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Novel water-developable negative resists were designed to induce both cross-linking and polarity change upon exposure and bake. The matrix polymers were synthesized by copolymerization of glyceryl methacrylate and methacrolein. The acid-catalyzed acetalization of the polymer induced cross-linking, polarity change, and increase in dry-etch resistance. The resist formulated with this polymer and cast in a water-ethanol mixture, showed 0.7 μm line and space patterns using a mercury-xenone lamp in a contact printing mode and pure water as a developer.

We propose three dimensional-graphene nanonetworks (3D-GN) with pores in the range of 10 ∼ 20 nm as a potential candidate for thermoelectric materials. The 3D-GN has a low thermal conductivity of 0.90 W/mK @773 K and a maximum electrical conductivity of 6660 S/m @ 773 K. Our results suggest a straightforward way to individually control two interdependent parameters, σ and κ, in the nanoporous graphene structures to ultimately improve the figure of merit value.

We have examined a novel class of ketal based deep UV photoresist. 1,4-Dioxaspiro(4,4)nonane-2-methyl methacrylate was synthesized and polymerized. A ketal group of poly(1,4- dioxaspiro(4,4)nonane-2-methyl methacrylate) hydrolyzes under acid catalysis to give two alcohol functionalities and a cyclopentanone molecule. The ketal polymer is insoluble in an aqueous developer, while the hydrolyzed products are soluble.It was found the cyclopentanone product affects diffusion of acid in the resist. As a result, the generated cyclopentanone increases mobility of the acid significantly.

Extended abstract of a paper presented at Microscopy and Microanalysis 2006 in Chicago, Illinois, USA, July 30 – August 3, 2005

We demonstrate a graphene-coated polymer film as a transparent piezoresistive strain sensor. Strain sensitivity was tuned by controlling the thickness and density of the graphene layer as well as the adhesion force between graphene and the substrate. Chemically reducing the graphene oxide, thereby maximizing its adhesion to the substrate, while minimizing the coating density and thickness resulted in excellent transparency and high gauge factors. The fabrication method presented allows design optimization of transparent, high-performance, and sensitivity-tunable piezoresistive sensors, which can make inroads into such applications as wide-area strain sensors, self-sensing flexible electronics, and intelligent structural health monitoring.

We present a simple route towards a superhydrophobic graphene surface, which opens up possibilities for transparent flexible graphene-based electrodes with a non-wetting property. By tailoring the surface energy and surface roughness, superhydrophobic properties of graphene with a contact angle greater than 150° at an optical transparency of 72.7% were obtained.

A gold nanoparticle-coated and surface-textured TiO2 inverse opal (Au/st-TIO) structure that provides a dramatic improvement of photoelectrochemical hydrogen generation has been fabricated by nano-patterning of TiO2 precursors on TiO2 inverse opal (TIO) and subsequent deposition of gold NPs. The surface-textured TiO2 inverse opal (st-TIO) maximizes the photon trapping effects triggered by the large dimensions of the structure while maintaining the adequate surface area achieved by the small dimensions of the structure. Au NPs are incorporated to further improve photoconversion efficiency in the visible region via surface plasmon resonance. st-TIO and Au/st-TIO exhibit a maximum photocurrent density of ∼0.58 mA cm(-2) and ∼0.8 mA cm(-2), which is 2.07 and 2.86 times higher than that of bare TIO, respectively, at an applied bias of +0.5 V versus an Ag/AgCl electrode under AM 1.5 G simulated sunlight illumination via a photocatalytic hydrogen generation reaction. The excellent performance of the surface plasmon-enhanced mesoporous st-TIO structure suggests that tailoring the nanostructure to proper dimensions, and thereby obtaining excellent light absorption, can maximize the efficiency of a variety of photoconversion devices.

