Theoretical background of the hybrid VπLES method for flows with variable transport properties

The paper presents the theoretical basis for the extension of the V π LES method, originally developed in recent works of the authors for incompressible flows, to flows with variable density and transport properties but without chemical reactions. The method is based on the combination of grid based and grid free computational particle techniques. Large scale motions are modelled on the grid whereas the fine scale ones are modelled by particles. The particles represent the fine scale vorticity, and scalar quantities like e.g., temperature, mass fractions of species, density and mixture fraction. Coupled system of equations is derived for large and fine scales transport

ANTIMICROBIAL ACTIVITY OF LACTOBACILLUS PLANTARUM AGAINST PATHOGENIC AND FOOD SPOILAGE MICROORGANISMS: A REVIEW

One of the most important properties of probiotic bacteria is their antimicrobial activity against many species of microorganisms which could be useful to prevent food spoilage caused by certain sensitive bacteria and fungi as well as to control the speed of propagation of potentially pathogenic bacteria by probiotic application. Lactobacillus plantarum is considered one of the probiotic bacteria with broad-est spectrum of antibacterial activity which makes it useful in veterinary, human medicine and food industry. According to a number of studies Lactobacillus plantarum exerts inhibitory activity against ma¬ny Gram-positive and Gram-negative bacteria – Escherichia coli (including E. coli 0157:H7), Pseudomonas aeruginosa, Helicobacter pylori, Yersinia enterocolitica, Campylobacter jejuni, Lis-teria monocytogenes, Staphylococcus aureus, Klebsiella, Salmonella, Shigella, Bacillus, Clostridium, Enterococcus, Lactobacillus spp., etc. as well as a number of moulds and yeasts – Aspergillus, Fusa-rium, Mucor, Candida spp., etc. The main antibacterial compounds of Lactobacillus plantarum are the bacteriocins and organic acids whereas the antifungal compounds are the organic acids, hydroxy fatty acids and cyclic dipeptides. Because of the high antifungal activity of some L. plantarum strains against food spoilage microorganisms they can be used as effective biopreservatives in food industry. Also, some L. plantarum strains could be applied as supporting therapeutic agents in treatment of infections caused by the corresponding susceptible microorganisms

Stress Dependence of Exciton Relaxation Processes in Cu2O

A comprehensive study of the exciton relaxation processes in Cu2O has led to some surprises. We find that the ortho-para conversion rate becomes slower at high stress, and that the Auger nonradiative recombination rate increases with stress, with apparently no Auger recombination at zero stress. These results have important consequences for the pursuit of Bose-Einstein condensation of excitons in a harmonic potential.Comment: 10 figures, 1 tabl

Ring-shaped spatial pattern of exciton luminescence formed due to the hot carrier transport in a locally photoexcited electron-hole bilayer

A consistent explanation of the formation of a ring-shaped pattern of exciton luminescence in GaAs/AlGaAs double quantum wells is suggested. The pattern consists of two concentric rings around the laser excitation spot. It is shown that the luminescence rings appear due to the in-layer transport of hot charge carriers at high photoexcitation intensity. Interestingly, one of two causes of this transport might involve self-organized criticality (SOC) that would be the first case of the SOC observation in semiconductor physics. We test this cause in a many-body numerical model by performing extensive molecular dynamics simulations. The results show good agreement with experiments. Moreover, the simulations have enabled us to identify the particular kinetic processes underlying the formation of each of these two luminescence rings.Comment: 14 pages, 16 figures. Final versio

New Symmetries in Crystals and Handed Structures

For over a century, the structure of materials has been described by a combination of rotations, rotation-inversions and translational symmetries. By recognizing the reversal of static structural rotations between clockwise and counterclockwise directions as a distinct symmetry operation, here we show that there are many more structural symmetries than are currently recognized in right- or left-handed handed helices, spirals, and in antidistorted structures composed equally of rotations of both handedness. For example, though a helix or spiral cannot possess conventional mirror or inversion symmetries, they can possess them in combination with the rotation reversal symmetry. Similarly, we show that many antidistorted perovskites possess twice the number of symmetry elements as conventionally identified. These new symmetries predict new forms for "roto" properties that relate to static rotations, such as rotoelectricity, piezorotation, and rotomagnetism. They also enable symmetry-based search for new phenomena, such as multiferroicity involving a coupling of spins, electric polarization and static rotations. This work is relevant to structure-property relationships in all material structures with static rotations such as minerals, polymers, proteins, and engineered structures.Comment: 15 Pages, 4 figures, 3 Tables; Fig. 2b has error

Two-phonon coupling to the antiferromagnetic phase transition in multiferroic BiFeO3

A prominent band centered at around 1000-1300 cm-1 and associated with resonant enhancement of two-phonon Raman scattering is reported in multiferroic BiFeO3 thin films and single crystals. A strong anomaly in this band occurs at the antiferromagnetic Neel temperature. This band is composed of three peaks, assigned to 2A4, 2E8, and 2E9 Raman modes. While all three peaks were found to be sensitive to the antiferromagnetic phase transition, the 2E8 mode, in particular, nearly disappears at TN on heating, indicating a strong spin-two phonon coupling in BiFeO3.Comment: 12 pages with figure

Spin-Charge-Lattice Coupling through Resonant Multi-Magnon Excitations in Multiferroic BiFeO3

Spin-charge-lattice coupling mediated by multi-magnon processes is demonstrated in multiferroic BiFeO3. Experimental evidence of two and three magnons excitations as well as multimagnon coupling at electronic energy scales and high temperatures are reported. Temperature dependent Raman experiments show up to five resonant enhancements of the 2-magnon excitation below the Neel temperature. These are shown to be collective interactions between on-site Fe d-d electronic resonance, phonons and multimagnonsComment: 11 pages including figure