42,325 research outputs found
General pattern of the turbid water in the Seto-inland sea extracted from multispectral imageries by the LANDSAT-1 and 2
The author has identified the following significant results. Each distribution pattern of turbid water changes with the time in accordance with daily tides, seasonal variation of tides, and occasional rainfall. Two cases of successfully repeated LANDSAT observations for the same sea regions suggested a general pattern of turbid water could be extracted for each region. Photographic and digital processes were used to extract patterns of turbid water separately from the cloud and smog-layer in MSS 4, 5, and 7 imageries. A mosaic of image-masked imageries displays a general pattern of turbid water for almost the entire Seto Inland Sea. No such pattern was extracted for the Aki-Nada south of Hiroshima City where the water is fairly polluted, nor for the Iyo-Nada where the water is generally clearer than in other regions of the Seto Inland Sea
Formation and structure of equatorial anticyclones caused by large scale cross equatorial flows determined by ATS-1 photographs
Atmospheric models for cross equatorial air mass flow and anticyclone formatio
Fermi Surface Reconstruction without Breakdown of Kondo Screening at Quantum Critical Point
Motivated by recent Hall-effect experiment in YbRhSi, we study ground
state properties of a Kondo lattice model in a two-dimensional square lattice
using variational Monte Carlo method. We show that there are two types of phase
transition, antiferromagnetic transition and topological one (Fermi surface
reconstruction). In a wide region of parameters, these two transitions occur
simultaneously without the breakdown of Kondo screening, accompanied by a
discontinuous change of the Hall coefficient. This result is consistent with
the experiment and gives a novel theoretical picture for the quantum critical
point in heavy fermion systems.Comment: 4 pages, 3 figures, submitted to Physical Review Letter
Absence of the impurity-induced magnetic order in the electron-doped high-T_c_ cuprates Pr_0.86_LaCe_0.14_Cu_1-y_(Zn, Ni)_y_O_4_
Zero-field muon-spin-relaxation measurements have been carried out in order
to investigate the Zn- and Ni-substitution effects on the Cu-spin dynamics in
the electron-doped Pr_0.86_LaCe_0.14_Cu_1-y_(Zn, Ni)_y_O_4+\alpa-\delta_ with y
= 0, 0.01, 0.02, 0.05 and different values of the reduced oxygen content
\delta(\delta \le 0.09). For the samples with y = 0 and very small \delta
values of \delta < 0.01, a muon-spin precession due to the formation of a
long-range antiferromagnetic order has been observed at low temperatures below
\~ 5 K. For the moderately oxygen-reduced samples of 0.01 \le \delta \le 0.09,
on the contrary, no muon-spin precession has been observed and the temperature
dependence of the spectra is similar to one another regardless of the y value.
That is, no impurity-induced slowing down of the Cu-spin fluctuations has been
detected, which is very different from the results of the hole-doped high-T_c_
cuprates. The reason is discussed.Comment: 13 pages, 2 figures, Proceedings of ISS2004 (to be published in
Physica C
A Maximum Mass-to-Size Ratio in Scalar-Tensor Theories of Gravity
We derive a modified Buchdahl inequality for scalar-tensor theories of
gravity. In general relativity, Buchdahl has shown that the maximum value of
the mass-to-size ratio, , is 8/9 for static and spherically symmetric
stars under some physically reasonable assumptions. We formally apply
Buchdahl's method to scalar-tensor theories and obtain theory-independent
inequalities. After discussing the mass definition in scalar-tensor theories,
these inequalities are related to a theory-dependent maximum mass-to-size
ratio. We show that its value can exceed not only Buchdahl's limit, 8/9, but
also unity, which we call {\it the black hole limit}, in contrast to general
relativity. Next, we numerically examine the validity of the assumptions made
in deriving the inequalities and the applicability of our analytic results. We
find that the assumptions are mostly satisfied and that the mass-to-size ratio
exceeds both Buchdahl's limit and the black hole limit. However, we also find
that this ratio never exceeds Buchdahl's limit when we impose the further
condition, , on the density, , and pressure, , of the
matter.Comment: 23 pages, 13 figures and 1 tabl
An infrared measurement of chemical desorption from interstellar ice analogues
In molecular clouds at temperatures as low as 10 K, all species except
hydrogen and helium should be locked in the heterogeneous ice on dust grain
surfaces. Nevertheless, astronomical observations have detected over 150
different species in the gas phase in these clouds. The mechanism by which
molecules are released from the dust surface below thermal desorption
temperatures to be detectable in the gas phase is crucial for understanding the
chemical evolution in such cold clouds. Chemical desorption, caused by the
excess energy of an exothermic reaction, was first proposed as a key molecular
release mechanism almost 50 years ago. Chemical desorption can, in principle,
take place at any temperature, even below the thermal desorption temperature.
Therefore, astrochemical net- work models commonly include this process.
Although there have been a few previous experimental efforts, no infrared
measurement of the surface (which has a strong advantage to quantify chemical
desorption) has been performed. Here, we report the first infrared in situ
measurement of chemical desorption during the reactions H + H2S -> HS + H2
(reaction 1) and HS + H -> H2S (reaction 2), which are key to interstellar
sulphur chemistry. The present study clearly demonstrates that chemical
desorption is a more efficient process for releasing H2S into the gas phase
than was previously believed. The obtained effective cross-section for chemical
desorption indicates that the chemical desorption rate exceeds the
photodesorption rate in typical interstellar environments
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