2,914 research outputs found
Saliva-based colorimetric test as an index of gingival inflammation in epidemiologic studies
– There is a pressing need for a reliable, low-cost method of assessing the gingival and periodontal status of large population groups. Existing indexes, despite their value in dental public health, are still too subject to examiner variability for use by uncalibrated examiners. This study describes an evaluation of a quick, inexpensive, extraoral colorimetric test for gingival inflammation, based on a reaction between saliva and the test material. It could probably be applied by non-professional personnel. In this study, the test was applied to a population of elementary schoolchildren, denial hygiene students and faculty, and adult inmates of two correctional institutions. These populations were chosen on the assumption that they would exhibit varying intensities of gingival inflammation. Values obtained from the colorimetric test carried out by one researcher were compared with Gingival Index (GI) scores observed by a different examiner. Results suggest that the colorimetric test may be a valid, reliable means of detecting major differences in the prevalence of gingival inflammation in most adult populations, although having little, if any, useful application among children at the mixed dentition stage.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73489/1/j.1600-0528.1978.tb01169.x.pd
Interaction of Low - Energy Induced Gravity with Quantized Matter and Phase Transition Induced by Curvature
At high energy scale the only quantum effect of any asymptotic free and
asymptotically conformal invariant GUT is the trace anomaly of the
energy-momentum tensor. Anomaly generates the new degree of freedom, that is
propagating conformal factor. At lower energies conformal factor starts to
interact with scalar field because of the violation of conformal invariance. We
estimate the effect of such an interaction and find the running of the
nonminimal coupling from conformal value to . Then we discuss
the possibility of the first order phase transition induced by curvature in a
region close to the stable fixed point and calculate the induced values of
Newtonian and cosmological constants.Comment: 11 pages, LaTex, KEK-TH-397-KEK Preprint 94-3
HI intensity mapping : a single dish approach
We discuss the detection of large scale HI intensity fluctuations using a
single dish approach with the ultimate objective of measuring the Baryonic
Acoustic Oscillations and constraining the properties of dark energy. We
present 3D power spectra, 2D angular power spectra for individual redshift
slices, and also individual line-of-sight spectra, computed using the S^3
simulated HI catalogue which is based on the Millennium Simulation. We consider
optimal instrument design and survey strategies for a single dish observation
at low and high redshift for a fixed sensitivity. For a survey corresponding to
an instrument with T_sys=50 K, 50 feed horns and 1 year of observations, we
find that at low redshift (z \approx 0.3), a resolution of 40 arc min and a
survey of 5000 deg^2 is close to optimal, whereas at higher redshift (z \approx
0.9) a resolution of 10 arcmin and 500 deg^2 would be necessary. Continuum
foreground emission from the Galaxy and extragalactic radio sources are
potentially a problem. We suggest that it could be that the dominant
extragalactic foreground comes from the clustering of very weak sources. We
assess its amplitude and discuss ways by which it might be mitigated. We then
introduce our concept for a single dish telescope designed to detect BAO at low
redshifts. It involves an under-illumintated static 40 m dish and a 60 element
receiver array held 90 m above the under-illuminated dish. Correlation
receivers will be used with each main science beam referenced against an
antenna pointing at one of the Celestial Poles for stability and control of
systematics. We make sensitivity estimates for our proposed system and
projections for the uncertainties on the power spectrum after 1 year of
observations. We find that it is possible to measure the acoustic scale at
z\approx 0.3 with an accuracy 2.4% and that w can be measured to an accuracy of
16%.Comment: 20 pages, 20 figures, submitted to MNRA
Mass-loss rates of Very Massive Stars
We discuss the basic physics of hot-star winds and we provide mass-loss rates
for (very) massive stars. Whilst the emphasis is on theoretical concepts and
line-force modelling, we also discuss the current state of observations and
empirical modelling, and address the issue of wind clumping.Comment: 36 pages, 15 figures, Book Chapter in "Very Massive Stars in the
Local Universe", Springer, Ed. Jorick S. Vin
Nucleon Decay Matrix Elements from Lattice QCD
We present a model-independent calculation of hadron matrix elements for all
dimension-six operators associated with baryon number violating processes using
lattice QCD. The calculation is performed with the Wilson quark action in the
quenched approximation at on a
lattice. Our results cover all the matrix elements required to estimate the
partial lifetimes of (proton,neutron)() +() decay modes. We point out the necessity of disentangling two
form factors that contribute to the matrix element; previous calculations did
not make the separation, which led to an underestimate of the physical matrix
elements. With a correct separation, we find that the matrix elements have
values 3-5 times larger than the smallest estimates employed in
phenomenological analyses of the nucleon decays, which could give strong
constraints on several GUT models. We also find that the values of the matrix
elements are comparable with the tree-level predictions of chiral lagrangian.Comment: 53 pages, 18 eps figure
Thermodynamics of (3+1)-dimensional black holes with toroidal or higher genus horizons
We examine counterparts of the Reissner-Nordstrom-anti-de Sitter black hole
spacetimes in which the two-sphere has been replaced by a surface Sigma of
constant negative or zero curvature. When horizons exist, the spacetimes are
black holes with an asymptotically locally anti-de Sitter infinity, but the
infinity topology differs from that in the asymptotically Minkowski case, and
the horizon topology is not S^2. Maximal analytic extensions of the solutions
are given. The local Hawking temperature is found. When Sigma is closed, we
derive the first law of thermodynamics using a Brown-York type quasilocal
energy at a finite boundary, and we identify the entropy as one quarter of the
horizon area, independent of the horizon topology. The heat capacities with
constant charge and constant electrostatic potential are shown to be positive
definite. With the boundary pushed to infinity, we consider thermodynamical
ensembles that fix the renormalized temperature and either the charge or the
electrostatic potential at infinity. Both ensembles turn out to be
thermodynamically stable, and dominated by a unique classical solution.Comment: 25 pages, REVTeX v3.1, contains 5 LaTeX figures. (Typos corrected,
references and minor comments added. To be published in Phys. Rev. D.
