Spin-Wave Spectrum in `Single-Domain' Magnetic Ground State of Triangular Lattice Antiferromagnet CuFeO2

By means of neutron scattering measurements, we have investigated spin-wave excitation in a collinear four-sublattice (4SL) magnetic ground state of a triangular lattice antiferromagnet CuFeO2, which has been of recent interest as a strongly frustrated magnet, a spin-lattice coupled system and a multiferroic. To avoid mixing of spin-wave spectrum from magnetic domains having three different orientations reflecting trigonal symmetry of the crystal structure, we have applied uniaxial pressure on [1-10] direction of a single crystal CuFeO2. By elastic neutron scattering measurements, we have found that only 10 MPa of the uniaxial pressure results in almost 'single domain' state in the 4SL phase. We have thus performed inelastic neutron scattering measurements using the single domain sample, and have identified two distinct spin- wave branches. The dispersion relation of the upper spin-wave branch cannot be explained by the previous theoretical model [R. S. Fishman: J. Appl. Phys. 103 (2008) 07B109]. This implies the importance of the lattice degree of freedom in the spin-wave excitation in this system, because the previous calculation neglected the effect of the spin-driven lattice distortion in the 4SL phase. We have also discussed relationship between the present results and the recently discovered "electromagnon" excitation.Comment: 5 pages, 3 figures, accepted for publication in J. Phys. Soc. Jp

Gender Pay Gap: A Macro Perspective

This paper examines the factors influencing the gender wage gap by using an unbalanced cross-country aggregated panel data set for a sample covering 53 economies for the period 1995–2010. Using robust estimators proposed by Lewbel (2012) to correct for heterogeneity and endogeneity, results suggest that a higher female share in the industry sector tends to widen the gender wage gap regardless of a country’s development stage. While having more children widens the gender wage gap, as expected, the effect is only statistically significant for developing countries. In developed countries, more labor force participation by women seems to narrow the gender wage gap, probably due to the number of female labor market entrants taking up higher-paying service sector jobs. For developing countries, closing the gender gaps in labor force participation and education is not sufficient to achieve gender wage parity. Higher-paying jobs should be created by developing the service sector in these economies

Myopericytoma of low grade malignancy in the oral cavity

Myopericytoma (MPC) of the oral cavity is extremely rare. Herein reported is a case of MPC of low grade malignancy in the oral cavity. A 61-year-old man noticed a tumor of the cheek mucosa, and admitted to our hospital. Oral examination revealed a reddish elevated tumor of the cheek mucosa. Tumorectomy with wide margins was performed. The clinical diagnosis was pyogenic granuloma. Grossly, the tumor was reddish, and measured 1×1×1 cm. Microscopically, oval to spindle tumor cells with hyperchromatic vesicular nuclei and many vasculatures were seen. The tumor cells were contiguous and mixed with endothelial cells in many blood vessels, thus resembling pericytes. Mitotic figures were scattered. The surgical margins were negative for tumor cells. Immunohistochemically, the tumor cells were positive for vimentin, α-smooth muscle actin and p53. The Ki67 labeling was 40%. The tumor cells were negative for cytokeratins (AE1/3 and CAM5.2), CD31, CD34, S100 protein, HMB45, CD10, vimentin, desmin, and factor VIII-related antigen. The endothelium of the vessels were positive for vimentin, CD31, CD34 and factor VIII-related antigen, but negative for α-smooth muscle actin, p53, cytokeratins (AE1/3 and CAM5.2), S100 protein, HMB45, CD10, vimentin, and desmin. The Ki67 labeling was 5%. Because the pericytoid tumor cells showed α-smooth muscle actin and negative for endothelial markers, MPC was diagnosed. In addition, because there was some atypia and mitotic figures were scatters and also because the tumor cells were positive for p53 and Ki67 labeling was high, a pathological diagnosis of MPC with low grade malignancy was made. No recurrence was observed, and the patient is now free from tumor 6 months after the operation

Small aggregates can cause nitrite accumulation in one-stage partial nitritation and anammox

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A search for cyclotron resonance features with INTEGRAL

