853 research outputs found
Hydrophobic coating of solid materials by plasma-polymerized thin film using tetrafluoroethylene
Glass slides were coated with plasma-polymerized tetrafluoroethylene films of different thickness using the glow discharge technique in a tube-shaped chamber, and the plasma conditions, film growth rates, light permeability of the polymer films, and particle bond strength in the polymer films were studied. Ashed sections of mouse organs and ashed bacillus spores were also coated to give them hydrophobic treatment without damaging their shapes or appearance. The hydrophobic coating of the specimens was successful, and the fine ash patterns were strongly fixed onto the glass slides, making permanent preparations
A Phase-Space Approach to Collisionless Stellar Systems Using a Particle Method
A particle method for reproducing the phase space of collisionless stellar
systems is described. The key idea originates in Liouville's theorem which
states that the distribution function (DF) at time t can be derived from
tracing necessary orbits back to t=0. To make this procedure feasible, a
self-consistent field (SCF) method for solving Poisson's equation is adopted to
compute the orbits of arbitrary stars. As an example, for the violent
relaxation of a uniform-density sphere, the phase-space evolution which the
current method generates is compared to that obtained with a phase-space method
for integrating the collisionless Boltzmann equation, on the assumption of
spherical symmetry. Then, excellent agreement is found between the two methods
if an optimal basis set for the SCF technique is chosen. Since this
reproduction method requires only the functional form of initial DFs but needs
no assumptions about symmetry of the system, the success in reproducing the
phase-space evolution implies that there would be no need of directly solving
the collisionless Boltzmann equation in order to access phase space even for
systems without any special symmetries. The effects of basis sets used in SCF
simulations on the reproduced phase space are also discussed.Comment: 16 pages w/4 embedded PS figures. Uses aaspp4.sty (AASLaTeX v4.0). To
be published in ApJ, Oct. 1, 1997. This preprint is also available at
http://www.sue.shiga-u.ac.jp/WWW/prof/hozumi/papers.htm
Growth of Velocity Dispersions for Collapsing Spherical Stellar Systems
First, we have ensured that spherical nonrotating collisionless systems
collapse with almost retaining spherical configurations during initial
contraction phases even if they are allowed to collapse three-dimensionally.
Next, on the assumption of spherical symmetry, we examine the evolution of
velocity dispersions with collapse for the systems which have uniform or
power-law density profiles with Maxwellian velocity distributions by
integrating the collisionless Boltzmann equation directly. The results show
that as far as the initial contraction phases are concerned, the radial
velocity dispersion never grows faster than the tangential velocity dispersion
except at small radii where the nearly isothermal nature remains, irrespective
of the density profiles and virial ratios. This implies that velocity
anisotropy as an initial condition should be a poor indicator for the radial
orbit instability. The growing behavior of the velocity dispersions is briefly
discussed from the viewpoint that phase space density is conserved in
collisionless systems.Comment: 12 pages, including 5 postscript figures. This preprint is also
available at http://www.kcua.ac.jp/~fujiwara/e-prints/e-prints.html Submitted
to Publ.Astron.Soc.Japa
Different mechanism of acute luminal gain by coronary intervention: comparison between acute myocardial infarction and stable effort angina pectoria
Maximum entropy models for antibody diversity
Recognition of pathogens relies on families of proteins showing great
diversity. Here we construct maximum entropy models of the sequence repertoire,
building on recent experiments that provide a nearly exhaustive sampling of the
IgM sequences in zebrafish. These models are based solely on pairwise
correlations between residue positions, but correctly capture the higher order
statistical properties of the repertoire. Exploiting the interpretation of
these models as statistical physics problems, we make several predictions for
the collective properties of the sequence ensemble: the distribution of
sequences obeys Zipf's law, the repertoire decomposes into several clusters,
and there is a massive restriction of diversity due to the correlations. These
predictions are completely inconsistent with models in which amino acid
substitutions are made independently at each site, and are in good agreement
with the data. Our results suggest that antibody diversity is not limited by
the sequences encoded in the genome, and may reflect rapid adaptation to
antigenic challenges. This approach should be applicable to the study of the
global properties of other protein families
Direct visualization of a significant stenosis of the right coronary artery by transthoracic echocardiography. A case report
Non-invasive imaging of coronary arteries by transthoracic echocardiography is an emerging diagnostic tool to study the left main (LM), left descending artery (LAD), circumflex (Cx) and right coronary artery (RCA). Impaired coronary circulation can be assessed by measuring coronary velocity flow reserve (CVFR) by transthoracic Doppler echocardiography. Coronary artery stenoses can be identified as localized colour aliasing and accelerated flow velocities. We report a case with an acute coronary syndrome (ACS) of a 46-year-old man. With non-invasive imaging of coronary arteries by transthoracic echocardiography (TTE), we identified a segment of the mid right coronary artery (RCA) suggestive of stenosis with localized colour aliasing and accelerated flow velocity. We found a high ratio between the stenotic peak velocity and the prestenotic peak velocity, and a pathologic coronary flow velocity reserve (CFVR) distal to the stenosis in the posterior interventricular descending branch (RDP). Subsequent coronary angiography demonstrated one vessel disease with a stenosis in segment 3 of RCA, which was successfully treated with percutaneos coronary intervention PCI. Two weeks following the PCI procedure he was readmitted to hospital with chest pain. A subacute stent thrombosis was questioned, and repeated echocardiography was preformed. The mid portion of RCA showed normal and laminar flow. The CVFR of RCA measured in the RDP showed normal vasodilatory response, confirming an open RCA without any flow limitation. A repeated coronary angiogram demonstrated only a mild in stent intimal hyperplasia. This case illustrates the value of transthoracic echocardiography as a tool both in the diagnosis and the follow-up of chest pain disorders and coronary flow problems. Transthoracic echocardiography allows both direct visualization of the various coronary segments and assessment of the CVFR
The Self-Regulated Growth of Supermassive Black Holes
We present a series of simulations of the self--regulated growth of
supermassive black holes (SMBHs) in galaxies via three different fueling
mechanisms: major mergers, minor mergers, and disk instabilities. The SMBHs in
all three scenarios follow the same black hole fundamental plane (BHFP) and
correlation with bulge binding energy seen in simulations of major mergers, and
observed locally. Furthermore, provided that the total gas supply is
significantly larger than the mass of the SMBH, its limiting mass is not
influenced by the amount of gas available or the efficiency of black hole
growth. This supports the assertion that SMBHs accrete until they reach a
critical mass at which feedback is sufficient to unbind the gas locally,
terminating the inflow and stalling further growth. At the same time, while
minor and major mergers follow the same projected correlations (e.g., the
and Magorrian relations), SMBHs grown via disk instabilities do
not, owing to structural differences between the host bulges. This finding is
supported by recent observations of SMBHs in pseudobulges and bulges in barred
systems, as compared to those hosted by classical bulges. Taken together, this
provides support for the BHFP and binding energy correlations as being more
"fundamental" than other proposed correlations in that they reflect the
physical mechanism driving the co-evolution of SMBHs and spheroids.Comment: 15 pages, 16 figures, accepted for publication in Ap
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