Examination of a high resolution laser optical plankton counter and FlowCAM for measuring plankton concentration and size

Highlights: • A High Resolution-LOPC and a FlowCAM were evaluated for ballast water monitoring. • Both instruments underestimated density compared to microscopy. • Size measurements can be affected by organism orientation and complex morphology. • Both tools might be particularly useful when working with a known community. Abstract: Many commercial ships will soon begin to use treatment systems to manage their ballast water and reduce the global transfer of harmful aquatic organisms and pathogens in accordance with upcoming International Maritime Organization regulations. As a result, rapid and accurate automated methods will be needed to monitoring compliance of ships' ballast water. We examined two automated particle counters for monitoring organisms ≥ 50 μm in minimum dimension: a High Resolution Laser Optical Plankton Counter (HR-LOPC), and a Flow Cytometer with digital imaging Microscope (FlowCAM), in comparison to traditional (manual) microscopy considering plankton concentration, size frequency distributions and particle size measurements. The automated tools tended to underestimate particle concentration compared to standard microscopy, but gave similar results in terms of relative abundance of individual taxa. For most taxa, particle size measurements generated by FlowCAM ABD (Area Based Diameter) were more similar to microscope measurements than were those by FlowCAM ESD (Equivalent Spherical Diameter), though there was a mismatch in size estimates for some organisms between the FlowCAM ABD and microscope due to orientation and complex morphology. When a single problematic taxon is very abundant, the resulting size frequency distribution curves can become skewed, as was observed with Asterionella in this study. In particular, special consideration is needed when utilizing automated tools to analyse samples containing colonial species. Re-analysis of the size frequency distributions with the removal of Asterionella from FlowCAM and microscope data resulted in more similar curves across methods with FlowCAM ABD having the best fit compared to the microscope, although microscope concentration estimates were still significantly higher than estimates from the other methods. The results of our study indicate that both automated tools can generate frequency distributions of particles that might be particularly useful if correction factors can be developed for known differences in well-studied aquatic ecosystems

Effects of radiation on predicted flame temperature and combustion products of a burning liquid fuel spray

The effects of radiative heat transfer calculations on the predicted temperature rise in a burning liquid-fuel spray, are studied. The adiabatic temperature rise resulting from a comprehensive spray combustion model is adjusted for heat transfer to the chamber cooling water by incorporating a radiation model using the Discrete Transfer Technique. The spray combustion model used is of the ‘mixed-is-burnt’ type where combustion is treated as a post process event. The data needed for the combustion post-processor are obtained from an effective property Locally Homogeneous CFD flow model, incorporating a droplet evaporation model to account for the liquid phase. The combustion model itself is based on the minimisation of Gibbs free energy and incorporates kinetic sub-modules for soot formation and oxidation. The results from the combustion model are fed into a radiation sub model for calculating cell emmisivities. These are used to calculate corrective terms for incorporation within the energy balance employed by the combustion model resulting in corresponding temperature (and, subsequently, composition) corrections. The convergence of this iterative process yields results of product concentrations and of temperature throughout the combustion chamber. The predicted results are compared with existing experimental result in a case study. The results are also compared with those obtained from the combustion model with no radiation correction and also with ones obtained with empirical corrections

Clustering of activated CD8 T cells around Malaria-infected hepatocytes is rapid and is driven by antigen-specific cells

Malaria, a disease caused by parasites of the Plasmodium genus, begins when Plasmodium-infected mosquitoes inject malaria sporozoites while searching for blood. Sporozoites migrate from the skin via blood to the liver, infect hepatocytes, and form liver stages which in mice 48 h later escape into blood and cause clinical malaria. Vaccine-induced activated or memory CD8 T cells are capable of locating and eliminating all liver stages in 48 h, thus preventing the blood-stage disease. However, the rules of how CD8 T cells are able to locate all liver stages within a relatively short time period remains poorly understood. We recently reported formation of clusters consisting of variable numbers of activated CD8 T cells around Plasmodium yoelii (Py)-infected hepatocytes. Using a combination of experimental data and mathematical models we now provide additional insights into mechanisms of formation of these clusters. First, we show that a model in which cluster formation is driven exclusively by T-cell-extrinsic factors, such as variability in “attractiveness” of different liver stages, cannot explain distribution of cluster sizes in different experimental conditions. In contrast, the model in which cluster formation is driven by the positive feedback loop (i.e., larger clusters attract more CD8 T cells) can accurately explain the available data. Second, while both Py-specific CD8 T cells and T cells of irrelevant specificity (non-specific CD8 T cells) are attracted to the clusters, we found no evidence that non-specific CD8 T cells play a role in cluster formation. Third and finally, mathematical modeling suggested that formation of clusters occurs rapidly, within few hours after adoptive transfer of CD8 T cells, thus illustrating high efficiency of CD8 T cells in locating their targets in complex peripheral organs, such as the liver. Taken together, our analysis provides novel insights into and attempts to discriminate between alternative mechanisms driving the formation of clusters of antigen-specific CD8 T cells in the liver

