Chang, YW
Jang, JY
Kim, NH
Lee, JW
Lee, HJ
Jung, WW
Dong, SH
Kim, HJ
Kim, BH
Lee, JI
Chang, R
Interleukin-1B and IL-1 receptor antagonist gene polymorphisms are associated with an increased risk of gastric cancer (GC) in Caucasian populations. However, recent studies could not find any association between IL-1B-511T polymorphism and the risk of GC in Asians. We tested for an association between IL-1 loci polymorphisms with increased gastric mucosal levels of IL-1beta and an increased risk of developing GC in a Korean population. Polymorphisms of IL-1A-889, IL-1B-31, IL-1B-511 and IL-1RN were genotyped in 434 controls and 234 patients with GC. Mucosal IL-10 cytokine was measured using an ELISA. The frequencies of IL-1A, IL-1B-511, IL-1B-31 and IL-1RN were not statistically different between controls and all patients with GC. After subclassification of GC, only patients with intestinal-type GC showed a higher frequency of IL-1B-31T homozygotes (OR = 2.2; 95% CI = 1.1-4.3) compared with controls. Risk was also significantly increased in these patients for IL-1B-31T homozygotes compared with patients with diffuse-type GC (OR = 3.4; 95% CI = 1.5-7.7). As in Caucasian populations, linkage disequilibrium between IL-1B-31 and IL-1B-511 was nearly complete, but the pattern of haplotype related to the risk of GC (IL-1B-31T/IL-1B-511C) was opposite (IL-1B-511T/IL-1B-31C). Mucosal IL-1beta levels in H. pylori-infected GC patients were higher in patients homozygous for IL-1B-31T compared with IL-1B-31C/T and IL-1B-31C/C. Thus, the combined effects of H. pylori infection and IL-1B-31T/IL-1B-511C polymorphisms with enhanced mucosal IL-1beta production contributed to the development of intestinal-type GC in this Korean population. (C) 2004 Wiley-Liss, Inc.
We present the anomalous magnetotransport observed in a narrow high mobility Hall device; both the peaks and minima in the Shubnikov-de Haas oscillations of the longitudinal resistance appear in the quantized plateau region of the Hall resistance. We interpret this feature as a consequence of an inhomogeneous distribution of two dimensional electron gas and provide a quantitative view with a model based on the edge current picture.
We investigated the Si-doped In0.5Ga0.5As quantum dots (QDs) grown by heterogeneous droplet epitaxy method and the annealing effects on the optical properties through photoluminescence (PL) spectroscopy. All together two or three peaks related to the QDs appear on the PL-spectra for undoped and lightly doped samples at low temperature. But, heavily doped sample, the free electron concentration is so high that it can screen the Coulomb interaction between electron and hole. Therefore, it is very difficult to form excitons. After, post-growth annealing, thermal intermixing was found to result in significant blue-shifts of the PL emission at annealing temperatures up to 800degreesC and a decrease of the intersublevel energy spacing (AE) as much as 22.7 meV. In addition, the inhomogeneously broad line width of PL spectra become narrow with increasing annealing temperature. These results have been explained by the interdiffusion of In Ga atoms at the interface between the QD and the GaAs barrier, which changes the composition of the QDs. (C) 2004 Elsevier B.V. All rights reserved.
Jee, C
Lee, J
Lee, JI
Lee, WH
Park, BJ
Yu, JR
Park, E
Kim, E
Ahnn, J
Protein localization in the postsynaptic density (PSD) of neurons is mediated by scaffolding proteins such as PSD-95 and Shank, which ensure proper function of receptors at the membrane. The Shank family of scaffolding proteins contain PDZ (PSD-95, Dig, and ZO-1) domains and have been implicated in the localizations of many receptor proteins including glutamate receptors in mammals. We have identified and characterized shn-1, the only homologue of Shank in Caenorhahditis elegans. The shn-1 gene shows approximately 40% identity over 1000 amino acids to rat Shanks. SHN-1 protein is localized in various tissues including neurons, pharynx and intestine. RNAi suppression of SHN-1 did not cause lethality or developmental abnormality. However, suppression of SHN-1 in the itr-1 (sa73) mutant, which has a defective inositol-1,4,5-trisphosphate (IP(3)) receptor, resulted in animals with altered defecation rhythm. Our data suggest a possible role of SHN-1 in affecting function of IP3 receptors in C. elegans. (C) 2004 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.
