Preparation and Applications of Multidimensional Graphene Oxide-Based Materials

Department of Energy EngineeringGraphene is well known to have excellent electronic, mechanical and thermal properties, but it is still challenges to apply its intrinsic properties to real applications. One possible route to utilizing these properties for applications would be to incorporate graphene sheets in a composite material. Many approaches have been studied for the fabrication of graphene and graphene oxide (GO)-based composite materials with polymer, carbon nanomaterials and metal nanoparticles. This thesis is aimed at discussing the fabrication methods and applications of GO-based high performance composites. There have been many studies on GO-based composite materials, among which PVA has been considered as the most suitable polymer for GO-based composite applications. For various practical applications, it is very important to improve the mechanical properties of PVA. A large amount of oxygen-containing functional groups inserted onto the GO surface can form strong hydrogen bonds with the hydroxyl group of PVA. In this thesis, we have successfully fabricated PVA-GO composite films and fibers with improved mechanical strength by forming an additional adhesion properties from poly(dopamine) layers between the GO and PVA. The fabricated PVA/GO composite films and fibers resulted in increases in tensile modulus, ultimate tensile strength, and strain-to-failure. A combination of hydrogen bonding, strong adhesion of poly(dopamine) at the interface of PVA and GO sheets resulted in increases in tensile modulus, ultimate tensile strength, and strain-to-failure. In addition, the electrical conductivity of PVA/GO composite films and fibers can be restored owing to the partially reduced GO, and its application on humidity sensing and piezoresistive sensing will also be discussed. The excellent electrical properties and high specific surface area of graphene can provide a positive effect on various energy storage materials. However, the tendency to restack between sheets always remains to be solved. In this thesis, two-dimensional (2D) GO sheets were assembled into three-dimensional (3D) crumpled structure, and the effect of sheet morphology on electrochemical energy storage performances was studied. In order to prevent restacking of rGO sheets and ensure high specific surface area, crumpled and spherical structure of rGO, and CNT spacer insertion were also studied. Furthermore, we will discuss the fabrication of supercapacitor electrodes with superior performance by using porous rGO/CNT hybrids. Finally, the fabricated 3D porous rGO structure will be combined with platinum nanoparticles and applied as a electrocatalyst showing excellent performance in oxygen reduction reaction (ORR).ope

Oxidation Resistance of Fe and Cu Foils Coated with Reduced Graphene Oxide Sheets

Energy Conversion & StorageThe size and the physical properties of graphene oxide sheets were controlled by changing the oxidation temperature of graphite and graphene oxide sheet were applied for protection of metal surface as a diffusion barrier layer. Graphite oxide (GO) samples were prepared at different oxidation temperatures of 20 oC, 27 oC, and 35 oC using a modified Hummers’ method. The C/O ratio and the average size of the GO sheets varied according to the oxidation temperature: 1.26 and 12.4 μm at 20 oC, 1.24 and 10.5 μm at 27 oC, and 1.18 and 8.5 μm at 35 oC. This indicates that the C/O ratio and the average size of the graphene oxide sheets respectively increase as the oxidation temperature decreases. Moreover, it was observed that the surface charge and optical property of the graphene oxide sheets could be tuned by changing the temperature. This study demonstrates tunability of the physical properties of graphene oxide sheets and shows that the properties depend on functional groups generated during the oxidation process. The protection of metals such as Fe and Cu, which are widely used in industry, is of great importance because of necessity to preserve their surface properties. Traditional protection methods including organic layer, paints, polymer deposition and formation of oxide layer may have some problems such as change of physical property and surface deformation. Recently, oxidation resistance of graphene-coated metal has been reported. However, they used CVD-grown graphene which has some limits: difficulty in reproducible growth of graphene with large area and complicated process such as high temperature and gas. In this study, we demonstrate possibility of oxidation resistance of Cu and Fe coated with reduced graphene oxide (RGO) sheets. The RGO thin films on SiO2 substrate by layer-by-layer assembly was transferred to Cu and Fe substrate. Then, we checked the oxidation resistance of the RGO-coated metal substrates in the condition of 200 oC in air. The substrates were characterized by Raman spectroscopy and scanning electron microscopy. This study affords an advantage of a simple solution process which enables coating of large area.ope

Standard Error of Empirical Bayes Estimate in NONMEM® VI.

The pharmacokinetics/pharmacodynamics analysis software NONMEM® output provides model parameter estimates and associated standard errors. However, the standard error of empirical Bayes estimates of inter-subject variability is not available. A simple and direct method for estimating standard error of the empirical Bayes estimates of inter-subject variability using the NONMEM® VI internal matrix POSTV is developed and applied to several pharmacokinetic models using intensively or sparsely sampled data for demonstration and to evaluate performance. The computed standard error is in general similar to the results from other post-processing methods and the degree of difference, if any, depends on the employed estimation options

Expression of stm4467-encoded arginine deiminase controlled by the stm4463 regulator contributes to salmonella enterica serovar typhimurium virulence

Arginine deiminase (ADI), carbamate kinase (CK), and ornithine transcarbamoylase (OTC) constitute the ADI system. In addition to metabolic functions, the ADI system has been implicated in the virulence of certain pathogens. The pathogenic intracellular bacterium Salmonella enterica serovar Typhimurium possesses the STM4467, STM4466, and STM4465 genes, which are predicted to encode ADI, CK, and OTC, respectively. Here we report that the STM4467 gene encodes an ADI and that ADI activity plays a role in the successful infection of a mammalian host by S. Typhimurium. An STM4467 deletion mutant was defective for replication inside murine macrophages and was attenuated for virulence in mice. We determined that a regulatory protein encoded by the STM4463 gene functions as an activator for STM4467 expression. The expression of the ADI pathway genes was enhanced inside macrophages in a process that required STM4463. Lack of STM4463 impaired the ability of S. Typhimurium to replicate within macrophages. A mutant defective in STM4467-encoded ADI displayed normal production of nitric oxide by macrophages

