Electrical conductivity measurement and thermogravimetric study of pure and niobium-doped uranium dioxide

The electrical conductivity and nonstoichiometric composition of UO_2+x and (U_1?yNb_y)O_2+x (y = 0.01, 0.05 and 0.10) were measured in the range $\text{1282 ≦ T ≦ 1373}$ K and Pa by tie four inserted wires method and thermogravimetry, respectively. The electrical conductivity of (U_1?yNb_y)O_2+x plotted against the oxygen partial pressure indicated a minimum corresponding to the transition between $\text{n}$- and $\text{p-}\text{type}$ cone uction. The band-gap energy of (U_1?yNb_y)O_2+x was calculated to be $\text{(248 ± 12)}$ kJmol.^?1, independent of niobium content, which is nearly the same as that of UO_2+x. From the oxygen partial pressure dependences of both the electrical conductivity and the deviation $\text{x}$ of UO_2+x and (U_1?yNb_y)O_2+x, the defect structures in these oxides were discussed with the complex defect model consisting of oxygen vacancies and two kinds of interstitial oxygens.     

Variations in anatomy and ultraviolet microspectrometry between normal and brown midrib mutant maizes possessing different rumen degradabilities

Normal and brown midrib mutant (bmr) maize (Zea mays L) were examined for variations in their morphological composition. The degradability of the leaf blade, leaf sheath and stem, proportional area of specific tissues in leaf blade, and the ultraviolet (UV) absorption spectra of cell walls were measured and related to variations in cell wall degradability by rumen microorganisms. The UV and infrared (IR) absorption spectra of the lignins isolated from leaf blades of both types, before and after reduction with sodium borohydride, were recorded. The bmr3 maize had higher dry matter (DM) and neutral detergent fibre (NDF) degradabilities for leaf blade, leaf sheath, and stem than the normal counterpart. Approximately 35% and 26% of the observed difference in DM degradability was attributed to the difference in DM degradability of stem and leaf blade, respectively, and 39% to the difference in DM composition of stem. Distinct differences in tissue degradation of the leaf blades were observed for mesophyll cell walls in the midrib portion, which were thinner and of greater number in the bmr3 maize. Sclerenchyma cells were present only in the vascular bundles in the bmr3 leaf blade, while in the normal type those cells were underneath the epidermis tissue. The bmr3 plant also had large epidermal cells. UV microspectrometry of mesophyll cell walls of the bmr3 maize showed their lower UV absorbance around 320 nm compared to that of the normal, but not at 280 nm. Considerable increase in the UV absorbance at 280 nm was observed for the isolated lignins after reduction, suggesting a lesser degree of lignification in the bmr3 maize tissues. Lowered UV absorbance of the isolated lignin around 320 nm after reduction was associated with the removal of the IR bands at 1730, 1660, 1600, and 1250 cm^?1.     

Effect of crystalline properties on coercive force in iron acicular fine particles

Crystallographic properties and their size dependence in acicular fine particles of iron prepared by reduction from-FeOOH were investigated by transmission electron microscopy and compared with magnetic properties. Although both larger particles with an average needle length of 0.5m and smaller ones of 0.2m length have single domain configuration, the former are crystal lographicaIly polycrystalline while the latter are single crystal with a [100] axial orientation, an easy magnetization direction of iron. The coercive force, principally yielded by external shape anisotropy, is higher in smaller particles in spite of their inferior axial ratio. The intrinsic magnetocrystalline anisotropy is inferred to be the most responsible to give rise to this further increase of coercive force. The experimentally obtained values of magnetic properties are also compared with the theoretical estimation, which results semi-quantitatively in good accordance.     

Temperature-Responsive Chromatography Using Poly(N-isopropylacrylamide)-Modified Silica

A new concept in chromatography is proposed that utilizes a temperature-responsive surface with a constant aqueous mobile phase. The surface of the silica stationary phase in high-performance liquid chromatography (HPLC) has been modified with temperature-responsive polymers to exhibit temperature-controlled hydrophilic/hydrophobic changes. Poly(N-isopropylacrylamide) (PIPAAm) was grafted onto (aminopropyl)silica using an activated ester-amine coupling method. These grafted silica surfaces show hydrophilic properties at lower temperatures which, as temperature increases, transform to hydrophobic surface properties. The elution profile of five mixed steroids on an HPLC column packed with this material depends largely on the temperature of the aqueous mobile phase. Retention times increase with increasing temperature without any change in the eluent. Changes in the retention times of hydrophobic steroids were larger than those for hydrophilic steroids. The temperature-responsive interaction between PIPAAm-modified silica and these steroids is proposed to result from changes in the surface properties of the HPLC stationary phase by the transition of hydrophilic/hydrophobic surface-grafted IPAAm polymers. We demonstrate a novel and useful new chromatography system in which surface properties and the resulting function of the HPLC stationary phase are controlled by external temperature changes. This method should be effective in biological and biomedical separations of peptides and proteins using only aqueous mobile phases.     

