SEARCH FOR PULSED γ-RAY EMISSION FROM GLOBULAR CLUSTER M28

Wu, J. H. K.,Hui, C. Y.,Wu, E. M. H.,Kong, A. K. H.,Huang, R. H. H.,Tam, P. H. T.,Takata, J.,Cheng, K. S. IOP Publishing 2013 ASTROPHYSICAL JOURNAL LETTERS - Vol.765 No.2

<P>Using the data from the Large Area Telescope on board the Fermi Gamma-ray Space Telescope, we have searched for gamma-ray pulsations from the direction of the globular cluster M28 (NGC 6626). We report the discovery of a signal with a frequency consistent with that of the energetic millisecond pulsar (MSP) PSR B1821-24 in M28. A weighted H-test test statistic of 28.8 is attained, which corresponds to a chance probability of similar to 10(-5) (4.3 sigma detection). With a phase-resolved analysis, the pulsed component is found to contribute similar to 25% of the total observed gamma-ray emission from the cluster. However, the unpulsed level provides a constraint for the underlying MSP population and the fundamental plane relations for the scenario of inverse Compton scattering. Follow-up timing observations in radio/X-ray are encouraged to further investigate this periodic signal candidate.</P>

An ANPC based High-Power Medium-Voltage Triple Active Bridge (TAB) DC-DC Converter with Enhanced Modulations

Hui Cao,Feng Guo,Zhuxuan Ma,Liyang Du,Yue Zhao,H. Alan Mantooth 전력전자학회 2023 ICPE(ISPE)논문집 Vol.2023 No.-

A high-power medium-voltage isolated DC-DC converter is proposed aiming at onboard power distribution for the future electric aircraft. The proposed converter is designed using the triple-active-bridge architecture, which consists of an H-bridge on the low voltage side and two active neutral-point-clamped (ANPC) half-bridge in series on the high voltage side. With this configuration, a high voltage step-up ratio can be achieved while using cost-effective low voltage silicon carbide (SiC) devices. A full power prototype is developed to study the design feasibility, where the H-bridge takes an input voltage up to 1 kV and the converter output can reach up to 4 kV. An improved modulation strategy is presented to control the power flow with reduced voltage overshoot across transformer windings. Also, an algorithm is proposed to address the capacitor voltage imbalance. The feasibility of the proposed converter architecture and its modulation scheme are verified using both simulation and experimental studies.

Hospital-based Influenza Morbidity and Mortality (HIMM) Surveillance for A/H7N9 Influenza Virus Infection in Returning Travelers

Song, Joon Young,Noh, Ji Yun,Lee, Jacob,Woo, Heung Jeong,Lee, Jin Soo,Wie, Seong-Heon,Kim, Young Keun,Jeong, Hye Won,Kim, Shin Woo,Lee, Sun Hee,Park, Kyung-Hwa,Kang, Seong Hui,Kee, Sae Yoon,Kim, Tae H KOREAN ACADEMY OF MEDICAL SCIENCE 2018 JOURNAL OF KOREAN MEDICAL SCIENCE Vol.33 No.7

<P>Since 2013, the Hospital-based Influenza Morbidity and Mortality (HIMM) surveillance system began a H7N9 influenza surveillance scheme for returning travelers in addition to pre-existing emergency room (ER)-based influenza-like illness (ILI) surveillance and severe acute respiratory infection (SARI) surveillance. Although limited to eastern China, avian A/H7N9 influenza virus is considered to have the highest pandemic potential among currently circulating influenza viruses. During the study period between October 1st, 2013 and April 30th, 2016, 11 cases presented with ILI within seven days of travel return. These patients visited China, Hong Kong, or neighboring Southeast Asian countries, but none of them visited a livestock market. Seasonal influenza virus (54.5%, 6 among 11) was the most common cause of ILI among returning travelers, and avian A/H7N9 influenza virus was not detected during the study period.</P>

Association of Genetic Variants in Complement Factor H and Factor H-Related Genes with Systemic Lupus Erythematosus Susceptibility

