Hindsight is 2020? Lessons in global health governance one year into the pandemic.

Fourteen months into the SARS-CoV-2 pandemic, we identify key lessons in the global and national responses to the pandemic. The World Health Organization has played a pivotal technical, normative and coordinating role, but has been constrained by its lack of authority over sovereign member states. Many governments also mistakenly attempted to manage COVID-19 like influenza, resulting in repeated lockdowns, high excess morbidity and mortality, and poor economic recovery. Despite the incredible speed of the development and approval of effective and safe vaccines, the emergence of new SARS-CoV-2 variants means that all countries will have to rely on a globally coordinated public health effort for several years to defeat this pandemic.

Clarification of purple carrot juice: analysis of the fouling mechanisms and evaluation of the juice quality.

Purple carrot juice was clarified by microfiltration. Two modes of filtration, batch concentration and total recycle were tested and the effect of microfiltration process on permeate flux and membrane fouling was studied. Intrinsic membrane resistance was negligible compared with the fouling resistances, which was less than 5 % of total resistance. Determination of membrane hydraulic permeability showed that water cleaning could permit a recovery of about 7 % of initial hydraulic flux. The analysis of color parameters of feed, permeate and concentrate juice during filtration shows that the a* and b* values decrease for the permeate corresponding respectively to changes from green to red and from blue to yellow. The total sugar and reducing sugars increase in permeate and decrease in concentrate. This work showed that it was possible to clarify the purple carrot juice by microfiltration with a real amelioration of the juice appearance.

Experimental Study of Membrane Fouling during Crossflow Microfiltration of Yeast and Bacteria Suspensions: Towards an Analysis at the Microscopic Level.

Microfiltration of model cell suspensions combining macroscopic and microscopic approaches was studied in order to better understand microbial membrane fouling mechanisms. The respective impact of Saccharomyces cerevisiae yeast and Escherichia coli bacteria on crossflow microfiltration performances was investigated using a multichannel ceramic 0.2 µm membrane. Pure yeast suspensions (5 µm ovoid cells) and mixtures of yeast and bacteria (1 to 2.5 µm rod shape cells) were considered in order to analyse the effect of interaction between these two microorganisms on fouling reversibility. The resistances varied significantly with the concentration and characteristics of the microorganisms. Membrane fouling with pure yeast suspension was mainly reversible. For yeast and bacteria mixed suspensions (6 g L-1 yeast concentration) the increase in bacteria from 0.15 to 0.30 g L-1 increased the percentage of normalized reversible resistance. At 10 g L-1 yeast concentration, the addition of bacteria tends to increase the percentage of normalized irreversible resistance. For the objective of performing local analysis of fouling, an original filtration chamber allowing direct in situ observation of the cake by confocal laser scanning microscopy (CLSM) was designed, developed and validated. This device will be used in future studies to characterize cake structure at the microscopic scale.