H M Lee

Publications (510)1282.69 Total impact

• Article: Parameter estimation for compact binary coalescence signals with the first generation gravitational-wave detector network

  the LIGO Scientific Collaboration, the Virgo Collaboration, J. Aasi, J. Abadie, B. P. Abbott, R. Abbott, T. D. Abbott, M. Abernathy, T. Accadia, F. Acernese, [......], M. Yvert, A. Zadrożny, M. Zanolin, J. -P. Zendri, F. Zhang, L. Zhang, C. Zhao, N. Zotov, M. E. Zucker, J. Zweizig
  [show abstract] [hide abstract]
  ABSTRACT: Compact binary systems with neutron stars or black holes are one of the most promising sources for ground-based gravitational wave detectors. Gravitational radiation encodes rich information about source physics; thus parameter estimation and model selection are crucial analysis steps for any detection candidate events. Detailed models of the anticipated waveforms enable inference on several parameters, such as component masses, spins, sky location and distance that are essential for new astrophysical studies of these sources. However, accurate measurements of these parameters and discrimination of models describing the underlying physics are complicated by artifacts in the data, uncertainties in the waveform models and in the calibration of the detectors. Here we report such measurements on a selection of simulated signals added either in hardware or software to the data collected by the two LIGO instruments and the Virgo detector during their most recent joint science run, including a "blind injection" where the signal was not initially revealed to the collaboration. We exemplify the ability to extract information about the source physics on signals that cover the neutron star and black hole parameter space over the individual mass range 1 Msun - 25 Msun and the full range of spin parameters. The cases reported in this study provide a snap-shot of the status of parameter estimation in preparation for the operation of advanced detectors.
  04/2013;
• Article: Search for Gravitational Waves from Binary Black Hole Inspiral, Merger and Ringdown in LIGO-Virgo Data from 2009-2010

  The LIGO Scientific Collaboration, the Virgo Collaboration, J. Aasi, J. Abadie, B. P. Abbott, R. Abbott, T. D. Abbott, M. Abernathy, T. Accadia, F. Acernese, [......], M. Yvert, A. Zadrozny, M. Zanolin, J. -P. Zendri, F. Zhang, L. Zhang, C. Zhao, N. Zotov, M. E. Zucker, J. Zweizig
  [show abstract] [hide abstract]
  ABSTRACT: We report a search for gravitational waves from the inspiral, merger and ringdown of binary black holes (BBH) with total mass between 25 and 100 solar masses, in data taken at the LIGO and Virgo observatories between July 7, 2009 and October 20, 2010. The maximum sensitive distance of the detectors over this period for a (20,20) Msun coalescence was 300 Mpc. No gravitational wave signals were found. We thus report upper limits on the astrophysical coalescence rates of BBH as a function of the component masses for non-spinning components, and also evaluate the dependence of the search sensitivity on component spins aligned with the orbital angular momentum. We find an upper limit at 90% confidence on the coalescence rate of BBH with non-spinning components of mass between 19 and 28 Msun of 3.3 \times 10^-7 mergers /Mpc^3 /yr.
  09/2012;
• Source

  Available from: Reinhard Prix

  Article: Einstein@Home all-sky search for periodic gravitational waves in LIGO S5 data

