Properties of Va metal-B films prepared by r.f.-sputtering

Ta_100-x B _x alloy films were prepared by r.f.-sputtering in the chemical composition range 45 x 77. Ta_100-x B _x (45 x 58) films consist of the amorphous phase, while the TaB₂ crystal phase was observed in Ta_100-x B _x (66 x 77) films. A remarkable preferred orientation with the (001) plane of TaB₂ parallel to the film surface was observed in Ta₃₄B₆₆. The d.c. electrical conductivity of Ta_100-x B _x (45 x 77) films decreases with increasing boron content in the range 6.7 × 10³ to 1.3 × 10^3–1 cm^–1. The micro-Vickers hardness of Ta_100-x B _x (45 x 77) films was in the range 2200 to 2600 kg mm^–2.     

Role of granulosa and theca cell interactions in ovarian follicular maturation

We developed a culture system in which two types of ovarian follicular cells were allowed to attach to opposite sides of a collagen membrane. Using this in vitro cell culture system, we studied the effects of granulosa- and theca-cell interaction on the morphology, structure, and function of bovine ovarian follicular cells. In the first part of the study, we explored how the interaction between theca and granulosa cells affects the morphology and structure of the cells. This study was done using follicular cells collected from bovine ovarian follicles at the early developmental stage. Granulosa cells cultured alone were flattened, and formed a monolayer sheet. By contrast, granulosa cells cultured with theca cells were convex, and formed multilayer sheets. Theca cells cultured alone were thin, flat, and spindle-shaped. Theca cells cultured with granulosa cells were also spindle-shaped; however, they appeared convex and more densely packed when compared with theca cells cultured alone. In the second part of the study, the possible role of the cellular interaction in the control of differentiation and growth of granulosa and theca cells was investigated. When follicular cells were isolated from the early stage of follicular development, theca cells reduced progesterone and inhibin production by granulosa cells and augmented the growth of granulosa cells. When the cells were isolated from the late stage of follicular development, by contrast, theca cells augmented hormonal production by granulosa cells, and did not affect the growth of granulosa cells. The growth and androstenedione production by theca cells were increased by the presence of granulosa cells, irrespective of the origin of follicular cells. These results demonstrated that communication between two types of follicular cells results in reciprocal modulation of their morphology, structure, growth, and function. Cellular interactions seem to be one of the major factors controlling the differentiation and growth of the follicular cells during the follicular maturation process. In contrast to granulosa and theca cells cultured alone, cells in the coculture seemed to possess morphological and functional characteristics more similar to those of cells in the growing follicular wall in vivo. Thus, we speculate that the interaction between these two types of follicular cells is essential for the maintenance of original structure and function of the bovine follicular wall.     

Effects of free stream turbulence on a turbulent boundary layer on a flat plate with zero pressure gradient part IV: Calculation of the flow field

The effects of free stream turbulence on a turbulent boundary layer were calculated by using a k-ϵ two-equation model. The calculations were performed with respect to velocity profiles on a flat plate, wall shear stress, turbulence energy, integral length scales of turbulence, and decay of free stream turbulence, and the results were compared with the experimental results. The energy of the free stream turbulence and the dissipation values at the leading edge of the flat plate were used as the initial calculation conditions. These initial values of dissipation were determined from the integral length scales of the free stream turbulence at the leading edge. The calculated wall shear stress increased with the free stream turbulence and integral length scales of turbulence. The velocity profiles and turbulence energy agreed well with the experimental results, and the effects of free stream turbulence on the wall shear stress agreed fairly well with those observed in experiments. © 1997 Scripta Technica. Inc. Heat Trans Jpn Res. 25 (2): 65–75, 1996     

Polyacene capacitors

We fabricated two types of polyacene capacitor with extremely stable polyacenic semiconductor (PAS) as the positive and negative electrodes. The first one is a coin-type PAS capacitor (six different sizes), which possesses large capacity with high reliability. Its capacity is much larger than that of the conventional electric double-layer capacitor which uses activated carbon as electrode. PAS capacitor can maintain more than 70% of the initial capacity even after 100 000 cycles. Moreover, this capacitor can be charged and discharged in a few minutes as well as at low rate. The second one is a cylinder-type PAS capacitor (diameter: 18 mm, height: 65 mm) which shows high capacity of 100 F and can discharge at the extremely high rate of 80 C. The coin-type PAS capacitor is currently used for memory back-up of electrical and communication equipment, and the cylinder-type is considered to be useful as power back-up for starting drive parts of electric equipment which needs high power density.     

