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Biomedical subjects

W C Poon

Publications and source records attributed to W C Poon.

6 recordsLinked to original sources
PubMed2005

Community psychiatry in Singapore: a pilot assertive community treatment (ACT) programme.

Severe mental illnesses cause their sufferers dismal functional impairment. The Global Burden of Disease lists schizophrenia among the top 10 contributors to health burden and disability around the world. In the Institute of Mental Health (IMH) of Singapore, 9 out of 10 Class-C beds are occupied by patients whose hospitalisation periods last 300 days on average. Whilst de-institutionalisation has not seen its expected level of success overseas, the provision of community-based psychiatric care has been shown to be more cost-effective than hospital-based inpatient care. As such, there is a need for increased emphasis on community psychiatric services, both to provide and to effectively utilise available resources to assist patients with severe mental illnesses in living and functioning within the community. In line with several other efforts, a pilot Assertive Community Treatment or ACT Programme was launched by IMH in November 2003. This article details the aims, set-up and services of this pilot project funded by the Health Service Development Programme (HSDP) for 3 years, which receives referrals from IMH psychiatrists. With the services provided by the ACT team including psychosocial rehabilitation, it is hoped that patients will continue to receive adequate psychiatric care as well as maintain sufficient skills for self-care and independent living within the community despite the well-documented deteriorating course of psychotic illnesses like schizophrenia.

Behavior Therapy↗
PubMed2001

Conventional optical microscopy of colloidal suspensions.

Optical microscopy can resolve detail at the larger end of the colloidal length scale, and to image suspensions at an individual particle level of resolution would allow the investigation of local behaviour in a way denied to the established scattering techniques. However, to achieve high-contrast single-particle resolution in dense suspensions that are thick enough to show behaviour the same as would be expected in the bulk is not a trivial exercise. We build on established advanced techniques of the conventional (i.e. non-confocal) light microscopy of phase objects to develop a suitable experimental protocol. Furthermore, we demonstrate the effectiveness of this protocol by means of an 'atlas' of the hard-sphere crystalline solid (where random stacking results in many complex facets), which should serve as a compendium for future study.

Bone Cements↗
PubMed2001

Classification of ordering kinetics in three-phase systems.

Though equations of motion containing transport coefficients are required to quantitatively predict the phase-ordering dynamics of any given system, a great deal can be gleaned just from the shape of the free-energy landscape. We demonstrate how to extract the most information concerning phase-ordering phenomenology from a knowledge of a system's free-energy function, or phase diagram. Many putative pathways to equilibrium can be ruled out on the grounds of the second law of thermodynamics. In some parts of the phase diagram, these considerations are sufficient to completely determine the phase-ordering process without ever having to calculate a transport coefficient, even when three phases are present. The results include a large number of regions of the phase diagram with distinct phase-ordering kinetics, and some surprisingly elaborate routes to the equilibrium state. A process is found whereby a crystalline condensation nucleus becomes coated with a shell of gas, buffering it from a majority metastable liquid phase. Our results, based on thermodynamic arguments, are supported by numerical solution of model B, which describes diffusive phase-ordering kinetics. Some of our predictions are tested against experimental observations of colloid-polymer mixtures, described in more detail in the preceding paper [F. Renth, W. C. K. Poon, and R. M. L. Evans, Phys. Rev. E 64, 031402 (2001)]. A compact notation is developed to represent intricate phase-ordering pathways.

Journal Article↗
PubMed2001

Shape of Ocr, the gene 0.3 protein of bacteriophage T7: modeling based on light scattering experiments.

Ocr, the first protein expressed by bacteriophage T7, inhibits type Iota DNA restriction enzymes by preventing them from binding to DNA. This inhibition allows the phage to successfully infect the host. The shape of ocr is modeled on the basis of static and dynamic light scattering measurements. The static light scattering data confirm previous observations that ocr exists in solution as a dimer. The diffusion constant determined by dynamic light scattering indicates a nonspherical shape of the ocr dimer. Hydrodynamic models of ellipsoids are presented, and it is argued that ocr is best described by a prolate ellipsoid with dimensions of 10.4 nm by 2.6 nm. The size and shape predicted by this model are consistent with ocr acting as a mimic of the DNA structure bound by type Iota restriction enzymes.

Bacteriophage T7↗
PubMed2001

Phase separation in star-polymer-colloid mixtures.

We examine the demixing transition in star-polymer-colloid mixtures for star arm numbers f=2,6,16,32 and different star-polymer-colloid size ratios 0.18< or =q< or =0.50. Theoretically, we solve the thermodynamically self-consistent Rogers-Young integral equations for binary mixtures using three effective pair potentials obtained from direct molecular computer simulations. The numerical results show a spinodal instability. The demixing binodals are approximately calculated and found to be consistent with experimental observations.

Journal Article↗