Young Seok Song

New High-Tc Superconductor Family of Cu-Based Cu1-xBa2Can-1CunO2n+4-δ with Tc>116 K

A new high-temperature and nontoxic superconductor family of Cu1-xBa2Can-1CunO2n+4-δ with critical temperature (Tc)>116 K was discovered. These materials were prepared by the high-pressure technique. A superconductor sample with the highest T c contains mainly a Cu1-x Ba2Ca3Cu4O12-δ phase. The T c value of the Cu1-x Ba2Ca3Cu4O12-δ phase is 116.4 K. The phase has two kinds of tetragonal structures: body-centered tetragonal (bct) and simple tetragonal. The lattice parameters of bct are a=7.7114 A and c=35.986 A. The disordering or full occupation of Cu-vacancy sites leads to the simple tetragonal phase with the space group of P4/mmm and the half values of the lattice constants (a=3.8557 A and c=17.993 A) of the bct phase. The relationship between the lattice constant c and the number of CuO2 layers n is c/2=8.4+3.2(n-1) ( A). The small CuO2-block spacing (8.4 A) of this family suggests a lower anisotropy and higher J c than in Hg- and Tl-based superconductor families.

Properties of epoxy nanocomposites filled with carbon nanomaterials

Abstract Rheological, mechanical, electrical, and thermal properties of epoxy nanocomposites containing carbon nanomaterials (CNMs) were investigated with different loading. Two kinds of CNMs - multiwalled carbon nanotubes (MWNTs) and carbon blacks (CBs) - were selected to examine the effect of their geometrical structure on various properties. Under sonication, MWNTs and CBs (0.5, 1.0, and 1.5 wt.-%) were mixed with the epoxy resin by using a solvent. Dispersion of the CNMs in the epoxy nanocomposites was characterized by means of transmission electron microscopy and field emission scanning electron microscopy. Carbon nanotubes (CNTs)/epoxy composites show significant differences from the CBs/ epoxy composites due to their high aspect ratio. It was found that the CNTs/epoxy composites exhibit non-Newtonian rheological behaviour, while the CBs/epoxy composites with the same weight content show Newtonian behaviour. The CNTs/ epoxy composites have better mechanical and thermal properties than the CBs/ epoxy composites. In the CNTs nanocomposites, the percolation threshold of electrical conductivity is found to be less than 0.5 wt.-%, which is too low to be obtained by using other carbon materials such as carbon fibre in polymer composites. Effects of CNM content on the various properties were also examined. As loading of the CNMs increased, improved results were obtained.

Prediction of permeability tensor for plain woven fabric by using control volume finite element method

The complete prediction of the second order permeability tensor for a three dimensional multi-axial preform is critical if we are to model and design the manufacturing process for composites by considering resin flow through a multi-axial fiber structure. In this study, the in-plane and transverse permeabilities for a woven fabric were predicted numerically by the coupled flow model, which combines microscopic and macroscopic flows. The microscopic and macroscopic flows were calculated by using 3-D CVFEM(control volume finite element method) for micro and macro unit cells. To avoid a checkerboard pressure field and improve the efficiency of numerical computation, a new interpolation function for velocity is proposed on the basis of analytical solutions. The permeability of a plain woven fabric was measured by means of an unidirectional flow experiment and compared with the permeability calculated numerically. Reverse and simple stacking of plain woven fabrics were taken into account and the relationship between the permeability and the structures of the preform such as the fiber volume fraction and stacking order is identified. Unlike other studies, the current study was based on a more realistic three dimensional unit cell. It was observed that in-plane flow is more dominant than transverse flow within the woven perform, and the effect of the stacking order of a multi-layered preform was negligible.

Irreversible and time-dependent magnetization in TDAE-C60

Abstract Precise measurements of low-field magnetization and magnetic susceptibility of TDAE-C 60 (TDAE; tetrakis(dimethylamino)ethylene) by SQUID magnetometer are reported. Irreversible magnetization effect, i.e. a difference between zero-field-cooled and field-cooled magnetization is clearly observed for the first time. Also, an extremely slow relaxation of magnetization, characteristic of a spin-glass-like freezing process, is observed at low temperatures.

Methylation status of long interspersed element-1 in advanced gastric cancer and its prognostic implication.

BackgroundsReportedly, the pyrosequencing methylation assay can produce inconsistent results between paired snap-frozen and formalin-fixed paraffin-embedded archival tissue samples. In this study, we assayed the methylation levels at four individual CpG sites of L1 using pyrosequencing and found that the methylation levels at individual CpG sites were different but were closely correlated between paired snap-frozen and formalin-fixed paraffin-embedded tissue samples. We aimed to determine whether low methylation status of L1 is associated with gastric cancer patient prognosis.MethodsWe analyzed 434 formalin-fixed paraffin-embedded tissue samples of advanced gastric cancer for their methylation status at four CpG sites of L1 [nucleotide positions 328, 321, 318, and 306 of X58075 (Genbank)] using pyrosequencing, and correlated the L1 methylation level with clinicopathological features.ResultsOlder age at onset, males, tumor location at antrum or lower body, intestinal type, and lymphatic or venous invasion were associated with a low average methylation level of L1 at the two CpG sites 1 and 4 combined. The average methylation level of L1 at CpG sites 1 and 4 combined was significantly lower in microsatellite-stable and EBV-negative gastric cancers than in EBV-positive or microsatellite-unstable gastric cancers. Low methylation status of L1 was independently correlated with shorter overall survival and disease-free survival time.ConclusionOur findings indicate that the discrepancy in the methylation level of L1 between fresh tissue and formalin-fixed paraffin-embedded tissue samples depends on the CpG sites considered, and that the methylation status of L1 at CpG sites 1 and 4 combined could be utilized as a prognostic parameter for advanced gastric cancers.

