Factors influencing the potential mobility and bioavailability of exchangeable ammonium ion in dried lake sediments

Abstract

The effect of drying temperature and oxidation on the level of exchangeable ammonium ion found in sediments has been examined using samples collected from along a polluted creek and from shallow lake bays. The sediments were dried at temperatures between 20°C and 100°C (either in air or under a nitrogen atmosphere), and the ammonium ion content was extracted into 0.1 M KCl prior to analysis using an ion selective electrode. Exposure to air during the drying stage usually resulted in lower ammonium values, while increasing the drying temperature altered the amount of displaceable (i.e. available) ammonium ion extracted, generally in an upward direction. The amount detected (5–25 μ g^?1) varied between sites, and surface sediment values differed from the 10–50 cm core material results. The pH of the extracts varied with the drying temperature used, indicating that the heating process promoted some chemical changes in the test samples. The study has demonstrated that in nutrient level surveys, the analytical data produced can depend greatly on the sample preparation procedure selected. It also indicated the type of changes which could occur when dredged sediments are land dumped.     

Composition of cellulin,the unique chitin-glucan granules of the fungus,Apodachlya sp.

Cellulin granules, the polysaccharide inclusions found uniquely in oomycetous fungi of the order Leptomitales, were isolated from Apodachlya sp. The granules were prepared free of cell wall and cytoplasmic contaminants. Biochemical analyses and X-ray diffraction studies demonstrated that the granules were composed of 60% chitin and 39% glucan consisting of β-1,3-and β-1,6-linked glucose units. A protein content of only 0.1% was attributed to an insignificant amount of cytoplasmic contamination. Isolated granules and those in situ showed no apparent differences in their microscopic form.     

Zur Physiologie der Pollenkeimung bei Corylus avellana: Pollen- und Narbensaugkräfte. Quellungserscheinungen der Kolloide des Pollens

Ohne ZusammenfassungHerrn Dr. A. Frey-Wyssling, Zürich, bin ich für die kritische Durchsicht des Manuskriptes, Herrn Dr. E. Funk, St. Gallen, für Hilfe bei der Volumenberechnung des Protoplasten, Herrn Dr. E. Müller, Schaffhausen, für Beschaffung von Glaskammern, Herrn Dr. 0. Widmer, St. Gallen, für die Herstellung von Zuckerlösungen, Herrn Dr. E. Wieser, St. Gallen, für die mikrophotographischen Aufnahmen und Herrn Prof. Dr, M. Wildi, St. Gallen, für die Durchsicht der englischen Zusammenfassung zu großem Dank verpflichtet.     

A combined CaMKII inhibition and mineralocorticoid receptor antagonism via eplerenone inhibits functional deterioration in chronic pressure overloaded mice

In the diseased and remodelled heart, increased activity and expression of Ca^2+/calmodulin‐dependent protein kinase II (CaMKII), an excess of fibrosis, and a decreased electrical coupling and cellular excitability leads to disturbed calcium homeostasis and tissue integrity. This subsequently leads to increased arrhythmia vulnerability and contractile dysfunction. Here, we investigated the combination of CaMKII inhibition (using genetically modified mice expressing the autocamtide‐3‐related‐peptide (AC3I)) together with eplerenone treatment (AC3I‐Epler) to prevent electrophysiological remodelling, fibrosis and subsequent functional deterioration in a mouse model of chronic pressure overload. We compared AC3I‐Epler mice with mice only subjected to mineralocorticoid receptor (MR) antagonism (WT‐Epler) and mice with only CaMKII inhibition (AC3I‐No). Our data show that a combined CaMKII inhibition together with MR antagonism mitigates contractile deterioration as was manifested by a preservation of ejection fraction, fractional shortening, global longitudinal strain, peak strain and contractile synchronicity. Furthermore, patchy fibrosis formation was reduced, potentially via inhibition of pro‐fibrotic TGF‐β/SMAD3 signalling, which related to a better global contractile performance and a slightly depressed incidence of arrhythmias. Furthermore, the level of patchy fibrosis appeared significantly correlated to eplerenone dose. The addition of eplerenone to CaMKII inhibition potentiates the effects of CaMKII inhibition on pro‐fibrotic pathways. As a result of the applied strategy, limiting patchy fibrosis adheres to a higher synchronicity of contraction and an overall better contractile performance which fits with a tempered arrhythmogenesis.     

