MEASUREMENT OF TURBULENCE IN TERRAIN-DISRUPTED AIRFLOW AT THE HONG KONG INTERNATIONAL AIRPORT USING A DOPPLER LIDAR

The Doppler LIDAR of the Hong Kong Observatory was used to measure eddy dissipation rate (EDR) directly for the first time at the Hong Kong International Airport in an experiment in 2004. EDR is a measure of turbulence intensity adopted by the International Civil Aviation Organization. The laser beam of the LIDAR stared in a direction parallel to the runways and radial velocity data were obtained at a range resolution of 60 m. The velocity structure function was computed based on two different estimates of the velocity fluctuation (viz. temporal and spatial methods) and EDR was then calculated by fitting the structure function with the von Kármán model. The two estimates of velocity fluctuation were found to give comparable EDR values. The LIDAR-derived EDR also turned out to have good correlation with EDR obtained from runway anemometers and a boundary-layer wind profiler. In a case of terrain-disrupted airflow during the experiment, the LIDAR-derived EDR showed that turbulence was present near the centre of a micro-scale vortex to the west of the airport

MEASUREMENT OF TURBULENCE IN TERRAIN-DISRUPTED AIRFLOW AT THE HONG KONG INTERNATIONAL AIRPORT USING A DOPPLER LIDAR

The Doppler LIDAR of the Hong Kong Observatory was used to measure eddy dissipation rate (EDR) directly for the first time at the Hong Kong International Airport in an experiment in 2004. EDR is a measure of turbulence intensity adopted by the International Civil Aviation Organization. The laser beam of the LIDAR stared in a direction parallel to the runways and radial velocity data were obtained at a range resolution of 60 m. The velocity structure function was computed based on two different estimates of the velocity fluctuation (viz. temporal and spatial methods) and EDR was then calculated by fitting the structure function with the von Kármán model. The two estimates of velocity fluctuation were found to give comparable EDR values. The LIDAR-derived EDR also turned out to have good correlation with EDR obtained from runway anemometers and a boundary-layer wind profiler. In a case of terrain-disrupted airflow during the experiment, the LIDAR-derived EDR showed that turbulence was present near the centre of a micro-scale vortex to the west of the airport

NUMERICAL SIMULATION OF VORTEX SHEDDING OBSERVED AT THE HONG KONG INTERNATIONAL AIRPORT USING A SHALLOW MODEL

The Hong Kong International Airport is situated in an area of hilly terrain, with a number of hills to its northeast and on the mountainous Lautau Island to the south. In a stably stratified boundary layer, vortices shed by these hills arc sometimes observed by the Terminal Doppler Weather Radar (TDWR) and the Doppler Light Detection and Ranging (LIDAR) System operated by the Hong Kong Observatory. They have a length scale of at least several hundred metres and occur with a shedding period of 15 to 45 minutes. This paper uses a single-layer shallow water model to simulate the vortex shedding events observed in two wind regimes, namely, an easterly wind case on 19 January 2005 and a northeasterly wind case on 27 January 2002. The model wind field (resolved along the measurement radials of TDWR and LIDAR) and the vortex shedding periods in the simulations were found to be largely consistent with the TDWR and LIDAR observations. Though the dynamical equations are simplified and there is a single layer only, the shallow water model appears to grasp the basic dynamics of the observed shedding events

Determinants of antibiotic prescribing for upper respiratory tract infections in an emergency department with good primary care access: a qualitative analysis

Upper respiratory tract infections (URTIs) account for substantial attendances at emergency departments (EDs). There is a need to elucidate determinants of antibiotic prescribing in time-strapped EDs – popular choices for primary care despite highly accessible primary care clinics. Semi-structured in-depth interviews were conducted with purposively sampled physicians (n = 9) in an adult ED in Singapore. All interviews were analysed using thematic analysis and further interpreted using the Social Ecological Model to explain prescribing determinants. Themes included: (1) reliance on clinical knowledge and judgement, (2) patient-related factors, (3) patient–physician relationship factors, (4) perceived practice norms, (5) policies and treatment guidelines and (6) patient education and awareness. The physicians relied strongly on their clinical knowledge and judgement in managing URTI cases and seldom interfered with their peers’ clinical decisions. Despite departmental norms of not prescribing antibiotics for URTIs, physicians would prescribe antibiotics when faced with uncertainty in patients’ diagnoses, treating immunocompromised or older patients with comorbidities, and for patients demanding antibiotics, especially under time constraints. Participants had a preference for antibiotic prescribing guidelines based on local epidemiology, but viewed hospital policies on prescribing as a hindrance to clinical judgement. Participants highlighted the need for more public education and awareness on the appropriate use of antibiotics and management of URTIs. Organisational practice norms strongly influenced antibiotic prescribing decisions by physicians, who can be swayed by time pressures and patient demands. Clinical decision support tools, hospital guidelines and patient education targeting at individual, interpersonal and community levels could reduce unnecessary antibiotic use

Characterizing Scales of Genetic Recombination and Antibiotic Resistance in Pathogenic Bacteria Using Topological Data Analysis

