871 research outputs found

    Aerosol hygroscopicity parameter derived from the light scattering enhancement factor measurements in the North China Plain

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    The relative humidity (RH) dependence of aerosol light scattering is an essential parameter for accurate estimation of the direct radiative forcing induced by aerosol particles. Because of insufficient information on aerosol hygroscopicity in climate models, a more detailed parameterization of hygroscopic growth factors and resulting optical properties with respect to location, time, sources, aerosol chemistry and meteorology are urgently required. In this paper, a retrieval method to calculate the aerosol hygroscopicity parameter, κ, is proposed based on the in situ measured aerosol light scattering enhancement factor, namely f(RH), and particle number size distribution (PNSD) obtained from the HaChi (Haze in China) campaign. Measurements show that f(RH) increases sharply with increasing RH, and that the time variance of f(RH) is much greater at higher RH. A sensitivity analysis reveals that the f(RH) is more sensitive to the aerosol hygroscopicity than PNSD. f(RH) for polluted cases is distinctly higher than that for clean periods at a specific RH. The derived equivalent κ, combined with the PNSD measurements, is applied in the prediction of the cloud condensation nuclei (CCN) number concentration. The predicted CCN number concentration with the derived equivalent κ agrees well with the measured ones, especially at high supersaturations. The proposed calculation algorithm of κ with the f(RH) measurements is demonstrated to be reasonable and can be widely applied

    Possible Supersymmetric Effects on Angular Distributions in BK(Kπ)+B \to K^* (\to K \pi) \ell^+ \ell^- Decays

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    We investigate the angular distributions of the rare B decay, BK(Kπ)+B \to K^* (\to K \pi) \ell^+ \ell^-, in general supersymmetric extensions of the standard model. We consider the new physics contributions from the operators O7,8,9,10O_{7,8,9,10} in small invariant mass region of lepton pair. We show that the azimuthal angle distribution of the decay can tell us the new physics effects clearly from the behavior of the distribution, even if new physics does not change the decay rate substantially from the standard model prediction

    The incidence of all-cause, cardiovascular and respiratory disease admission among 20,252 users of lisinopril vs. perindopril: a cohort study

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    Background: Major international guidelines do not offer explicit recommendations on any specific angiotensin-converting enzyme inhibitor (ACEI) agent over another within the same drug group. This study compared the effectiveness of lisinopril vs. perindopril in reducing the incidence of hospital admission due to all-cause, cardiovascular disease and respiratory disease. Methods: Adult patients who received new prescriptions of lisinopril or perindopril from 2001 to 2005 in all public hospitals and clinics in Hong Kong were included, and followed up for ≥2 years. The incidence of admissions due to all-cause, cardiovascular disease and respiratory disease were evaluated, respectively, by using Cox proportional hazard regression models. The regression models were constructed with propensity score matching to minimize indication biases. Results: A total of 20,252 eligible patients with an average age of 64.5 years (standard deviation 15.0) were included. The admission rate at 24 months within the date of index prescription due to any cause, cardiovascular disease and respiratory disease among lisinopril vs. perindopril users was 24.8% vs. 24.8%, 13.7% vs. 14.0% and 6.9% vs. 6.3%, respectively. Lisinopril users were significantly more likely to be admitted due to respiratory diseases (adjusted hazard ratios [AHR] = 1.25, 95% CI 1.08 to 1.43, p = 0.002 at 12 months; AHR = 1.17, 95% CI 1.04 to 1.31, p = 0.009 at 24 months) and all causes (AHR = 1.12, 95% CI 1.05 to 1.19, p < 0.001 at 24 months) than perindopril users. Conclusions: These findings support intra-class differences in the effectiveness of ACEIs, which could be considered by clinical guidelines when the preferred first-line antihypertensive drugs are recommended

    R-parity violation effect on the top-quark pair production at linear colliders

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    We investigate in detail the effects of the R-parity lepton number violation in the minimal supersymmetric standard model (MSSM) on the top-quark pair production via both ee+e^--e^+ and γγ\gamma-\gamma collision modes at the linear colliders. We find that with the present experimental constrained /R\rlap/{R} parameters, the effect from /R\rlap/{R} interactions on the processes e+ettˉe^+e^-\to t\bar{t} and e+eγγttˉe^+e^- \to \gamma\gamma \to t\bar{t} could be significant and may reach -30% and several percent, respectively. Our results show that the /R\rlap/{R} effects are sensitive to the c.m.s. energy and the relevant /R\rlap/{R} parameters. However, they are not sensitive to squark and slepton masses when mq~400GeVm_{\tilde{q}} \geq 400 GeV (or ml~300GeVm_{\tilde{l}} \geq 300 GeV) and are almost independent on the tanβ\tan\betaComment: Accepted by Phys.Rev.

