Tracing Activity Across the Whole Brain Neural Network with Optogenetic Functional Magnetic Resonance Imaging

Despite the overwhelming need, there has been a relatively large gap in our ability to trace network level activity across the brain. The complex dense wiring of the brain makes it extremely challenging to understand cell-type specific activity and their communication beyond a few synapses. Recent development of the optogenetic functional magnetic resonance imaging (ofMRI) provides a new impetus for the study of brain circuits by enabling causal tracing of activities arising from defined cell types and firing patterns across the whole brain. Brain circuit elements can be selectively triggered based on their genetic identity, cell body location, and/or their axonal projection target with temporal precision while the resulting network response is monitored non-invasively with unprecedented spatial and temporal accuracy. With further studies including technological innovations to bring ofMRI to its full potential, ofMRI is expected to play an important role in our system-level understanding of the brain circuit mechanism

Two Essays on the Average Bid Auction

The dissertation investigates an average bid auction, in which the bid closest to the average wins the auction. In the first study, I investigate the equilibrium bidding strategy in the average bid auction, when cost constitutes a private value without the winner’s curse. More specifically, in addition to the pooling equilibrium established by the existing literature, I characterize a partially pooling equilibrium with three bidders, in which the bid function is constant for small cost realizations and strictly increasing in cost for high cost realizations. Moreover, complete necessary conditions for the existence of partially pooling equilibrium are provided in the case of more than three bidders. Lastly, unlike the first price auction, the average bid auction loses efficiency, and the buyer is likely to pay the more compared to first price auction. The second study investigates the characterization of the equilibrium bid function with three bidders in the average bid auction, considering the possibility of cost overrun and penalty. When the penalty is zero, every bidder bids an identical amount. If the penalty is large, either some bidders bid identically and the rest of bidders follow a strictly increasing bidding strategy, or all bidders place an identical bid. Finally, I compare the average bid auction with the first price reverse auction from the buyer’s point of view. If the penalty is not imposed on insolvent bidders, the buyer who chooses the average bid auction could be better off. On the other hand, if the penalty is large enough to prevent all bidders from defaulting, the average bid auction is always worse. This result partly explains why the average bid auction has been widespread in Italy, and the first price reverse auction has been dominantly used for the procurement in the U.S

Kaon mixing matrix elements from beyond-the-Standard-Model operators in staggered chiral perturbation theory

Models of new physics induce K-Kbar mixing operators having Dirac structures other than the "left-left" form of the Standard Model. We calculate the functional form of the corresponding B-parameters at next-to-leading order in both SU(3) and SU(2) staggered chiral perturbation theory (SChPT). Numerical results for these matrix elements are being generated using improved staggered fermions; our results can be used to extrapolate these matrix elements to the physical light and strange quark masses. The SU(3) SChPT results turn out to be much simpler than that for the Standard Model B_K operator, due to the absence of chiral suppression in the new operators. The SU(2) SChPT result is of similar simplicity to that for B_K. In fact, in the latter case, the chiral logarithms for two of the new B-parameters are identical to those for B_K, while those for the other two new B-parameters are of opposite sign. In addition to providing results for the 2+1 flavor theory in SU(3) SChPT and the 1+1+1 flavor theory in SU(2) SChPT, we present the corresponding continuum partially quenched results, as these are not available in the literature.Comment: 16 pages, 3 figures. Typos corrected--published versio

Comparison of very-large-scale motions of turbulent pipe and boundary layer simulations

A direct numerical simulation of a fully developed turbulent pipe flow was performed to investigate the similarities and differences of very-large-scale motions (VLSMs) to those of turbulent boundary layer (TBL) flows. The Reynolds number was set to ReD = 35 000, and the computational domain was 30 pipe radii in length. Inspection of instantaneous fields, streamwise two-point correlations, and population trends of the momentum regions showed that the streamwise length of the structures in the pipe flow grew continuously beyond the log layer (y/?? 3??), and the maximum length of the VLSMs increased up to ~30??. Such differences between the TBL and pipe flows arose due to the entrainment of large plumes of the intermittent potential flow in the TBL, creating break-down of the streamwise coherence of the structures above the log layer with the strong swirling strength and Reynolds shear stress. The average streamwise length scale of the pipe flow was approximately 1.5-3.0 times larger than that of the TBL through the log and wake regions. The maximum contribution of the structures to the Reynolds shear stress was observed at approximately 6?? in length, whereas that of the TBL was at 1??-2??, indicating a higher contribution of the VLSMs to the Reynolds shear stress in the pipe flow than in the TBL flow.open1