Working memory revived in older adults by synchronizing rhythmic brain circuits

Published in final edited form as: Nat Neurosci. 2019 May ; 22(5): 820–827. doi:10.1038/s41593-019-0371-x.Understanding normal brain aging and developing methods to maintain or improve cognition in older adults are major goals of fundamental and translational neuroscience. Here we show a core feature of cognitive decline—working-memory deficits—emerges from disconnected local and long-range circuits instantiated by theta–gamma phase–amplitude coupling in temporal cortex and theta phase synchronization across frontotemporal cortex. We developed a noninvasive stimulation procedure for modulating long-range theta interactions in adults aged 60–76 years. After 25 min of stimulation, frequency-tuned to individual brain network dynamics, we observed a preferential increase in neural synchronization patterns and the return of sender–receiver relationships of information flow within and between frontotemporal regions. The end result was rapid improvement in working-memory performance that outlasted a 50 min post-stimulation period. The results provide insight into the physiological foundations of age-related cognitive impairment and contribute to groundwork for future non-pharmacological interventions targeting aspects of cognitive decline.Accepted manuscrip

Are Financial Derivates Really Value Enhancing? Australian Evidence

This paper investigates the relationship between the use of financial derivatives and firm value in the Australian setting. Contrary to expectations, we find that the use of derivatives in general, and the use of interest rate derivatives in particular, are negatively related to firm value (as proxied by Tobin’s Q). The existence of this derivative user ‘discount’, combined with strong prior evidence that corporations are primarily motivated by value-enhancing goals, suggests a need for managers to focus serious efforts into explaining their value-driven strategies to the financial market and to do so in a timely manner.

Does the Type of Derivative Instrument Used by Companies Impact Firm Value?

We explore the relationship between the type of derivative instrument used and firm value, in a sample of Australian firms. Specifically, we examine the impact of the corporate use of swaps, futures, forwards and options, and the extent of such usage, on firm value. Our findings suggest that a ‘discount’ is most severely imposed on users of swaps.

Exchange rate exposure, foreign currency derivatives and the introduction of the euro : French evidence

We investigate the impact of the introduction of the Euro on exchange rate exposures for French corporations and examine the corporate use of foreign currency derivatives to hedge exchange rate exposure post-Euro. Our findings indicate that the introduction of the Euro is associated with both a reduction in the number of firms that have significant exchange rate exposure and the absolute size of exposure. Consistent with these reduced exposures, French firms use foreign currency derivatives less intensively. Furthermore, the use of foreign currency derivatives is found to be associated with lower exchange rate exposure but there is insufficient evidence that these instruments are more effective in the post-Euro environment

W-graph ideals

We introduce a concept of a W-graph ideal in a Coxeter group. The main goal of this paper is to describe how to construct a W-graph from a given W-graph ideal. The principal application of this idea is in type A, where it provides an algorithm for the construction of W-graphs for Specht modules.Comment: 25 page

Joint Data compression and Computation offloading in Hierarchical Fog-Cloud Systems

Data compression has the potential to significantly improve the computation offloading performance in hierarchical fog-cloud systems. However, it remains unknown how to optimally determine the compression ratio jointly with the computation offloading decisions and the resource allocation. This joint optimization problem is studied in the current paper where we aim to minimize the maximum weighted energy and service delay cost (WEDC) of all users. First, we consider a scenario where data compression is performed only at the mobile users. We prove that the optimal offloading decisions have a threshold structure. Moreover, a novel three-step approach employing convexification techniques is developed to optimize the compression ratios and the resource allocation. Then, we address the more general design where data compression is performed at both the mobile users and the fog server. We propose three efficient algorithms to overcome the strong coupling between the offloading decisions and resource allocation. We show that the proposed optimal algorithm for data compression at only the mobile users can reduce the WEDC by a few hundred percent compared to computation offloading strategies that do not leverage data compression or use sub-optimal optimization approaches. Besides, the proposed algorithms for additional data compression at the fog server can further reduce the WEDC