Vacuum nanohole array embedded phosphorescent organic light emitting diodes.

Light extraction from organic light-emitting diodes that utilize phosphorescent materials has an internal efficiency of 100% but is limited by an external quantum efficiency (EQE) of 30%. In this study, extremely high-efficiency organic light emitting diodes (OLEDs) with an EQE of greater than 50% and low roll-off were produced by inserting a vacuum nanohole array (VNHA) into phosphorescent OLEDs (PhOLEDs). The resultant extraction enhancement was quantified in terms of EQE by comparing experimentally measured results with those produced from optical modeling analysis, which assumes the near-perfect electric characteristics of the device. A comparison of the experimental data and optical modeling results indicated that the VNHA extracts the entire waveguide loss into the air. The EQE obtained in this study is the highest value obtained to date for bottom-emitting OLEDs.

Liquid Slip on a Nanostructured Surface

We explored a liquid slip, referred to as the Navier slip, at liquid-solid interface. Such a slip is provoked by the physicochemical features of the liquid-solid system. The goal of this study was to investigate the effect of a nanoengineered surface structure on liquid slip by fabricating the self-assembly structure of nano Zinc oxide (n-ZnO). We have also examined how the liquid-solid surface interaction controlled by hydrophobic chemical treatment affects the liquid slip. The findings showed that liquid slip increases with decreasing the characteristic length scales (e.g., channel height and depth), resulting in drag reduction. It was also found that dewetted (Cassie) state due to the generation of air gap developed by n-ZnO was more critical for the liquid slip than the minimization of interface interaction. The linear and nonlinear Navier slip models showed that liquid slip behavior is more obvious when increasing the nonlinearity. This study will contribute to understanding of the underlying physics behind fluid slip phenomena, such as the Navier slip for Newtonian liquids and Maxwells slip for Newtonian gases.

New high-Tc superconductor families of Ag1−xCuxBa2Can−1CunO2n+3−y and CuBa2Can−1CunO2n+4−y with Tc>116 K

Abstract New high-temperature and nontoxic superconductor families of Ag 1−x Cu x Ba 2 Ca n−1 Cu n O 2n+3−y with Tc=117 K and CuBa 2 Ca n−1 Cu n O 2n+4−y with Tc=116 K were discovered. These materials were prepared by the high-pressure technique. The highest Tc was obtained for n=4 i.e. Ag 1−x Cu x Ba 2 Ca 3 Cu 4 O 11−y (Ag-1234) and CuBa 2 Ca 3 Cu 4 O 12−y (Cu-1234) phases. Their structures were analyzed as a tetragonal structure for simplicity. The Ag-1234 phase has the lattice parameters of a=3.8635 A and c=18.111 A , while the lattice parameters of the Cu-1234 phase are a=3.8557 A and c=17.993 A . The Ag-based superconductors have higher Tc and larger lattice parameters than the Cu-based for n=3, 4, and 5. The relationships between the lattice parameter c and the number of CuO 2 layers r are c=8.5 + 3.2(n−1) ( A ) and c=8.4 + 3.2(n−1) ( A ) for Ag and Cu-based superconductors, respectively. The small CuO 2 -block spacing (8.5 and 8.4 A) of these families suggests a lower anisotropic superconductivity than Hg- and Tl-based superconductor families. The occupation of Ag sites was analyzed.

Correlation between Internal Structure and Electrochemical Impedance Spectroscopy of Multiphase Slurry Systems

Slurry for lithium-ion batteries is prepared from an active material, a carbon conductive additive, and a polymeric binder in a solvent, and its morphological change is evaluated over time using electrochemical impedance spectroscopy. A schematic model of the internal structure and dispersion states of the slurry components during 7 days of storage is proposed on the basis of the electrochemical impedance spectroscopy (EIS) measurement. The EIS results reveal that the conductive path constructed by the network structure of the slurry components breaks over time, which can be worsened by mechanical agitation. In order to confirm the morphological change, the slurry is freeze-dried and then prepared to fixate the locations of the slurry components. The existence of a network structure (or flocculation) is verified by morphological observations. In addition, the dispersity index and Micro-CT are introduced as new methods representing the dispersion state of the slurry components.

Clinicopathologic, molecular, and prognostic implications of the loss of EPCAM expression in colorectal carcinoma

We aimed to comprehensively investigate the clinicopathologic and molecular implications of altered epithelial cell adhesion molecule (EPCAM) expression in colorectal carcinoma (CRC). EPCAM immunohistochemical expression, EPCAM 3′ end deletion, EPCAM promoter methylation, microsatellite instability (MSI), and the CpG island methylator phenotype (CIMP) were analyzed in large cohorts of human CRCs. Among 218 MSI-high CRCs, complete loss (CL) of EPCAM expression was observed in two cases, both of which displayed MSH2 deficiency and EPCAM 3′ deletion. Thirty-one of the 218 MSI-high CRCs demonstrated the partial loss (PL) of EPCAM expression without EPCAM deletion or methylation and were correlated with CIMP-high and poor disease-free survival. Histologically, foci exhibiting EPCAM loss in EPCAM-PL tumors were dominantly distributed in poorly differentiated tumor components and/or in the invasive tumor front. The implications of EPCAM-PL were further validated in a consecutive series of 726 CRCs. EPCAM-PL (n = 50; 6.9%) was also associated with CIMP-high and adverse pathologic factors and was confirmed to be an independent poor prognostic factor in CRC (HR, 1.57; 95% CI, 1.04 to 2.39). EPCAM-CL can be used to screen for EPCAM deletion-induced Lynch syndrome-associated CRC, whereas EPCAM-PL can be used as an indicator of tumor aggressiveness and poor prognosis in CRC.