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School of Energy and Chemical Engineering (Chemical Engineering)Rechargeable batteries have attracted a lot of attention owing to their wide applicability, such as portable/consumer electronics, electric vehicles, and grid-scale applications. Over the past two decades, significant advances have been made in battery technologies. However, advancement in various technologies necessitates batteries that are more efficient because the current levels of performance are inadequate. This has encouraged researchers to design and discover new battery materials to meet future demands. In this context, a fundamental understanding of the polymorphism and charge storage mechanism of battery materials can provide design principles and promote the discovery of novel materials. To achieve this, the multiscale simulation method has been used to study physicochemical phenomena or properties of different time and space scales. In this dissertation, we introduced theoretical studies on polymorphism and charge storage mechanism of battery materials. Specifically, we discussed three newly designed electrode materials, a conventional binder material, and a separator material. In Chapter 1, we provide an overview and the challenges of rechargeable batteries. We then present a general background of the charge storage mechanism and polymorphism phenomenon and their importance in the study and design of rechargeable battery materials. Finally, we describe the modern multiscale computational techniques for rechargeable battery materials such as the density functional theory calculation, density functional tight binding calculation, molecular dynamics simulation, and Monte Carlo simulation. In Chapter 2, we present a theoretical study on the polymorphism and charge storage mechanism of contorted hexabenzocoronene (c-HBC) as a new type of anode material for Li-ion batteries. In this study, the packing polymorphism was demonstrated by disclosing the crystal structure of polymorph ??????, which is the metastable R-3 crystal phase, using computational polymorph prediction. It was also revealed that polymorph ??? was not a polymorph of c-HBCinstead, it is the P31 (or P32) crystal phase of c-HBC with Pd atoms. Moreover, our investigation on the lithium storage mechanism showed that the c-HBC anode exhibited a single-stage Li-ion insertion behavior without voltage penalty, which was attributed to the 3D-ordered empty pores originating from the contorted structure of c-HBC. In Chapter 3, we present a theoretical study on the polymorphism and charge storage mechanism of fluorinated-contorted hexabenzocoronene (F-cHBC) as a potential electrochemical organic electrode material. Based on Monte Carlo computational study, it was revealed that the crystal structure of polymorph I was the energetically stable P21/c crystal phase. Furthermore, theoretical investigation on lithium/sodium storage mechanism showed that Li- and Na-ions could be stored in two distinct sites surrounded by electronegative fluorine atoms and a negatively charged bent edge aromatic ring. In Chapter 4, we present a theoretical study on the polymorphism and charge storage mechanism of the redox-active covalent triazine framework (rCTF) as a promising organic anode material for Li-ion batteries. The potential energy analysis suggested that the rCTF can potentially exhibit packing polymorphism for two energy-minimum packing modes, namely, AB and slipped-parallel packing modes. The most stable was the slipped-packing mode. Furthermore, we revealed that the rCTF provided a theoretical capacity of up to 1200 mAh g???1 using quinone, triazine, and benzene rings as the redox-active sites. The structural deformation of rCTF during activation allowed more redox-active sites to be accessible, especially the benzene rings. In Chapter 5, we present a theoretical study on poly(vinylidene fluoride) (PVDF), which is a conventional polymeric binder material for rechargeable batteries. Although it is rarely considered in the battery field, PVDF is a semicrystalline polymer with various polymorphs that have different polarization characteristics. In this study, the effect of the crystal phases of PVDF, specifically ??- and ??-PVDFs, on battery performance was investigated. We showed that compared to negligible polarization of the paraelectric ??-PVDF, the strong polarization generated by the ferroelectric ??-PVDF can effectively transport electrons and Li-ions, leading to reduction in the charge transfer resistance and mitigation of the concentration polarization in the Li-ion battery system. In Chapter 6, we present a theoretical study on polymorphism of chitin separator material and its interaction with electrolyte. As a semicrystalline biopolymer, chitin can exist in two polymorphs, ??- and ??-phase. These crystals have different molecular conformation and arrangement, resulting in different polarization characteristics. Based on density functional theory calculations and molecular dynamics simulations, we revealed that both polymorphs of chitin had excellent electrolyte-uptaking property and high physicochemical affinity to Li-ions with binding reversibility.ope

Multi-Color Luminescence Transition of Upconversion Nanocrystals via Crystal Phase Control with SiO2 for High Temperature Thermal Labels