355 Background: Liver resection for multifocal hepatocellular carcinoma (HCC) is controversial. This study was conducted to outline our institution’s experience with liver resection for multifocal HCC. Methods: A retrospective review of patients who underwent liver resections from 1992 to 2011 for histologically confirmed hepatocellular carcinoma was performed. Multifocal disease was defined as more than 1 histologically proven HCC found in the liver resection specimens. Results: Of the 386 liver resections performed for HCC, 47 were performed for multifocal disease. Mean age was 60+11 years, and most patients (92%) had chronic liver disease. Hepatitis B was the most common etiology (60%), followed by hepatitis C (26%), and other etiologies (15%). Most patients were Child’s class A (89%). Most patients had intermediate Barcelona Clinic Liver Cancer (BCLC) stage (stage B) tumors (81%) and a minority of patients had early stage tumors (BCLC stage A, 19%). Major hepatectomy (>2 segments) was performed in 87% with an in hospital mortality of 6.4%. Major complications (Clavien-Dindo scale >3) occurred in 4 patients (9%). Median length of stay was 7 days and the rate of liver failure was 4.3%. Mean tumor number was 3+2 and the size of the largest lesion was 5+3 cm. Cirrhosis was present in 51% of patients. Majority of tumors were moderately differentiated (60%) and vascular invasion was present in 42%. The recurrence rate was 57% and the liver was the most common site of recurrence (81%). Treatment of recurrences occurred in 74% of patients: ablation (33%), chemotherapy (11%), transarterial chemoembolization (11%), resection (7.4%), sorafenib/radiation (7.4%) and transplantation (3.7%). Median disease free interval was 8 months and the overall survival was 18 months Conclusions: Liver resection for multifocal HCC can be performed safely in patients with chronic liver disease. Long term survival can be achieved in these patients and it should be considered as an option.

We have investigated the effects of the introduction of an antireflection layer consisting of a hierarchically patterned diffraction grating into a conventional TiO(2) working electrode on the power conversion efficiency (PCE) of a DSSC. High index-contrast TiO(2) nanowires (NWs) were grown in the circular holes of the two-dimensional diffraction grating prepared through the use of a polymer template fabricated via interference lithography (IL) for maximized photon trapping effects in the visible region of light. The larger scale dimension of the polymer template was determined using the beam parameters of the IL and the smaller scale dimension in the structures was controlled by the growth conditions of the TiO(2) NWs. Compared with a conventional DSSC, the hybrid nanostructure with an additional antireflection layer demonstrated higher and wider absorption bands of wavelength spectra, leading to an increased PCE due to enhanced light trapping effects achieved by the combination of antireflection and diffraction of the light on the front surface of the devices with minimum loss in the surface area of the hierarchical structure. The excellent performance of the optimized hybrid nanostructure indicates that the nanophotonic effects have strong potential for solar energy conversion, photocatalyst, and photoelectrode applications.

We report a robust and direct route to fabricate a three-dimensional nano-foam of few-layer graphene (3D-NFG) with large area coverage via a chemical vapor deposition (CVD) technique. Pyrolysis of polymer/nickel precursor film under a hydrogen environment, simply prepared by spin-coating, leads to the creation of nano-foam in the film and the reduction process of nickel ions. Carbonized-C and the nickel nano-frame formed from the pyrolysis are used as a solid carbon source and as a catalyst for the growth of graphene under CVD conditions, respectively. We investigate the use of 3D-NFG, with the advantage of large surface area and high conductivity, as an alternative to the Pt counter electrode material in dye sensitized solar cells. The excellent properties of 3D-NFG, fabricated in this simple and direct manner, suggest a great potential for interconnected graphene networks in electronic devices and photocatalytic sensors as well as in energy-related materials.

Objectives: This study examined the effect of the uncured dentin adhesives on the bond interface between the resin inlay and dentin. Materials and Methods: Dentin surface was exposed in 24 extracted human molars and the teeth were assigned to indirect and direct resin restoration group. For indirect resin groups, exposed dentin surfaces were temporized with provisional resin. The provisional restoration was removed after 1 wk and the teeth were divided further into 4 groups which used dentin adhesives (OptiBond FL, Kerr; One-Step, Bisco) with or without light-curing, respectively (Group OB-C, OB-NC, OS-C and OS-NC). Pre-fabricated resin blocks were cemented on the entire surfaces with resin cement. For the direct resin restoration groups, the dentin surfaces were treated with dentin adhesives (Group OB-D and OS-D), followed by restoring composite resin. After 24 hr, the teeth were assigned to microtensile bond strength (μ TBS) and confocal laser scanning microscopy (CLSM), respectively. Results: The indirect resin restoration groups showed a lower μ TBS than the direct resin restoration groups. The μ TBS values of the light cured dentin adhesive groups were higher than those of the uncured dentin adhesive groups ( p < 0.05). CLSM analysis of the light cured dentin adhesive groups revealed definite and homogenous hybrid layers. However, the uncured dentin adhesive groups showed uncertain or even no hybrid layer. Conclusions: Light-curing of the dentin adhesive prior to the application of the cementing material in luting a resin inlay to dentin resulted in definite, homogenous hybrid layer formation, which may improve the bond strength. [J Kor Acad Cons Dent 2011;36(6):490-497.]

