Estimation of COVID-19 spread curves integrating global data and borrowing information

Currently, novel coronavirus disease 2019 (COVID-19) is a big threat to global health. The rapid spread of the virus has created pandemic, and countries all over the world are struggling with a surge in COVID-19 infected cases. There are no drugs or other therapeutics approved by the US Food and Drug Administration to prevent or treat COVID-19: information on the disease is very limited and scattered even if it exists. This motivates the use of data integration, combining data from diverse sources and eliciting useful information with a unified view of them. In this paper, we propose a Bayesian hierarchical model that integrates global data for real-time prediction of infection trajectory for multiple countries. Because the proposed model takes advantage of borrowing information across multiple countries, it outperforms an existing individual country-based model. As fully Bayesian way has been adopted, the model provides a powerful predictive tool endowed with uncertainty quantification. Additionally, a joint variable selection technique has been integrated into the proposed modeling scheme, which aimed to identify possible country-level risk factors for severe disease due to COVID-19

Bonding Material Coated Clay for Improving Paper Properties

The paper industry utilizes fillers either to reduce the cost or to provide desired functional or end-use properties of paper products. However, there are disadvantages associated with higher filler loadings beyond a certain level, which reduces paper strength. The present study focused on improving the physical property of filled papers. Three methods of structuring fillers were designed; precipitation with starch, complexation with starch and fatty acid, and regeneration with cellulose. Because cellulose and starch have hydroxyl groups on the chemical structure, the hydrogen bonding between fillers and wood fibers is assumed to be occurred by structuring fillers. For starch application, we used two different approaches; salt precipitation and fatty acid complexation. The cooked starch can be precipitated by certain salt solutions such as (NH4)2SO4. Also, the cooked starch can be complexed with fatty acid to produce an insoluble crystalline structure. When starch composites with clay made by both methods were put into the furnish as fillers, dramatic strength improvement was achieved such as 100-200% gains in tensile strength. This is due to the strong bonding between clay fillers and wood fibers, which is determined by Z-directional tensile strength. One of advantages is that using the starch-fatty acid complex has an inherent water repellent property, sizing effect. For cellulose as a bonding material, N-methylmorpholine-N-oxide was used as a solvent to dissolve the cellulose. The advantage of using this method is that we can use the low grade cellulose. The physical properties of the cellulose coated clay handsheets were significantly improved, but optical properties such as brightness and opacity were inferior to the hadnsheets filled with starch-clay composites due to relatively large particle size. In order to model the strength improvement by the composite filler, BDT theory, which is a modified Pages Equation, was used. After calculating the factors such as surface area and specific bond strength, the model matched well with the experimental results. Using this model, the tensile strength improvement could be predicted in terms of the change of bond strength and composite size.Ph.D.Committee Chair: Yulin Deng; Committee Member: Art Ragauskas; Committee Member: Jeff Empie; Committee Member: Jeff Hsieh; Committee Member: Sujit Banerje

Simultaneous VLBI Astrometry of H2O and SiO Masers toward the Semiregular Variable R Crateris

We obtained, for the first time, astrometrically registered maps of the 22.2 GHz H2O and 42.8, 43.1, and 86.2 GHz SiO maser emission toward the semiregular b-type variable (SRb) R Crateris, at three epochs (2015 May 21, and 2016 January 7 and 26) using the Korean Very-long-baseline Interferometry Network. The SiO masers show a ring-like spatial structure, while the H2O maser shows a very asymmetric one-side outflow structure, which is located at the southern part of the ring-like SiO maser feature. We also found that the 86.2 GHz SiO maser spots are distributed in an inner region, compared to those of the 43.1 GHz SiO maser, which is different from all previously known distributions of the 86.2 GHz SiO masers in variable stars. The different distribution of the 86.2 GHz SiO maser seems to be related to the complex dynamics caused by the overtone pulsation mode of the SRb R Crateris. Furthermore, we estimated the position of the central star based on the ring fitting of the SiO masers, which is essential for interpreting the morphology and kinematics of a circumstellar envelope. The estimated stellar coordinate corresponds well to the position measured by Gaia

How Much and When Do We Need Higher-order Information in Hypergraphs? A Case Study on Hyperedge Prediction

Hypergraphs provide a natural way of representing group relations, whose complexity motivates an extensive array of prior work to adopt some form of abstraction and simplification of higher-order interactions. However, the following question has yet to be addressed: How much abstraction of group interactions is sufficient in solving a hypergraph task, and how different such results become across datasets? This question, if properly answered, provides a useful engineering guideline on how to trade off between complexity and accuracy of solving a downstream task. To this end, we propose a method of incrementally representing group interactions using a notion of n-projected graph whose accumulation contains information on up to n-way interactions, and quantify the accuracy of solving a task as n grows for various datasets. As a downstream task, we consider hyperedge prediction, an extension of link prediction, which is a canonical task for evaluating graph models. Through experiments on 15 real-world datasets, we draw the following messages: (a) Diminishing returns: small n is enough to achieve accuracy comparable with near-perfect approximations, (b) Troubleshooter: as the task becomes more challenging, larger n brings more benefit, and (c) Irreducibility: datasets whose pairwise interactions do not tell much about higher-order interactions lose much accuracy when reduced to pairwise abstractions

An Atypical Mitral Valve Prolapse in a Patient With Behçet's Disease

We report the case of a 42-year-old male who was admitted to the hospital with progressive dyspnea. Cardiomegaly and diffuse pulmonary edema were visible on chest X-ray and multiple oral and genital ulcers on physical examination. On admission, echocardiography revealed mitral valve prolapse (MVP) predominantly involving a basal portion of the posterior leaflet, with severe mitral regurgitation. A successful mitral valve replacement with St. Jude #29 was performed, after pre-treatment with prednisolone for 2 weeks. Fifteen months following the operation, the patient expired from severe pulmonary edema and secondary pneumonia. This case demonstrates, for the first time in the literature, an unusual feature of mitral prolapse in the basal portion with severe mitral regurgitation in a patient with Behçet's disease. As suggested by this case, we should consider an atypical type of MVP as a possible inflammatory involvement of the heart in patients with Behçet's disease