The synthesis of a novel germyl-substitutedpoly(p-phenylenevinylene) (PPV) derivative, poly(2-triethylgermyl-1,4-phenylenevinylene) (TEG-PPV), via a soluble precursor polymer is described for the first time. The light-emitting properties of TEG-PPV are compared with those of the silyl-substituted PPV homologue poly(2-trimethylsilyl-1,4-phenylenevinylene) (TMS-PPV). The precursor polymer is solution-processable. After carrying out thermal elimination on the precursor polymer film, the resulting fully conjugated polymer film was found to exhibit high thermal stability in air, and absorption that is shifted to the longer wavelength region owing to the extension of the pi-conjugated system. TEG-PPV exhibits efficient green light emission; the maximum PL emission of a TEG-PPV thin film was found to be at 515 nm. The HOMO and LUMO energy levels were also determined using photo-emission spectroscopy. The estimated HOMO and LUMO levels of TEG-PPV are 5.70 and 3.30 eV respectively. Single layered EL devices using TEG-PPV and TMS-PPV were fabricated in the ITO/Polymer/LiF/Al configuration. The performance of the TEG-PPV EL device was found to be comparable to that of the TMS-PPV device.
The effect of alkoxy substitution on the photophysical properties of poly(p-phenylenevinylene) [PPV] was investigated using steady-state and time-resolved photoluminescence, visible and infrared absorption spectroscopies. By substituting the alkoxy group (methoxy or butoxy) into the phenylene ring of PPV, the prolongation of effective conjugation length accompanied by the disappearance of the well-resolved vibronic structure was detected in the absorption spectra. These experimental results were attributable to the electron donating effect and the steric hindrance of the alkoxy substituent. These conjectures were compared with the effect of the alkoxy substitution on the photoluminescence and the Fourier-transform infrared spectra. Also, it was found that, alkoxy substitution slowed down the exciton relaxation process from the lower exciton state to the ground state, and lowered the height of the potential barrier in an excitonic potential well.
Photoluminescence (PL) properties of the residual shallow donors in GaN epitaxial layers grown by low-pressure metal organic chemical vapor deposition (LP-MOCVD were reported. Well-resolved free exciton transitions and luminescence due to the residual shallow donors were observed. The localization energy and binding energy of the neutral shallow donor were found to be 7 meV and 35 meV, respectively. In addition we identified a new ionized donor bound exciton center. Temperature dependence of the neutral donor bound exciton PL peak, was found to follow the same variation as the band gap with temperature and Varshni's coefficients were obtained. The linewidth of donor bound exciton transition increases linearly with temperature and their interaction with the acoustic phonons was thought to be the only contribution to the linewidth. From the PL intensities the thermal activation energy of the neutral donor bound exciton was estimated as 9 meV. The ratio of the total free excitons' intensity to the total bound excitons' intensity increases with temperature, which shows that the donor bound excitons thermally dissociate releasing free excitons.
Magnetic properties of Co chain-coated carbon nanotube (CNT) were investigated using a first-principles calculation. Binding energy between Co chain and CNT increased with the coverage ratio, and the adsorption of Co chains on CNT enhanced the conductance channel. Total magnetic moment of Co chains coated on CNT increased with the coverage ratio, while the magnetic moment per Co atom decreased due to spin flip of majority spin states in Co atoms. Spin polarization at the Fermi level of the Co chains was calculated to converge to that of bulk fcc Co. (c) 2006 Elsevier B.V. All rights reserved.
Vasiliou, Vasilis
Lee, Ji
Pappa, Aglaia
Petersen, Dennis R.
