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 $\sim$10 km. This amount of displacement represents $\sim$18% of the total right-shear, $\sim$57 km, likely to have occurred across the northeastern Mojave Desert since $\sim$6-10 Ma. Paleomagnetism studies confirm that there has been little to no regional vertical-axis rotation of the Goldstone Lake region since $\sim$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)

Symbolic thinking :: extending the dual representation issue beyond the model/room paradigm.

Thesis (M.S.

A Study of Certain Symbiotic Nitrogen-Fixing Systems

Abstract Not Provided

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