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Data assimilation insights on selecting the most valuable atmospheric measurements
We discuss how objective guidance on selecting the most valuable atmospheric measurements on future Mars spacecraft missions can be provided through already developed Martian atmospheric data assimilation systems, and in particular through Observing System Simulation Experiments (OSSEs) which are widely used to design instruments for the Earth’s atmosphere
Synthesis, Characterization, and Magnetic Properties of gamma-NaxCoO2 (0.70 < x <0.84)
Powder NaCoO () samples were synthesized and
characterized carefully by X-ray diffraction analysis, inductive-coupled plasma
atomic emission spectroscopy, and redox titration. It was proved that
-NaCoO is formed only in the narrow range of . Nevertheless, the magnetic properties depend strongly on . We
found, for the first time, two characteristic features in the magnetic
susceptibility of NaCoO, a sharp peak at K and an
anomaly at K, as well as the transition at K and the broad
maximum at K which had already been reported. A type of weak
ferromagnetic transition seems to occur at . The transition at ,
which is believed to be caused by spin density wave formation, was observed
clearly for with constant and independent of .
On the other hand, ferromagnetic moment varies systematically depending on .
These facts suggest the occurrence of a phase separation at the microscopic
level, such as the separation into Na-rich and Na-poor domains due to the
segregation of Na ions. The magnetic phase diagram and transition mechanism
proposed previously should be reconsidered.Comment: 4 pages (2 figures included) and 2 extra figures (gif), to be
published in J. Phys. Soc. Jpn. 73 (8) with possible minor revision
Survey of long-term variability of stars I. Reliability of magnitudes in old star catalogues
The comparison of visual magnitudes of stars compiled in old catalogues is
expected to yield information about their long-term magnitude variations. In
seven old catalogues whose historical data have been intensively compared, 2123
sampled stars have been studied, disregarding stars that we could not identify,
double stars which could be misidentified, or stars observed under poor
conditions, and known variable stars with large amplitude discrepancies. The
independence of stellar magnitude catalogues is demonstrated by comparing seven
old studies to each other, suggesting that the magnitude estimates in each
catalogue reflect the brightness at each observational period. Furthermore, by
comparing them with a modern star catalogue, the magnitude differences show a
Gaussian distribution. Therefore, if they are sufficiently larger than the
deduced standard deviations, the magnitude variations between the catalogues
can be considered real. Thus, the stellar magnitudes compiled in old studies
can be used as scientific data within the average intrinsic uncertainty. These
seven old catalogues can be used as data for the survey of the long-term
variability of stars.Comment: 7 pages including 2 figures, accepted for publication in A&
A Possible Phase Transition in beta-pyrochlore Compounds
We investigate a lattice of interacting anharmonic oscillators by using a
mean field theory and exact diagonalization. We construct an effective
five-state hopping model with intersite repulsions as a model for
beta-pyrochlore AOs_2O_6(A=K, Rb or Cs). We obtain the first order phase
transition line from large to small oscillation amplitude phases as temperature
decreases. We also discuss the possibility of a phase with local electric
polarizations. Our theory can explain the origin of the mysterious first order
transition in KOs_2O_6.Comment: 4 pages, 4 figures, submitted to J. Phys. Soc. Jp
Genetic diversity of Mycobacterium tuberculosis isolates from foreign-born and Japan-born residents in Tokyo
