The changing epidemiology of varicella and herpes zoster in Hong Kong before universal varicella vaccination in 2014.

In Hong Kong, universal varicella vaccination started in July 2014. Before this, children could receive varicella vaccine via the private market. We analysed the epidemiology of varicella and zoster before universal vaccination. We estimated varicella vaccination coverage through surveys in preschool children. We estimated the burden of varicella and zoster with varicella notifications from 1999/00 to 2013/14, Accident and Emergency Department (A&E) attendance and inpatient admissions to public hospitals from 2004/05 to 2013/14. We fitted a catalytic model to serological data on antibodies against varicella-zoster virus to estimate the force of infection. We found that varicella vaccination coverage gradually increased to about 50% before programme inception. In children younger than 5 years, the annual rate of varicella notifications, varicella admission and zoster A&E attendance generally declined. The annual notification, A&E attendance and hospitalisation rate of varicella and zoster generally increased for individuals between 10 and 59 years old. Varicella serology indicated an age shift during the study period towards a higher proportion of infections in slightly older individuals, but the change was most notable before vaccine licensure. In conclusion, we observed a shift in the burden of varicella to slightly older age groups with a corresponding increase in incidence but it cannot necessarily be attributed to private market vaccine coverage alone. Increasing varicella vaccination uptake in the private market might affect varicella transmission and epidemiology, but not to the level of interrupting transmission.

Validation of the Hong Kong Cantonese Version of World Health Organization Five Well-Being Index for People with Severe Mental Illness.

OBJECTIVE: The World Health Organization Five Well-Being Index (WHO-5) has been developed to measure psychological wellbeing. Translation and linguistic validation of the WHO-5 into a Cantonese version has been accomplished for local use but it is not yet validated in people with severe mental illness in Hong Kong. This study aimed to examine the applicability of WHO-5 in measuring the psychological wellbeing dimension of people with severe mental illness. A brief and easily administrated tool to measure psychological wellbeing of people with severe mental illness can be used to provide an outcome measure in research studies and clinical trials. METHODS: Subjects were randomly recruited from the Extended-Care Patient Intensive Treatment, Early Diversion and Rehabilitation Stepping-Stone Project (EXITERS) and the Rehabilitation Activity Centre (RAC) of Kwai Chung Hospital in Hong Kong. They were invited to complete the abbreviated version of Hong Kong Chinese World Health Organization Quality of Life (WHOQOL-BREF [HK]) and WHO-5 (Cantonese version) separately and concurrent validity was examined. RESULTS: A total of 84 subjects were recruited, 42 each from EXITERS and RAC. In all, 49 (58%) were male and 35 (42%) were female. The mean ± standard deviation age was 43.2 ± 9.7 years. Their mean duration of mental illness was 16.4 ± 10.5 years and the mean years of education was 10.17 ± 2.5 years, i.e. about junior secondary school level in Hong Kong. The internal consistency of the WHO-5 was satisfactory (0.86) and was comparable with previous reports. Regarding validity, 1-factor structure with an eigenvalue of 3.24 explained 64.8% of total variance of WHO-5 for people with severe mental illness. Concurrent validity was established with moderate correlation (0.41-0.51) between WHO-5 and 4 domains of the WHOQOL-BREF (HK). CONCLUSION: The WHO-5 (Cantonese version) is a reliable and valid tool to assess the psychological wellbeing of people with severe mental illness in Hong Kong. It can be used to monitor the effectiveness of psychological intervention aimed at improving the wellbeing of such patients.

Micromixer based on viscoelastic flow instability at low Reynolds number.

We exploited the viscoelasticity of biocompatible dilute polymeric solutions, namely, dilute poly(ethylene oxide) solutions, to significantly enhance mixing in microfluidic devices at a very small Reynolds number, i.e., Re approximately 0.023, but large Peclet and elasticity numbers. With an abrupt contraction microgeometry (8:1 contraction ratio), two different dilute poly(ethylene oxide) solutions were successfully mixed with a short flow length at a relatively fast mixing time of <10 mus. Microparticle image velocimetry was employed in our investigations to characterize the flow fields. The increase in velocity fluctuation with an increase in flow rate and Deborah number indicates the increase in viscoelastic flow instability. Mixing efficiency was characterized by fluorescent concentration measurements. Our results showed that enhanced mixing can be achieved through viscoelastic flow instability under situations where molecular-diffusion and inertia effects are negligible. This approach bypasses the laminar flow limitation, usually associated with a low Reynolds number, which is not conducive to mixing.

