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

Urban regeneration with Chinese characteristics : a case study of the Shangbu industrial district, Shenzhen, China

Shangbu Industrial District (SID) is the first industrial district in China that has successful been regenerated into a major commercial and retailing centre. First developed in the 1980s for industrial development, the SID faced the hallowing out of industries in the early 1990s as a result of rapid economic and spatial restructuring in China's regional economy. The expanding residential population, the consequent needs for retailing activities, and the encroachment of the SID by commercial activities have “gentrified” the deindustrializing District into a retailing centre. Successful regeneration of the SID can be attributed first to the failure of the early socialist market economy to anticipate consumption and retailing needs of a growing population. Another reason, ironically, is the weak enforcement of regulations on the emerging land market and land use changes at the Municipal level. The regeneration process generates interesting dynamics and conflicts among the Municipal and District Governments. primary land users, tenants and consumers. This case illustrates that while globalization, economic and spatial restructuring seem to be the universal forces in regenerating cities, the outcome is more of a function of the interplay of various socio-economic and political factors in a specific context

Iodine status of adults in Taiwan 2005–2008, 5 years after the cessation of mandatory salt iodization

Iodine deficiency causes a broad spectrum of disorders across all ages. Mandatory salt iodization in Taiwan successfully reduced the goiter rate from 21.6% to 4.3% in schoolchildren surveyed in 1971. The program continued until 2003 when salt iodization was changed from mandatory to voluntary. The purpose of this study was to investigate the iodine status of Taiwanese individuals after the change in the iodine policy. Methods: Urinary iodine (UI) was measured in samples from adults in the Nutrition and Health Survey in Taiwan 2005–2008. Results: The median UI level was 100 μg/L, and the percentage of populations with UI levels below 100 μg/L and 50 μg/L was 50.1% and 15.1%, respectively, indicating that the iodine status was borderline adequate. Men had a higher UI level than women (102 μg/L vs. 98 μg/L, p = 0.003), and older individuals (age > 60 years) had a lower UI level than younger people, particularly in women. The iodine status of the population < 50 years was sufficient, but it was insufficient in older groups. Mild iodine insufficiency was noted in all areas of Taiwan except the Southern area and Penghu islands, with the lowest UI level of 79 μg/L in the Mountain area. Although the UI level of women of childbearing age (19–44 years) was 103 μg/L, there may be a risk of iodine deficiency during pregnancy. Conclusion: The iodine nutrition of the Taiwanese population in 2005–2008 was borderline adequate, with insufficiency in some subgroups. Further monitoring of the iodine status is necessary