Zhao, Jian,Wu, Hui,Khosravi, Melanie,Cui, Huijuan,Qian, Xiaoxia,Kelly, Jennifer A.,Kaufman, Kenneth M.,Langefeld, Carl D.,Williams, Adrienne H.,Comeau, Mary E.,Ziegler, Julie T.,Marion, Miranda C.,Adl Public Library of Science 2011 PLoS genetics Vol.7 No.5

<▼1><P>Systemic lupus erythematosus (SLE), a complex polygenic autoimmune disease, is associated with increased complement activation. Variants of genes encoding complement regulator factor H (CFH) and five CFH-related proteins (CFHR1-CFHR5) within the chromosome 1q32 locus linked to SLE, have been associated with multiple human diseases and may contribute to dysregulated complement activation predisposing to SLE. We assessed 60 SNPs covering the <I>CFH</I>-<I>CFHRs</I> region for association with SLE in 15,864 case-control subjects derived from four ethnic groups. Significant allelic associations with SLE were detected in European Americans (EA) and African Americans (AA), which could be attributed to an intronic <I>CFH</I> SNP (rs6677604, in intron 11, <I>P</I><SUB>meta</SUB> = 6.6×10<SUP>−8</SUP>, OR = 1.18) and an intergenic SNP between <I>CFHR1</I> and <I>CFHR4</I> (rs16840639, <I>P</I><SUB>meta</SUB> = 2.9×10<SUP>−7</SUP>, OR = 1.17) rather than to previously identified disease-associated <I>CFH</I> exonic SNPs, including I62V, Y402H, A474A, and D936E. In addition, allelic association of rs6677604 with SLE was subsequently confirmed in Asians (AS). Haplotype analysis revealed that the underlying causal variant, tagged by rs6677604 and rs16840639, was localized to a ∼146 kb block extending from intron 9 of <I>CFH</I> to downstream of <I>CFHR1</I>. Within this block, the deletion of <I>CFHR3</I> and <I>CFHR1</I> (<I>CFHR3-1</I>Δ), a likely causal variant measured using multiplex ligation-dependent probe amplification, was tagged by rs6677604 in EA and AS and rs16840639 in AA, respectively. Deduced from genotypic associations of tag SNPs in EA, AA, and AS, homozygous deletion of <I>CFHR3-1</I>Δ (<I>P</I><SUB>meta</SUB> = 3.2×10<SUP>−7</SUP>, OR = 1.47) conferred a higher risk of SLE than heterozygous deletion (<I>P</I><SUB>meta</SUB> = 3.5×10<SUP>−4</SUP>, OR = 1.14). These results suggested that the <I>CFHR3-1</I>Δ deletion within the SLE-associated block, but not the previously described exonic SNPs of <I>CFH</I>, might contribute to the development of SLE in EA, AA, and AS, providing new insights into the role of complement regulators in the pathogenesis of SLE.</P></▼1><▼2><P><B>Author Summary</B></P><P>Systemic lupus erythematosus (SLE) is a complex autoimmune disease, associated with increased complement activation. Previous studies have provided evidence for the presence of SLE susceptibility gene(s) in the chromosome 1q31-32 locus. Within 1q32, genes encoding complement regulator factor H (CFH) and five CFH-related proteins (CFHR1-CFHR5) may contribute to the development of SLE, because genetic variants of these genes impair complement regulation and predispose to various human diseases. In this study, we tested association of genetic variants in the region containing <I>CFH</I> and <I>CFHRs</I> with SLE. We identified genetic variants predisposing to SLE in European American, African American, and Asian populations, which might be attributed to the deletion of <I>CFHR3</I> and <I>CFHR1</I> genes but not previously identified disease-associated exonic variants of <I>CFH</I>. This study provides the first evidence for consistent association between <I>CFH/CFHRs</I> and SLE across multi-ancestral SLE datasets, providing new insights into the role of complement regulators in the pathogenesis of SLE.</P></▼2>

Solvent Electronic Polarization Effects on Na⁺–Na⁺ and Cl^––Cl^– Pair Associations in Aqueous Solution

Choi, Cheol Ho,Re, Suyong,Rashid, Mohammad H. O.,Li, Hui,Feig, Michael,Sugita, Yuji American Chemical Society 2013 The journal of physical chemistry. B, Condensed ma Vol.117 No.31

