Publications

Oxygen vacancies in ZnO crystals have significant impacts on its properties and applications. On the basis of ab initio results, we describe the oxygen vacancy distribution and diffusion paths away from the ZnO( 11¯00) surface, aiming to elucidate thermodynamics and kinetic stability of the vacancies and a possible control mechanism. In view of defect engineering and sensor applications, we propose efficient routes to chemically control the equilibrium concentration of the oxygen vacancies at ZnO surfaces by exposure to specific reactive gases: we show that the oxygen vacancy concentration can be increased using sulfur oxide as post-growth treatment, while under exposure to ozone, no significant amount of oxygen vacancies can be sustained on the surface.

PurposeWilms tumor is the commonest renal malignancy in childhood. Survival in high-income countries is approximately 90%, whereas in low-income countries, it is less than 50%. This study assessed treatment outcomes of patients with Wilms tumor at a Kenyan academic hospital.Patients and MethodsWe conducted a retrospective medical record review of all children diagnosed with Wilms tumor between 2010 and 2012. Data on treatment outcomes and various sociodemographic and clinical characteristics were collected.ResultsOf the 39 patients with Wilms tumor, 41% had event-free survival, 31% abandoned treatment, 23% died, and 5% had progressive or relapsed disease. Most patients presented at an advanced stage: stage I (0%), II (7%), III (43%), IV (40%), or V (10%). The most likely treatment outcome in patients with low-stage (I to III) disease was event-free survival (67%), whereas in those with high-stage (IV to V) disease, it was death (40%). No deaths or instances of progressive or relapsed disease were recorded among patients with low-stage disease; their only reason for treatment failure was abandonment of treatment. Stage of disease significantly affected treatment outcomes (P = .014) and event-free survival estimates (P < .001). Age at diagnosis, sex, duration of symptoms, distance to hospital, and health insurance status did not statistically significantly influence treatment outcomes or event-free survival estimates.ConclusionSurvival of patients with Wilms tumor in Kenya is lower compared with that in high-income countries. Treatment abandonment is the most common cause of treatment failure. Stage of disease at diagnosis statistically significantly affects treatment outcomes and survival.