Three-dimensional measurement of an inner surface profile using a supercontinuum beam.

We demonstrate an inner surface profile measurement that has a smooth spatial distribution. A supercontinuum beam suppresses the speckle contrast to 22% and the standard deviation of the point cloud to 40%, compared to equivalent values obtained by use of a conventional green He-Ne laser at a wavelength of 543.5 nm. A compact probe for the inner surface profile measurements using the supercontinuum beam measures the depth removed by wear of a small hole in an automobile component. The radial spatial resolution was evaluated to be 2 µm, which was of the same order as the wavelength of the supercontinuum beam. The supercontinuum beam enables fivefold improvement of the radial spatial resolution compared to the monochromatic wavelength beam because of a reduction in speckle effects.

Numerical Large Deviation Analysis of the Eigenstate Thermalization Hypothesis.

A plausible mechanism of thermalization in isolated quantum systems is based on the strong version of the eigenstate thermalization hypothesis (ETH), which states that all the energy eigenstates in the microcanonical energy shell have thermal properties. We numerically investigate the ETH by focusing on the large deviation property, which directly evaluates the ratio of athermal energy eigenstates in the energy shell. As a consequence, we have systematically confirmed that the strong ETH is indeed true even for near-integrable systems. Furthermore, we found that the finite-size scaling of the ratio of athermal eigenstates is a double exponential for nonintegrable systems. Our result illuminates the universal behavior of quantum chaos, and suggests that a large deviation analysis would serve as a powerful method to investigate thermalization in the presence of the large finite-size effect.

The role of the non-covalent ß-ionone-ring binding site in rhodopsin: historical and physiological perspective.

Bleached rhodopsin regenerates by way of the Schiff base formation between the 11-cis retinal and opsin. Recovery of human vision from light adapted states follows biphasic kinetics and each adaptive phase is assigned to two distinct classes of visual pigments in cones and rods, respectively, suggesting that the speed of Schiff base formation differs between iodopsin and rhodopsin. Matsumoto and Yoshizawa predicted the existence of a ß-ionone ring-binding site in rhodopsin, which has been proven by structural studies. They postulated that rhodopsin regeneration starts with a non-covalent binding of the ß-ionone ring moiety of 11-cis-retinal, followed by the Schiff base formation. Recent physiological investigation revealed that non-covalent occupation of the ß-ionone ring binding site transiently activates the visual transduction cascade in the dark. In order to understand the role of non-covalent binding of 11-cis-retinal to opsin during regeneration, we studied the kinetics of rhodopsin regeneration from opsin and 11-cis-retinal and found that the Schiff base formation is accelerated ∼10(7) times compared to that between retinal and free amine. According to Cordes and Jencks, Schiff base formation in solution exhibits a bell-shaped pH dependence. However, we discovered that the rhodopsin formation is independent of pH over a wide pH range, suggesting that aqueous solvents do not have access to the Schiff base milieu during its formation. According to Hecht et al. the regeneration of iodopsin must be significantly faster than that of rhodopsin. Does this suggest that the Schiff base formation in iodopsin is favored due to its structural architecture? The iodopsin structure once solved would answer such a question as how molecular fine-tuning of retinal proteins realizes their dark adaptive functions. In contrast, bacteriorhodopsin does not require occupancy of a distinct ß-ionone ring-binding site, enabling an aldehyde without the cyclohexene ring to form a pigment. Studies of regeneration reaction of other retinal proteins, which are scarcely available, would clarify the molecular structure-phenotype relationships and their physiological roles.

Determination of the polarization states of an arbitrary polarized terahertz beam: vectorial vortex analysis.

Vectorial vortex analysis is used to determine the polarization states of an arbitrarily polarized terahertz (0.1-1.6 THz) beam using THz achromatic axially symmetric wave (TAS) plates, which have a phase retardance of Δ = 163° and are made of polytetrafluorethylene. Polarized THz beams are converted into THz vectorial vortex beams with no spatial or wavelength dispersion, and the unknown polarization states of the incident THz beams are reconstructed. The polarization determination is also demonstrated at frequencies of 0.16 and 0.36 THz. The results obtained by solving the inverse source problem agree with the values used in the experiments. This vectorial vortex analysis enables a determination of the polarization states of the incident THz beam from the THz image. The polarization states of the beams are estimated after they pass through the TAS plates. The results validate this new approach to polarization detection for intense THz sources. It could find application in such cutting edge areas of physics as nonlinear THz photonics and plasmon excitation, because TAS plates not only instantaneously elucidate the polarization of an enclosed THz beam but can also passively control THz vectorial vortex beams.

