1,422 research outputs found
Dimensional Changes in Dental Stone and Plaster
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66786/2/10.1177_00220345500290060601.pd
Cladoceran birth and death rates estimates
I. Birth and death rates of natural cladoceran populations cannot be measured directly. Estimates of these population parameters must be calculated using methods that make assumptions about the form of population growth. These methods generally assume that the population has a stable age distribution.
2. To assess the effect of variable age distributions, we tested six egg ratio methods for estimating birth and death rates with data from thirty-seven laboratory populations of Daphnia pulicaria. The populations were grown under constant conditions, but the initial age distributions and egg ratios of the populations varied. Actual death rates were virtually zero, so the difference between the estimated and actual death rates measured the error in both birth and death rate estimates.
3. The results demonstrate that unstable population structures may produce large errors in the birth and death rates estimated by any of these methods. Among the methods tested, Taylor and Slatkin's formula and Paloheimo's formula were most reliable for the experimental data.
4. Further analyses of three of the methods were made using computer simulations of growth of age-structured populations with initially unstable age distributions. These analyses show that the time interval between sampling strongly influences the reliability of birth and death rate estimates. At a sampling interval of 2.5 days (equal to the duration of the egg stage), Paloheimo's formula was most accurate. At longer intervals (7.5–10 days), Taylor and Slatkin's formula which includes information on population structure was most accurate
Dynamics with Infinitely Many Derivatives: The Initial Value Problem
Differential equations of infinite order are an increasingly important class
of equations in theoretical physics. Such equations are ubiquitous in string
field theory and have recently attracted considerable interest also from
cosmologists. Though these equations have been studied in the classical
mathematical literature, it appears that the physics community is largely
unaware of the relevant formalism. Of particular importance is the fate of the
initial value problem. Under what circumstances do infinite order differential
equations possess a well-defined initial value problem and how many initial
data are required? In this paper we study the initial value problem for
infinite order differential equations in the mathematical framework of the
formal operator calculus, with analytic initial data. This formalism allows us
to handle simultaneously a wide array of different nonlocal equations within a
single framework and also admits a transparent physical interpretation. We show
that differential equations of infinite order do not generically admit
infinitely many initial data. Rather, each pole of the propagator contributes
two initial data to the final solution. Though it is possible to find
differential equations of infinite order which admit well-defined initial value
problem with only two initial data, neither the dynamical equations of p-adic
string theory nor string field theory seem to belong to this class. However,
both theories can be rendered ghost-free by suitable definition of the action
of the formal pseudo-differential operator. This prescription restricts the
theory to frequencies within some contour in the complex plane and hence may be
thought of as a sort of ultra-violet cut-off.Comment: 40 pages, no figures. Added comments concerning fractional operators
and the implications of restricting the contour of integration. Typos
correcte
SRAO CO Observation of 11 Supernova Remnants in l = 70 to 190 deg
We present the results of 12CO J = 1-0 line observations of eleven Galactic
supernova remnants (SNRs) obtained using the Seoul Radio Astronomy Observatory
(SRAO) 6-m radio telescope. The observation was made as a part of the SRAO CO
survey of SNRs between l = 70 and 190 deg, which is intended to identify SNRs
interacting with molecular clouds. The mapping areas for the individual SNRs
are determined to cover their full extent in the radio continuum. We used
halfbeam grid spacing (60") for 9 SNRs and full-beam grid spacing (120") for
the rest. We detected CO emission towards most of the remnants. In six SNRs,
molecular clouds showed a good spatial relation with their radio morphology,
although no direct evidence for the interaction was detected. Two SNRs are
particularly interesting: G85.4+0.7, where there is a filamentary molecular
cloud along the radio shell, and 3C434.1, where a large molecular cloud appears
to block the western half of the remnant. We briefly summarize the results
obtained for individual SNRs.Comment: Accepted for publication in Astrophysics & Space Science. 12 pages,
12 figures, and 3 table
Measurements of exclusive B_s^0 decays at the Y(5S) resonance
Several exclusive decays are studied using a 1.86 fb-1 data sample
collected at the Y(5S) resonance with the Belle detector at the KEKB asymmetric
energy e^+ e^- collider. In the decay mode we find 10
candidates and measure the corresponding branching fraction. Combining
the B_s^0 -> D_s^{(*)-} \pi^+, B_s^0 -> D_s^{(*)-} \rho^+, B_s^0 -> J/\psi \phi
and B_s^0 -> J/\psi \eta decay modes, a significant signal is observed.
