669 research outputs found
A Re-analysis of Caries Rates in a Preventive Trial using Poisson Regression Models
The analysis of caries incidence in clinical trials has several challenging features: (1) The distribution of the number of caries onsets per patient is skewed, with the majority of patients having few or no cavities; (2) the number of surfaces at risk varies (i) over time and (ii) between patients, due to eruption and exfoliation patterns, dental diseases, and treatments ; (3) surfaces within a patient differ in their caries susceptibility, and (4) caries onsets within a patient are correlated due to shared host factors. Recent statistical developments in the area of correlated data analyses permit incorporation of some of these characteristics into the analyses. With Poisson regression models, the expected number of caries onsets can be related to the number of surfaces at risk, the time they have been at risk, and surface- and subject-specific explanatory variables. The parameter estimated in these models is an epidemiological measure of disease occurrence: the disease incidence rate (caries rate) or the rate of change from healthy (sound) to diseased (carious). Differences and ratios of these rates provide standard epidemiological measures of excess risk. To illustrate, Poisson regression models were used for exploratory analyses of the Ylivieska xylitol study.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67228/2/10.1177_00220345940730021401.pd
Process simulation and optimal design of membrane separation system for CO2 capture from natural gas
The Glass-like Universe: Real-space correlation properties of standard cosmological models
After reviewing the basic relevant properties of stationary stochastic
processes (SSP), defining basic terms and quantities, we discuss the properties
of the so-called Harrison-Zeldovich like spectra. These correlations, usually
characterized exclusively in k-space (i.e. in terms of power spectra P(k)), are
a fundamental feature of all current standard cosmological models. Examining
them in real space we note their characteristics to be a {\it negative} power
law tail \xi(r) \sim - r^{-4} and a {\it sub-poissonian} normalised variance in
spheres \sigma^2(R) \sim R^{-4} \ln R. We note in particular that this latter
behaviour is at the limit of the most rapid decay (\sim R^{-4}) of this
quantity possible for any stochastic distribution (continuous or discrete).
This very particular characteristic is usually obscured in cosmology by the use
of Gaussian spheres. In a simple classification of all SSP into three
categories, we highlight with the name ``super-homogeneous'' the properties of
the class to which models like this, with P(0)=0, belong. In statistical
physics language they are well described as glass-like. They do not have either
``scale-invariant'' features, in the sense of critical phenomena, nor fractal
properties. We illustrate their properties with some simple examples, in
particular that of a ``shuffled'' lattice.Comment: 20 pages, 3 postscript figures, corrected some typos and minor
changes to match the accepted version in Physical Review
Review of experimental methods to determine spontaneous combustion susceptibility of coal – Indian context
This paper presents a critical review of the different techniques developed to investigate the susceptibility of coal to spontaneous combustion and fire. These methods may be sub-classified into the two following areas: (1) Basic coal characterisation studies (chemical constituents) and their influence on spontaneous combustion susceptibility. (2) Test methods to assess the susceptibility of a coal sample to spontaneous combustion. This is followed by a critical literature review that summarises previous research with special emphasis given to Indian coals
SCExAO/MEC and CHARIS Discovery of a Low Mass, 6 AU-Separation Companion to HIP 109427 using Stochastic Speckle Discrimination and High-Contrast Spectroscopy
We report the direct imaging discovery of a low-mass companion to the nearby
accelerating A star, HIP 109427, with the Subaru Coronagraphic Extreme Adaptive
Optics (SCExAO) instrument coupled with the MKID Exoplanet Camera (MEC) and
CHARIS integral field spectrograph. CHARIS data reduced with reference star PSF
subtraction yield 1.1-2.4 m spectra. MEC reveals the companion in and
band at a comparable signal-to-noise ratio using stochastic speckle
discrimination, with no PSF subtraction techniques. Combined with complementary
follow-up photometry from Keck/NIRC2, the SCExAO data favors a
spectral type, effective temperature, and luminosity of M4-M5.5, 3000-3200 ,
and , respectively.
