NaCl-dependent formation of the highly crystalline phase in sufficiently hydrated dimyristoylphosphatidylglycerol bilayers

We investigated the low-temperature phase behavior of dimyristoylphosphatidylglycerol (DMPG) bilayers in the presence of high concentration of NaCl (≥100 mM). Differential scanning calorimetry showed that the highly crystalline (HC) phase grew after an initial delay period when DMPG bilayers were sufficiently hydrated and incubated at 1˚C in the presence of more than 100 mM NaCl. The HC phase formation reached a plateau, the level of which depended on NaCl concentration; all the lipids were unable to be in the HC phase at the plateau stage without a quite high concentration of NaCl. Since electron microscopic observations suggested that the HC phase formed coexists with the precursor phases in a closed vesicle, elastic constrain and/or shortage of free sodium ions in the inside of the closed vesicle may prevent the complete transition into the HC phase

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Re-evaluation of the phylogeny based on mitochondrial cytochrome b gene in the house shrew, Suncus murinus-S. montanus species complex, with special reference to Yemen and Myanmar populations

The house shrew (Suncus murinus-S. montanus species complex) is considered to have been unintentionally introduced by humans from their original range to other regions around the　Indian Ocean and neighboring seas, but this has yet not fully been investigated. A phylogenetic tree and haplotype network were reconstructed　based on the mitochondrial cytochrome b gene nucleotide sequences (1140 bp) of 179 individuals of house shrews from 46 localities in southern East Asia, Southeast Asia, West Asia, and islands in the western Indian Ocean. There was small genetic variation among shrews in Japan (Okinawa), southern China, Vietnam, and insular Southeast Asia. However, the shrew populations in Myanmar and Sri Lanka showed of a variety of different haplotypes. In the region of the western Indian Ocean, three interesting findings were obtained. First, the shrews on Zanzibar Island (Tanzania) shared same haplotype as those in southwestern Iran, and the haplotype was close to a group in Pakistan, despite these three regions being distantly located. Second, inferring from the haplotype network, it was suggests that the shrews in Yemen might have derived from Madagascar/Comoros populations. Third, the shrews on Réunion Island were genetically different from other populations around the western Indian Ocean but closer to Malaysia and Myanmar populations. Thus, the present study demonstrates that there have been dynamic immigration/emigration processes in the house shrews, especially for those around the western Indian Ocean. In addition, the house shrews in Myanmar may include several different species

Isothermal switching of perpendicular exchange bias by pulsed high magnetic field

Isothermal switching of a perpendicular exchange bias by a strong pulsed magnetic field has been investigated using a Pt/Co/α-Cr₂O₃ thin film system. The switching of the perpendicular exchange bias is accompanied by the spin reversal of interfacial uncompensated antiferromagnetic Cr spins. We have also demonstrated that the switching of the exchange bias is reversible by changing the pulsed magnetic field direction. The mechanism of the demonstrated switching is discussed from the viewpoint of the spin flop transition of the α-Cr₂O₃ layer.Yu Shiratsuchi, Kohei Wakatsu, Tetsuya Nakamura, Hiroto Oikawa, Satoru Maenou, Yasuo Narumi, Kou Tazoe, Chiharu Mitsumata, Toyohiko Kinoshita, Hiroyuki Nojiri, and Ryoichi Nakatani, Appl. Phys. Lett. 100, 262413 (2012); https://doi.org/10.1063/1.4731643

New aspect of photophysics of 7,7,8,8-tetracyanoquinodimethane and its solvated complexes: intra- vs. inter-molecular charge-transfer

We performed laser-induced fluorescence (LIF) spectroscopy of 7,7,8,8-tetracyanoquinodimethane (TCNQ) and its solvated complexes with acetonitrile (ACN) and benzene (Bz), under the jet-cooled gas-phase condition. We also carried out fluorescence and its time profile measurements in TCNQ/Bz/hexane solution to compare with the gas-phase results. The LIF excitation spectrum of the S-1 (pi pi*)-S-0 electronic transition of TCNQ monomer exhibited unusual vibronic structure with the maximum intensity at similar to 3000 cm(-1) above the band origin. In addition, the fluorescence lifetime is more than 100 times longer than that in hexane solution with most of the bands showing double exponential decay. The unusual feature of the vibronic bands is intrinsic and not due to the presence of other species, as confirmed by UV-UV hole-burning (HB) spectroscopy. These unusual features of S-1 are thought to be due to the coupling with the S-2 state, where S-2 was revealed to have intramolecular charge-transfer (ICT) character. The S-1-S-0 transition of the TCNQ-ACN complex exhibited sharp vibronic bands which are red-shifted by 120 cm(-1) from those of the monomer, indicating van der Waals (vdW) interaction between them; however, the fluorescence lifetime was drastically shortened. In contrast, the TCNQ-Bz complex gave a broad electronic spectrum. The study of the fluorescence and its time profile in TCNQ/Bz/hexane solution clearly shows the formation of the CT complex between TCNQ and Bz. Based on the experimental results and density functional theory (DFT) calculations, we propose that in the TCNQ monomer and TCNQ-ACN complex the S-1 (pi pi*) state is coupled to the intramolecular CT state, while the S-1 state of TCNQ in the TCNQ-Bz complex is more strongly coupled to the intermolecular CT state

A cold seep triggered by a hot ridge subduction

The Chile Triple Junction, where the hot active spreading centre of the Chile Rise system subducts beneath the South American plate, offers a unique opportunity to understand the influence of the anomalous thermal regime on an otherwise cold continental margin. Integrated analysis of various geophysical and geological datasets, such as bathymetry, heat flow measured directly by thermal probes and calculated from gas hydrate distribution limits, thermal conductivities, and piston cores, have improved the knowledge about the hydrogeological system. In addition, rock dredging has evidenced the volcanism associated with ridge subduction. Here, we argue that the localized high heat flow over the toe of the accretionary prism results from fluid advection promoted by pressure-driven discharge (i.e., dewatering/discharge caused by horizontal compression of accreted sediments) as reported previously. However, by computing the new heat flow values with legacy data in the study area, we raise the assumption that these anomalous heat flow values are also promoted by the eastern flank of the currently subducting Chile Rise. Part of the rift axis is located just below the toe of the wedge, where active deformation and vigorous fluid advection are most intense, enhanced by the proximity of the young volcanic chain. Our results provide valuable information to current and future studies related to hydrothermal circulation, seismicity, volcanism, gas hydrate stability, and fluid venting in this natural laboratory