  J. Aasi, J. Abadie, B. P. Abbott, R. Abbott, T. D. Abbott, M. Abernathy, T. Accadia, F. Acernese, C. Adams, T. Adams, [......], A. Zadrożny, M. Zanolin, J. -P. Zendri, F. Zhang, L. Zhang, C. Zhao, N. Zotov, M. E. Zucker, J. Zweizig, D. P. Anderson
  [show abstract] [hide abstract]
  ABSTRACT: This paper presents results of an all-sky searches for periodic gravitational waves in the frequency range [50, 1190] Hz and with frequency derivative ranges of [-2 x 10^-9, 1.1 x 10^-10] Hz/s for the fifth LIGO science run (S5). The novelty of the search lies in the use of a non-coherent technique based on the Hough-transform to combine the information from coherent searches on timescales of about one day. Because these searches are very computationally intensive, they have been deployed on the Einstein@Home distributed computing project infrastructure. The search presented here is about a factor 3 more sensitive than the previous Einstein@Home search in early S5 LIGO data. The post-processing has left us with eight surviving candidates. We show that deeper follow-up studies rule each of them out. Hence, since no statistically significant gravitational wave signals have been detected, we report upper limits on the intrinsic gravitational wave amplitude h0. For example, in the 0.5 Hz-wide band at 152.5 Hz, we can exclude the presence of signals with h0 greater than 7.6 x 10^-25 with a 90% confidence level.
  07/2012;
• Article: Measurement of Mechanical Properties of Thin Film by Membrane Deflection Test

  Y.-H. Huh, D.-I. Kim, D.-J. Kim, H.-M. Lee, S.-G. Hong, J.-H. Park, C.-D. Kee
  [show abstract] [hide abstract]
  ABSTRACT: Micro-tensile properties of Au thin films were measured using a membrane deflection testing system. During the membrane deflection test, the deflection of the film was measured by an out-of-plane electronic speckle pattern interferometric (ESPI) system. From the measurement, the tensile loads and strains exerted on the membrane film during the deflection of the film could be determined. Quantitative analysis of the phase maps of the ESPI speckle patterns corresponding to the respective different deflection levels provided the deflection distribution along the testing section of the film. Test pieces were fabricated by electromachining process using 0.5 and 1. 0μm thick Au films which were deposited on the silicon wafer by sputtering technique. Tensile properties, including elastic modulus, yield and tensile strength, were evaluated in the tensile stress-strain curve determined from the load-deflection relation. These properties were compared to those obtained from the micro-tensile tests. It was found that the yield and tensile strengths obtained from the deflection tests were lesser than those from the micro-tensile tests. Furthermore, the thickness effect, showing the increasing tendency of yield strength with decreasing thickness, was experimentally examined. KeywordsAu thin film-Out-of-plane ESPI-Membrane deflection test-Micro-tensile test-Mechanical properties
  Experimental Mechanics 05/2012; 50(4):429-435. · 1.52 Impact Factor
• Source

  Available from: Alexander S Krylov

  Article: Resonant raman scattering and dispersion of polar optical and acoustic phonons in hexagonal InN

  V. Yu. Davydov, A. A. Klochikhin, A. N. Smirnov, I. Yu. Strashkova, A. S. Krylov, Hai Lu, William J. Schaff, H. -M. Lee, Y. -L. Hong, S. Gwo
  [show abstract] [hide abstract]
  ABSTRACT: It is shown that a study of the dependence of impurity-related resonant first-order Raman scattering on the frequency of excitation light makes it possible to observe the dispersion of polar optical and acoustic branches of vibrational spectrum in hexagonal InN within a wide range of wave vectors. It is established that the wave vectors of excited phonons are uniquely related to the energy of excitation photon. Frequencies of longitudinal optical phonons E1(LO) and A1(LO) in hexagonal InN were measured in the range of excitation-photon energies from 2.81 to 1.17 eV and the frequencies of longitudinal acoustic phonons were measured in the range 2.81–1.83 eV of excitation-photon energies. The obtained dependences made it possible to extrapolate the dispersion of phonons A1(LO) and E1(LO) to as far as the point Γ in the Brillouin zone and estimate the center-band energies of these phonons (these energies have not been uniquely determined so far).
  Semiconductors 05/2012; 44(2):161-170. · 0.63 Impact Factor
• Article: Direct analysis of clomipramine in human plasma by microbore high performance liquid chromatography with column-switching

