RESUMEN
A detailed computational study on the reaction mechanisms of the thermal activation of methane by the bare complex [Ni(H)(OH)](+) has been conducted. The experimentally observed reaction features, i.e. the ligand exchange Ni(H) â Ni(CH(3)), the H/D scrambling between the incoming methane and the hydrido ligand of the nickel complex, the spectator-like behavior of the OH ligand, and the relatively moderate reaction efficiency of 6% relative to the collision rate of the ion/molecule reaction, can be explained by considering three competing mechanisms, and a satisfactory agreement between experiment and theory has been found.
RESUMEN
BACKGROUND: As a result of the high prevalence, basal cell carcinoma (BCC) causes a significant and expensive health care problem. OBJECTIVE: In this study, we evaluate the proportional increase in BCC by histological subtype over the last two decades. METHODS: We retrospectively reviewed all primary histological confirmed BCCs diagnosed in the Maastricht University Medical Centre in The Netherlands in the years 1991, 1999 and 2007. RESULTS: An annual increase of the number of BCCs of 7% for both genders was shown. The age-standardized incidence rates for BCC increased between 1991 and 2007 from 54.2 to 162.1 per 100, 000 men and from 61.7 to 189.8 per 100, 000 women. The proportion of superficial BCC increased significantly from 17.6% to 30.7%. CONCLUSION: The incidence of BCC is continuing to increase this century. The observed shift to the superficial histological subtype, which can be treated non-surgically, might reduce the workload in the busy dermatologists practice.