Omicron strain spreads with the doubling time of 3.2-3.6 days in South Africa province of Gauteng that achieved herd immunity to Delta variant

Omicron, the novel, highly mutated SARS-CoV-2 Variant of Concern (belonging to the Pango lineage B.1.1.529), was first collected on November 8, 2021, in Gauteng province of South Africa. By the end of November 2021 it has spread towards fixation in Gauteng and was detected on all continents. Based on data collected till December 7, 2021, we showed the exponential growth of the Omicron variant over the four-week period in Gauteng (November 8-December 5, 2021) with the doubling time equal 3.38 day [CI 95%: 3.18-3.61 day]. Log-linear regression suggests that the spread began around October 10, 2021, however due to stochasticity in the initial spread this estimate is likely inaccurate. Phylogenetic analysis indicates that the Omicron strain started to diverge in between October 28 and November 5, 2021. This implies that the hidden spread of Omicron before October 10, 2021 (which would suggest slower strain growth) is unlikely. The very short doubling time of Omicron in Gauteng, a province that has reached herd immunity to the Delta variant (implied by the decrease of the weekly number of cases between July and October, 2021, at no significant mobility restrictions), suggests that Omicron will cause abrupt outbreaks of COVID-19 epidemics across the world, and will become the (temporarily) dominant strain.

Challenges in control of COVID-19: short doubling time and long delay to effect of interventions

Early assessments of the growth rate of COVID-19 were subject to significant uncertainty, as expected with limited data and difficulties in case ascertainment, but as cases were recorded in multiple countries, more robust inferences could be made. Using multiple countries, data streams and methods, we estimated that, when unconstrained, European COVID-19 confirmed cases doubled on average every 3 days (range 2.2–4.3 days) and Italian hospital and intensive care unit admissions every 2–3 days; values that are significantly lower than the 5–7 days dominating the early published literature. Furthermore, we showed that the impact of physical distancing interventions was typically not seen until at least 9 days after implementation, during which time confirmed cases could grow eightfold. We argue that such temporal patterns are more critical than precise estimates of the time-insensitive basic reproduction number R 0 for initiating interventions, and that the combination of fast growth and long detection delays explains the struggle in countries' outbreak response better than large values of R 0 alone. One year on from first reporting these results, reproduction numbers continue to dominate the media and public discourse, but robust estimates of unconstrained growth remain essential for planning worst-case scenarios, and detection delays are still key in informing the relaxation and re-implementation of interventions. This article is part of the theme issue ‘Modelling that shaped the early COVID-19 pandemic response in the UK’.

Newly discovered Synechococcus sp. PCC 11901 is a robust cyanobacterial strain for high biomass production

Cyanobacteria, which use solar energy to convert carbon dioxide into biomass, are potential solar biorefineries for the sustainable production of chemicals and biofuels. However, yields obtained with current strains are still uncompetitive compared to existing heterotrophic production systems. Here we report the discovery and characterization of a new cyanobacterial strain, Synechococcus sp. PCC 11901, with promising features for green biotechnology. It is naturally transformable, has a short doubling time of ≈2 hours, grows at high light intensities and in a wide range of salinities and accumulates up to ≈33 g dry cell weight per litre when cultured in a shake-flask system using a modified growth medium − 1.7 to 3 times more than other strains tested under similar conditions. As a proof of principle, PCC 11901 engineered to produce free fatty acids yielded over 6 mM (1.5 g L−1), an amount comparable to that achieved by similarly engineered heterotrophic organisms.

