Nutrient supply is a key bottom-up control of phytoplankton primary production in lake ecosystems. Top-down control via grazing pressure by zooplankton also constrains primary production and primary ...production may simultaneously affect zooplankton. Few studies have addressed these bidirectional interactions. We used convergent cross-mapping (CCM), a numerical test of causal associations, to quantify the presence and direction of the causal relationships among environmental variables (light availability, surface water temperature, NO3-N, and PO4-P), phytoplankton community composition, primary production, and the abundances of five functional zooplankton groups (large cladocerans, small cladocerans, rotifers, calanoids, and cyclopoids) in Lake Kasumigaura, a shallow, hypereutrophic lake in Japan. CCM suggested that primary production was causally influenced by NO3-N and phytoplankton community composition; there was no detectable evidence of a causal effect of zooplankton on primary production. Our results also suggest that rotifers and cyclopoids were forced by primary production, and cyclopoids were further influenced by rotifers. However, our CCM suggested that primary production was weakly influenced by rotifers (i.e., bidirectional interaction). These findings may suggest complex linkages between nutrients, primary production, and rotifers and cyclopoids, a pattern that has not been previously detected or has been neglected. We used linear regression analysis to examine the relationships between the zooplankton community and pond smelt (Hypomesus nipponensis), the most abundant planktivore and the most important commercial fish species in Lake Kasumigaura. The relative abundance of pond smelt was significantly and positively correlated with the abundances of rotifers and cyclopoids, which were causally influenced by primary production. This finding suggests that bottom-up linkages between nutrient, primary production, and zooplankton abundance might be a key mechanism supporting high planktivore abundance in eutrophic lakes. Because increases in primary production and cyanobacteria blooms are likely to occur simultaneously in hypereutrophic lakes, our study highlights the need for ecosystem management to resolve the conflict between good water quality and high fishery production.
Strengthening behavior of composite containing discontinuous reinforcement is strongly related with load transfer at the reinforcement–matrix interface. We selected multi-walled carbon nanotube ...(MWCNT) and few-layer graphene (FLG) as a reinforcing agent. By varying a volume fraction of the reinforcement, aluminum (Al) matrix composites were produced by a powder metallurgy method. Uniform dispersion and uniaxial alignment of MWCNT and FLG in the Al matrix are evidenced by high-resolution transmission electron microscope analysis. Although the reinforcements have a similar molecular structure, FLG has a 12.8 times larger specific surface area per volume more than MWCNT due to geometric difference. Therefore an increment of a yield stress versus a reinforcement volume fraction for FLG shows 3.5 times higher than that of MWCNT Consequently, for both reinforcements, the composite strength proportionally increases with the specific surface area on the composite, and the composites containing 0.7vol% FLG exhibit 440MPa of tensile strength.
Quercetin is a flavonol believed to have beneficial effects on human health. Rutin, found in many plants, fruits and vegetables, is metabolized by human intestinal bacteria and converted to ...quercetin, where it is absorbed through the intestinal epithelium. This study aimed to isolate and characterize human intestinal bacteria capable of converting rutin to quercetin. A bacterium that can metabolize rutin was isolated from human faecal samples and identified by 16S rRNA gene sequencing. The whole‐cell enzymatic activities on flavonoid glycoside and the conversion profiles of the isolate were also analysed. The bacterium was identified as Enterococcus avium EFEL009 and was shown to convert rutin to isoquercetin and then to quercetin under anaerobic conditions. Microscopic analysis revealed short chains of cocci with diameters of approx. 1 μm. β‐Glucosidase was shown to be constitutively expressed in Ent. avium, while α‐rhamnosidase was expressed following induction by rutin. Both enzymes were mainly localized to the cell surface. This study is the first report on the isolation of a quercetin‐producing Ent. avium FEEL009, which could be a potential industrial starter bacterium. SIGNIFICANCE AND IMPACT OF THE STUDY: Quercetin is a member of the flavonoids family reported to have better cytoprotective abilities, stronger inhibition of lipopolysaccharide‐induced nitric oxide production, and better chemoprevention than rutin. This is the first report on the isolation and characterization of Enterococcus avium EFEL009 from the human intestine which is capable of converting rutin to quercetin.
