Characteristics and turnover of exopolymeric substances in a hypersaline microbial mat

The properties and microbial turnover of exopolymeric substances (EPS) were measured in a hypersaline nonlithifying microbial mat (Eleuthera, Bahamas) to investigate their potential role in calcium carbonate (CaCO3) precipitation. Depth profiles of EPS abundance and enzyme activities indicated that c. 80% of the EPS were turned over in the upper 15-20 mm. Oxic and anoxic mat homogenates amended with low-molecular-weight (LMW) organic carbon, sugar monomers, and different types of EPS revealed rapid consumption of all substrates. When comparing the consumption of EPS with that of other substrates, only marginally longer lag times and lower rates were observed. EPS (5-8%) were readily consumed during the conversion of labile to refractory EPS. This coincided with a decrease in glucosidase activity and a decrease in the number of acidic functional groups on the EPS. Approximately half of the calcium bound to the EPS remained after 10 dialyses steps. This tightly bound calcium was readily available to precipitate as CaCO3. We present a conceptual model in which LMW organic carbon complexed with the tightly bound calcium is released upon enzyme activity. This increases alkalinity and creates binding sites for carbonate and allows CaCO3 to precipitate. Therefore, this model explains interactions between EPS and CaCO3 precipitation, and underscores the critical role of aerobic and anaerobic microorganisms in early diagenesis and lithification processe

Preparation of SnO2 thin films for photovoltaic electrode materials using sol-gel method

Celem przeprowadzonych badań było otrzymanie cienkich warstw SnO2 na powierzchniach szklanych przy użyciu techniki zol-żel, z zastosowaniem organicznych związków cyny. Warstwy otrzymywano przez nanoszenie zolu SnO2 w metanolu techniką dip coating. Otrzymana warstwa była następnie poddawana kalcynacji w atmosferze utleniającej. Otrzymano serię materiałów zawierających od 1. do 12. warstw SnO2 na powierzchni podłoża szklanego. Uzyskane warstwy poddano charakterystyce za pomocą techniki XRD, SEM, SEM-EDS, UV/VIS. Równolegle przeprowadzono badania czasowo-rozdzielcze procesu schnięcia warstwy z wykorzystaniem techniki FT-IR (ATR).The aim of the study was to obtain SnO2 thin films on glass using a sol-gel technique and organic tin compounds. The layers were prepared by dip coating deposition of SnO2 sol in methanol. The resulting layer was then subjected to a process of calcining in an oxidizing atmosphere. To give a series of materials comprising from one to twelve layers of SnO2 on the surface of the glass substrate. The obtained film was subjected to characterization by XRD, SEM, SEM-EDS and UV-Vis technique. Above that time-resolved tests of the layer drying process using the technique of FT-IR (ATR) were carried out