Unprecedented biomass and fatty acid production by the newly discovered cyanobacteriumSynechococcussp. PCC 11901

Cyanobacteria, which use solar energy to convert carbon dioxide into biomass, are potential solar biorefineries for the sustainable production of chemicals and biofuels. However, yields obtained with current strains are still uncompetitive compared to existing heterotrophic production systems. Here we report the discovery and characterization of a new cyanobacterial strain,Synechococcussp. PCC 11901, with potential for green biotechnology. It is transformable, has a short doubling time of ≈2 hours, grows at high light intensities and a wide range of salinities and accumulates up to 18.3 g dry cell weight/L of biomass – 2-3 times more than previously described for cyanobacteria - when grown in a modified medium containing elevated nitrate, phosphate and iron. As a proof of principle, PCC 11901 engineered to produce free fatty acids did so at unprecedented levels for cyanobacteria, with final yields reaching over 6 mM (1.5 g/L), comparable to those achieved by heterotrophic organisms.

Industrial and Biotechnological Applications of Algae: A Review

Algae are a class of photosynthetic organisms found in both marine and freshwaters habitats. As these organisms have a short doubling time, they are considered among fastest growing creatures. They have different pathways to fix atmospheric carbon dioxide and to efficiently utilize the nutrients to convert it into biomass. In few years, a focus has been shifted towards these organisms due to their food and fuel production capability. In fuel industry algae biofuels have been emerged as a clean, nature friendly, cost effective solution to other fuels. Algae fuels are categorized into bio-ethanol, biogas, bio-hydrogen, biodiesel and bio-oil. Algae as a food have been explored for different applications as in production of single cell proteins, pigments, bioactive substances, pharmaceuticals and cosmetics. The present review has been prepared to throw a light on enormous applications of algae as food and fuel and also to provide some information about different commercially available algae products.

BCR-ABL1 doubling times more reliably assess the dynamics of CML relapse compared with the BCR-ABL1 fold rise: implications for monitoring and management

Rising BCR-ABL1 transcripts indicate potential loss of imatinib response in CML. We determined whether the BCR-ABL1 doubling time could distinguish nonadherence from resistance as the cause of lost response. Distinct groups were examined: (1) acquired clinical resistance because of blast crisis and/or BCR-ABL1 mutations; and (2) documented imatinib discontinuation/interruption. Short doubling times occurred with blast crisis (median, 9.0 days; range, 6.1-17.6 days; n = 12 patients), relapse after imatinib discontinuation in complete molecular response (median, 9.0 days; range, 6.9-26.5 days; n = 17), and imatinib interruption during an entire measurement interval (median, 9.4 days; range, 4.2-17.6 days; n = 12; P = .72). Whereas these doubling times were consistently short and indicated rapid leukemic expansion, fold rises were highly variable: 71-, 9.5-, and 10.5-fold, respectively. The fold rise depended on the measurement interval, whereas the doubling time was independent of the interval. Longer doubling times occurred for patients with mutations who maintained chronic phase (CP: median, 48 days; range, 17.3-143 days; n = 29; P < .0001). Predicted short and long doubling times were validated on an independent cohort monitored elsewhere. The doubling time revealed major differences in kinetics according to clinical context. Long doubling times observed with mutations in CP allow time for intervention. A short doubling time for a patient in CP should raise the suspicion of nonadherence.

Effect of Pin and Subassembly Heterogenity in Sodium Void Worth Calculations

Metal fuelled sodium cooled fast reactors are known to have high breeding ratio and short doubling time. Due to these features they play a very important role in the energy scenario, where higher power growth is required. Large sodium cooled fast reactors have positive sodium void coefficient, which is considered to be undesirable feature even though reactor safety can be established for all design based accidents like loss of flow and transient over power accidents. These types of fast reactors, which have harder neutron spectra are having higher sodium void coefficient compared to ceramic fuelled fast reactors. In many of the safety analysis the total sodium void is calculated and it is used in the safely evaluation. However the sodium in the metal fuelled reactor has got three parts, namely bonding sodium, coolant sodium and the sodium in the inter space of subassembly hexagonal cans. In the reactor accident scenario the behavior of these three components of sodium will be different and will effect the sequence of the accident. The finer details, of the fuel sub assembly, are modeled in to Monte Carlo code and the sodium void coefficient is calculated for each of the component for the fuel zones. This study will be helpful in improving safety of the reactor and also reducing the conservatism in the safely features.