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Inviscid and turbulent airflows over a symmetric flat-sided double wedge are studied numerically. Solutions of the Euler and Navier-Stokes equations are obtained with a finite-volume solver on fine meshes. The solutions demonstrate both symmetric and asymmetric flow regimes in significant bands of the free-stream Mach number at zero angle of attack. The realization of a certain regime depends on the time history of boundary conditions. A physical interpretation of transitions between the symmetric and asymmetric flows is suggested.

The two-dimensional turbulent airflow in a 9-degrees-bent channel is studied numerically. Inner surfaces of the top and bottom walls are parallel to each other upstream and downstream of the bend. The free stream is supersonic, whereas the flow is subsonic at the channel exit. Solutions of the Reynolds-averaged Navier-Stokes equations are obtained with a finite-volume solver using the Spalart-Allmaras and Shear Stress Transport k −! turbulence models. The solutions reveal a flow hysteresis and non-uniqueness in considerable bands of the free-stream Mach number, angle of attack, and exit pressure. At the endpoints of the bands, there are abrupt changes of the shock wave system. The non-uniqueness admits different losses of the total pressure, which may cause different trusts of an air breathing engine.

The transonic turbulent two-dimensional airflow over a symmetric flat-sided double wedge is studied numerically. Solutions of the Reynolds-averaged Navier-Stokes equations are obtained with ANSYS-18.2 CFX finite-volume solver of second order accuracy on a fine mesh. The solutions demonstrate an extreme sensitivity of the flow field and lift coefficient to variation of the angle of attack α or free-stream Mach number M∞. Non-unique flow regimes and hysteresis in certain bands of α and M∞ are identified. Interaction of shock waves and local supersonic regions is discussed. The study confirms a concept of shock wave instability due to a coalescence/rupture of supersonic regions. In addition to the instability of shock wave locations, the numerical simulation shows a buffet onset, i.e., self-exciting oscillations due to instability of a boundary layer separation at the rear of wedge. Curious flow regimes with positive lift at negative angles α and, vice versa, with negative lift at positive angles α, are pointed out. A piecewise continuous dependence of the lift coefficient on two free-stream parameters, α and M∞, is discussed.

Reactive oxygen species (ROS), superoxide anion and hydrogen peroxide, are generated as byproducts of oxidative phosphorylation in the mitochondria or via cell signaling-induced NADPH oxidases in the cytosol. In the recent two decades, a plethora of studies established that elevated ROS levels generated by oxidative eustress are crucial physiological mediators of many cellular and developmental processes. In this review, we discuss the mechanisms of ROS generation and regulation, current understanding of ROS functions in the maintenance of adult and embryonic stem cells, as well as in the process of cell reprogramming to a pluripotent state. Recently discovered cell-non-autonomous ROS functions mediated by growth factors are crucial for controlling cell differentiation and cellular immune response in Drosophila . Importantly, many physiological functions of ROS discovered in Drosophila may allow for deciphering and understanding analogous processes in human, which could potentially lead to the development of novel therapeutic approaches in ROS-associated diseases treatment.

In photodynamic therapy, light is absorbed by a therapy agent (photosensitizer) to generate reactive oxygen, which then locally kills diseased cells. Here, we report a new form of photodynamic therapy in which nonlinear optical interactions of near-infrared laser radiation with a biological medium in situ produce light that falls within the absorption band of the photosensitizer. The use of near-infrared radiation, followed by upconversion to visible or ultraviolet light, provides deep tissue penetration, thus overcoming a major hurdle in treatment. By modelling and experiment, we demonstrate activation of a known photosensitizer, chlorin e6, by in situ nonlinear optical upconversion of near-infrared laser radiation using second-harmonic generation in collagen and four-wave mixing, including coherent anti-Stokes Raman scattering, produced by cellular biomolecules. The introduction of coherent anti-Stokes Raman scattering/four-wave mixing to photodynamic therapy in vitro increases the efficiency by a factor of two compared to two-photon photodynamic therapy alone, while second-harmonic generation provides a fivefold increase. An investigation of the use of nonlinear upconversion effects like second-harmonic generation and four-wave mixing within biological tissue indicates that it should be possible to perform photodynamic therapy with near-infrared laser light at greater depths than previously.

