Simulation of Colloidal Stability and Aggregation Tendency of Magnetic Nanoflowers in Biofluids

A population balance model for the aggregation of iron oxide nanoflowers (IONfs) is presented. The model is based on the fixed pivot technique and is validated successfully for four kinds of aggregation kernels. The extended Derjaguin, Landau, Verwey, and Overbeek (xDLVO) theory is also employed for assessing the collision efficiency of the particles, which is pertinent to the total energy of the interaction. Colloidal stability experiments were conducted on IONfs for two dispersant cases—aqueous phosphate buffered saline solution (PBS) and simulated body fluid (SBF). Dynamic light scattering (DLS) measurements after 24-h of incubation show a significant size increase in plain PBS, whereas the presence of proteins in SBF prevents aggregation by protein corona formation on the IONfs. Subsequent simulations tend to overpredict the aggregation rate, and this can be attributed to the flower-like shape of IONfs, thus allowing patchiness on the surface of the particles that promotes an uneven energy potential and aggregation hindering. In silico parametric study on the effects of the ionic strength shows a prominent dependency of the aggregation rate on the salinity of the dispersant underlying the effect of repulsion forces, which are almost absent in the PBS case, promoting aggregation. In addition, the parametric study on the van der Waals potential energy effect—within common Hamaker-constant values for iron oxides—shows that this is almost absent for high salinity dispersants, whereas low salinity gives a wide range of results, thus underlying the high sensitivity of the model on the potential energy parameters.

Theoretical Analysis of Activation Energy Effect on Prandtl–Eyring Nanoliquid Flow Subject to Melting Condition

This study models the convective flow of Prandtl–Eyring nanomaterials driven by a stretched surface. The model incorporates the significant aspects of activation energy, Joule heating and chemical reaction. The thermal impulses of particles with melting condition is addressed. The system of equations is an ordinary differential equation (ODE) system and is tackled numerically by utilizing the Lobatto IIIA computational solver. The physical importance of flow controlling variables to the temperature, velocity and concentration is analyzed using graphical illustrations. The skin friction coefficient and Nusselt number are examined. The results of several scenarios, mesh-point utilization, the number of ODEs and boundary conditions evaluation are provided via tables.

Strain Compensation and Trade-Off Design Result in Exciton Emission at 306 nm from AlGaN LEDs at Temperatures up to 368 K

In this study, we suppressed the parasitic emission caused by electron overflow found in typical ultraviolet B (UVB) and ultraviolet C (UVC) light-emitting diodes (LEDs). The modulation of the p-layer structure and aluminum composition as well as a trade-off in the structure to ensure strain compensation allowed us to increase the p-AlGaN doping efficiency and hole numbers in the p-neutral region. This approach led to greater matching of the electron and hole numbers in the UVB and UVC emission quantum wells. Our UVB LED (sample A) exhibited clear exciton emission, with its peak near 306 nm, and a band-to-band emission at 303 nm. The relative intensity of the exciton emission of sample A decreased as a result of the thermal energy effect of the temperature increase. Nevertheless, sample A displayed its exciton emission at temperatures of up to 368 K. In contrast, our corresponding UVC LED (sample B) only exhibited a Gaussian peak emission at a wavelength of approximately 272 nm.

Self-energy dynamics and mode-specific phonon threshold effect in a Kekulé-ordered graphene

Electron-phonon interaction and related self-energy are fundamental to both the equilibrium properties and non-equilibrium relaxation dynamics of solids. Although electron-phonon interaction has been suggested by various time-resolved measurements to be important for the relaxation dynamics of graphene, the lack of energy- and momentum-resolved self-energy dynamics prohibits direct identification of the role of specific phonon modes in the relaxation dynamics. Here by performing time- and angle-resolved photoemission spectroscopy measurements on a Kekulé-ordered graphene with folded Dirac cones at the Γ point, we have succeeded in resolving the self-energy effect induced by coupling of electrons to two phonons at Ω1 = 177 meV and Ω2 = 54 meV and revealing its dynamical change in the time domain. Moreover, these strongly coupled phonons define energy thresholds, which separate the hierarchical relaxation dynamics from ultrafast, fast to slow, thereby providing direct experimental evidence for the dominant role of mode-specific phonons in the relaxation dynamics.

Application of Minimum Energy Effect to Numerical Reconstruction of Insolation Curves

Increasing the efficiency of the solar energy harvesting system is an urgent need in light of the climate changes we live in nowadays. The most significant data to be processed in the photovoltaic harvesters are the curve of solar radiation intensity to achieve the maximum benefits of the solar incident light. This processing contains complicated procedures, and the used algorithms are also high computational power-consuming which makes using special software and high potential hardware essential requirements. An explanation of the Minimum Energy Effect method is presented in this article. Our proposed algorithm uses this method to provide a simple and high-accuracy mathematical tool for generating a simple alternative curve instead of the complicated original nonlinear curve of solar radiation intensity. The produced curve is suitable for further operations, such as derivatives, integrals, or even simple addition/subtraction. Our algorithm provides a gradual procedure to find an optimum solution of the equation system, unlike the iterative methods. In addition, the results of analyzing the effect of time-division density showed the relationship between the speed of solving the task and the accuracy of results.

Medical and biological bases of safety

The textbook considers the subject and tasks of the discipline, highlights the medical and biological foundations of ensuring human security in the conditions of natural, man-made and biological-social emergencies, as well as when using modern weapons of destruction by a probable enemy. Briefly, but quite informative, the structure of the human body and the basics of its functioning are described. The specificity and mechanism of the toxic effect of harmful substances on a person, the energy effect and the combined effect of the main damaging factors of the sources of emergency situations of peacetime and wartime are shown. The article highlights the medical and biological aspects of ensuring the safe life of people in adverse environmental conditions, including in regions with hot and cold climates (the Arctic). The methods of forecasting and assessing the medical situation in emergency zones and lesions are presented. The means and methods of medical and biological protection and first aid to the affected are shown. The main tasks and organizational structure of formations and institutions of the medical rescue service of the GO, the All-Russian Service of Disaster Medicine and medical formations of the EMERCOM of Russia are considered. Organizational issues of medical and biological protection in emergency situations are highlighted. The features of the organization of medical support for those affected by terrorist attacks are considered. It is intended for students and cadets of educational institutions of higher education studying under the bachelor's degree program in the following areas of training: "Technosphere security", "Infocommunication technologies and communication systems", "Information systems and technologies", "State and municipal management", "Economics", "Mechatronics and robotics", "Operation of transport and technological machines and complexes", "Informatics and computer engineering", "Air Navigation", "System analysis and management". It can also be useful for researchers and a wide range of specialists engaged in practical work on planning and organizing medical and biological protection of the population.