AbstractSequences of the full genomes of 259 clinical isolates of Mycobacterium tuberculosis, obtained from foreign-born and Japan-born patients in Tokyo, Japan, were determined, and a phylogenetic tree constructed by concatenated single-nucleotide polymorphism (SNP) sequences. The 259 isolates were clustered into four clades: Lineage 2 (East Asian or “Beijing” genotype; n = 182, 70.3%), Lineage 4 (Euro-American, n = 46, 17.8%), Lineage 1 (Indo-Oceanic, n = 23, 8.9%), and Lineage 3 (East African-Indian, n = 8, 3.1%). Of the 259, 36 (13.9%) were resistant to at least one drug. There was no multi-drug-resistant isolate. Drug resistance was greater for the strains in Lineage 2 than the non-Lineage 2. The proportion of Lineage 2 isolates was significantly smaller in foreign-born (n = 43/91, 47.3%) than in Japan-born (n = 139/168, 82.7%) patients, whereas the proportion of Lineage 1 isolates was significantly larger in foreign-born (n = 19/91, 20.9%) than in Japan-born (n = 4/168, 2.4%) patients. We also found eight SNPs specific to the typical Beijing sub-genotype in Lineage 2, including 4 non-synonymous SNPs. Of the 259 isolates, 244 had strain-specific SNP(s) and small (1–30-bp) insertions and deletions (indels). The numbers of strain-specific SNPs and indels per isolate were significantly larger from foreign-born (median 89, range 0–520) than from Japan-born (median 23, range 0–415) (p 3.66E-15) patients. These results suggested that M. tuberculosis isolates from foreign-born patients had more genetic diversity than those from Japan-born patients
Primordial fractal density perturbations and structure formation in the Universe: 1-Dimensional collisionless sheet model
Two-point correlation function of galaxy distribution shows that the
structure in the present Universe is scale-free up to a certain scale (at least
several tens Mpc), which suggests that a fractal structure may exist. If small
primordial density fluctuations have a fractal structure, the present
fractal-like nonlinear structure below the horizon scale could be naturally
explained. We analyze the time evolution of fractal density perturbations in
Einstein-de Sitter universe, and study how the perturbation evolves and what
kind of nonlinear structure will come out. We assume a one-dimensional
collisionless sheet model with initial Cantor-type fractal perturbations. The
nonlinear structure seems to approach some attractor with a unique fractal
dimension, which is independent of the fractal dimensions of initial
perturbations. A discrete self-similarity in the phase space is also found when
the universal nonlinear fractal structure is reached.Comment: 17 pages, 19 jpeg figures. Accepted for publication in ApJ. Figures
are also available from
http://www.phys.waseda.ac.jp/gravity/~tatekawa/0003124/figs.tar.g
Photon generation by laser-Compton scattering at the KEK-ATF
We performed a photon generation experiment by laser-Compton scattering at
the KEK-ATF, aiming to develop a Compton based polarized positron source for
linear colliders. In the experiment, laser pulses with a 357 MHz repetition
rate were accumulated and their power was enhanced by up to 250 times in the
Fabry-Perot optical resonant cavity. We succeeded in synchronizing the laser
pulses and colliding them with the 1.3 GeV electron beam in the ATF ring while
maintaining the laser pulse accumulation in the cavity. As a result, we
observed 26.0 +/- 0.1 photons per electron-laser pulse crossing, which
corresponds to a yield of 10^8 photons in a second.Comment: 3 pages, 5 figures, Preprint submitted to TIPP09 Proceedings in NIM
Mass-Enhanced Fermi Liquid Ground State in NaCoO
Magnetic, transport, and specific heat measurements have been performed on
layered metallic oxide NaCoO as a function of temperature .
Below a characteristic temperature =3040 K, electrical resistivity
shows a metallic conductivity with a behavior and magnetic susceptibility
deviates from the Curie-Weiss behavior showing a broad peak at 14 K. The
electronic specific heat coefficient is 60 mJ/molK at 2 K.
No evidence for magnetic ordering is found. These behaviors suggest the
formation of mass-enhanced Fermi liquid ground state analogous to that in
-electron heavy fermion compound LiVO.Comment: 4 pages, 4 figures, to be published in Phys. Rev. B 69 (2004
Distribution functions of two-dimensionally oriented magnetic particles
In this paper, the angular dependence of the magnetoremanence ratio of particulate tapes was measured. The two-dimensional distribution functions for audio /spl alpha/-Fe and /spl gamma/-Fe/sub 2/O/sub 3/ tapes were also discussed.</p
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