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Search Results: 1 - 10 of 309600 matches for " C. -T. Hoi "
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Evidence for Direct CP Violation in $B^\pm \to ηh^\pm$ and Observation of $B^0 \to ηK^0$
C. -T. Hoi,P. Chang,for the Belle Collaboration
Physics , 2011, DOI: 10.1103/PhysRevLett.108.031801
Abstract: We report measurements of the branching fractions and CP asymmetries for B^+- -> eta h^+- (h = K or pi) and the observation of the decay B^0 -> eta K^0 from the final data sample of 772x10^6 BBbar pairs collected with the Belle detector at the KEKB asymmetric-energy e^+e^- collider. The measured branching fractions are Br(B^+- -> eta K^+-) = (2.12 +- 0.23 +- 0.11)x10^-6}, Br(B^+- -> eta pi^+-) = (4.07 +- 0.26 +- 0.21)x10^{-6} and Br(B^0 -> eta K^0) = (1.27^{+0.33}_{-0.29} +- 0.08)x10^-6, where the last decay is observed for the first time with a significance of 5.4 standard deviations (\sigma). We also find evidence for CP violation in the charged B modes, A_{CP}(B^+- -> eta K^+-) = -0.38 +- 0.11 +- 0.01 and A_{CP}(B^+- -> eta pi^+- = -0.19 +- 0.06 +- 0.01 with significances of 3.8 sigma and 3.0 sigma, respectively. For all measurements, the first and second uncertainties are statistical and systematic, respectively.
Partial functions and domination
C. T. Chong,Gordon Hoi,Frank Stephan,Daniel Turetsky
Computer Science , 2015, DOI: 10.2168/LMCS-11(3:16)2015
Abstract: The current work introduces the notion of pdominant sets and studies their recursion-theoretic properties. Here a set A is called pdominant iff there is a partial A-recursive function $\psi$ such that for every partial recursive function $\phi$ and almost every x in the domain of $\phi$ there is a y in the domain of $\psi$ with $y\leq x$ and $\psi(y) > \phi(x)$. While there is a full $\Pi^0_1$-class of nonrecursive sets where no set is pdominant, there is no $\Pi^0_1$-class containing only pdominant sets. No weakly 2-generic set is pdominant while there are pdominant 1-generic sets below K. The halves of Chaitin's $\Omega$ are pdominant. No set which is low for Martin-Loef random is pdominant. There is a low r.e. set which is pdominant and a high r.e. set which is not pdominant.
Spontaneously Broken Technicolor and the Dynamics of Virtual Vector Technimesons
Christopher T. Hill,Dallas C. Kennedy,Tetsuya Onogi,Hoi--Lai Yu
Physics , 1992, DOI: 10.1103/PhysRevD.47.2940
Abstract: We propose spontaneously breaking technicolor, thus liberating techniquarks and suppressing large resonance contributions to the electroweak $S$ parameter. The dynamics is modeled by a fermion bubble approximation to a single massive techni--gluon exchange potential. This contains a Nambu--Jona-Lasinio model with additional interactions. ``Virtual'' vector mesons occur and contribute to $S$, and their effects are studied. Models of broken technicolor are discussed.
Liquid crystal pretilt control by inhomogeneous surfaces
Jones T. K. Wan,Ophelia K. C. Tsui,Hoi-Sing Kwok,Ping Sheng
Physics , 2005, DOI: 10.1103/PhysRevE.72.021711
Abstract: We consider the pretilt alignment of nematic liquid crystal (LC) on inhomogeneous surface patterns comprising patches of homeotropic or homogeneous alignment domains, with azimuthal anisotropy assumed in the surface plane. We found that the resultant LC pretilt generally increases continuously from the homogeneous limit to the homeotropic limit as the area fraction of the homeotropic region increases from 0 to 1. The variations are qualitatively different depending on how the distance between patches compares to the extrapolation length of the stronger anchoring domain. Our results agree with those previously found in stripped patterns. The present findings may provide useful guidelines for designing inhomogeneous alignment surfaces for variable LC pretilt control - a subject of much technological interest in recent years.
