Showing papers by "Hyun-Chul Kim published in 2007"

Sparse non-negative matrix factorizations via alternating non-negativity-constrained least squares for microarray data analysis

Abstract: Motivation: Many practical pattern recognition problems require non-negativity constraints. For example, pixels in digital images and chemical concentrations in bioinformatics are non-negative. Sparse non-negative matrix factorizations (NMFs) are useful when the degree of sparseness in the non-negative basis matrix or the non-negative coefficient matrix in an NMF needs to be controlled in approximating high-dimensional data in a lower dimensional space. Results: In this article, we introduce a novel formulation of sparse NMF and show how the new formulation leads to a convergent sparse NMF algorithm via alternating non-negativity-constrained least squares. We apply our sparse NMF algorithm to cancer-class discovery and gene expression data analysis and offer biological analysis of the results obtained. Our experimental results illustrate that the proposed sparse NMF algorithm often achieves better clustering performance with shorter computing time compared to other existing NMF algorithms. Availability: The software is available as supplementary material. Contact:hskim@cc.gatech.edu, hpark@acc.gatech.edu Supplementary information: Supplementary data are available at Bioinformatics online.

Evidence of a broad structure at an invariant mass of 4.32GeV/c2 in the reaction e+e-→π+π-ψ(2S) measured at BABAR

Abstract: The authors measure the cross section for the process e{sup +}e{sup -} {yields} {pi}{sup +}{pi}{sup -}{psi}(2S) from threshold up to 8 GeV center-of-mass energy using events containing initial-state radiation, produced at the PEP-II e{sup +}e{sup -} storage rings The study is based on 298 fb{sup -1} of data recorded with the BABAR detector A structure is observed in the cross-section not far above threshold, near 432 GeV This structure is not compatible with the Y(4260) previously reported by this experiment A single resonance is adequate to describe the cross-section in the low-energy region (< 57 GeV)

Analysis of the quantum numbers J(PC) of the X(3872) particle.

Abstract: The authors present an analysis of angular distributions and correlations of the X(3872) in the exclusive decay mode X(3872) {yields} J/{psi}{pi}{sup +}{pi}{sup -} with J/{psi} {yields} {mu}{sup +}{mu}{sup -}. They use 780 pb{sup -1} of data from p{bar p} collisions at {radical}s = 1.96 TeV collected with the CDF II detector at the Fermilab Tevatron. They derive constraints on spin, parity, and charge conjugation parity of the X(3872) by comparing measured angular distributions of the decay products with predictions for different J{sup PC} hypotheses. The assignments J{sup PC} = 1{sup ++} and 2{sup -+} are the only ones consistent with the data.

Composition dependent crystallography of α''-martensite in Ti-Nb-based β-titanium alloy

Abstract: Composition dependence of crystallographic features of α″-martensite in Ti–Nb-based alloy was systematically examined in Ti–Xmol%Nb–3mol%Al alloy, where X is 10–30. One of the lattice deformation s...

The e+e-→2(π+π-)π0, 2(π+π-)η, K+K-π+π-π0 and K+K-π+π-η cross sections measured with initial-state radiation

Abstract: We study the processes $e^+ e^-\to 2(\pi^+\pi^-)\pi^0\gamma$, $2(\pi^+\pi^-)\eta\gamma$, $K^+ K^-\pi^+\pi^-\pi^0\gamma$ and $K^+ K^-\pi^+\pi^-\eta\gamma$ with the hard photon radiated from the initial state. About 20000, 4300, 5500 and 375 fully reconstructed events, respectively, are selected from 232 fb$^{-1}$ of BaBar data. The invariant mass of the hadronic final state defines the effective $e^+ e^-$ center-of-mass energy, so that the obtained cross sections from the threshold to about 5 GeV can be compared with corresponding direct \epem measurements, currently available only for the $\eta\pi^+\pi^-$ and $\omega\pi^+\pi^-$ submodes of the $e^+ e^-\to 2(\pi^+\pi^-)\pi^0$ channel. Studying the structure of these events, we find contributions from a number of intermediate states, and we extract their cross sections where possible. In particular, we isolate the contribution from $e^+ e^-\to\omega(782)\pi^+\pi^-$ and study the $\omega(1420)$ and $\omega(1650)$ resonances. In the charmonium region, we observe the $J/\psi$ in all these final states and several intermediate states, as well as the $\psi(2S)$ in some modes, and we measure the corresponding branching fractions.