The ratio \sigma (e^+ e^- -> B_s^* \bar{B}_s^*) / \sigma (e^+ e^- -> B_s^{(*)}
\bar{B}_s^{(*)}) = (93^{+7}_{-9} \pm 1)% is obtained at the Y(5S) energy,
indicating that meson production proceeds predominantly through the
creation of pairs. The and meson masses are
measured to be M(B_s^0)=(5370 \pm 1 \pm 3)MeV/c^2 and M(B_s^*)=(5418 \pm 1 \pm
3)MeV/c^2. Upper limits on the B_s^0 -> \gamma \gamma, B_s^0 -> \phi \gamma,
B_s^0 -> K^+ K^- and B_s^0 -> D_s^{(*)+} D_s^{(*)-} branching fractions are
also reported.Comment: 9 pages, 5 figures, published in Phys. Rev. D76, 012002 (2007
Search for Resonant Decays at Belle
We report measurements and searches for resonant decays where is a
meson or
the X(3872) particle.Comment: accepted by Physics Letters
Study of charmonia in four-meson final states produced in two-photon collisions
We report measurements of charmonia produced in two-photon collisions and
decaying to four-meson final states, where the meson is either a charged pion
or a charged kaon. The analysis is based on a 395fb^{-1} data sample
accumulated with the Belle detector at the KEKB electron-positron collider. We
observe signals for the three C-even charmonia eta_c(1S), chi_{c0}(1P) and
chi_{c2}(1P) in the pi^+pi^-pi^+pi^-, K^+K^-pi^+pi^- and K^+K^-K^+K^- decay
modes. No clear signals for eta_c(2S) production are found in these decay
modes. We have also studied resonant structures in charmonium decays to
two-body intermediate meson resonances. We report the products of the
two-photon decay width and the branching fractions, Gamma_{gamma gamma}B, for
each of the charmonium decay modes.Comment: 22 pages, 12 figure
Moments of the Hadronic Invariant Mass Spectrum in B --> X_c l nu Decays at Belle
We present a measurement of the hadronic invariant mass squared (M^2_X)
spectrum in charmed semileptonic B meson decays B --> X_c l nu based on 140
fb^-1 of Belle data collected near the Y(4S) resonance. We determine the first,
the second central and the second non-central moments of this spectrum for
lepton energy thresholds ranging between 0.7 and 1.9 GeV. Full correlations
between these measurements are evaluated.Comment: published version of the paper (one figure added, minor changes in
the text); 16 pages, 3 figures, 10 table
Observation of Ds1(2536)+ -> D+pi-K+ and angular decomposition of Ds1(2536)+ -> D*+K0S
Using 462/fb of e+e- annihilation data recorded by the Belle detector, we
report the first observation of the decay Ds1(2536)+ -> D+pi-K+. The ratio of
branching fractions B(Ds1+ -> D+pi-K+)/B(Ds1+ -> D*+K0) is measured to be
(3.27+-0.18+-0.37)%. We also study the angular distributions in the Ds1(2536)+
-> D*+K0S decay and measure the ratio of D- and S-wave amplitudes. The S-wave
dominates, with a partial width of Gamma_S/Gamma_total=0.72+-0.05+-0.01.Comment: Submitted to Phys.Rev.D 16 pages, 6 figures, 3 table
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