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BACKGROUND: The Inter-facility Transport (IFT) service provided by the Emergency Department (ED) is a vital service in Hong Kong. Patients need to be rapidly transported over distances to access appropriate healthcare facilities. METHODS: This study aims 1. to examine the resource utilisation of IFT accompanied by ED staff and 2. to analyse the crude, fixed and variable costs of IFT. A retrospective review was conducted of all IFT from Alice Ho Miu Ling Nethersole Hospital in the New Territories of Hong Kong where ED staff accompanied patients from 1 January 2006 to 31 December 2008. Descriptive analysis was used to evaluate the crude, fixed and variable costs per year for providing an ED-based IFT service. RESULTS: There were 337 transports accompanied by either medical or nursing staff from the ED that accounted for around 2% of all IFT. The most common indication for mobilising the transport team was an unstable clinical condition that required neurosurgical care. The average transport service time was 57.7 min per transport (SD 11.0). Resource utilisation consisted of fixed and variable costs that summed up to a cost of HKD $87 224.3 (USD $11 182.6) per year and the crude cost of providing IFT service by the ED was HKD$852.2 (USD $109.3) per patient. CONCLUSION: The crude cost of providing IFT service by the ED was reasonable and acceptable.

A statistical mechanics inspired formulation for the second virial coefficient (B2) correlation is presented. We revisit the formula proposed some 40 years ago based on the simple square-well potential (Hirschfelder, J. O.; Curtis, C. F.; Bird, R. B. Molecular Theory of Gases and Liquids; John Wiley:  New York, 1964). To account for polar and anisotropic effects, we reformulate in terms of an anisotropic square-well potential that also depends on the Euler angles of orientation of the moleulces. A new mean-field second virial formula is derived. Only four parameters are needed in the correlation:  i.e., the repulsive volume, Br, the attractive (range) volume, Va, the interaction energy (well depth), ε, and a temperature correction factor, Dt, due to anisotropy. For some 40 chemicals, such as methane, ethane, propane (hydrocarbons), CO, CO2, oxygen, nitrogen, hydrogen, and water vapor, high accuracy in the correlation is achieved:  most deviations are within 1−5% for the gases studied from low temperatures to temperatures above the Boyle temperature. The parameters Br, Va, ε, and Dt can be expressed in terms of the critical volume, critical temperature, and acentric factor. Comparison with similar industrial correlations (e.g., Hayden, J. G.; O'Connell, J. P. Ind. Eng. Chem. Process Des. Dev. 1975, 14, 209; Tsonopoulos, C. AIChE J. 1974, 20, 263) shows that the present approach is generally more accurate.

The pyrolysis temperature is a critical factor in the synthesis of the silicon−carbon membranes which are derived from poly(dimethylsilane). These membranes show respectable molecular sieving capability when the pyrolysis temperature is 873 K or lower. Permeation of He, H2, N2, CH4, and i-C4H10 through these membranes is dominated by activated diffusion. Nonetheless, a pyrolysis temperature higher than 873 K sinters the micropores and reduces the integrity of the membrane. Consequently, both permeation and permselectivity decline. The 873 K pyrolyzed membrane exhibits H2 permeance of 2.7 × 10^-9 mol Pa^-1 s^-1 m^-2, H2/N2 selectivity of around 20, and H2/i-C4H10 selectivity of around 80, at permeation temperature 473 K.

Several separation processes, including supercritical extraction and supercritical fluid chroma-tography, take advantage of the striking solubility behavior of supercritical fluids. A general theoretical framework is presented for modeling thermodynamic properties of supercritical solutions based on the theory of Kirkwood and Buff. The theory is expressed in terms of the Kirkwood fluctuation integral from statistical mechanics and permits introduction of appropriate molecular solution approximations. Thus, the solute-solvent interaction may be expressed using a local composition approximation, for example, with an accurate equation of state for the pure solvent. This approach is illustrated for two molecular solution approximations and is compared with solubility and partial molecular volume data.

