Terahertz Time-Domain Spectroscopy of Solids: A Review

Recent development of the terahertz time domain spectroscopy (THz-TDS) and its application to solids have been reviewed. This spectroscopy is unique in that the time-domain wave forms are measured at first and the complex optical constants are deduced directly by the Fourier transformation of them without resort to the Kramers-Kronig analysis. Various types of the THz-TDS systems are briefly described. Applications of the THz-TDS to various solids, i.e., semiconductors, superconductors, polymers, photonic crystals, and so on are also presented to demonstrate how widely this spectroscopy is applicable to characterization of solids.     

Increase of coercive force in sputtered hard disk

A study was made on increasing the coercive force in CoNiCr/Cr sputtered hard-disk media. A higher coercive force could be obtained when the substrate temperature was higher than 150°C and a negative bias voltage was applied to the substrate during sputtering. With optimized conditions, a coercive force of more than 2300 Oe was obtained. The increase in the coercive force is thought to be due to the enhancement of isolation between magnetic particles by developing the segregation of Cr in the CoNiCr film     

Development of solar total energy system in Japan

To clarify the feasibility of introducing solar total energy system into various factories, an experimental facility was constructed at Tsukuba Second Research Center on March 1982. Long-term experimental studies are presently being continued to determine the operating characteristic of the facility. This facility is constructed to improve the system availability and to collect effectively solar energy under fairly bad weather conditions as experienced in Japan. To accomplish this purpose, it is operated by selecting one of three operating modes according to the intensity of insolation and the thermal condition of the heat storage unit. In this paper, the outline of the facility is described. Experimental results show that in this facility the operating rate increases and useful energy, such as electricity, can be obtained from solar energy if the operating mode is selected according to the weather condition at 8:00 a.m.     

Investigation of nitrate salts for solar latent heat storage

Solar thermal applications require some means of thermal energy storage. Amongst several storage concepts, latent heat storage is quite suitable because of its high storage density and almost constant temperature during charging and discharging. The temperature range between 200 and 300°C is considered to be important for solar total energy systems. In this temperature range, sodium nitrate and its mixed salts with other nitrates including eutectic and off-eutectic salts are candidates.

The present paper deals with heat transfer in a latent heat storage unit utilizing these salts. A method of rough estimation of the thermal conductivity of the storage materials is described, and the temperature history of the storage material experimentally obtained is compared with numerical solutions and found to be in reasonably good agreement.

It is seen that the temperature of the heat transfer surface quickly drops soon after the appearance of a solid phase due to low thermal conductivity of these salts. Ways to avoid this temperature drop are discussed.     

Changes in textural properties of Japanese tenobe somen noodles during storage

Tenobe somen (TS) noodles are traditional Japanese wheat-based noodles that are produced manually using a sophisticated method called tenobe (literally, "hand stretched"). In the tension test, both the tensile strength and extensibility of TS noodles were greater than those of machine-made (MS) noodles. In the biting test, the chewy texture of TS noodles was realized in the analysis of the force-deformation curves of each type of somen noodles. The creep test indicated a clear difference between the external and internal elasticity of TS noodles. The texture of TS noodles appeared to change dramatically during storage in the rainy season. In addition, firm and chewy textures of TS noodles stored for 20 mo were observed. Similar to the results from our previous study, TS noodles exhibited significantly higher dityrosine content than the flour used for their manufacture. However, the increase in the dityrosine content during the manufacturing process was not observed in the case of MS noodles. Although clear textural differences were observed between TS noodles stored for 0 and 20 mo, the dityrosine contents of TS noodles at each stage were not largely different.     

Identification of three isoforms for the Na+-dependent phosphate cotransporter (NaPi-2) in rat kidney