Influence of Polymer Aggregation and Liquid Immiscibility on Morphology Tuning by Varying Composition in PffBT4T‐2DT/Nonfullerene Organic Solar Cells

The temperature‐dependent aggregation behavior of PffBT4T polymers used in organic solar cells plays a critical role in the formation of a favorable morphology in fullerene‐based devices. However, there is little investigation into the impact of donor/acceptor ratio on morphology tuning, especially for nonfullerene acceptors (NFAs). Herein, the influence of composition on morphology is reported for blends of PffBT4T‐2DT with two NFAs, O‐IDTBR and O‐IDFBR. The monotectic phase behavior inferred from differential scanning calorimetry provides qualitative insight into the interplay between solid–liquid and liquid–liquid demixing. Transient absorption spectroscopy suggests that geminate recombination dominates charge decay and that the decay rate is insensitive to composition, corroborated by negligible changes in open‐circuit voltage. Exciton lifetimes are also insensitive to composition, which is attributed to the signal being dominated by acceptor excitons which are formed and decay in domains of similar size and purity irrespective of composition. A hierarchical morphology is observed, where the composition dependence of size scales and scattering intensity from resonant soft X‐ray scattering (R‐SoXS) is dominated by variations in volume fractions of polymer/polymer‐rich domains. Results suggest an optimal morphology where polymer crystallite size and connectivity are balanced, ensuring a high probability of hole extraction via such domains.     

Toward an understanding of broad-scale patterns of the habitat suitability of fountain grass (Cenchrus setaceus (Forssk.) Morrone,Poaceae)

Plant Ecology - Understanding the factors contributing to the introduction and spread of invasive species is crucial to help develop management strategies to control and eradicate them in sensitive...     

Influence of temperature on the δ13C values and distribution of methanotroph‐related hopanoids in Sphagnum‐dominated peat bogs

Methane emissions from peat bogs are mitigated by methanotrophs, which live in symbiosis with peat moss (e.g. Sphagnum). Here, we investigate the influence of temperature and resultant changes in methane fluxes on Sphagnum and methanotroph‐related biomarkers, evaluating their potential as proxies in ancient bogs. A pulse‐chase experiment using ¹³C‐labelled methane in the field clearly showed label uptake in diploptene, a biomarker for methanotrophs, demonstrating in situ methanotrophic activity in Sphagnum under natural conditions. Peat cores containing live Sphagnum were incubated at 5, 10, 15, 20 and 25°C for two months, causing differences in net methane fluxes. The natural δ¹³C values of diploptene extracted from Sphagnum showed a strong correlation with temperature and methane production. The δ¹³C values ranged from ?34‰ at 5°C to ?41‰ at 25°C. These results are best explained by enhanced expression of the methanotrophic enzymatic isotope effect at higher methane concentrations. Hence, δ¹³C values of diploptene, or its diagenetic products, potentially provide a useful tool to assess methanotrophic activity in past environments. Increased methane fluxes towards Sphagnum did not affect δ¹³C values of bulk Sphagnum and its specific marker, the C₂₃ n‐alkane. The concentration of methanotroph‐specific bacteriohopanepolyols (BHPs), aminobacteriohopanetetrol (aminotetrol, characteristic for type II and to a lesser extent type I methanotrophs) and aminobacteriohopanepentol (aminopentol, a marker for type I methanotrophs) showed a non‐linear response to increased methane fluxes, with relatively high abundances at 25°C compared to those at 20°C or below. Aminotetrol was more abundant than aminopentol, in contrast to similar abundances of aminotetrol and aminopentol in fresh Sphagnum. This probably indicates that type II methanotrophs became prevalent under the experimental conditions relative to type I methanotrophs. Even though BHP concentrations may not directly reflect bacterial activity, they may provide insight into the presence of different types of methanotrophs.     

When to start and when to stop: Effects of climate on breeding in a multi‐brooded songbird

Climate warming has been shown to affect the timing of the onset of breeding of many bird species across the world. However, for multi‐brooded species, climate may also affect the timing of the end of the breeding season, and hence also its duration, and these effects may have consequences for fitness. We used 28 years of field data to investigate the links between climate, timing of breeding, and breeding success in a cooperatively breeding passerine, the superb fairy‐wren (Malurus cyaneus). This multi‐brooded species from southeastern Australia has a long breeding season and high variation in phenology between individuals. By applying a “sliding window” approach, we found that higher minimum temperatures in early spring resulted in an earlier start and a longer duration of breeding, whereas less rainfall and more heatwaves (days > 29°C) in late summer resulted in an earlier end and a shorter duration of breeding. Using a hurdle model analysis, we found that earlier start dates did not predict whether or not females produced any young in a season. However, for successful females who produced at least one young, earlier start dates were associated with higher numbers of young produced in a season. Earlier end dates were associated with a higher probability of producing at least one young, presumably because unsuccessful females kept trying when others had ceased. Despite larger scale trends in climate, climate variables in the windows relevant to this species’ phenology did not change across years, and there were no temporal trends in phenology during our study period. Our results illustrate a scenario in which higher temperatures advanced both start and end dates of individuals’ breeding seasons, but did not generate an overall temporal shift in breeding times. They also suggest that the complexity of selection pressures on breeding phenology in multi‐brooded species may have been underestimated.