Polarizations of J/ψ and ψ(2S) mesons produced in pp̄ collisions at s=1.96TeV

Abstract: The authors have measured the polarizations of J/{psi} and {psi}(2S) mesons as functions of their transverse momentum p{sub T} when they are produced promptly in the rapidity range |y| < 0.6 with p{sub T} {ge} 5 GeV/c. The analysis is performed using a data sample with an integrated luminosity of about 800 pb{sup -1} collected by the CDF II detector. For both vector mesons, they find that the polarizations become increasingly longitudinal as p{sub T} increases from 5 to 30 GeV/c. These results are compared to the predictions of non-relativistic quantum chromo-dynamics and other contemporary models. The polarizations of J/{psi} and {psi}(2S) mesons from B-hadron decays are also reported.

Direct measurement of antiferromagnetic domain fluctuations

Abstract: Measurements of magnetic noise emanating from ferromagnets owing to domain motion were first carried out nearly 100 years ago, and have underpinned much science and technology. Antiferromagnets, which carry no net external magnetic dipole moment, yet have a periodic arrangement of the electron spins extending over macroscopic distances, should also display magnetic noise. However, this must be sampled at spatial wavelengths of the order of several interatomic spacings, rather than the macroscopic scales characteristic of ferromagnets. Here we present a direct measurement of the fluctuations in the nanometre-scale superstructure of spin- and charge-density waves associated with antiferromagnetism in elemental chromium. The technique used is X-ray photon correlation spectroscopy, where coherent X-ray diffraction produces a speckle pattern that serves as a 'fingerprint' of a particular magnetic domain configuration. The temporal evolution of the patterns corresponds to domain walls advancing and retreating over micrometre distances. This work demonstrates a useful measurement tool for antiferromagnetic domain wall engineering, but also reveals a fundamental finding about spin dynamics in the simplest antiferromagnet: although the domain wall motion is thermally activated at temperatures above 100 K, it is not so at lower temperatures, and indeed has a rate that saturates at a finite value - consistent with quantum fluctuations - on cooling below 40 K.

Measurement of the inclusive jet cross section using the kT algorithm in pp̄ collisions at s=1.96TeV with the CDF II detector

Abstract: The authors report on measurements of the inclusive jet production cross section as a function of the jet transverse momentum in p{bar p} collisions at {radical}s = 1.96 TeV, using the k{sub T} algorithm and a data sample corresponding to 1.0 fb{sup -1} collected with the Collider Detector at Fermilab in Run II. The measurements are carried out in five different jet rapidity regions with |y{sup jet}| < 2.1 and transverse momentum in the range 54 < p{sub T}{sup jet} < 700 GeV/c. Next-to-leading order perturbative QCD predictions are in good agreement with the measured cross sections.

Study of e+e-→ΛΛ̄, ΛΣ̄0, Σ0Σ̄0 using initial state radiation with BABAR

Abstract: We study the e+e- --> Lambda anti-Lambda gamma, Lambda anti-Sigma0 gamma, Sigma0 anti-Sigma0 gamma processes using 230 fb-1 of integrated luminosity collected by the BABAR detector at e+e- center-of-mass energy of 10.58 GeV. From the analysis of the baryon-antibaryon mass spectra the cross sections for e+e- --> Lambda anti-Lambda, Lambda anti-Sigma0, Sigma0 anti-Sigma0 are measured in the dibaryon mass range from threshold up to 3 GeV/c^2. The ratio of electric and magnetic form factors, |G_E/G_M|, is measured for e+e- --> Lambda anti-Lambda, and limits on the relative phase between Lambda form factors are obtained. We also measure the J/psi --> Lambda anti-Lambda, Sigma0 anti-Sigma0 and psi(2S) --> Lambda anti-Lambda branching fractions.