<P>The formation of like-ion pairs, Na<SUP>+</SUP>–Na<SUP>+</SUP> and Cl<SUP>–</SUP>–Cl<SUP>–</SUP>, in aqueous solution was studied by high-level ab initio methods, classical molecular dynamics (MD), QM/TIP5P, and QM/EFP MD (quantum mechanics/effective fragment potential molecular dynamics). Ab initio calculations on model clusters revealed that the Na<SUP>+</SUP>(H<SUB>2</SUB>O)<SUB><I>n</I></SUB>Na<SUP>+</SUP> (<I>n</I> = 2–4) clusters were significantly more stabilized by bridged waters than the corresponding Cl<SUP>–</SUP>(H<SUB>2</SUB>O)<SUB><I>n</I></SUB>Cl<SUP>–</SUP> clusters. QM/EFP MD simulations in solution also predicted a clear local minimum near 3.6 Å only for the Na<SUP>+</SUP>–Na<SUP>+</SUP> pair, suggesting that Na<SUP>+</SUP>–Na<SUP>+</SUP> pairs may be more likely to form than Cl<SUP>–</SUP>–Cl<SUP>–</SUP> pairs in solution. Analysis of the hydration structures further showed that two-water bridged Na<SUP>+</SUP>–Na<SUP>+</SUP> pairs were dominant at the local minimum. The preferred formation of Na<SUP>+</SUP> like-ion pairs in solution appeared to come from significant short-range effects, in particular, charge delocalization (polarization) between the bridged oxygen p and the vacant valence Na<SUP>+</SUP> orbitals.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpcbfk/2013/jpcbfk.2013.117.issue-31/jp4049346/production/images/medium/jp-2013-049346_0003.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp4049346'>ACS Electronic Supporting Info</A></P>

DISCOVERY OF GAMMA-RAY EMISSION FROM THE SUPERNOVA REMNANT Kes 17 WITH <i>FERMI</i> LARGE AREA TELESCOPE

Wu, J. H. K.,Wu, E. M. H.,Hui, C. Y.,Tam, P. H. T.,Huang, R. H. H.,Kong, A. K. H.,Cheng, K. S. IOP Publishing 2011 ASTROPHYSICAL JOURNAL LETTERS - Vol.740 No.1

<P>We report the discovery of GeV emission at the position of supernova remnant Kes 17 by using the data from the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. Kes 17 can be clearly detected with a significance of similar to 12 sigma in the 1-20 GeV range. Moreover, a number of gamma-ray sources were detected in its vicinity. The gamma-ray spectrum of Kes 17 can be described well by a simple power law with a photon index of Gamma similar to 2.4. Together with the multiwavelength evidence for its interactions with the nearby molecular cloud, the gamma-ray detection suggests that Kes 17 is a candidate acceleration site for cosmic rays.</P>

ORBITAL-PHASE-DEPENDENT γ-RAY EMISSIONS FROM THE BLACK WIDOW PULSAR

Wu, E. M. H.,Takata, J.,Cheng, K. S.,Huang, R. H. H.,Hui, C. Y.,Kong, A. K. H.,Tam, P. H. T.,Wu, J. H. K. IOP Publishing 2012 The Astrophysical journal Vol.761 No.2

<P>We report on evidence for orbital phase dependence of the gamma-ray emission from the PSR B1957+20 black widow system using data from the Fermi Large Area Telescope. We divide an orbital cycle into two regions: one containing the inferior conjunction and the other containing the rest of the orbital cycle. We show that the observed spectra for the different orbital regions are fitted by different functional forms. The spectrum of the orbital region containing the inferior conjunction can be described by a power law with an exponential cutoff (PLE) model, which also gives the best-fit model for the orbital phase without the inferior conjunction, plus an extra component above similar to 2.7 GeV. The emission above 3 GeV in this region is detected with a similar to 7 sigma confidence level. The gamma-ray data above similar to 2.7 GeV are observed to be modulated at the orbital period at the similar to 2.3 sigma level. We anticipate that the PLE component dominant below similar to 2.7 GeV originates from the pulsar magnetosphere. We also show that inverse Compton scattering of the thermal radiation of the companion star off a 'cold' ultrarelativistic pulsar wind can explain the extra component above similar to 2.7 GeV. The black widow pulsar PSR B1957+20 may be a member of a new class of object, in the sense that the system is showing gamma-ray emission with both magnetospheric and pulsar wind origins.</P>

