Bulking sludge in biological nutrient removal systems

Bulking sludge problems are commonly reported in biological nutrient removal (BNR) systems. This has led to the general belief that intrinsic BNR conditions favor the growth of undesirable and excessive filamentous bacteria. The present study shows that other factors have a major role in bulking, and not the BNR conditions. These factors have been verified in well-controlled, strictly anoxic-aerobic and strictly anaerobic-aerobic sequencing batch reactor systems. The experimental results show that conditions known to be responsible for bulking sludge in aerobic systems (i.e., low concentration of electron donor and/or electron acceptor) did not lead to bulking. Even when acetate was present at very low concentrations in the aerobic stage of an anaerobic-aerobic bio-P system, the sludge settleability remained very good. This clearly demonstrates that good bio-P activity can stabilize and improve sludge settleability. The presence of microaerophilic conditions in the anoxic stage of the anoxic-aerobic system was the only factor leading to worsening sludge settling characteristics. The results are discussed in light of our previous hypothesis about the importance of diffusion-limited substrate uptake for the development of filamentous structures in biological flocs. The hypothesis is extended to anaerobic-aerobic and anoxic-aerobic conditions, typical of BNR-activated sludge systems. Taking into account the effect of feeding patterns on biochemical rates and on the development of filamentous bacterial structures, we recommend the adoption of plug-flow selector configurations, with strictly anaerobic and/or strictly anoxic conditions, wherein microaerophilic conditions are excluded, in order to maintain reliable and robust BNR performance.     

Penicillium rubens germination on desiccated and nutrient-depleted conditions depends on the water activity during sporogenesis

Fungal growth often appears in a surrounding where water and nutrients are scarce. The impact of this environment during sporogenesis on subsequent growth is often neglected.This study investigates the effect of water availability during sporogenesis on subsequent early growth. Therefore, a carbon-depleted substrate was constructed. Humidity is then the only parameter of interest. The water conditions during sporogenesis, and during subsequent growth, were varied. This is a stressing environment: no carbon source is present, and water provided solely via the vapour.The lag time, $t_l$, and initial growth rate, ${\mu }_{fp}$, of the germ tubes were monitored.The effect of $a_w$ history on germination and initial growth depends on the $RH$ of the environment. Only at low $RH$ do spores produced at low $a_w$ have a smaller $t_l$ and higher ${\mu }_{fp}$ compared to those grown at high $a_w$. This result was remarkably pronounced when the substrate was also made hydrophobic: growth only occurred when spores were developed at low $a_w$ and placed in high $RH$.Spores grown on lowered $a_w$ attract more water. It is hypothesized that this attraction affects subsequent growth behaviour, and is the reason why growth on hydrophobic glass only prevails in the condition of high $RH$ and lowered $a_w$ history.We demonstrate the influence of cultivation conditions on germination, which becomes more pronounced in a more desiccated environment.     

腐植酸生产菌株——链霉菌发酵条件研究

利用链霉菌ST菌株发酵生产腐植酸。在蔗渣发酵培养基的基础上,采用一次回归正交试验,对腐植酸发酵过程中接种量（I）、通气量（搅拌次数,A）、温度（T）及时间（D）4个因素对腐植酸产量的影响情况进行分析。结果表明发酵时间的影响最为显著,接种量影响显著;所得到的回归方程有效且可信度高,回归方程为Y=6．0356＋0．02501＋0．0033A＋0．0069T＋0．2425D,其中各因素均与腐植酸产量呈正相关性。该回归方程为腐植酸生产过程链霉菌ST菌株发酵条件的控制提供了很好的指导作用。     

