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Molecular-beam synchrotron photoionization mass spectrometry and electron-ionization mass spectrometry are used for measurements of species mole fraction profiles for low-pressure premixed dimethyl ether (DME) flames with equivalence ratios ranging from near-stoichiometric conditions (Phi = 0.93) to fuel-rich flames near the limits of flat-flame stability (Phi = 1.86). The results are compared with predictions of a recently modified kinetic model for DME combustion [Zhao et al., Int. J. Chem. Kinet., 2008, 40, 1-18] that has been extensively tested against laminar flame speed measurements, jet-stirred reactor experiments, pyrolysis and oxidation experiments in flow reactors, species measurements for burner-stabilized flames and ignition delay measurements in shock tubes. The present comprehensive measurements of the composition of reaction intermediates over a broad range of equivalence ratios considerably extends the range of the previous experiments used for validation of this model and allows for an accurate determination of contributions of individual reactions to the formation or destruction of any given flame species. The excellent agreement between measurements and predictions found for all major and most intermediate species over the entire range of equivalence ratios provides a uniquely sensitive test of details of the kinetic model. The dependence on equivalence ratio of the characteristic reaction paths in DME flames is examined within the framework of reaction path analyses.

It is known that ischemia/reperfusion induces neurodegeneration in the hippocampus in a sub-region dependent manner. The present study investigated the mechanism of selective resistance/vulnerability to oxygen glucose deprivation (OGD) using mouse organotypic hippocampal cultures. Analysis of propidium iodide uptake showed that OGD induced duration- and sub-region-dependent neuronal injury. As compared to the CA1-3 sub-regions, dentate neuronal survival was more sensitive to inhibition of PI3K/Akt signaling under basal conditions. Dentate neuronal sensitivity to PI3K/Akt signaling activation was inversely related to its vulnerability to OGD-induced injury; Insulin/IGF pretreatment conferred neuroprotection to dentate neurons via activation of PI3K/Akt signaling. In contrast, CA1 and CA3 neurons were less sensitive to disruptions of endogenous PI3K/Akt signaling and protective effects of insulin/IGF-1, but more vulnerable to OGD. OGD-induced injury in CA1 was reduced by inhibition of NMDA receptor or MAPK signaling, and was prevented by blocking NMDA receptor in the presence of insulin. The CA2 sub-region was distinctive in its response to glutamate, OGD, and insulin, compared to other CA sub-regions. CA2 neurons were sensitive to the protective effects of insulin against OGD-induced injury, but more resistant to glutamate. Distinctive distribution of insulin receptor β and basal phospho-Akt was detected in our slice cultures. Our results suggest a role for insulin signaling in sub-regional resistance/vulnerability to cerebral ischemia.

BackgroundSome plants develop a breeding system that produces both chasmogamous (CH) and cleistogamous (CL) flowers. However, the underlying molecular mechanism remains elusive.ResultsIn the present study, we observed that Viola philippica develops CH flowers with short daylight, whereas an extended photoperiod induces the formation of intermediate CL and CL flowers. In response to long daylight, the respective number and size of petals and stamens was lower and smaller than those of normally developed CH flowers, and a minimum of 14-h light induced complete CL flowers that had no petals but developed two stamens of reduced fertility. The floral ABC model indicates that B-class MADS-box genes largely influence the development of the affected two-whorl floral organs; therefore, we focused on characterizing these genes in V. philippica to understand this particular developmental transition. Three such genes were isolated and respectively designated as VpTM6-1, VpTM6-2, and VpPI. These were differentially expressed during floral development (particularly in petals and stamens) and the highest level of expression was observed in CH flowers; significantly low levels were detected in intermediate CL flowers, and the lowest level in CL flowers. The observed variations in the levels of expression after floral induction and organogenesis apparently occurred in response to variations in photoperiod.ConclusionsTherefore, inhibition of the development of petals and stamens might be due to the downregulation of B-class MADS-box gene expression by long daylight, thereby inducing the generation of CL flowers. Our work contributes to the understanding of the adaptive evolutionary formation of dimorphic flowers in plants.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-016-0832-2) contains supplementary material, which is available to authorized users.