Beating heart coronary surgery and renal function: a prospective randomised study (Presented at 18th Spring Meeting of the Association of Cardiothoracic Anaesthetists: Selected abstracts, Cambridge, UK. 22 June 2001)

Introduction Cardiopulmonary bypass (CPB) is widely regarded as an important contributor to renal failure, a well recognised complication, following coronary artery surgery (CABG). Off-pump coronary surgery (OPCAB) is intuitively considered renoprotective. We examine the extent of renal glomerular and tubular injury in low-risk patients undergoing either OPCAB or on-pump coronary artery bypass (ONCAB).Methods Forty patients awaiting elective CABG were prospectively randomized into those undergoing OPCAB (n = 20) and ONCAB (n = 20). Table 1 illustrates the exclusion criteria. Glomerular and tubular injury were assessed, respectively, by urinary excretion of microalbumin and retinol binding protein (RBP) indexed to urinary creatinine [1]. Daily measurements were made from admission to postoperative day 5. Fluid balance, serum creati-nine and blood urea were also monitored. Results No mortality or renal complication was observed. Both groups had similar demographic make-up. The OPCAB group received fewer coronary grafts than their counterparts (1.8 versus 2.8; P = 0.002). Serum creatinine and blood urea remained normal in both groups throughout the study. A dramatic and similar rise in mean ± 2SD urinary RBP:creatinine ratio occurred in both groups peaking on day 1 (3183 ± 2534 versus 4035 ± 4078; P = 0.43) before returning to baseline levels. These trends were also observed with the urinary microalbumin:creatinine ratio (5.05 ± 2.66 versus 6.77 ± 5.76; P = 0.22). ONCAB patients had a significantly more negative fluid balance on postoperative day 2 (-183 ± 1118 versus 637 ± 847 ml; P < 0.05). Conclusions Although renal dysfunction did not clinically occur in any patient, sensitive indicators revealed significant and similar injury to both renal tubules and glomeruli following either OPCAB or ONCAB. These suggest that avoidance of CPB per se does not offer additional renoprotection to patients at low risk of perioperative renal insult during CABG

Sound generation by a vortex ring collision

A collision between two vortex rings and its sound generation is studied numerically using the contour dynamics method. Results suggest that the radial acceleration and the rate of change of the axial acceleration of the vortex rings are the more important dynamic parameters for sound generation during the interaction. The former is important at or near the pass-through instant when the vortex rings are coplanar and are of unequal strength. The latter, being important in the sound generation during a head-on collision before the vortex ring cores are very close to each other, especially when the rings are thin, is also important in sound generation by an unequal strength vortex ring collision after the pass through when the vortex cores are separated by a distance so that the mutual induction strength does not result in significant change of the impulse of the stronger ring. ©1995 Acoustical Society of America.published_or_final_versio

Effects of a background axisymmetric potential flow on vortex ring pairing sound

Sound generated by the pairing of two coaxial vortex rings in the presence of a background axisymmetric potential flow was studied numerically. Results show that the background flow substantially affects the sound generation process in the beginning of the vortex ring interaction. They also suggest that the axial jerk and radial acceleration/deceleration of vortex rings are the major mechanisms through which pairing sound is produced. The effect of background flow mean shear rate on sound generation is also discussed and the results suggest that higher sound levels will be generated when the vortex rings are interacting within the region of high mean shear in a low speed laminar jet. ©1998 Acoustical Society of America.published_or_final_versio

Paediatric preventative health care use by immigrants in Hong Kong: a pilot study

BACKGROUND: Over 14,000 children arrived in Hong Kong from Mainland China last year to join their recently immigrated parents. The aims of this pilot study were to explore immigrant parents' knowledge and perceptions of the accessibility of paediatric preventative health care services. METHOD: A descriptive survey was administered to parents. Participants (N=27) were grouped by their child's point of entry into the health care system. RESULTS: Most participants lacked knowledge about well-child care and health education. Participants whose children lived in Hong Kong for longer than one year used services for well-child care significantly more than those with shorter stays (χ2=4.50; p=0.03). The major barrier in accessing services was lack of knowledge. CONCLUSIONS: Although a preliminary study, the results suggest a population-based study is needed because lack of familiarity with available services was a reoccurring finding. A more comprehensive assessment of the learning needs of this population is needed so effective ways of familiarizing new immigrants and tracking these children can be developed.published_or_final_versio

Anomalous diffusivity and electric conductivity for low concentration electrolytes in nanopores

The dynamic properties of electrolytes in nanopores were studied using the equilibrium and non-equilibrium molecular dynamic simulations. The realistic primitive model and the restrictive primitive models that were widely used in liquid state theory were applied to the electrolyte model. The electrolytic ions that were found to be immersed in the water were treated as dielectric continuum or macroscopic dielectric continuum. Simulation studies for the discrete solvent primitive model were performed and detailed analysis of the characteristics of the ion radial density functions was done.published_or_final_versio

Narrow sidebranch arrays for low frequency duct noise control

Author name used in this publication: S. K. Tang2012-2013 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

On sound transmission loss across a Helmholtz resonator in a low Mach number flow duct

Author name used in this publication: S. K. Tang2009-2010 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Vortex sound in the presence of a low Mach number flow across a drum-like silencer

Author name used in this publication: S. K. Tang2010-2011 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Inviscid two dimensional vortex dynamics and a soliton expansion of the sinh-Poisson equation

The dynamics of inviscid, steady, two dimensional flows is examined for the case of a hyperbolic sine functional relation between the vorticity and the stream function. The 2-soliton solution of the sinh-Poisson equation with complex wavenumbers will reproduce the Mallier-Maslowe pattern, a row of counter-rotating vortices. A special 4-soliton solution is derived and the corresponding flow configuration is studied. By choosing special wavenumbers complex flows bounded by two rigid walls can result. A conjecture regarding the number of recirculation regions and the wavenumber of the soliton expansion is offered. The validity of the new solution is verified independently by direct differentiation with a computer algebra software. The circulation and the vorticity of these novel flow patterns are finite and are expressed in terms of well defined integrals. The questions of the linear stability and the nonlinear evolution of a finite amplitude disturbance of these steady vortices are left for future studies. © 1998 American Institute of Physics.published_or_final_versio

海浪發電

由於全球人口不斷增長，所以能源需求日益增加。地球上大部份的能源主要來自化石燃料。不過，燃燒化石燃料發電會釋出大量二氧化碳和污染物，造成溫室效應從而導致環境破壞；而且，化石燃料是有限的能源。雖然可用核原料發電，但是核能的安全問題與風險管理不斷受人們爭論。故此，對再生能源的研究及開發是刻不容緩的。本章主要討論其中一種再生能源，海浪發電的好處及近期一些研究成果。published_or_final_versio