Molecular explanations have recently identified massive solvent clusters surrounding the dissolved solute as the causative agent of the striking solvent properties of supercritical fluids. Such clusters were first inferred from the large negative values of the solute partial molar volume near the solvent critical point; these clusters were estimated to contain about 100 solvent molecules per solute molecule in excess of the bulk average. Subsequent evidence from visible and ultraviolet absorption and fluorescence spectroscopy and from chemical reaction studies have provided qualitative support for the notion of solvent-solute clusters. Other spcctroscopic evidence suggests the formation of solute-solute aggregates, as well, near the solvent critical point. Such structures on a molecular level are describable in terms of the molecular distribution functions. We present results on the size and radial profile of solvent-solute clusters and on solute-solute aggregation for systems representative of typical dilute, attractive, supercritical solutions calculated from integral equation theories. The microstructure of theoretically-predicted dilute, repulsive, supercritical solutions exhibits a deficit of solvent molecules surrounding the solute. Solute partial molar volume and chemical potential are predicted to increase dramatically in such repulsive mixtures as density is increased toward the critical point at slightly supercritical temperatures.

A strength-based model for the single-fibre push-out test has been developed. Using this model, the matrix stress, fibre stress and interfacial shear stress in a single fibre specimen subjected to push-out loading was considered. The effect of physical and geometrical factors on the stress distribution were evaluated in terms of the influence of relative moduli and sizes of the matrix and fibre, respectively. The propensity for debonding crack initiation at the interface arising from matrix yielding (due to normal stress) and interfacial yielding (due to shear stress) has been determined. The influence of these on the location of debonding crack initiation and the maximum debond force has also been studied.

This paper discusses theoretical models for the composition dependence of equations of state and compares the quality of predictions against experimental thermodynamic property data. The mean density approximation (MDA) and the van der Waals one-fluid (VDW1) model are compared with hybrid mixing rules (HMR), in which rigorous composition dependence is used for the second and third virial coefficients and the conformai solution model is used for equation-of-state density terms beyond the third virial term. It is found that when values of unity are used for all binary and three-body unlike interaction parameters, calculated densities for methane-normal heptane mixtures have average absolute deviations of 3.54% for MDA, 4.04% for VDW1, and 2.59% for HMR. When vapor-liquid equilibrium calculations were performed for the methane-normal heptane system, average absolute deviations of calculatedK values from experimental values were 16.7% for methane and 36.4% for normal heptane using HMR, whereas when conformal solution model (CSM) mixing rules were used, the results were 34.8% for methane and 66.7% for normal heptane. When the binary interaction parameter for the characterization of interaction energies is determined, it is found to be less sensitive to state conditions in the case of HMR than either MDA or VDW1. These preliminary results suggest the potential of mixture equation-of-state methods which utilize rigorous composition dependence for the lower-order virial coefficients.

A generalized correlation is developed for the viscosity and thermal conductivity of isotropic fluids under high pressures (up to 200 MPa) and low temperatures (down to 85 K). Two known observations have been taken into consideration in the development of the correlation. First, the Alder correction factors for the Enskog theory values of transport coefficients obtained from molecular dynamics simulations for hard sphere fluids are incorporated. The inclusion of these corrections in the theory makes it possible to describe correctly the density dependence of the hard sphere viscosity and thermal conductivity at high pressures. The hydrodynamic “cage” effect, which is manifested in the molecular motions of dense fluid systems, is thus correctly accounted for. Second, the generalized Eucken relation, which relates the thermal conductivity to the viscosity, is incorporated. As a consequence, an internally consistent correlation is obtained, which can adequately predict the behavior of the thermal conductivity from given values of viscosity. Tests on simple fluids, such as argon, krypton, etc., show that the correlation is valid within a few percent for the entire fluid range where experimental data are available for comparison, and also along the vapor-liquid saturation line, with the exclusion of the critical region. Furthermore, since the variables appearing in the theory are in reduced form, a corresponding states correlation is established for isotropic fluids.

A method to generate new absorbents for water in a novel refrigeration cycle was developed. The cycle, known as the phase separation absorption cycle, relies on phase separation, rather than boiling, to generate the refrigerant. After separation, the refrigerant flows to a conventional evaporator, where it evaporates, resulting in a cooling effect. The vapor is absorbed in a conventional absorber. The phase separation process is projected to require less energy than the conventional boiling process, resulting in higher cycle performance. However, suitable fluids for this cycle have never been found. The computer program developed under this work was used for the systematic design of possible absorbents. Whereas the predictive techniques which serve as kernel of the program can only provide approximate results, they allow fast screening of candidate absorbents. A model of the cycle was run for each potential absorbent, to establish whether the cycle and absorbent were compatible. A total of over 250,000 molecules were investigated, allowing the identification of a few with the potential to work in conjunction with the cycle.

