Implementation of the compulsory universal testing scheme in Hong Kong: Mathematical simulations of a household-based pooling approach

This study aims to propose a pooling approach to simulate the compulsory universal RT-PCR test in Hong Kong and explore the feasibility of implementing the pooling method on a household basis. The mathematical model is initially verified, and then the simulation is performed under different prevalence rates and pooled sizes. The simulated population is based in Hong Kong. The simulation included 10,000,000 swab samples, with a representative distribution of populations in Hong Kong. The samples were grouped into a batch size of 20. If the entire batch is positive, then the group is further divided into an identical group size of 10 for re-testing. Different combinations of mini-group sizes were also investigated. The proposed pooling method was extended to a household basis. A representative from each household is required to perform the RT-PCR test. Results of the simulation replications, indicate a significant reduction (p < 0.001) of 83.62, 64.18, and 48.46% in the testing volume for prevalence rate 1, 3, and 5%, respectively. Combined with the household-based pooling approach, the total number of RT-PCR is 437,304, 956,133, and 1,375,795 for prevalence rates 1, 3, and 5%, respectively. The household-based pooling strategy showed efficiency when the prevalence rates in the population were low. This pooling strategy can rapidly screen people in high-risk groups for COVID-19 infections and quarantine those who test positive, even when time and resources for testing are limited

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

The Misallocation Problem of Subsidized Housing: A Lesson from Hong Kong

Providing affordable housing has become one of China’s key national policy agenda items. The shared-equity model in Hong Kong, implemented since the late 1970s, has assisted many families in owning a home in the public housing market. However, little attention has been paid to their welfare after acquiring their subsidized units. This study aims to examine how shared-equity homeownership distorts residential mobility through in-kind subsidies. Panel data analysis reveals that the more in-kind subsidies owners receive, the longer they would hold on to their units in spite of spatial mismatches. Private owners, on the other hand, would trade their units without such distortion. Conceptually, the lower mobility of assisted owners could be interpreted as a new source of misallocation in Glaeser and Luttmer’s welfare analysis. Practically, this throws into question the sustainability of a subsidizing homeownership policy: does the government ultimately want assisted homeowners to move from public housing to private housing in the future (for which high mobility would be intended)? If so, new thinking on how to make in-kind subsidies transferable is needed

Evaluation of different demulsifiers for Marpol oil waste recovery

Marpol oil waste composed of wasted oil with seawater which is challenging for waste treatment. Therefore, emulsified seawater has to be broken down for recovering the oil content involving chemical destabilizer to disperse water droplets or destroy emulsifiers. This study aims to evaluate 37 products of demulsifiers (cationic, non-ionic and anionic) based on ability of water removal from Marpol oil waste. The results show that anionic and nonionic surfactants were found to be effective demulsifiers exhibiting good property for oil and water separation. The efficiency of the nonionic demulsifiers increases with the dosage up to a certain extent after which the efficiency falls. However, anionic demulsifiers do not show any decrease in efficiency at higher doses. Among all the tested anionic demulsifiers, sodium dioctyl sulfosuccinate (ALCOPOL O70 PG), sodium dioctyl sulfosuccinate (ALCOPOL O CONC 60%) and Oligoguluronate (DP9-6661) were with most outstanding performance. Additionally there is a general improvement in the performance of screened demulsifiers with increased temperature (70 °C). Sodium dioctyl sulfosuccinate (ALCOPOL O70 PG), sodium dioctyl sulfosuccinate (ALCOPOL O CONC 60%) and sodium dodecyl benzene sulphonate (DP9-6661) reached water removal performance percentage as 75%, 66.3% and 56.7% respectively after 30 h. When the water content of recovered oil was reduced to a certain level (below 10%), the heat valve was about 40 MJ/kg. The recovered Marpol oil waste was suggested to apply for low-quality fuel usage such as cement kilns and waste incinerators with its property of high energy value, low sulphur content and Polychlorinated Biphenyls (PCBs)

Laparoscopic Cholecystectomy for Acute Cholecystitis: The Evolving Trend in an Institution

Laparoscopic cholecystectomy (LC) is the gold standard for symptomatic cholecystolithiasis. Technical maturation and advances in instrumentation have enabled the application of this procedure for acute cholecystitis (AC). We review the evolving role of LC for AC in our institution. Methods: A retrospective study was conducted of patients who received LC for AC between January 1994 and June 2001. Patients' demographics, clinical findings and perioperative outcomes were evaluated. Results: There were 140 men and 141 women with a mean age of 56.9 years (range, 23-89 years). Two hundred and eighteen of these patients underwent successful LC. There were 63 conversions (22.4%) for uncertain anatomy and difficult dissection (41), gangrenous or perforated gallbladder (16) and bleeding (6). The conversion rates as stratified to surgeon's seniority were 25.1%, 22.8% and 9.7% for registrar, senior registrar and consultant, respectively. The mean operative time was 84.3 minutes (range, 30-255 minutes) and the mean postoperative stay was 5.8 days (range, 1-35 days). The overall complication rate was 11.6%, including two bile duct injuries and two perioperative deaths. Conclusion: LC for AC is safe and effective and associated with a low incidence of complications when routinely applied by surgical residents. The conversion rate is related to operators' surgical experience