Objectives: This in vitro study investigated whether short-term application of calcium hydroxide in the root canal system for 1 and 4 wk affects the fracture strength of human permanent teeth. Materials and Methods: Thirty two mature human single rooted mandibular premolars in similar size and dentin thickness without decay or restorations were hand and rotary instrumented and 16 teeth vertically packed with calcium hydroxide paste and sealed coronally with caviton to imitate the endodontic procedure and the other 16 teeth was left empty as a control group. The apicies of all the samples were sealed with resin, submerged in normal saline and put in a storage box at 37℃ to mimic the oral environment. After 1 and 4 wk, 8 samples out of 16 samples from each group were removed from the storage box and fracture strength test was performed. The maximum load required to fracture the samples was recorded and data were analysed statistically by the two way ANOVA test at 5% significance level. Results: The mean fracture strengths of two groups after 1 wk and 4 wk were similar. The intracanal placement of calcium hydroxide weakened the fracture strength of teeth by 8.2% after 4 wk: an average of 39.23 MPa for no treatment group and 36.01 MPa for CH group. However there was no statistically signif- icant difference between experimental groups and between time intervals. Conclusions: These results suggest that short term calcium hydroxide application is available during endodontic treatment. ABSTRACT 1 Shin EJ, Dental school student, Chonnam National University School of dentistry

Combining the physical principle of actuators with the basic concept of photonic crystals, colour-tunable three-dimensional (3D) photonic actuators were successfully fabricated. By controlling the d-spacings and the refractive index contrasts of the self-assembled 3D colloidal photonic crystals, colours of the photonic actuators were tuned. Various shapes of these 3D actuating objects were constructed by transforming the programmed 2D structures via bending, twisting and folding mechanisms. These 2D structures were first programmed by breaking the symmetry. The selective swellings were then applied as driving forces to control the shapes and colours of the photonic actuators. Scroll photonic actuators had been first demonstrated by bending the traditional 2D cantilever structure (K.-U. Jeong, et al., J.Mater.Chem., 2009, 19, 1956). By breaking the symmetry of a cantilever structure perpendicular to its long axis, polypeptide-/DNA-like 3D helical photonic actuators were obtained from the programmed 2D structure via twisting processes. Both left- and right-handed scrolls and helices with various colours can be achieved by changing the polarity of solvents. Different types of 3D actuators, such as cube, pyramid and phlat ball, were also demonstrated via the folding mechanism. The reversible 3D photonic actuators transformed from the programmed 2D structures via the bending, twisting and folding mechanisms may be applied in the field of mechanical actuators, and optoelectronic and bio-mimetic devices.

Combining the multi-faceted environmental responsiveness of polymers with photonically active structures, we developed spiral photonic actuators which can reversibly change both shape and colour in response to the chemical environment.

Brillouin light scattering is employed to record the phonon dispersion relation of two-dimensional (2D) hypersonic phononic crystals with square lattice plane group p4mm symmetry. The samples are single crystalline arrays of cylindrical holes with a lattice constant of 750nm and 35% porosity patterned in epoxy using interference lithography. The dispersion relation reveals the presence of a phononic band gap between 1.21 and 1.57GHz at the edge of the first Brillouin zone for elastic waves propagating along the [10] direction and conclusively demonstrates a band gap in a single crystalline 2D polymer based phononic structure at hypersonic frequencies.

Twelve Korean infectious bronchitis viruses (IBVs) were isolated in the field from chickens suspected of being carriers of infectious bronchitis between 2001 and 2003. The S1 glycoprotein genes of these IBV isolates were amplified by reverse transcriptase-polymerase chain reaction (RT-PCR) and analyzed by restriction fragment length polymorphism (RFLP) analysis. These Korean IBV isolates were classified into three groups according to their RFLP patterns obtained using the restriction enzyme HaeIII. Half of the twelve isolates were similar to the KM91 RFLP pattern, which is a common pattern in Korea. Three more isolates were related to the Arkansas strain pattern, but with some unique variations. The other three viruses showed variant RFLP patterns. For a comparison with the published sequences for non-Korean IBV strains, amplified PCR products from the twelve isolates were cloned and sequenced. The Korean IBV field isolates had 71.2-99.7% nucleotide sequence homology with each other and 45.9-80.7% nucleotide sequence homology with non-Korean IBV strains. With respect to the deduced amino acid sequence, the Korean IBV isolates had 71.5-99.3% similarity with each other and 44.9-80.3% similarity with non-Korean IBV strains. Phylogenetic tree analysis revealed that some of the IBV isolates appear to belong to a new group, different from the non-Korean IBV strains or from previously isolated Korean IBV strains. Specifically, the new Korean IBV isolates K10217-03, K3-3 and K1255-03 represented a separate group. These findings suggest that the Korean IBVs appear to be continuously evolving.