Preparation of Silicon Carbide and Aluminum Silicon Carbide from a Montmorillonite–Polyacrylonitrile Intercalation Compound by Carbothermal Reduction

Both silicon carbide and aluminum silicon carbide have simultaneously been obtained directly from naturally occurring aluminosilicate by carbothermal reduction for the first time. A precursor of a montmorillonite–polyacrylonitrile (PAN) intercalation compound was heated at 1700°C in Ar. For comparison, montmorillonite–carbon mixtures were similarly heated. α-SiC, β-SiC, and Al₄Si₂C₅ formed from the montmorillonite–PAN intercalation compound. Mainly α-Al₄SiC₄ was obtained with ternary carbides from the montmorillonite–carbon mixtures in addition to a large amount of β-SiC. Hence, aluminum silicon carbide formation was affected by the mixing condition of the starting materials.     

Quantitation of vitamin K in human milk

A quantitative method was developed for the assay of vitamin K in human colostrum and milk. The procedure combines preparative and analytical chromatography on silica gel in a nitrogen atmosphere followed by reversed phase high performance liquid chromatography (HPLC). Two HPLC steps were used: gradient separation with ultraviolet (UV) detection followed by isocratic separation detected electrochemically. Due to co-migrating impurities, UV detection alone is insufficient for identification of vitamin K. Exogenous vitamin K was shown to equilibrate with endogenous vitamin K in the samples. A statistical method was incorporated to control for experimental variability. Vitamin K₁ was analyzed in 16 pooled milk samples from 7 donors and in individual samples from 15 donors at 1 month post-partrum. Vitamin K₁ was present at 2.94±1.94 and 3.15±2.87 ng/mL in pools and in individuals, respectively. Menaquinones, the bacterial form of the vitamin, were not detected. The significance of experimental variation to studies of vitamin K in individuals is discussed.     

Lysozyme requires fluctuation of the active site for the manifestation of activity

Mutations around His15 which lie far away from the active site,stimulated glycol chitin activity of lysozyme at physiologicaltemperature. Del-Argl4Hisl5 lysozyme, a mutant lysozyme whoseArgl4 and Hisl5 were deleted together, and has the highest activityamong these mutant lysozymes, had a similar binding abilityto a trimer of N-acetyl-glucosamine, a substrate analogue, relativeto native lysozyme. This suggests that the increased activitywas due to an increased k_cat in the catalysis reaction. TheH-D exchange rate of the N-1 proton in the Trp63 which is locatedin the active site cleft, was enhanced in the Del-Argl4Hisl5lysozyme, while 2-D proton NMR analysis revealed no conformationalchange around Trp63. We conclude that some sort of fluctuationat the active site might be required for the manifestation ofactivity. This theory is supported by the finding that the Del-Argl4Hisl5lysozyme showed a shift in temperature dependency of activityto lower temperatures compared with that of native lysozyme.     

The structure of acetylene flames for diamond synthesis

An acetylene flame was photographed with an SIT camera through optical filters, and the signals were Abel transformed to obtain two-dimensional emission-intensity profiles. It was found that the intensive emissions of CH* and C*₂ are localized at the feather boundary, while the OH* emission is localized at the intermediate zone. The structure of the acetylene flame was made clear: it consists of a carbon-radical-rich feather and an oxygen-radical-rich intermediate zone. The carbon-radical concentrations are approximately in equilibrium near the burner exit while they decrease almost linearly via interdiffusion and reactions with the oxygen-radicals in the intermediate zone.Numerical simulations including detailed gaseous and surface reactions reproduced well previous preliminary calculations showing that CH₄ is rapidly produced in the boundary layer near the substrate followed by an increase in CH₃. This result satisfactorily explains the measured dependence of growth rate on the substrate temperature and ratio.     

