Detection of plant virus particles with a capacitive field-effect sensor

Plant viruses are major contributors to crop losses and induce high economic costs worldwide. For reliable, on-site and early detection of plant viral diseases, portable biosensors are of great interest. In this study, a field-effect SiO2-gate electrolyte-insulator-semiconductor (EIS) sensor was utilized for the label-free electrostatic detection of tobacco mosaic virus (TMV) particles as a model plant pathogen. The capacitive EIS sensor has been characterized regarding its TMV sensitivity by means of constant-capacitance method. The EIS sensor was able to detect biotinylated TMV particles from a solution with a TMV concentration as low as 0.025 nM. A good correlation between the registered EIS sensor signal and the density of adsorbed TMV particles assessed from scanning electron microscopy images of the SiO2-gate chip surface was observed. Additionally, the isoelectric point of the biotinylated TMV particles was determined via zeta potential measurements and the influence of ionic strength of the measurement solution on the TMV-modified EIS sensor signal has been studied.

Analytical Equations Applied to the Study of Steel Profiles under Fire According to Different Nominal Temperature-Time Curves

Some analytical methods are available for temperature evaluation in solid bodies. These methods can be used due to their simplicity and good results. The main goal of this work is to present the temperature calculation in different cross-sections of structural hot-rolled steel profiles (IPE, HEM, L, and UAP) using the lumped capacitance method and the simplified equation from Eurocode 3. The basis of the lumped capacitance method is that the temperature of the solid body is uniform at any given time instant during a heat transient process. The profiles were studied, subjected to the fire action according to the nominal temperature–time curves (standard temperature-time curve ISO 834, external fire curve, and hydrocarbon fire curve). The obtained results allow verifying the agreement between the two methodologies and the influence in the temperature field due to the use of different nominal fire curves. This finding enables us to conclude that the lumped capacitance method is accurate and could be easily applied.

Assessment of Concentration of Mineral Oil in Synthetic Ester Based on the Density of the Mixture and the Capacitance of the Capacitor Immersed in It

This research was carried out during the realization of a project with the aim of developing a method of drying cellulose insulation in power transformers by using synthetic ester. Unfortunately, during the drying process, the ester is systematically contaminated with mineral oil, which reduces its water absorption. Information on the oil concentration in the mixture is needed in two cases: when deciding how to treat the mixture, and during the treatment. The article presents two methods: (1) based on the measurement of the mixture density, and (2) based on the measurement of a capacitor immersed in the mixture. The most important scientific achievement of the work is the proof, by way of experiment, of the existence of a relationship between the concentration of mineral oil and (1) the density of the mixture, and (2) the capacity of the capacitor immersed in it. These relations are presented in the form of equations for which the error calculus showed that the uncertainty of measurement for both methods did not exceed 3 p. %. Due to the similar measurement error of both methods, the authors recommend the capacitance method as easier to use, especially online.

Easy Trends to Analyse Structural Profiles: Lumped Capacitance Vs Simplified Equation

This work presents the calculation of the temperature in different cross-sections of structural profiles (IPE, HEM, L and UAP) using the lumped capacitance method and the simplified equation from Eurocode 3 part 1-2. The lumped capacitance method allows the temperature calculation of the solid body at any time instant during the heat transient process, as a constant and uniform value. The simplified equation from Eurocode 3 part 1-2 is a simple model for heat transfer based on the uniformly distributed temperature over the cross-section surface and directly proportional to section factor of the element. Steel profiles have as almost thermal behaviour uniform during the heat transfer process when submitted to fire conditions and the lumped capacitance method allows a great simplification to estimate the temperature field in the element and may be used when Biot number is lower than unity. Therefore, thermal analysis of solids with high thermal conductivity using this method is adequate. For the studied steel profiles, a thermal analysis was also performed using the simplified equation from the Eurocode 3 part 1-2 in order to validate the obtained results from the lumped capacitance method. The results from both methods are presented for discussion and analysis.

Thermal - electrical analogy in dynamic simulations of buildings: Comparison of four numerical solution methods

The lumped capacitance method is widely used in dynamic modelling of buildings. Models differ in complexity, solution methods and ability to simulate transient behaviour of described objects. The paper presents a mathematical description of a simple 1R1C thermal network model of a building zone. Four numerical methods were applied to solve differential equation describing its dynamics. For validation purposes two test cases (600 and 900) from the BESTEST procedure were used. In both cases detailed results were given. Better ability of the simulation model to reproduce transient behaviour of the modelled buildings was noticed in case of the lightweight object (case 600). Annual heating and cooling demand was within the reference range for heavyweight one (case 900). The kind of the computation method had no significant effect on simulation results.