Microscale solute flow probed with rotating microbead trapped in optical vortex

The dynamics of solute flow in the microscopic chamber can be studied with optical tweezers. A method based on the metallic microbeads trapped in the focused optical vortex beam is proposed. This annular beam of a twisted wavefront exerts torque on a reflective object placed inside the dark core of the vortex. The induced rotational movement of the bead is sensitive to local viscosity changes in the surrounding medium, for example, during the ongoing dissolution process. Two experimental configurations are described, both relying on tracing the angular velocity of the bead in time. In one-bead configuration, the dynamics of local solute concentration can be studied. In two-bead case, the direction and speed of solute flow can be probed with a spatial resolution of single micrometers. We approach the elementary problem of sucrose dissolution and diffusion in water. The surprising impression of the reverse solute flow was observed. Further experimental investigation led to the discovery that this phenomenon originates from the sucrose stream-like diffusion in the mid-depth of the measurement chamber. The rotating microbead method applies for various solid and liquid substances and may become a useful technique for microfluidics research. Graphic abstract

High frequency measurements reveal distinct sources of shoot methane emissions.

<p>Plant shoots can emit methane (CH<sub>4</sub>) from multiple source processes (microbial methanogenesis in soils and core wood, aerobic CH<sub>4</sub> production in foliage). We constructed a chamber system to isolate these processes and study how leaf level CH<sub>4</sub> emissions respond to environmental factors like dark-light-cycles, temperature, drought, or CO<sub>2</sub> concentrations. Tree samplings are located in a FITOCLIMA D 1200 plant growth chamber for PAR, temperature and humidity control and equipped with a measurement chamber to quantify CH<sub>4</sub> exchange in a closed loop setup with a Picarro G2301 CH<sub>4</sub> analyser. The system was further customized to control temperature, CO<sub>2</sub>, and humidity in the measurement chamber. The system allows the detection of CH<sub>4</sub> flux rates of on the order of 1 nmol CH<sub>4</sub> h<sup>-1</sup> and can conduct high frequency (< 15 min) measurements of CH<sub>4</sub> emissions rates from small shoots (<5g foliage biomass). Initial measurements were conducted with Scots pine and birch saplings. In addition, we measured conducted manual methane flux measurements on shoots of Scots pine saplings in two 24-hour campaigns.</p><p>These experiments demonstrated that the shoots of different tree species emit CH<sub>4</sub> from distinct sources. Scots pine shoots emitted CH<sub>4</sub> produced within the shoot, likely through aerobic CH<sub>4</sub> production, which showed a strong diurnal cycles that follows irradiation and photosynthesis rates. Shoot from some birch species, in contrast, showed emissions of soil-borne CH<sub>4</sub> that remained constant throughout day and nighttime. We expect that future experiment with this unique setup will allow to further disentangle shoot CH<sub>4</sub> emissions and characterize their response to environmental conditions including light, temperature, and relative humidity.</p>

Towards an understanding of surface effects: testing of various materials in a small volume measurement chamber and its relevance for atmospheric trace gas analysis

A critical issue for the long-term monitoring of atmospheric trace gases is precision and accuracy of the measurement systems employed. Both measuring and preparing reference gas mixtures for trace gases are challenging due to, for example, adsorption and desorption of the substances of interest on surfaces; this is particularly critical at low amount fractions and/or for reactive gases. Therefore, to ensure the best preparation and measurement conditions for trace gases in very low amount fractions, usage of coated materials is in demand in gas metrology and atmospheric measurement communities. This study focuses on testing potential adsorption and desorption effects for different materials or coatings that are currently used or that may be relevant in the future for the measurements of greenhouse gases. For this study we used small volume chambers designed to be used for adsorption studies. Various materials with or without coatings were loaded into the small cylinder to test their adsorption and desorption behavior. We used the aluminum cylinder as the measurement chamber and glass, aluminum, copper, brass, steel and three different commercially available coatings as test materials. Inserting the test materials into the measurement chamber doubles the available geometric area for the surface processes. The presented experiments were designed to investigate the pressure dependency of adsorption up to 15 bar and its temperature dependency up to 80 ∘C for the test materials placed in the measurement chamber. Here, we focused on the species CO2, CH4, CO and H2O measured by a cavity ring-down spectroscopy analyzer. Our results show that the materials currently used in atmospheric measurements are well suited. The investigated coatings were not superior to untreated aluminum or to stainless steel at the tested pressure ranges, whereas under changing temperature aluminum showed better performance for CO2 (<0.05 µmol mol−1 change in measured amount fractions) than stainless steel (>0.1 µmol mol−1). To our knowledge, this study is one of the first attempts to investigate surface effects of different materials in such a setup for the abovementioned gases.

Measurement Chamber Design for Testing Batteries of the Electric Vehicles

Crucial factors with respect to modern autonomous vehicles include reliability and design. Researchers and engineers strive to increase the number of vehicles over the latest possibilities both in industrial and in military applications. A number of modern batteries are available on the market for the electric autonomous vehicles. The authors suggest the use of test chambers to investigate optimal battery use and performance in vehicles. The results of the theoretical research suggest that the use of test chambers during battery management system development is necessary.

Towards an understanding of surface effects: Testing of various materials in a small volume measurement chamber and its relevance for atmospheric trace gas analysis

A critical issue for the long-term monitoring of atmospheric trace gases is precision and accuracy of the measurement systems employed. To ensure the best preparation and measurement conditions for trace gases in very low amount fractions, usage of coated materials is in demand in gas metrology and atmospheric measurement communities. This study focuses on the testing of different materials or coatings that are currently used, or may be relevant in future for the measurements of greenhouse gases. For this study, we used the previously tested small volume cylinders, which were constructed such that they can serve as adsorption test chambers. Various materials with or without coatings were loaded into the small cylinder to test their adsorption/desorption behavior. We used the aluminum cylinder as the measurement chamber, and glass, aluminum, copper, brass, steel and three different commercially available coatings as test materials. Inserting the test materials into the measurement chamber doubles the available geometric area for the surface processes. The presented experiments were designed to investigate the pressure dependency up to 15 bar, and temperature dependency up to 80 °C for the test materials placed in the measurement chamber. Here, we focused on the species CO2, CH4, CO and H2O measured by a cavity ring down spectroscopy analyzer. Our results show that the materials currently used in atmospheric measurements are well-suited. The investigated coatings were not superior to untreated aluminum or to stainless steel at the tested pressure ranges, whereas under changing temperature aluminum showed better performance for CO2 (< 0.05 μmol mol−1 change in measured amount fractions) than stainless steel (> 0.1 μmol mol−1). To our knowledge, this study is one of the first attempts to investigate surface effects of different materials in such a setup for the above-mentioned gases.

On the Reconstruction Capability of the Linear Sampling Method

<p>Linear Sampling Method (LSM), although a simple and fast qualitative method, encounters some limitations and restrictions when it comes to measurement set-up and realistic implementation. Addressing some difficulties arising from somewhat complicated measurement structures used to gather raw data for the reconstruction algorithm, this communication tries to show the effect of mutual coupling between antennas utilized in the measurement chamber. Another tangible effect of the antenna arrangement, covered here through reconstructing a reference scenario of Fresnel Institute dataset, has to do with the aspect-limited nature of scan lines. Reconstructions based on both simulated and measured data are reported.</p>