Showing papers by "Hyun-Chul Kim published in 2001"

Suppression of hadrons with large transverse momentum in central Au + Au collisions at √sNN = 130 GeV

Abstract: Transverse momentum spectra for charged hadrons and for neutral pions in the range 1 Gev/c < P-T < 5 GeV/c have been measured by the PHENIX experiment at RHIC in Au + Au collisions at rootS(NN) = 130 GeV. At high p(T) the spectra from peripheral nuclear collisions are consistent with scaling the spectra from p + p collisions by the average number of binary nucleon-nucleon collisions. The spectra from central collisions are significantly suppressed when compared to the binary-scaled p + p expectation, and also when compared to similarly binary-scaled peripheral collisions, indicating a novel nuclear-medium effect in central nuclear collisions at RHIC energies.

Human kallikrein gene 5 (KLK5) expression is an indicator of poor prognosis in ovarian cancer.

Abstract: Kallikrein gene 5 (KLK5, also known as KLK-L2), located on chromosome 19q13.4, is one of the newly identified members of the kallikrein gene family, which is a subgroup of the serine protease enzyme family. In normal human tissues, KLK5 is highly expressed in skin, mammary gland and testis. Preliminary RT-PCR analysis has indicated that KLK5 is expressed in a subset of ovarian tumours. We have thus hypothesized that KLK5 may be a new prognostic indicator in ovarian cancer. We have examined the mRNA expression of KLK5 in 142 malignant ovarian tissues. Tumours were pulverized, total RNA was extracted, and cDNA was prepared by reverse transcription. KLK5 was amplified by PCR using gene specific primers, and the identity of the PCR product was verified by sequencing. Ovarian tissues were then classified as KLK5 positive or negative, based on ethidium bromide staining of the PCR product on agarose gels. KLK5 was found to be highly expressed in 58/142 (41%) of ovarian cancer samples while its level of expression was very low in normal ovarian tissues. We found a strong positive relation between KLK5 expression and tumour grade (P = 0.006) and disease stage (P = 0.027). Univariate survival analysis revealed that patients with ovarian tumours positive for KLK5 expression had an increased risk for relapse and death (P = 0.018 and 0.022, respectively). In multivariate analysis, KLK5 expression showed independent prognostic value only in the subset of tumours with lower grade disease (grades I and II). We conclude that KLK5 expression is associated with more aggressive forms of epithelial ovarian carcinoma and has indepdent prognostic value in low grade tumours. © 2001 Cancer Research Campaign http://www.bjcancer.com

Neutrino Astronomy with the MACRO detector

Abstract: High-energy gamma-ray astronomy is now a well-established —eld, and several sources have been dis- covered in the region from a few gigaelectron volts up to several teraelectron volts. If sources involv- ing hadronic processes exist, the production of photons would be accompanied by neutrinos too. Other possible neutrino sources could be related to the annihilation of weakly interacting, massive particles (WIMPs) at the center of galaxies with black holes. We present the results of a search for pointlike sources using 1100 upward-going muons produced by neutrino interactions in the rock below and inside the Monopole Astrophysics and Cosmic Ray Observatory (MACRO) detector in the underground Gran Sasso Laboratory. These data show no evidence of a possible neutrino pointlike source or of possible correlations between gamma-ray bursts and neutrinos. They have been used to set —ux upper limits for candidate pointlike sources which are in the range 10~14¨10~15 cm~2 s~1. Subject headings: elementary particlesgamma rays: observations

Thermally oxidized GaN film for use as gate insulators

Abstract: The structural and electrical characteristics of a thermally grown gallium oxide on GaN films were investigated. A furnace oxidation at 850 °C for 12 h resulted in the formation of monoclinic β-Ga2O3, 88 nm in thickness. From the I–V measurements of the metal–oxide–semiconductor (MOS) structure, the breakdown field strength (EBD) was found to be 3.85±0.32 MV cm−1. Under gate voltage sweep, C–V hysteresis was observed due to the oxide charge trap. By comparing the ideal and experimental C–V curves, the oxide charge density (Nf) was calculated to be 6.77×1011 cm−2. These results suggest that the thermally grown Ga2O3 is suitable for gate dielectric applications of power MOS field-effect transistors.

