Plasma Membrane Fluidity: An Environment Thermal Detector in Plants

The lipid matrix in cell membranes is a dynamic, bidimensional array of amphipathic molecules exhibiting mesomorphism, which contributes to the membrane fluidity changes in response to temperature fluctuation. As sessile organisms, plants must rapidly and accurately respond to environmental thermal variations. However, mechanisms underlying temperature perception in plants are poorly understood. We studied the thermal plasticity of membrane fluidity using three fluorescent probes across a temperature range of −5 to 41 °C in isolated microsomal fraction (MF), vacuolar membrane (VM), and plasma membrane (PM) vesicles from Arabidopsis plants. Results showed that PM were highly fluid and exhibited more phase transitions and hysteresis, while VM and MF lacked such attributes. These findings suggest that PM is an important cell hub with the capacity to rapidly undergo fluidity modifications in response to small changes of temperatures in ranges spanning those experienced in natural habitats. PM fluidity behaves as an ideal temperature detector: it is always present, covers the whole cell, responds quickly and with sensitivity to temperature variations, functions with a cell free-energy cost, and it is physically connected with potential thermal signal transducers to elicit a cell response. It is an optimal alternative for temperature detection selected for the plant kingdom.

The distortion of images in remote sensing systems at arbitrary angles of sight

Background. The main problem in launching space optical and electronic viewing systems (OEVS) for remote sensing of the Earth can be regarded as their high price, which even the leading countries of the world are not always ready to pay. Therefore, the quality of spacecraft systems imposed the most stringent requirements. One of the economically expedient options to increase the efficiency of space OEVS is scanning the Earth’s surface at arbitrary angles of sighting, which allows for the same time of service life to collect more information, but this in turn leads to image distortion. Therefore, analysis of the resulting image quality depending on the angles of sighting of the OEVS is an actual task that will assess the capabilities of the system and its conformance with the established requirements. Objective. Improving the physical and mathematical model of the modulation transfer function of the system “lens – matrix detector” and the study of the dependence of spatial and radiometric resolution on the angles of sight for the space OEVS when the sighting axis deviates from the nadir. Methods. Based on the analysis of signal generation models for television and thermal imaging space OEVS, it is proposed to use the concept – the contrast gray body. In the physical and mathematical model, it is proposed normalize to the spatial frequencies of objects at different angles of sight to the spatial frequencies in the nadir, and to calculate the radiometric resolution take into account the transmission and rarefied of the atmosphere, the image movement speed on the detector and its integration time. Results. Practical results of calculations of the offered physical and mathematical model for space OEVS showed that at deviation from nadir the effective spatial bandwidth worsens and at the specified parameters of system it is inexpedient scanning at angles of sighting greater than 30º. Accordingly, a comparative analysis of radiometric resolution for different type of detectors showed that the use of a photonic detector gives ~1.4 times better resolution in the nadir as opposed to the use of thermal detector and almost identical results are obtained at maximum angles of sighting. Also, a significant impact is made by a decrease a coefficient of atmospheric transmittance due to the rarefied of the atmosphere, which reaches from 26% to 45% that depends on the spectral range. Conclusions. Analysis of the results of the study confirms the possibility that photonic detectors can be replaced by modern thermal detectors with insignificant loss of image quality of the resulting image, which can significantly increase the service life of space OEVS.

Research on Performance Evaluation and Optimization Theory for Thermal Microscope Imaging Systems

Infrared imaging theory is an important theoretical basis for the design of infrared imaging systems, but there is no research on infrared imaging theory for designing thermal microscope imaging systems. Therefore, we studied the performance evaluation and optimization theory of thermal microscope imaging systems. In this paper, we analyzed the difference in spectral radiant flux between thermal microscope imaging and telephoto thermal imaging. The expression of signal-to-noise ratio of the output image of the thermal microscope imaging systems was derived, based on the analysis of the characteristics of thermal microscope imaging. We studied the performance evaluation model of thermal microscope imaging systems based on the minimum resolvable temperature difference and the minimum detectable temperature difference. Simulation and analysis of different detectors (ideal photon detector and ideal thermal detector) were also carried out. Finally, based on the conclusion of theoretical research, we carried out a system design and image acquisition experiment. The results show that the theoretical study of thermal microscope imaging systems in this paper can provide reference for the performance evaluation and optimization of thermal microscope imaging systems.

Development of Thermal Detector Based on Flexible Film Thermoelectric Module

Thermal detectors find a significant niche in the market of modern sensors. Bi2T3 and PbTe semiconductors are effective thermoelectrics and excellent candidates for different applications. In the present work, a technology for fabrication of p-Bi0.5Sb1.5Te3 and n-PbTe films with the high thermoelectric efficiency on thin flexible polyimide substrate has been developed. The preparation of films was performed by flash evaporation method. The high sensitivity of the devices is due to the high Seebeck coefficient of 200 mV/K and reduction of thermal conductivity of thin thermoelectric film from the bulk value. The devices operate in the Johnson-Nyquist noise limit of the thermocouple. The performance enables fast and sensitive detection of low levels of thermal power and infrared radiation at room temperature.