Spores of puffball fungus Lycoperdon pyriforme as a reference standard of stable monodisperse aerosol for calibration of optical instruments

Advanced air quality control requires real-time monitoring of particulate matter size and concentration, which can only be done using optical instruments. However, such techniques need regular calibration with reference samples. In this study, we suggest that puffball fungus (Lycoperdon pyriforme) spores can be utilized as a reference standard having a monodisperse size distribution. We compare the Lycoperdon pyriforme spores with the other commonly used reference samples, such as Al2O3 powder and polystyrene latex (PSL) microspheres. Here we demonstrate that the puffball spores do not coagulate and, thus, maintain the same particle size in the aerosol state for at least 15 minutes, which is enough for instrument calibration. Moreover, the puffball mushrooms can be stored for several years and no agglomeration of the spores occurs. They are also much cheaper than other calibration samples and no additional devices are needed for aerosol generation since the fungal fruiting body acts as an atomizer itself. The aforementioned features make the fungal spores a highly promising substance for calibration and validation of particle size analyzers, which outperforms the existing, artificially produced particles for aerosol sampling. Furthermore, the L. pyriforme spores are convenient for basic research and development of new optical measurement techniques, taking into account their uniform particle size and absent coagulation in the aeroso

Formation of the Steam Phase in Superheated Liquids in the State of Metastable Equilibrium

The results of studies of vaporization processes in liquids in a metastable state were presented. Regularities of heat and mass exchange in thermodynamically unstable liquids (superheated liquids) were considered. A mathematical model of the mutual dynamic effect of boiling drops of a multicomponent liquid was developed with the help of which the level of dynamic effects was estimated from the point of view of possibility of fragmentation of drops of the primary mixture. Accuracy of the known criterion equations for the described homogenization technology was estimated. It was shown that instability of the Rayleigh-Taylor type has the greatest effect on fragmentation of drops.In the study of the velocity and pressure fields, data were obtained that show that in the inter-bubble space of the ensemble, even with monotonically expanding bubbles, there are sharp jumps in pressures and velocities characteristic of the turbulent flow. This type of flow contributes to intensification and stimulation of heat and mass exchange and hydrodynamic processes in the liquid phase of the bubble system.The obtained dependences make it possible to qualitatively assess critical forces sufficient for the thermodynamic fragmentation of the secondary phase. The time and energy parameters necessary for fragmentation of drops were determined. They depend on the temperature and size of the disperse phase. The proposed method for determining basic thermodynamic parameters of superheated liquid and vapor is necessary for predicting energy parameters of the thermodynamic homogenization technology

Development of a New Method for Obtaining Claydite with a Minimal Thermal Conductivity Coefficient

The object of study is the technology of creation of claydite with a minimal coefficient of thermal conductivity. Most problematic is the lack of methods for determining the optimal technological parameters of thermal treatment of raw materials to obtain claydite with a low coefficient of thermal conductivity. The reason for this is that the existing methods are aimed at creating mullite during roasting of the alumina raw materials, as a substance of sufficient strength. Although, when claydite is used as a thermal insulation filling or as an additive to a concrete mixture, a reduction in the coefficient of thermal conductivity in the formation of the structure of claydite is more significant than the strength value. In the course of research, we created a number of experimental samples of claydite at different initial factors. Fire resistance was determined by comparing the behavior of the examined and standard samples when heated. Bulk thermal conductivity was determined by the thermal conductivity meter ITP-MG4 made by SKB Stroypribor, Russia. Strength of the material was determined by the Rockwell method.To determine the optimal technological parameters for the production of claydite from the specified alumina mixture, we used the method of experiment planning and the optimization of the resulting equation employing the Lagrange method with the Kuhn–Tucker conditions. Based on data received, the technology of obtaining claydite with improved thermal-physical properties is as follows. Clay mixture is dried to humidity of 38 % and the granules are formed (by pressing a grid with a cell of 6×20 mm). Next, the pallet with granules is put into a heating furnace for 15 minutes at 270 °C. After the heating furnace, the granules are discharged into a drum furnace, where they are roasted at temperature 1250 °C for 1.5 hours.The results obtained make it possible to reduce the coefficient of thermal conductivity of claydite by 2.25 times. The applied technique could be used for future studies of samples with different additives, including industrial waste. This in turn will allow a more effective use of available raw materials as well as reduction in the cost of product

A mathematical model for evaporation of explosive thin film

Here we develop a mathematical model for evaporation of an explosive thin film. Such an objective stems from the problem of trace explosive detection by techniques based on explosive vapor recording. In particular, we have previously devised an instrumentation system for standoff trace explosive detection by the active spectral imaging method. To determine the applicability limits of remote trace explosive detection methods, one should understand the regularities of evaporation dynamics of an explosive thin film, depending on explosive properties, film geometry (thickness, surface area), and ambient conditions. The mathematical model relies on the Hertz-Knudsen- Langmuir equation for evaporation rate and allows for heat exchange between the surface and ambient gas and for heat loss due to evaporation. The fact that phase transition temperature in a thin film is lower than that in a large volume of an explosive was also taken into account. The parametric study of the model was performed. The basic parameters and their variation range affecting the film evaporation rate were identified. Estimations were done for the substance mass in air during the evaporation of explosive thin films within a wide range of the parameters used. Conclusions were made on the applicability limits of trace explosive detection optical methods