THE DISTRIBUTION OF IONIZATION ALONG UNDERDENSE METEOR TRAILS

1964 ◽  
Vol 42 (11) ◽  
pp. 2035-2047 ◽  
Author(s):  
D. W. Rice ◽  
P. A. Forsyth
Keyword(s):  
Upper Atmosphere ◽  
Sources Of Error ◽  
Signal Characteristics ◽  
Radio Signals ◽  
Meteor Trails

Attempts to use the decay of radio signals reflected from individual meteor trails to study the upper atmosphere have revealed a puzzling inconsistency in the signal behavior. An earlier paper pointed out that this inconsistency remained even when the previously postulated sources of error were eliminated. As a result, an irregularly ionized trail model was proposed and shown, by calculation of signal characteristics, to be capable of accounting for the observations. This paper presents results of a new experiment which permitted the determination of the ionization profiles as the meteor trails were formed. The predicted irregularities were found, even for trails which exhibited apparently "ideal" underdense signal characteristics.

scholarly journals Hydrogen Maser Support of VLBI for the NASA Crustal Dynamics Project

1988 ◽  
Vol 129 ◽  
pp. 505-506
Author(s):  
R. E. Price ◽  
M. J. Chandler ◽  
B. R. Schupler ◽  
P. R. Dachel
Keyword(s):  
Hydrogen Maser ◽  
Frequency Reference ◽  
Frequency Standards ◽  
The Pacific ◽  
Mobile Stations ◽  
Radio Signals ◽  
Crustal Dynamics ◽  
Stable Frequency ◽  
The Difference

For the NASA Crustal Dynamics Project VLBI network, signals from quasars are recorded simultaneously at widely separated antennas. It is well known that hydrogen maser frequency standards provide the stable frequency reference used to precisely measure the difference in arrival time of the radio signals at the different antennas, enabling the determination of precise distances between the antennas. This paper reviews the practical requirements for maser support of VLBI for the Crustal Dynamics Project and describes the means used to meet these requirements for a network of eight fixed and three mobile stations which participate in approximately 200 VLBI experiments per year at locations in North America and the Pacific.

Instrumental and Procedural Sources of Error in Determination of Bile Pigments in Amniotic Fluid

1972 ◽  
Vol 18 (2) ◽  
pp. 150-154 ◽  
Author(s):  
Robert W Burnett
Keyword(s):  
Amniotic Fluid ◽  
Error Propagation ◽  
Obstet Gynecol ◽  
Bile Pigments ◽  
Linear Estimation ◽  
Sources Of Error ◽  
Significant Bias ◽  
Accuracy And Precision ◽  
Baseline Estimation

Abstract Although the Liley spectrophotometric estimation of bile pigments in amniotic fluid [Amer. J. Obstet. Gynecol. 82, 1359 ( 1961)] is widely used, the levels of accuracy and precision necessary for clinically meaningful results have not been clarified. This paper delineates some of the important instrumental and procedural sources of error, and how each affects the final value of ΔA455: (a) A limit of error propagation is presented to show that the uncertainty in ΔA455 due to instrumental factors is considerably larger than is commonly appreciated. (b) It is desirable to use a logarithmic baseline estimation, as did Liley, instead of a linear estimation, which can introduce a serious bias. (c) Failure to establish a true zero-absorbance baseline before scanning the specimen can also result in a significant bias in the calculated ΔA455.

Sign in / Sign up

Export Citation Format

Share Document