10,378 research outputs found
Heat sterilizable Ni-Cd battery development Quarterly report, 1 Apr. - 30 Jun. 1968
Development of heat sterilizable, hermetically sealed nickel cadmium batteries for space application
Relativistic semiclassical approach in strong-field nonlinear photoionization
Nonlinear relativistic ionization phenomena induced by a strong laser
radiation with elliptically polarization are considered. The starting point is
the classical relativistic action for a free electron moving in the
electromagnetic field created by a strong laser beam. The application of the
relativistic action to the classical barrier-suppression ionization is briefly
discussed. Further the relativistic version of the Landau-Dykhne formula is
employed to consider the semiclassical sub-barrier ionization. Simple
analytical expressions have been found for: (i) the rates of the strong-field
nonlinear ionization including relativistic initial and final state effects;
(ii) the most probable value of the components of the photoelectron final state
momentum; (iii) the most probable direction of photoelectron emission and (iv)
the distribution of the photoelectron momentum near its maximum value.Comment: 13 pages, 3 figures, to be published in Phys. Rev.
Heat sterilizable and impact resistant Ni-Cd battery development Quarterly report, 1 Apr. - 30 Jun. 1969
Electrochemistry, battery engineering, and impact tests of heat sterilizable nickel cadmium cell
Audit of surgical delay in relationship to outcome after proximal femoral fracture.
To ascertain the influence of surgical delay on outcome after proximal femoral fracture in elderly females, a cohort study of patients presenting in 1987 was compared to 1989/90. Organisational changes in the intervening period were introduced to reduce delay to surgical intervention. Two hundred and eighty females aged 65 years and over presenting from the local catchment area of an acute inner-city teaching hospital were enrolled in the study. Seventy-nine patients received surgery in 1987 and 186 in 1989/90. The one year mortality was 34% and 26% respectively. The proportion receiving surgery within 24 hours rose from 34% in 1987 to 57% in 1989/90. The relative hazard of the group receiving surgery on day 2 in comparison to day 1 was 1.7 (95% CI 1.0 to 2.9) when adjusted for co-variance of age and mental score. Medically fit elderly patients presenting with proximal femoral fracture have improved survival with early surgery within 24 hours of admission. Improvements in the organisation of hospital care will result in important benefits for the increasing number of elderly females presenting with proximal femoral fracture
Cloud Structure and Physical Conditions in Star-forming Regions from Optical Observations. I. Data and Component Structure
We present high-resolution optical spectra (at ~0.6--1.8 km s-1) of
interstellar CN, CH, CH^+, \ion{Ca}{1}, \ion{K}{1}, and \ion{Ca}{2} absorption
toward 29 lines of sight in three star-forming regions, \rho Oph, Cep OB2, and
Cep OB3. The observations and data reduction are described. The agreement
between earlier measurements of the total equivalent widths and our results is
quite good. However, our higher resolution spectra reveal complex structure and
closely blended components in most lines of sight. The velocity component
structure of each species is obtained by analyzing the spectra of the six
species for a given sight line together. The tabulated column densities and
Doppler parameters of individual components are determined by using the method
of profile fitting. Total column densities along lines of sight are computed by
summing results from profile fitting for individual components and are compared
with column densities from the apparent optical depth method. A more detailed
analysis of these data and their implications will be presented in a companion
paper.Comment: 66 pages, 15 figures, accepted to ApJ
Radio Polarization of the Young High-Magnetic-Field Pulsar PSR J1119-6127
We have investigated the radio polarization properties of PSR J1119-6127, a
recently discovered young radio pulsar with a large magnetic field. Using
pulsar-gated radio imaging data taken at a center frequency of 2496 MHz with
the Australia Telescope Compact Array, we have determined a rotation measure
for the pulsar of +842 +/- 23 rad m^-2. These data, combined with archival
polarimetry data taken at a center frequency of 1366 MHz with the Parkes
telescope, were used to determine the polarization characteristics of PSR
J1119-6127 at both frequencies. The pulsar has a fractional linear polarization
of ~75% and ~55% at 1366 and 2496 MHz, respectively, and the profile consists
of a single, wide component. This pulse morphology and high degree of linear
polarization are in agreement with previously noticed trends for young pulsars
(e.g., PSR J1513-5908). A rotating-vector (RV) model fit of the position angle
(PA) of linear polarization over pulse phase using the Parkes data suggests
that the radio emission comes from the leading edge of a conal beam. We discuss
PSR J1119-6127 in the context of a recent theoretical model of pulsar spin-down
which can in principle be tested with polarization and timing data from this
pulsar. Geometric constraints from the RV fit are currently insufficient to
test this model with statistical significance, but additional data may allow
such a test in the future.Comment: 9 pages, including 6 figures and 1 table. Accepted for publication in
Ap
Relativistic photoelectron spectra in the ionization of atoms by elliptically polarized light
Relativistic tunnel ionization of atoms by intense, elliptically polarized
light is considered. The relativistic version of the Landau-Dykhne formula is
employed. The general analytical expression is obtained for the relativistic
photoelectron spectra. The most probable angle of electron emission, the
angular distribution near this angle, the position of the maximum and the width
of the energy spectrum are calculated. In the weak field limit we obtain the
familiar non-relativistic results. For the case of circular polarization our
analytical results are in agreement with recent derivations of Krainov [V.P.
Krainov, J. Phys. B, {\bf 32}, 1607 (1999)].Comment: 8 pages, 2 figures, accepted for publication in Journal of Physics
A Comparison of Measured Crab and Vela Glitch Healing Parameters with Predictions of Neutron Star Models
There are currently two well-accepted models that explain how pulsars exhibit
glitches, sudden changes in their regular rotational spin-down. According to
the starquake model, the glitch healing parameter, Q, which is measurable in
some cases from pulsar timing, should be equal to the ratio of the moment of
inertia of the superfluid core of a neutron star (NS) to its total moment of
inertia. Measured values of the healing parameter from pulsar glitches can
therefore be used in combination with realistic NS structure models as one test
of the feasibility of the starquake model as a glitch mechanism. We have
constructed NS models using seven representative equations of state of
superdense matter to test whether starquakes can account for glitches observed
in the Crab and Vela pulsars, for which the most extensive and accurate glitch
data are available. We also present a compilation of all measured values of Q
for Crab and Vela glitches to date which have been separately published in the
literature. We have computed the fractional core moment of inertia for stellar
models covering a range of NS masses and find that for stable NSs in the
realistic mass range 1.4 +/- 0.2 solar masses, the fraction is greater than
0.55 in all cases. This range is not consistent with the observational
restriction Q < 0.2 for Vela if starquakes are the cause of its glitches. This
confirms results of previous studies of the Vela pulsar which have suggested
that starquakes are not a feasible mechanism for Vela glitches. The much larger
values of Q observed for Crab glitches (Q > 0.7) are consistent with the
starquake model predictions and support previous conclusions that starquakes
can be the cause of Crab glitches.Comment: 8 pages, including 3 figures and 1 table. Accepted for publication in
Ap
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