A study on the pristine and the doped polyacenic semiconductive materials

A new material supposed to have a mixed structure of polyacenic skeletons has been prepared from phenol-formaldehyde resin through the pyrolytic process. This material is air-stable, showing a wide variation of electrical conductivity with pyrolytic temperature. Moreover, it has been confirmed that the present material can be doped with an electron acceptor (iodine) and an electron donor (sodium) in a successful manner, giving rise to a maximum increase in the conductivity of more than seven and eleven orders of magnitude, respectively. The results of the electron probe X-ray microanalysis (EPMA) with respect to the doped samples have shown a uniform distribution of the dopants inside these materials.     

Interaction of Ag ions with a vanadium pentoxide hydrate—Formation of silver vanadate at low temperature

Reactions between V₂O₅·nH₂O sol and Ag⁺ solution were investigated and new conventional reaction processes to produce silver vanadate bronzes were found. Reactions were surveyed as a function of the concentration ratios of Ag and V, and the reaction regions were divided into 4 parts dependent upon the reaction products. System 1: ion-exchanged sediment to produce -Ag_0.35V₂O₅; System 2: needle-like -AgVO₃ and hydrate to produce Ag_{2 – x}V₄O₁₁ upon heating; System 3: new fine needle-like particle and small proportions of various dendrite crystallites; System 4: hydrate to produce -AgVO₃ upon heating. The new needle-like particle of system 3 was analyzed by use of electron diffraction and XRD and found to be monoclinic, a = 32.96 Å, b = 2.60 Å, c = 3.62 Å, and = 91.88°. The material is named -AgVO_3· -Ag_0.35V₂O₅ and Ag_{2 – x}V₄O₁₁ were reversibly crystallized after melt. -AgVO₃ was crystallized when the melt was cooled slowly, while -AgVO₃ was crystallized when quenched rapidly.     

Structural analysis of polyacenic semiconductor (PAS) materials with Xenon NMR measurements

Structural analysis of the polyacenic semiconductor (PAS) material prepared by the pyrolysis of phenol-formaldehyde resin at relatively low temperature (680 °C) has been performed by applying ¹²⁹Xe nuclear magnetic resonance (NMR) measurements. One can obtain information on the microporous structure of the PAS material through adsorption of Xe atoms, since a ¹²⁹Xe nucleus is a very sensitive probe of its microscopic environment. All the introduced Xe atoms were adsorbed on the internal surface of the pure PAS sample, which indicated remarkably large surface area of the PAS material. The average pore size of the pure PAS sample has been determined to be 7.7 ± 1.6 Å from the pressure dependence of the Xe NMR chemical shift. In connection with the application of the PAS material to the electrode of the Li rechargeable battery, changes in the Xe NMR spectrum brought about by extrinsic additives such as binder, electrolyte solvent, and the doped Li have been investigated. In particular, it has been found that the Li-doping entirely prevents Xe atoms from entering into the micropores of the PAS material, probably due to adsorption of the solvent molecules on the internal surface of the micropores.     

Extraction,selection and ranking of Field Association (FA) Terms from domain-specific corpora for building a comprehensive FA terms dictionary

Field Association (FA) Terms—words or phrases that serve to identify document fields are effective in document classification, similar file retrieval and passage retrieval. But the problem lies in the lack of an effective method to extract and select relevant FA Terms to build a comprehensive dictionary of FA Terms. This paper presents a new method to extract, select and rank FA Terms from domain-specific corpora using part-of-speech (POS) pattern rules, corpora comparison and modified tf-idf weighting. Experimental evaluation on 21 fields using 306 MB of domain-specific corpora obtained from English Wikipedia dumps selected up to 2,517 FA Terms (single and compound) per field at precision and recall of 74–97 and 65–98. This is better than the traditional methods. The FA Terms dictionary constructed using this method achieved an average accuracy of 97.6% in identifying the fields of 10,077 test documents collected from Wikipedia, Reuters RCV1 corpus and 20 Newsgroup data set.     

Effect of some amino acids on the rectal irritation caused by sodium caprate in conscious rats

The effects of some amino acids such as L-glutamine (Gln), L-arginine (Arg) and L-methionine (Met) on rectal irritation caused by sodium caprate were studied in rats. Rectal irritation was assessed by the balloon method in fasting conscious rats. This method is based on measuring rectal contractions due to possible irritation caused by the presence of drugs and/or adjuvants in the rectum. Strong contractions were observed after rectal administration of an aqueous solution of 100 mM sodium caprate. However, the presence of Gln, Arg or Met (100 mM) in sodium caprate (100 mM) solution resulted in a significant decrease in the intensity of the rectal contraction caused by sodium caprate. The rectal absorption-promoting effect of sodium caprate on 6-carboxyfluorescein (6-CF) was examined following administration with amino acids in rats. The absorption of 6-CF was not influenced by the concurrent administration of amino acids. In addition, the rectal tissue interaction of sodium caprate, with or without Gln, was examined. The concentration of sodium caprate in rectal tissue was reduced by the presence of Gln.