What image features guide lightness perception?

Lightness constancy is the ability to perceive black and white surface colors under a wide range of lighting conditions. This fundamental visual ability is not well understood, and current theories differ greatly on what image features are important for lightness perception. Here we measured classification images for human observers and four models of lightness perception to determine which image regions influenced lightness judgments. The models were a high-pass-filter model, an oriented difference-of-Gaussians model, an anchoring model, and an atmospheric-link-function model. Human and model observers viewed three variants of the argyle illusion (Adelson, 1993) and judged which of two test patches appeared lighter. Classification images showed that human lightness judgments were based on local, anisotropic stimulus regions that were bounded by regions of uniform lighting. The atmospheric-link-function and anchoring models predicted the lightness illusion perceived by human observers, but the high-pass-filter and oriented-difference-of-Gaussians models did not. Furthermore, all four models produced classification images that were qualitatively different from those of human observers, meaning that the model lightness judgments were guided by different image regions than human lightness judgments. These experiments provide a new test of models of lightness perception, and show that human observers' lightness computations can be highly local, as in low-level models, and nevertheless depend strongly on lighting boundaries, as suggested by midlevel models.York University Librarie

Heterogeneous Investors and their Changing Demand and Supply Schedules for Individual Common Stocks

Using 550 million limit orders submitted in the Korea Stock Exchange, we estimate demand and supply elasticities of heterogeneous investor types and their changes around the Asian financial crisis. We find that domestic individuals have substantially more inelastic demand and supply curves than domestic institutions and foreign investors. The crisis permanently reduced price elasticities of domestic individuals by 50% but had no effect on those of foreign investors. Institutional changes restricting margin purchases, implemented after the crisis, seem particularly important in explaining the dramatic drop. Information heterogeneity, availability of close substitutes and arbitrage risk also explain time-series variations in elasticities.

Comparing the efficacy and safety of potential clinical vaccines for the Ebola virus

The Ebola virus disease is one of the most dangerous diseases to develop into a major health concern in the modern era, largely because of the ZEBOV outbreak that has devastated West Africa from 2014 to 2016. The outbreak has compelled many countries and organizations to prioritize finding a vaccine for Ebola, which is key to preventing a similar outbreak on a global scale. As a result, studies on Ebola vaccines have increased in frequency since 2014. This thesis will focus on three vaccine candidates that could potentially be developed into a future vaccine for Ebola: chAd3, rVSV, and rAd5. Each of the vaccines has been the focus of several studies on both animals and humans, which have provided information and understanding of the vaccines’ characteristics in terms of reactogenicity and immunogenicity. All of the vaccines demonstrate safety and immunogenicity profiles that offer promise for the vaccines as future candidates, which at first makes them seem very similar to each other. However, they each differ substantially in their flaws and ability to generate an immunogenic response. More specifically, the chAd3 vaccine requires a boost of MVA to reach its full potential, the rVSV vaccine has expressed a higher level of reactogenicity and adverse effects than the other two vaccines, and the rAd5 vaccine’s efficacy is weakened by the presence of pre-existing immunity against Ad5 in the human population

Crossmodal Attentive Skill Learner

This paper presents the Crossmodal Attentive Skill Learner (CASL), integrated with the recently-introduced Asynchronous Advantage Option-Critic (A2OC) architecture [Harb et al., 2017] to enable hierarchical reinforcement learning across multiple sensory inputs. We provide concrete examples where the approach not only improves performance in a single task, but accelerates transfer to new tasks. We demonstrate the attention mechanism anticipates and identifies useful latent features, while filtering irrelevant sensor modalities during execution. We modify the Arcade Learning Environment [Bellemare et al., 2013] to support audio queries, and conduct evaluations of crossmodal learning in the Atari 2600 game Amidar. Finally, building on the recent work of Babaeizadeh et al. [2017], we open-source a fast hybrid CPU-GPU implementation of CASL.Comment: International Conference on Autonomous Agents and Multiagent Systems (AAMAS) 2018, NIPS 2017 Deep Reinforcement Learning Symposiu

Heterogeneous Investors and their Changing Demand and Supply Schedules for Individual Common Stocks

Using 550 million limit orders submitted in the Korea Stock Exchange, we estimate demand and supply elasticities of heterogeneous investor types and their changes around the Asian financial crisis. We find that domestic individuals have substantially more inelastic demand and supply curves than domestic institutions and foreign investors. The crisis permanently reduced price elasticities of domestic individuals by 50% but had no effect on those of foreign investors. Institutional changes restricting margin purchases, implemented after the crisis, seem particularly important in explaining the dramatic drop. Information heterogeneity, availability of close substitutes and arbitrage risk also explain time-series variations in elasticities.

Local Out-Tournaments with Upset Tournament Strong Components I: Full and Equal {0,1}-Matrix Ranks

A digraph D is a local out-tournament if the outset of every vertex is a tournament. Here, we use local out-tournaments, whose strong components are upset tournaments, to explore the corresponding ranks of the adjacency matrices. Of specific interest is the out-tournament whose adjacency matrix has boolean, nonnegative integer, term, and real rank all equal to the number of vertices, n. Corresponding results for biclique covers and partitions of the digraph are provided