The effect of Reynolds numbers on the steady state aerodynamic force coefficients of the Stonecutters Bridge deck section

Hui, M.C.H.,Zhou, Z.Y.,Chen, A.R.,Xiang, H.F. Techno-Press 2008 Wind and Structures, An International Journal (WAS Vol.11 No.3

In a wind tunnel experiment employing a reduced scale model, Reynolds number (Re) can hardly be respected. Its effects on the aerodynamics of closed-box bridge decks have been the subject of research in recent years. Stonecutters Bridge in Hong Kong is a cable-stayed bridge having an unprecedented central span of 1018m. The issue of Re sensitivity was raised early in the design phase of the deck of Stonecutters Bridge. The objective of this study is to summarise the results of various wind tunnel experiments in order to demonstrate the effect of Re on the steady state aerodynamic force coefficients. The results may provide an insight on the choice of scale for section model experiments in bridge design projects. Computational Fluid Dynamics (CFD) analysis of forces on bridge deck section was also carried out to see how CFD results are compared with experimental results.

Rapid X-Ray Variations of the Geminga Pulsar Wind Nebula

Hui, C. Y.,Lee, Jongsu,Kong, A. K. H.,Tam, P. H. T.,Takata, J.,Cheng, K. S.,Ryu, Dongsu American Astronomical Society 2017 The Astrophysical journal Vol.846 No.2

<P>A recent study by Posselt et al. reported the deepest X-ray investigation of the Geminga pulsar wind nebula (PWN) by using Chandra X-ray Observatory. In comparison with previous studies of this system, a number of new findings have been reported, and we found that these suggest the possible variabilities in various components of this PWN. This motivates us to carry out a dedicated search for the morphological and spectral variations of this complex nebula. We have discovered variabilities on timescales from a few days to a few months from different components of the nebula. The fastest change occurred in the circumstellar environment at a rate of 80% of the speed of light. One of the most spectacular results is the wiggling of a half light-year long tail as an extension of the jet, which is significantly bent by the ram pressure. The jet wiggling occurred at a rate of about 20% of the speed of light. This twisted structure could possibly be a result of a propagating torsional Alfv'en wave. We have also found evidence of spectral hardening along this tail for a period of about nine months.</P>

SEARCHES FOR MILLISECOND PULSAR CANDIDATES AMONG THE UNIDENTIFIED<i>FERMI</i>OBJECTS

Hui, C. Y.,Park, S. M.,Hu, C. P.,Lin, L. C. C.,Li, K. L.,Kong, A. K. H.,Tam, P. H. T.,Takata, J.,Cheng, K. S.,Jin, Ruolan,Yen, T.-C.,Kim, Chunglee IOP Publishing 2015 The Astrophysical journal Vol.809 No.1

<P>Here we report the results of searching millisecond pulsar (MSP) candidates from the Fermi LAT second source catalog (2FGL). Seven unassociated gamma-ray sources in this catalog are identified as promising MSP candidates based on their gamma-ray properties. Through the X-ray analysis, we have detected possible X-ray counterparts, localized to an arcsecond accuracy. We have systematically estimated their X-ray fluxes and compared them with the corresponding gamma-ray fluxes. The X-ray to gamma-ray flux ratios for 2FGL J1653.6-0159 and 2FGL J1946.4-5402 are comparable with the typical value for pulsars. For 2FGL J1625.2-0020, 2FGL J1653.6-0159, and 2FGL J1946.4-5402, their candidate X-ray counterparts are bright enough to perform a detailed spectral and temporal analysis to discriminate their thermal/non-thermal nature and search for the periodic signal. We have also searched for possible optical/IR counterparts at the X-ray positions. For the optical/IR source coincident with the brightest X-ray object associated with 2FGL J1120.0-2204, its spectral energy distribution is comparable with a late-type star. Evidence for the variability has also been found by examining its optical light curve. All the aforementioned 2FGL sources resemble a pulsar in one or more aspects, making them promising targets for follow-up investigations.</P>