Mass spectrometric studies of alkyl-, phenyl- and chloropyrimidines

The mass spectra of alkyl- and chloropyrimidines are recorded. A generalised fragmentation mechanism for the derivatives of pyrimidine is proposed. The principle of α-cleavage for heterocyclic compounds as proposed in the previous paper is shown to be valid for pyrimidine derivatives. Electronic structures of some molecular and intermediate ions are calculated by the openshell CNDO/2 and INDO methods.     

Exact ground-state correlation functions of one-dimensional strongly correlated electron models with resonating-valence-bond ground state

We investigate one-dimensional strongly correlated electron models which have the resonating-valence-bond state as the exact ground state. The correlation functions are evaluated exactly using the transfer matrix method for the geometric representations of the valence-bond states. In this method, we only treat matrices with small dimensions. This enables us to give analytical results. It is shown that the correlation functions decay exponentially with distance. The result suggests that there is a finite excitation gap, and that the ground state is insulating. Since the corresponding noninteracting systems may be insulating or metallic, we can say that the gap originates from strong correlation. The persistent currents of the present models are also investigated and found to be exactly vanishing.     

Elastic properties and structure of alkaline-earth silicate glasses

The densities and elastic properties of RO · SiO₂ and RO · 2 SiO₂ glasses (R = Mg, Ca, Sr, Ba or their mixtures) have been determined to obtain the compositional dependences of volume and bulk modulus of alkaline-earth silicate glasses. The mean atomic volume was found to vary almost linearly with glass composition for a series of RO · SiO₂ or RO · 2SiO₂ glasses, although there exists a slight negative deviation from the linearity for RO · 2SiO₂ glasses when two kinds of alkaline-earth oxides were mixed. The change in glass volume agreed fairly well with the value calculated on the basis of the difference in ionic size of alkali-earth ions being subtituted each other. The bulk moduli of RO · SiO₂ and RO · 2Si_O2 glasses were found to vary in reciprocal proportion to the four-thirds power of the volume when R was changed from one kind to another, indicating that the difference in internal energy of glass arises mainly from the change in Coulombic attraction due to their size difference. These results seemed to show that the glass structure of a series of RO · 2SiO₂ or RO · 2SiO₂ glasses remains almost unchanged except the local a change around R ions when R is subtituted from one kind to another.     

Estimation of energy dissipated during superconducting wire motion in a magnetic field

An experiment was carried out to study the motion of superconducting wire under the influence of electromagnetic force. Experiments were conducted at 4.2 K by varying the experimental conditions such as tension to the superconducting wire, current ramp rate, and the use of different insulating materials at the interface of the superconducting wire. We were able to examine in detail the structure of the voltage spikes caused by sudden wire motion. The velocity of the wire motion, distance moved by the wire, and energy dissipated during wire motion are estimated.     

Synthesis of novel fluorescently labeled water-soluble fullerenes and their application to its cellar uptake and distribution properties

Fullerene is a well-known carbon nanomaterial, which can be potentially used for drug manufacture or delivery. Despite several successful examples of utilizing fullerene derivatives as drug candidate materials, their low water solubility under physiological conditions negatively affects the cell penetration efficiency after treatment. In this work, we successfully synthesized two fullerene derivatives with covalently attached fluorescein and boron dipyrromethene (BODIPY) fluorophore moieties, which exhibited cellular uptake and intracellular localization. While both fluorophores decreased their fluorescence intensity in the vicinity of fullerene, the cellar uptake of the fluorescein-modified fullerene was detected via fluorescence microscopy observations. Moreover, decreases in the fluorescence intensities of the intact fluorescein and BODIPY species were observed when both fluorophores and fullerene coexisted in aqueous media.     

Disk-type Nd/Cr:YAG ceramic lasers pumped by arc-metal-halide-lamp

We observed the lasing of highly sensitized Nd/Cr:YAG ceramic disks that use artificial solar radiation pumping. The disk material can be used for high power multi-stage amplifiers pumped by lamplight or sunlight because of its scalability and ability to handle high power densities. A maximum output power of 86 mW was experimentally obtained, and this value correlated well with the calculated results. A small signal gain of 1.9 was obtained, and the estimated stored energy was 0.6 J/cm³, which is three or four times higher than that from a Nd:YAG medium.     

Effect of measurement volume size on turbulent flow measurement using ultrasonic Doppler method

This paper presents the results of an investigation on the effects of measurement volume size on the mean velocity profile and the Reynolds stress for fully developed turbulent pipe flows. The study employs the ultrasonic velocity profile method, which is based on the ultrasonic Doppler method. The ultrasonic Doppler method offers many advantages over conventional methods for flow rate measurement in the nuclear power plant piping system. This method is capable of measuring the instantaneous velocity profile along the measuring line and is applicable for opaque liquids and opaque pipe wall materials. Furthermore, the method has the characteristic of being non-intrusive. Although it is applicable to various flow conditions, it requires a relatively large measurement volume. The measurement volume of the present method has a disk-shape determined by the effective diameter of the piezoelectric element and the number of the wave cycles of the ultrasonic pulse. Considering this disk-shaped measurement volume and expressing the time-averaged velocity in a truncated Taylor series expansion around the value at the center of the measuring control volume, the value of the velocity can be obtained. The results are then compared with the data obtained from DNS and LDA measurements. The result shows that the effect of the measurement volume size appears in the buffer region and viscous sublayer.