An investigation has been undertaken into the oxidation behaviour of manganese-containing Fe-28% Cr alloys in oxygen at 800" and 1OOO"C. The presence of the tertiary element has a detrimental effect on the oxidation resistance, resulting in enhanced scale-growth rates during isothermal exposure and increased incidences of scale failure at temperature. This is largely due to relatively rapid rates of diffusion of manganese across the Cr203 scale and formation of MnCrzOd spinel on its outer surface. The scale on Fe-28% (31% Mn consists of a layer of Cr203, containing a small concentration of manganese, with an outer layer of the spinel oxide. During the early stages, an inner layer of the spinel also develops, but, eventually, this almost completely disappears as the manganese diffuses into the outer scale. A similar scale forms on Fe-26% 0 3 % Mn, but the higher manganese concentration enables a significant amount of this element to be retained in the inner regions. The overall growth rate of the scale is significantly faster than on Fe-28% Cr or the 1% Mn-containing alloy.

Aim: To investigate methods for identifying specific cyclophilin D (CypD) inhibitors derived from quinoxaline, thus developing possible lead compounds to inhibit mitochondrial permeability transition (MPT) pore opening. Methods: Kinetic analysis of the CypD/inhibitor interaction was quantitatively performed by using surface plasmon resonance (SPR) and fluorescence titration (FT) techniques. IC 50 values of these inhibitors were determined by PPIase inhibition activity assays. Results: All the equilibrium dissociation constants (K D ) of the seven compounds binding to CypD were below 10 µmol/L. The IC 50 values were all consistent with the SPR and FT results. Compounds GW2, 5, 6, and 7 had high inhibition activities against Ca 2+ -dependent rat liver mitochondrial swelling and Ca 2+ uptake/release. Compound GW5 had binding selectivity for CypD over CypA. Conclusion: The agreement between the measured IC 50 values and the results of SPR and FT suggests that these methods are appropriate and powerful methods for identifying CypD inhibitors. The compounds we screened using these methods (GW1-7) are reasonable CypD inhibitors. Its potent ability to inhibit mitochondrial swelling and the binding selectivity of GW5 indicates that GW5 could potentially be used for inhibiting MPT pore opening.

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The influence of silicon on the oxidation of Fe‐14% Cr and Fe‐28% Cr has been studied at high temperature, with particular emphasis on the development and nature of the healing SiO2 layer. In general, silicon is a less effective addition than aluminium to these alloys in improving oxidation resistance because SiO2 grows at a lower rate than α‐Al2O3. Hence, silicon is a less successful oxygen secondary getter and development of a complete healing layer of SiO2 is less rapid than that of α‐Al2O3 on a corresponding aluminium‐containing alloy. Nonetheless, the addition of only 1% Si to Fe‐28% Cr causes a marked reduction in the overall oxidation rate, particularly by facilitating development of the Cr2O3 scale. Precipitates of SiO2 form at the alloy/scale interface. These grow inwards and laterally until they eventually link up to establish a continuous healing layer at the interface after several hundred hours exposure at 1000°C. Similar features are observed for Fe‐14% Cr‐3% Si but the healing SiO2 layer develops after a much shorter time for Fe‐14% Cr‐10% Si, due to the high silicon availability. In every case, the healing layer has been shown to be amorphous SiO2. Although this phase is very protective during isothermal oxidation, it is a site of weakness during cooling and scale spallation is very extensive from specimens where the SiO2 is continuous, with failure occurring cohesively within that layer. Ion implantation of silicon into Fe‐14% Cr and Fe‐28% Cr gives a reduced oxidation rate due to facilitation of a more rapid establishment of a Cr2O3 scale. Similar implantation of yttrium into the ternary alloys assists in development of the silicon‐containing oxide layer, possibly associated with an influence on the nucleation of the oxide precipitates in the early stages of exposure.

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