691 research outputs found
Phase structure of topological insulators by lattice strong-coupling expansion
The effect of the strong electron correlation on the topological phase
structure of 2-dimensional (2D) and 3D topological insulators is investigated,
in terms of lattice gauge theory. The effective model for noninteracting system
is constructed similarly to the lattice fermions with the Wilson term,
corresponding to the spin-orbit coupling. Introducing the electron-electron
interaction as the coupling to the gauge field, we analyze the behavior of
emergent orders by the strong coupling expansion methods. We show that there
appears a new phase with the in-plane antiferromagnetic order in the 2D
topological insulator, which is similar to the so-called "Aoki phase" in
lattice QCD with Wilson fermions. In the 3D case, on the other hand, there does
not appear such a new phase, and the electron correlation results in the shift
of the phase boundary between the topological phase and the normal phase.Comment: 7 pages, 2 figures; Presented at the 31st International Symposium on
Lattice Field Theory (Lattice 2013), 29 July - 3 August 2013, Mainz, German
In Orbit Performance of the MAXI/SSC onboard the ISS
We report here the in orbit performance of the CCD camera (MAXI/SSC) onboard
the International Space Station (ISS). It was commissioned in August, 2009.
This is the first all-sky survey mission employing X-ray CCDs. It consists of
32 CCDs each of which is 1 inch square. It is a slit camera with a field of
view of 1deg.5x 90deg and scans the sky as the rotation of the ISS. The CCD on
the SSC is cooled down to the working temperature around -60degC by the
combination of the peltier cooler, a loop heat pipe and a radiator. The
standard observation mode of the CCD is in a parallel sum mode (64-binning).
The CCD functions properly although it suffers an edge glow when the Sun is
near the field of view (FOV) which reduces the observation efficiency of the
SSC down to about 30%. The performance of the CCD is continuously monitored
both by the Mn-K X-rays and by the Cu-K X-rays. There are many sources
detected, not only point sources but extended sources. Due to the lack of the
effective observation time, we need more observation time to obtain an extended
emission analysis extraction process.Comment: 15 pages 11 figure
FeII/MgII Emission Line Ratios of QSOs. II. z>6 Objects
Near-infrared spectra of four QSOs located at are obtained with the
OH-airglow suppressor mounted on the Subaru telescope. The FeII/MgII
emission-line ratios of these QSOs are examined by the same fitting algorithm
as in our previous study of QSOs. The fitting results show that two out
of the four QSOs have significant FeII emission in their rest-UV spectra,
while the other two have almost no FeII features. We also applied our fitting
algorithm to more than 10,000 SDSS QSOs and found two trends in the
distribution of FeII/MgII against redshift: (1) the upper envelope of the
FeII/MgII distribution at shows a probable declination toward high
redshift, and (2) the median distribution settles into lower ratios at with small scatter compared to the other redshift. We discuss an Fe/Mg
abundance evolution of QSOs with a substantial contribution from the diverse
nature of the broad-line regions in high-redshift QSOs.Comment: 12 pages, 2 figures. Accepted for publication in ApJ (10 October
2004, v614
Multi-Stage Generalized Deferred Acceptance Mechanism: Strategyproof Mechanism for Handling General Hereditary Constraints
The theory of two-sided matching has been extensively developed and applied
to many real-life application domains. As the theory has been applied to
increasingly diverse types of environments, researchers and practitioners have
encountered various forms of distributional constraints. Arguably, the most
general class of distributional constraints would be hereditary constraints; if
a matching is feasible, then any matching that assigns weakly fewer students at
each college is also feasible. However, under general hereditary constraints,
it is shown that no strategyproof mechanism exists that simultaneously
satisfies fairness and weak nonwastefulness, which is an efficiency (students'
welfare) requirement weaker than nonwastefulness. We propose a new
strategyproof mechanism that works for hereditary constraints called the
Multi-Stage Generalized Deferred Acceptance mechanism (MS-GDA). It uses the
Generalized Deferred Acceptance mechanism (GDA) as a subroutine, which works
when distributional constraints belong to a well-behaved class called
hereditary M-convex set. We show that GDA satisfies several
desirable properties, most of which are also preserved in MS-GDA. We
experimentally show that MS-GDA strikes a good balance between fairness and
efficiency (students' welfare) compared to existing strategyproof mechanisms
