Chemically Engineered 3D Graphene Nanostructures

Chemical EngineeringRecently, 3D graphene nanostructures have attracted considerable attentions for a variety of applications in sensors, separations, lithium-ion batteries, and supercapacitors because of their prominent properties such as high surface area, high electrical conductivity, and thermal/mechanical stability. Herein, we demonstrate various types of 3D graphene nanostructures via chemical modification of graphene oxide and their self-assembly behaviors in different solvent conditions. In particular, porous graphene nanostructures are fabricated through the control of electrostatic repulsions between chemically modified graphene sheets. Chemically reduced graphene oxide sheets are well-dispersed owing to the electrostatic repulsion at high pH condition, while agglomerating each other at low pH condition. Noticeably, we fabricate different graphene morphologies such as dendrite-like structure and wire-like structure by controlling the pH condition. In addition, different morphology of graphene nanostructures such as crumpled and scrolled geometries is demonstrated via control of pH condition and graphene reduction time. These various type of graphene nanostructures could be used for variety of applications as mentioned above.ope

Simultaneous determination of methylcarbamate and ethylcarbamate in fermented foods and beverages by derivatization and GC-MS analysis

BACKGROUND: Methylcarbamate (MC) and ethylcarbamate (EC) are toxic compounds that commonly exist in fermented food and beverages. In order to estimate the risk for their exposure, a sensitive simultaneous analytical method is required RESULTS: A simultaneous determination of MC and EC was described based on derivatization with 9-xanthydrol and consecutive detection using gas chromatography–mass spectrometry. The derivatization of MC and EC was performed directly in food or beverages and the reaction conditions were established through changing various parameters. The detection and the quantification limits were 0.01-0.03 μg/kg and 0.03-0.1 μg/kg, respectively, and the interday relative standard deviation was less than 12% at concentrations of 2.0 and 50 μg/kg. MC and EC were measured from 0.4 μg/kg to 85.8 μg/kg in sixteen Korean fermented foods and eleven beverages. CONCLUSION: A simple, sensitive method to detect MC and EC in several solid foods and liquid foods was developed based on derivatization with 9-xanthydrol for 10 min at an ambient temperature. The method may useful for routine analysis of MC and EC in numerous food samples

Engineering of hybrid materials for self-powered flexible sensors

Department of Energy Engineering (Energy Engineering)Along with the 4th industrial revolution, the great advance in wearable electronics has led a new paradigm in our life. Especially, wearable sensor technology has received great attention as promising candidates to improve the quality of life by realizing the ???Internet of Things??? which can be utilized in daily healthcare, intelligent control, daily activity monitoring, and human-machine interface systems. The ideal wearable devices require several characteristics providing light weight, flexible, unobtrusive, autonomously powered for the convenience of user and sustainable uses. Although various emerging technologies have been suggested to meet these requirements, there are still challenges for highly flexible and unobtrusive forms, multifunctionality, and sustainable uses, which are directly related to widespread practical applications. In response to these requirements, several approaches to explore functional materials and to design the effective structures for advanced sensor performances with sustainable uses, high sensitivity, and multifunctionality. For sustainable uses, self-powered sensing system can be developed by triboelectric/piezoelectric/pyroelectric effect, which can rule out any problems with power sources. For wearable and flexible form factors, textile and extremely thin films, which are mountable and attachable on the human body, are used instead of conventional obtrusive devices, improving the wearing sensing of devices. Moreover, the selection of multifunctional materials and modification of material characteristics can realize multifunctionality which can respond to different stimuli (pressure and temperature) simultaneously. Furthermore, soft/hard and organic/inorganic hybrid materials can be used for effective design of high performance wearable sensor by distribution control in dissimilar materials, which is attributed to effectively localized strain and large contrast of dielectric properties. Therefore, self-powered wearable sensors can be developed with functional materials, unique design and novel approach for characteristic modification, which can provide a promising platform to realize ideal wearable sensors for future applications such as daily healthcare, intelligent control, daily activity monitoring, and human-machine interface systems. In this thesis, we suggest the strategy for advanced sustainable wearable sensors with better wearing sensation, multimodality, and enhanced sensory functions through structure design and modification of material characteristics. Firstly, we briefly summarize the fundamental working principles, the latest research trends, and potential applications in Chapter 1. In Chapter 2, we demonstrate as-spun P(VDF) fiber-based self-powered textile sensors with high sensitivity, mechanical stability, and washing durability. In Chapter 3, we introduce multimodal wearable sensors without signal interference based on triboelectric and pyroelectric effect, which is attributed to controllable polarity of P(VDF-TrFE) via ferroelectric polarization. In Chapter 4, we suggest a novel method for high performance of triboelectric sensors based on alternating P(VDF-TrFE)/BaTiO3 multilayer nanocomposites, which is attributed to the efficient stress concentration and large contrast of dielectric properties. Lastly, we summarize this thesis with future prospects in Chapter 5.clos

Ciliated muconodular papillary tumor of the lung: The risk of false-positive diagnosis in frozen section

AbstractCiliated muconodular papillary tumor (CMPT) is newly-defined low-grade malignant tumor, characterized as papillary tumor consisting of ciliated columnar, goblet, and basal cells. We present one case of pulmonary peripheral neoplasm misdiagnosed as mucinous adenocarcinoma. Pathologic findings showed, centrally, cystic papillary growth consisting of ciliated columnar, goblet, and basal cells, and peripherally, some tumor cells spread along the adjacent alveolar walls, in a lepidic fashion, and floating in pool of mucin. Tumor cells had bland nuclei, and no mitotic activity was observed. This had been initially misdiagnosed as mucinous adenocarcinoma in frozen section. We reviewed previous articles as well as permanent and frozen slides. In conclusion, in order to reduce the possibility of false positives, it is important to be aware that CMPT is a rare form of peripheral mucin-producing tumor with characteristic histologic findings

Piercing of the Corporate Veil in Korea: Case Commentary

The purpose of this Commentary is to critically appraise the jurisprudence of Korea on the doctrine of corporate veil piercing with a special emphasis on the Korean Supreme Courts decision in 2004Da26119. In 2004Da26119, the Supreme Court of Korea delineated the criteria for disregarding the corporate entity under Korean corporate law, particularly in the parentsubsidiary context. As part of its purported aim, the Commentary will analyze the constitutive elements of veil piercing as understood by Korean courts and attempt to survey the evolution of jurisprudence on veil piercing leading up to 2004Da26119. The Commentary will argue that a showing of parental motive and/or purpose, which the Supreme Court required in 2004Da26119 as part of prima facie proof for veil piercing, may well dampen the overall efficacy of veil piercing in Korea, due to the evidentiary hardship it will pose in practice