Chemical, Structural, and Morphological Changes of a MoVTeNb Catalyst during Oxidative Dehydrogenation of Ethane

MoVTeNb mixed oxide, a highly active and selective catalyst for the oxidative dehydrogenation of ethane to produce ethylene, exhibits the so-called M1 and M2 crystalline phases. The thermal stability of the MoVTeNb catalytic system was assessed under varying reaction conditions; to this end, the catalyst was exposed to several reaction temperatures spanning from 440 to 550 °C. Both the pristine and spent materials were analyzed by several characterization techniques. The catalyst was stable below 500 °C; a reaction temperature of ≥500 °C brings about the removal of tellurium from the intercalated framework channels of the M1 crystalline phase. Rietveld refinement of X-ray diffraction patterns and microscopy results showed that the tellurium loss causes the progressive partial destruction of the M1 phase, thus decreasing the number of active sites and forming a MoO2 crystalline phase, which is inactive for this reaction. Raman spectroscopy confirmed the MoO2 phase development as a function of reaction temperature. From highresolution transmission electron microscopy and energy-dispersive X-ray spectroscopy analyses it was noticed that tellurium departure occurs preferentially from the end sides of the needlelike M1 crystals, across the [001] plane. Detailed analysis of a solid deposited at the reactor outlet showrf that it consisted mainly of metallic tellurium, suggesting that the tellurium detachment occurs via reduction of Te4+ to Te0 due to a combination of reaction temperature and feed composition. Thus, in order to sustain the catalytic performance exhibited by MoVTeNb mixed oxide, hot spots along the reactor bed should be avoided or controlled, maintaining the catalytic bed temperature below 500 °C.This work was financially supported by the Instituto Mexicano del Petroleo.Valente, JS.; Armendariz-Herrera, H.; Quintana-Solorzano, R.; Del Angel, P.; Nava, N.; Masso Ramírez, A.; López Nieto, JM. (2014). Chemical, Structural, and Morphological Changes of a MoVTeNb Catalyst during Oxidative Dehydrogenation of Ethane. ACS Catalysis. 4:1292-1301. doi:10.1021/cs500143jS12921301

Human immunodeficiency virus-related cancer in children: Incidence and treatment outcome - Report of the Italian Register

Purpose: to outline the incidence, presenting features, treatment response, and outcome of human immunodeficiency virus (HIV)-associated malignancies in infancy and childhood, together with the estimated risk of HIV-associated cancer in children born to mothers infected with HIV. Patients and Methods: The Italian Register for HN Infection in Children collected data by specific registration and follow-up forms. By March 1999, 5,060 children were recruited, including 4,889 with perinatal exposure to HIV-1. Overall, 1,331 infected children were enrolled onto the Register and classified according to current Centers for Disease Control criteria; of them, 1,163 were vertically infected (24% of those with perinatal exposure). Of these 1,163, 569 (49%) were considered to have been prospectively followed-up since they had been registered at birth or within the first 3 months of age. Results: Of the 1,331 children observed for a median time of 6.5 years, 35 developed 36 malignancies, four of which occurred in patients with blood-borne risk. For the 1,163 vertically infected children, the cumulative number of years of observation was 7,178 child-years and the cumulative incidence of HIV-associated tumors was 4. 18 per 1,000 children/yr (95% confidence interval [CI], 2.92 to 5.98). When only the 569 vertically infected children prospectively followed up since birth were considered, the cumulative number of years of observation was 2,803 child-years. In this group, 10 rumors were observed, with a cumulative incidence of HIV-associated tumors of 3.57 per 1,000 children per year (95% CI, 1.92 to 6.63). Conclusion: The risk of cancer was significantly higher but nor restricted to symptomatic and/or immune-compromised children. Cancer-directed treatment should be given promptly to these patients, who have ct fair chance to survive their tumor in view of potential highly aggressive antiretroviral therapy-associated improvement in survival and quality of life