when distributional constraints are close to an M-convex set.Comment: 23 page
Observation of a Dirac nodal line in AlB2
We have performed angle-resolved photoemission spectroscopy of AlB2 which is
isostructural to high-temperature superconductor MgB2. Using soft-x-ray
photons, we accurately determined the three-dimensional bulk band structure and
found a highly anisotropic Dirac-cone band at the K point in the bulk hexagonal
Brillouin zone. This band disperses downward on approaching the H point while
keeping its degeneracy at the Dirac point, producing a characteristic Dirac
nodal line along the KH line. We also found that the band structure of AlB2 is
regarded as a heavily electron-doped version of MgB2 and is therefore well
suited for fully visualizing the predicted Dirac nodal line. The present
results suggest that (Al,Mg)B2 system is a promising platform for studying the
interplay among Dirac nodal line, carrier doping, and possible topological
superconducting properties.Comment: 6 pages, 3 figure
Effects of tongue cleaning on bacterial flora in tongue coating and dental plaque: a crossover study
BACKGROUND: The effects of tongue cleaning on reconstruction of bacterial flora in dental plaque and tongue coating itself are obscure. We assessed changes in the amounts of total bacteria as well as Fusobacterium nucleatum in tongue coating and dental plaque specimens obtained with and without tongue cleaning. METHODS: We conducted a randomized examiner-blind crossover study using 30 volunteers (average 23.7 ± 3.2 years old) without periodontitis. After dividing randomly into 2 groups, 1 group was instructed to clean the tongue, while the other did not. On days 1 (baseline), 3, and 10, tongue coating and dental plaque samples were collected after recording tongue coating score (Winkel tongue coating index: WTCI). After a washout period of 3 weeks, the same examinations were performed with the subjects allocated to the alternate group. Genomic DNA was purified from the samples and applied to SYBR® Green-based real-time PCR to quantify the amounts of total bacteria and F. nucleatum. RESULTS: After 3 days, the WTCI score recovered to baseline, though the amount of total bacteria in tongue coating was significantly lower as compared to the baseline. In plaque samples, the bacterial amounts on day 3 and 10 were significantly lower than the baseline with and without tongue cleaning. Principal component analysis showed that variations of bacterial amounts in the tongue coating and dental plaque samples were independent from each other. Furthermore, we found a strong association between amounts of total bacteria and F. nucleatum in specimens both. CONCLUSIONS: Tongue cleaning reduced the amount of bacteria in tongue coating. However, the cleaning had no obvious contribution to inhibit dental plaque formation. Furthermore, recovery of the total bacterial amount induced an increase in F. nucleatum in both tongue coating and dental plaque. Thus, it is recommended that tongue cleaning and tooth brushing should both be performed for promoting oral health
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Exquisite Tumor Targeting by Salmonella A1-R in Combination with Caffeine and Valproic Acid Regresses an Adult Pleomorphic Rhabdomyosarcoma Patient-Derived Orthotopic Xenograft Mouse Model.
Adult pleomorphic rhabdomyosarcoma (RMS) is a rare and malignant mesenchymal tumor. Recently, we developed a patient-derived orthotopic xenograft (PDOX) model of adult pleomorphic RMS. In the present study, we evaluated the efficacy of tumor-targeting Salmonella typhimurium (S. typhimurium) A1-R combined with caffeine (CAF) and valproic acid (VPA) on the adult RMS PDOX. An adult pleomorphic RMS cell line was established from the PDOX model. Cell survival after exposure to CAF and VPA was assessed, and the IC50 value was calculated for each drug. The RMS PDOX models were randomized into five groups: untreated control; tumor treated with cyclophosphamide (CPA); tumor treated with CAF + VPA; tumor treated with S. typhimurium A1-R; and tumor treated with S. typhimurium A1-R + CAF + VPA. Tumor size and body weight was measured twice a week. VPA caused a concentration-dependent cytocidal effect. A synergistic effect of combination treatment with CAF was observed against the RMS cell line. For the in vivo study, all treatments significantly inhibited tumor growth compared with the untreated control. S. typhimurium A1-R combined with VPA and CAF was significantly more effective than CPA, VPA combined with CAF, or S. typhimurium A1-R alone and significantly regressed the tumor volume compared with day 0. These results suggest that S. typhimurium A1-R together with VPA and CAF could regresses an adult pleomorphic RMS in a PDOX model and therefore has important future clinical potential
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