  H. M. Lee, C. K. Jeong, S. J. Choi, B. M. Yoon, D. H. Na, K. C. Lee, H. S. Lee
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  ABSTRACT: An automated microbore, liquid chromatographic method with column-switching was developed for the determination of clomipramine from human plasma samples. After direct injection of samples (60 μL), plasma proteins and clomipramine were separated in size-exclusion mode using 20% acetonitrile in 20 mM phosphate buffer (pH 7.0) on Capcell Pak MF Ph-1 precolumn (10×4 mm I.D.). By valve switching, a fraction containing clomipramine was directed to an intermediate column for subsequent main separation on a microbore C18 column (250×1.5 mm I.D.) using 50% acetonitrile in 20 mM phosphate buffer (pH 2.5) at 0.1 mL min−1. The method was advantageous for rapidity (total analysis time: 15 min), reproducibility (C.V.<4.8%), and increased sensitivity (1 ng mL−1). The linearity of response was good (r 2≥0.999) over the concentration range 1–250 ng mL−1.
  Chromatographia 04/2012; 51(5):353-356. · 1.20 Impact Factor
• Article: Antipsychotic treatment in older schizophrenia patients with extrapyramidal side effects in Asia (2001 - 2009).

  Yu-Tao Xiang, Julie Kreyenbuhl, Faith B Dickerson, Gabor S Ungvari, Chuanâ Yue Wang, Tian-Mei Si, Edwin H M Lee, Helen F K Chiu, Kelly Y C Lai, Yan-Ling He, [......], Eeâ Heok Kua, Senta Fujii, Kang Sim, Michael K H Yong, Jitendra K Trivedi, Eunâ Kee Chung, Pichet Udomratn, Kok-Yoon Chee, Norman Sartorius, Naotaka Shinfuku
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  ABSTRACT: This study surveyed the prescribing patterns of antipsychotic medications in Asian older schizophrenia patients with extrapyramidal side effects (EPS) during the period between 2001 and 2009. Information on 848 hospitalized patients with schizophrenia aged 60 or older was extracted from the database of the Research on Asian Psychotropic Prescription Patterns (REAP) study (2001 - 2009). Data from those patients with reported EPS from 8 Asian countries and territories including China, Hong Kong, Japan, Korea, Singapore, Taiwan, India and Malaysia were analyzed. The cross-sectional data of sociodemographic and clinical characteristics and antipsychotic prescriptions were collected using a standardized protocol and data collection procedure. Of the 309/848 (36%) patients suffering from EPS, 210 patients (210/309; 68.0%) received at least one type of first generation antipsychotic (FGA), and 99 (99/309; 32.0%) received second generation antipsychotics (SGAs) only. Of SGAs prescribed in patients with EPS, risperidone was the most commonly used (100/309; 32.4%) followed by olanzapine (33/309; 10.7%) and quetiapine (25/309; 8.1%). FGAs were frequently used in Asian older schizophrenia patients with EPS. Considering the potential adverse effects of FGAs on existing EPS, the reasons for the frequent use of FGAs need to be urgently identified.
  International journal of clinical pharmacology and therapeutics 04/2012; 50(7):500-4. · 1.18 Impact Factor
• Article: Implementation and testing of the first prompt search for gravitational wave transients with electromagnetic counterparts