Upconversion nanocrystals (UCNs)-embedded microarchitectures with luminescence color transition capability and enhanced luminescence intensity under extreme conditions are suitable for developing a robust labeling system in a high-temperature thermal industrial process. However, most UCNs based labeling systems are limited by the loss of luminescence owing to the destruction of the crystalline phase or by a predetermined luminescence color without color transition capability. Herein, an unusual crystal phase transition of UCNs to a hexagonal apatite phase in the presence of SiO2 nanoparticles is reported with the enhancements of 130-fold green luminescence and 52-fold luminance as compared to that of the SiO2-free counterpart. By rationally combining this strategy with an additive color mixing method using a mask-less flow lithography technique, single to multiple luminescence color transition, scalable labeling systems with hidden letters-, and multi-luminescence colored microparticles are demonstrated for a UCNs luminescence color change-based high temperature labeling system

Cyclooxygenase-2 and p53 Expression as Prognostic Indicators in Conventional Renal Cell Carcinoma

The aim of this study was to investigate the relationship of cyclooxygenase (COX)-2 and p53 expression with prognosis in patients with conventional renal cell carcinoma (RCC). Formalin-fixed, paraffin-embedded tissue sections of conventional RCC from 92 patients, who had undergone radical nephrectomy, were examined for COX-2 and p53 expression by immunohistochemistry and compared with clinicopathological variables. The COX-2 expression significantly correlated only with tumor size (p=0.049), whereas the p53 expression profoundly correlated with the TNM stage (p=0.024), M stage (p=0.001), and metastasis (synchronous or metachronous; p=0.004). The COX-2 overexpression did not significantly associate with p53 positivity (p=0.821). The survival rate of patients correlated with the p53 expression (p<0.0001) but not with the COX-2 expression (p=0.7506). Multivariate analyses indicated that tumor size, M stage, and p53 expression were independent prognostic factors for cancer-specific survival. The COX-2 expression was not an independent factor. These results show that the increased expression of p53 was associated with metastasis and a worse prognosis in conventional RCC, which suggests that p53 might have played an important role in the progression of conventional RCC. The increased expression of COX-2 was associated only with tumor size, but may not be an important prognostic factor in conventional RCC. No association was observed between COX-2 overexpression and p53 positivity in conventional RCC

Developments and Further Applications of Ephemeral Data Derived Potentials

Machine-learned interatomic potentials are fast becoming an indispensable tool in computational materials science. One approach is the ephemeral data-derived potential (EDDP), which was designed to accelerate atomistic structure prediction. The EDDP is simple and cost-efficient. It relies on training data generated in small unit cells and is fit using a lightweight neural network, leading to smooth interactions which exhibit the robust transferability essential for structure prediction. Here, we present a variety of applications of EDDPs, enabled by recent developments of the open-source EDDP software. New features include interfaces to phonon and molecular dynamics codes, as well as deployment of the ensemble deviation for estimating the confidence in EDDP predictions. Through case studies ranging from elemental carbon and lead to the binary scandium hydride and the ternary zinc cyanide, we demonstrate that EDDPs can be trained to cover wide ranges of pressures and stoichiometries, and used to evaluate phonons, phase diagrams, superionicity, and thermal expansion. These developments complement continued success in accelerated structure prediction.Comment: 22 pages, 15 figure

New record of Chromis weberi (Actinopterygii: Ovalentaria: Pomacentridae) from Jeju Island, southern Korea

Discovering tropical marine species outside of their distribution limits is important for evaluating the impact of climate change on marine ecosystems. One specimen (31.6 mm standard length) of a tropical fish, Chromis weberi Fowler et Bean, 1928, representing the family Pomacentridae, was first recorded from Jeju Island, Korea, on 8 December 2021. It was characterized by black posterior margins of the preopercle and opercle and black upper and lower lobes of the caudal fin. A specimen of this species collected from Munseom was distinguished from Chromis xanthura (Bleeker, 1854) based on distinct differences in the tips of the upper and lower caudal fin lobes, which are not black in C. xanthura. In addition, C. weberi was easily distinguished from the other four species in the genus Chromis, by the mitochondrial DNA cytochrome c oxidase subunit I gene sequence (345 bp), with genetic distances ranging from 0.130 to 0.252. This study documents the first record of C. weberi in temperate Korean waters, implying a poleward range expansion for this species. The Korean name ‘geom-eun-jeom-ggo-ri-ja-ri-dom’ has been proposed for C. weberi

