Mechanistic Aspects of Catalytic Steam Reforming of Biomass-related Oxygenates

Catalytic steam reforming of acetic acid, as a model oxygenate derived from biomass, was studied over supported Pt catalysts. It is suggested that both Pt and the support are involved in the activation of acetic acid and water, respectively. This manifests in different intrinsic activity for Pt when anchored on different supports. Accordingly, the reforming proceeds most likely at the boundary between the Pt and the support and the number of Pt sites that are in the close proximity of the support determine hydrogen formation rates.     

Diffusion of titanium in copper

Interdiffusion coefficients in copper-titanium alloys have been determined by Matano's method in the temperature range between 973 and 1283 K on (pure Cu)-(Cu-1.98 at. pct Ti alloy) and (pure Cu)-(Cu-2.91 at. pct Ti alloy) couples. Temperature dependence of the impurity diffusion coefficient of titanium in copper, determined by extrapolation of the concentration dependence of the interdiffusion coefficient to zero mole fraction of titanium, is expressed by the following Arrhenius equation along with the probable errors:D _Ti/Cu=(0.693 _−0.135 ^+0.169 )×10⁻⁴exp[−(196±2)kJ mol⁻¹/RT] m²/s. The difference in the activation energies for the impurity diffusion of the 3d-transition metals and self-diffusion in copper has been calculated by applying LeClaire's model with the oscillating potential of the impurity atom in copper. The calculated values agree well with the experimental values including the present one. Kazutomo Hoshino, formerly Graduate Student, Tohoku University     

Increased activity of oleate-dependent type phospholipase D during actinomycin D-induced apoptosis in Jurkat T cells

Apoptosis is an active form of cell death that can be induced by a wide variety of agents and conditions. In response to actinomycin D, hydrogen peroxide (H2O2), or TNF-alpha, Jurkat T cells underwent typical apoptosis. Phospholipase D (PLD) activity in intact cells determined by phosphatidylbutanol generation was up-regulated by these agents. The PLD activation was in a time-dependent manner during apoptosis. It was also shown that the PLD activity measured by using exogenous substrate in the lysate from apoptotic cells was higher than that in the lysate from control untreated cells. The PLD activity in lysate from control untreated cells was stimulated by unsaturated fatty acids (UFA), but not by guanosine 5'-O-(3-thiotriphosphate). However, the PLD activity in the apoptotic cell lysate was no longer enhanced by the addition of oleate, suggesting that the increased PLD activity during apoptosis was attributed to the PLD of UFA-dependent type, but not the small G protein-dependent one. In fact, the release of free UFA was increased during apoptosis. The caspase inhibitors, z-DEVD and z-VAD, effectively suppressed PLD activation and apoptosis, but UFA release was unaffected. These results suggest the possibility that UFA-dependent type PLD may be implicated in apoptotic process in Jurkat T cells. This is the first demonstration that the PLD of UFA-dependent type would be involved in cellular responses.     

Preparation of new hydrophilic and durable porous polymer particles

A preparation method for new highly durable hydrophilic porous polymer particles consisting of acrylic monomers and copolymerizable cross-linking agents was studied. In the case of using only a two-functional acrylic monomer as the cross-linking agents, the obtained particles had a relatively low mechanical strength, but by the addition of a multifunctional acrylic monomer into the above system, it was found that the porous particles obtained became highly durable and showed excellent mechanical strength of more than 500 kg/cm². The effect of preparation conditions on the specific surface area of these particles consisting of three components was investigated from the following viewpoints: The first was aimed at the stabilized phase of droplets consisting of monomer/cross-linkers/porogen under various conditions of aqueous poly(vinyl alcohol) (PVA) media, and the second was the effect of composition changes of the monomer and cross-linkers on the inner porous structure of the particles obtained. Thus, the specific surface area of the particles was found to be significantly affected both by the degree of saponification (DS) of PVA and by the change of composition. On the other hand, the average pore radius of typical particles obtained in this way can be controlled in the range from 40 to 120 Å by the weight ratio of chlorobenzene as the porogen. Furthermore, the mechanical stability and durability of the column packed with the porous particles obtained were discussed. © 1993 John Wiley & Sons, Inc.     

