Doctor of Philosophy

dissertationTopological phases are new kind of quantum phases of matter with properties robust against weak disorders and interactions. They occur in two-dimensional electron liquids with quantized Hall conductance and in topological insulators etc. The description of these phases goes beyond Landau's theory of symmetry breaking. They are (partially) characterized by exotic properties, such as topology-dependent ground state degeneracy(GSD), fractional quantum numbers of anyonic excitations and topology-protected bulk-edge duality etc. In this dissertation, we systematically examine exactly solvable discrete models, particularly the so-called Levin-Wen models, for two-dimensional topological phases. They were expected to describe a large class of nonchiral (or, time reversal invariant) two-dimensional topological phases and to provide a Hamiltonian approach to some topological quantum field theories, which are related to topological invariants defined in the mathematical literature. We first show how to construct concrete models of the Levin-Wen type on a two-dimensional graph (generalized lattice), associated with the data from representation theory (the 3j- and 6j-symbols) of finite groups or quantum groups. Then an operator approach is developed to deal with the properties of the models, such as topology-dependent GSD and fractional quantum numbers for quasiparticle excitations. In this approach we are able to demonstrate the topological invariance/symmetry of the models under the mutation transformations of the graph on which the system lives, and explore this invariance to compute the topology-dependent GSD on a torus. Moreover, we use the operator approach to study the fluxon excitations, i.e., quasiparticles living on plaquettes, and to exhibit their fractional exchange (braiding) and exclusion statistics. Also, we explicitly show the correspondence between the degenerate ground states and the quasiparticle excitations: (1) the GSD on a torus is equal to the number of quasiparticle species; and (2) the modular matrices S and T obtained from the modular transformation of the torus for the ground states coincide with those obtained from the fractional exchange statistics of quasiparticles. In this way the present study reveals the first time in the literature the Hilbert space structure for the degenerate ground states as well as that for the excited states, and the interconnection between them in the Levin-Wen models

A meta-analysis of efficacy and safety of doripenem for treating bacterial infections

AbstractObjectiveThe aim of this article is to compare the efficacy and safety of doripenem for bacterial infections.MethodsWe included six randomized clinical trials identified from PubMed and Embase up to July 31, 2014. The included trials compared efficacy and safety of doripenem for complicated intra-abdominal infections, complicated urinary tract infection, nosocomial pneumonia, and acute biliary tract infection. The meta-analysis was carried on by the statistical software of Review Manager, version 5.2.ResultsCompared with empirical antimicrobial agents on overall treatment efficacy, doripenem was associated with similar clinical and microbiological treatment success rates (for the clinical evaluable population, odds ratio [OR]=1.26, 95% confidence interval [CI] 0.93–1.69, p=0.13; for clinical modified intent-to-treatment population, OR=0.88, 95% CI 0.55–1.41, p=0.60; for microbiology evaluable population, OR=1.16, 95% CI 0.90–1.50, p=0.26; for microbiological modified intent-to-treatment (m-mITT), OR=0.98, 95% CI 0.81–1.20, p=0.87). We compared incidence of adverse events and all-cause mortality to analyze treatment safety. The outcomes suggested that doripenem was similar to comparators in terms of incidence of adverse events and all-cause mortality on modified intent-to-treatment population (for incidence of AEs, OR=1.10, 95% CI 0.90–1.35, p=0.33; for all-cause mortality, OR=1.08, 95% CI 0.77–1.51, p=0.67). In nosocomial pneumonia and ventilator-associated pneumonia treatment, doripenem was not inferior to other antibacterial agents in terms of efficacy and safety.ConclusionFrom this meta-analysis, we can conclude that doripenem is as valuable and well-tolerated than empirical antimicrobial agents for complicated intra-abdominal infections, complicated urinary tract infection, acute biliary tract infection and nosocomial pneumonia treatment

A-priori Validation of Subgrid-scale Models for Astrophysical Turbulence

We perform a-priori validation tests of subgrid-scale (SGS) models for the turbulent transport of momentum, energy and passive scalars. To this end, we conduct two sets of high-resolution hydrodynamical simulations with a Lagrangian code: an isothermal turbulent box with rms Mach number of 0.3, 2 and 8, and the classical wind tunnel where a cold cloud traveling through a hot medium gradually dissolves due to fluid instabilities. Two SGS models are examined: the eddy diffusivity (ED) model wildly adopted in astrophysical simulations and the "gradient model" due to Clark et al. (1979). We find that both models predict the magnitude of the SGS terms equally well (correlation coefficient > 0.8). However, the gradient model provides excellent predictions on the orientation and shape of the SGS terms while the ED model predicts poorly on both, indicating that isotropic diffusion is a poor approximation of the instantaneous turbulent transport. The best-fit coefficient of the gradient model is in the range of [0.16, 0.21] for the momentum transport, and the turbulent Schmidt number and Prandtl number are both close to unity, in the range of [0.92, 1.15].Comment: ApJ accepted; analysis code available at https://github.com/huchiayu/Lapriori.j