Pure magnesium (Mg) develops a strong basal texture after conventional processing of hot rolling or extrusion. Consequently, it exhibits anisotropic mechanical properties and is difficult to form at ...room temperature. Adding appropriate alloying elements can weaken the basal texture or even change it, but the improvement in formability and mechanical properties is still far from expectations. Over the past 20 years, considerable efforts have been made and significant progress has been made on wrought Mg alloys at the fundamental and technological levels. At the fundamental level, textures formed in sheets and extrusions of different alloy compositions and produced under different strain paths or thermomechanical processing conditions are relatively well established, with the assistance of the advanced characterization technique of electron backscatter diffraction. At the technological level, room temperature formability of sheet has been significantly improved, and tension–compression yield asymmetry of extrusion is also remarkably reduced or eliminated. This paper starts with an overview of dislocations, stacking faults and twins, and deformation of single crystals of pure Mg along different orientations and under different loading conditions, followed by a review of microstructure (texture and grain size) and deformation of polycrystalline pure Mg with different textures, grain sizes, and loading conditions. With this information as a base, texture, grain size, and deformation of polycrystalline Mg alloy sheets and extrusions produced under different processing conditions are systematically examined and compared. Remaining and emerging scientific and technology issues are then highlighted and discussed in the context of texture and grain size. The need for better-resolution diffraction and spectroscopy techniques is also discussed in the relationship between texture change and grain boundary solute segregation.
Aims
Exopolysaccharide fraction from Pediococcus pentosaceus KFT18 (PE‐EPS), a lactic acid bacteria isolated from Kimchi (a Korean fermented vegetable product), was preliminary characterized and its ...immunostimulating effects were analysed.
Methods and Results
In this study, we used interferon‐γ (IFN‐γ)‐primed RAW 264·7 macrophages and CD3/CD28‐stimulated splenocytes to determine the immunotimulatory activities of PE‐EPS. Upon exposure to PE‐EPS, IFN‐γ‐primed RAW 264·7 macrophages showed significant increases in the expressions of inducible nitric oxide synthase (iNOS), tumour necrosis factor‐α (TNF‐α), interleukin (IL)‐6 and IL‐1β. Molecular data using reporter gene assay and electrophoretic mobility shift assay (EMSA) revealed that PE‐EPS upregulated transcriptional activity, DNA binding and the nuclear translocation of nuclear factor‐κB (NF‐κB). Furthermore, PE‐EPS enhanced anti‐CD3/CD28‐specific proliferation and the productions of IL‐2 and IFN‐γ in primary splenocytes. In cyclophosphamide‐induced immunosuppressed mice, pretreatment with PE‐EPS (5, 15 or 45 mg kg−1 day−1, p.o.) increased thymus and spleen indices, and improved lymphocyte and neutrophil counts.
Conclusion
PE‐EPS stimulated the IFN‐γ‐primed macrophages and primary splenocytes to induce immune responses and improved the cyclophosphamide‐induced immunosuppression in mice.
Significance and Impact of the Study
The results in this study improved our understanding of immunostimulating activity of PE‐EPS and supported its potential treatment option as a natural immunostimulant.
Ram pressure stripping can remove significant amounts of gas from galaxies in clusters and massive groups and thus has a large impact on the evolution of cluster galaxies. We find that magnetic ...fields have a strong effect on the morphology of the gas in the tail of the galaxy. While in the purely hydrodynamical case the tail is very clumpy, the magnetohydrodynamical case shows very filamentary structures in the tail. The filaments can be strongly supported by magnetic pressure and, wherever this is the case, the magnetic fields vectors tend to be aligned with the filaments. For significantly tilted disks, the situation may be reversed and the stripping rate may be enhanced by the "scraping" of the disk surface by the magnetic fields sliding past the ISM/ICM interface. Instabilities, such as gravitational instabilities, undo the protective effect of this layer and allow the gas to leak out of the galaxy.