Heavy Metal-Induced Oxidative Stress on Seed Germination and Seedling Development: A Critical Review

Heavy metal contamination in soils can influence plants and animals, often leading to toxicosis. Heavy metals can impact various biochemical processes in plants, including enzyme and antioxidant production, protein mobilization and photosynthesis. Hydrolyzing enzymes play a major role in seed germination. Enzymes such as acid phosphatases, proteases and α-amylases are known to facilitate both seed germination and seedling growth via mobilizing nutrients in the endosperm. In the presence of heavy metals, starch is immobilized and nutrient sources become limited. Moreover, a reduction in proteolytic enzyme activity and an increase in protein and amino acid content can be observed under heavy metal stress. Proline, is an amino acid which is essential for cellular metabolism. Numerous studies have shown an increase in proline content under oxidative stress in higher plants. Furthermore, heat shock protein production has also been observed under heavy metal stress. The chloroplast small heat shock proteins (Hsp) reduce photosynthesis damage, rather than repair or help to recover from heavy metal-induced damage. Heavy metals are destructive substances for photosynthesis. They are involved in destabilizing enzymes, oxidizing photosystem II (PS II) and disrupting the electron transport chain and mineral metabolism. Although the physiological effects of Cd have been investigated thoroughly, other metals such as As, Cr, Hg, Cu and Pb have received relatively little attention. Among agricultural plants, rice has been studied extensively; additional studies are needed to characterize toxicities of different heavy metals on other crops. This review summarizes the current state of our understanding of the effects of heavy metal stress on seed germination and seedling development and highlights informational gaps and areas for future research

Role of Bacterial-Fungal Interactions on Heavy Metal Phytotoxicity in Serpentine Soil

This study was conducted to understand the role of bacterial–fungal interactions on heavy metal uptake by Zea mays plants. A pot experiment was conducted for 90 days with Z. mays in serpentine soil inoculated with a Gram-negative bacterium, fungus (Aspergilllus sp.) and both microbes to determine the effects of inoculation on nickel, manganese, chromium and cobalt concentrations in plant tissue and soil. Soil nutrients and soil enzyme activities were measured to determine the effect of inoculations on soil quality. Inoculation of microorganisms increased shoot and root biomass, and the maximum biomass was in the bacterial–fungal inoculation. This could be due to the solubilisation of phosphate and production of indole acetic acid. Although the combination treatment contributed to an increase in heavy metal uptake in Z. mays plants, the lowest translocation was observed in the combination treatment. Moreover, the soil available nitrogen, available phosphorous and total organic carbon content were increased with the microbial inoculation. Similarly, the soil dehydrogenase activity was higher as a result of microbial inoculation, whereas the highest dehydrogenase activity was reported in the combination inoculation. This study confirms the synergistic effect of bacterial–fungal inoculation as a soil-quality enhancer and as a plant-growth promoter in the presence of heavy metals

Killing the predator: impacts of highest-predator mortality on the global-ocean ecosystem structure

Recent meta-analyses suggest that microzooplankton biomass density scales linearly with phytoplankton biomass density, suggesting a simple, general rule may underpin trophic structure in the global ocean. Here, we use a set of highly simplified food web models, solved within a global general circulation model, to examine the core drivers of linear predator–prey scaling. We examine a parallel food chain model which assumes microzooplankton grazers feed on distinct size classes of phytoplankton and contrast this with a diamond food web model allowing shared microzooplankton predation on a range of phytoplankton size classes. Within these two contrasting model structures, we also evaluate the impact of fixed vs. density-dependent microzooplankton mortality. We find that the observed relationship between microzooplankton predators and prey can be reproduced with density-dependent mortality on the highest predator, regardless of choices made about plankton food web structure. Our findings point to the importance of parameterizing mortality of the highest predator for simple food web models to recapitulate trophic structure in the global ocean.</p

Analysis of polymorphisms in the merozoite surface protein-3α gene and two microsatellite loci in Sri Lankan Plasmodium vivax: evidence of population substructure in Sri Lanka.

