Ab initio free energy of vacancy formation and mass-action kinetics in vis-active TiO2

Recent reports have identified bulk defects such as oxygen vacancies as key players in visible-light photoactive TiO2. This would imply greater visible light absorption rates may be possible provided effective defect engineering can be achieved. To further this we have developed methods to simulate vacancy formation in bulk TiO2 using ab initio techniques. Initial results of these methods show an entropic reduction in the free energy of vacancy formation of 2.3 eV over a range of 266 K. The use of this result is illustrated by a 'toy' mass-action kinetics model which offers insight into vacancy concentration, rate constants, and enthalpy of reaction

Turbo-FLASH based arterial spin labeled perfusion MRI at 7 T.

Motivations of arterial spin labeling (ASL) at ultrahigh magnetic fields include prolonged blood T1 and greater signal-to-noise ratio (SNR). However, increased B0 and B1 inhomogeneities and increased specific absorption ratio (SAR) challenge practical ASL implementations. In this study, Turbo-FLASH (Fast Low Angle Shot) based pulsed and pseudo-continuous ASL sequences were performed at 7T, by taking advantage of the relatively low SAR and short TE of Turbo-FLASH that minimizes susceptibility artifacts. Consistent with theoretical predictions, the experimental data showed that Turbo-FLASH based ASL yielded approximately 4 times SNR gain at 7T compared to 3T. High quality perfusion images were obtained with an in-plane spatial resolution of 0.85×1.7 mm(2). A further functional MRI study of motor cortex activation precisely located the primary motor cortex to the precentral gyrus, with the same high spatial resolution. Finally, functional connectivity between left and right motor cortices as well as supplemental motor area were demonstrated using resting state perfusion images. Turbo-FLASH based ASL is a promising approach for perfusion imaging at 7T, which could provide novel approaches to high spatiotemporal resolution fMRI and to investigate the functional connectivity of brain networks at ultrahigh field

Enhanced co-solubilities of Ca and Si in YAG (Y3Al5O12)

General garnet structure (Ia3-d) is a forgiving host and can accommodate cations of varying sizes and valence states. Studies on highly yttrium doped alumina ceramics with Ca and Si contamination indicated that YAG precipitates in the ceramic had a propensity to allow simultaneous incorporation of small amounts of Ca and Si impurities in their structure. In this study, using chemical synthesis techniques it was shown that YAG can accommodate up to approximately 8 cation % Ca+2 and Si+4 (i.e. Ca+2/Y+3 and Si+4/Y+3) if they are incorporated together. Equilibrium conditions are established by calcining samples at 900 C for 2 hours and cooling the samples to room temperature in the furnace. Disappearing-phase method and energy dispersive X-ray spectroscopy (EDS) were used to determine solubility and co-solubility limits. Beyond the solubility limit phase separation occurred and three crystalline yttrium aluminate phases (YAG, YAP (yttrium aluminate perovskite, YAlO3), YAM (yttrium aluminate monoclinic, Y4Al2O9)) were observed. It is believed that the excess Ca and Si above co-solubility limit precipitate out in the form of an x-ray amorphous anorthite-like glass in the system

To be or not to be : Impairment Practices Among Indian Listed Companies

India is converging its practices to be consistent with IFRS, but in the case of goodwill impairment how much consistency is there among Indian companies and auditors, and how much impairment has been disclosed. The paper investigates these questions. Arguably, the issue of how India writes-down goodwill is important as Indian companies and the Indian share market are influential throughout the world. It is a question of recognition, measurement and disclosure. The findings are that different methods of writing down goodwill are recognised implying different methods of measurement. There is even more inconsistency around disclosure as nearly half of the top 50 companies analysed on the Bombay exchange failed to mention any write down of goodwill. Some companies claimed that they were testing for impairment but no case of actual impairment was reported. This, in spite of some compaines reporting declining earnings and share price