  LIGO Scientific Collaboration, Virgo Collaboration, J. Abadie, B. P. Abbott, R. Abbott, T. D. Abbott, M. Abernathy, T. Accadia, F. Acernese, C. Adams, [......], R. Fender, N. Gehrels, A. Klotz, E. O. Ofek, M. Smith, M. Sokolowski, B. W. Stappers, I. Steele, J. Swinbank, R. A. M. J. Wijeres
  [show abstract] [hide abstract]
  ABSTRACT: Aims: A transient astrophysical event observed in both gravitational wave (GW) and electromagnetic (EM) channels would yield rich scientific rewards. A first program initiating EM follow-ups to possible transient GW events has been developed and exercised by the LIGO and Virgo community in association with several partners. In this paper, we describe and evaluate the methods used to promptly identify and localize GW event candidates and to request images of targeted sky locations. Methods: During two observing periods (Dec. 17, 2009 to Jan. 8, 2010 and Sep. 2 to Oct. 20, 2010), a low-latency analysis pipeline was used to identify GW event candidates and to reconstruct maps of possible sky locations. A catalog of nearby galaxies and Milky Way globular clusters was used to select the most promising sky positions to be imaged, and this directional information was delivered to EM observatories with time lags of about thirty minutes. A Monte Carlo simulation has been used to evaluate the low-latency GW pipeline's ability to reconstruct source positions correctly. Results: For signals near the detection threshold, our low-latency algorithms often localized simulated GW burst signals to tens of square degrees, while neutron star/neutron star inspirals and neutron star/black hole inspirals were localized to a few hundred square degrees. Localization precision improves for moderately stronger signals. The correct sky location of signals well above threshold and originating from nearby galaxies may be observed with ~50% or better probability with a few pointings of wide-field telescopes.
  Astronomy and Astrophysics 03/2012; 539:124. · 4.59 Impact Factor
• Article: Implementation and testing of the first prompt search for gravitational wave transients with electromagnetic counterparts

  LIGO Scientific Collaboration, Virgo Collaboration, J. Abadie, B. P. Abbott, R. Abbott, T. D. Abbott, M. Abernathy, T. Accadia, F. Acernese, C. Adams, [......], R. Fender, N. Gehrels, A. Klotz, E. O. Ofek, M. Smith, M. Sokolowski, B. W. Stappers, I. Steele, J. Swinbank, R. A. M. J. Wijeres
  [show abstract] [hide abstract]
  ABSTRACT: Aims: A transient astrophysical event observed in both gravitational wave (GW) and electromagnetic (EM) channels would yield rich scientific rewards. A first program initiating EM follow-ups to possible transient GW events has been developed and exercised by the LIGO and Virgo community in association with several partners. In this paper, we describe and evaluate the methods used to promptly identify and localize GW event candidates and to request images of targeted sky locations. Methods: During two observing periods (Dec. 17, 2009 to Jan. 8, 2010 and Sep. 2 to Oct. 20, 2010), a low-latency analysis pipeline was used to identify GW event candidates and to reconstruct maps of possible sky locations. A catalog of nearby galaxies and Milky Way globular clusters was used to select the most promising sky positions to be imaged, and this directional information was delivered to EM observatories with time lags of about thirty minutes. A Monte Carlo simulation has been used to evaluate the low-latency GW pipeline's ability to reconstruct source positions correctly. Results: For signals near the detection threshold, our low-latency algorithms often localized simulated GW burst signals to tens of square degrees, while neutron star/neutron star inspirals and neutron star/black hole inspirals were localized to a few hundred square degrees. Localization precision improves for moderately stronger signals. The correct sky location of signals well above threshold and originating from nearby galaxies may be observed with ~50% or better probability with a few pointings of wide-field telescopes.
  Astronomy and Astrophysics 03/2012; 539:124. · 4.59 Impact Factor
• Article: α-Lipoic acid regulates lipid metabolism through induction of sirtuin 1 (SIRT1) and activation of AMP-activated protein kinase.