Immunopotentiating Activity of Dendrobium Species in Mouse Splenocytes  [PDF]
David T. W. Lau, Michel K. T. Poon, Hoi Yan Leung, Kam Ming Ko
Chinese Medicine (CM) , 2011, DOI: 10.4236/cm.2011.23017
Abstract: This study aimed to explore a pharmacological activity marker for quality assurance of Dendrobium species. The immunopotentiating activity in aqueous extracts prepared from four Dendrobium species, including D. officinalis, was assessed by an in vitro assay of concanavalin A (Con A)-stimulated proliferation of mouse splenocytes. Four samples of commercially available Dendrobii Caulis were also analyzed for comparison. The results indicated that the aqueous extract of D. officinalis produced immunopotentiating action, as evidenced by the increase in Con A-stimulated proliferation of mouse splenocytes, with the extent of stimulation being more prominent than those of other tested Dendrobium species and Dendrobii Caulis samples. In conclusion, an in vitro immunopotentiation assay may be used for assessing the pharmacological activity of Dendrobium species. The finding that D. officinalis produced a more potent immunopotentiating action is consistent with its "yin-nourishing" action in Chinese medicine, which is more effective than other Dendrobium species in clinical use.
An Analytic Theory for the Orbits of Circumbinary Planets
Gene C. K. Leung,Man Hoi Lee
Physics , 2012, DOI: 10.1088/0004-637X/763/2/107
Abstract: Three transiting circumbinary planets (Kepler-16 b, Kepler-34 b, and Kepler-35 b) have recently been discovered from photometric data taken by the Kepler spacecraft. Their orbits are significantly non-Keplerian because of the large secondary-to-primary mass ratio and orbital eccentricity of the binaries, as well as the proximity of the planets to the binaries. We present an analytic theory, with the planet treated as a test particle, which shows that the planetary motion can be represented by the superposition of the circular motion of a guiding center, the forced oscillations due to the non-axisymmetric components of the binary's potential, the epicyclic motion, and the vertical motion. In this analytic theory, the periapse and ascending node of the planet precess at nearly equal rates in opposite directions. The largest forced oscillation term corresponds to a forced eccentricity (which is an explicit function of the parameters of the binary and of the guiding center radius of the planet), and the amplitude of the epicyclic motion (which is a free parameter of the theory) is the free eccentricity. Comparisons with direct numerical orbit integrations show that this analytic theory gives an accurate description of the planetary motion for all three Kepler systems. We find that all three Kepler circumbinary planets have nonzero free eccentricities.
On-Line Portfolio Selection with Moving Average Reversion
Bin Li,Steven C. H. Hoi
Computer Science , 2012,
Abstract: On-line portfolio selection has attracted increasing interests in machine learning and AI communities recently. Empirical evidences show that stock's high and low prices are temporary and stock price relatives are likely to follow the mean reversion phenomenon. While the existing mean reversion strategies are shown to achieve good empirical performance on many real datasets, they often make the single-period mean reversion assumption, which is not always satisfied in some real datasets, leading to poor performance when the assumption does not hold. To overcome the limitation, this article proposes a multiple-period mean reversion, or so-called Moving Average Reversion (MAR), and a new on-line portfolio selection strategy named "On-Line Moving Average Reversion" (OLMAR), which exploits MAR by applying powerful online learning techniques. From our empirical results, we found that OLMAR can overcome the drawback of existing mean reversion algorithms and achieve significantly better results, especially on the datasets where the existing mean reversion algorithms failed. In addition to superior trading performance, OLMAR also runs extremely fast, further supporting its practical applicability to a wide range of applications.
Online Portfolio Selection: A Survey
Bin Li,Steven C. H. Hoi
Computer Science , 2012,
Abstract: Online portfolio selection is a fundamental problem in computational finance, which has been extensively studied across several research communities, including finance, statistics, artificial intelligence, machine learning, and data mining, etc. This article aims to provide a comprehensive survey and a structural understanding of published online portfolio selection techniques. From an online machine learning perspective, we first formulate online portfolio selection as a sequential decision problem, and then survey a variety of state-of-the-art approaches, which are grouped into several major categories, including benchmarks, "Follow-the-Winner" approaches, "Follow-the-Loser" approaches, "Pattern-Matching" based approaches, and "Meta-Learning Algorithms". In addition to the problem formulation and related algorithms, we also discuss the relationship of these algorithms with the Capital Growth theory in order to better understand the similarities and differences of their underlying trading ideas. This article aims to provide a timely and comprehensive survey for both machine learning and data mining researchers in academia and quantitative portfolio managers in the financial industry to help them understand the state-of-the-art and facilitate their research and practical applications. We also discuss some open issues and evaluate some emerging new trends for future research directions.