We have isolated three unique NaPi-2-related protein cDNAs (NaPi-2alpha, NaPi-2beta, and NaPi-2gamma) from a rat kidney library. NaPi-2alpha cDNA encodes 337 amino acids which have high homology to the N-terminal half of NaPi-2 containing 3 transmembrane domains. NaPi-2beta encodes 327 amino acids which are identical to the N-terminal region of NaPi-2 containing 4 transmembrane domains, whereas the 146 amino acids in the C-terminal region are completely different. In contrast, NaPi-2gamma encodes 268 amino acids which are identical to the C-terminal half of NaPi-2. An analysis of phage and cosmid clones indicated that the three related proteins were produced by alternative splicing in the NaPi-2 gene. In a rabbit reticulocyte lysate system, NaPi-2 alpha, beta, and gamma were found to be 36, 36, and 29 kDa amino acid polypeptides, respectively. NaPi-2alpha and NaPi-2gamma were glycosylated and revealed to be 45- and 35-kDa proteins, respectively. In isolated brush-border membrane vesicles, an N-terminal antibody was reacted with 45- and 40-kDa, and a C-terminal antibody was reacted with 37-kDa protein. The sizes of these proteins corresponded to those in glycosylated forms. A functional analysis demonstrated that NaPi-2gamma and -2alpha markedly inhibited NaPi-2 activity in Xenopus oocytes. The results suggest that these short isoforms may function as a dominant negative inhibitor of the full-length transporter.     

Dynamics of Hollow and Solid Alumina Particle Formation in Spray Flames

Thermophoretic sampling (TS) of the aerosol was conducted to manifest the formation of hollow and solid alumina particles in spray flames. The collected particles were investigated by transmission electron microscopy. Hollow particles with a thin shell (e.g., 10 nm) were formed from the aluminum nitrate precursor emulsion at less than 4-cm flame height. Hollow particles maintained their shapes in the flame using air as dispersion/oxidant gas, whereas hollow-to-solid restructuring of the particles took place in the flame using oxygen. With oxygen, nanoparticles were formed in the gas phase from the aluminum butoxide/2-propanol precursor solution only, whereas gas-phase reaction was hindered, forming large particles from the aluminum nitrate/2-propanol precursor solution.     

DTC Drives for Wide Speed Range Applications Using a Robust Flux-Weakening Algorithm

A control scheme for robust flux-weakening operation of direct-torque-control induction motor drive is proposed. The basic idea is to adjust the flux reference on the basis of the torque error, thus determining a spontaneous flux weakening. To exploit the maximum torque capability, it is necessary to estimate the maximum torque that the induction machine is able to generate at any speed. Initially, a basic version of the algorithm, requiring a simple off-line parameter tuning, is presented. Then, the algorithm is improved and completed with the online estimation of the maximum torque, hence avoiding the initial tuning process. The main features of the proposed methods are a little dependence on machine parameters and a smooth transition into and out of the flux-weakening operation mode. Experimental tests demonstrate the effectiveness of the control schemes.     

Alpha 6 beta 4 integrin and newly deposited laminin-1 and laminin-5 form the adhesion mechanism of gastric carcinoma. Continuous expression of laminins but not that of collagen VII is preserved in invasive parts of the carcinomas: implications for acquisition of the invading phenotype

We studied the expression and distribution of different laminin chains, the alpha 6 beta 4 integrin and type VII collagen, i.e., components of the epithelial adhesion complex, in gastric carcinomas and in suggested preneoplastic stages of this malignancy. Intestinal-type gastric carcinomas showed strong reactivity for laminin alpha 1, alpha 3, beta 1, and beta 3 chains, the components of laminin-1 and -5, at the interface between malignant cells and tumor stroma. The reactivities were continuous throughout the carcinomas, even in structures invading through the smooth muscle layers of the gastric wall. The expression of different laminin chains was accompanied by strong polarized reactivity for the alpha 6 beta 4 integrin, which is a receptor for both laminin-1 and laminin-5. Collagen type VII was only occasionally present at sites showing reactivity for laminin-5 and was totally absent from the cell islands invading through the gastric wall. Intestinalized gastric epithelium showed a similar expression pattern of laminins and the alpha 6 beta 4 integrin as the gastric carcinomas. Our results suggest that gastric carcinomas use the alpha 6 beta 4 integrin and newly deposited laminin-1 and -5, accompanied by the disappearance of type VII collagen, as their mechanism of adhesion during the invasion through surrounding tissues. Unlike in previous studies, the reactivity for the laminin-5 protein was not restricted to the invading cells but surrounded the malignant glandular structures throughout the tumor. Our results also show that both intestinal-type gastric carcinoma, and intestinal metaplasia mimic the gastric surface epithelium in the expression pattern of laminins and the beta 4 integrin subunit. This supports previous studies proposing a pathogenetic sequence from intestinal metaplasia to gastric carcinoma.