459 research outputs found
Decades-long phylogeographic issues: complex historical processes and ecological factors on genetic structure of alpine plants in the Japanese Archipelago
Mountain regions are important places for biodiversity, where organisms could persist throughout prolonged periods and accumulate genetic divergence as well as promote speciation. Roles of mountains for biodiversity have been exclusively discussed in regions that have specifically diverse species or covered with ice-sheets during the Pleistocene glacial periods, whereas the importance of mountainous regions in East Asia has been less disputed. High mountains in the Japanese Archipelago, located at the eastern edge of the Eurasia continent, have one of southernmost populations of alpine and arctic-alpine plants that are also distributed in the northern Pacific and/or the circumarctic regions. Phylogeographic studies on the Japanese alpine plants have excluded their possible ephemeral occurrence during the current warm period, and rather, suggest persistence of alpine plants throughout several cycles of climate changes in the Pleistocene on high mountains in central Honshu, the main island of the Japanese Archipelago. In this review, I look through decade long phylogeographic studies and show complicated patterns of range dynamics of Japanese alpine plants. In addition, I note recent findings of genetic relationships of Japanese populations of alpine and/or arctic-alpine plants with those in northern regions and their possible ecological divergence in the Japanese Archipelago. Taken together, I provide several issues for understanding historical processes that established distribution of alpine plants following climate changes as well as their diversification and propose importance of Japanese populations of alpine plants on biodiversity in alpine communities across broader range, especially in the northern Pacific region
Design of Hemispherical Radio Frequency (RF) Capacitive-type Electrode Free of Edge Effects for Treatment of Intracavitary Tumors
A new hemispherical electrode to heat oral cavity cancer is proposed. The electrode does not produce a hot spot around its edge, a feature that usually arises when using radio frequency (RF) capacitive-type heating. The hemispherical electrode was designed by computer simulation using a 3-D finite element method. To assess its practicality and effectiveness, we built a prototype hemispherical electrode
and evaluated its heating characteristics by phantom experiments. The heating effects on the phantom were measured by thermography. The concave phantom surface in contact with the hemispherical
electrode showed a uniform increase in temperature, with no obvious edge effect. The proposed
electrode allows non-invasive RF capacitive-type heating for intracavity tumors that was not previously considered possible, and should contribute to the multidisciplinary treatment of intracavity tumors
Antiviral and Virucidal Activities of Nα-Cocoyl-L-Arginine Ethyl Ester
Various amino acid-derived compounds, for example, Nα-Cocoyl-L-arginine ethyl ester (CAE), alkyloxyhydroxylpropylarginine, arginine cocoate, and cocoyl glycine potassium salt (Amilite), were examined for their virucidal activities against herpes simplex virus type 1 and 2 (HSV-1 and HSV-2), influenza A virus (IAV), and poliovirus type 1 (PV-1) in comparison to benzalkonium chloride (BKC) and sodium dodecylsulfate (SDS) as a cationic and anionic control detergent and also to other commercially available disinfectants. While these amino acid-derived compounds were all effective against HSV-1 and HSV-2, CAE and Amilite were the most effective. These two compounds were, however, not as effective against IAV, another enveloped virus, as against HSV. Cytotoxicity of CAE was weak; at 0.012%, only 5% of the cells were killed under the conditions, in which 100% cells were killed by either SDS or BKC. In addition to these direct virucidal effects, CAE inhibited the virus growth in the HSV-1- or PV-1-infected cells even at 0.01%. These results suggest a potential application of CAE as a therapeutic or preventive medicine against HSV superficial infection at body surface
Anisotropic magnetotransport properties coupled with spiral spin modulation in a triangular-lattice magnet EuZnGe
We investigate the thermodynamic, magnetic, and electrical transport
properties of a triangular-lattice antiferromagnet EuZnGe using single crystals
grown from Eu-Zn flux in sealed tantalum tubes. Magnetic properties are found
to be isotropic in the paramagnetic state while we observe an enhancement of
in-plane magnetic susceptibility at the temperature near T* =11.3 K, suggesting
an easy-plane anisotropy at low temperatures. Magnetic transition temperature
is lower than T* as specific heat shows a peak at TN =7.6 K. We reveal the
magnetic modulation along the c axis by resonant x-ray scattering at Eu L2
edge, which suggests competing magnetic interaction among Eu triangular-lattice
layers. We observe a double-peak structure in the intensity profile along (0,
0, L) below TN, which is mainly composed of a dominant helical modulation with
q ~ (0, 0, 0.4) coexisting with a secondary contribution from q ~ (0, 0, 0.5).