We present an INTEGRAL observation of the Cen-Crux region in order to search the electron cyclotron resonance scattering features from the X-ray binary pulsars. During the AO1 200ks observation, we clearly detected 4 bright X-ray binaries, 1 Seyfert Galaxy, and 4 new sources in the field of view. Especially from GX301-2, the cyclotron resonance feature is detected at about 37 keV, and width of 3--4 keV. In addition, the depth of the resonance feature strongly depends on the X-ray luminosity. This is the first detection of luminosity dependence of the resonance depth. The cyclotron resonance feature is marginally detected from 1E1145.1-6141. Cen X-3 was very dim during the observation and poor statistics disable us to detect the resonance features.These are first INTEGRAL results of searching for the cyclotron resonance feature.Comment: 4pages, 8figures, To be published in the Proceedings of the 5th INTEGRAL Workshop: "The INTEGRAL Universe", February 16-20, 2004, Munic

Discovery of a new pulsating X-ray source with a 1549.1-s period, AX J183220-0840

A new pulsating X-ray source, AX J183220-0840, with a 1549.1-s period was discovered at R.A.= 18h32m20s and Dec.=-8d40'30'' (J2000, uncertainty=0.6degree) during an ASCA observation on the Galactic plane. The source was observed two times, in 1997 and in 1999. A phase-averaged X-ray flux of 1.1E-11 ergs cm-2 s-1 and pulsation period of 1549.1+/-0.4 s were consistently obtained from these two observations. The X-ray spectrum was represented by a flat absorbed power-law with a photon-index of =~0.8 and an absorption column density of =~1.3E22 cm-2. Also, a signature of iron K-shell line emission with a centroid of 6.7 keV and an equivalent width of approximately 450 eV was detected. From the pulsation period and the iron-line feature, AX J183220-0840 is likely to be a magnetic white dwarf binary with a complexly absorbed thermal spectrum with a temperature of about 10 keV.Comment: 13 pages, 4 figures, accepted for publication in ApJ Letter

Distribution of dust clouds around the central engine of NGC 1068

We studied the distribution of dust clouds around the central engine of NGC 1068 based on shifted-and-added 8.8 - 12.3 micron (MIR) multi-filter images and 3.0 - 3.9 micron (L-band) spectra obtained with the Subaru Telescope. In a region of 100 pc (1.4") around the central peak, we successfully constructed maps of color temperatures and emissivities of the MIR and L-band continua as well as the 9.7 micron and 3.4 micron dust features with spatial resolutions of 26 pc (0.37") in the MIR and 22 pc (0.3") in the L-band. Our main results are: 1) color temperature of the MIR continuum scatters around the thermal equilibrium temperature with the central engine as the heat source while that of the L-band continuum is higher and independent upon distance from the central engine; 2) the peak of the 9.7 micron silicate absorption feature is shifted to a longer wavelength at some locations; 3) the ratio of the optical depths of the dust features is different from the Galactic values and show complicated spatial distribution; and 4) there is a pie shaped warm dust cloud as an enhancement in the emissivity of the MIR continuum extending about 50 pc to the north from the central engine. We speculate that material falls into the central engine through this cloud.Comment: 26 pages, 9 figures. Accepted for publication on Ap

Infrared Imaging of the Gravitational Lens PG 1115+080 with the Subaru Telescope

We present high spatial resolution images of the gravitational-lens system PG 1115+080 taken with the near-infrared camera (CISCO) on the Subaru telescope. The FWHM of the combined image is $0.''32$ in the $K'$-band, yielding spatial resolution of $0.''14$ after a deconvolution procedure. This is a first detection of an extended emission adjacent to the A1/A2 components, indicating the presence of a fairly bright emission region with a characteristic angular radius of $\sim$ 5 mas (40 pc). The near-infrared image of the Einstein ring was extracted in both the $J$ and $K'$ bands. The $J-K'$ color is found to be significantly redder than that of a synthetic model galaxy with an age of 3 Gyr, the age of the universe at the quasar redshift.Comment: 11 pages, 6 figures. Accepted for publication in PASJ(2000