Temperature dependence of photoluminescence of InGaN films containing In-rich quantum dots

Abstract: The temperature dependence of the photoluminescence (PL) of InGaN films, grown by metalorganic chemical vapor deposition, has been investigated. A strained InGaN thin film which contains composition-fluctuated regions shows the so-called S-shaped temperature dependence of the dominant PL peak energy. However, an InGaN thick film which contains quantum dot-like In-rich regions shows a sigmoidal temperature dependence of the dominant PL peak energy, as the result of a transfer of carriers from the band-edge related luminescent centers to quantum dot-like In-rich regions. It is also found that the activation energy for the thermal quenching of PL intensity in the InGaN thick film which contains quantum dot-like In-rich regions is larger than that in the strained InGaN thin film which contains composition-fluctuated regions.

Thermal behaviour of poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone) tri-block copolymers

Abstract: Thermal behavior of poly(e-caprolactone)-poly(ethylene glycol)-poly(e-caprolactone) tri-block copolymers with different block lengths is examined. Thermal behavior of specimens crystallized under the isothermal and dynamic condition are characterized by DSC. Also WAXD and SAXS are employed to investigate the structure. Depending on the relative length of each block, tri-block copolymers can be classified into three groups: PCL dominant crystallization; PEG dominant crystallization; and the competing case. When the crystallization of PEG and PCL are competing, the crystallization of each block shows strong dependency on the thermal hystory of crystallization, leading to multiple melting and crystallization peaks. Also, the typical micro-phase separation of block copolymers seems to play an important role, competing with crystallization, especially under the dynamic crystallization condition.

Double Diffraction Dissociation at the Fermilab Tevatron Collider

Abstract: We present results from a measurement of double diffraction dissociation in $\overline{p}p$ collisions at the Fermilab Tevatron collider. The production cross section for events with a central pseudorapidity gap of width $\ensuremath{\Delta}{\ensuremath{\eta}}^{0}g3$ (overlapping $\ensuremath{\eta}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0$) is found to be $4.43\ifmmode\pm\else\textpm\fi{}0.02(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}1.18(\mathrm{syst})\mathrm{mb}$ [ $3.42\ifmmode\pm\else\textpm\fi{}0.01(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}1.09(\mathrm{syst})\mathrm{mb}$] at $\sqrt{s}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1800[630]\mathrm{GeV}$. Our results are compared with previous measurements and with predictions based on Regge theory and factorization.

Development of a sensor information integrated expert system for optimizing die polishing

Abstract: This paper presents a polishing expert system integrated with sensor information which can modify the polishing sequence and conditions initially set by the system using the on-site polishing status detected. A practical system using AE sensors is developed for rotational and curved-surface polishing. A database and a knowledge base for polishing processes are established by using the results of experiments and also expert's experience. Evaluations are performed for a die of an automobile headlight lamp by using both the sensor-integrated expert system and the expert system without sensor. The results show that the sensor-integrated expert system provides more optimal polishing conditions since the proposed system takes advantage of the on-line sensor information.

Effects of sulfur treatment on electrical and optical performance of InGaN/GaN multiple-quantum-well blue light-emitting diodes

Abstract: The results of the sulfur treatment of multiple-quantum-well (MQW) light-emitting diodes (LEDs) with (NH4)2S and (NH4)2S+t-C4H9OH solutions prior to the deposition of a light-transmitting p-electrode metal are presented The room-temperature I–V curves showed that the forward voltages of MQW LEDs treated with the two sulfur solutions decrease by 012 and 035 V at 20 mA, respectively, compared to the untreated MQW LED, as the result of an improvement in p-Ohmic contact characteristics The relative light-output power and external quantum efficiency of MQW LEDs increased by a factor of 128 for the (NH4)2S treated sample and 223 for the (NH4)2S+t-C4H9OH treated sample compared to the untreated sample In addition, the reverse leakage current characteristic of MQW LEDs was reduced as a result of sulfur treatment This can be attributed to the passivation of surface and sidewall damages formed after the dry-etching process for a reliable pattern transfer The present results indicate that the sulfur treatme

