34,867 research outputs found
Average age at death in infancy and infant mortality level: reconsidering the Coale-Demeny formulas at current levels of low mortality
The longterm historical decline in infant mortality has been accompanied by increasing concentration of infant deaths at the earliest stages of infancy. The influence of prenatal and neonatal conditions has become increasingly dominant relative to postnatal conditions as external causes of death such as infectious disease have been diminished. In the mid-1960s Coale and Demeny developed formulas describing the dependency of the average age of death in infancy on the level of infant mortality. Almost at the same time as Coale and Demeny’s analysis, as shown in this paper, in the more developed countries a steady rise in average age of infant death began. This paper demonstrates this phenomenon with several different data sources, including the linked individual birth and infant death datasets available from the US National Center for Health Statistics and the Human Mortality Database. A possible explanation for the increase in average age of death in infancy is proposed, and modifications of the Coale-Demeny formulas for practical application to contemporary low levels of mortality are offered.
Development of the elevation drive assembly for orbiting solar observatory I (EYE)
The requirements for pointing accuracy, friction, and power for the elevation drive assembly of an orbiting space observatory are discussed briefly. A description of the components making up the assembly is presented. Special features requiring development testing prior to unit fabrication are more fully described together with a review of the test programs conducted and results obtained
Coherent Exclusive Exponentiation for Precision Monte Carlo Calculations of Fermion Pair Production / Precision Predictions for (Un)stable W+W- Pairs
We present the new Coherent Exclusive Exponentiation (CEEX), in comparison to
the older Exclusive Exponentiation (EEX) and the semi-analytical Inclusive
Exponentiation (IEX), for the process e+e- -> f-bar f + n(gamma),
f=mu,tau,d,u,s,c,b, with validity for centre of mass energies from tau lepton
threshold to 1 TeV. We analyse 2f numerical results at the Z-peak, 189 GeV and
500 GeV. We also present precision calculations of the signal processes e+e- ->
4f in which the double resonant W+W- intermediate state occurs using our
YFSWW3-1.14 MC. Sample 4f Monte Carlo data are explicitly illustrated in
comparison to the literature at LEP2 energies. These comparisons show that a TU
for the signal process cross section of 0.4 percent is valid for the LEP2 200
GeV energy. LC energy results are also shown.Comment: 5 pages, 4 figures, Presented at ICHEP200
W-Pair Production with YFSWW/KoralW
A theoretical description of W-pair production in terms of two complementary
Monte Carlo event generators YFSWWand KoralW is presented. The way to combine
the results of these two programs in order to get precise predictions for WW
physics at LEP2 and LC energies is discussed.Comment: LateX file, 6 pages, conference contributio
Precision W-pair physics with the YFSWW3 and KoralW Monte Carlos
We present the recent developments in the precision studies of W-pair and
single-W processes in e+e- collisions achieved with the help of the KoralW and
YFSWW3 Monte Carlo generators. We focus on the theoretical precision of the
measurements of M_W and anomalous couplings on the example of lambda coupling.
We present the mechanism of running these two independent codes in the form of
one Concurrent Monte Carlo code. We describe also the extensions of KoralW
necessary to emulate the kinematical region of single-W process.Comment: Talk given by M. Skrzypek at 6th International Symposium on Radiative
Corrections, 8-13 September 2002, Kloster Banz, German
Psychological Issues in Online Adaptive Task Allocation
Adaptive aiding is an idea that offers potential for improvement over many current approaches to aiding in human-computer systems. The expected return of tailoring the system to fit the user could be in the form of improved system performance and/or increased user satisfaction. Issues such as the manner in which information is shared between human and computer, the appropriate division of labor between them, and the level of autonomy of the aid are explored. A simulated visual search task was developed. Subjects are required to identify targets in a moving display while performing a compensatory sub-critical tracking task. By manipulating characteristics of the situation such as imposed task-related workload and effort required to communicate with the computer, it is possible to create conditions in which interaction with the computer would be more or less desirable. The results of preliminary research using this experimental scenario are presented, and future directions for this research effort are discussed
First Observations of the Magnetic Field Geometry in Pre-stellar Cores
We present the first published maps of magnetic fields in pre-stellar cores,
to test theoretical ideas about the way in which the magnetic field geometry
affects the star formation process. The observations are JCMT-SCUBA maps of 850
micron thermal emission from dust. Linear polarizations at typically ten or
more independent positions in each of three objects, L1544, L183 and L43 were
measured, and the geometries of the magnetic fields in the plane of the sky
were mapped from the polarization directions. The observed polarizations in all
three objects appear smooth and fairly uniform. In L1544 and L183 the mean
magnetic fields are at an angle of around 30 degrees to the minor axes of the
cores. The L43 B-field appears to have been influenced in its southern half,
such that it is parallel to the wall of a cavity produced by a CO outflow from
a nearby T Tauri star, whilst in the northern half the field appears less
disturbed and has an angle of 44 degrees to the core minor axis. We briefly
compare our results with published models of magnetized cloud cores and
conclude that no current model can explain these observations simultaneously
with previous ISOCAM data.Comment: 13 pages, 3 figs, to appear in ApJ Letter
Melt-growth dynamics in CdTe crystals
We use a new, quantum-mechanics-based bond-order potential (BOP) to reveal
melt-growth dynamics and fine-scale defect formation mechanisms in CdTe
crystals. Previous molecular dynamics simulations of semiconductors have shown
qualitatively incorrect behavior due to the lack of an interatomic potential
capable of predicting both crystalline growth and property trends of many
transitional structures encountered during the melt crystal
transformation. Here we demonstrate successful molecular dynamics simulations
of melt-growth in CdTe using a BOP that significantly improves over other
potentials on property trends of different phases. Our simulations result in a
detailed understanding of defect formation during the melt-growth process.
Equally important, we show that the new BOP enables defect formation mechanisms
to be studied at a scale level comparable to empirical molecular dynamics
simulation methods with a fidelity level approaching quantum-mechanical method
Exact Gauge Invariant YFS Exponentiated Monte Carlo for (Un)Stable for (Un)Stable Production At and Beyond LEP2 Energies
We realize, by Monte Carlo event generator methods, the exact O}(\alpha)e^+e^- \to W^+ W^- (\to f_1\bar f'_1 + \bar f_2
f'_2)f_if'_iSU_{2L}i=1,2n(\gamma)W^+ W^-$. Sample Monte Carlo data are illustrated.Comment: 12 pages, 4 figures, 1 Latex file which includes the figure
- …