Pore-Water and Proton Transport in Polymer Electrolyte Membrane Fuel Cell: Molecular Dynamics and Mono- and Bimodal Wetting Treatments of Mesopore Hydrated Nafion.

Water states and water/proton transport in nanopores of hydrated Nafion, a chosen electrolyte in polymer electrolyte membrane fuel cell, are explained using molecular dynamics (MD) aided bimodal pore-size/water-wetting model. The bimodal model is developed based on the effective Debye screening length for pore water confined by heterogeneously ionized surface, and using small-angle X-ray scattering (SAXS) measurements and existing pore-size distribution. The smaller pores (1 nm) critically confine water and promote capillary condensation (hydrophilic-like), while hindering transport. The larger pores (4 nm) delay the condensation (hydrophobic-like), while allowing bulk-like transport. In a pore network, the small pores selectively wet, while the large pores provide dominant adsorption and transport channels, a novel attribute of the bimodal model. Also, in contrast to the existing Nafion backbone-hydration model, a hydration-dependent, temperature-dependent sulfonic acid surface density is proposed. The bimodal model succeeds in predicting the pore-water states and the transition in adsorption with capillary condensation in the large pores and negligible contribution from the small pores. These are in agreement with experiments. This transition also results in the proton conductivity jump by allowing dominant proton hopping through the larger pores in the network. The bimodal wetting describes the capillary water flow, where the small hydrophilic-like pores provide dominant flow channels, whereas water in the large pores remains immobile due to adsorption only. This water flow network results in lower liquid saturation distribution, in general agreement with the limited experimental results. At elevated temperatures, it is suggested that the sulfonic acid surface site density reduces due to pore surface stretching (relaxing backbone), resulting in hydrophobicity, most pronounced in the large pores. This delays the capillary condensation and decreases adsorption, and masks the transition in proton conductivity. The pore-water state/content for optimal cell operation is also discussed.Ph.D.Mechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/78840/1/gshwang_1.pd

Bactericidal surfaces with nanoparticles and light activated agents to inhibit healthcare associated infections

This thesis details the anti-biofouling property of superhydrophobic surface and white light-activated bactericidal polymers, and self-cleaning and bactericidal paints for preventing hospital associated infection. To investigate the anti-biofouling property of superhydrophobic surface over a long period of time, superhydrophobic surfaces were made using 1H, 1H, 2H, 2Hperfluorooctyltriethoxysilane, P25 TiO2 nanoparticles, ethanol, and double sided tape. The bacteria adhesion of the superhydrophobic surface was tested through full immersion of four different bacteria suspensions for 1, 4, 8, 16, and 24 h and then the result was compared with other surfaces containing glass, polystyrene, and polyurethane. Changes of the tested surfaces were investigated by water contact angle meter, SEM, AFM, and confocal microscope. Through a simple swell-encapsulation shrink process, white light-activated bactericidal polyurethane was produced. Toluidine blue O and silver nanoparticles were encapsulated into a polyurethane and characterised by water contact angle meter, UV/Vis spectrometer, fluorescence microscope, and material testing and inspection device. Crystal violet and acrylic latex, which is a widely used paint material for home decoration, were mixed together to produce photobactericidal paints for the first time. At various mixing ratio, crystal violet and acrylic latex were combined together. The paint coated slide was characterised using water contact angle meter, and UV/Vis spectrometer, and its stability was investigated through liquid leaching test Crystal violet, toluidine blue O, P25 TiO2 nanoparticles, and 1H, 1H, 2H, 2Hperfluorooctyltriethoxysilane were used to produce dual functional paints with superhydrophobic and bactericidal behaviour. TiO2, TBO, and CV paints were fabricated via physical and chemical reaction. The dual functional paint coated slides were investigated in terms of water repellence, self-cleaning, and anti-biofouling properties, and was also characterised by SEM, AFM, and UV/Vis spectrometer. Bactericidal properties of the treated polyurethane and paint, dual functional paints were assessed with Escherichia coli and Staphylococcus aureus. The tested samples demonstrated not only potent photobactericidal activity in white light (typical 5 hospital lamp) but also bactericidal activity in dark. It is expected that bactericidal materials detailed in this thesis will be useful for use in healthcare facilities in order to reduce hospital associated infections

Rook polynomials to and from permanents

AbstractIn this paper, we find an expression of the rook vector of a matrix A (not necessarily square) in terms of permanents of some matrices associated with A, and obtain some simple exact formulas for the permanents of all n×n Toeplitz band matrices of zeros and ones whose bands are of width not less than n−1