Pathogenic bacteria present a large disease burden on human health. Control of these pathogens is hampered by rampant lateral gene transfer, whereby pathogenic strains may acquire genes conferring resistance to common antibiotics. Here we introduce tools from topological data analysis to characterize the frequency and scale of lateral gene transfer in bacteria, focusing on a set of pathogens of significant public health relevance. As a case study, we examine the spread of antibiotic resistance in Staphylococcus aureus. Finally, we consider the possible role of the human microbiome as a reservoir for antibiotic resistance genes.Comment: 12 pages, 6 figures. To appear in AMT 2014 Special Session on Advanced Methods of Interactive Data Mining for Personalized Medicin

Interior Structure of a Charged Spinning Black Hole in (2+1)(2+1)-Dimensions

The phenomenon of mass inflation is shown to occur for a rotating black hole. We demonstrate this feature in $(2+1)$ dimensions by extending the charged spinning BTZ black hole to Vaidya form. We find that the mass function diverges in a manner quantitatively similar to its static counterparts in $(3+1)$, $(2+1)$ and $(1+1)$ dimensions.Comment: 5 pages, 2 figures (appended as postscript files), WATPHYS-TH94/0

Charmonium Absorption in the Meson-exchange Model

We review the meson-exchange model for charmonium absorption by hadrons. This includes the construction of the interaction Lagrangians, the determination of the coupling constants, the introduction of form factors, and the predicted cross sections for $J/\psi$ absorption by both mesons and nucleons. We further discuss the effects due to anomalous parity interactions, uncertainties in form factors, constraints from chiral symmetry, and the change of charmed meson mass in medium on the cross sections for charmonium absorption in hadronic matter.Comment: 10 pages, 2 figures. Talk given at Quark Matter 2002 (QM 2002), Nantes, France, 18-24 July 2002. To appear in the proceedings (Nucl. Phys. A

Quantifying Stock Price Response to Demand Fluctuations

We address the question of how stock prices respond to changes in demand. We quantify the relations between price change $G$ over a time interval $\Delta t$ and two different measures of demand fluctuations: (a) $\Phi$, defined as the difference between the number of buyer-initiated and seller-initiated trades, and (b) $\Omega$, defined as the difference in number of shares traded in buyer and seller initiated trades. We find that the conditional expectations $<G >_{\Omega}$ and $_{\Phi}$ of price change for a given $\Omega$ or $\Phi$ are both concave. We find that large price fluctuations occur when demand is very small --- a fact which is reminiscent of large fluctuations that occur at critical points in spin systems, where the divergent nature of the response function leads to large fluctuations.Comment: 4 pages (multicol fomat, revtex

Comparison of K+K^+ and e−e^- Quasielastic Scattering

We formulate $K^+$-nucleus quasielastic scattering in a manner which closely parallels standard treatments of $e^-$-nucleus quasielastic scattering. For $K^+$ scattering, new responses involving scalar contributions appear in addition to the Coulomb (or longitudinal) and transverse $(e,e')$ responses which are of vector character. We compute these responses using both nuclear matter and finite nucleus versions of the Relativistic Hartree Approximation to Quantum Hadrodynamics including RPA correlations. Overall agreement with measured $(e,e')$ responses and new $K^+$ quasielastic scattering data for $^{40}$Ca at |\qs|=500 MeV/c is good. Strong RPA quenching is essential for agreement with the Coulomb response. This quenching is notably less for the $K^+$ cross section even though the new scalar contributions are even more strongly quenched than the vector contributions. We show that this ``differential quenching'' alters sensitive cancellations in the expression for the $K^+$ cross section so that it is reduced much less than the individual responses. We emphasize the role of the purely relativistic distinction between vector and scalar contributions in obtaining an accurate and consistent description of the $(e,e')$ and $K^+$ data within the framework of our nuclear structure model.Comment: 26 pages, 5 uuencoded figures appended to end of this fil

General Brane Geometries from Scalar Potentials: Gauged Supergravities and Accelerating Universes

We find broad classes of solutions to the field equations for d-dimensional gravity coupled to an antisymmetric tensor of arbitrary rank and a scalar field with non-vanishing potential. Our construction generates these configurations from the solution of a single nonlinear ordinary differential equation, whose form depends on the scalar potential. For an exponential potential we find solutions corresponding to brane geometries, generalizing the black p-branes and S-branes known for the case of vanishing potential. These geometries are singular at the origin with up to two (regular) horizons. Their asymptotic behaviour depends on the parameters of the model. When the singularity has negative tension or the cosmological constant is positive we find time-dependent configurations describing accelerating universes. Special cases give explicit brane geometries for (compact and non-compact) gauged supergravities in various dimensions, as well as for massive 10D supergravity, and we discuss their interrelation. Some examples lift to give new solutions to 10D supergravity. Limiting cases with a domain wall structure preserve part of the supersymmetries of the vacuum. We also consider more general potentials, including sums of exponentials. Exact solutions are found for these with up to three horizons, having potentially interesting cosmological interpretation. We give several additional examples which illustrate the power of our techniques.Comment: 54 pages, 6 figures. Uses JHEP3. Published versio