Graduate Recital: Chieh-Chun Chen, Piano

Kemp Recital Hall April 20, 2019 Saturday Morning 11:30 a.m

Identification of Novel (\u3cem\u3eR\u3c/em\u3eNAi \u3cem\u3eDe\u3c/em\u3eficient) Genes in \u3cem\u3eC. elegans\u3c/em\u3e: A Dissertation

RNA interference or RNAi was first discovered as an experimental approach that induces potent sequence-specific gene silencing. Remarkably, subsequent studies on dissecting the molecular mechanism of the RNAi pathway reveal that RNAi is conserved in most eukaryotes. In addition, genes and mechanisms related to RNAi are employed to elicit the regulation of endogenous gene expression that controls a variety of important biological processes. To investigate the mechanism of RNAi in the nematode C. elegans, we performed genetic screens in search of RNAi deficient mutants (rde). Here I report the summary of the genetic screens in search of rde mutants as well as the identification of two novel genes required for the RNAi pathway, rde-3 and rde-8. In addition, we demonstrate that some of the rde genes, when mutated, render the animals developmentally defective, suggesting that these rde genes also function in developmental gene regulation. This work presents novel insights on the components of the RNAi pathway and the requirement of these components in the regulation of endogenous gene expression

Monotherapy of acetylsalicylic acid or warfarin for prevention of ischemic stroke in low-risk atrial fibrillation: A Easter Asian population-based study

Background: This study aimed to investigate the effectiveness of monotherapy acetylsalicylic acid(ASA) and warfarin for stroke prevention in low-risk atrial fibrillation (AF) by using a population--based cohort study in Taiwan.Methods: A newly diagnosed low-risk AF patient cohort were identified by using National HealthInsurance Research Database (NHIRD) in Taiwan in 2008. The study cohort was observed witha follow-up of 2 years to examine the onset of ischemic stroke (IS) (to 2010). The longitudinal data wereanalyzed by using generalized estimation equations (GEE).Results: A total of 8,065 newly-diagnosed low-risk AF patients were identified in 2008. 7.4% wereprescribed with ASA and 4.6% were prescribed with warfarin. The GEE results showed that low-riskAF patients with hypertension who received warfarin were associated with a statistically significant58.4% reduction of IS risk (OR = 0.416, p = 0.024, 95% CI 0.194–0.891). Additionally, low-risk AFpatients with hyperlipidemia who received warfarin were associated with a 69.3% reduction of IS risk(OR = 0.307, p = 0.044, 95% CI 0.097–0.969).Conclusions: Warfarin is suggested to be prescribed in preventing IS for low-stroke-risk AF patientswith hypertension and hyperlipidemia

Selection of thermodynamic models for combinatorial control of multiple transcription factors in early differentiation of embryonic stem cells

<p>Abstract</p> <p>Background</p> <p>Transcription factors (TFs) have multiple combinatorial forms to regulate the transcription of a target gene. For example, one TF can help another TF to stabilize onto regulatory DNA sequence and the other TF may attract RNA polymerase (RNAP) to start transcription; alternatively, two TFs may both interact with both the DNA sequence and the RNAP. The different forms of TF-TF interaction have different effects on the probability of RNAP's binding onto the promoter sequence and therefore confer different transcriptional efficiencies.</p> <p>Results</p> <p>We have developed an analytical method to identify the thermodynamic model that best describes the form of TF-TF interaction among a set of TF interactions for every target gene. In this method, time-course microarray data are used to estimate the steady state concentration of the transcript of a target gene, as well as the relative changes of the active concentration for each TF. These estimated concentrations and changes of concentrations are fed into an inference scheme to identify the most compatible thermodynamic model. Such a model represents a particular way of combinatorial control by multiple TFs on a target gene.</p> <p>Conclusions</p> <p>Applying this approach to a time-course microarray dataset of embryonic stem cells, we have inferred five interaction patterns among three regulators, Oct4, Sox2 and Nanog, on ten target genes.</p

Two dimensional shape measurement via video signal processing

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1978.Includes bibliographical references.by Chun-Chieh Chen.M.S

Interactions Between Reinforcement Corrosion and Chloride Ion Diffusion in Mortar

This study explored the diffusion of the chloride ions influenced by the reinforcement corrosion in the mortar. It is believed that, during the corroding process, a small current is generated at the surface of the reinforcement. Such current is supposed to influence the diffusion of the chloride ions, but the relationship between both was not well studied in the literature. In this study, the corroded reinforcements were prepared by applied currents. Reinforced mortar specimens with w/c of 0.6 were then prepared and cured by either salt or fresh water. Results showed that the chloride ion distribution was likely associated with the reinforcement corrosion. During the early hydration, the chloride ions were attracted by the reinforcement corrosion in the specimens prepared with fresh water and cured in salt water. The concentration of the chloride ions near the surface of the reinforcement was increased with the increases of the charging time during the preparation for the corroded reinforcement. On the contrary, the chloride ions were likely bound in those specimens prepared with salt water and cured by saturated lime water. The concentration of the chloride ions near the surface of the reinforcement was higher than those near the outer surface. However, such influencing effects were not clear in the long term, possibly due to the hydration. The results of this study show that the reinforcement corrosion have influences on the diffusion of the chloride ions and such effect should be considered during the refinement of the traditional chloride ion diffusion models

Accelerated Policy Gradient: On the Nesterov Momentum for Reinforcement Learning

Policy gradient methods have recently been shown to enjoy global convergence at a $\Theta(1/t)$ rate in the non-regularized tabular softmax setting. Accordingly, one important research question is whether this convergence rate can be further improved, with only first-order updates. In this paper, we answer the above question from the perspective of momentum by adapting the celebrated Nesterov's accelerated gradient (NAG) method to reinforcement learning (RL), termed \textit{Accelerated Policy Gradient} (APG). To demonstrate the potential of APG in achieving faster global convergence, we formally show that with the true gradient, APG with softmax policy parametrization converges to an optimal policy at a $\tilde{O}(1/t^2)$ rate. To the best of our knowledge, this is the first characterization of the global convergence rate of NAG in the context of RL. Notably, our analysis relies on one interesting finding: Regardless of the initialization, APG could end up reaching a locally nearly-concave regime, where APG could benefit significantly from the momentum, within finite iterations. By means of numerical validation, we confirm that APG exhibits $\tilde{O}(1/t^2)$ rate as well as show that APG could significantly improve the convergence behavior over the standard policy gradient.Comment: 51 pages, 8 figure