ESR observations of paramagnetic centers in intrinsic hydrogenated microcrystalline silicon

Paramagnetic centers in hydrogenated microcrystalline silicon, µc-Si:H have been studied using dark and light-induced electron-spin resonance (ESR). In dark ESR measurements only one center is observed. The g values obtained empirically from powder-pattern line-shape simulations are g=2.0096 and g'=2.0031. We suggest that this center may be due to defects in the crystalline phase. During illumination at low temperatures, an additional ESR signal appears. This signal is best described by two powder patterns indicating the presence of two centers. One center is asymmetric (gi=1.999, g'=1.996), while the other is characterized by large, unresolved broadening such that unique g values cannot be obtained. The average g value for this center is 1.998. The light-induced signal, which we interpret as coming from carriers trapped in the band tails at the crystalline grain boundaries, remains for at least several minutes after the light is turned off. Although the time scales of the decay curves are very different for two samples prepared by different techniques, both decays can be fitted using the assumption of recombination due to distant pairs of electrons and holes trapped in localized band-tail states

Deprivation and colorectal cancer surgery: longer-term survival inequalities are due to differential postoperative mortality between socioeconomic groups

Background: Deprivation is associated with poorer survival after surgery for colorectal cancer, but determinants of this socioeconomic inequality are poorly understood.<p></p> Methods: A total of 4,296 patients undergoing surgery for colorectal cancer in 16 hospitals in the West of Scotland between 2001 and 2004 were identified from a prospectively maintained regional audit database. Postoperative mortality (<30 days) and 5-year relative survival by socioeconomic circumstances, measured by the area-based Scottish Index of Multiple Deprivation 2006, were examined.<p></p> Results: There was no difference in age, gender, or tumor characteristics between socioeconomic groups. Compared with the most affluent group, patients from the most deprived group were more likely to present as an emergency (23.5 vs 19.5 %; p = .033), undergo palliative surgery (20.0 vs 14.5 %;p < .001), have higher levels of comorbidity (p = .03), have <12 lymph nodes examined (56.7 vs 53.1 %; p = .016) but were more likely to receive surgery under the care of a specialist surgeon (76.3 vs 72.0 %; p = .001). In multivariate analysis, deprivation was independently associated with increased postoperative mortality [adjusted odds ratio 2.26 (95 % CI, 1.45–3.53; p < .001)], and poorer 5-year relative survival [adjusted relative excess risk (RER) 1.25 (95 % CI, 1.03–1.51;p = .024)] but not after exclusion of postoperative deaths [adjusted RER 1.08 (95 %, CI .87–1.34;p = .472)].<p></p> Conclusions: The observed socioeconomic gradient in long-term survival after surgery for colorectal cancer was due to higher early postoperative mortality among more deprived groups.<p></p&gt