IR Practical Extinction Coefficients of Water in Alkali Lime Silicate Glasses Determined by Nuclear Reaction Analysis

Infrared spectroscopy (IR) is widely used to determine the water concentration in glasses, whereas determination of the IR practical extinction coefficient is necessary to deduce the absolute water concentration of glasses on the basis of Beer–Lambert law. From the nuclear reaction analysis data, the IR practical extinction coefficients of water were successfully determined for the alkali lime silicate glasses with different levels of sodium/potassium cation (Na/K) ratio. The two‐band method is well‐known to be useful for the determination of the water concentration in some alkali lime silicate glasses. It is proved here that the two‐band method is not applicable to the variety of composition for alkali lime silicate and soda lime aluminosilicate glasses, whereas it is valid for the similar composition of soda lime silicate glasses [SLS: Composition (in mol%) 16Na₂O·10CaO·74SiO₂]. The single‐band procedure with the IR practical extinction coefficient is crucial for the determination of the precise water concentration in the wide variety of glass composition although the determination of the IR practical extinction coefficient is troublesome. It also appears that the ion radius of alkali affects the IR practical extinction coefficient and the chemical state of OH group in glasses.     

Diameter-controlled and nitrogen-doped vertically aligned single-walled carbon nanotubes

Diameter controlled and vertically aligned single-walled carbon nanotubes were synthesized from pure and mixed ethanol/acetonitrile feedstock. With increasing acetonitrile concentration in the feedstock, nitrogen incorporation into the sp² carbon network increased until saturating at approximately one atomic percent. The incorporation of nitrogen correlates with a significant diameter reduction from a mean diameter of 2.1 nm down to 0.7 nm. Heteroatom-mediated diameter control is independent of catalyst preparation and represents a versatile tool for the direct synthesis of tailored single-walled carbon nanotubes.     

Morphometric study of myelinated fibers in human cervical spinal cord white matter

STUDY DESIGN: Using human autopsy spinal cord specimens, morphologic measurements of myelinated nerve fibers were performed, focusing on the regions that include the main white matter conduction paths. The hemilateral spinal cord morphology was also measured, and its relation with the component myelinated nerve fibers determined. OBJECTIVES: To determine the relation between spinal cord transverse area in the normal lower cervical spine, the site most vulnerable to chronic compressive myelopathy, and myelinated nerve fibers. SUMMARY OF BACKGROUND DATA: Considerable interindividual variation normally is observed in the morphology of the spinal cord transverse area. The influence of this variation on the composition of the white matter myelinated nerve fibers is obscure. METHODS: The C7 segments from seven cadavers were resected, and from magnified photographs of paraffin-embedded specimens, the hemilateral spinal cord area and funicular area were measured. Nerve fiber morphology was measured using Epon-embedded specimens. Three regions that included the main conduction paths were sampled, and magnified photographs obtained. The nerve fiber transverse morphology was measured using the ellipse conversion method, and the myelinated nerve density and fiber area were determined. RESULTS: Marked interindividual variations were found in both the hemilateral spinal cord transverse area and funicular area. A positive correlation was noted between the two, with the spinal cord transverse area large in the cases with a large funicular area. For fiber density and area, histograms were constructed that showed characteristic distribution patterns in each region. By dividing each region into two components (i.e., small- and large-diameter fibers), it was found that the interindividual variation in large-diameter fiber density was small, clarifying that the absolute number of large-diameter fibers compared to fiber density is more strongly dependent on the funicular area. CONCLUSIONS: The absolute number of large-diameter myelinated fibers is smaller in cross-sections of thin as compared to those of thick spinal cord. When elucidating the pathophysiology of compressive myelopathy, it is necessary to study not only the circumstances surrounding the spinal cord, but this kind of factor intrinsic to the spinal cord itself.     

Diameter controlled chemical vapor deposition synthesis of single-walled carbon nanotubes

In this study, we systematically investigated the influence of catalyst preparation procedures on the mean diameter of single-walled carbon nanotubes (SWNTs) synthesized by the alcohol catalytic chemical vapor deposition (ACCVD) process. It was found that the SWNT diameter is dependent upon both reduction temperature and time, with lower reduction temperature and/or shorter reduction time resulting in smaller diameter SWNTs. The morphology of the SWNTs also changed from vertically aligned to randomly oriented when the reduction temperature was below 500 degrees C. We also found that introducing a small amount of water during the catalyst reduction stage significantly decreased the mean diameter of the SWNTs. Lastly, we report on the use of a new binary catalyst system in which rhodium was combined with cobalt. This new Co/Rh combination produced SWNTs of smaller diameter than the conventional Co/Mo catalyst.     

Polycrystalline silicon films with nanometer-sized dense fine grains formed by flash-lamp-induced crystallization

Flash lamp annealing (FLA) with millisecond-order pulse duration can crystallize microm-order-thick a-Si films on glass substrates through explosive crystallization (EC), and flash-lamp-crystallized (FLC) poly-Si films consist of densely-packed nanometer-sized fine grains. We investigate the impact of the hydrogen concentration and the defect density of precursor a-Si films on crystallization mechanism and the microstructures of FLC poly-Si films, by comparing chemical-vapor-deposited (CVD) and sputtered precursor a-Si films. Transmission electron microscopy (TEM) observation reveals that FLC poly-Si films with similar periodic microstructures are formed by the FLA of the two kinds of precursor films, meaning no significant influence of hydrogen atoms and defect density on crystallization mechanism. This high flexibility of the properties of precursor a-Si films would contribute to a wide process window to reproducibly form FLC poly-Si films with the particular periodic microstructures.     

Inferring Minimal Functional Dependencies in Horn and q-Horn Theories

In this paper, we study various problems related to the inference of minimal functional dependencies in Horn and q-Horn theories. We show that if a Horn theory is represented by a Horn CNF, then there exists an incrementally polynomial algorithm for inferring all minimal functional dependencies. On the other hand, if a Horn theory is represented as the Horn envelope of a given set of models, then there exists a polynomial total time algorithm for this inference problem if and only if there exists such an algorithm for dualizing a positive CNF. Finally, we generalize our results to the case of q-Horn theories, and show that all the considered problems can be reduced in polynomial time to the corresponding problems for Horn theories.     

Characteristics of Strength for Hydraulic Fracturing of Buffer Material

The fundamental characteristics of strength for the hydraulic fracturing of highly compacted bentonite were studied. Firstly, the constant pressurize rate tests were carried out for the material having various specifications. Secondly, the cyclic pressurize test was carried out to examine the self-sealing function as a buffer material. Thirdly, the constant pressure test was carried out to observe the change in strength during seepage. The observed phenomena were analytically examined. As a result, it was found that the strength for hydraulic fracturing of the buffer material increased with the increase of initial dry density, decrease of sand-mixture ratio and decrease of water content. The swelling pressure of the buffer material worked as a constraint stress for the strength for hydraulic fracturing. The fracture made by hydraulic fracturing was fixed through the supply of water. However a long period of low-pressure supply was needed to recover the strength at the failed parts. While the tensile failure was dominant, the specimen having a low dry density might be failed initially by the shear failure. When the water content became large during seepage, the strength for hydraulic fracturing reduced.