Effect of Gambisan on the Inhibition of Adipogenesis in 3T3-L1 Adipocytes

This study was conducted to explore the antiadipogenic effect and possible mechanism of Gambisan on 3T3-L1 cells. For quality control, Gambisan was standardized by HPLC and the standard compounds ephedrine, epigallocatechin-3-gallate, and caffeine were screened. Cultured 3T3-L1 cells that had been induced to differentiate were treated with various concentrations of Gambisan or its major component extracts (Ephedra intermedia Schrenk, Atractylodes lancea DC., and Thea sinensis L.) for 72 hours for MTT assay to determine cell viability or 10 days for LDH assay, triglyceride assay, DNA content measurement, Oil red O staining, RT-PCR, and western blot. Gambisan significantly inhibited adipogenesis in 3T3-L1 cells by reducing triglyceride contents and lipid accumulation in a dose-dependent manner without obvious cytotoxicity. Viability and DNA content in 3T3-L1 cells treated with Gambisan were significantly higher than cells treated with the major component extracts at every concentration. The anti-adipogenic effects of Gambisan appeared to be mediated by a significant downregulation of the expression of lipoprotein lipase mRNA and PPARγ, C/EBPα, and SREBP-1 protein apart from the expression of hormone-sensitive lipase. Gambisan could act as a possible therapeutic agent for obesity. However, further studies including in vivo assays and clinical trials are needed to confirm the efficacy, safety and mechanisms of the antiobesity effects of Gambisan

Highly controllable transparent and conducting thin films using layer-by-layer assembly of oppositely charged reduced graphene oxides

A new approach for the fabrication of reduced graphene oxide (rGO) multilayers which can be used for transparent and conducting thin films was developed. This was achieved by using layer-by-layer (LbL) assembly of positively and negatively charged rGO sheets, which could provide highly controllable thin films in terms of thickness, transmittance, and sheet resistance. In particular, the thickness of the multilayer thin films of rGO was able to be controlled precisely in the subnanometre scale by similar to 0.46 nm via simply varying the number of stacking layers. Therefore, this method enabled an excellent control of the rGO multilayers over the optical and electrical properties, which are related to the thickness. Furthermore, we demonstrated the application of the rGO multilayers for an OLED device.close585

Evaluation of partial cranial cruciate ligament rupture with positive contrast computed tomographic arthrography in dogs

Computed tomographic arthrography (CTA) of four cadaveric canine stifles was performed before and after partial cranial cruciate ligament rupture in order to verify the usefulness of CTA examination for the diagnosis of partial cranial cruciate ligament rupture. To obtain the sequential true transverse image of a cranial cruciate ligament, the computed tomography gantry was angled such that the scanning plane was parallel to the fibula. True transverse images of cranial cruciate ligaments were identified on every sequential image, beginning just proximal to the origin of the cranial cruciate ligament distal to the tibial attachment, after the administration of iodinated contrast medium. A significant decrease in the area of the cranial cruciate ligament was identified on CTA imaging after partial surgical rupture of the cranial cruciate ligament. This finding implies that CTA can be used for assessing partial cranial cruciate ligament ruptures in dogs

Case report: Sclerosing encapsulating peritonitis in a cat with disseminated pancreatic adenocarcinoma of presumed ductal origin

A 9-year-old, neutered male, domestic short-haired cat was referred for recurrent ascites of unknown etiology over a week. Physical examination revealed abdominal distension and ultrasonography revealed a large volume of ascites throughout the abdominal cavity; this was interpreted as modified transudate. The mesentery and abdominal fat were hyperechoic and edematous. Fat tissue was assessed using fine-needle aspiration cytology, and adipocytes, fat-phagocytizing macrophages, and neutrophils were identified. Computed tomography revealed a pancreatic mass connected to the left pancreatic leg. Exploratory laparoscopy confirmed nodular masses and organ adhesions, leading to a tentative diagnosis of sclerosing encapsulating peritonitis. The cat was administered prednisolone, vitamin E, and tamoxifen but died 22 days after the initial therapy. Necropsy revealed a multi-lobulated pancreatic tumor (10 × 10 cm) tightly attached to the stomach and intestine, with a large amount of ascites. The peritoneum, stomach, intestine, and mesentery were covered with numerous disseminated nodules of various sizes (1–5 mm diameter). Microscopically, the tumor consisted of extensive adipose tissue, locally extensive inflammatory infiltrates, fibrous connective tissue, and small invasive proliferative glands. Well-defined small irregular glands composed of single-layered epithelial cells that appear to be of ductal origin were surrounded by an abundant desmoplastic stroma. Neoplastic nodules were widespread in the liver, stomach, peritoneum, mesentery, mesenteric lymph nodes, lungs, and urinary bladder. Immunohistochemistry revealed that the neoplastic glands were positive for pan-cytokeratin, confirming the pancreatic epithelial origin of the tumor. This is the first report of sclerosing encapsulating peritonitis accompanied by aggressive pancreatic adenocarcinoma of presumed ductal origin and extensive metastasis in a cat