Numerical study on the dynamics of a jet-vortex interaction

The interaction of a vortex and a jet plays an important role for many industrial processes such as carbon black formation or combustion in diesel engines. The knowledge of physics of these phenomena is crucial for engineers, but also for scientists who wish to study this complex flow pattern. In this research, we numerically investigate cases where a cylindrical reactor is charged with gas injected through five ports. The first one is located along the main axis of the cylinder and this leads to the formation of the main jet. The other four ports are situated along the side walls such that the gas entering the cylinder tangentially through them causes a vortex to be formed. The objective of this paper is to show the fundamental physical phenomena and also how the initial and boundary conditions influence the results. It is shown how the process is influenced not only by modifying the velocity of injected gas, but also by the orientation and position of the vortex inlet nozzles.     

Superparamagnetic magnetite–divinylbenzene–maleic anhydride copolymer nanocomposites obtained by dispersion polymerization

Magnetite alternating copolymers divinylbenzene–maleic anhydride (DVB–MA) composites were prepared by dispersion polymerization. Because magnetite is used as a complex with oleic acid (Fe₃O₄OLA), the final hybrids show good dispersion of inorganic nanofillers in the polymer matrix. The obtained composites were analyzed by infrared absorption spectrometry, diffuse reflectance in visible light, thermogravimetry, X-ray fluorescence, X-ray diffraction, dynamic light scattering, scanning electron microscopy and vibrating sample magnetometry. The obtained results indicate the successful preparation of magnetite nanoparticles with an average size of about 23 nm dispersed in micrometer size copolymer spherical particles, which relative content can be controlled via the processing parameters. A relationship between the relative content of magnetite nanoparticles and the size of the polymer particles, with direct influence on the diffuse reflectance in the visible domain, was observed. A superparamagnetic behavior was evidenced at room temperature with a blocking temperature lower than as expected from the bulk anisotropy constant and the average size of the magnetite nanoparticles. Both the unexpected low blocking temperature and the observed low specific magnetizations were explained by a defected and poor crystalline structure of the magnetite nanoparticles, giving rise to spin disorder and diminished crystalline anisotropy constant.     

Continuum description of the cytoskeleton: ring formation in the cell cortex

Motivated by the formation of ringlike filament structures in the cortex of plant and animal cells, we study the dynamics of a two-dimensional layer of cytoskeletal filaments and motor proteins near a surface by a general continuum theory. As a result of active processes, dynamic patterns of filament orientation and density emerge via instabilities. We show that self-organization phenomena can lead to the formation of stationary and oscillating rings. We present state diagrams that reveal a rich scenario of asymptotic behaviors and discuss the role of boundary conditions.     

Monitoring biological membrane-potential changes: a CI QM/MM study

In recent decades, new less-invasive, nonlinear optical methods have been proposed and optimized for monitoring fast physiological processes in biological cells. One of these methods allows the action potential (AP) in cardiomyocytes or neurons to be monitored by means of second-harmonic generation (SHG). We now present the first, to our knowledge, simulations of the dependency of the intensity of the second harmonic (I(SHG)) on variations of the transmembrane potential (TMP) in a cardiomyocyte during an action potential (AP). For this, an amphiphilic potential-sensitive styryl dye molecule with nonlinear optical properties was embedded in a dipalmitoylphosphatidylcholine (DPPC) bilayer, replacing one of the phospholipid molecules. External electrical fields with different strengths were applied across the membrane to simulate the AP of a heart-muscle cell. We used a combined classical/quantum mechanical approach to model the structure and the spectroscopic properties of the embedded chromophore. Two 10 ns molecular dynamics (MD) simulations provided input geometries for semiempirical molecular orbital (QM/MM) single-point configuration interaction (CI) calculations, which were used to calculate the wavelengths and oscillator strengths of electronic transitions in the di-8-ANEPPS dye molecule. The results were then used in a sum-over-states treatment to calculate the second-order hyperpolarizability. The square of the hyperpolarizability scales with the intensity of the second harmonic, which is used to monitor the action potentials of cardiomyocytes experimentally. Thus, we computed changes in the intensity of the second harmonic (DeltaI(SHG)) as function of TMP changes. Our results agree well with experimental measurements.     

Silver doping in lanthanum manganite materials: structural and electrical properties

Journal of Thermal Analysis and Calorimetry - Porous media are very useful tools used for energy management. They are used in vast fields such as in solar heat exchangers to enhance heat transfer...     

Thermal and mechanical behavior of biodegradable polyester films containing cellulose nanofibers

Journal of Thermal Analysis and Calorimetry - Agricultural waste is a valuable source of advanced materials. Cheap nanocellulose may be obtained from plum shells agricultural residues and further...