Influence of fabrication conditions on the structural characteristics and the magnetic properties of FeAl2O4

We report a systematic evaluation of the magnetic properties of FeAl₂O₄ focusing on the relationship between the fabrication conditions and its structural characteristics, in order to improve ceramics processing in applications of this material. For this purpose, the most important factor to control is the inversion parameter, expressed as y in the (Fe_1−yAl_y)(Al_1−y/2Fe_y/2)₂O₄ composition, which is relatively high for the spinel aluminate of a transition metal. The magnetic properties of these samples all show the spin glass phenomenon at low temperatures, and the cusp temperature depends systematically on this y value. This means that the evaluation of these magnetic properties will be an effective way to predict some characteristics of product FeAl₂O₄. Additionally, this study found an anomaly in the structural and magnetic characteristics of FeAl₂O₄ fabricated at a low temperature. This is thought to originate in a tiny and a small amount of impurity. It will be key for discussing the quality of chemically synthesized FeAl₂O₄, which is typically produced at low temperatures.     

Structural Basis for the Activation of the Cobalt-Carbon Bond and Control of the Adenosyl Radical in Coenzyme B12 Catalysis

Adenosylcobalamin (AdoCbl), or coenzyme B₁₂, is a naturally occurring organometallic compound that serves as a cofactor for enzymes that catalyze intramolecular group-transfer reactions and ribonucleotide reduction in a wide variety of organisms from bacteria to animals. AdoCbl-dependent enzymes are radical enzymes that generate an adenosyl radical by homolysis of the coenzyme's cobalt-carbon (Co−C) bond for catalysis. How do the enzymes activate and cleave the Co−C bond to form the adenosyl radical? How do the enzymes utilize the high reactivity of the adenosyl radical for catalysis by suppressing undesirable side reactions? Our recent structural studies, which aimed to solve these problems with diol dehydratase and ethanolamine ammonia-lyase, established the crucial importance of the steric strain of the Co−C bond and conformational stabilization of the adenosyl radical for coenzyme B₁₂ catalysis. We outline here our results obtained with these eliminating isomerases and compare them with those obtained with other radical B₁₂ enzymes.     

Influence of the structure of polysulphide additives on the shiftability of manual transmissions

The shiftability of manual transmissions is known to be strongly affected by the nature of the transmission oil. When conventional sulphur—phosphorus (SP) additives are used in the oil, gear clashing, sticking, and other problems occur. As reported previously, these problems are caused mainly by the polysulphide used in the SP additives. This paper reports on a study of the effect of the structure of the polysulphide's hydrocarbon chain on the synchromesh characteristics. It is found that polysulphides with long hydrocarbon chains have high kinematic friction coefficients and low static friction coefficients. It is also shown that this phenomenon occurs because of the adsorption of the polysulphide on to the copper alloy of which the gear synchroniser ring is made. By using a polysulphide with a long hydrocarbon chain it is possible to develop transmission oils that have superior load‐carrying capacity and better shiftability even when compared with the latest transmission oils that contain metallic detergents.