365 research outputs found
Ultra stable frequency distribution system
A system is presented for synchronizing a signal at a remotely located slave station with the phase and frequency of a signal generated at a master station. The signal transmitted at the master station and received by the slave station provides compensation for the phase shift caused by the transmission path delays between the master and slave station. The slave station transmits a signal to the master station at a frequency that is different from the frequency of the signal being transmitted by the master station. The signal transmitted by the slave station is received by the master station while the master station transmitter is off. The signal transmitted by the master station is received by the slave station while the slave station transmitter is off
Aspects of the population geography of the eastern border counties of Scotland, 1850-1967
This thesis seeks to study the population of the south east
Scotland counties of Berwick, Roxburgh and Selkirk from 1851 to the
present day, and to establish the significance of the interrelationship between changing demographic structure on the one
hand and employment and social provision on the other.The major characteristic of the population of the area is that
it has declined throughout the period, and by considering the various
possible components of population change, fertility, mortality and
migration, it was clearly established that the last named was
instrumental in producing this feature. The volume of net migration
was computed, an idea of the gross amount of movement involved
obtained from various sources, and the origins and destinations of
movers was determined. From this part of the study it was evident
that:1) migration was a characteristic of both burghal and landward
areas2) net migration is only a small proportion of the gross
movement3) destinations of out-migrants were mainly Central
Scotland and north-east England: origins of in-migrants were mainly rural, particularly from south-
west Scotland.4) migration is age selective: the proportion of persons
aged 15-25 who undertook migration movements was at
least twice as high as the proportion among people of
all other age groups together, in each ten-year period
from 1851.5) out-migration is female dominated in the 15-20 age group
out-migration is male dominated in the 20-25 age groupCorrelation of demographic trends with changing employment
conditions, particularly in the main industries of the area was then
made, and a close relationship between economic changes and population changes was established. Case studies of twelve parishes in
the area were undertaken and by studying population, economic and
social changes in these small units over the 1851-196? period, it
was possible to find out whether population change caused economic
change or vice versa. A sample survey of the population in each
parish was made, to obtain information on movement both of those
in the parish, and of close relatives who may have left, and by so
doing to ascertain the main reasons for living in the area, and moving to or from it at the present time
Active Tectonics of the Northeastern Mojave Desert, California.
This study has led to an improved understanding of the active tectonics and seismic hazards of the northeastern Mojave Desert region and has provided a means with which to assess regional strain models proposed by previous workers. Primary data sets include published and unpublished geologic maps, Landsat Thematic Mapper multi-spectral imagery, SPOT panchromatic imagery as well as hand-held ground and aerial photographs (panchromatic, color and color-infrared), color video, digital topography, gravity, seismicity and paleomagnetic data. Prior to analysis, data sets were organized into a geographic information system implemented on a UNIX workstation. This allowed for the simultaneous visualization of combinations of data sets in order to gain new perspectives on spatial and temporal relationships. Most faults of the northeastern Mojave Desert region have moved in late Quaternary time with many currently active and seismogenic. The most prominent zone of seismicity is along the Goldstone Lake fault zone. It is proposed that the net right slip across the Goldstone Lake fault zone is 10 km. This amount of displacement represents 18% of the total right-shear, 57 km, likely to have occurred across the northeastern Mojave Desert since 6-10 Ma. Paleomagnetism studies confirm that there has been little to no regional vertical-axis rotation of the Goldstone Lake region since 22 Ma. This result constrains the northern limit of early Miocene, regional crustal rotations which formed as a consequence of right shear along the Trans Mojave-Sierran shear zone. Furthermore, geometric/kinematic models of the late Cenozoic tectonic evolution of the northeastern Mojave Desert which require regional vertical-axis rotations of this region are refuted by this result. The Goldstone Lake fault zone is likely more significant than previously recognized; the location, orientation, length and seismicity of the Goldstone Lake fault zone give cause to conclude that it may be capable of producing earthquakes similar in magnitude to that of the Landers earthquake (M = 7.3, June 28, 1992)
Recommended from our members
Symbolic thinking :: extending the dual representation issue beyond the model/room paradigm.
Thesis (M.S.
Crack detection in a rotating shaft using artificial neural networks and PSD characterisation
Peer reviewedPostprin
Carbon stars in the IRTS survey
We have identified 139 cool carbon stars in the near-infrared
spectro-photometric survey of the InfraRed Telescope in Space (IRTS) from the
conspicuous presence of molecular absorption bands at 1.8, 3.1 and 3.8 microns.
Among them 14 are new, bright (K ~ 4.0-7.0), carbon stars. We find a trend
relating the 3.1 microns band strength to the K-L' color index, which is known
to correlate with mass-loss rate. This could be an effect of a relation between
the depth of the 3.1 microns feature and the degree of development of the
extended stellar atmosphere where dust starts to form.Comment: accepted by the PASP; December 7, 200
Drum Major\u27s Song : March Song
https://digitalcommons.library.umaine.edu/mmb-vp/4598/thumbnail.jp
A Spitzer view of protoplanetary disks in the gamma Velorum cluster
We present new Spitzer Space Telescope observations of stars in the young ~5
Myr gamma Velorum stellar cluster. Combining optical and 2MASS photometry, we
have selected 579 stars as candidate members of the cluster. With the addition
of the Spitzer mid-infrared data, we have identified 5 debris disks around
A-type stars, and 5-6 debris disks around solar-type stars, indicating that the
strong radiation field in the cluster does not completely suppress the
production of planetesimals in the disks of cluster members. However, we find
some evidence that the frequency of circumstellar primordial disks is lower,
and the IR flux excesses are smaller than for disks around stellar populations
with similar ages. This could be evidence for a relatively fast dissipation of
circumstellar dust by the strong radiation field from the highest mass star(s)
in the cluster. Another possibility is that gamma Velorum stellar cluster is
slightly older than reported ages and the the low frequency of primordial disks
reflects the fast disk dissipation observed at ~5 Myr.Comment: Accepted for publication in the Astrophysical Journal: 32 pages; 11
Figure
Radio interferometric observations of candidate water-maser-emitting planetary nebulae
We present Very Large Array (VLA) observations of H2O and OH masers, as well
as radio continuum emission at 1.3 and 18 cm toward three sources previously
cataloged as planetary nebulae (PNe) and in which single-dish detections of H2O
masers have been reported: IRAS 17443-2949, IRAS 17580-3111, and IRAS
18061-2505. Our goal was to unambiguously confirm their nature as
water-maser-emitting PNe, a class of objects of which only two bona-fide
members were previously known. We detected and mapped H2O maser emission toward
all three sources, while OH maser emission is detected in IRAS 17443-2949 and
IRAS 17580-3111 as well as in other two objects within the observed fields:
IRAS 17442-2942 (unknown nature) and IRAS 17579-3121 (also cataloged as a
possible PN). We found radio continuum emission associated only with IRAS
18061-2505. Our results confirm IRAS 18061-2505 as the third known case of a PN
associated with H2O maser emission. The three known water-maser-emitting PNe
have clear bipolar morphologies, which suggests that water maser emission in
these objects is related to non-spherical mass-loss episodes. We speculate that
these bipolar PNe would have ``water-fountain'' Asymptotic Giant Branch (AGB)
and post-AGB stars as their precursors. A note of caution is given for other
objects that have been classified as OHPNe (objects with both OH maser and
radio continuum emission, that could be extremely young PNe) based on
single-dish observations, since interferometric data of both OH masers and
continuum are necessary for a proper identification as members of this class.Comment: 33 pages, 10 figures. Accepted by The Astronomical Journa
- …