Kinetics of the dissolution of scheelite in aqueous Na4EDTA solutions

The reaction kinetics of the dissolution of pure scheelite (CaWO₄) particles in aqueous Na₄EDTA solutions were studied at atmospheric pressure. As expected, the dissolution rate increased with decreasing initial particle size and with increasing temperature and Na₄EDTA concentration. Further, the dissolution rate decreased as the initial solid-liquid ratio and the ionic strength of the solution were increased. The experimental results do not support the conventional shrinking-core model for a single irreversible reaction. A new shrinking-core model for multiple reactions, composed of a noninstantaneous reversible reaction (scheelite dissociation into the ions Ca²⁺ and WO ₄ ²⁻ ) and an instantaneous irreversible reaction (formation of Ca-EDTA complex), was presented. The observed dependency of the dissolution rate on the relevant operating variables was the same a the theoretical predictions based on the present shrinking-core model. The activation energy was 49800 J mol⁻¹. These findings justify the validity of the assumed kinetic model with the multiple reactions as the rate-controlling step. The dissolution rate expression was obtained as a function of the initial particle size, initial solid-liquid ratio, Na₄EDTA concentration, temperature, and ionic strength of the solution.     

Primary yields and reaction sets with corresponding rate constants for computer simulation of water radiolysis at elevated temperature

The chemical conditions of coolant water in light water reactors are important factors affecting the corrosive environment and the integrity of the structural materials. Computer simulations have commonly been used to predict chemical environment changes due to water radiolysis under extreme conditions. Initial parameters, including the chemical reactions, rate constants, and primary yields of water decomposition by radiolysis, have been reported by several groups in the past few decades. Using a FACSIMILE simulation, the variations caused by utilizing different sets of primary yields of water radiolysis, including γ-rays and fast neutrons, along with the chemical reactions and rate constants at 285 °C were evaluated in this study. The rate constant of the reverse reaction of OH + H₂ → H + H₂O was found to be the main factor controlling the variation between the different sets of chemical reactions and rate constants.     

Fabrication and characterization of fine-grained 316L steel with 2.0 mass% TiC

Development of fine grain 316L with small amount of TiC for high radiation-tolerant performance was tried considering the fabrication process of thermo-mechanical treatments. The materials obtained are UFG316L+2.0 mass% TiC with the grain size of 90–270 nm, depending on the final annealing temperature from 700 ℃ to 900 ℃. The materials were examined by transmission electron microscopy observation, X-ray absorption near-edge structure spectroscopy, high voltage electron microscope electron irradiation and stress corrosion cracking by crevice bent beam method in high-temperature water with 8 ppm dissolved oxygen. The test results showed that the material is generally of excellent quality. Especially void swelling induced by the electron irradiation at 400 ℃ is less than 1/10 compared to the commercial SUS316L.     

Molecular and Neural Mechanism of Dysphagia Due to Cancer

Cancer is one of the most common causes of death worldwide. Along with the advances in diagnostic technology achieved through industry–academia partnerships, the survival rate of cancer patients has improved dramatically through treatments that include surgery, radiation therapy, and pharmacotherapy. This has increased the population of cancer “survivors” and made cancer survivorship an important part of life for patients. The senses of taste and smell during swallowing and cachexia play important roles in dysphagia associated with nutritional disorders in cancer patients. Cancerous lesions in the brain can cause dysphagia. Taste and smell disorders that contribute to swallowing can worsen or develop because of pharmacotherapy or radiation therapy; metabolic or central nervous system damage due to cachexia, sarcopenia, or inflammation can also cause dysphagia. As the causes of eating disorders in cancer patients are complex and involve multiple factors, cancer patients require a multifaceted and long-term approach by the medical care team.     

