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S H Chang

Publications and source records attributed to S H Chang.

At least 37 records · Page 2Linked to original sources
PubMed2006

Measurement of the dipion mass spectrum in decays.

We measure the dipion mass spectrum in X(3872)--> J/psipi(+) pi(-) decays using 360 pb(-1) of pp collisions at square root s= 1.96 TeV collected with the CDF II detector. The spectrum is fit with predictions for odd C-parity ((3)S(1), (1)P(1), and (3)D(J)) charmonia decaying to J/psipi(+) pi(-), as well as even C-parity states in which the pions are from rho(0) decay. The latter case also encompasses exotic interpretations, such as a D(0)D(*0) molecule. Only the (3)S(1) and J/psirho hypotheses are compatible with our data. Since (3)S(1) is untenable on other grounds, decay via J/psirho is favored, which implies C= +1 for the X(3872). Models for J/psi - rho different angular momenta L are considered. Flexibility in the models, especially the introduction of rho - omega interference, enables good descriptions of our data for both L = 0 and 1.

Journal Article↗
PubMed2006

Search for Higgs bosons decaying to bb and produced in association with W bosons in pp collisions at square root of s = 1.96 TeV.

We present a search for Higgs bosons decaying into bb and produced in association with W bosons in pp collisions at square root of s = 1.96 TeV. This search uses 320 pb(-1) of the data set accumulated by the upgraded Collider Detector at Fermilab. Events are selected that have a high-transverse momentum electron or muon, missing transverse energy, and two jets, at least one of which is consistent with the hadronization of a b quark. Both the number of events and the dijet mass distribution are consistent with standard model background expectations, and we set 95% confidence level upper limits on the production cross section times branching ratio for the Higgs boson or any new particle with similar decay kinematics. These upper limits range from 10 pb for mH = 110 GeV/c2 to 3 pb for mH = 150 GeV/c2.

Journal Article↗
PubMed2006

Evidence for the exclusive decay B(c)+- --> J/psi pi+- and measurement of the mass of the B(c)+- meson.

We report the first evidence for a fully reconstructed decay mode of the B(c)+- meson in the channel B(c)+- --> J/psi pi+-, with J/psi --> mu+ mu-. The analysis is based on an integrated luminosity of 360 pb(-1) in pp collisions at 1.96 TeV center of mass energy collected by the Collider Detector at Fermilab. We observe 14.6 +/- 4.6 signal events with a background of 7.1 +/- 0.9 events, and a fit to the J/psi pi+-mass spectrum yields a B(c)+- mass of 6285.7 +/- 5.3(stat) +/- 1.2(syst) MeV/c2. The probability of a peak of this magnitude occurring by random fluctuation in the search region is estimated as 0.012%.

Journal Article↗
PubMed2006

Search for charged Higgs bosons from top quark decays in pp collisions at square root s=1.96 TeV.

We report the results of a search for a charged Higgs boson in the decays of top quarks produced in pp collisions at a center-of-mass energy of 1.96 TeV. We use a data sample corresponding to an integrated luminosity of 193 pb-1 collected by the upgraded Collider Detector at Fermilab. No evidence for charged Higgs production is found, allowing 95% C.L. upper limits to be placed on BR(t-->H+b) for different charged Higgs decay scenarios. In addition, we present in the minimal supersymmetric standard model (mH+/-, tanbeta) plane the first exclusion regions with radiative and Yukawa coupling corrections.

Journal Article↗
PubMed2006

Precision top-quark mass measurement in the lepton+jets topology in p p collisions at square root s=1.96 TeV.

We report two measurements of the top-quark mass M(top) using the CDF II detector at the Fermilab Tevatron in a 318 pb(-1) data sample of tt events in the lepton+jets final state. One method uses an event-based likelihood technique resulting in M(top) = 173.2(-2.4)(+2.6)(stat) +/- 3.2(syst) GeV/c2 or 173.2(-4.0)(+4.1) GeV/c2. The second method reconstructs a top-quark mass in each event using the measured invariant mass of the hadronically decaying W boson to constrain the jet energy scale to obtain a value for M(top)of 173.5(-3.6)(+3.7)(stat) +/- 1.3(syst) GeV/c2 or 173.5(-3.8)(+3.9) GeV/c2 . We take the latter, which is more precise, as our result.

Journal Article↗
PubMed2006

Search for neutral Higgs bosons of the minimal supersymmetric standard model decaying to tau pairs in pp collisions at square root of s = 1.96 TeV.

We present a search for neutral supersymmetric Higgs bosons decaying to tau pairs produced in pp collisions at square root of s = 1.96 TeV. The data, corresponding to 310 pb(-1) integrated luminosity, were collected with the Collider Detector at Fermilab in run II of the Tevatron. No significant excess above the standard model backgrounds is observed. We set exclusion limits on the production cross section times branching fraction to tau pairs for Higgs boson masses in the range from 90 to 250 GeV/c2.

