76 research outputs found

    Optical Bragg, atom Bragg and cavity QED detections of quantum phases and excitation spectra of ultracold atoms in bipartite and frustrated optical lattices

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    Ultracold atoms loaded on optical lattices can provide unprecedented experimental systems for the quantum simulations and manipulations of many quantum phases and quantum phase transitions between these phases. However, so far, how to detect these quantum phases and phase transitions effectively remains an outstanding challenge. In this paper, we will develop a systematic and unified theory of using the optical Bragg scattering, atomic Bragg scattering or cavity QED to detect the ground state and the excitation spectrum of many quantum phases of interacting bosons loaded in bipartite and frustrated optical lattices. We show that the two photon Raman transition processes in the three detection methods not only couple to the density order parameter, but also the {\sl valence bond order} parameter due to the hopping of the bosons on the lattice. This valence bond order coupling is very sensitive to any superfluid order or any Valence bond (VB) order in the quantum phases to be probed. These quantum phases include not only the well known superfluid and Mott insulating phases, but also other important phases such as various kinds of charge density waves (CDW), valence bond solids (VBS), CDW-VBS phases with both CDW and VBS orders unique to frustrated lattices, and also various kinds of supersolids. The physical measurable quantities of the three experiments are the light scattering cross sections, the atom scattered clouds and the cavity leaking photons respectively. We analyze respectively the experimental conditions of the three detection methods to probe these various quantum phases and their corresponding excitation spectra. We also address the effects of a finite temperature and a harmonic trap.Comment: REVTEX4-1, 32 pages, 16.eps figures, to Appear in Annals of Physic

    Effects of School Closures, 2008 Winter Influenza Season, Hong Kong

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    In winter 2008, kindergartens and primary schools in Hong Kong were closed for 2 weeks after media coverage indicated that 3 children had died, apparently from influenza. We examined prospective influenza surveillance data before, during, and after the closure. We did not find a substantial effect on community transmission

    Rapid emergence and predominance of a broadly recognizing and fast-evolving norovirus GII. 17 variant in late 2014

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    Norovirus genogroup II genotype 4 (GII.4) has been the predominant cause of viral gastroenteritis since 1996. Here we show that during the winter of 2014–2015, an emergent variant of a previously rare norovirus GII.17 genotype, Kawasaki 2014, predominated in Hong Kong and outcompeted contemporary GII.4 Sydney 2012 in hospitalized cases. GII.17 cases were significantly older than GII.4 cases. Root-to-tip and Bayesian BEAST analyses estimate GII.17 viral protein 1 (VP1) evolves one order of magnitude faster than GII.4 VP1. Residue substitutions and insertion occur in four of five inferred antigenic epitopes, suggesting immune evasion. Sequential GII.4-GII.17 infections are noted, implicating a lack of cross-protection. Virus bound to saliva of secretor histo-blood groups A, B and O, indicating broad susceptibility. This fast-evolving, broadly recognizing and probably immune-escaped emergent GII.17 variant causes severe gastroenteritis and hospitalization across all age groups, including populations who were previously less vulnerable to GII.4 variants; therefore, the global spread of GII.17 Kawasaki 2014 needs to be monitored

    Brief Report: Virologic Response by Baseline Viral Load With Dolutegravir Plus Lamivudine vs Dolutegravir Plus Tenofovir Disoproxil Fumarate/Emtricitabine: Pooled Analysis

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    BACKGROUND: To investigate antiviral potency of the 2-drug regimen (2DR) dolutegravir plus lamivudine vs the 3-drug regimen (3DR) dolutegravir plus tenofovir disoproxil fumarate/emtricitabine, we performed a post-hoc analysis assessing antiviral response rates in the phase III GEMINI-1 and GEMINI-2 studies by baseline viral load (VL). SETTING: One hundred ninety-two centers in 21 countries. METHODS: Treatment-naive HIV-1-infected participants with screening VL ≤500,000 copies/mL were randomized 1:1 to once-daily dolutegravir plus lamivudine or dolutegravir plus tenofovir disoproxil fumarate/emtricitabine. Median change from baseline was determined for log10-transformed VL in the overall study population and the subpopulation with baseline VL >100,000 copies/mL. Proportion of participants achieving plasma VL 100,000 copies/mL, median change from baseline at week 4 was -3.38 and -3.40 log10 copies/mL in the 2DR and 3DR groups, respectively; reduction was sustained throughout 48 weeks. Time to VL 100,000 copies/mL than the overall study population (57 [week 8] vs 29 days [week 4]) and similar between the 2DR and 3DR groups. Proportion of participants with VL <50 or <40 copies/mL and target not detected was similar between groups, irrespective of baseline VL, at all tested visits throughout 48 weeks. CONCLUSION: Dolutegravir plus lamivudine demonstrates high antiviral potency in treatment-naive HIV-1-infected individuals across baseline VL strata

    A comparison of the clinical, laboratory and epidemiological features of two divergent subpopulations of Plasmodium knowlesi

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    Plasmodium knowlesi, a simian malaria parasite responsible for all recent indigenous cases of malaria in Malaysia, infects humans throughout Southeast Asia. There are two genetically distinct subpopulations of Plasmodium knowlesi in Malaysian Borneo, one associated with long-tailed macaques (termed cluster 1) and the other with pig-tailed macaques (cluster 2). A prospective study was conducted to determine whether there were any between-subpopulation differences in clinical and laboratory features, as well as in epidemiological characteristics. Over 2 years, 420 adults admitted to Kapit Hospital, Malaysian Borneo with knowlesi malaria were studied. Infections with each subpopulation resulted in mostly uncomplicated malaria. Severe disease was observed in 35/298 (11.7%) of single cluster 1 and 8/115 (7.0%) of single cluster 2 infections (p = 0.208). There was no clinically significant difference in outcome between the two subpopulations. Cluster 1 infections were more likely to be associated with peri-domestic activities while cluster 2 were associated with interior forest activities consistent with the preferred habitats of the respective macaque hosts. Infections with both P. knowlesi subpopulations cause a wide spectrum of disease including potentially life-threatening complications, with no implications for differential patient management

    Performance of reconstruction and identification of τ leptons decaying to hadrons and vτ in pp collisions at √s=13 TeV

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    The algorithm developed by the CMS Collaboration to reconstruct and identify τ leptons produced in proton-proton collisions at √s=7 and 8 TeV, via their decays to hadrons and a neutrino, has been significantly improved. The changes include a revised reconstruction of π⁰ candidates, and improvements in multivariate discriminants to separate τ leptons from jets and electrons. The algorithm is extended to reconstruct τ leptons in highly Lorentz-boosted pair production, and in the high-level trigger. The performance of the algorithm is studied using proton-proton collisions recorded during 2016 at √s=13 TeV, corresponding to an integrated luminosity of 35.9 fb¯¹. The performance is evaluated in terms of the efficiency for a genuine τ lepton to pass the identification criteria and of the probabilities for jets, electrons, and muons to be misidentified as τ leptons. The results are found to be very close to those expected from Monte Carlo simulation

    Observation of nuclear modifications in W±^{±} boson production in pPb collisions at √S^{S}NN = 8.16 TeV

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    Measurement of prompt ψ(2S) production cross sections in proton–lead and proton–proton collisions at √SNN = 5.02 TeV

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