A method to generate new absorbents for water in a novel refrigeration cycle was developed. The cycle, known as the phase separation absorption cycle, relies on phase separation, rather than boiling, to generate the refrigerant. After separation, the refrigerant flows to a conventional evaporator, where it evaporates, resulting in a cooling effect. The vapor is absorbed in a conventional absorber. The phase separation process is projected to require less energy than the conventional boiling process, resulting in higher cycle performance. However, suitable fluids for this cycle have never been found. The computer program developed under this work was used for the systematic design of possible absorbents. Whereas the predictive techniques which serve as kernel of the program can only provide approximate results, they allow fast screening of candidate absorbents. A model of the cycle was run for each potential absorbent, to establish whether the cycle and absorbent were compatible. A total of over 250,000 molecules were investigated, allowing the identification of a few with the potential to work in conjunction with the cycle.

The applicability of the push out technique to fibre composite systems with both excellent and poor interfacial bonding has been considered through experimental push out studies on model polymer matrix and metal matrix composite systems, respectively. Some factors which affect the reliability and reproducibility of data from the push out test have also been established. The findings are applicable to ceramic matrix composites. The interfacial properties of the model steel fibre/epoxy matrix, copper fibre/epoxy matrix, steel fibre/aluminium matrix, and SiC fibre/aluminium matrix composite systems were studied. Factors which influence the reproducibility of interfacial properties such as the interfacial bond strength and the matrix shrinkage pressure as determined from the push out test have been identified. These include the thickness/fibre diameter ratio, the relative diameter of the fibre and the specimen, and the aspect ratio of the fibre in the push out specimen. It was also important to establish the nature offailure at the interface.

The interaction between nocodazole and calf brain tubulin in 10(-2) M sodium phosphate, 10(-4) M GTP, and 12% (v/v) dimethyl sulfoxide at pH 7.0 was studied. The number of binding sites for nocodazole was shown to be one per tubulin monomer of 50,000 as a result of equilibrium binding studies by gel filtration and spectroscopic techniques. The presence of microtubule-associated proteins did not significantly affect the binding of nocodazole to tubulin. The apparent equilibrium constant measured at 25 degrees C was (4 +/- 1) X 10(5) M-1. Temperature does not significantly affect the apparent equilibrium constant; hence, the binding of nocodazole to tubulin is apparently entropy driven. Stopped flow spectroscopy was employed to monitor the rate of nocodazole binding under pseudo first order conditions. The effects of temperature and nocodazole concentration were studied. The apparent rate constants were dependent on the concentration of nocodazole in a nonlinear manner. In conjunction with results from structural and thermodynamic studies the kinetic results were interpreted to suggest a mechanism of T + N in equilibrium with TN in equilibrium with T* N, where T and N are tubulin and nocodazole, respectively. T and T* represent two conformational states of tubulin. Furthermore, the kinetic data are consistent with the thermodynamic data only if a model of two parallel similar reactions were considered, one rapid and the other slow. The initial binding step for both the rapid and slow phases was characterized by identical binding constants; however, there was a significant difference in the rates of isomerization. Hence, nocodazole is potentially a useful probe for amplifying differences in solution properties of tubulin subspecies.

A thermodynamic consistency principle is established for the closure relations in integral equations that can yield accurate correlation functions as well as accurate thermodynamic properties, A brief lour d'horizon is given for existing consistency approaches. In addition to the common pressure consistency and the pressure energy consistency, we introduce a third requirement based on the Gibbs-Duhem relation. We found that Gibbs Duhem relation, mediated through the chemical potential, is instrumental in procuring accurate behavior of the bridge function and cavity Junction in the overlapping region (0 * andp* (T* as low as 0.72 andp* up to 11,90(, For more than IS state points we obtain excellent agreement in internal energy, pressure, and chemical potential. Comparison with Monte Carlo data on the bridge Junction and the radial distribution function also shows that the present approach is highly accurate.

