High temperature oxidation behaviour of Nb and HfO2 coatings on ZrB2

ZrB2 has a unique combination of properties such as high melting point (>3000°C) and low theoretical density, high strength and elastic modulus which makes itself a very attractive candidate for ultra-high temperature applications. However, its’ oxidation resistance is poor above 800°C which limits its application for aero-propulsion and hypersonic flight applications. Few studies have shown that the addition of transition metals into the ZrB2 material could improve the oxidation behaviour at high temperatures. In this study, two different materials were applied as oxidation protective coatings by means of magnetron sputtering technique on top of ZrB2 : the transition metal Nb and HfO2. The oxidation studies were performed at 1500 and 1600°C in a box furnace under synthetic air atmosphere for different times. Both coatings have shown promising results and the ZrO2 scale growth was drastically reduced. Formation of mixed oxides comprising of Nb and ZrO2 at the surface has reduced the oxygen transport at the ZrB2 reaction front. Similarly, HfO2 has acted as a barrier to the oxygen transport and a lower oxidation rate was achieved

Candida bloodstream infections in intensive care units: analysis of the extended prevalence of infection in intensive care unit study

Item does not contain fulltextOBJECTIVES: To provide a global, up-to-date picture of the prevalence, treatment, and outcomes of Candida bloodstream infections in intensive care unit patients and compare Candida with bacterial bloodstream infection. DESIGN: A retrospective analysis of the Extended Prevalence of Infection in the ICU Study (EPIC II). Demographic, physiological, infection-related and therapeutic data were collected. Patients were grouped as having Candida, Gram-positive, Gram-negative, and combined Candida/bacterial bloodstream infection. Outcome data were assessed at intensive care unit and hospital discharge. SETTING: EPIC II included 1265 intensive care units in 76 countries. PATIENTS: Patients in participating intensive care units on study day. INTERVENTIONS: None. MEASUREMENT AND MAIN RESULTS: Of the 14,414 patients in EPIC II, 99 patients had Candida bloodstream infections for a prevalence of 6.9 per 1000 patients. Sixty-one patients had candidemia alone and 38 patients had combined bloodstream infections. Candida albicans (n = 70) was the predominant species. Primary therapy included monotherapy with fluconazole (n = 39), caspofungin (n = 16), and a polyene-based product (n = 12). Combination therapy was infrequently used (n = 10). Compared with patients with Gram-positive (n = 420) and Gram-negative (n = 264) bloodstream infections, patients with candidemia were more likely to have solid tumors (p < .05) and appeared to have been in an intensive care unit longer (14 days [range, 5-25 days], 8 days [range, 3-20 days], and 10 days [range, 2-23 days], respectively), but this difference was not statistically significant. Severity of illness and organ dysfunction scores were similar between groups. Patients with Candida bloodstream infections, compared with patients with Gram-positive and Gram-negative bloodstream infections, had the greatest crude intensive care unit mortality rates (42.6%, 25.3%, and 29.1%, respectively) and longer intensive care unit lengths of stay (median [interquartile range]) (33 days [18-44], 20 days [9-43], and 21 days [8-46], respectively); however, these differences were not statistically significant. CONCLUSION: Candidemia remains a significant problem in intensive care units patients. In the EPIC II population, Candida albicans was the most common organism and fluconazole remained the predominant antifungal agent used. Candida bloodstream infections are associated with high intensive care unit and hospital mortality rates and resource use