81,431 research outputs found
The Frozen Core Approximation and Nuclear Screening Effects in Single Electron Capture Collisions
Fully Differential Cross Sections (FDCS) for single electron capture from
helium by heavy ion impact are calculated using a frozen core 3-Body model and
an active electron 4-Body model within the first Born approximation. FDCS are
presented for H+, He2+, Li3+, and C6+ projectiles with velocities of 100
keV/amu, 1 MeV/amu, and 10 MeV/amu. In general, the FDCS from the two models
are found to differ by about one order of magnitude with the active electron
4-Body model showing better agreement with experiment. Comparison of the models
reveals two possible sources of the magnitude difference: the inactive
electron's change of state and the projectile-target Coulomb interaction used
in the different models. Detailed analysis indicates that the uncaptured
electron's change of state can safely be neglected in the frozen core
approximation, but that care must be used in modeling the projectile-target
interaction
Radial Velocities of Newly Discovered Globular Clusters in NGC 5128
We present radial velocity measurements for 74 globular clusters (GCs) in the
nearby giant elliptical NGC 5128, of which 31 are newly discovered clusters.
All the GC candidates were taken from the list of possible new clusters given
in the Harris, Harris, & Geisler (2004) photometric survey. In addition to the
newly confirmed clusters, we identified 24 definite foreground stars and 31
probable background galaxies. From a combined list of 299 known GCs in NGC 5128
with measured radial velocities and metallicity-sensitive (C - T_1) photometric
indices, we construct a new metallicity distribution function (MDF) for the
cluster system. The MDF shows an approximately bimodal form, with centroids at
[Fe/H] = -1.46 and -0.53, and with nearly equal numbers of metal-poor and
metal-rich clusters in the two modes. However, there are many
intermediate-color clusters in the distribution, and the fainter clusters tend
to have a higher proportion of red clusters. These features of the MDF may
indicate a widespread age range within the cluster system as well as an
intrinsically broad metallicity spread.Comment: 10 pages, 7 figures, 4 tables - accepted in Astronomical Journa
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Employers' policies for third age employment – the case for action and the rational for reaction
This paper reports on findings from a study which explores employers’ perceptions of the careers of those in third age employment and the extent to which these organisations have in place policies and practices to manage older worker careers. Drawing on interviews with UK HR managers and advisory bodies, the study finds that there was an absence of formal policies which addressed the career needs of older works despite employers being aware of the issue associated with an aging workforce. Instead employers responded to career related requests from older workers on an ad hoc basis as they felt that specific policies for this group of people would potentially create legal issues for the organisation. Employers also believed that the aged workforce had little impact on their business and as a result did not engage in collective dialogue with older workers about their requirements and instead made assumptions about their career needs
Measurement of the derivative 'ZW' for an oscillating aerofoil
This report presents the results of experimental
measurements of the damping derivative coefficient zw for
constant chord rigid wings of various aspect ratios having
sweepback angles of zero and 450.
The results for the rectangular wings Flow substantial
agreement with the unsteady aerofoil theory developed
by TI.P. Jones $2) The dependence of Zvi upon frequency parameter
is as given by theory and is much less than for two dimensional
flow, but the numerical results are approximately
10 per cent below the theoretical. This is attributed to the
large trailing edge angle 22° of the N.A.C.A. 0020 section
used for the model aerofoils.
The effect of sweepback is to decrease the numerical
value of z , but this effect is much less pronounced, for low
than for high aspect ratios. For aspect ratios 5 and 3
the numerical value is greater than would be given by a factor
of proportionality equal to the cosine of the angle of
sweepback.
The measurements were corrected for tunnel interference
by a method based on the theoretical work of 7.P.Jones.(1
Does settlement plate material matter? The influence of substrate type on fouling community development
Benthic community composition and ascidian abundance can differ dramatically between adjacent man-made and natural substrates. Although multiple factors, including light exposure, surface orientation, predation exposure, and habitat type, are known to contribute to these patterns, few studies have directly tested the influence of substrate identity on community development. We compared fouling communities on settlement plates composed of commonly occurring natural (granite) and artificial (concrete, high density polyethylene, and PVC) marine materials deployed from late May to mid November 2014 from a floating dock in Newcastle, NH. We sought to determine if observed patterns resulted from differential recruitment onto substrate materials or post-settlement survival and growth. To do this, half of the plates were cleaned during bi-weekly examinations, and half were left un-cleaned. Preliminary analyses indicate that community composition differs between substrate types. These results will help us understand how substrate features contribute to non-native species establishment and habitat dominance, and may inform decisions regarding material usage in marine construction. These findings also underline the importance of settlement substrate choice in scientific studies, as plate material may influence experimental conclusions
The control of nonlinear stochastic control systems under discounted performance criteria
Control algorithm for optimization of nonlinear stochastic processes with discounted performance criteri
Spine-sheath layer radiative interplay in subparsec-scale jets and the TeV emission from M87
Simple one-zone homogeneous synchrotron self-Compton models have severe
difficulties in explaining the TeV emission observed in the radiogalaxy M87.
Also the site of the TeV emission region is uncertain: it could be the
unresolved jet close to the nucleus, analogously to what proposed for blazars,
or an active knot, called HST-1, tens of parsec away. We explore the
possibility that the TeV emission of M87 is produced in the misaligned subpc
scale jet. We base our modelling on a structured jet, with a fast spine
surrounded by a slower layer. In this context the main site responsible for the
emission of the TeV radiation is the layer, while the (debeamed) spine accounts
for the emission from the radio to the GeV band: therefore we expect a more
complex correlation with the TeV component than that expected in one-zone
scenarios, in which both components are produced by the same region. Observed
from small angles, the spine would dominate the emission, with an overall
Spectral Energy Distribution close to those of BL Lac objects with a
synchrotron peak located at low energy (LBLs).Comment: 5 pages, 2 figures. Accepted for publication in MNRAS Letter
How a pilot looks at altitude
Commerical pilot eye scanning data previously collected were reanalyzed to evaluate how pilot used the drum pointer altimeter. The results of these tests showed that the pilots seldom used the drum window apparently because it was difficult to read as indicated by average drum window dwell times of .6 seconds. It is suggested that pilot scanning data be collected for other type of altimeters in order to find those with good scanning characteristics
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