Upper estimate of martingale dimension for self-similar fractals

We study upper estimates of the martingale dimension d _m of diffusion processes associated with strong local Dirichlet forms. By applying a general strategy to self-similar Dirichlet forms on self-similar fractals, we prove that d _m  = 1 for natural diffusions on post-critically finite self-similar sets and that d _m is dominated by the spectral dimension for the Brownian motion on Sierpinski carpets.     

Acquiring new use of multiplication through classroom teaching: an exploratory study

This article analyzes the process in which pupils acquire new uses of multiplication to measure area. Behaviors of five 4th-grade pupils in a series of lessons on areas were studied in depth by qualitative case-study methodology. Their use of multiplication changed as the lesson evolved, characterized conceptually as “using multiplication as a label,” “using it positively to approach problems which have not been solved before,” and “using it effectively to achieve the goal of measuring areas.” These three phases show the pupils’ understanding of multiplication in the context of measuring areas from a secondary accompaniment to a powerful tool of thinking. The phases observed and the students’ progress between the phases differs noticeably among the pupils. Factors that foster learners’ progress are investigated by comparing their behaviors.     

Matrix embedded cobalt-carbon nano-cluster magnets: behavior as room temperature single domain magnets

A new type of Co-C nanoparticles is synthesized from CH₂Cl₂ solution of Co₄(CO)_{1 2} by heating up to 210 ^°C in a closed vessel. Transmission electron microscope (TEM) and electron energy loss spectroscopy (EELS) observation show that the particles are embedded in amorphous carbon and their average size is 12 nm. The radial structure function obtained from the extended X-ray absorption fine structure (EXAFS) of the Co K-edge absorption of the Co-C nanoparticles provides a Co-C average distance of 2.08 Å and the Co-Co distances of 3.18 Å and 3.9 (±0.2) Å. The particles exhibit the magnetic hysteresis curve with a coercive force of 200 Oe at 20 K and 260 Oe at 300 K. The temperature dependence of the magnetic susceptibility measured under zero-field cooling and 10 Oe field cooling conditions exhibits the behavior characteristic of a set of single magnetic domain nanomagnets in an amorphous carbon matrix.     

Effects of Thermal Treatments on Helium Retention and Thermal Desorption Behaviors in a V-4Ti Aalloy

Vanadium alloys are considered as the promising first wall and structure materials of the future fusion reactors owing to their perfect low neutron-induced radioactivity and good high temperature performance. Helium retention and thermal desorption behaviors are key issues for the applications of vanadium alloys in fusion reactors since helium can be produced by helium discharge cleaning and neutron transmutation. A. van Veen groupt investigated helium trapping and thermal desorption mechanisms in vanadium alloys by using 1 keV helium ion irradiation to the fluence of 10^13～10^14He/cm^2, and the influenee of pre-annealing treatments on helium trapping. Two group of peaks were found at the thermal helium desorption spectrum. They thought one was due to helium-vacancyimpurity clusters and the other was corresponding to helium trapping into pre-existing traps, such as fine-size precipitates.     

Residual stress analysis of joints of ceramics and metals

Development of reliable bonding techniques for ceramics and metals is considered to be very important for more useful applications of ceramics to machinery parts. However, a high thermal stress concentration occurs at the corner of bonded interface in ceramics during the bonding process. This occurs because of the difference in thermal properties of the bond materials and reduces the strength of the bonded joint considerably.The authors have been investigating various methods for effectively decreasing this stress concentration. In this paper, they present theoretical and experimental evidence that the stress concentration can be successfully diminished by varying the apex angle of joints. It is found that the tensile strength of joints increases as the apex angle of metals decreases from 90 deg to 45 deg. It also increases with increasing the apex angle of metals. Numerical calculations confirm these experimental results and the proposed procedure may be useful in the design and manufacture dissimilar joints.Paper was presented at the 1992 SEM Spring Conference on Experimental Mechanics held in Las Vegas, NV on June 8–11.     

Halogen catalyzed acetylenic oxy-cope rearrangement in N-methyl-2-pyrrolidone solvent a new industrial process for pseudoionone and its analogues

Selective synthesis of pseudoionone was achieved by the acetylenic oxy-Cope rearrangement of 4-isopropenyl-3,7-dimethyl-6-octen-1-yn-3-ol ($\text{3}$) in N-methyl-2-pyrrolidone solvent containing a trace of hydrochloric acid, hydrobromic acid, iodine, ammonium bromide and ammonium chloride catalysts.     

Preparation of bromodifluoromethyl sulfide and its conversion to trifluoromethyl sulfide

Bromodifluoromethyl sulfides are prepared by the reaction of mercaptides with CF₂BrX (x=Br,Cl). And treatment of bromodifluoromethyl sulfides with various inorganic fluorides produced trifluoromethyl sulfides.     

Slow release of tetracycline from a mucoadhesive complex with sucralfate for eradication of Helicobacter pylori

Treatment composed of a gastric mucoadhesive antibiotic with slow release drug delivery is expected to be effective for the eradication of Helicobacter pylori (H. pylori). In this study, we evaluated the slow release property of the tetracycline-sucralfate acidic complex. Tetracycline was the antibiotic selected because of its complexation capacity with sucralfate. Sustained release was tested using two different dissolution test methods: paddle and flow-through cell. The adhesive paste formed from the acidic complex displayed a longer sustained release profile of tetracycline using flow-through cell method. The milder conditions of the flow-through cell method better mimicked the fasted state of the stomach, suggesting that the oral administration with fasting is appropriate for the acidic complex. Furthermore, the paste formation protected the tetracycline from decomposition under an acidic condition, which apparently contributes to long-term release. Change in the zeta potential of the acidic complex particles was helpful in clarifying the release mechanisms of the tetracycline. The data indicated that the immediate release of tetracycline in the early stage of the test was indispensable to the subsequent paste formation that enables slow release. If administrated orally with fasting, the acidic complex rapidly adheres to the gastric mucosa and sustains long-term release of the tetracycline to the gastric lumen or mucus layer. This antibiotic delivery mechanism, which requires only a minimum dosage, may be effective for efficient eradication of H. pylori.     

Desulfurization of epidithio-2,5-piperazinedione derivatives and their open chain analogs with triphenyl phosphine

Desulfurization of epidithio-2,5-piperazinediones (6 and 7) by triphenylphosphine in THF gave dimeric compounds (8 and 15). In the presence of water or phenol the desulfurization gave 3-hydroxy (9) or 3-phenoxy-2,5-piperazinedione (10). Reaction of 6c with triphenylphosphine in ethyl vinyl ether yielded 2,5-diazabicyclo[2.2.2]octane-3,6-dione (11), indicating the presence of 1,4-dipole (B) as an intermediate of the desulfurization. Similar cycloaddition products (13 and 14) were obtained by the desulfurization of 6c in the presence of benzofuran, indole or skatole. Desulfurization of open chain disulfides (16, 21, 23 and 25) by triphenylphosphine gave reduced products (17, 22 and 26) and an isoxazole (18), but CC bond formation was not observed.