Four new tantalum amido precursors (η2-RN(CH2) n NR)Ta(NMe2)3 (where R = Me, n = 2, 1; R = Et, n = 2, 2; R = Me, n = 3, 3; R = Et, n = 3, 4) with chelate diamide ligands and one new tantalum amido ...precursor (η2- t BuNC(NMe2)NEt)Ta(NMe2)4) (5) with a chelate guanidinate ligand were prepared and characterized. Their thermal behavior, especially (NMe2)3Ta(η2-MeN(CH2)2NMe) (1), were investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) experiments to demonstrate the enhancement of their thermal stability and preservation of the volatility as metalorganic chemical vapor deposition (MOCVD) precursors as compared to Ta(NMe2)5 (PDMAT). Introduction of the asymmetric chelate guanidine ligand in complex 5 gave improved volatility as compared with its known isomer (η2- i PrNC(NMe2)N i Pr)Ta(NMe2)4 (6). The crystal structures of 5 and 6 were measured to investigate the correlation between the volatility and intermolecular interactions. The MOCVD of tantalum nitride thin films was successfully achieved using 1. The films are based on field emission scanning electron microscopy (FESEM) and show good adhesion properties. Rutherford backscattering spectrometry (RBS) and X-ray photoelectron spectroscopy (XPS) data suggest that the film deposited using 1 at 500 °C under ammonia has a composition of TaN1.22±0.14 with negligible carbon and oxygen levels. It also shows low resistivity of 1.4 × 103 μΩ cm on SiO2/Si and broad X-ray diffraction (XRD) peaks for the stoichiometric cubic refractory TaN, indicating the potential of 1 becoming an alternative MOCVD precursor for barrier applications.
Elderly patients represent a growing subgroup of cancer patients for whom the role of radiation therapy is poorly defined. Older patients are still clearly underrepresented in clinical trials, ...resulting in very limited high-level evidence. Moreover, elderly patients are less likely to receive radiation therapy in similar clinical scenarios compared to younger patients. However, there is no clear evidence for a generally reduced radiation tolerance with increasing age. Modern radiation techniques have clearly reduced acute and late side effects, thus extending the boundaries of the possible regarding treatment intensity in elderly or frail patients. Hypofractionated regimens have further decreased the socioeconomic burden of radiation treatments by reducing the overall treatment time. The current review aims at summarizing the existing data for the use of radiation therapy or chemoradiation in elderly patients focusing on the main cancer types. It provides an overview of treatment tolerability and outcomes with current standard radiation therapy regimens, including possible predictive factors in the elderly population. Strategies for patient selection for standard or tailored radiation therapy approaches based on age, performance score or comorbidity, including the use of prediction tests or geriatric assessments, are discussed. Current and future possibilities for improvements of routine care and creation of high-level evidence in elderly patients receiving radiation therapy are highlighted.
(La0.6Sr0.4)0.95Co0.2Fe0.8O3-δ (LSCF) powder has been modified by atomic layer deposition (ALD) with Group IVA based oxides, including zirconia, hafnia, and cobalt doped compositions. Amide zirconium ...and hafnium and amidinate cobalt precursors were used in an ALD process to treat 0.3 mm nominal diameter LSCF powder at 240°C using water as a co-reactant. The effect of the number of ALD cycles and level of Co additions have been examined up to 15% Co. The morphology and physical properties of sintered samples were similar to untreated powders with a modest shift to lower porosity and pore volume, but well within the desired range of microstructural properties. Depending on the recipe, initial polarization of cathodes in symmetrical electrochemical cells varied slightly compared to uncoated powders. Degradation of cathodes made from treated powders was improved compared to cathodes made from untreated powders.
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