Contextual Linear Bandits under Noisy Features: Towards Bayesian Oracles

We study contextual linear bandit problems under uncertainty on features; they are noisy with missing entries. To address the challenges from the noise, we analyze Bayesian oracles given observed noisy features. Our Bayesian analysis finds that the optimal hypothesis can be far from the underlying realizability function, depending on noise characteristics, which is highly non-intuitive and does not occur for classical noiseless setups. This implies that classical approaches cannot guarantee a non-trivial regret bound. We thus propose an algorithm aiming at the Bayesian oracle from observed information under this model, achieving $\tilde{O}(d\sqrt{T})$ regret bound with respect to feature dimension $d$ and time horizon $T$. We demonstrate the proposed algorithm using synthetic and real-world datasets.Comment: 30 page

Modulations of visual and somatosensory perception by action

This thesis aimed to further investigate the effects of movements on modulations of visual and somatosensory perception. The first experiment (Chapter 2) investigated spatial mislocalisation of visual stimuli presented before saccade using a pointing paradigm and found that a predictive remapping of visual space occurred before saccade and the post-saccadic remapping employed spatially as well as temporally accurate memory of pre-saccadic visual stimuli. The second experiment (Chapter 3) examined relevance of saccadic chronostasis to remapping of visual space using a target displacement paradigm and found that it did not serve as a mechanism that fills in a perceptual gap during saccadic suppression. The third (Chapter 4) and fourth (Chapter 5) experiments adopted a target blanking paradigm and found that the pre-saccadic stimuli predictively remapped before saccade were anchored to the location of the pre-saccadic target remapped using a precise efference copy and neither saccade landing sites nor remembered locations of pre-saccadic targets were used in this process. Behavioural (Chapter 6) and fMRI (Chapter 7) studies were conducted to investigate modulations of tactile perception by manual movements and found that the tactile attention induced by the cued index finger facilitated processing of tactile stimuli presented to the responded hand. The somatosensory ROIs mainly showed a bias towards contralateral tactile stimulation in comparison with ipsilateral tactile stimulation. The right primary motor cortex (right M1), the left precuneus (left PreC) and the left middle frontal gyrus (left MFG) showed significant modulations of somatosensory processing by the Moving condition compared to the Non Moving condition. The final chapter included summaries and conclusions of each chapter and proposals for future investigations

Modulations of visual and somatosensory perception by action

This thesis aimed to further investigate the effects of movements on modulations of visual and somatosensory perception. The first experiment (Chapter 2) investigated spatial mislocalisation of visual stimuli presented before saccade using a pointing paradigm and found that a predictive remapping of visual space occurred before saccade and the post-saccadic remapping employed spatially as well as temporally accurate memory of pre-saccadic visual stimuli. The second experiment (Chapter 3) examined relevance of saccadic chronostasis to remapping of visual space using a target displacement paradigm and found that it did not serve as a mechanism that fills in a perceptual gap during saccadic suppression. The third (Chapter 4) and fourth (Chapter 5) experiments adopted a target blanking paradigm and found that the pre-saccadic stimuli predictively remapped before saccade were anchored to the location of the pre-saccadic target remapped using a precise efference copy and neither saccade landing sites nor remembered locations of pre-saccadic targets were used in this process. Behavioural (Chapter 6) and fMRI (Chapter 7) studies were conducted to investigate modulations of tactile perception by manual movements and found that the tactile attention induced by the cued index finger facilitated processing of tactile stimuli presented to the responded hand. The somatosensory ROIs mainly showed a bias towards contralateral tactile stimulation in comparison with ipsilateral tactile stimulation. The right primary motor cortex (right M1), the left precuneus (left PreC) and the left middle frontal gyrus (left MFG) showed significant modulations of somatosensory processing by the Moving condition compared to the Non Moving condition. The final chapter included summaries and conclusions of each chapter and proposals for future investigations

Hypochoeris radicata attenuates LPS-induced inflammation by suppressing P38, ERK, and JNK phosphorylation in Raw 264.7 macrophages

Hypochoeris radicata, an invasive plant species, is a large and growing threat to ecosystem integrity on Jeju Island, a UNESCO World Heritage site. Therefore, research into the utilization of H. radicata is important and urgently required in order to solve this invasive plant problem in Jeju Island. The broader aim of our research is to elucidate the biological activities of H. radicata, which would facilitate the conversion of this invasive species into high value added products. The present study was undertaken to identify the pharmacological effects of H. radicata flower on the production of inflammatory mediators in macrophages. The results indicate that the ethyl acetate fraction of H. radicata extract (HRF-EA) inhibited the production of pro-inflammatory molecules such as NO, iNOS, PGE2, and COX-2, and cytokines such as TNF-α, IL-1β, and IL-6 in LPS-stimulated RAW 264.7 cells. Furthermore, the phosphorylation of MAPKs such as p38, ERK, and JNK was suppressed by HRF-EA in a concentration-dependent manner. In addition, through HPLC and UPLC fingerprinting, luteolins were also identified and quantified as extract constituents. On the basis of these results, we suggest that H. radicata may be considered possible anti-inflammatory candidates for pharmaceutical and/or cosmetic applications

Biosynthesis of phenylpropanoids and their protective effect against heavy metals in nitrogen-fixing black locust (Robinia pseudoacacia)

Purpose: To examine the effect of various heavy metals (HMs) on phenylpropanoid pathway compounds in Robinia pseudoacacia.Methods: A series of pot culture experiments were performed to understand how the metabolic profile of phenylpropanoid compounds were affected by various HMs, such as redox-active HMs (AgNO3 and CuCl2), and non-redox-active HMs (HgCl2). Phenylpropanoid compound level was evaluated by high performance liquid chromatography.Results: The total phenylpropanoid level in leaves increased significantly in all the treated groups when compared to that in the untreated group (p < 0.05). However, a significant effect on the total phenylpropanoid levels was only found for redox-active HMs (p < 0.05), whereas non-redox-active HMs showed less accumulation. Chlorogenic acid and rutin were the two major phenylpropanoid compounds found after the plants were subjected to redox and non-redox-active HMs stress. However, when compared to these two compounds, the levels of catechin hydrate, epicatechin, p-coumaric acid, kaempferol, and quercetin were lower. Caffeic acid level was significantly decreased in both redox and non-redox-active HMs when compared to that in the control (p < 0.05). In addition, trans-cinnamic acid accumulation was altered based on the types and concentration of HMs.Conclusion: Phenylpropanoid metabolic pathway participated in the HM tolerance process for the protection of R. pseudoacacia from oxidative damage caused by HMs, thus allowing the species to grow in highly HMs-contaminated areas. Keywords: Heavy metals, Non-redox-active metals, Phenylpropanoid compounds, Redox-active metals, Robinia pseudoacaci