A new culture medium based on genetic algorithms for Isochrysis galbana production relevant to hatcheries

The nutrient content of a commercial seawater culture medium for growing the microalga Isochrysis galbana was optimized using a stochastic strategy based on genetic algorithms. For this, 210 experiments spread over seven generations were carried out. This strategy reduced the number of assays by more than 90% compared to a factorial design involving the optimization of twelve nutrients simultaneously. The optimized medium outperformed the reference medium in all aspects. The genetic algorithm strategy achieved a polyunsaturated fatty acids (PUFAs) productivity of 7.8 mg L−1 day−1 in a continuous culture of I. galbana, corresponding to an increase of 15% compared to the commercial formulation. Carotenoids, on the other hand, increased by 50% d.w. In addition, PUFA yields were significantly improved, which allowed us to reduce the requirement of several nutrients, for instance, N (25%), Mo (20%), Mn (60%), Co (60%), and Cu (60%).

Genetic Analysis of Salinity Tolerance in Wheat (Triticum aestivum L.)

Background: The understanding of the genetics of salt tolerance is of utmost need to combat the rising prevalence of soil salinity through employing tolerant cultivars. The current study was carried out to investigate the quantitative genetic basis of agronomical and physiological-related traits of salinity-stressed plants using the seven generations (parents, F1, F2, F3, and backcrosses) of wheat grown in the field under normal and saline conditions. Results: The combined analysis of variance showed highly significant effects of salinity and genotypes (generations) on all the traits. The scaling tests did not support the three-parameter model (additive-dominance model); hence, the six-parameter model was used to assess the genetic effects governing the traits in this study. The epistatic gene effects were crucial, as were additive and dominance gene effects for plant height, K/Na, and yield in salinity stress conditions. The highest heritability was observed for total chlorophyll, carotenoid, SPAD chlorophyll, and K/Na ratio in saline conditions. The additive genetic variance was more important than the dominance variance for grain weight, K, K/Na in salinity conditions. Conclusions: The findings of the current study may have important implications in the quantitative genetics of salinity tolerance and the development of cultivars tolerant to salinity in wheat.

Newly identified parasitic nematode beta-tubulin alleles confer resistance to benzimidazoles

Infections by parasitic nematodes cause large health and economic burdens worldwide. We use anthelmintic drugs to reduce these infections. However, resistance to anthelmintic drugs is extremely common and increasing worldwide. It is essential to understand the mechanisms of resistance to slow its spread. Recently, four new parasitic nematode beta-tubulin alleles have been identified in benzimidazole (BZ) resistant parasite populations: E198I, E198K, E198T, and E198stop. These alleles have not been tested for the ability to confer resistance or for any effects that they might have on organismal fitness. We introduced these four new alleles into the sensitive C. elegans laboratory-adapted N2 strain and exposed these genome-edited strains to both albendazole and fenbendazole. We found that all four alleles conferred resistance to both BZ drugs. Additionally, we tested for fitness consequences in both control and albendazole conditions over seven generations in competitive fitness assays. We found that none of the edited alleles had deleterious effects on fitness in control conditions and that all four alleles conferred strong and equivalent fitness benefits in BZ drug conditions. Because it is unknown if previously validated alleles confer a dominant or recessive BZ resistance phenotype, we tested the phenotypes caused by five of these alleles and found that none of them conferred a dominant BZ resistance phenotype. Accurate measurements of resistance, fitness effects, and dominance caused by the resistance alleles allow for the generation of better models of population dynamics and facilitate control practices that maximize the efficacy of this critical anthelmintic drug class.

Half-life of surgical truth in general surgery

Introduction Karl Popper’s hypothetico-deductive model contends that an assertion is true if it agrees with the facts, and that science progresses via paradigms held to be true until replaced by better approximations of reality. Our study aimed to estimate the half-life of surgical dogma. Methods The first 15 general surgery articles at 5-year intervals were extracted from the British Journal of Surgery since its inception in 1913. A statement summarising each article’s conclusion was formatted, and non-conducive articles were excluded (n=22). A total of 293 article statements were reviewed and marked as true or false by a cohort of 15 senior general surgeons, with a majority positive response denoting a true statement. Regression analysis of the relationship between perceived truth and time was performed. Results Median reviewer positive response rate was 49.5% (range 35.8–64.2%), with over 80% of responders in total agreement regarding 151 statements (51.5%) and deeming 137 (46.8%) currently true. Publication year correlated with percentage of true responses (rho 0.647, p=0.002). Linear modelling of true responses related to 5-year intervals (R2=0.398, p=0.002) estimated the annual rate of loss of truth to be 0.25%, equating to a half-life of 200.0 years. Conclusions Contrary to popular belief, it appears THAT surgical dogma does not lose its lustre for some seven generations. Regression line extrapolation is contentious but would suggest that the current era of surgical knowledge extends from 1769 – the days of John Hunter, the ‘father of modern surgery’ – to 2176, although relative rates of innovation may accelerate and move the nexus point.