E+e-→K+K-π+π-, K+K-π0π0 and K+K-K+K- cross sections measured with initial-state radiation

Abstract: We study the processes e+e-→K+K-π+π-γ, K+K-π0π0γ and K+K-K+K-γ, where the photon is radiated from the initial state. About 34600, 4400 and 2300 fully reconstructed events, respectively, are selected from 232fb-1 of BABAR data. The invariant mass of the hadronic final state defines the effective e+e- center-of-mass energy, so that the K+K-π+π-γ data can be compared with direct measurements of the e+e-→K+K-π+π- reaction; no direct measurements exist for the e+e-→K+K-π0π0 or e+e-→K+K-K+K- reactions. Studying the structure of these events, we find contributions from a number of intermediate states, and we extract their cross sections where possible. In particular, we isolate the contribution from e+e-→ (1020)f0(980) and study its structure near threshold. In the charmonium region, we observe the J/ψ in all three final states and several intermediate states, as well as the ψ(2S) in some modes, and measure the corresponding branching fractions. We see no signal for the Y(4260) and obtain an upper limit of BY(4260)→ π+π- •ΓeeY<0.4eV at 90% C.L. © 2007 The American Physical Society.

Design of high-efficiency GaN-based light emitting diodes with vertical injection geometry

Abstract: The authors report on the design and fabrication of high-efficiency GaN-based light emitting diodes (LEDs) with vertical-injection geometry. Based on the analyses of LED test patterns fabricated with various n-electrode dimensions, a design rule for vertical LEDs is proposed. It is found that the suppression of the vertical current under n electrodes and the efficient injection of the spreading current across the n layers are essential to fabricate high-efficiency LEDs. Introduction of the current blocking layer along with well-designed branched n electrodes results in a large enhancement of power efficiency by a factor of 1.9, compared with that of reference LEDs.

Wound healing activity of gamma-aminobutyric Acid (GABA) in rats.

Abstract: Gamma-aminobutyric acid (GABA) is a non-protein amino acid. It is well known for its role as an inhibitory neurotransmitter of developing and operating nervous systems in brains. In this study, a novel function of GABA in the healing process of cutaneous wounds was presented regarding anti-inflammation and fibroblast cell proliferation. The cell proliferation activity of GABA was verified through an MTT assay using murine fibroblast NIH3T3 cells. It was observed that GABA significantly inhibited the mRNA expression of iNOS, IL-1beta, and TNF-alpha, in LPS-stimulated RAW 264.7 cells. To evaluate in vivo activity of GABA in wound healing, excisional open wounds were made on the dorsal sides of Sprague-Dawley rats under anesthesia, and the healing of the wounds was apparently assessed. The molecular aspects of the healing process were also investigated by hematoxylineosin staining of the healed skin, displaying the degrees of reepithelialization and linear alignment of the granulation tissue, and immunostaining and RT-PCR analyses of fibroblast growth factor and platelet-derived growth factor, implying extracellular matrix synthesis and remodeling of the skin. The GABA treatment was effective to accelerate the healing process by suppressing inflammation and stimulating reepithelialization, compared with the epidermal growth factor treatment. The healing effect of GABA was remarkable at the early stage of wound healing, which resulted in significant reduction of the whole healing period.

Study of the exclusive initial-state-radiation production of the DD̄ system

Abstract: A study of exclusive production of the D{bar D} system through initial-state radiation is performed in a search for charmonium states, where D = D{sup 0} or D{sup +}. The D{sup 0} mesons are reconstructed in the D{sup 0} {yields} K{sup -}{pi}{sup +}, D{sup 0} {yields} K{sup -}{pi}{sup +}{pi}{sup 0}, and D{sup 0} {yields} K{sup -}{pi}{sup +}{pi}{sup +}{pi}{sup -} decay modes. The D{sup +} is reconstructed through the D{sup +} {yields} K{sup -}{pi}{sup +}{pi}{sup +} decay mode. The analysis makes use of an integrated luminosity of 288.5 fb{sup -1} collected by the BABAR experiment. The D{bar D} mass spectrum shows a clear {psi}(3770) signal. Further structures appear in the 3.9 and 4.1 GeV/c{sup 2} regions. No evidence is found for Y(4260) decays to D{bar D}, implying an upper limit {Beta}(Y(4260) {yields} D{bar D})/{Beta}(Y(4260) {yields} J/{psi}{pi}{sup +}{pi}{sup -}) < 7.6 (95% confidence level).

