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Transition and turbulence production in a hypersonic boundary layer is investigated in the Mach 6 wind tunnel at Peking University, using Rayleigh-scattering visualization, fast-response pressure measurements, and particle image velocimetry. Detailed analysis of the experimental observations is provided. It is found that, although the second mode is primarily an acoustic wave, it causes the formation of high-frequency vortical waves. Moreover, the second mode interacts strongly with low-frequency waves, which leads to immediate transition to turbulence.freestream velocity, m∕s u = velocity vector, m∕s u = x component of the velocity, m∕s v = y component of the velocity, m∕s w = z component of the velocity, m∕s x = streamwise coordinate along the cone's surface, mm y = coordinate normal to the cone's surface, mm z = transverse coordinate normal to the x-y plane, mm= viscous normal stress, Pa ρ = density, kg∕m 3 τ f = flow time scale, s τ p = particle relaxation time, s Φ = viscous dissipation function per unit volume, kg∕m · s 3 ω = vorticity, 1∕s

Transition and turbulence production in a hypersonic boundary layer is investigated in a Mach 6 wind tunnel using Rayleigh-scattering visualization, fast-response pressure measurements, and particle image velocimetry. It is found that the second-mode instability is a key modulator of the transition process. Although the second-mode is primarily an acoustic wave, it causes the formation of high-frequency vortical waves, which triggers a fast transition to turbulence.

Highly variable regions of chloroplast genome were found to be useful in the detection of plant genetic diversity at micro-evolution level. Our methodology will improve understanding and conservation of plant diversity. Tree peonies are famous flowers with about 2,000 cultivars in the world, belonging to Paeonia sect. Moutan of the Paeoniaceae. They are traditionally classified based on flower forms and colors. Due to the limited number of DNA and morphological markers, and the existence of synonyms and homonyms, evaluation on genetic diversity of so many cultivars remains a challenge. In most cases, it is difficult and even impossible to discriminate tree peony cultivars when they are not in flower. In this study, single nucleotide polymorphism detected from the hyper-variable regions of chloroplast genome was employed to separate tree peony cultivars into different maternal lineages which can be expressed briefly by a nucleotide molecular formula. Our approach enabled a much higher resolution of cultivar identification and classification that has not been obtained before. The newly developed hyper-variable chloroplast markers, as an independent source of taxonomic characteristics, provided novel evidences and higher resolution ability that are helpful in building an effective classification system for evaluation, conservation, and utilization of the tree peony germplasm resources at cultivar level.