  W-L Chen, C-H Kang, S-G Wang, H-M Lee
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  ABSTRACT: Sirtuin 1 (SIRT1) is a longevity-associated protein, which regulates energy metabolism and lifespan in response to nutrient deprivation. It has been proposed to be a therapeutic target for obesity and metabolic syndrome. We investigated whether α-lipoic acid (ALA) exerts a lipid-lowering effect through regulation of SIRT1 activation and production in C(2)C(12) myotubes. ALA-stimulated AMP-activated protein kinase (AMPK), acetyl-CoA carboxylase (ACC), adipose triacylglycerol lipase (ATGL) and fatty acid synthase (FAS) production, as well as intracellular triacylglycerol accumulation and fatty acid β-oxidation were analysed in the absence or presence of a SIRT1 inhibitor (nicotinamide), SIRT1 small interfering (si) RNA and an AMPK inhibitor (compound C) in C(2)C(12) myotubes. Mice with streptozotocin/nicotinamide-induced diabetes and db/db mice fed on a high-fat diet were used to study the ALA-mediated lipid-lowering effects in vivo. ALA increased the NAD(+)/NADH ratio to enhance SIRT1 activity and production in C(2)C(12) myotubes. ALA subsequently increased AMPK and ACC phosphorylation, leading to increased palmitate β-oxidation and decreased intracellular triacylglycerol accumulation in C(2)C(12) myotubes. In cells treated with nicotinamide or transfected with SIRT1 siRNA, ALA-mediated AMPK/ACC phosphorylation, intracellular triacylglycerol accumulation and palmitate β-oxidation were reduced, suggesting that SIRT1 is an upstream regulator of AMPK. ALA increased ATGL and suppressed FAS protein production in C(2)C(12) myotubes. Oral administration of ALA in diabetic mice fed on a high-fat diet and db/db mice dramatically reduced the body weight and visceral fat content. ALA activates both SIRT1 and AMPK, which leads to lipid-lowering effects in vitro and in vivo. These findings suggest that ALA may have beneficial effects in the treatment of dyslipidaemia and obesity.
  Diabetologia 03/2012; 55(6):1824-35. · 6.81 Impact Factor
• Source

  Available from: Dumitru Ghilencea

  Article: Tuning supersymmetric models at the LHC: A comparative analysis at two-loop level

  D. M. Ghilencea, H. M. Lee, M. Park
  [show abstract] [hide abstract]
  ABSTRACT: We provide a comparative study of the fine tuning amount (Delta) at the two-loop leading log level in supersymmetric models commonly used in SUSY searches at the LHC. These are the constrained MSSM (CMSSM), non-universal Higgs masses models (NUHM1, NUHM2), non-universal gaugino masses model (NUGM) and GUT related gaugino masses models (NUGMd). Two definitions of the fine tuning are used, the first (Delta_{max}) measures maximal fine-tuning wrt individual parameters while the second (Delta_q) adds their contribution in "quadrature". As a direct result of two theoretical constraints (the EW minimum conditions), fine tuning (Delta_q) emerges as a suppressing factor (effective prior) of the averaged likelihood (under the priors), under the integral of the global probability of measuring the data (Bayesian evidence p(D)). For each model, there is little difference between Delta_q, Delta_{max} in the region allowed by the data, with similar behaviour as functions of the Higgs, gluino, stop mass or SUSY scale (m_{susy}=(m_{\tilde t_1} m_{\tilde t_2})^{1/2}) or dark matter and g-2 constraints. The analysis has the advantage that by replacing any of these mass scales or constraints by their latest bounds one easily infers for each model the value of Delta_q, Delta_{max} or vice versa. For all models, minimal fine tuning is achieved for M_{higgs} near 115 GeV with a Delta_q\approx Delta_{max}\approx 10 to 100 depending on the model, and in the CMSSM this is actually a global minimum. Due to a strong ($\approx$ exponential) dependence of Delta on M_{higgs}, for a Higgs mass near 125 GeV, the above values of Delta_q\approx Delta_{max} increase to between 500 and 1000. Possible corrections to these values are briefly discussed.
  03/2012;
• Source