Observation of the heavy baryons Σb and Σb

Abstract: We report an observation of new bottom baryons produced in proton-antiproton collisions at the Tevatron. Using 1.1 fb^{-1} of data collected by the CDF II detector, we observe four \Lambda_b^0\pi^{\pm} resonances in the fully reconstructed decay mode \Lambda_b^0 \to \Lambda_c^+ \pi^-, where \Lambda_c^+ \to p K^- \pi^+. We interpret these states as the \Sigma_b^{(*)\pm} baryons and measure the following masses: m_{\Sigma_b^+} = 5807.8^{+2.0}_{-2.2}(stat.) \pm 1.7(syst.) MeV/c^2, m_{\Sigma_b^-} = 5815.2 \pm 1.0(stat.) \pm 1.7(syst.) MeV/c^2, and m(\Sigma_b^*) - m(\Sigma_b) = 21.2^{+2.0}_{-1.9}(stat.) ^{+0.4}_{-0.3}(syst.) MeV/c^2.

Method and apparatus for selecting menu in portable terminal

Abstract: Provided is an apparatus and a method for selecting a menu in a portable terminal. The portable terminal includes a first input means that can be rotated stepwise by a predetermined angle, a second input means that can be continuously rotated and pressed, and a controller for providing a menu list corresponding to the rotation direction of the first input means and the number of steps of rotation of the first input means, changing the position of a cursor on the menu list according to the rotation direction and the rotation degree of the second input means, and performing an operation corresponding to a menu in which the cursor is located when the second input means is pressed.

Study of B0→π0π0, B±→π±π0, and B±→K±π0 decays, and isospin analysis of B→ππ decays

Abstract: We present updated measurements of the branching fractions and CP asymmetries for B{sup 0}{yields}{pi}{sup 0}{pi}{sup 0}, B{sup {+-}}{yields}{pi}{sup {+-}}{pi}{sup 0}, and B{sup {+-}}{yields}K{sup {+-}}{pi}{sup 0}. Based on a sample of 383x10{sup 6} {upsilon}(4S){yields}BB decays collected by the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC, we measure B(B{sup 0}{yields}{pi}{sup 0}{pi}{sup 0})=(1.47{+-}0.25{+-}0.12)x10{sup -6}, B(B{sup {+-}}{yields}{pi}{sup {+-}}{pi}{sup 0})=(5.02{+-}0.46{+-}0.29)x10{sup -6}, and B(B{sup {+-}}{yields}K{sup {+-}}{pi}{sup 0})=(13.6{+-}0.6{+-}0.7)x10{sup -6}. We also measure the CP asymmetries C{sub {pi}{sup 0}}{sub {pi}{sup 0}}=-0.49{+-}0.35{+-}0.05, A{sub {pi}{sup {+-}}}{sub {pi}{sup 0}}=0.03{+-}0.08{+-}0.01, and A{sub K{sup {+-}}}{sub {pi}{sup 0}}=0.030{+-}0.039{+-}0.010. Finally, we present bounds on the Cabibbo-Kobayashi-Maskawa angle {alpha} using isospin relations.

Genetic alterations of Wnt signaling pathway-associated genes in hepatocellular carcinoma.