Exact Master Equation and Quantum Decoherence of Two Coupled Harmonic Oscillators in a General Environment

In this paper we derive an exact master equation for two coupled quantum harmonic oscillators interacting via bilinear coupling with a common environment at arbitrary temperature made up of many harmonic oscillators with a general spectral density function. We first show a simple derivation based on the observation that the two-harmonic oscillator model can be effectively mapped into that of a single harmonic oscillator in a general environment plus a free harmonic oscillator. Since the exact one harmonic oscillator master equation is available [Hu, Paz and Zhang, Phys. Rev. D \textbf{45}, 2843 (1992)], the exact master equation with all its coefficients for this two harmonic oscillator model can be easily deduced from the known results of the single harmonic oscillator case. In the second part we give an influence functional treatment of this model and provide explicit expressions for the evolutionary operator of the reduced density matrix which are useful for the study of decoherence and disentanglement issues. We show three applications of this master equation: on the decoherence and disentanglement of two harmonic oscillators due to their interaction with a common environment under Markovian approximation, and a derivation of the uncertainty principle at finite temperature for a composite object, modeled by two interacting harmonic oscillators. The exact master equation for two, and its generalization to $N$, harmonic oscillators interacting with a general environment are expected to be useful for the analysis of quantum coherence, entanglement, fluctuations and dissipation of mesoscopic objects towards the construction of a theoretical framework for macroscopic quantum phenomena.Comment: 35 pages, revtex, no figures, 2nd version, references added, to appear in PR

SARS-CoV Regulates Immune Function-Related Gene Expressions in Human Monocytic Cells

Background: Severe Acute Respiratory Syndrome (SARS) is characterized by acute respiratory distress (ARDS) and pulmonary fibrosis, and the monocyte/macrophage is the key player in the pathogenesis of SARS.
 
Methods: In this study, we compared the transcriptional profiles of SARS coronavirus (SARS-CoV) infected monocytic cells against that infected by coronavirus 229E (CoV-229E). Total RNA was extracted from infected DC-SIGN transfected monocytes (THP-1-DC-SIGN) at 6 and 24 h after infection and the gene expression was profiled by oligonucleotide-based microarray. 

Results: Analysis of immune-related gene expression profiles showed that 24 h after SARS-CoV infection, (i) IFN-alpha/beta-inducible and cathepsin/proteosome genes were down-regulated; (ii) the hypoxia/hyperoxia-related genes were up-regulated; and (iii) the TLR/TLR-signaling, cytokine/cytokine receptor-related, chemokine/chemokine receptor-related, the lysosome-related, MHC/chaperon-related, and fibrosis-related genes were differentially regulated. 

Conclusion: These results elucidate that monocyte/macrophage dysfunction and dysregulation of fibrosis-related genes are two important pathogenic events of SARS. 
&#xa

Generalized quantum measurement

We overcome one of Bell's objections to `quantum measurement' by generalizing the definition to include systems outside the laboratory. According to this definition a {\sl generalized quantum measurement} takes place when the value of a classical variable is influenced significantly by an earlier state of a quantum system. A generalized quantum measurement can then take place in equilibrium systems, provided the classical motion is chaotic. This paper deals with this classical aspect of quantum measurement, assuming that the Heisenberg cut between the quantum dynamics and the classical dynamics is made at a very small scale. For simplicity, a gas with collisions is modelled by an `Arnold gas'.Comment: 11 pages, LaTeX, no figures, title change

Complementary Therapy with Traditional Chinese Medicine for Neonatal Hypoxic Ischemic Encephalopathy

Hypoxic ischemic encephalopathy (HIE) is one of the most significant causes of morbidity, mortality, and lifelong disability in newborns. The diagnosis of neonatal HIE is based on the dysfunction of neurogenic signs and classification according to the Sarnat staging system, which evaluates conscious level, neuromuscular control, complex reflexes, autonomic function, seizures, electroencephalogram readings, and duration of neurologic sign. There is no standard treatment for neonatal HIE, but it is widely accepted that hypothermia therapy is a safe and effective method for treating neonates with HIE. Traditional Chinese medicine (TCM) has recently been used to treat cases of neonatal HIE, especially herbal medicine prescriptions. Acupuncture is a common method used in TCM and is another promising therapy for neonatal HIE due to its demonstrated effective treatment of the disease in animal models. While there is a lack of direct evidence in clinical practice, we have observed acupuncture to be useful in adult HIE and in animal studies; therefore, we believe a clinical trial designed to evaluate the effectiveness of acupuncture in neonatal HIE treatment is worthwhile. Taken together, TCM is a promising technique that can be integrated into the conventional therapies for neonatal HIE