Interfacial tension of demixed polymer solutions over a wide range of reduced temperature

Interfacial tensions were measured for solutions of polystyrene-methylcyclohexane, polystyrene-heptamethylnonane and poly(dimethyl siloxane)-phenylethyl ether to investigate the behaviour of the interfacial tension from the critical point to a region far away from it. In the polystyrene-heptamethylnonane system, measurements were performed until the concentration of the polymer rich phase became about 70～80%. The molecular weight dependence of the interfacial tension was stronger away from the critical temperature than near to it. Data for polystyrene solutions with different solvents were connected by a scaling law. Recent scaling theories were compared with the results for poly(dimethyl siloxane) solution.     

Qualitative analysis of fluorescent whitening agents in river water

The analytical method of fluorescent whitening agents (FWAs) in river waters was examined. Two types of FWAs were identified qualitatively in river waters with the aid of the extraction method developed in the present work and thin layer chromatography.     

Reliability of high radiance InGaAsP/InP LED́s operating in the 1.2-1.3 µm wavelength

The reliability of high radiance InGaAsP/InP DH LED's operating in the1.2-1.3 mum wavelength and the defect structures observed in this quaternary alloy have been presented. Threading dislocations and misfit dislocations do not act as strong nonradiative recombination centers, in contrast with the case in GaAs or GaAlAs optical devices. Dark-spot defects (DSD's) were sometimes generated in the emitting area during aging at elevated temperatures. These defects were analyzed microscopically using a transmission electron microscope and were identified as precipitates. To investigate the homogeneous degradation, accelerated aging at the ambient temperatures of 20, 60, 120, 170, 200, and 230°C has been carried out for over 15 000 h at the current density of 8 kA/cm²using LED's without dark structures. The degradation rates were statistically calculated by assuming the normal distribution. The mean values of degradation rates and the values of standard deviation were determined at the temperatures above 170°C. The activation energy of homogeneous degradation was determined to be 1.0 eV and the extrapolated half-life in excess of 10⁹h was estimated at the ambient temperature of 60°C.     

Electric Field Effect on the Magnetic Properties of III–V Ferromagnetic Semiconductor (In,Mn)As and ((Al),Ga,Mn)As

We have investigated the magnetotransport properties of field-effect transistors (FET) having a III–V ferromagnetic semiconductor channel layer. One can control not only the ferromagnetic transition temperature T _C but also the magnetization and the coercive force of (In,Mn)As channel layers isothermally and reversibly by gate electric fields. A small change of the magnetization upon application of gate electric fields is also observed in FETs with a (Ga,Mn)As channel. Results on a (Al,Ga,Mn)As channel FET are also presented.     

Uncertainty Analysis of Evaporation Rate in Magnetic Suspension Balance/Diffusion-Tube Humidity Generator

An analysis method for the uncertainty of a small evaporation rate in a magnetic suspension balance/diffusion-tube humidity generator has been developed. Using experimentally obtained data, the uncertainty is evaluated as a function of measurement time. It is found that the observed standard deviation of the evaporation rate in a region of short measurement time (short term) is inversely proportional to the measurement time, and that in a region of long measurement time (long term) the standard deviation does not vary markedly with increasing measurement time. The behavior of the observed standard deviation in the short term is attributable mainly to the uncertainty of the balance reading, and that in the long term to the variability of room temperature. The results of the investigation show that the use of only least-squares analysis leads to underestimation of the uncertainty.     

Internal Flow of Acoustically Levitated Droplet

Under the microgravity environment, products of new and high quality materials solidified into homogeneous crystal by under cooling solidification have been the subject of much interest. Manufacture of material under the microgravity environment can be performed more static than that under the normal gravity. Handling technology of molten metal is important for such processes to hold in the limit space. However, when a large levitated droplet exists in the limit space, internal flow can be appeared remarkably. Elucidation of the effect of the internal flow of the levitated droplet is required in order to establish the containerless processing for new material under the microgravity environment. In current research, the internal flow of a levitated droplet was investigated by Zhao et al. (J Acoust Soc Am 106:589–595, 1999a and 106:3289–3295, 1999b) and Trinh et al. (Phys Fluids 12(2):249–251, 2000). These studies were analyzed numerically and theoretically. However, experimental study about the internal flow of the levitated droplet is not enough. According to our study Abe et al. (Microgravity Sci Technol 19(3–4):33–34, 2007), the authors observed internal flow of the water and glycerol droplet in normal gravity environment. In the water droplet, which is a low viscosity fluid, internal flow of both left and right hand rotation was observed. On the other hand, in the glycerol droplet, which is a high viscosity fluid, only rigid body rotation was observed. This research measured only two dimensional flows. It is thought that internal flow in the water is not two-dimensional but three-dimensional flow. Then, in order to investigate a three-dimensional flow structure in levitated water droplet in detail, we try to measure the three-dimensional flow in the levitated droplet. In the present study, test fluid with different viscosity is levitated. And, multidimensional PIV measurement is conducted to investigate the internal flow structure in a levitated droplet. Stereo images at equatorial plane of a levitated droplet are observed for measuring the three-dimensional component of velocity in the levitated droplet. As a result, the velocity of z direction is observed in the water droplet. On the other hand, the v _z is hardly observed in the glycerol droplet. The three dimensional structures of water and glycerol are differed. The difference of such flow structure is supposed to be due to the influence of the viscosity.     

N-terminal specific fluorescence labeling of proteins through incorporation of fluorescent hydroxy acid and subsequent ester cleavage

We have developed a novel method to attach a fluorescent label at the N terminus of proteins through a four-base codon-mediated incorporation of a fluorescent hydroxy acid and subsequent cleavage of the ester bond in a cell-free translation system. We found that a fluorescent-labeled p-amino-L-phenyllactic acid was successfully incorporated downstream of N-terminal tag peptides in response to a CGGG codon, and the tag peptides could be removed through ester cleavage to leave the fluorescent hydroxy acid at the N terminus of the proteins. Immunoprecipitation analysis revealed that ester cleavage occurred spontaneously during the translation reaction. The efficiency of the ester cleavage and the yield of the labeled proteins were dependent on the peptide tag sequence. We demonstrate that the insertion of an asparagine residue between the N-terminal T7 tag and the fluorescent hydroxy acid achieved both quantitative ester cleavage and efficient expression of the labeled proteins. The present method is a potential tool for N-terminal specific labeling of proteins with various compounds.