Abstract: Background and Aim: Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide. Recently, abnormal activation of the Wnt pathway has been found to be involved in the carcinogenesis of HCC. However, the relationship between genetic changes in the Wnt pathway–associated genes and its protein expression has not been studied in patients with HCC and cirrhotic nodules. The purpose of this study is to explore the contribution of inappropriate activation of the Wnt pathway in liver carcinogenesis. Methods: Somatic mutation in exons 3–5 of AXIN1 and exon 3 of β-catenin were analyzed by direct sequencing and expression of axin and β-catenin proteins by immunohistochemistry in a series of 36 patients with HCC and cirrhosis. Results: The AXIN1 and β-catenin gene mutations were observed in 25% (9/36) and 2.8% (1/36) of HCCs, respectively. All mutations detected in AXIN1 and β-catenin genes were missense point mutations. Abnormal nuclear expression of β-catenin was observed in 11 of 36 cases of HCCs (30.6%), but not in cirrhotic nodules. Reduced or absent expression of axin was seen in 24 of 36 HCCs (66.7%). The abnormal expression of β-catenin and axin proteins was closely correlated with mutations of AXIN1 and β-catenin (P < 0.0001 and P = 0.008, respectively). Conclusions: These data suggest that mutation of AXIN1 gene is a frequent and late event for HCC associated with cirrhosis, and is correlated significantly with abnormal expression of axin and β-catenin. Therefore, activation of Wnt signaling through AXIN1 rather than β-catenin mutation might play an important role in liver carcinogenesis.

High-Reflectance and Thermally Stable AgCu Alloy p-Type Reflectors for GaN-Based Light-Emitting Diodes

Abstract: We report on the formation of high-quality AgCu alloy p-type reflectors for GaN-based light-emitting diodes (LEDs). Compared with Ag contacts, the AgCu alloy reflectors produce lower specific contact resistance (7.5times10-5 Omegamiddotcm2), higher light reflectance (89.5% at 400 nm), and better thermal stability (absence of interfacial voids), when annealed at 400 degC in N2 : O2(=1:1) ambient. LEDs fabricated with the AgCu reflectors show light output power better than that of LEDs with the Ag reflectors. The ohmic mechanism for the AgCu alloy reflectors is explained in terms of the formation of Ag-Ga solid solution and the presence of Cu-oxide nano-particles at the contact/GaN interface

Measurement of the τ-→K-π0ντ branching fraction

Abstract: A measurement of the tau(-)-> K-pi(0)nu(tau) branching fraction has been made using 230.2 fb(-1) of data recorded by the BABAR detector at the PEP-II e(+)e(-) collider, located at the Stanford Linear Accelerator Center (SLAC), at a center-of-mass energy root s close to 10.58 GeV. We measure B(tau(-)-> K-pi(0)nu(tau))=(0.416 +/- 0.003(stat)+/- 0.018(syst))%.

A 500MHz Random Cycle 1.5ns-Latency, SOI Embedded DRAM Macro Featuring a 3T Micro Sense Amplifier

Abstract: A prototype SOI embedded DRAM macro is developed for high-performance microprocessors and introduces performance-enhancing 3T micro sense amplifier architecture (muSA). The macro was characterized via a test chip fabricated in a 65nm SOI deep-trench DRAM process. Measurements confirm 1.5ns random access time with a 1V supply at 85deg and low voltage operation with a 600mV supply.

Measurement of the hadronic form factor in D0→K-e+νe decays

Abstract: We present a preliminary measurement of the q2 dependence of the D0 --> K- e+ nu_e decay rate. This rate is proportional to the hadronic form factor squared, specified by a single parameter. This is either the mass in the simple pole ansatz m_pole = (1.854 +- 0.016 +- 0.020) GeV/c2 or the scale in the modified pole ansatz alpha_pole = 0.43 +- 0.03 +- 0.04. The first error refers to the statistical, the second to the systematic uncertainty.

User input device and method using fingerprint recognition sensor

Abstract: Disclosed are a user input device and a method for rapidly selecting an operation mode in a mobile terminal having a touch screen input panel and a fingerprint recognition sensor. The user input method includes setting operation modes for at least one fingerprint data and input pattern, each comprised of keys necessary to implement a corresponding operation mode; detecting fingerprint data inputted from the fingerprint recognition sensor, and confirming an operation mode set for the inputted fingerprint data; and displaying an input pattern corresponding to the confirmed operation mode on the touch screen input panel.