Antioxidant capacities and polyphenolics of Chinese cabbage (Brassica rapa L. ssp. Pekinensis) leaves

a b s t r a c t Chinese cabbage (Brassica rapa L. ssp. Pekinensis) is a green leafy vegetable used mainly in kimchi, salted and fermented dishes. Consumer preference for the leaf portion differs according to the type of dishes. In this study, Chinese cabbage was divided into three parts, and their antioxidant activities were investigated through in vitro assays. The total phenolic contents (TPC), total flavonoid contents (TFC), and vitamin C contents were also determined as indicators of antioxidant contents. The phenolic acids and flavonoids were separated and identified using high performance liquid chromatography (HPLC) and liquid chromatography/mass spectrometry (LC/MS). The outer leaf had the strongest antioxidant activity with the maximum antioxidant contents, followed by the mid-and inner leaves. Principal component analysis (PCA) revealed that outer leaf is positively related to caffeic acid, p-coumaric acid, ferulic acid, and myricetin contents, whereas the mid-and inner leaves are negatively related to sinapic acid contents

Mechanical Properties and Durability of Latex-Modified Fiber-Reinforced Concrete: A Tunnel Liner Application

This study assessed the mechanical properties and durability of latex-modified fiber-reinforced segment concrete (polyolefin-based macrosynthetic fibers and hybrid fiber-macrosynthetic fiber and polypropylene fiber) for a tunnel liner application. The tested macrosynthetic fiber-reinforced concrete has a better strength than steel fiber-reinforced concrete. The tested concrete with blast furnace slag has a higher chloride ion penetration resistance (less permeable), but its compressive and flexural strengths can be reduced with blast furnace slag content increase. Also, the hybrid fiber-reinforced concrete has higher compressive strength, flexural strength, chloride ion water permeability resistance, impact resistance, and abrasion resistance than the macrosynthetic fiber-reinforced concrete. The modified fiber improved the performance of concrete, and the hybrid fiber was found to control the formation of micro- and macrocracks more effectively. Therefore, overall performance of the hybrid fiber-reinforced concrete was found superior to the other fiber-reinforced concrete mixes tested for this study. The test results also indicated that macrosynthetic fiber could replace the steel fiber as a concrete reinforcement

Production of an EP/PDMS/SA/AlZnO Coated Superhydrophobic Surface through an Aerosol-Assisted Chemical Vapor Deposition Process

In this study, a superhydrophobic coating on glass has been prepared through a single-step aerosol-assisted chemical vapor deposition (AACVD) process. During the process, an aerosolized precursor containing polydimethylsiloxane, epoxy resin, and stearic acid functionalized Al-doped ZnO nanoparticles was deposited onto the glass at 350 °C. X-ray photoelectron spectroscopy, scanning electron microscopy, and atomic force microscopy showed that the precursor was successfully coated and formed a nano/microstructure (surface roughness: 378.0 ± 46.1 nm) on the glass surface. The coated surface had a water contact angle of 159.1 ± 1.2°, contact angle hysteresis of 2.2 ± 1.7°, and rolling off-angle of 1°, indicating that it was superhydrophobic. In the self-cleaning test of the coated surface at a tilted angle of 20°, it was shown that water droplets rolled and washed out dirt on the surface. The stability tests showed that the surface remained superhydrophobic after 120 h of exposure to ultraviolet (UV) irradiation and even after heat exposure at 350 °C. In addition, the surface was highly repellent to water solutions of pH 1–13. The results showed that the addition of the functionalized nanoparticles into the precursor allowed for the control of surface roughness and provided a simplified single-step fabrication process of the superhydrophobic surface. This provides valuable information for developing the manufacturing process for superhydrophobic surfaces

Three newly recorded plants of South Korea: Muhlenbergia ramosa (Hack. ex Matsum.) Makino, Dichanthelium acuminatum (Sw.) Gould & C.A. Clark and Rottboellia cochinchinensis (Lour.) Clayton

AbstractThree new Poaceae species are reported in South Korea. Muhlenbergia ramosa was found in Boryeong-si, Iksan-si, Jangsu-gun and Gwangju. Dichanthelium acuminatum and Rottboellia cochinchinensis were found in Jeonju-si, Jeollabuk-do and Seogwipo-si, Jeju-do which were thought to be alien species. Genus Dichanthelium and Rottboellia are newly reported in South Korea. Muhlenbergia ramosa was thought to be native to Korea

High-Temperature Corrosion Behaviors of Structural Materials for Lead-Alloy-Cooled Fast Reactor Application

The corrosion of nuclear-grade steels in lead-bismuth eutectic (LBE) complicates the realization of high coolant temperatures. Corrosion tests of T91, HT9, and SS316L were performed in static cells at 600 degrees C for 2000 h at an oxygen level of 10(-6) wt.%. The obtained corrosion surfaces of post-processed samples were characterized by several microscopy methods. Up to 1000 h, all the alloys exhibited an evolution of duplex oxide layers, which were spalled until 2000 h due to their increased thickness and decreased integrity. Following the spallation, a thin internal Cr-rich oxide layer was formed above the Cr-depleted zone for T91 and HT9. SS316L was penetrated by LBE down to 300 mu m in severe cases. A comparison on the corrosion depths of the materials with regard to the parabolic oxidation law with abundant literature data suggests that it may lose its validity once the duplex layer is destroyed as it allows LBE to penetrate the metal substrate