Mechanism of puffing and the role of puffing inhibitors in the graphitization of electrodes from needle cokes

A mechanism of puffing that occurs during graphitization of needle coke in the electrode is proposed based on the experimental results in the literature. Gases may evolve from within needle coke grains via porosity, causing pore walls to expand irreversibly when they are softened during graphitization. Hence, extents of puffing are influenced by rate and temperature range of gas evolution, the nature of evolved gases, location of the evolved heteroatoms such as sulfur and nitrogen in the coke, and the structure (especially grain size), porosity (pores and cracks), and preferred orientation of the coke, because these factors are related to the pressure induced by the evolved gas, timing for the softening of the coke and gas evolution and the resistivity of the wall against the pressure. Porosity within a coke grain can be modified by the coke derived from binder and impregnation pitches that can diffuse into the porosity of filler coke in the electrode. The graphitization also leads to shrinkage of the carbon. Hence, the size of the electrode is influenced by both puffing and shrinkage, these having opposing effects. The extent of puffing can be described semi-quantitatively in terms of influential factors described above. Thus, it is understandable that the puffing increased the porosity in a certain range (0.1–1 μm) and that puffing is suppressed by the increased porosity of 1–100μm. Based on the mechanism, procedures for puffing inhibition are suggested including:

1. 1. moderate acceleration of graphitization

2. 2. capture of heteroatoms to be liberated

3. 3. controled gasification to increase porosity of the filler cokes

4. 4. removal of heteroatoms from the needle coke or its starting feedstock The roles of puffing inhibitors are discussed based on the mechanism of puffing.

Quantitative analysis of mycoflora on commercial domestic fruits in Japan

A comprehensive and quantitative analysis of the mycoflora on the surface of commercial fruit was performed. Nine kinds of fruits grown in Japan were tested. Overall fungal counts on the fruits ranged from 3.1 to 6.5 log CFU/g. The mean percentages of the total yeast counts were higher than those of molds in samples of apples, Japanese pears, and strawberries, ranging from 58.5 to 67.0%, and were lower than those of molds in samples of the other six fruits, ranging from 9.8 to 48.3%. Cladosporium was the most frequent fungus and was found in samples of all nine types of fruits, followed by Penicillium found in eight types of fruits. The fungi with the highest total counts in samples of the various fruits were Acremonium in cantaloupe melons (47.6% of the total fungal count), Aspergillus in grapes (32.2%), Aureobasidium in apples (21.3%), blueberries (63.6%), and peaches (33.6%), Cladosporium in strawberries (38.4%), Cryptococcus in Japanese pears (37.6%), Penicillium in mandarins (22.3%), and Sporobolomyces in lemons (26.9%). These results demonstrated that the mycoflora on the surfaces of these fruits mainly consists of common pre- and postharvest inhabitants of the plants or in the environment; fungi that produce mycotoxins or cause market diseases were not prominent in the mycoflora of healthy fruits. These findings suggest fruits should be handled carefully with consideration given to fungal contaminants, including nonpathogenic fungi, to control the quality of fruits and processed fruit products.     

Structural effects of amphiphiles on Candida rugosa lipase activation by freeze-drying of aqueous solution of enzyme and amphiphile

Lipases co-lyophilized with water-soluble gemini-type amphiphiles were found to have high enzyme activity in nonaqueous media without washing out of the amphiphile with anhydrous organic solvent. In this study, we obtained freeze-dried complexes of Candida rugosa lipase (CRL) with six water-soluble twin glusitol-headed amphiphiles bearing different types of hydrophobic tails, including newly synthesized ones, and their transesterification activity in organic solvent was evaluated. The results indicate that the increased enzyme activity upon CRL modification at 200 molar ratio of amphiphile/CRL, which are restricted to the ester-containing amphiphiles, is probably due to the surface activation by the interaction between ester-carbonyl of the amphiphile and phenyl group of the tyrosine residue situated on the surface of the lid in the CRL.