Effect of solvent state and isothermal conditions on gelation of methylcellulose hydrogels.

In this study, thermal behavior of aqueous solutions of methyl cellulose (MC) at a constant temperature of 50 degrees C was analyzed. Various samples were studied for two consecutive heating-cooling cycles. The experiments with the solutions prepared using cold de-ionized (DI) water showed that the rate of gelation was higher for higher MC concentrations. However, the rate was slower during the first heating-cooling cycle than during the second cycle. The possible reasons behind such observations are discussed. Various MC solutions prepared using hot DI water were studied for understanding the role of the solvent state in the isothermal gelation process. The gelation of these MC solutions started at a lower MC concentration and resulted in a higher gelation rate. The gelation mechanism responsible for such effects is explored and presented. Finally, a gel-indexing method is proposed to provide a quantitative measure of the gelation state of all the MC gels.

Design of experiment for optimization of plasma-polymerized octafluorocyclobutane coating on very high aspect ratio silicon molds.

As-fabricated deep reactive ion etched (DRIE) silicon mold with very high aspect ratio (>10) feature patterns is unsuitable for poly(dimethylsiloxane) (PDMS) replication because of the strong interaction between the Si surface and the replica and the corrugated mold sidewalls. The silicon mold can be conveniently passivated via plasma polymerization of octafluorocyclobutane (C4F8), which is also employed in the DRIE process itself, to enable the mold to be used repeatedly. To optimize the passivation conditions, we have undertaken a Box-Behnken experimental design on the basis of three passivation process parameters (plasma power, C4F8 flow rate, and deposition time). The measured responses were fluorinated film thickness, demolding status/success, demolding force, and fluorine/carbon ratio on the fifth replica surface. The optimal passivation process conditions were predicted to be an input power of 195 W, a C4F8 flow rate of 57 sccm, and a deposition time of 364 s; these were verified experimentally to have high accuracy. Demolding success requires medium-deposited film thickness (66-91 nm), and the thickness of the deposited films correlated strongly with deposition time. At moderate to high ranges, increased plasma power or gas flow rate promoted polymerization over reactive etching of the film. It was also found that small quantities of the fluorinated surface were transferred from the Si mold to the PDMS at each replication, entailing progressive wear of the fluorinated layer.

Quantification of thermal energy deposited in silicon by multiple femtosecond laser pulses.

We report our study of deposited thermal energy in silicon induced by multiple-pulse femtosecond laser irradiation. Using infrared thermography, we quantified through in situ direct measurement of temperature fields that a significant portion of laser power (two-thirds or more) was deposited into the silicon substrate instead of being reflected or carried away with the ablated material. This is believed to be the first reported study of direct in situ measurement of temperature fields as the result of deposited thermal energy from multiple femtosecond laser pulses. Our simulation results support the measured data.

Simulation and investigation of factors affecting high aspect ratio UV embossing.

UV embossing is a replication method whereby an UV-curable polymer is pressed against a patterned mold and cured with UV irradiation, resulting in a patterned polymeric substrate. High aspect ratio UV embossing will find diverse applications in tissue engineering, micro-optics, display technologies, and sensors. Demolding of an UV-embossed polymer pattern with aspect ratio of 5 from the mold has previously been demonstrated experimentally. In this paper, parameters that affect the demolding process have been identified and investigated. They include cross-linking shrinkage during curing by UV irradiation, modulus of cured polymer, interfacial fracture strength and toughness, and loading method during demolding. Shrinkage is an important parameter, and an optimum level of shrinkage to avoid breakage of the embossing during demolding was found to exist. This optimum level is that at which the maximum stress (sigma(1)max) experienced by the polymer during demolding is minimized. The micromechanics of demolding was found to be different for shrinkage values lower or larger than the optimum value.