We have examined the NF-kappaB binding and functional activities in two stellate cell lines derived from normal (NFSC) and cirrhotic (CFSC) rat liver. Gel mobility shift assays revealed two bands in NFSC nuclear extracts that correspond to p65/p50 heterodimers and p50/p50 homodimers. In contrast, a single and more intense band that migrates faster was detected in CFSC nuclear extracts. This band supershifts with either p65 or p50 antibody. The differential NF-kappaB binding observed in these two cell lines appears to depend on the phosphorylation of the p65 subunit rather than the expression levels of either p65 or p50. The nonphosphorylated NF-kappaB form, present in CFSC cells, possesses significantly lower transcriptional activity compared to phosphorylated NF-kappaB, found in NFSC cells. To our knowledge, this is the first report on the NF-kappaB regulation at the p65 protein in hepatic stellate cells. It is likely that this regulation affects IL-6 expression and may represent a mechanism regulating hepatocyte death during fibrogenesis.
Chemostats supplied with limited lactose were used to ask whether it was possible to generate and isolate any mutant of Escherichia coli lactose permease which allowed cells to grow faster. The permease and beta-galactosidase activities of the chemostat culture initially rose together to reach a plateau. After 30 days, the former underwent a second increase alone. From this culture, a faster-growing mutant was isolated. Its permease gene was cloned, sequenced, and found to have a single base pair changed. Thymine at position 199 was changed to guanine, resulting in serine 67 being substituted by alanine. Cells bearing this mutant in the plasmid could grow faster than parents in 10 mu M lactose. The K-m of the mutant permease toward lactose was 1.4 mM, about half of the wild-type value. Thus, a mutant with higher affinity for substrate could be selected from the chemostat. (C) 1996 Academic Press, Inc.
Lee, Ji
Ahn, Seungyoung
Yoon, Seungjoon
Chun, Jongtae
In this paper, we suggest a topology design optimization of the address/command signals for DDR2 memory module to minimize the overshoot in waveforms when the 0.9V V(TT) terminations are removed for power saving and cost reduction. Simulations in frequency domain and time domain are performed for optimal signal integrity, and the optimized designs are verified by measurements.
Park, YM
Park, YJ
Kim, KM
Song, JD
Lee, JI
Yoo, KH
Kim, HS
Park, CG
Post-growth rapid thermal annealing (RTA) has been used to investigate an interdiffusion and the structural change in an InGaAs dots-in-a-well (DWELL) structure grown by molecular beam epitaxy using an alternately supplying InAs and GaAs sources. In the case of the as-grown sample, which has a metastable quantum structure due to an intentional deficit of source materials, it is found that an InGaAs quantum well (QW) coexists with the premature quantum dots (QDs), and an intermediate layer exists between the QW and the QDs. Through the RTA process at 600 and 800degreesC for 30 s, metastable structure changes into a normal DWELL structure composed of QDs and QW as a result of the intermixing of premature QDs and the intermediate layer. (C) 2004 American Institute of Physics.
Do, LM
Hwang, DH
Chu, HY
Kim, SH
Lee, JI
Park, H
Zyung, T
The initial state of dark spots in polymer light-emitting diodes (PLEDs) with poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) layer as an emissive layer has been investigated by in situ measurement with the interferometer, fluorescence microscope, and other various analytical instruments. Degradation of the device initiates with the dark spot that is the non-emissive portion of the polymer layer. The cross-sectional profile of interferometer image of Al electrode changes with operating time from dip to con-shaped sharp peak. It is clear that the dark spot originates from the pinhole leading to the severe damages on the microstructure of the polymer layer, polymer/metal interface, and metal electrode. Interferometer is a powerful tool for the investigation of the short-term degradation behavior of the polymeric EL devices. (C) 2000 Published by Elsevier Science S.A. All rights reserved.
We report on the optical and electrical transport properties of single-crystalline silicon carbide nanowires (SiC NWs). The NWs were fabricated by a chemical vapor deposition process, and had diameters of <100 nm and lengths of several mum. X-ray diffraction and transmission electron microscopy analysis showed the single-crystalline nature of NWs with a growth direction of <111>. Photoluminescence characterization showed blue emission at room temperature. The electrical measurements from a field effect transistor structure on individual NWs showed n-type semiconductor characteristics. The resistivity and estimated electron mobility on the NWs are 2.2x10(-2) Omega cm for 0 V of gate voltage and 15 cm(2)/(V s), respectively. Our low-resistivity SiC NWs could be applied to a high-temperature operation sensor and actuator due to its own excellent electrical and optical properties. (C) 2004 American Institute of Physics.