Competition between benthic cyanobacteria and diatoms as influenced by different grain sizes and temperatures

An experimental laboratory set-up was used to study the influence of different grain size compositions and temperatures on the growth of benthic cyanobacteria and diatoms, and on the competition between these 2 groups. Monospecific cultures of 3 species of cyanobacteria (Merismopedia punctata, Microcoleus chthonoplastes, Oscillatoria limosa), and of 2 species of benthic diatoms (Phaeodactylum tricornutum and Nitzschia sp.) were used. The organisms were cultured in 100 ml flasks filled with medium and 3 different kinds of sediment: (1) Sand (fine sand, 63 to 200 µm), (2) Mud-I (mixed fine sand and mud <63 µm in the ratio 80:20 wt %), (3) Mud-II (mixed fine sand and mud in the ratio 50:50 wt %). Experimental temperatures were 10, 15 and 25°C. At 10°C and 15°C, both diatom species achieved the highest biomass on the sediments of the finest grain size (50 wt % < 63 µm) while cyanobacteria achieved low biomass levels. Coarsening of sediments at the same temperature levels revealed a gradually lower biomass of the diatoms. Particularly on sand, the diatoms never reached the same concentrations of chlorophyll a as on mud. The cyanobacteria, on the other hand, had the highest biomass on sand at 15°C. In the competition experiments the benthic diatom species Nitzschia sp. dominated all types of sediments at 10°C and 15°C. The experiments at 25°C were dominated by the filamentous cyanobacterium M. chthonoplastes. This indicates the importance of abiotic conditions for the distribution and abundance of benthic phototrophic micro-organisms

Reliable lift-off patterning of graphene dispersions for humidity sensors

Dispersion-based graphene materials are promising candidates for various sensing applications. They offer the advantage of relatively simple and fast deposition via spin-coating, Langmuir-Blodgett deposition, or inkjet printing. Film uniformity and reproducibility remain challenging in all of these deposition methods. Here, we demonstrate, characterize, and successfully apply a scalable structuring method for graphene dispersions. The method is based on a standard lift-off process, is simple to implement, and increases the film uniformity of graphene devices. It is also compatible with standard semiconductor manufacturing methods. We investigate two different graphene dispersions via Raman spectroscopy and Atomic Force Microscopy and observe no degradation of the material properties by the structuring process. Furthermore, we achieve high uniformity of the structured patterns and homogeneous graphene flake distribution. Electrical characterizations show reproducible sheet resistance values correlating with material quantity and uniformity. Finally, repeatable humidity sensing is demonstrated with van der Pauw devices, with sensing limits of less than 1% relative humidity.Comment: 35 page

Reliable Compact Models for the Investigation of Acoustic High-Frequency Effects in MEMS Transducers

We present a fully coupled multi-energy domain compact model of a MEMS microphone dedicated to the investigation of acoustic high-frequency effects affecting the device behavior. To this end, the components of the acoustic domain are described using physics-derived analytical expressions. Finite element simulations are employed to confirm the validity of the acoustic submodel. The differential equations governing the small-signal dynamics of the electrically actuated transducer are solved in the frequency domain with MATLAB. The full-system model is calibrated and validated with experimental data. Measurements and simulations show very good agreement, which highlights the reliability of the presented modeling approach

Development of Graphene Based Inks for Deposition via Inkjet Printing for Sensing Application

In this work we investigate and optimize graphene based inks to achieve a stable and well-controllable jetting behavior using a DoD (Drop on Demand) inject printer which has all the required characteristics of a tool for mass production

Reliable Lift‐Off Patterning of Graphene Dispersions for Humidity Sensors

Abstract Dispersion‐based graphene materials are promising candidates for various sensing applications. They offer the advantage of relatively simple and fast deposition via spin‐coating, Langmuir–Blodgett deposition, or inkjet printing. Film uniformity and reproducibility remain challenging in all of these deposition methods. Here, a scalable structuring method is demonstrated, characterized, and successfully applied for graphene dispersions. The method is based on a standard lift‐off process, is simple to implement, and increases the film uniformity of graphene devices. It is also compatible with standard semiconductor manufacturing methods. Two different graphene dispersions are investigated via Raman spectroscopy and Atomic Force Microscopy and observe no degradation of the material properties by the structuring process. Furthermore, high uniformity of the structured patterns and homogeneous graphene flake distribution is achieved. Electrical characterizations show reproducible sheet resistance values correlating with material quantity and uniformity. Finally, repeatable humidity sensing is demonstrated with van der Pauw devices, with sensing limits of less than 1% relative humidity

Thermokarst Processes and Depositional Events in a Tundra Lake, Northeastern Siberia

The relationships between thermokarst activity, limnogeological processes and climate change in the Siberian Arctic are not well understood. The objective of this paper is to identify the factors controlling the patterns of deposition, using grain-size distributions, organic contents, elemental compositions and mineralogical compositions of a 137-cm-long sediment core with a maximum age of ~10.9 cal. kyr BP from Lake El’gene-Kyuele, in the tundra of north-eastern Siberia. Eight fine sand layers are attributed to depositional events associated with thaw slump activity acting upon orthogonally oriented patterns of the ice-wedge networks in the ice-rich permafrost on the NW margin of the lake catchment. Sr/Rb ratios, which correspond to the total feldspar and illite content, serve as high-resolution grain-size proxies. The Br content relates to the total organic carbon (TOC) content, and the Fe/Mn ratio reflects the degree of oxidisation. Our results indicate a relationship between repeated phases of fine sand input and retrogressive thaw slumping dependent on hydroclimate variability and orthogonally oriented ice-wedge networks within the catchment