Generation of achromatic, uniform-phase, radially polarized beams.

Axially symmetric half-wave plates have been used to generate radially polarized beams that have constant phase in the plane transverse to propagation. However, since the retardance introduced by these waveplates depends on the wavelength, it is difficult to generate radially polarized beams achromatically. This paper describes a technique suitable for the generation of achromatic, radially polarized beams with uniform phase. The generation system contains, among other optical components, an achromatic, axially symmetric quarter-wave plate based on total internal reflection. For an incident beam with a constant phase distribution, the system generates a beam with an extra geometrical phase term. To generate a beam with the correct phase distribution, it is therefore necessary to have an incident optical vortex with an azimuthally varying phase distribution of the form exp( + iθ). We show theoretically that the phase component of radially polarized beam is canceled out by the phase component of the incident optical vortex, resulting in a radially polarized beam with uniform phase. Additionally, we present an experimental setup able to generate the achromatic, uniform-phase, radially polarized beam and experimental results that confirm that the generated beam has the correct phase distribution.

Achromatic axially symmetric wave plate.

An achromatic axially symmetric wave plate (AAS-WP) is proposed that is based on Fresnel reflections. The wave plate does not introduce spatial dispersion. It provides retardation in the wavelength domain with an axially symmetric azimuthal angle. The optical configuration, a numerical simulation, and the optical properties of the AAS-WP are described. It is composed of PMMA. A pair of them is manufactured on a lathe. In the numerical simulation, the achromatic angle is estimated and is used to design the devices. They generate an axially symmetric polarized beam. The birefringence distribution is measured in order to evaluate the AAS-WPs.

Rhodopsin regeneration is accelerated via noncovalent 11-cis retinal-opsin complex--a role of retinal binding pocket of opsin.

The regeneration of bovine rhodopsin from its apoprotein opsin and the prosthetic group 11-cis retinal involves the formation of a retinylidene Schiff base with the epsilon-amino group of the active lysine residue of opsin. The pH dependence of a Schiff base formation in solution follows a typical bell-shaped profile because of the pH dependence of the formation and the following dehydration of a 1-aminoethanol intermediate. Unexpectedly, however, we find that the formation of rhodopsin from 11-cis retinal and opsin does not depend on pH over a wide pH range. These results are interpreted by the Matsumoto and Yoshizawa (Nature 258 [1975] 523) model of rhodopsin regeneration in which the 11-cis retinal chromophore binds first to opsin through the beta-ionone ring, followed by the slow formation of the retinylidene Schiff base in a restricted space. We find the second-order rate constant of the rhodopsin formation is 6100+/-300 mol(-1) s(-1) at 25 degrees C over the pH range 5-10. The second-order rate constant is much greater than that of a model Schiff base in solution by a factor of more than 10(7). A previous report by Pajares and Rando (J Biol Chem 264 [1989] 6804) suggests that the lysyl epsilon-NH(2) group of opsin is protonated when the beta-ionone ring binding site is unoccupied. The acceleration of the Schiff base formation in rhodopsin is explained by stabilization of the deprotonated form of the lysyl epsilon-NH(2) group which might be induced when the beta-ionone ring binding site is occupied through the noncovalent binding of 11-cis retinal to opsin at the initial stage of rhodopsin regeneration, followed by the proximity and orientation effect rendered by the formation of noncovalent 11-cis retinal-opsin complex.

pH- and temperature-sensitive release behaviors from polyelectrolyte complex films composed of chitosan and PAOMA copolymer.

This paper describes the pH and temperature effects on drug release from polyelectrolyte complex (PEC) films composed of a cationic polymer, chitosan, and an anionic polymer, polyalkyleneoxide-maleic acid copolymer (PAOMA). In this study, we prepared and investigated PEC films in terms of the drug release properties as pH- and temperature-sensitive drug carriers. Drug release rates were tested at pH 3.8 and 7.2, and at 25 and 50 degrees C. Salicylic acid and phenol were selected as model drugs. An increase in pH from 3.8 to 7.2 resulted in an increase in the rate of drug release because of the repulsive forces between carboxyl groups in PAOMA and anionic groups in model drugs. When the hydrophobic PAOMA was used as a polyanion, the drug release rate increased at 50 degrees C. This is attributed to the increase of release area due to the phase transition of PAOMA and the increase of repulsive forces between carboxyl groups in PAOMA and anionic groups in model drugs.