We reproduce the intensity profile with a random mixture of five- and
four-sublattice helices with spin rotation skipping due to hexagonal in-plane
anisotropy. The metallic conductivity is highly anisotropic with the ratio
rho_zz/rho_xx exceeding 10 over the entire temperature range and additionally
exhibits a sharp enhancement of rho_zz at TN giving rise to rho_zz/rho_xx ~ 50,
suggesting a coupling between out-of-plane electron conduction and the spiral
magnetic modulations. In-plane magnetic field induces a spin-flop like
transition, where the q = 0.4 peak disappears and an incommensurate peak of
approximately qICM ~ 0.47 emerges, while the q = 0.5 modulation retains a
finite intensity. This transition correlates with non-monotonic
magnetoresistance and Hall resistivity, suggesting a significant interplay
between electrons and spin structures through Ruderman-Kittel-Kasuya-Yosida
(RKKY) interaction.Comment: 9 pages, 6 figure
Physical Properties of Dense Cores in the Rho Ophiuchi Main Cloud and A Significant Role of External Pressures in Clustered Star Formation
Using the archive data of the H13CO+ (J=1-0) line emission taken with the
Nobeyama 45 m radio telescope with a spatial resolution of about 0.01pc, we
have identified 68 dense cores in the central dense region of the rho Ophiuchi
main cloud. The H13CO+ data also indicates that the fractional abundance of
H13CO+ relative to H2 is roughly inversely proportional to the square root of
the H2 column density with a mean of 1.72 x 10^{-11}. The mean radius, FWHM
line width, and LTE mass of the identified cores are estimated to be 0.045 +-
0.011 pc, 0.49 +- 0.14 km/s, and 3.4 +- 3.6 Msolar, respectively. The majority
of the identified cores have subsonic internal motions. The virial ratio, the
ratio of the virial mass to the LTE mass, tends to decrease with increasing the
LTE mass and about 60 percent of the cores have virial ratios smaller than 2,
indicating that these cores are not transient structures but self-gravitating.
The detailed virial analysis suggests that the surface pressure often dominates
over the self-gravity and thus plays a crucial role in regulating core
formation and evolution. By comparing the rho Oph cores with those in the Orion
A molecular cloud observed with the same telescope, we found that the
statistical properties of the core physical quantities are similar between the
two clouds if the effect of the different spatial resolutions is corrected. The
line widths of the rho Oph cores appear to be nearly independent of the core
radii over the range of 0.01 - 0.1 pc and deviate upwards from the Heyer &
Brunt relation. This may be evidence that turbulent motions are driven by
protostellar outflows in the cluster environment.Comment: 45 pages, 14 figures, accepted or publication in ApJ, mpeg movies of
figure 3 are available from
http://quasar1.ed.niigata-u.ac.jp/~fnakamur/papers/oph1
Magnetostriction studies up to megagauss fields using fiber Bragg grating technique
We here report magnetostriction measurements under pulsed megagauss fields
using a high-speed 100 MHz strain monitoring system devised using fiber Bragg
grating (FBG) technique with optical filter method. The optical filter method
is a detection scheme of the strain of FBG, where the changing Bragg wavelength
of the FBG reflection is converted to the intensity of reflected light to
enable the 100 MHz measurement. In order to show the usefulness and reliability
of the method, we report the measurements for solid oxygen, spin-controlled
crystal, and volborthite, a deformed Kagom\'{e} quantum spin lattice, using
static magnetic fields up to 7 T and non-destructive millisecond pulse magnets
up to 50 T. Then, we show the application of the method for the
magnetostriction measurements of CaVO, a two-dimensional
antiferromagnet with spin-halves, and LaCoO, an anomalous spin-crossover
oxide, in the megagauss fields.Comment: 9pages, 6 figures, Conference proceedings for MegaGauss16 at Kashiwa,
Japan in Sept. 201
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