38,191 research outputs found
Determination of nitrogen monoxide in high purity nitrogen gas with an atmospheric pressure ionization mass spectrometer
An atmospheric pressure ionization mass spectrometric (API-MS) method was studied for the determination of residual NO in high purity N2 gas. The API-MS is very sensitive to NO, but the presence of O2 interferes with the NO measurement. Nitrogen gas in cylinders as sample gas was mixed with NO standard gas and/or O2 standard gas, and then introduced into the API-MS. The calibration curves of NO and O2 has linearity in the region of 0 - 2 ppm, but the slopes changed with every cylinder. The effect of O2 on NO+ peak was additive and proportional to O2 concentration in the range of 0 - 0.5 ppm. The increase in NO+ intensity due to O2 was (0.07 - 0.13)%/O2, 1 ppm. Determination of NO and O2 was carried out by the standard addition method to eliminate the influence of variation of slopes. The interference due to O2 was estimated from the product of the O2 concentration and the ratio of slope A to Slope B. Slope A is the change in the NO+ intensity with the O2 concentration. Slope B is the intensity with O2 concentration
Multichannel dynamical symmetry and cluster-coexistence
A composite symmetry of the nuclear structure, called multichannel dynamical
symmetry is established. It can describe different cluster configurations
(defined by different reaction channels) in a unified framework, thus it has a
considerable predictive power. The two-channel case is presented in detail, and
its conceptual similarity to the dynamical supersymmetry is discussed.Comment: published in Phys. Rev. C 87,067301 (2013
Discovery of Extremely Large-Amplitude Quasi-Periodic Photometric Variability in WC9-Type Wolf-Rayet Binary, WR 104
We discovered that the Wolf-Rayet (WR)+OB star binary, WR 104, renowned for
its associated "dusty pinwheel nebula" recently spatially resolved with
infrared interferometry, exhibits strong quasi-periodic optical variations with
a full amplitude of 2.7 mag. Such a large-amplitude, continuous variation has
been unprecedented in a WR star. The optical quasi-period (~241 d) is in almost
perfect agreement with the interferometric period (243.5+/-3 d). The remarkable
agreement of the dominant period in optical variability with the orbital period
supports that the strongly varying dust obscuration is physically related to
the binary motion, rather than sporadic dust-forming episodes. Considering the
low orbital inclination (11+/-7 deg) and the nearly circular orbit inferred
from the interferometric observations, the strongly variable line-of-sight
extinction suggests that the highly structured extinction can be being formed
via an ejection of dust in the direction of the binary rotation axis. Another
viable explanation is that the three-dimensional structure of the shock front,
itself is the obscuring body. Depending on the geometry, the dusty shock front
near the conjunction phase of the binary can completely obscure the inner
WR-star wind and the OB star, which can explain the amplitude of optical fading
and the past observation of remarkable spectral variation.Comment: 5 pages, 4 figures, to appear in PASJ (Letters), using an alternative
style fil
Deep Transient Optical Fading in the WC9 Star WR 106
We discovered that the WR9-type star WR 106 (HDE 313643) underwent a deep
episodic fading in 2000. The depth of the fading (dV ~ 2.9 mag) surpassed those
of all known similar "eclipse-like" fadings in WR stars. This fading episode
was likely to be produced by a line-of-sight episodic dust formation rather
than a periodic enhancement of dust production in the WR-star wind during the
passage of the companion star though an elliptical orbit. The overall 2000
episode was composed of at least two distinct fadings. These individual fadings
seem to more support that the initial dust formation triggered a second dust
formation, or that the two independent dust formations occurred by the same
triggering mechanism rather than a stepwise dust formation. We also discuss on
phenomenological similarity of the present fading with the double fading of R
CrB observed in 1999-2000.Comment: 3 pages, 4 figures, to appear in Astron. Astrophys. (Letters
Ramification theory for varieties over a local field
We define generalizations of classical invariants of wild ramification for
coverings on a variety of arbitrary dimension over a local field. For an l-adic
sheaf, we define its Swan class as a 0-cycle class supported on the wild
ramification locus. We prove a formula of Riemann-Roch type for the Swan
conductor of cohomology together with its relative version, assuming that the
local field is of mixed characteristic.
We also prove the integrality of the Swan class for curves over a local field
as a generalization of the Hasse-Arf theorem. We derive a proof of a conjecture
of Serre on the Artin character for a group action with an isolated fixed point
on a regular local ring, assuming the dimension is 2.Comment: 159 pages, some corrections are mad
High efficiency dark-to-bright exciton conversion in carbon nanotubes
We report that dark excitons can have a large contribution to the emission
intensity in carbon nanotubes due to an efficient exciton conversion from a
dark state to a bright state. Time-resolved photoluminescence measurements are
used to investigate decay dynamics and diffusion properties of excitons, and we
obtain intrinsic lifetimes and diffusion lengths of bright excitons as well as
diffusion coefficients for both bright and dark excitons. We find that the
dark-to-bright transition rates can be considerably high, and that more than
half of the dark excitons can be transformed into the bright excitons. The
state transition rates have a large chirality dependence with a family pattern,
and the conversion efficiency is found to be significantly enhanced by adsorbed
air molecules on the surface of the nanotubes. Our findings show the nontrivial
significance of the dark excitons on the emission kinetics in low dimensional
materials, and demonstrate the potential for engineering the dark-to-bright
conversion process by using surface interactions.Comment: 7 pages, 4 figure
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