Mechanisms of Glycine Release in Mouse Brain Stem Slices

In the brain stem glycine is associated with multiple sensory and visceral regulations, being involved in, for instance, cardiovascular, respiratory and auditory functions. We here studied the mechanisms of the release of preloaded [³H]glycine from mouse brain stem slices in a superfusion system. A depolarizing concentration of K⁺ ions (50 mM) evoked glycine release, but in the absence of Ca²⁺ the effect was attenuated, indicating that a part of the evoked release represents Ca²⁺-dependent exocytosis. The Ca²⁺-independent release was enhanced by omission of Na⁺ and Cl⁻. The stimulatory effect of extracellular glycine confirmed the involvement of transporters functioning in a reverse direction. A part of the release is mediated by Na⁺ and Cl⁻ channels, since it was inhibited by the inhibitors of these, riluzole and 4-acetamido-4′-isothiocyanostilbene-2,2′-disulphonate, respectively. Glycine release was potentiated by the activation of protein kinase C and diminished by increasing cyclic guanosine monophosphate levels with a phosphodiesterase inhibitor, zaprinast. The release was also modulated by the phospholipase inhibitor quinacrine and the tyrosine kinase inhibitor genistein. Adenosine A₁ receptors likewise regulate glycine release, since it was enhanced by their agonist R(−)N⁶-(2-phenylisopropyl)adenosine, which effect was blocked by the antagonist 8-cyclopentyl-1,3-dipropylxanthine. The ionotropic glutamate receptor agonists N-methyl-d-aspartate, kainate and 2-amino-3-hydroxy-5-methyl-4-isoxazolepropionate failed to have any effects contrary to their effects in higher brain regions, e.g., in the hippocampus. The group I and III metabotropic glutamate receptor agonists (S)-3,5-dihydroxyphenylglycine and O-phospho-l-serine, respectively, increased the release in a receptor-mediated manner. Glycine release in the brain stem was also markedly enhanced by cell-damaging conditions, including hypoxia, hypoglycemia and ischemia.     

Controllers for imposing continuum-to-molecular boundary conditions in arbitrary fluid flow geometries

We present a new parallelised controller for steering an arbitrary geometric region of a molecular dynamics (MD) simulation towards a desired thermodynamic and hydrodynamic state. We show that the controllers may be applied anywhere in the domain to set accurately an initial MD state, or solely at boundary regions to prescribe non-periodic boundary conditions (PBCs) in MD simulations. The mean molecular structure and velocity autocorrelation function remain unchanged (when sampled a few molecular diameters away from the constrained region) when compared with those distributions measured using PBCs. To demonstrate the capability of our new controllers, we apply them as non-PBCs in parallel to a complex MD mixing nano-channel and in a hybrid MD continuum simulation with a complex coupling region. The controller methodology is easily extendable to polyatomic MD fluids.     

Influence of environmental factors on content and composition of essential oil from common juniper ripe berry cones (Juniperus communis L.)

Abstract

The present study evaluated the influence of some environmental factors on the quantity and composition of essential oil (EO) in ripe berry cones of Juniperus communis L. The berry cones were collected from juniper shrubs growing wild at five localities of north-east Slovakia during the years 2012–2014. The EO yield ranged from 0.4 to 1.9%, depending on the locality and year. In the EO, eight monoterpenes (α-pinene, β-pinene, β-myrcene, sabinene, limonene, terpinene-4-ol, borneol, bornylacetate) and one sesquiterpene (β-caryophyllene) were identified. The dominant component was the monoterpene α-pinene, ranging from 31.0 to 49.0%. The amount and composition of the EO was affected by soil composition (content of humus and pH) and topographic environmental factors, including air temperature and precipitation. According to the composition of the EO, the studied juniper shrubs belong to the α-pinene chemotype.     

Pathogenic fungal dynamics in a fall population of the blackmargined aphid (Monellia caryella)

A fall population of the blackmargined aphid, Monellia caryella (Fitch) (Homoptera: Aphididae), was monitored daily for mortality caused by fungi and parasitoids. Three species of Entomophthorales fungi were found. Fungal-induced mortality was found to be correlated with minimum temperature. During the period when the minimum temperature was consistently above 8°C, fungal-induced mortality was positively correlated with the sum of hours of leaf-wetness on days 5, 6, and 7 before sampling. Parasitoid wasps killed fewer hosts than fungi and were not affected by environmental factors.

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Résumé La mortalité quotidienne provoquée par des parasitoïdes et des champignons sur une population automnale de M. caryella Fitch (Homopt. Aphididae) a été suivie à Byron (Géorgie, USA), avec enregistrement de la température, de la pluie et de l'humidité des feuilles. 3 espèces de champignons entomophthorales ont été trouvées: Neozygites sp., Entomophthora planchoniana et Erynia sp. 54% des pucerons morts étaient contaminés par Neozygites et 46% par E. planchoniana. Seuls 2 pucerons avaient été tués par Erynia sp. Les taux de mortalité quotidienne par champignons s'élevaient après les périodes pluvieuses et d'humidité des feuilles. La mortalité due au parasitisme était inférieure à la mortalité due aux champignons et ne semblait pas liée aux conditions écologiques. La discussion porte sur l'importance de la mortalité provoquée par les champignons sur la dynamique de la population de pucerons.

     

Biological assessment of European lakes: ecological rationale and human impacts

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