surface roughness at a Reynolds number of 10⁴. The present results are in good agreement with those of the pseudospectral method with respect to the flow in a smooth channel. It is shown that the present method predicts well the precise change in the flow with the channel length and roughness height. The turbulence is generally weakened by the roughness. Laminarization is also accomplished under the appropriate condition. © 1997 John Wiley & Sons, Ltd.     

Liquid Pressure Varifocus Lens

A liquid pressure varifocus lens that consists of a thin polymer film and liquid is described. The lens can be continuously changed from a concave to a convex shape by driving the liquid pressure in the lens. The dynamic range of the focal length of the convex lens is from 50 to 250 mm. A beam spot verifies the variable focal function on a photographic film exposed by a He-Ne laser. In addition, the application of the laser for processing is demonstrated to manufacture Fe compressed powder sheets by normal pulse YAG laser. Its melting marks along a focus change are formed with a minimum width of 0.1 mm.     

THE PHOTOREACTIONS AND PHOTOSENSITIVITY OF 3,4-DEHYDRO-BACTERIORHODOPSIN AT LOW TEMPERATURES

Abstract— The photoreaction of the artificial pigment synthesized from bacterioopsin and rrans-3,4-dehydro-retinal, [3,4-dehydro]bacteriorhodopsin ([3,4-deH]bR^t) was investigated with low temperature spectrophotometry.
The amount of batho-product formed from the light-adapted pigment of [3,4-deH]bR (designated as batho-[3,4-deH]bR^t) by irradiation at 77 K was much less than that from trans -bacteriorhodopsin (bR^t) and depends on temperature at irradiation of the sample. The kinetics of photoconversion of [3,4-deH]bR^t to batho-[3,4-deH]bR^t and that of its reversion were measured at several temperatures with a so-called "double Dewar system". The results showed that the photosensitivity of [3,4-deH]bR^t was temperature dependent. When batho-[3,4-deH]bR^t was warmed above 143 K, it was converted to lumi-[3,4-deH]bR^t. Lumi-[3,4-deH]bR^t was also produced by irradiation of [3,4-deH]bR^t at 143 or 163 K. The maximum in the difference spectrum between lumi-[3,4-deH]bR^t and [3,4-deH]bR^t was located at about 540 nm. The irradiation of [3,4-deH]bR^t at 183 K produced an intermediate analogous to meta-bR^t, but under similar conditions bR^t does not produce meta-bR^t. These results indicate that intermediates of [3,4-deH]bR^t are less stable than those of bR^t.
The differences between bacteriorhodopsin and [3,4-dehydro]bacteriorhodopsin were discussed and compared with the differences between rhodopsin and [3,4-dehydro]rhodopsin.