16,863 research outputs found
Detachable caster adapter
Detachable caster adapter moves heavy welding tables when fork lift trucks are not practical. A support saddle on the adapter, connected to the caster platform by means of a hinge, fits the leg of the welding table, but can be modified to fit other leg configurations
Using the Fundamental Plane to Estimate the Total Binding Mass in A2626
We use fundamental plane (FP) distance estimates to the components of the
double cluster A2626 (cz~17,500 km/s) to constrain cluster kinematics and
estimate total binding mass. The FP coefficients for a sample of 24 early type
and S0 cluster members (alpha=1.30+/-0.36 and beta=0.31+/-0.06) are consistent
with others reported in the literature. We examine the Mg_b distributions
within both subclusters and find them to be indistinguishable. Lacking evidence
for stellar population differences, we interpret the FP zeropoint offset
(\log(D_B/D_A)=-0.037+/-0.046, where D_{cl} is distance to subcluster cl) as a
measure of the distance difference. This measurement is consistent with the
subclusters being at the same distance, and it rules out the Hubble flow
hypothesis (distances proportional to velocity) with 99% confidence; analysis
of the subcluster galaxy magnitude distributions rules out Hubble flow at 93%
confidence. Both results favor a kinematic model where the subclusters are
bound and infalling. We estimate the total cluster binding mass by modelling
the subcluster merger as radial infall. The minimum possible total binding mass
is 1.65 times higher than the sum of the standard virial masses, a difference
statistically significant at the ~3sigma level. We discuss explanations for the
inconsistency including (1) biases in the standard virial mass estimator, (2)
biases in our radial infall mass estimate, and (3) mass beyond the virialized
cluster region; if the standard virial mass is significantly in error, the
cluster has an unusually high mass to light ratio (~1000h). Because
observational signatures of departures from radial infall are absent, we
explore the implications of mass beyond the virialized, core regions.
(abridged)Comment: 14 pages and 5 figures, Latex, Accepted for publication in A
Optical Turbulence Measurements and Models for Mount John University Observatory
Site measurements were collected at Mount John University Observatory in 2005
and 2007 using a purpose-built scintillation detection and ranging system.
profiling indicates a weak layer located at 12 - 14 km above sea
level and strong low altitude turbulence extending up to 5 km. During calm
weather conditions, an additional layer was detected at 6 - 8 km above sea
level. profiling suggests that tropopause layer velocities are nominally
12 - 30 m/s, and near-ground velocities range between 2 -- 20 m/s, dependent on
weather. Little seasonal variation was detected in either and
profiles. The average coherence length, , was found to be cm for
the full profile at a wavelength of 589 nm. The average isoplanatic angle,
, was arcsec. The mean turbulence altitude,
, was found to be km above sea level. No average in the
Greenwood frequency, , could be established due to the gaps present in the
\vw\s profiles obtained. A modified Hufnagel-Valley model was developed to
describe the profiles at Mount John, which estimates at 6 cm
and at 0.9 arcsec. A series of models were developed, based
on the Greenwood wind model with an additional peak located at low altitudes.
Using the model and the suggested model for moderate ground
wind speeds, is estimated at 79 Hz.Comment: 14 pages; accepted for publication in PAS
Calculation of Hydrogenic Bethe Logarithms for Rydberg States
We describe the calculation of hydrogenic (one-loop) Bethe logarithms for all
states with principal quantum numbers n <= 200. While, in principle, the
calculation of the Bethe logarithm is a rather easy computational problem
involving only the nonrelativistic (Schroedinger) theory of the hydrogen atom,
certain calculational difficulties affect highly excited states, and in
particular states for which the principal quantum number is much larger than
the orbital angular momentum quantum number. Two evaluation methods are
contrasted. One of these is based on the calculation of the principal value of
a specific integral over a virtual photon energy. The other method relies
directly on the spectral representation of the Schroedinger-Coulomb propagator.
Selected numerical results are presented. The full set of values is available
at quant-ph/0504002.Comment: 10 pages, RevTe
- …