The Role of Stellar Feedback in Galaxy Evolution

Aiming at understanding the role of stellar feedback in galaxy evolution, I present a study of the hot interstellar medium in several representative galaxies, based primarily on X-ray observations as well as theoretical modelling. I find that, in the massive disk galaxies NGC2613 and M104, the observed amount of hot gas is much less than that predicted by current galaxy formation models. Such a discrepancy suggests a lack of appropriate treatments of stellar/AGN feedback in these models. I also find that stellar feedback, primarily in the form of mass loss from evolved stars and energy released from supernovae, and presumably consumed by the hot gas, is largely absent from the inner regions of M104, a galaxy of a substantial content of evolved stars but little current star formation. A natural understanding of this phenomenon is that the hot gas is in the form of a galactic-scale outflow, by which the bulk of the stellar feedback is transported to the outer regions and perhaps into the intergalactic space. A comparison between the observed sub-galactic gas structures and model predictions indicate that this outflow is probably subsonic rather than being a classical supersonic galactic wind. Such outflows are likely prevalent in most early-type galaxies of intermediate masses in the present-day universe and thus play a crucial role in the evolution of such galaxies. For the first time I identify the presence of diffuse hot gas in and around the bulge of the Andromeda Galaxy (M31), our well-known neighbor. Both the morphology and energetics of the hot gas suggest that it is also in the form of a large-scale outflow. Assisted with multiwavelength observations toward the circumnuclear regions of M31, I further reveal the relation between the hot gas and other cooler phases of the interstellar medium. I suggest that thermal evaporation, mostly likely energized by Type Ia supernovae, acts to continuously turn cold gas into hot, a process that naturally leads to the inactivity of the central supermassive blackhole as well as the launch of the hot gas outflow. Such a mechanism plays an important role in regulating the multi-phase interstellar medium in the circumnuclear environment and transporting stellar feedback to the outer galactic regions

Potencies and selectivities of inhibitors of acetylcholinesterase and its molecular forms in normal and Alzheimer's disease brain

Eight inhibitors of acetylcholinesterase (AChE), tacrine, bis-tacrine, donepezil, rivastigmine, galantamine, heptyl-physostigmine, TAK-147 and metrifonate, were compared with regard to their effects on AChE and butyrylcholinesterase (BuChE) in normal human brain cortex. Additionally, the IC50 values of different molecular forms of AChE (monomeric, G1, and tetrameric, G4) were determined in the cerebral cortex in both normal and Alzheimer’s human brains. The most selective AChE inhibitors, in decreasing sequence, were in order: TAK-147, donepezil and galantamine. For BuChE, the most specific was rivastigmine. However, none of these inhibitors was absolutely specific for AChE or BuChE. Among these inhibitors, tacrine, bis-tacrine, TAK-147, metrifonate and galantamine inhibited both the G1 and G4 AChE forms equally well. Interestingly, the AChE molecular forms in Alzheimer samples were more sensitive to some of the inhibitors as compared with the normal samples. Only one inhibitor, rivastigmine, displayed preferential inhibition for the G1 form of AChE. We conclude that a molecular form-specific inhibitor may have therapeutic applications in inhibiting the G1 form, which is relatively unchanged in Alzheimer’s brain