    Exclusive semileptonic rare decays B>(B ->_ (K,K^*) \ell^+ \ell^- in supersymmetric theories

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    The invariant mass spectrum, forward-backward asymmetry, and lepton polarizations of the exclusive processes BK(K)+,=μ,τB\to K(K^*)\ell^+ \ell^-, \ell=\mu, \tau are analyzed under supersymmetric context. Special attention is paid to the effects of neutral Higgs bosons (NHBs). Our analysis shows that the branching ratio of the process \bkm can be quite largely modified by the effects of neutral Higgs bosons and the forward-backward asymmetry would not vanish. For the process \bksm, the lepton transverse polarization is quite sensitive to the effects of NHBs, while the invariant mass spectrum, forward-backward asymmetry, and lepton longitudinal polarization are not. For both \bkt and \bkst, the effects of NHBs are quite significant. The partial decay widths of these processes are also analyzed, and our analysis manifest that even taking into account the theoretical uncertainties in calculating weak form factors, the effects of NHBs could make SUSY shown up.Comment: Several references are added, typo are correcte

    Hadronic B Decays Involving Even Parity Charmed Mesons

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    Hadronic B decays containing an parity-even charmed meson in the final state are studied. Specifically we focus on the Cabibbo-allowed decays BˉDπ(ρ),DDˉs(),DˉsD()\bar B\to D^{**} \pi(\rho), D^{**}\bar D_s^{(*)}, \bar D^{**}_sD^{(*)} and BˉsDsπ(ρ)\bar B_s\to D_s^{**}\pi(\rho), where DD^{**} denotes generically a p-wave charmed meson. The BDB\to D^{**} transition form factors are studied in the improved version of the Isgur-Scora-Grinstein-Wise quark model. We apply heavy quark effective theory and chiral symmetry to study the strong decays of p-wave charmed mesons and determine the magnitude of the D11/2D13/2D_1^{1/2}-D_1^{3/2} mixing angle. Except the decay to D1(2427)0πD_1(2427)^0\pi^- the predictions for BD0πB^-\to D^{**0}\pi^- agree with experiment. The sign of D11/2D13/2D_1^{1/2}-D_1^{3/2} mixing angle is found to be positive in order to avoid a severe suppression on the production of D1(2427)0πD_1(2427)^0\pi^-. The interference between color-allowed and color-suppressed tree amplitudes is expected to be destructive in the decay BD1(2427)0πB^-\to D_1(2427)^0\pi^-. Hence, an observation of the ratio D1(2427)0π/D1(2427)+πD_1(2427)^0\pi^-/D_1(2427)^+\pi^- can be used to test the relative signs of various form factors as implied by heavy quark symmetry. Although the predicted BD1(2420)0ρB^-\to D_1(2420)^0\rho^- at the level of 3×1033\times 10^{-3} exceeds the present upper limit, it leads to the ratio D1(2420)ρ/D1(2420)π2.6D_1(2420)\rho^-/D_1(2420)\pi^-\approx 2.6 as expected from the factorization approach and from the ratio fρ/fπ1.6f_\rho/f_\pi\approx 1.6 . Therefore, it is crucial to have a measurement of this mode to test the factorization hypothesis. For BˉDˉsD\bar B\to \bar D_s^{**}D decays, it is expected that \bar D_{s0}^*D\gsim \bar D_{s1}D as the decay constants of the multiplet (Ds0,Ds1)(D_{s0}^*,D_{s1}) become the same in the heavy quark limit.Comment: 27 pages, Belle's new data on DD_s^{**} productions in B decays and on the radiative decay D_{s1}-> D_s\gamma are updated and discussed. Add two reference

    Brane fluctuation and the electroweak chiral Lagrangian

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    We use the external field method to study the electroweak chiral Lagrangian of the extra dimension model with brane fluctuation. Under the assumption that the contact terms between the matters of the standard model and KK excitations are heavily suppressed, we use the standard procedure to integrate out the quantum fields of KK excitations and the equation of motion to eliminate the classic fields of KK excitations. At one-loop level, we find that up to the order O(p4)O(p^4), due to the momentum conservation of the fifth dimension and the gauge symmetry of the zero modes, there is no constraint on the size of extra dimension. This result is consistent with the decoupling theorem. However, meaningful constraints can come from those operators in O(p6)O(p^6), which can contribute considerably to some anomalous vector couplings and can be accessible in the LC and LHC.Comment: Revised version, 20 pages in ReVTeX, to appear in PR

    Meta-analysis of T peak –T end and T peak –T end /QT ratio for risk stratification in congenital long QT syndrome

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    Background and objectives: Congenital long QT syndrome (LQTS) predisposes affected individuals to ventricular tachycardia/fibrillation (VF/VF), potentially resulting in sudden cardiac death. The Tpeak–Tend interval and the Tpeak–Tend/QT ratio, electrocardiographic markers of dispersion of ventricular repolarization, were proposed for risk stratification but their predictive values in LQTS have been controversial. A systematic review and meta-analysis was conducted to examine the value of Tpeak–Tend intervals and Tpeak–Tend/QT ratios in predicting arrhythmic and mortality outcomes in congenital LQTS. Method: PubMed and Embase databases were searched until 9th May 2017, identifying 199 studies. Results: Five studies on long QT syndrome were included in the final meta-analysis. Tpeak–Tend intervals were longer (mean difference [MD]: 13 ms, standard error [SE]: 4 ms, P = 0.002; I2 = 34%) in congenital LQTS patients with adverse events [syncope, ventricular arrhythmias or sudden cardiac death] compared to LQTS patients without such events. By contrast, Tpeak–Tend/QT ratios were not significantly different between the two groups (MD: 0.02, SE: 0.02, P = 0.26; I2 = 0%). Conclusion: This meta-analysis showed that Tpeak–Tend interval is significant higher in individuals who are at elevated risk of adverse events in congenital LQTS, offering incremental value for risk stratification
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