Effect of an oxidized Ni/Au p contact on the performance of GaN/InGaN multiple quantum well light-emitting diodes

Abstract: Feasibility of an oxidized Ni/Au p contact on some aspects of device applications for a GaN/InGaN multiple quantum well light-emitting diode (LED) was investigated. For the oxidation of Ni/Au p contact, furnace annealing of a completely fabricated LED was performed at 600 °C for 5 min in an O2 ambient. For the case of LED with an oxidized Ni/Au system, the I–V measurements showed a reduction in series resistance of the diode by 17.2%. In addition, the optical output power of the oxidized LED was increased by a factor of 2. However, a significant degradation in reliability characteristics was observed, which might detract from the direct application of the Ni/Au oxidation process. We also conclude that the improvement of oxidized Ni/Au contact properties is mainly due to the formation of an intermediate NiO layer, rather than an enhancement in p-type activation.

Strange form factors in the context of SAMPLE, HAPPEX, and A4 experiments

Abstract: The strange properties of the nucleon are investigated within the framework of the SU(3) chiral quark-soliton model assuming isospin symmetry and applying the symmetry conserving SU(3) quantization. We present the form factors $G^0_{E,M}(Q^2)$, $G^Z_M(Q^2)$ and the electric and magnetic strange form factors $G^s_{E,M}(Q^2)$ incorporating pion and kaon asymptotics. The results show a fairly good agreement with the recent experimental data from the SAMPLE and HAPPEX collaborations. We also present predictions for future measurements including the A4 experiment at MAMI (Mainz).

The transport of a reversible proton pump antagonist, 5, 6-dimethyl-2-(4-Fluorophenylamino)-4-(1-methyl-1,2,3, 4-tetrahydroisoquinoline-2-yl) pyrimidine hydrochloride (YH1885), across caco-2 cell monolayers.

Abstract: 5,6-Dimethyl-2-(4-fluorophenylamino)-4-(1-methyl-1,2,3,4-tetrahydroisoquinoline-2-yl) pyrimidine hydrochloride (YH1885) is under development as a novel acid pump antagonist by Yuhan Research Center. Previous studies have suggested that the AUC and Cmax of orally dosed YH1885 are dose-dependent in the range of 2 to 500 mg/kg. The objective of the present study was to investigate the absorption mechanism of YH1885 using a human colon carcinoma cell line, Caco-2. The cells were grown to confluency on a permeable polycarbonate membrane insert to permit loading of YH1885 on either the apical or basolateral side of the cell monolayer. The flux across the monolayer from the apical to basolateral side was 3 to 5 times greater than that from the basolateral to apical side. The uptake of YH1885 into the Caco-2 cell monolayer was saturable and appeared to be mediated by a high-affinity transporter, with an apparentKm of 1.47 ± 0.21 μM and aVmax of 25.14 ± 1.16 pmol/cm2/40 s. The apical to basolateral transport across the monolayer was Na+-independent, H+-sensitive, and energy-dependent. The transport was inhibited significantly by the presence of structural analogs of YH1885 (e.g., YH957, YH1070, and YH1041), some pyrimidine nucleobases (uracil and 5-methyluracil), and nucleobase transport inhibitors (e.g., papaverine, dipyridamole, and phloridzin). These results demonstrate that the apical to basolateral transport of YH1885 across the Caco-2 cell monolayer is partially mediated by a nucleobase transport system, which exhibits high-affinity and energy-dependent properties for YH1885. Saturation of this transport system, in addition to the limited solubility of YH1885 (i.e., ∼5.3 μM), appears to contribute to the dose-dependent bioavailability of the drug.

