Ultrafast transient absorption spectra and kinetics of human blue cone visual pigment at room temperature.

The ultrafast photochemical reaction mechanism, transient spectra, and transition kinetics of the human blue cone visual pigment have been recorded at room temperature. Ultrafast time-resolved absorption spectroscopy revealed the progressive formation and decay of several metastable photo-intermediates, corresponding to the Batho to Meta-II photo-intermediates previously observed with bovine rhodopsin and human green cone opsin, on the picosecond to millisecond timescales following pulsed excitation. The experimental data reveal several interesting similarities and differences between the photobleaching sequences of bovine rhodopsin, human green cone opsin, and human blue cone opsin.

Spectroscopic analysis of bacterial photoreactivation.

With the rise of bacterial infections and antibiotic resistance, spectroscopic devices originally developed for bacterial detection have shown promise to rapidly identify bacterial strains and determine the ratio of live to dead bacteria. However, the detection of the photoreactivated pathogens remains a critical concern. This study utilizes fluorescence and Raman spectroscopy to analyze bacterial responses to UV irradiation and subsequent photoreactivation.

Ultrafast Transient Absorption Spectra and Kinetics of Rod and Cone Visual Pigments.

Rods and cones are the photoreceptor cells containing the visual pigment proteins that initiate visual phototransduction following the absorption of a photon. Photon absorption induces the photochemical transformation of a visual pigment, which results in the sequential formation of distinct photo-intermediate species on the femtosecond to millisecond timescales, whereupon a visual electrical signal is generated and transmitted to the brain. Time-resolved spectroscopic studies of the rod and cone photo-intermediaries enable the detailed understanding of initial events in vision, namely the key differences that underlie the functionally distinct scotopic (rod) and photopic (cone) visual systems.

Enhancing the upconversion efficiency of NaYF:Yb,Er microparticles for infrared vision applications.

In this study, (NaYF:Yb,Er) microparticles dispersed in water and ethanol, were used to generate 540 nm visible light from 980 nm infrared light by means of a nonlinear stepwise two-photon process. IR-reflecting mirrors placed on four sides of the cuvette that contained the microparticles increased the intensity of the upconverted 540 nm light by a factor of three. We also designed and constructed microparticle-coated lenses that can be used as eyeglasses, making it possible to see rather intense infrared light images that are converted to visible.

A novel approach for remote detection of bacteria using simple charge-coupled device cameras and telescope.

We have designed, constructed, and utilized a charge-coupled device system, integrated with a small Newtonian telescope, capable of long distance recording of bacterial fluorescence and synchronous spectra for the detection of bacteria, their component molecules, and other species. This newly developed optical system utilizes commercial monochrome cameras that we have used to detect various bacterial strains, such as Escherichia coli, and determine their concentrations. In addition, using this system, we were able to differentiate between live and dead bacteria after treatment with ultraviolet light or antibiotics.

Ultrafast time-resolved structural changes of thin-film ferromagnetic metal heated with femtosecond optical pulses.

As a classic ferromagnetic material, nickel has been an important research candidate used to study dynamics and interactions of electron, spin, and lattice degrees of freedom. In this study, we specifically chose a thick, 150 nm ferromagnetic nickel (111) single crystal rather than 10-20 nm thin crystals that are typically used in ultrafast studies, and we revealed both the ultrafast heating within the skin depth and the heat transfer from the surface (skin) layer to the bulk of the crystal. The lattice deformation after femtosecond laser excitation was investigated by means of 8.