In acid hydrolysis of plant biomass, polysaccharides are converted to monosaccharides, which is basic raw material for biorefinery for fermentation based process. These monosaccharides, however, are ...not stable in acidic reaction medium, and are converted to organic acids via furans. Impact of hemicelluloses and lignin on acid hydrolysis of cellulose was investigated to focus on monosaccharide production with different degrees of cellulose purity. Two-step concentrated sulphuric acid process was applied to biomass for monosaccharide conversion. Kinetics of cellulose hydrolysis was analysed using 1H NMR spectroscopy. Higher reaction temperature in secondary hydrolysis caused severe degradation of the monosaccharides. In pure and holocellulose, further reaction of glucose in acidic reaction medium produced formic acid and levulinic acid. However, lignocellulosic biomass generated much less formic acid and levulinic acid under the same reaction condition. Humin (or pseudo-lignin) was also formed by the condensation of lignin and furans from monosaccharides in acidic reaction condition. Thus, the fermentation inhibitors, furans and formic acid, were generated in low quantities by lignocellulosic biomass than by delignified biomass such as pure cellulose or holocellulose.
•Higher second hydrolysis temperature in concentrated sulphuric acid hydrolysis process led to more gluocose degradation products (formic acid, 5-hydroxymethylfurfural).•Lignin in goat willow biomass could hinder the formation of formic acid by bypath reaction to humin (or pseudo-lignin) formation.•Xylan in avicell cellulose promoted the formation of formic acid than pure cellulose.•For higher yield of glucose, careful control of second hydrolysis temperature in concentrated sulphuric acid hydrolysis is critical.
Chaotic dynamics appear to be prevalent in short‐lived organisms including plankton and may limit long‐term predictability. However, few studies have explored how dynamical stability varies through ...time, across space and at different taxonomic resolutions. Using plankton time series data from 17 lakes and 4 marine sites, we found seasonal patterns of local instability in many species, that short‐term predictability was related to local instability, and that local instability occurred most often in the spring, associated with periods of high growth. Taxonomic aggregates were more stable and more predictable than finer groupings. Across sites, higher latitude locations had higher Lyapunov exponents and greater seasonality in local instability, but only at coarser taxonomic resolution. Overall, these results suggest that prediction accuracy, sensitivity to change and management efficacy may be greater at certain times of year and that prediction will be more feasible for taxonomic aggregates.
Time‐varying local stability metrics were examined for plankton time series from 21 sites. We found that local stability metrics often fluctuated seasonally between stable and unstable values, suggesting that prediction accuracy, sensitivity to change and management efficacy may be greater at certain times of year than others. Taxonomic aggregates were more stable and more predictable than finer groupings and showed variation in stability with latitude.
In many regions across the globe, extreme weather events such as storms have increased in frequency, intensity, and duration due to climate change. Ecological theory predicts that such extreme events ...should have large impacts on ecosystem structure and function. High winds and precipitation associated with storms can affect lakes via short‐term runoff events from watersheds and physical mixing of the water column. In addition, lakes connected to rivers and streams will also experience flushing due to high flow rates. Although we have a well‐developed understanding of how wind and precipitation events can alter lake physical processes and some aspects of biogeochemical cycling, our mechanistic understanding of the emergent responses of phytoplankton communities is poor. Here we provide a comprehensive synthesis that identifies how storms interact with lake and watershed attributes and their antecedent conditions to generate changes in lake physical and chemical environments. Such changes can restructure phytoplankton communities and their dynamics, as well as result in altered ecological function (e.g., carbon, nutrient and energy cycling) in the short‐ and long‐term. We summarize the current understanding of storm‐induced phytoplankton dynamics, identify knowledge gaps with a systematic review of the literature, and suggest future research directions across a gradient of lake types and environmental conditions.
Our understanding of ecosystem‐scale responses to storm events is fragmented, and terminological variability in defining a “storm” hinders resolution of generalizable impacts. We provide a comprehensive synthesis of the interactions between physical properties and biological responses in lakes that demonstrates the context‐dependency of storm impacts; lake/watershed attributes and their antecedent conditions mediate the extent to which storms impact lake ecosystems. We develop a framework which conceptualizes how abrupt, storm‐induced changes in the lake environment influence phytoplankton community dynamics through functional traits, identifies current limitations, and highlights several avenues of research to narrow knowledge gaps in synthetic and interdisciplinary ways.
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