Journal Article↗
PubMed2005

Search for new high-mass particles decaying to Lepton pairs in pp collisions at square root s = 1.96 TeV.

A search for new particles (X) that decay to electron or muon pairs has been performed using approximately 200 pb(-1) of pp collision data at (square root) s = 1.96 TeV collected by the CDF II experiment at the Fermilab Tevatron. Limits on sigma(pp --> X)BR (X --> ll) are presented as a function of dilepton invariant mass m(ll) > 150 GeV/c2, for different spin hypotheses (0, 1, or 2). The limits are approximately 25 fb for m(ll) > GeV/c2. Lower mass bounds for X from representative models beyond the standard model including heavy neutral gauge bosons are presented.

Journal Article↗
PubMed2005

Search for [corrected] B0(s) --> mu+ mu- and B0(d) [corrected] --> mu + mu- decays in pp collisions with CDF II.

We report on a search for B0(s) --> mu+ mu- and B0(d) --> mu + mu- decays in pp collisions at square root(s) = 1.96 TeV using 364 pb(-1) of data collected by the CDF II detector at the Fermilab Tevatron Collider. After applying all selection requirements, we observe no candidates inside the B0(s) or B0(d) mass windows. The resulting upper limits on the branching fractions are B(B0(s) --> mu+ mu-) < 1.5 x 10(-7) and B(B0(d) --> mu+ mu-) < 3.9 x 10(-8) at 90% confidence level.

Journal Article↗
PubMed2005

Tuberculin reactivity in adults after 50 years of universal bacille Calmette-Guerin vaccination in Taiwan.

We aimed to assess whether tuberculin reactivity in adults is affected by bacille Calmette-Guerin (BCG) vaccination after 50 years of universal BCG vaccination with 80-95% coverage. A community-based study on tuberculin reactivity in 619 participants was conducted in February 2000 in Keelung city, Taiwan. Information on BCG vaccination policies and annual risk of infection (ARI) in the underlying population was extracted from consecutive national prevalence surveys relating to the period 1952-1997. Compared with the expected ARI estimate, the standardized morbidity ratio of positive tuberculin response for vaccination in infancy was 2.2 (95% CI 0.3-15.5) for those aged <10 years. The corresponding figures for older age groups ranged from 3.6 (95% CI 2.2-5.9) for those aged 10-12 years to 0.7 (95% CI 0.5-0.9) for those aged 57-67 years. This suggests that the effect of BCG vaccination on positive tuberculin response in adults aged >30 years is probably negligible irrespective of age at vaccination or revaccination and that the tuberculin skin test can be used to diagnose TB in control programmes in countries with moderate or high incidence of TB.

Adolescent↗
PubMed2005

The transient appearance of collateral circulation during coronary spasm.

This article reports a case of transient augmentation of collateral circulation due to spontaneous coronary arterial spasm during angiography. The patient's electrocardiogram revealed ST-segment depression during vasospastic attack; this depression differs from the typical change of the ST-segment elevation in coronary spasm without collateral circulation.

Collateral Circulation↗
PubMed2005

A novel application of an anaerobic membrane process in wastewater treatment.

The applications of membrane processes in anaerobic biological wastewater treatment still have some limitations due to severe membrane scaling and fouling, although they have been proven to achieve superior COD removal and biomass retention. An innovative anaerobic membrane process for wastewater treatment was conducted to control the membrane scaling problems. The process comprises an anaerobic reactor, an aerobic reactor, and a membrane separation tank. Anaerobic sludge from a full-scale UASB reactor treating food wastewater was inoculated to anaerobic and aerobic reactor to purify synthetic wastewater consisting of glucose and sodium acetate. The anaerobic reactor was operated in a sludge bed type without three-phase separator. The aerobic reactor can eliminate residual organics from the anaerobic reactor effluent using facultative microorganisms. To provide solid-liquid separation, hollow fiber ultrafiltration module was submerged in the separation tank. The results clearly show that the anaerobic membrane process combined methanogenic and aerobic COD reduction is a stable system. No fatal scaling was found after two months of operation even without chemical cleaning for the membrane. It was also found that inorganic precipitates formed in the aerobic reactor were reduced due to CO2 stripping in aerobic reactor. Another important finding was that the inorganic precipitates were entrapped into facultative aerobes floc. The ash/SS ratio of aerobes floc increased from 0.17 to 0.55 after 50 days of operation, which confirms this phenomenon. Based on our investigation, the new process can control scaling effectively to extend the membrane application in anaerobic treatment.

Bacteria, Aerobic↗
PubMed2004

Morphological and photoelectrochemical characterization of core-shell nanoparticle films for dye-sensitized solar cells: Zn-O type shell on SnO2 and TiO2 cores.

