Fabrication of Bi2Sr2CaCu2O x /Ag superconducting tape using a screen-printing method

High- T _c superconducting Bi₂Sr₂CaCu₂O _x /Ag tape was successfully fabricated using a screen-printing method and a partial-melting process. A highly oriented layer structure was achieved and confirmed by X-ray diffraction (XRD), pole-figure measurement and scanning electron microscopy (SEM). The critical current density, J _c, of the tape at 77 K, 0 T, was about 20000 A cm^–2. High-temperature XRD was used to clarify the mechanism of the grain alignment. An aligned structure of the 2212 phase was originated from Bi-free compounds, such as (Sr,Ca)CuO₂ and (Sr,Ca)₂CuO₃ developed during a holding stage at 875°C.     

Controlling chaos in a switched arrival system

We consider a switched arrival system with three buffers. We assume that the input rate of work and the processing time per unit are constant. Chase et al. show that the system is chaotic. In this article, we propose a method for stabilization of an unstable periodic orbit embedded in a chaotic attractor by changing the limited continuous processing time.     

Studies on thermal degradation of synthetic polymers. XV. Estimation of the product yield on the basis of intensity function for thermal gasification of isotactic and atactic polypropylenes

The kinetic equation for the pyrolysis gasification reaction of isotactic and atactic polypropylenes has been established. The difference in tacticity of the samples does not much affect the kinetic parameters. The exponent a of the intensity function I_F = Tδ^a (K·sec^a), concerning the severity of decomposition conditions, has been approximated as 0.039 (isotactic) and 0.040 (atactic), respectively from the kinetic parameters in this experiment. The calculated values of the product yield from Arrhenius equations, k = 2.0 × 10¹⁰ exp(?40.9 × 10³/RI_F) (isotactic) and k = 1.2 × 10¹⁰ exp(–41.4 × 10³/RI_F) (atactic), for the I_F standard agree with the experimental values.     

Efficiency of hydrogen transferring liquefaction of a subbituminous coal using hydrogenated fluoranthene for short contact time at high temperature and low pressure

An Australian subbituminous coal (Wandoan) was effectively liquefied at 490 and 510 °C under nitrogen pressure of 2.5 MPa for 1.0–7.5 min using 1, 2, 3, 3a-tetrahydrofluoranthene (4HFL) as a hydrogen-donating solvent. The yields of oil and asphalthene could be as high as 58 and 24 wt%, respectively. The content of 4HFL was very influential on the oil yield although under appropriate liquefaction conditions, a considerable amount remained after reaction. The kinetics of the reaction and analytical study of the products and the solvent suggest consecutive as well as instantaneous depolymerization in the process. The coking or recondensation reaction was very rapid after 4HFL was consumed, confirming the efficacy of the short contact time liquefaction.     

Classic: A hierarchical clustering algorithm based on asymmetric similarities

The nearest neighbors relation (NNR) is defined in terms of a given asymmetric matrix of similarities of data items. This paper presents a new clustering algorithm, called CLASSIC, based on an iteratively defined nested sequence of NNRs. CLASSIC has been applied to various types of gestalt clustering problems. For CLASSIC applications in which asymmetric similarities are not available a priori, this paper also introduces a method for obtaining asymmetric similarities from Euclidean distances. This method has been used in the detection of gestalt clusters by CLASSIC.     

Correlation between electrical properties and thermal stability in Ni-Si-B metallic glasses

The temperature coefficient of resistivity (TCR), specific resistivity _{3000 K}, crystallization temperatureT _x and activation energyE _a for crystallization in various Ni-Si-B metallic glasses were measured and relationships among them were examined. It was found that the values of TCR decreased with increasing metalloid (Si, B) contents and by substituting silicon atoms for boron atoms, but conversely the values of _{300 K},T _x andE _a increased. A very close correlation was observed between TCR andT _x orE _a. The compositional dependences of TCR, _300K,T _x andE _a and good correlations among them can be explained qualitatively by considering the short-range structure and the directional chemical bonding between nickel and silicon or boron atoms.     

Fabrication of Transparent Tellurite Glasses Containing Potassium Niobate Crystals by an Incorporation Method

To fabricate transparent oxide glasses containing ferroelectric KNbO₃ crystals, a new method in which KNbO₃ particles are directly incorporated into TeO₂─K₂O─Nb₂O₅ glasses has been developed. Transparent TeO₂-based glasses containing KNbO₃ crystals with a diameter of ∼ 10 μm have been first successfully fabricated by adjusting temperature and time for incorporation. A small difference in the refractive indexes, n , between TeO₂-based matrix glasses ( n = 2.0) and incorporated KNbO₃ crystals ( n = 2.21) is a significant reason for the transparency. This new method is applicable for the fabrication of new transparent glasses containing other functional materials with high refractive indexes.     

Neural Model Approach to the Basic Law of Psychophysics

Stevens’ law, which is one of the well-known psychophysical laws, suggests that the perceived intensity R of a biological system is proportional to the power of the stimulus strength I, R ∝ I ⁿ . In order to realize a self-sustainable system that adapts to changes of the environment, it is important to understand the neural mechanism behind this law. Here, we propose a new neural scheme based on the shunting short-term memory (STM) model with the physiological properties of the nervous system, and examine the relation between the neural system and Stevens’ law through computer simulations of the firing rate f with respect to the stimulus strength I. The simulations showed that the feedback-inputting connectivity plays an important role in reproducing the n > 1 and n < 1 cases of Stevens’ law.     

The Metabolic Fate of ortho-Quinones Derived from Catecholamine Metabolites

ortho-Quinones are produced in vivo through the oxidation of catecholic substrates by enzymes such as tyrosinase or by transition metal ions. Neuromelanin, a dark pigment present in the substantia nigra and locus coeruleus of the brain, is produced from dopamine (DA) and norepinephrine (NE) via an interaction with cysteine, but it also incorporates their alcoholic and acidic metabolites. In this study we examined the metabolic fate of ortho-quinones derived from the catecholamine metabolites, 3,4-dihydroxyphenylethanol (DOPE), 3,4-dihydroxyphenylethylene glycol (DOPEG), 3,4-dihydroxyphenylacetic acid (DOPAC) and 3,4-dihydroxyphenylmandelic acid (DOMA). The oxidation of catecholic substrates by mushroom tyrosinase was followed by UV-visible spectrophotometry. HPLC analysis after reduction with NaBH₄ or ascorbic acid enabled measurement of the half-lives of ortho-quinones and the identification of their reaction products. Spectrophotometric examination showed that the ortho-quinones initially formed underwent extensive degradation at pH 6.8. HPLC analysis showed that DOPE-quinone and DOPEG-quinone degraded with half-lives of 15 and 30 min at pH 6.8, respectively, and >100 min at pH 5.3. The major product from DOPE-quinone was DOPEG which was produced through the addition of a water molecule to the quinone methide intermediate. DOPEG-quinone yielded a ketone, 2-oxo-DOPE, through the quinone methide intermediate. DOPAC-quinone and DOMA-quinone degraded immediately with decarboxylation of the ortho-quinone intermediates to form 3,4-dihydroxybenzylalcohol (DHBAlc) and 3,4-dihydroxybenzaldehyde (DHBAld), respectively. DHBAlc-quinone was converted to DHBAld with a half-life of 9 min, while DHBAld-quinone degraded rapidly with a half-life of 3 min. This study confirmed the fact that ortho-quinones from DOPE, DOPEG, DOPAC and DOMA are converted to quinone methide tautomers as common intermediates, through proton rearrangement or decarboxylation. The unstable quinone methides afford stable alcoholic or carbonyl products.