Antibody Repertoires in Humanized NOD-scid-IL2Rγnull Mice and Human B Cells Reveals Human-Like Diversification and Tolerance Checkpoints in the Mouse
Gregory C. Ippolito, Kam Hon Hoi, Sai T. Reddy, Sean M. Carroll, Xin Ge, Tobias Rogosch, Michael Zemlin, Leonard D. Shultz, Andrew D. Ellington, Carla L. VanDenBerg, George Georgiou
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0035497
Abstract: Immunodeficient mice reconstituted with human hematopoietic stem cells enable the in vivo study of human hematopoiesis. In particular, NOD-scid-IL2Rγnull engrafted mice have been shown to have reasonable levels of T and B cell repopulation and can mount T-cell dependent responses; however, antigen-specific B-cell responses in this model are generally poor. We explored whether developmental defects in the immunoglobulin gene repertoire might be partly responsible for the low level of antibody responses in this model. Roche 454 sequencing was used to obtain over 685,000 reads from cDNA encoding immunoglobulin heavy (IGH) and light (IGK and IGL) genes isolated from immature, na?ve, or total splenic B cells in engrafted NOD-scid-IL2Rγnull mice, and compared with over 940,000 reads from peripheral B cells of two healthy volunteers. We find that while na?ve B-cell repertoires in humanized mice are chiefly indistinguishable from those in human blood B cells, and display highly correlated patterns of immunoglobulin gene segment use, the complementarity-determining region H3 (CDR-H3) repertoires are nevertheless extremely diverse and are specific for each individual. Despite this diversity, preferential DH-JH pairings repeatedly occur within the CDR-H3 interval that are strikingly similar across all repertoires examined, implying a genetic constraint imposed on repertoire generation. Moreover, CDR-H3 length, charged amino-acid content, and hydropathy are indistinguishable between humans and humanized mice, with no evidence of global autoimmune signatures. Importantly, however, a statistically greater usage of the inherently autoreactive IGHV4-34 and IGKV4-1 genes was observed in the newly formed immature B cells relative to na?ve B or total splenic B cells in the humanized mice, a finding consistent with the deletion of autoreactive B cells in humans. Overall, our results provide evidence that key features of the primary repertoire are shaped by genetic factors intrinsic to human B cells and are principally unaltered by differences between mouse and human stromal microenvironments.
Digital quantum simulation of fermionic models with a superconducting circuit
R. Barends,L. Lamata,J. Kelly,L. García-álvarez,A. G. Fowler,A. Megrant,E. Jeffrey,T. C. White,D. Sank,J. Y. Mutus,B. Campbell,Yu Chen,Z. Chen,B. Chiaro,A. Dunsworth,I. -C. Hoi,C. Neill,P. J. J. O'Malley,C. Quintana,P. Roushan,A. Vainsencher,J. Wenner,E. Solano,John M. Martinis
Physics , 2015, DOI: 10.1038/ncomms8654
Abstract: Simulating quantum physics with a device which itself is quantum mechanical, a notion Richard Feynman originated, would be an unparallelled computational resource. However, the universal quantum simulation of fermionic systems is daunting due to their particle statistics, and Feynman left as an open question whether it could be done, because of the need for non-local control. Here, we implement fermionic interactions with digital techniques in a superconducting circuit. Focusing on the Hubbard model, we perform time evolution with constant interactions as well as a dynamic phase transition with up to four fermionic modes encoded in four qubits. The implemented digital approach is universal and allows for the efficient simulation of fermions in arbitrary spatial dimensions. We use in excess of 300 single-qubit and two-qubit gates, and reach global fidelities which are limited by gate errors. This demonstration highlights the feasibility of the digital approach and opens a viable route towards analog-digital quantum simulation of interacting fermions and bosons in large-scale solid state systems.
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