  Available from: Giancarlo Cella

  Article: All-sky search for gravitational-wave bursts in the second joint LIGO-Virgo run

  the LIGO Scientific Collaboration, the Virgo Collaboration, J. Abadie, B. P. Abbott, R. Abbott, T. D. Abbott, M. Abernathy, T. Accadia, F. Acernese, C. Adams, [......], A. Zadrozny, M. Zanolin, J. -P. Zendri, F. Zhang, L. Zhang, W. Zhang, C. Zhao, N. Zotov, M. E. Zucker, J. Zweizig
  [show abstract] [hide abstract]
  ABSTRACT: We present results from a search for gravitational-wave bursts in the data collected by the LIGO and Virgo detectors between July 7, 2009 and October 20, 2010: data are analyzed when at least two of the three LIGO-Virgo detectors are in coincident operation, with a total observation time of 207 days. The analysis searches for transients of duration < 1 s over the frequency band 64-5000 Hz, without other assumptions on the signal waveform, polarization, direction or occurrence time. All identified events are consistent with the expected accidental background. We set frequentist upper limits on the rate of gravitational-wave bursts by combining this search with the previous LIGO-Virgo search on the data collected between November 2005 and October 2007. The upper limit on the rate of strong gravitational-wave bursts at the Earth is 1.3 events per year at 90% confidence. We also present upper limits on source rate density per year and Mpc^3 for sample populations of standard-candle sources. As in the previous joint run, typical sensitivities of the search in terms of the root-sum-squared strain amplitude for these waveforms lie in the range 5 10^-22 Hz^-1/2 to 1 10^-20 Hz^-1/2. The combination of the two joint runs entails the most sensitive all-sky search for generic gravitational-wave bursts and synthesizes the results achieved by the initial generation of interferometric detectors.
  02/2012;
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  Available from: Giancarlo Cella

  Article: Search for Gravitational Waves from Intermediate Mass Binary Black Holes

  the LIGO Scientific Collaboration, the Virgo Collaboration, J. Abadie, B. P. Abbott, R. Abbott, T. D. Abbott, M. Abernathy, T. Accadia, F. Acernese, C. Adams, [......], A. Zadrozny, M. Zanolin, J. -P. Zendri, F. Zhang, L. Zhang, W. Zhang, C. Zhao, N. Zotov, M. E. Zucker, J. Zweizig
  [show abstract] [hide abstract]
  ABSTRACT: We present the results of a weakly modeled burst search for gravitational waves from mergers of non-spinning intermediate mass black holes (IMBH) in the total mass range 100--450 solar masses and with the component mass ratios between 1:1 and 4:1. The search was conducted on data collected by the LIGO and Virgo detectors between November of 2005 and October of 2007. No plausible signals were observed by the search which constrains the astrophysical rates of the IMBH mergers as a function of the component masses. In the most efficiently detected bin centered on 88+88 solar masses, for non-spinning sources, the rate density upper limit is 0.13 per Mpc^3 per Myr at the 90% confidence level.
  01/2012;
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  Available from: arxiv.org

  Article: Measurement Limits to $^{134} $ Cs Concentration in Soil

  J K Ahn, J S Kim, H M Lee, H Kim, T H Kim, J N Park, Y S Kang, H S Lee, S J Kim, J Y Park, S Y Ryu, H.-Ch Kim, W G Kang, S K Kim
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  ABSTRACT: We investigate the caesium concentrations in soils in mountain areas near Gori nuclear power plant in Korea, focusing on the measurement limits to the 134 Cs. In order to lower the minimum detectable amount (MDA) of activity for the 134 Cs, we have used the ammonium molybdophosphase (AMP) precipitation method to get rid of the 40 K existing in natural radioactivity, which reduces the MDA activity about ten times smaller than those without the AMP precipitation method. The MDA results for the 134 Cs were found to be in the range between 0.015 and 0.044 Bq/kg-dry weight. In order to diminish the background, we also have measured a part of the soil samples in Yangyang, a small town in the east coast of Korea. However, it turns out that in order to detect the 134 Cs in the samples the MDA should be reduced to the level of mBq/kg-dry weight.
  01/2012;
• Article: Epigenetic regulation of myofibroblast differentiation and extracellular matrix production in nasal polyp-derived fibroblasts.