Measurement of the B0→π-l+ν form-factor shape and branching fraction, and determination of |Vub| with a loose neutrino reconstruction technique

Abstract: We report the results of a study of the exclusive charmless semileptonic decay, B-0 ->pi(-)center dot(+)nu, undertaken with approximately 227x10(6) BB pairs collected at the Upsilon(4S) resonance with the BABAR detector. The analysis uses events in which the signal B decays are reconstructed with an innovative loose neutrino reconstruction technique. We obtain partial branching fractions in 12 bins of q(2), the momentum transfer squared, from which we extract the f(+)(q(2)) form-factor shape and the total branching fraction B(B-0 ->pi(-)l(+)nu)=(1.46 +/- 0.07(stat)+/- 0.08(syst))x10(-4). Based on a recent unquenched lattice QCD calculation of the form factor in the range q(2)> 16 GeV2, we find the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element vertical bar V-ub vertical bar to be (4.1 +/- 0.2(stat)+/- 0.2(syst)+0.6-0.4(FF))x10(-3), where the last uncertainty is due to the normalization of the form factor.

Clustering Based on Gaussian Processes

Abstract: In this letter, we develop a gaussian process model for clustering. The variances of predictive values in gaussian processes learned from a training data are shown to comprise an estimate of the support of a probability density function. The constructed variance function is then applied to construct a set of contours that enclose the data points, which correspond to cluster boundaries. To perform clustering tasks of the data points, an associated dynamical system is built, and its topological invariant property is investigated. The experimental results show that the proposed method works successfully for clustering problems with arbitrary shapes.

Measurements of current spreading length and design of GaN-based light emitting diodes

Abstract: The authors report on the experimental method to measure the current spreading length in GaN-based light emitting diodes (LEDs) based on a one-dimensional current-distribution model neglecting vertical series resistance of the LEDs. It is clearly shown that the measured current spreading length is in good agreement with the calculated results, exhibiting a strong dependence on the injected current density (or forward bias voltage). LEDs fabricated with hybrid p-type reflectors by using the proposed design rule and measured current spreading lengths show enhancement of the output power by 10% as compared to LEDs made with standard reflectors.

Study of B0→ρ+ρ- decays and constraints on the CKM angle α

Abstract: We present results from an analysis of B0→ρ+ρ- decays using (383.6±4.2)×106 BB pairs collected by the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC. The measurements of the B0→ρ+ρ- branching fraction, longitudinal polarization fraction fL, and the CP-violating parameters Slong and Clong are as follows: B(B0→ρ+ρ-)=(25.5±2.1(stat)-3.9+3.6(syst))×10-6, fL=0.992±0.024(stat)-0.013+0.026(syst), Slong=-0.17±0.20(stat)-0. 06+0.05(syst), Clong=0.01±0.15(stat)±0.06(syst). We determine the unitarity triangle angle α, using an isospin analysis of B→ρρ decays. One of the two solutions, α=[73.1,117.0]° at 68% confidence level, is compatible with standard model-based fits of existing data. Constraints on the unitarity triangle are also evaluated using an SU(3) symmetry-based approach. © 2007 The American Physical Society.

Improved limits on the lepton-flavor violating decays τ-→l-l+l-

Abstract: A search for the neutrinoless, lepton-flavor violating decay of the tau lepton into three charged leptons has been performed using 376 fb^{-1} of data collected at an e^+e^- center-of-mass energy around 10.58 GeV with the BaBar detector at the PEP-II storage rings. In all six decay modes considered, the numbers of events found in data are compatible with the background expectations. Upper limits on the branching fractions are set in the range (4-8) x 10^{-8} at 90% confidence level.

Measurement of decay amplitudes of B→J/ψK*, ψ(2S)K*, and χc1K* with an angular analysis

Abstract: We perform the first three-dimensional measurement of the amplitudes of B→ψ(2S)K* and B→χc1K* decays and update our previous measurement for B→J/ψK*. We use a data sample collected with the BABAR detector at the PEP-II storage ring, corresponding to 232×106 BB pairs. The longitudinal polarization of decays involving a JPC=1++ χc1 meson is found to be larger than that with a 1 - J/ψ or ψ(2S) meson. No direct CP-violating charge asymmetry is observed. © 2007 The American Physical Society.