Detection of a brain aneurysm and a way to search for a brain aneurysm aimed at the development of a system to simulate an operation

In this article, a system is proposed for a simulated operation which would help a trainee surgeon to perform a medical operation to ensure that a cerebral aneurysm does not burst. The physician will have acquired empirical medical technologies from operations in traditional clinical teaching. However, there is a problem with safety and the burden to the patient. Therefore, recently a new training approach for a simulated medical operation using virtual reality has been explored. With the aim of developing a simulated system for a medical operation for a cerebral aneurysm, we considered the necessary functions such as detecting the brain aneurysm that is the target of the operation, and searching for a suitable blood vessel to make a plan for the operation.     

Design of a Four-Element, Hollow-Cube Corner Retroreflector for Satellites by use of a Genetic Algorithm

A four-element retroreflector was designed for satellite laser ranging and Earth-satellite-Earth laser long-path absorption measurement of the atmosphere. The retroreflector consists of four symmetrically located corner retroreflectors. Each retroreflector element has curved mirrors and tuned dihedral angles to correct velocity aberrations. A genetic algorithm was employed to optimize dihedral angles of each element and the directions of the four elements. The optimized four-element retroreflector has high reflectance with a reasonably broad angular coverage. It is also shown that the genetic algorithm is effective for optimizing optics with many parameters.     

A Linear Algorithm for Computing the Homography from Conics in Correspondence

This paper presents a study, based on conic correspondences, on the relationship between two perspective images acquired by an uncalibrated camera. We show that for a pair of corresponding conics, the parameters representing the conics satisfy a linear constraint. To be more specific, the parameters that represent a conic in one image are transformed by a five-dimensional projective transformation to the parameters that represent the corresponding conic in another image. We also show that this transformation is expressed as the symmetric component of the tensor product of the transformation based on point/line correspondences and itself. In addition, we present a linear algorithm for uniquely determining the corresponding point-based transformation from a given conic-based transformation up to a scale factor. Accordingly, conic correspondences enable us to easily handle both points and lines in uncalibrated images of a planar object.     

Shear viscosity of the B phase of superfluid3He

The shear viscosity (T) in the Balian-Werthamer (BW) state of superfluid ³ He is calculated variationally throughout the region 0t 1(t=T/T _c) from the transport equation for Bogoliubov quasiparticles. Coherence factors are treated exactly in the calculation of the collision integral. The numerical result for =_s= _s(T)/_n(T_c) agree very well with experiment in the range 0.8t1.0. Analytic expressions = 0.577 (1–1.0008t) and =1–(23/64) [=(T)/k _B T] are obtained in the low-temperature region and in the vicinity ofT _c, respectively. From the numerical analysis it is shown that the latter equation is valid only in the temperature range 0.9997t1.0.Supported by the Research Institute for Fundamental Physics, Kyoto University.     

MOSAIC for multiple-reward environments

Reinforcement learning (RL) can provide a basic framework for autonomous robots to learn to control and maximize future cumulative rewards in complex environments. To achieve high performance, RL controllers must consider the complex external dynamics for movements and task (reward function) and optimize control commands. For example, a robot playing tennis and squash needs to cope with the different dynamics of a tennis or squash racket and such dynamic environmental factors as the wind. In addition, this robot has to tailor its tactics simultaneously under the rules of either game. This double complexity of the external dynamics and reward function sometimes becomes more complex when both the multiple dynamics and multiple reward functions switch implicitly, as in the situation of a real (multi-agent) game of tennis where one player cannot observe the intention of her opponents or her partner. The robot must consider its opponent's and its partner's unobservable behavioral goals (reward function). In this article, we address how an RL agent should be designed to handle such double complexity of dynamics and reward. We have previously proposed modular selection and identification for control (MOSAIC) to cope with nonstationary dynamics where appropriate controllers are selected and learned among many candidates based on the error of its paired dynamics predictor: the forward model. Here we extend this framework for RL and propose MOSAIC-MR architecture. It resembles MOSAIC in spirit and selects and learns an appropriate RL controller based on the RL controller's TD error using the errors of the dynamics (the forward model) and the reward predictors. Furthermore, unlike other MOSAIC variants for RL, RL controllers are not a priori paired with the fixed predictors of dynamics and rewards. The simulation results demonstrate that MOSAIC-MR outperforms other counterparts because of this flexible association ability among RL controllers, forward models, and reward predictors.