Relative astrometry of HIP 109427 B from SCExAO/CHARIS and Keck/NIRC2, and
complementary Gaia-Hipparcos absolute astrometry of the primary favor a
semimajor axis of au, an eccentricity of
, an inclination of degrees, and a
dynamical mass of . This work shows the
potential for extreme AO systems to utilize speckle statistics in addition to
widely-used post-processing methods to directly image faint companions to
nearby stars near the telescope diffraction limit.Comment: 13 pages, 7 figures, 3 table
Production and Decay of D_1(2420)^0 and D_2^*(2460)^0
We have investigated and final states and
observed the two established charmed mesons, the with mass
MeV/c and width MeV/c and
the with mass MeV/c and width
MeV/c. Properties of these final states, including
their decay angular distributions and spin-parity assignments, have been
studied. We identify these two mesons as the doublet predicted
by HQET. We also obtain constraints on {\footnotesize } as a function of the cosine of the relative phase of the two
amplitudes in the decay.Comment: 15 pages in REVTEX format. hardcopies with figures can be obtained by
sending mail to: [email protected]
Measurement of the branching fraction for
We have studied the leptonic decay of the resonance into tau
pairs using the CLEO II detector. A clean sample of tau pair events is
identified via events containing two charged particles where exactly one of the
particles is an identified electron. We find . The result is consistent with
expectations from lepton universality.Comment: 9 pages, RevTeX, two Postscript figures available upon request, CLNS
94/1297, CLEO 94-20 (submitted to Physics Letters B
Study of the B^0 Semileptonic Decay Spectrum at the Upsilon(4S) Resonance
We have made a first measurement of the lepton momentum spectrum in a sample
of events enriched in neutral B's through a partial reconstruction of B0 -->
D*- l+ nu. This spectrum, measured with 2.38 fb**-1 of data collected at the
Upsilon(4S) resonance by the CLEO II detector, is compared directly to the
inclusive lepton spectrum from all Upsilon(4S) events in the same data set.
These two spectra are consistent with having the same shape above 1.5 GeV/c.
From the two spectra and two other CLEO measurements, we obtain the B0 and B+
semileptonic branching fractions, b0 and b+, their ratio, and the production
ratio f+-/f00 of B+ and B0 pairs at the Upsilon(4S). We report b+/b0=0.950
(+0.117-0.080) +- 0.091, b0 = (10.78 +- 0.60 +- 0.69)%, and b+ = (10.25 +- 0.57
+- 0.65)%. b+/b0 is equivalent to the ratio of charged to neutral B lifetimes,
tau+/tau0.Comment: 14 page, postscript file also available at
http://w4.lns.cornell.edu/public/CLN
Measurement of the Decay Asymmetry Parameters in and
We have measured the weak decay asymmetry parameters (\aLC ) for two \LC\
decay modes. Our measurements are \aLC = -0.94^{+0.21+0.12}_{-0.06-0.06} for
the decay mode and \aLC = -0.45\pm 0.31 \pm
0.06 for the decay mode . By combining these
measurements with the previously measured decay rates, we have extracted the
parity-violating and parity-conserving amplitudes. These amplitudes are used to
test models of nonleptonic charmed baryon decay.Comment: 11 pages including the figures. Uses REVTEX and psfig macros. Figures
as uuencoded postscript. Also available as
http://w4.lns.cornell.edu/public/CLNS/1995/CLNS95-1319.p
Observation of the Charmed Baryon Decays to , , and
We have observed two new decay modes of the charmed baryon into
and using data collected with the
CLEO II detector. We also present the first measurement of the branching
fraction for the previously observed decay mode . The branching fractions for these three modes relative to
are measured to be , , and , respectively.Comment: 12 page uuencoded postscript file, postscript file also available
through http://w4.lns.cornell.edu/public/CLN
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