Test of CsI (Tℓ) crystals for the dark matter search

Abstract: Searches for weakly interacting massive particles (WIMP) can be based on the detection of nuclear recoil energy in CsI(Tl) crystals. We demonstrate that low-energy gamma rays down to a few keV are detected with CsI(Tl) crystal detector. A clear peak at 6 keV is observed using an X-ray source. Good energy resolution and linearity have been achieved down to the X-ray region. In addition, we also show that alpha particles and gamma rays can be clearly separated using the different time characteristics of the crystal.

Static reactive-power compensator using soft-switching current source inverter

Abstract: This paper describes a static reactive-power compensator using a soft-switching scheme The proposed system is composed of a three-phase current-source inverter with an H-type soft-switching module, which consists of two semiconductor switches, two diodes, and an L-C resonant circuit The operation of the proposed system was analyzed in detail through a theoretical approach and computer simulation with SPICE A scaled prototype was built and tested for verifying the feasibility of hardware implementation The proposed system would be suitable for a high-power application with less switching loss

Effects of N 2 O Plasma Surface Treatment on the Electrical and Ohmic Contact Properties of n-Type GaN

Abstract: An N2O plasma surface treatment was introduced to improve the electrical and ohmic contact properties of the n-GaN surface. Hall measurements indicate that the sheet carrier concentration and sheet resistance of the N2O treated n-GaN is considerably improved compared to as-grown samples. In addition, it is shown that the Ti/Al contact on the N2O plasma surface-treated GaN results in a significant reduction in the specific contact resistance by about one order of magnitude, compared to that for a conventionally treated GaN. Based on the Hall measurement and Auger electron spectroscopy data, the observed improvements in the electrical and contact properties are due to the formation of a layer of highly conductive gallium oxynitride (GaOxN12x) at the surface. © 2001 The Electrochemical Society. @DOI: 10.1149/1.1406998# All rights reserved.

Bonding pad structure of semiconductor device and method for fabricating the same

Abstract: A bonding pad structure of a semiconductor device has an increased bonding pad height to prevent an increase in mechanical stress caused by a large step difference between a metal pad, exposed through a pad window region, and a protective layer. A misalignment margin is also increased. Preferably, a second metal pad is arranged in direct contact with a first metal pad and a conductive layer pattern such as P-poly pattern. This direct contact is preferably made at an external portion, or outside, of a pad window region, thereby leaving insulation layers between the P-poly pattern and the first metal pad and between the first and second metal pads intact in the pad window regions. According to various aspects of this invention, the height of the bonding pad can be raised as high as the thickness of the remaining insulation layers to reduce mechanical stress on the bonding pad without requiring additional process steps. In addition, the step differences between the metal pad exposed through the pad window region and the protective layer can be reduced, thereby increasing the misalignment margin.

Cloning, expression, and complementation test of the RNA lariat debranching enzyme cDNA from mouse.

Abstract: The RNA lariat debranching enzyme of mouse (mDBR1) was cloned by screening a NIH/3T3 cDNA library. The sequence of full-length mDBR1 cDNA contained a single 515 amino acid open reading frame of 58 kDa protein. Comparison of the amino acid sequence of mDBR1 to other DBR proteins showed 40%, 44%, 43%, 42%, and 80% identity to Saccharomyces cerevisiae, Schizosaccharomyces pombe, Caenorhabditis elegans, Drosophila melanogaster, and human debranching enzymes, respectively. The mDBR1 cDNA was shown to be functional in an interspecies specific complementation experiment, and an in vitro debranching enzyme assay. Mouse DBR1 could complement the intron accumulation phenotype of a S. cerevisiae dbrl null mutant strain. However, the level of complementation depended on the copy number of the mDBR1 cDNA. The integration of the mDBR1 cDNA in the chromosome of S. pombe also complemented both intron accumulation and slow growth phenotypes of the S. pombe dbr1 knock-out mutant strain.

Striation Mechanism and Triggered Striation in Dielectric Microdischarge Plasma.