The geographical distribution of genetic variation in Plasmodium vivax samples (N = 386) from nine districts across Sri Lanka is described using three markers; the P. vivax merozoite surface protein-3α (Pvmsp-3α) gene, and the two microsatellites m1501 and m3502. At Pvmsp-3α, 11 alleles were found with an expected heterozygosity (H(e)) of 0.81, whereas at m1501 and m3502, 24 alleles (H(e) = 0.85) and 8 alleles (H(e) = 0.74) were detected, respectively. Overall, 95 unique three locus genotypes were detected among the 279 samples positive at all three loci (H(e) = 0.95). Calculating the pairwise fixation index (F(ST)) revealed statistically significant population structure. The presence of identical 2-loci microsatellite genotypes in a significant proportion of samples revealed local clusters of closely related isolates contributing to strong linkage disequilibrium between marker alleles. The results show evidence of high genetic diversity and possible population substructure of P. vivax populations in Sri Lanka

Thrombosis, major bleeding, and survival in COVID-19 supported by VV- ECMO in the first vs second wave- multicentre observational study in the UK

BACKGROUND: Bleeding and thrombosis are major complications of veno-venous extracorporeal membrane (VV-ECMO). OBJECTIVES: To assess thrombosis, major bleeding (MB) and 180-day in patients supported by VV-ECMO between first (1st March-31st May 2020) and second (1st June 2020-30th June 2021) waves of the COVID-19 pandemic. PATIENTS/METHODS: Observational study of 309 consecutive patients (≥18years) with severe COVID-19 supported by VV-ECMO in four nationally commissioned ECMO centres, UK. RESULTS: Median age was 48 (19-75)years and 70.6% were male. Probabilities of survival, thrombosis, and MB at 180 days in the overall cohort were 62.5% (193/309), 39.8%(123/309) and 30%(93/309). In multivariate analysis, age >55 years (HR 2.29 [1.33-3.93],p=0.003) and elevated creatinine (HR 1.91 [1.19-3.08],p=0.008) were associated with increased mortality. Corrected for duration of VV-ECMO support, arterial thrombosis alone (HR 3.0 [95% CI1.5-5.9], P= 0.002) or circuit thrombosis alone (HR 3.9 [95% 2.4-6.3], P<0.001), but not venous thrombosis, increased mortality. MB during ECMO had 3-fold risk (95% CI 2.6-5.8, P<0.001) of mortality. The first wave cohort had more males (76.7% vs 64%, p=0.014), higher 180-day survival (71.1% vs 53.3% p=0.003), more venous thrombosis alone (46.4% vs 29.2%, p=0.02) and lower circuit thrombosis (9.2% vs 28.1%, p<0.001). The second wave cohort received more steroids (121/150 [80.6%] vs 86/159 [54.1%], p<0.0001) and Tocilizumab (20/150 [13.3%] vs 4/159 [2.5%] p=0.005). CONCLUSIONS: MB and thrombosis are frequent complications in patients on VV-ECMO and significantly increase mortality. Arterial thrombosis alone or circuit thrombosis alone increased mortality whilst venous thrombosis alone had no effect. MB during ECMO support increased mortality 3.9-fold

Impacts of river regulation and other anthropogenic activities on floodplain vegetation: A case study from Sri Lanka

Since the initiation of large-scale development in late 1970s, the Mahaweli River basin in Sri Lanka has experienced significant changes. However, no comprehensive study has been undertaken so far to evaluate the impacts of river regulation on associated ecosystems including floodplains in the downstream. The present study was aimed at identifying the impacts due to both river regulation and other anthropogenic activities on inland floodplain habitats (locally known as villus) located along the final stretch of the River Mahaweli before reaching the Indian Ocean. Four villus, Handapana (HAN), Bendiya (BEN), Karapola (KAR) and Gengala (GEN), were selected for the study. HAN and BEN can be considered as highly influenced (HI) by river regulation while KAR and GEN as less influenced (LI) due to their respective locations. Due to the absence of pre- regulation vegetation data, HI villus were compared with LI villus in order to explore any potential impacts of river regulation. Vegetation was enumerated using belt transect method. To find out other on-going anthropogenic impacts on these villu ecosystems, a survey was conducted using 100 individuals living in two villages located nearby. The results revealed some significant modification in the composition and the diversity of the vegetation, most possibly due to river regulation and other on-going anthropogenic activities. However, the most notable changes were recorded in the herbaceous layer. Some native aquatic herbaceous species have been completely absent over the period of two decades since the developmental activities begun, while some exotic invasive aquatic species (Eichhornia crassipes) dominated the herbaceous layer in HI villus threatening the survival of the remaining native species. Density and richness of lianas too diminished significantly in HI villus perhaps due to changes of micro-habitat conditions as a result of river regulation and also due to over-harvesting for commercial purposes. The results suggest that these ecosystems have been altered over the years due to culmination of factors including altered flow regimes following river regulation and some on-going human influences. The present study highlights the importance of regulating such human influences on villus including fishing and extracting cane and reed in order to protect these vulnerable ecosystems for future generations. The potential of these ecosystems to develop ecotourism has also been emphasized