Palladium‐Catalyzed Arylation of Methylene‐Bridged Polyarenes: Synthesis and Structures of 9‐Arylfluorene Derivatives

In the presence of a catalytic system comprised of palladium(II) acetate and tricyclohexylphosphine, the reaction of fluorene with haloarenes generated 9‐arylfluorenes in good to excellent yields. The scope and limitations of the coupling reaction were investigated. This synthetic protocol is more efficient than conventional methods. A wide range of functional groups, including alkyl, alkoxy, ester, and nitrile, can tolerate the reaction conditions herein. Sterically congested haloarenes also gave satisfactory results. Furthermore, this synthetic method is utilized to prepare 9,9‐diarylfluorenes and tetraarylindenofluorene. Depending on the reaction conditions, the arylation of bowl‐shaped sumanene gave monoarylated sumanene either as the sole product or with another diaryl‐substituted product.     

Production of large‐diameter uniform plasmas and control of electron temperature

In order to produce large‐diameter uniform plasmas, we have proposed two plasma sources: a plane electron‐cyclotron‐resonance (ECR) slotted antenna (PESA) source for ECR plasma production and a modified magnetron‐type (MMT) radio frequency (RF) source for RF plasma production. The PESA has magnet rings behind the slotted antenna to provide the magnetic field for the ECR. The MMT RF source provides high‐density uniform plasmas with the help of the LC resonance of auxiliary electrode placed parallel to the substrate. Both plasma sources produce large‐diameter uniform plasmas exceeding 30 cm in diameter. We have proposed a grid method for electron temperature control. By applying a negative dc voltage to the grid which separates a plasma‐processing region from a plasma production region, the electron temperature is decreased by one order of magnitude in the processing region. The same effect is obtained by changing the mesh size of a floating grid. The change of a slit between two grids also causes variation of the electron temperature. These techniques are quite effective for chemical reaction control in processing plasmas. © 1999 Scripta Technica, Electr Eng Jpn, 130(1): 1–7, 2000     

IMPINGING JET DRYER

ABSTRACT

In coating and gravure printing, an impinging jet nozzle with high thermal efficiency for drying of coated film was developed.

Trial production 0f 40 kinds of nozzle enables to develop a high-performance impinging jet nozzle with heat transfer coefficient 1.5 times larger than that of current slit nozzle, through measurement of heat transfer coefficient, visualizations of air flow and heat transfer, and measuremenu of jet velocity and turbulence distribution. The purpose of the trial production was to expand a range of high heat transfer and promote turbulence compared with the current nozzle.

Paying attention to mass transfer within gravure ink coated film, drying characteristic of the film was analyzed by numerical solution of a set of equations governing the drying process in which concentration dependencies 0f the diffusion coefficient and the equilibrium vapor pressure were considered.

Applying these analyses. an industrial scale dryer with excellent drying efficiency has finally been developed.     

Polarization-Dependent Total-Reflection Fluorescence X-ray Absorption Fine Structure for 3D Structural Determination and Surface Fine Tuning

This short review reports the three dimensional structure analysis of oxide-supported metal species and the origin of the metal-support interaction, using single crystal oxide surfaces and polarization-dependent total-reflection X-ray absorption fine structure (PTRF-XAFS) method. The PTRF-XAFS revealed that metal species interact strongly with oxygen anions of oxide surfaces and that surface pre-modification is a promising way to stabilize the surface monoatomic species of easily-aggregating Cu and Au and to prepare finely-tuned surface metal–organic species with regulated molecular structures and orientations.     

Oxidation and Degradation of Titanium Nitride Ultrafine Powders Exposed to Air

Titanium nitride ultrafine powders were synthesized by an active plasma-metal reaction method. Gas desorption measurements were conducted to estimate the surface chemistry of the powders after exposure to air and storage at room temperature. H₂O, H₂, CO₂, CO, and NH₃ gases were mainly evolved. These gases were considered to be formed by the surface reaction of adsorbed gases on surface oxide of the powders and decomposition of hydroxide-like or ammonialike compounds, which might be produced during a slow oxidation treatment and storage.