Abstract: The striation mechanism of dielectric microdischarges, as in many plasma devices, is extensively explored by collisional kinetic and fluid simulations. Striation in a typical dielectric microdischarge device predominantly occurs near the anode region and is basically governed by the ionization-dominated α-processes, wherein surface and space charges collectively dictate the phenomenon in a complex manner. A novel type of striation has been investigated by us near the cathode region, which is dominated by γ-processes and is driven by the secondary-electron emission mechanism.

Search for the supersymmetric partner of the top quark in pp̅ collisions at √s=1.8 TeV

Abstract: We present a search for the lightest supersymmetric partner of the top quark in proton-antiproton collisions at a center-of-mass energy $\sqrt{s}=1.96\text{ }\text{ }\mathrm{TeV}$. This search was conducted within the framework of the $R$ parity conserving minimal supersymmetric extension of the standard model, assuming the stop decays dominantly to a lepton, a sneutrino, and a bottom quark. We searched for events with two oppositely-charged leptons, at least one jet, and missing transverse energy in a data sample corresponding to an integrated luminosity of $1\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ collected by the Collider Detector at Fermilab experiment. No significant evidence of a stop quark signal was found. Exclusion limits at 95% confidence level in the stop quark versus sneutrino mass plane are set. Stop quark masses up to $180\text{ }\text{ }\mathrm{GeV}/{c}^{2}$ are excluded for sneutrino masses around $45\text{ }\text{ }\mathrm{GeV}/{c}^{2}$, and sneutrino masses up to $116\text{ }\text{ }\mathrm{GeV}/{c}^{2}$ are excluded for stop quark masses around $150\text{ }\text{ }\mathrm{GeV}/{c}^{2}$.

A comprehensive characterization of Hamamatsu 16- and 64-anode PMTs

Abstract: We are reporting preliminary results of studies of R59000-00-M16 and M64 tubes, manufactured by Hamamatsu Photonics, to be employed by the MINOS neutrino experiment. Our tests focused on anode response uniformity, gain, cross-talk, and linearity for light illuminating PMTs through a 1.2 mm diameter fiber.

A New On-line Dead-Time compensation Method Based on Time Delay Control Technique

Abstract: In this paper, an on-line dead-time compensation method based on a time delay control approach is presented. The disturbance voltages caused by the dead time are estimated in an on-line manner by the time delay control without any additional circuits and off-line experimental measurements. And the estimated disturbance voltages are fed to voltage references in order to compensate the dead-time effects. The proposed method is applied to a PM synchronous motor drive system and implemented by using software of a digital signal processor (DSP) TMS320C31. Experiments are carried out for this system and the results well demonstrate the effectiveness of the proposed method.

Quick dialling method by character on communication terminal with touch board

Abstract: A method for performing speed dialing using symbols in a communication terminal having a touch pad is disclosed. The method comprises registering a symbol in association with a phone number; comparing a symbol input by a user from the touch pad with the registered symbol; and reading, when the input symbol is identical to the registered symbol, said phone number registered in associated with the registered symbol and automatically dialing the read phone number. An error message, or a re-input request message, is displayed when the input symbol is not identical to a registered symbol.

A new on-line dead-time compensation method based on time delay control

Abstract: In this paper, an on-line dead-time compensation method based on a time delay control approach is presented. The disturbance voltages caused by the dead time are estimated in an on-line manner by the time delay control without any additional circuits and off-line experimental measurements. The estimated disturbance voltages are fed to voltage references in order to compensate the dead-time effects. The proposed method is applied to a PM synchronous motor drive system and implemented by using software of a digital signal processor (DSP) TMS320C31. Experiments are carried out for this system and the results well demonstrate the effectiveness of the proposed method.

A fast programmable trigger for isolated cluster counting in the BELLE experiment

Abstract: We have developed a fast programmable trigger processor board based on a field programmable gate array and a complex programmable logic device for use in the BELLE experiment. The trigger board accommodates 144 ECL input signals, 2 NIM input signals, 24 ECL output signals, and the VME bus specification. An asynchronous trigger logic for counting isolated clusters is used. We have obtained a trigger latency of 50 ns with full access to input and output signals via a VME interface. The trigger logic can be modified at any time depending on the experimental conditions.