  J-S Cho, Y-M Moon, I-H Park, J-Y Um, J-H Moon, S-J Park, S H Lee, H J Kang, H-M Lee
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  ABSTRACT: Nasal polyposis is a multi-factorial disease associated with chronic inflammatory condition of the paranasal sinuses. Myofibroblast differentiation and extracellular matrix (ECM) accumulation are involved in the pathogenesis of nasal polyposis. The aim of this study was to study the effect of trichostatin A (TSA), a histone deacetylase (HDAC) inhibitor, on transforming growth factor (TGF)-β1-induced myofibroblast differentiation and ECM accumulation in nasal polyp-derived fibroblasts (NPDFs). Nasal polyp-derived fibroblasts were isolated from nasal polyps of patients who have chronic rhinosinusitis with nasal polyp. TSA was treated in TGF-β1-induced NPDFs. Expression levels of HDAC2, α-smooth muscle actin (SMA), TGF-β1, collagen type I, acetylated Histone H3, acetylated Histone H4, phosphorylated Smad2/3 and Smad7 were determined by RT-PCR, western blot and/or immunofluorescent staining. The total collagen amount production was analysed by Sircol soluble collagen assay and contractile activity was measured by collagen gel contraction assay. HDAC2 inhibition by TSA or HDAC2 silencing was established by RT-PCR and western blot. The epigenetic effect on α-SMA gene inactivation was examined by chromatin immunoprecipitation assay. Proliferation was determined by Ki67-positive cell staining and cytotoxicity was assessed by 3-(4,5- dimethylthiazol-2yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. The expression levels of HDAC2, α-SMA and TGF-β1 were increased in nasal polyp tissues compared to normal inferior turbinate tissues. TSA and HDAC2 silencing inhibited expression levels α-SMA, collagen and HDAC2. TSA induced hyperacetylation of histone and suppressed opening of α-SMA gene promoter in TGF-β1-induced NPDFs. TSA inhibited TGF-β1-induced Smad 2/3 and rescued TGF-β1-suppressed Smad7 signalling pathway. Finally, TSA blocked proliferation in TGF-β1-induced NPDFs and has no cytotoxic effect in NPDFs. These results suggest that HDAC inhibition is associated with myofibroblast differentiation and extracelluar matrix accumulation in nasal polyposis. TSA may be useful as an inhibitor of nasal polyp growth, and thus has potential to be used as a novel treatment option for nasal polyposis.
  Clinical & Experimental Allergy 01/2012; 42(6):872-82. · 5.03 Impact Factor
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  Available from: Glenn J. White

  Article: The AKARI NEP-Deep survey: a mid-infrared source catalogue

  T Takagi, H. Matsuhara, T Goto, H. Hanami, M. Im, T Ishigaki, H M Lee, M. Malkan, Y Ohyama, S. Oyabu, C. P. Pearson, S. Serjeant, T Wada, G. J. White
  [show abstract] [hide abstract]
  ABSTRACT: We present a new catalogue of mid-IR sources using the AKARI NEP-Deep survey. The InfraRed Camera (IRC) onboard AKARI has a comprehensive mid-IR wavelength coverage with 9 photometric bands at 2 - 24 micron. We utilized all of these bands to cover a nearly circular area adjacent to the North Ecliptic Pole (NEP). We designed the catalogue to include most of sources detected in 7, 9, 11, 15 and 18 micron bands, and found 7284 sources in a 0.67 deg^2 area. From our simulations, we estimate that the catalogue is ~80 per cent complete to 200 micro Jy at 15 - 18 micron, and ~10 per cent of sources are missed, owing to source blending. Star-galaxy separation is conducted using only AKARI photometry, as a result of which 10 per cent of catalogued sources are found to be stars. The number counts at 11, 15, 18, and 24 micron are presented for both stars and galaxies. A drastic increase in the source density is found in between 11 and 15 micron at the flux level of ~300 micro Jy. This is likely due to the redshifted PAH emission at 8 micron, given our rough estimate of redshifts from an AKARI colour-colour plot. Along with the mid-IR source catalogue, we present optical-NIR photometry for sources falling inside a Subaru/Sprime-cam image covering part of the AKARI NEP-Deep field, which is deep enough to detect most of AKARI mid-IR sources, and useful to study optical characteristics of a complete mid-IR source sample.
  01/2012;
• Article: Large-Scale Synthesis and CO Oxidation Study of FeCr Alloy Supported Pt Nanocatalyst by Electrical Wire Explosion Process