Eta Carinae and the Luminous Blue Variables
We evaluate the place of Eta Carinae amongst the class of luminous blue
variables (LBVs) and show that the LBV phenomenon is not restricted to
extremely luminous objects like Eta Car, but extends luminosities as low as
log(L/Lsun) = 5.4 - corresponding to initial masses ~25 Msun, and final masses
as low as ~10-15 Msun. We present a census of S Doradus variability, and
discuss basic LBV properties, their mass-loss behaviour, and whether at maximum
light they form pseudo-photospheres. We argue that those objects that exhibit
giant Eta Car-type eruptions are most likely related to the more common type of
S Doradus variability. Alternative atmospheric models as well as
sub-photospheric models for the instability are presented, but the true nature
of the LBV phenomenon remains as yet elusive. We end with a discussion on the
evolutionary status of LBVs - highlighting recent indications that some LBVs
may be in a direct pre-supernova state, in contradiction to the standard
paradigm for massive star evolution.Comment: 27 pages, 6 figures, Review Chapter in "Eta Carinae and the supernova
imposters" (eds R. Humphreys and K. Davidson) new version submitted to
Springe
Measurements of Light Nuclei Production in 11.5 A GeV/c Au+Pb Heavy-Ion Collisions
We report on measurements by the E864 experiment at the BNL-AGS of the yields
of light nuclei in collisions of Au(197) with beam momentum of 11.5 A GeV/c on
targets of Pb(208) and Pt(197). The yields are reported for nuclei with baryon
number A=1 up to A=7, and typically cover a rapidity range from y(cm) to
y(cm)+1 and a transverse momentum range of approximately 0.1 < p(T)/A < 0.5
GeV/c. We calculate coalescence scale factors B(A) from which we extract model
dependent source dimensions and collective flow velocities. We also examine the
dependences of the yields on baryon number, spin, and isospin of the produced
nuclei.Comment: 21 figures-to be published in Phys. Rev.
On the nature of the galactic early-B hypergiants
Despite their importance to a number of astrophysical fields, the lifecycles
of very massive stars are still poorly defined. In order to address this
shortcoming, we present a detailed quantitative study of the physical
properties of four early-B hypergiants (BHGs); Cyg OB2 #12, zeta Sco, HD190603
and BP Cru. These are combined with an analysis of their long-term
spectroscopic and photometric behaviour in order to determine their
evolutionary status. The long-term datasets revealed that they are remarkably
stable over long periods (>40yr), with the possible exception of zeta Sco prior
to the 20th century, in contrast to the typical excursions that characterise
luminous blue variables (LBVs). Zeta Sco, HD190603 and BP Cru possess physical
properties intermediate between B supergiants and LBVs; we therefore suggest
that BHGs are the immediate descendants and progenitors (respectively) of such
stars (for initial masses in the range ~30-60Msun). In contrast, while the wind
properties of Cyg OB2 #12 are consistent with this hypothesis, the combination
of extreme luminosity and spectroscopic mass (~110Msun) and comparatively low
temperature means it cannot be accommodated in such a scheme. Likewise, despite
its co-location with several LBVs above the Humphreys-Davidson (HD) limit, the
lack of long term variability and its unevolved chemistry apparently excludes
such an identification. Since such massive stars are not expected to evolve to
such cool temperatures, the properties of Cyg OB2 #12 are difficult to
understand under current evolutionary paradigms. [ABRIDGED]Comment: 36 pages, 19 figures (of which 17 pages are online supplemental
material). Accepted for publication in Astronomy and Astrophysic
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