Identification of transmission chains and clusters associated with COVID-19 in Tunisia

Background The aim of this study was to characterize the transmission chains and clusters of COVID-19 infection in Tunisia. Methods All cases were confirmed by Reverse Transcriptase Polymerase Chain Reaction of a nasopharyngeal specimen. Contact tracing is undertaken for all confirmed cases in order to identify close contacts that will be systematically screened and quarantined. Transmission chains were identified based on field investigation, contact tracing, results of screening tests and by assessing all probable mode of transmission and interactions. Results As of May 18, 2020, 656 cases out of a total of 1043 confirmed cases of Coronavirus disease 2019 belong to 127 transmission chains identified during the epidemic (mean age 42.36 years, Standard deviation 19.56 and sex ratio 0.86). The virus transmission is the most concentrated in the governorate of Tunis (31.5%), Ariana (10.2%) and Ben Arous (10.2%). Virus transmission occurred 50 times (9.72% of secondary transmission events) between two different governorates. A maximum of seven generations of secondary infection was identified, whereas 62% of these secondary infections belong the first generation. A total of 11 “super spreader” cases were identified in this investigation. Four large clusters have been identified. The evolution of secondary cases highlighted two peaks: one in 2nd April and a second in 16 th April whereas imported cases caused local transmission of virus during the early phase of the epidemic. Conclusion Correct contact tracing and early active case finding is useful to identify transmission chains and source of infection in order to contain the widespread transmission in the community.

The effect of powder age in high speed sintering of poly(propylene)

Purpose This study aims to demonstrate for the first time that the cheap, commodity polymer, poly(propylene), can be successfully processed using high speed sintering, and that it can be recycled several times through the process, with little to no detriment to either the polymer itself or the parts obtained. This is significant as a step towards the realisation of high speed sintering as a technology for high-volume manufacturing. Design/methodology/approach A poly(propylene) powder designed for laser sintering was used to build parts on a high speed sintering machine. The unsintered powder was then collected and reused. Repeating this process allowed creation of seven generations of aged powder. A variety of characterisation techniques were then used to measure polymer, powder and part properties for each generation to discern any effects arising from ageing in the machine. Findings It was found that poly(propylene) could be used successfully in high speed sintering, albeit with a low build success rate. Increased powder age was found to correlate to an increase in the build success rate, changes in microscopic and bulk powder properties and improvement to the dimensional accuracy of the parts obtained. By contrast, no discernible correlations were seen between powder age and polymer molecular weight, or between powder age and the tensile properties of parts. Originality/value This is the first report of the use of poly(propylene) in high speed sintering. It is also first study regarding powder recyclability in high speed sintering, both in general and using poly(propylene) specifically.

SELECTION OF THE NIGERIAN INDIGENOUS FOWL FOR 12-WEEK BODY WEIGHT

A FOUNDATION stock of 1171 male and 1210 female indigenous fowl supplied a breeding population which increased from 858 — 1627 over a period of seven generations (about 71 years) During the first three generations 30-38 % of males and females and subsequently about 2.4 — 2.7% males and 25 % females were selected positively for 12 weeks body weight. A non-selected flock mated population of 455 — 615 females and 53 — 70 males per generation provided basis for determining the response to selection. This amounted to 40.1 ± 0.37g, 36.9 ± 0.37g and 39.4 ± 0.37g per generation for male, female and the sexes combined respectively. The realised heritability estimates 0.27 ± 0 03 — 0.28 ± 0.03 appeared close to values obtained by within generation hierachial classification and suggested, no sex-linked effects for the selected trait in this population. The relatively low ultimate male and female mean weights, 760.0 ± 63.1g and 673.5 1 ± 79.0g respectively combined with the marked reduction in the variation of body weight that occurred as selection progressed indicate that the Nigerian indigenous fowl is not a potential broiler strain.