  J.Y. Yun, A.S. Reddy, S. Yang, H.J. Kim, H.Y. Koo, H.M. Lee, C.H. Jung, K. Qadir, S. Kim, J.Y. Park
  Catalysis letters. 01/2012;
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  Available from: Giancarlo Cella

  Article: Upper limits on a stochastic gravitational-wave background using LIGO and Virgo interferometers at 600-1000 Hz

  J. Abadie, B. P. Abbott, R. Abbott, T. D. Abbott, M. Abernathy, T. Accadia, F. Acernese, C. Adams, R. Adhikari, C. Affeldt, [......], A. Zadroźny, M. Zanolin, J. -P. Zendri, F. Zhang, L. Zhang, W. Zhang, C. Zhao, N. Zotov, M. E. Zucker, J. Zweizig
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  ABSTRACT: A stochastic background of gravitational waves is expected to arise from a superposition of many incoherent sources of gravitational waves, of either cosmological or astrophysical origin. This background is a target for the current generation of ground-based detectors. In this article we present the first joint search for a stochastic background using data from the LIGO and Virgo interferometers. In a frequency band of 600-1000 Hz, we obtained a 95% upper limit on the amplitude of $\Omega_{\rm GW}(f) = \Omega_3 (f/900 \mathrm{Hz})^3$, of $\Omega_3 < 0.33$, assuming a value of the Hubble parameter of $h_{100}=0.72$. These new limits are a factor of seven better than the previous best in this frequency band.
  12/2011;
• Article: Mg-induced terahertz transparency of indium nitride films

  H. Ahn, J.-W. Chia, H.-M. Lee, Y.-L. Hong, S. Gwo
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  ABSTRACT: Terahertz time-domain spectroscopy (THz-TDS) has been used to investigate electrical properties of Mg-doped indium nitride (InN). Mg-doping in InN was found to significantly increase terahertz transmittance. THz-TDS analysis based on the Drude model shows that this high transmittance from Mg-doped InN is mainly due to the reduction in mobility associated with ionized dopants. The Hall-effect-measured mobility is typically lower than the THz-TDS-measured mobility for the same samples. However, the results of both measurements have the same slope in the linear relation between mobility and density. By introducing a compensation ratio of ∼0.2, an excellent agreement in mobilities of two methods is obtained.
  Applied Physics Letters 12/2011; 99(23):232117-232117-3. · 3.84 Impact Factor
• Article: Investigation of Electronic Transport in Lateral NiFe/Al O /p-Si/Al O /NiFe Junctions

  Y.C. Lee, C.W. Lin, H.M. Lee, L. Horng, J.C. Wu
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  ABSTRACT: A series of lateral junctions consisting of NiFe/Al₂O₃/p-Si/Al₂O₃/NiFe have been investigated for the understanding of manipulating the electronic spin in semiconducting channel. Devices with various conducting channel lengths between two electrodes were fabricated using a top-down technique. An ion beam sputtering was used for the required film stack and an electron beam lithography in combination with ion beam etching technique were adopted for patterning. The current-voltage measurements reveal a remarkable phenomenon of current enhancement, indicating a formation of the interface state in such devices. This transport behavior associated with trapping assistance has also been demonstrated with a fitting based on Poole-Frenkel effect. The results also show that a transition from trapping assisted process to direct tunneling process occurs when the semiconducting channel length is below 1 μm. In addition, the current enhancement may be suppressed with increasing the thickness of the oxide layer.
  IEEE Transactions on Magnetics 11/2011; · 1.36 Impact Factor