Chronic levodopa therapy enhances dopa absorption: contribution to wearing-off

Effects of the chronic administration of levodopa on its peripheral pharmacokinetics and the contribution of the pharmacokinetics to the pathogenesis of the wearing-off phenomenon are re-evaluated. The concentration of plasma levodopa and clinical symptoms were determined 4 hours after oral levodopa (levodopa 100 mg + benserazide 25 mg) administration on 55 parkinsonian patients. Long-term levodopa therapy markedly increased the peak levodopa concentration (Cmax) and the area under the time-concentration curve (AUC); whereas, it decreased time to the peak concentration (Tmax) and the elimination half-life (T1/2). These results suggest that long-term levodopa therapy accelerates the absorption of levodopa. The wearing-off group (n = 23), however, had a markedly higher Cmax and AUC, and a shorter Tmax and T1/2 than the stable group (n = 32). We speculate that the clinical expression of "stable" or "wearing-off" depends on the absorption of levodopa as well as the presynaptic terminal and post synaptic receptors.     

An approach to establishing a method for calculating inventory

In periodic review inventory systems, inventory is classified into cycle stock and safety stock. Cycle stock is defined as inventory that absorbs differences between supply and demand frequencies. It can be calculated without deficiency or excess because a method has been established for ensuring that the minimum on-hand inventory during a periodic review is zero. Safety stock is defined as inventory that absorbs various differences between supply and demand. Unlike for cycle stock, a method for calculating safety stock without deficiency or excess remains to be established. An approach is proposed to establishing a method for calculating inventory in which inventory is classified on the basis of the holding purpose and the calculation factors indicate solutions. This approach was applied to inventory held to absorb, on the basis of fluctuations in demand, the difference in terms of time and quantity between supply and demand. Stock held for this purpose is referred to as ‘fluctuation stock’. The objective is to establish a method for calculating fluctuation stock so that the minimum on-hand inventory during a periodic review is zero and to clarify the relationship between fluctuation stock and safety stock.     

Kinetics of solid state polymerization of poly(sulphur nitride)

Kinetics of the solid state polymerization of disulphur dinitride into poly(sulphur nitride) was investigated using Fourier transform infrared spectroscopy in the temperature range 22 to 40 ° C. It was found that the polymerization is autocatalytic. The polymerization rate is strongly dependent on temperature and the overall activation energy of the polymerization in this temperature range was found to be 41 kcal mol^–1. The polymerization is also strongly dependent on the crystal size, at 23 ° C the polymerization of needle-like crystals of about 5m in width was complete in about 6 h but crystals of several millimetres in size reached conversion of only 40% in 6 days. It is concluded that the polymerization is much faster at the crystal surface than in its interior. Hence, it is suggested that the polymerization begins at the crystal surface and progresses towards the interior of the monomer crystal. The polymerization mechanism is discussed in terms of Baughman's theory of single-phase solid state polymerization; it is suggested that the autocatalytic character of S₂N₂ polymerization is better described by the effect of the nearest neighbour interactions than by the effect of long range lattice strain.     

(Z,Z)-5,27-Tritriacontadiene: Major sex pheromone ofDrosophila pallidosa (Diptera; Drosophilidae)

A crude cuticular extract from both sexes of 3660 fruit flies (Drosophila pallidosa) was subjected to SiO₂ and AgNO₃/SiO₂ column chromatography, accompanied by bioassay for the sex pheromone activity. After three chromatographic steps, the active fraction was obtained. The main component of the active fraction was determined to be (Z,Z)-5,27-tritriacontadiene [(Z,Z)-5,27-C_33:2, on the basis of gas-liquid chromatographic analysis, chemical derivatization and gas chromatography-mass spectrometry. Synthetic (Z,Z)-5,27-C_33:2 at 5 female equivalents (FE) elicited a clear courtship response with a high courtship index amongD. pallidosa males. Therefore it was concluded that (Z,Z)-5,27-C_33:2 was a major sex pheromone component in this species.     

A Note on Intensionalization

Building on Ben-Avi and Winter’s (2007) work, this paper provides a general “intensionalization” procedure that turns an extensional semantics for a language into an intensionalized one that is capable of accommodating “truly intensional” lexical items without changing the compositional semantic rules. We prove some formal properties of this procedure and clarify its relation to the procedure implicit in Montague’s (1973) PTQ.     

Enhancement of ionic conduction in CaF2 and BaF2 by dispersion of Al2O3

Ionic conductivity measurements were performed on polycrystalline CaF₂, BaF₂ and those dispersed with Al₂O₃ particles. The ionic conductivity of both CaF₂ and BaF₂ increased by about 1 to 2 orders of magnitude by dispersion of Al₂O₃ particles, while X-ray diffraction measurements showed there were no other phases present other than fluoride and Al₂O₃. The conductivity of the dispersed system strongly depended on the particle size and the concentration of Al₂O₃, which suggested the high ionic-conductivity layers were formed at the interface between the ionic conductor matrix and the Al₂O₃ particles. The effective thickness and electrical conductivity of the interface layer at 500° C were calculated, using a simple mixing model, to be 0.3 to ~ 0.6m and ~ 10^–3 S cm^–1, respectively.