Core-shell type nanoparticles with SnO2 and TiO2 cores and zinc oxide shells were prepared and characterized by surface sensitive techniques. The influence of the structure of the ZnO shell and the morphology ofnanoparticle films on the performance was evaluated. X-ray absorption near-edge structure and extended X-ray absorption fine structure studies show the presence of thin ZnO-like shells around the nanoparticles at low Zn levels. In the case of SnO2 cores, ZnO nanocrystals are formed at high Zn/Sn ratios (ca. 0.5). Scanning electron microscopy studies show that Zn modification of SnO2 nanoparticles changes the film morphology from a compact mesoporous structure to a less dense macroporous structure. In contrast, Zn modification of TiO2 nanoparticles has no apparent influence on film morphology. For SnO2 cores, adding ZnO improves the solar cell efficiency by increasing light scattering and dye uptake and decreasing recombination. In contrast, adding a ZnO shell to the TiO2 core decreases the cell efficiency, largely owing to a loss of photocurrent resulting from slow electron transport associated with the buildup of the ZnO surface layer.

Journal Article↗
PubMed2003

Development of a novel aspherical mirror bender for an active grating.

A novel monolithic mechanical bender has been designed and fabricated to meet the requirements of an active polynomial grating in a new soft X-ray scattering and emission beamline at the National Synchrotron Radiation Research Center, Taiwan. This compact bender achieves nearly fixed center point under different bending conditions. Moreover, the compact bender can be bent to a desirable third-order polynomial surface profile to cancel the defocus and coma aberrations using two PZT actuators. Theoretical analysis reveals that the grating has unprecedented spectral resolving power. A detailed mechanical analysis has been conducted and a prototype bender was fabricated and tested. The results indicate that the performance of the bender is excellent and is therefore suitable to be used in the active grating.

Computer-Aided Design↗
PubMed2002

Random laser in one dimension.

We present an analytical approach to random lasing in a one-dimensional medium, consistent with transfer matrix numerical simulations. It is demonstrated that the lasing threshold is defined by transmission through the passive medium and thus depends exponentially on the size of the system. Lasing in the most efficient regime of strong three-dimensional localization of light is discussed. We argue that the lasing threshold should have anomalously strong fluctuations from probe to probe, in agreement with recent measurements.

Journal Article↗
PubMed2002

Dominant NZB contributions to lupus in the (SWR x NZB)F1 model.

(SWR x NZB)F1 (or SNF1) mice succumb to lupus nephritis. Analysis of NZB x SNF1 backcross mice has recently revealed the existence of four dominant SWR loci (H2 on Chr 17, Swrl-1 on Chr 1, Swrl-2 on Chr 14 and Swrl-3 on Chr 18), and two NZB loci (Nba1 and Lbw2/Sbw2, both on Chr 4) conferring lupus susceptibility. The present study focusing on a panel of 88 SWR x SNF1 backcross mice reveals the existence of five suggestive loci for antinuclear antibody formation, consisting of three dominant NZB contributions (Nba4 on Chr 5, Lbw4 on Chr 6, and Nba5 on Chr 7), and two recessive SWR contributions (Swrl-1 on Chr 1, and Swrl-4 on Chr 10). In addition, this study reveals a dominant NZB locus for GN (Nba3 on Chr 7, peak at 31 cM), and a dominant NZB locus linked to early mortality, on Chr 10 (peak at 4 cM). Collectively, these studies suggest that lupus in the SNF1 strain is the epistatic end-product of four dominant SWR loci and four dominant NZB loci. The immunological functions and molecular identities of these loci await elucidation.

Animals↗
PubMed2001

DNA-mediated immunization of glycoprotein 350 of Epstein-Barr virus induces the effective humoral and cellular immune responses against the antigen.

Epstein-Barr virus (EBV) is a human pathogen that is involved in numerous diseases and tumors. Since the EBV infection occurs in the early ages of life, and most of the population is subsequently exposed to EBV, the conventional method of vaccination to induce the prophylactic immunity cannot be considered effective in coping with the virus infection. In this study, we tested whether the injection of a plasmid vector that contained the gene for glycoprotein 350 (gp350), which had been identified as a ligand for virus' adsorption and a target for virus neutralizing antibodies, could induce effective immune responses against the antigen. As a result, the injection of the constructed plasmid vector into mice induced the production of gp350-specific antibodies. A major isotype of the gp350-specific antibodies was IgG1. The antibodies efficiently mediated the antibody-dependent cellular cytotoxicity against the cells expressing the gp350 antigen. In addition, the injection of the constructed plasmid vector stimulated the precursor T cell population that was specific to the gp350 antigen. In addition, gp350-specific cytotoxic T lymphocytes were efficiently stimulated by the injection of the constructed plasmid vector. These results suggested that the injection of the plasmid vector, containing the gp350 gene of Epstein-Barr virus, could be one of the most effective ways to induce both prophylactic and therapeutic vaccinations against the virus infection.

Animals↗