A procedure frequently proposed in the literature for calculating chemical potentials relies on the Kirkwood charging process. Numerical problems associated with coupling large repulsive forces can be avoided by estimating the contribution to the chemical potential due to these forces with scaled particle theory. The contribution due to soft repulsive forces and attractive forces can be calculated with the Kirkwood charging process using distribution functions for a test particle obtained from integral equation theories. We have used the accurate HMSA theory of Zerah and Hansen to provide distribution functions in mixtures of Lennard-Jones molecules, and we have used the PYP theory of Lee to scale the distribution functions over the charging process. The theory provides accurate estimates of chemical potentials over a range of densities from gas-like to liquid-like when the reduced temperature kT/? is greater than 2. Accurate results for excess free energy changes of mixing are also obtained at these conditions. At lower temperatures accurate results are obtained for low to moderate reduced densities (?s3?0.5).

Arterial post-stenotic dilatation (PSD) is a fusiform swelling immediately downstream to a stenosis. It is characterized by the presence of turbulent blood flow and wall vibration which has been claimed by others to be causal by producing structural weakening. We tested the hypothesis that vibration causes PSD in vivo by attaching electromagnetic and pneumatic vibrators to the aortic wall in chronic rabbits. We also observed whether mechanical vibration of the aorta in vivo influenced the distribution of oil-red-O lesions during one percent dietary cholesterol feeding. Low mass vibration gauges were developed to measure the vibration. Electromechanical vibrators having a ceramic magnet slug within a coil supplied with 50 Hz were glued to the aorta of chronic rabbits and the vibration maintained for an average of 8 weeks. Despite greater amounts of energy imparted to the wall there was no dilatation or difference in oil-red-O staining from the controls. Five weeks vibration at 100 Hz and an amplitude equal to the normal diameter pulse also produced no dilatation. We conclude that vibration does not cause PSD in vivo and suggest that its cause is likely to involve the vascular muscle stimulated by the effect of turbulent flow on the endothelium.

Arterial post-stenotic dilatation (PSD) is a fusiform swelling immediately downstream to a stenosis. It is characterized by the presence of turbulent blood flow and wall vibration which has been claimed by others to be causal by producing structural weakening. We tested the hypothesis that vibration causes PSD in vivo by attaching electromagnetic and pneumatic vibrators to the aortic wall in chronic rabbits. We also observed whether mechanical vibration of the aorta in vivo influenced the distribution of oil-red-O lesions during one percent dietary cholesterol feeding. Low mass vibration gauges were developed to measure the vibration. Electromechanical vibrators having a ceramic magnet slug within a coil supplied with 50 Hz were glued to the aorta of chronic rabbits and the vibration maintained for an average of 8 weeks. Despite greater amounts of energy imparted to the wall there was no dilatation or difference in oil-red-O staining from the controls. Five weeks vibration at 100 Hz and an amplitude equal to the normal diameter pulse also produced no dilatation. We conclude that vibration does not cause PSD in vivo and suggest that its cause is likely to involve the vascular muscle stimulated by the effect of turbulent flow on the endothelium.

The perturbation approach developed by Weeks, Chandler, and Andersen (WCA) and by Verlet and Weis (VW) for pure systems is here generalized to the case of mixtures. We study binary mixtures of molecules interacting with the 12-6 Lennard-Jones potential, for which Monte Carlo simulations are available for comparison. The work is divided into two parts: The first part presents results of Monte Carlo calculations on mixtures of hard spheres of 864 and 1000 particles. The radial distribution functions generated are used to test the VW representation for the correlation functions of hard-sphere mixtures. This representation is found to work satisfactorily within the expected error limits. The second part deals with the two-step perturbation procedure for calculating the thermodynamic quantities of the Lennard-Jones system. The Lennard-Jones potential is divided into a reference potential, which is strictly repulsive, and an attractive part. The system of the reference potential is represented by a system of hard-sphere mixture with equivalent diameters determined by the WCA rule. Analytical expressions are given for evaluating these equivalent diameters. The Lennard-Jones system is then recovered to the first order by a λ expansion over the reference system. Comparison with Monte Carlo results for a mixture of Lennard-Jones molecules, obeying the Berthelot rule, shows that the total thermodynamic properties are reproduced by the perturbation theory to 1 per cent, while the agreement in excess properties is only moderately successful, similar to some other analytical theories compared here. To reproduce these excess properties, which are extremely small, a precision of 0·1 per cent in the theory is required. The present theory is estimated to be accurate to 1 per cent in view of the successive approximations made.