Local plasmon sensor with gold colloid monolayers deposited upon glass substrates

A new optical sensor that uses local plasmon resonance is proposed. A peak that is due to the local plasmon resonance appears in the absorption spectrum of a gold colloid suspension in the visible region, and its height and wavelength depend on the refractive index of the suspension. These properties are used for optical sensors. We used gold colloid monolayers in which colloidal gold particles a few tens of nanometers in diameter were immobilized upon a glass slide by a functional organic coupling agent. We measured the absorption spectra of the the gold colloid monolayers, which were immersed in liquid samples or coated with thin films. We observed increases of both the resonance wavelength and the absorbance as the refractive indices of the sample liquids or the thickness of the coated films increased. The proportional constants of the resonance wavelength to the film thickness were 3.6 and 5.7 for a 13.9- and a 20.2-nm gold colloid monolayer, respectively.     

Radiator effect on plastic nuclear track detectors for high-energy neutrons

The effect of radiators supplying charged particles to plastic nuclear track detectors has been investigated both experimentally and theoretically in order to apply them to personal dosimeters for high-energy neutrons. Performance of four types of radiator materials, CH₂, CD₂ (deuterized hydrocarbon), LiF (lithium fluoride) and C (graphite), was checked in a quasi-monoenergetic neutron field generated by p-Li reactions. The efficiency has been numerically calculated based on a model with a special attention to the angular dependence of cross sections and data of characteristic response to light ions. The effect of respective radiator candidates has been evaluated as a function of the neutron energy. A two-layer radiator has also been proposed to adjust the energy dependence of the relative sensitivity to conversion factor for dose-equivalent.     

Spectrophotometric determination of urinary protein with o-sulfophenylfluorone-metal complex.

A simple and sensitive spectrophotometric method for the determination of human serum albumin (HSA) was established based on the ternary complex-formation reaction of HSA with o-sulfophenylfluorone (SPF) as a xanthene dye and metal ion (niobium(V) and bismuth(III)) in the presence of a dispersion agent. This new method enabled the determination of HSA in the range of 1 - 15 microg/ml HSA by measuring the difference of the absorbance at 530 nm between HSA-SPF-metal ion and SPF-metal ion solutions. In the determination of HSA, this method is about 2-times more sensitive than the Pyrogallol Red-molybdenum(VI) method (PR method), which accounts for more than 80% of the quantification methods for urinary protein assays in Japan. There was no significant difference between the results obtained by the present method and the PR method for human urine samples. The binding process between the SPF-metal complex and HSA was studied by determining the binding parameters and the thermodynamic parameters.     

Mössbauer and infrared investigation of reactions of laser-evaporated iron atoms with ethylene

Reactions of laser-evaporated iron atoms with ethylene molecules were investigated. The reaction products were trapped in a low-temperature matrix observed by Mössbauer and infrared spectroscopies. Fe(C₂H₄) was produced at low ethylene concentration, and Fe(C₂H₄)₂ was obtained as the major product at higher ethylene concentration. The assignments were confirmed through molecular orbital calculations.     

Theory of spin reorientation in rare-earth orthochromites and orthoferrites

Mechanisms of the temperature-induced spin-reorientation in rare-earth orthochromites (and orthoferrites) are examined. It is concluded that the anisotropic parts of the magnetic interactions between Cr³⁺ (or Fe³⁺) and rare-earth ions, the antisymmetric and the anisotropic-symmetric exchange interactions, are generally responsible for both the rotational and the abrupt types of the spin-reorientations. These anisotropic exchange interactions produce an effective field for the Cr³⁺ up-spins in the direction perpendicular to that of these spins and an effective field for the Cr³⁺ down-spins in the direction opposite to the above. These effective fields favor rotation of the Cr³⁺ spins, retaining their original antiferromagnetic configuration. Thus, as the temperature is lowered, this effective field increases due to the increase of the rare-earth magnetization, and when the interaction energy of the Cr³⁺ spins with these effective fields exceeds the anisotropy energy of the Cr³⁺ ion, spin-reorientation. takes place. At the beginning and ending of the spin-reorientation a second-order phase-transition occurs. The first-order nature of the abrupt spin-reorientation is stressed. Anisotropic exchange interactions between Cr³⁺ and rare-earth ions also play an important role in inducing the abrupt spin-reorientation.     

Microwave spectrum of cis-thiopropionic acid

The microwave spectrum of cis-thiopropionic acid in the ground vibrational state has been observed in the frequency range between 10 and 35 GHz. The rotational and centrifugal distortion constants, and the dipole moments have been determined. The conformation of this molecule is discussed on the basis of the observed results.     

Superconductivity and metal-insulator transition in amorphous Si1−xAux system

Electrical conductivity of metallic amorphous Si_1?xAu_x films was measured down to 10 mK. Superconducting transition was observed in a certain range of Au content. In the normal state, the temperature variation of electrical conductivity showed √T-dependence at higher temperatures and ln T-dependence at lower temperatures. This crossover is interpreted as being due to a change of sample dimensionality.