A highly efficient wide-band-gap host material for blue electrophosphorescent light-emitting devices

We report on an efficient wide-band-gap host material for blue electrophosphorescence devices, namely, 1,2-trans-di-9-carbazolylcyclobutane (DCz). Photophysical studies show that lower-energy excimer formation between the carbazole units can be efficiently suppressed in a DCz film, thus maintaining its high triplet-state energy and inducing an exothermic energy transfer from DCz to iridium(III)bis[(4,6-difluorophenyl)-pyridinato-N,C2]picolinate (FIrpic). Electrophosphorescent devices comprising a FIrpic:DCz emitting layer exhibit a superior performance with a maximum external quantum efficiency of 9.8%, a maximum luminance efficiency of 21.5 cd/A, and a maximum power efficiency of 15.0 lm/W at 0.01 mA/cm2.This work was partly supported by the Korea Science and Engineering Foundation (KOSEF) through the National Research Laboratory Program funded by the Ministry of Science and Technology (No. 2006-03246), and by Dongwoo FineChem Co

Effects of Murine Dermal Cells on the Regulation of Hair Growth Is Dependent on the Cell Number and Post-Natal Age of Newborn Mice

Dermal cells from neonatal mice can initiate the formation of hair follicles (HFs) when combined with adult mouse epidermal cells and transplanted subcutaneously into athymic mice. In the present study, the effects of dermal cells on HF formation were tested in terms of total cell number and the time course of cell harvest. Results demonstrated that the number of dermal cells is critical to the formation of HF. Furthermore, hair forming ability is rapidly decreasing as the neonatal mice age. To examine potential differences in gene expression, cDNA array was performed. Results demonstrate that numerous molecules which are directly involved in receptor and signaling correlated with decreased hair inductivity in early time points after delivery. It is reported that bone morphogenic protein (BMP)-6 and Wnt3a treatment increased hair inductivity of dermal papilla cells. But in our study, no changes were observed in the expression levels of BMP-6 and Wnt3a. However, several Wnt related genes demonstrate increased or decreased expression levels. Thus, our results suggest that co-ordinated regulation of these molecules will be important in hair neogenesis within our model system

A Case of Adult Polyglucosan Body Disease

Adult polyglucosan body disease (APBD) is a rare neurological disease, characterized by adult onset (fifth to seventh decades), progressive sensorimotor or pure motor peripheral neuropathy, upper motor neuron symptoms, neurogenic bladder, and cognitive impairment. APBD is confirmed by a sural nerve biopsy that shows the widespread presence of polyglucosan bodies in the nerve. We report a 70 year old male patient who exhibited progressive weakness in all extremities and dementia. His electrodiagnostic studies showed sensorimotor polyneuropathy and muscle pathology that consisted of polyglucosan bodies located in small peripheral nerves. This is the first case of APBD reported in Korea

Trans-Differentiation of Neural Stem Cells: A Therapeutic Mechanism Against the Radiation Induced Brain Damage

Radiation therapy is an indispensable therapeutic modality for various brain diseases. Though endogenous neural stem cells (NSCs) would provide regenerative potential, many patients nevertheless suffer from radiation-induced brain damage. Accordingly, we tested beneficial effects of exogenous NSC supplementation using in vivo mouse models that received whole brain irradiation. Systemic supplementation of primarily cultured mouse fetal NSCs inhibited radiation-induced brain atrophy and thereby preserved brain functions such as short-term memory. Transplanted NSCs migrated to the irradiated brain and differentiated into neurons, astrocytes, or oligodendrocytes. In addition, neurotrophic factors such as NGF were significantly increased in the brain by NSCs, indicating that both paracrine and replacement effects could be the therapeutic mechanisms of NSCs. Interestingly, NSCs also differentiated into brain endothelial cells, which was accompanied by the restoration the cerebral blood flow that was reduced from the irradiation. Inhibition of the VEGF signaling reduced the migration and trans-differentiation of NSCs. Therefore, trans-differentiation of NSCs into brain endothelial cells by the VEGF signaling and the consequential restoration of the cerebral blood flow would also be one of the therapeutic mechanisms of NSCs. In summary, our data demonstrate that exogenous NSC supplementation could prevent radiation-induced functional loss of the brain. Therefore, successful combination of brain radiation therapy and NSC supplementation would provide a highly promising therapeutic option for patients with various brain diseases