10,366 research outputs found
Phase reduction of stochastic limit cycle oscillators
We point out that the phase reduction of stochastic limit cycle oscillators
has been done incorrectly in the literature. We present a correct phase
reduction method for oscillators driven by weak external white Gaussian noises.
Numerical evidence demonstrates that the present phase equation properly
approximates the dynamics of the original full oscillator system.Comment: 4 pages, 2 figure
A variety of lepton number violating processes related to Majorana neutrino masses
A Majorana type of the neutrino mass matrix induces a class of lepton number
violating processes. Cross sections of these reactions are given in terms of
the neutrino mass matrix element, and a semi-realistic event rate is estimated.
These processes provide mass and mixing parameters not directly accessible by
the neutrino oscillation experiments. If these processes are discovered with a
larger rate than given here, it would imply a new physics of the lepton number
violation not directly related to the Majorana neutrino mass, such as R-parity
violating operators in SUSY models.Comment: 15 pages, 1 figur
Orbital Properties of Sr3Ru2O7 and Related Ruthenates Probed by 17O-NMR
We report a site-separated O-NMR study of the layered perovskite
ruthenate SrRuO, which exhibits nearly two-dimensional transport
properties and itinerant metamagnetism at low temperatures. The local hole
occupancies and the spin densities in the oxygen orbitals are obtained by
means of tight-binding analyses of electric field gradients and anisotropic
Knight shifts. These quantities are compared with two other layered perovskite
ruthenates: the two-dimensional paramagnet SrRuO and the
three-dimensional ferromagnet SrRuO. The hole occupancies at the oxygen
sites are very large, about one hole per ruthenium atom. This is due to the
strong covalent character of the Ru-O bonding in this compound. The magnitude
of the hole occupancy might be related to the rotation or tilt of the RuO
octahedra. The spin densities at the oxygen sites are also large, 20-40% of the
bulk susceptibilities, but in contrast to the hole occupancies, the spin
densities strongly depend on the dimensionality. This result suggests that the
density-of-states at the oxygen sites plays an essential role for the
understanding of the complex magnetism found in the layered perovskite
ruthenates.Comment: 9 pages, 5 figures, to be published in Phys. Rev.
Time trend analysis of gastric cancer incidence in Japan by histological types, 1975-1989
Since different histological types (HT) of gastric cancer (GC) may differ in their aetiology, time trend analysis by HT may afford an insight into aetiology. From the Gastric Cancer Registry of Japan, 161 067 cases diagnosed were retrieved between 1975 and 1989 to calculate the annual relative frequencies, stratified by age group and sex, of HT according to the Lauren and the Japanese Research Society for Gastric Cancer (JRSGC) classifications. Age- and sex-specific incidence rates by HT were estimated by multiplying the corresponding national cancer incidence rates of GC by the relative frequencies. Logistic regression models stratified by sex and age group were fitted to determine the time trends of HT. Using the Lauren classification, a decreasing trend of the intestinal type and a stable trend of the diffuse type were found. By the JRSGC classification, significant decreasing trends for most age groups were found for papillary and mucinous adenocarcinomas. Tubular adenocarcinomas (well differentiated type) showed a decreasing trend only in younger age groups. Tubular (moderately differentiated type), poorly differentiated adenocarcinomas, and signet ring cell carcinoma were statistically stable during the period. Considering changes in lifestyles of the Japanese, the result suggests that there are three aetiological types of GC. © 2001 Cancer Research Campaign http://www.bjcancer.co
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