Single-crystal, microcrystalline and nanocrystalline nickel oxides (NiO) have been studied by Raman spectroscopy. A new band at ~200 cm and TO-LO splitting of the band at 350–650 cm have been found in the spectra of single-crystals NiO(100), NiO(110) and NiO(111). The Raman spectra of microcrystalline (1500 nm) and nanocrystalline (13–100 nm) NiO resemble those of the single crystals. They all contain the two-magnon band at 1500 cm , indicating that the oxides remain at room temperature in the antiferromagnetic phase. Besides, a new sharp Raman band has been observed at 500 cm in nanocrystalline NiO. Its temperature dependence suggests the magnetic origin of the band, possibly associated with the one-phonon–one-magnon excitation at the Brillouin zone centre.

Background Plant mitochondrial genomes (mitogenomes) can be structurally complex while their size can vary from ~ 222 Kbp in Brassica napus to 11.3 Mbp in Silene conica . To date, in comparison with the number of plant species, only a few plant mitogenomes have been sequenced and released, particularly for conifers (the Pinaceae family). Conifers cover an ancient group of land plants that includes about 600 species, and which are of great ecological and economical value. Among them, Siberian larch ( Larix sibirica Ledeb.) represents one of the keystone species in Siberian boreal forests. Yet, despite its importance for evolutionary and population studies, the mitogenome of Siberian larch has not yet been assembled and studied. Results Two sources of DNA sequences were used to search for mitochondrial DNA (mtDNA) sequences: mtDNA enriched samples and nucleotide reads generated in the de novo whole genome sequencing project, respectively. The assembly of the Siberian larch mitogenome contained nine contigs, with the shortest and the largest contigs being 24,767 bp and 4,008,762 bp, respectively. The total size of the genome was estimated at 11.7 Mbp. In total, 40 protein-coding, 34 tRNA, and 3 rRNA genes and numerous repetitive elements (REs) were annotated in this mitogenome. In total, 864 C-to-U RNA editing sites were found for 38 out of 40 protein-coding genes. The immense size of this genome, currently the largest reported, can be partly explained by variable numbers of mobile genetic elements, and introns, but unlikely by plasmid-related sequences. We found few plasmid-like insertions representing only 0.11% of the entire Siberian larch mitogenome. Conclusions Our study showed that the size of the Siberian larch mitogenome is much larger than in other so far studied Gymnosperms, and in the same range as for the annual flowering plant Silene conica (11.3 Mbp). Similar to other species, the Siberian larch mitogenome contains relatively few genes, and despite its huge size, the repeated and low complexity regions cover only 14.46% of the mitogenome sequence.

Turbulent airflow in a supersonic intake model of rectangular cross-section is studied numerically. Instability of shock waves formed in the intake and ahead of the entrance is examined. Solutions of the Reynolds-averaged Navier–Stokes equations are obtained with a finite-volume solver of second-order accuracy. The expulsion and the swallowing of the shocks with a variation of free-stream parameters are studied at both subsonic and supersonic conditions prescribed at the outlet. Hysteresis in the dependence of 2D flow on the free-stream velocity and angle-of-attack is documented. An influence of 3D effects on the flow is examined.

This paper presents a numerical study of the 2D and 3D turbulent airflows in divergent 9°-bent channels. The incoming flow is supersonic, whereas the exit flow may be either supersonic or subsonic. Solutions of the Reynolds-averaged Navier-Stokes equations are obtained with a finite-volume solver ANSYS CFX using the Spalart-Allmaras and Shear Stress Transport k-ω turbulence models. The solutions reveal a significant hysteresis of the flow field under variations of the free-stream Mach number or exit pressure. At the ends of hysteresis bands, the flow pattern changes crucially due to instability of a shock wave formed near the bend of channel. The instability is caused by the shock foot interaction with an expansion flow developed over the convex wall of channel. Boundary conditions, in which the flow admits a double hysteresis, are figured out. The occurrence of non-unique flow regimes must be taken into account in the advanced intake design, as different losses of the total pressure may cause different trusts of an air breathing engine.