A Seismic Investigation of the Crust and Moho on a Line Perpendicular to the Grenville Front

1971 ◽  
Vol 8 (12) ◽  
pp. 1553-1583 ◽  
Author(s):  
R. F. Mereu ◽  
G. Jobidon
Keyword(s):  
Upper Mantle ◽  
Low Frequency ◽  
Mean Velocity ◽  
Crust And Upper Mantle ◽  
Grenville Province ◽  
Long Line ◽  
The Mean ◽  
Oriented Parallel ◽  
The University ◽  
Lateral Variations

A major structural feature 50 to 75 km in width has been outlined along the Moho in an area just south of the Grenville Front from a delay-time analysis of Pn waves arriving from a number of different azimuths. The crust in this anomalous region was found to be from 5–10 km thicker than in the surrounding area. The low frequency portion of the gravity low in central Quebec can be attributed to this feature. The fact that the front is deep-seated suggests that it may mark the position of an ancient fault connected tectonically in origin to the mid-continent gravity high and Lake Superior syncline.During the summer of 1968, the University of Western Ontario participated with the Dominion Observatory of Canada and other research groups in a crustal survey of eastern Quebec. Shots of various sizes were fired by the Dominion Observatory at six different locations in central Quebec. Two of the locations were in the Superior (structural) Province, two in the Grenville (structural) Province, and two in the vicinity of the Grenville Front. The University of Western Ontario recording stations were located at distances from 60 to 800 km southwest of the shots and lay along (a) a 550-km long line running perpendicular to the Grenville Front from Lake Evans in the Superior Province to a point just south of Lake St. John in the Grenville Province, (b) a 100-km long line running parallel to the Grenville Front from Chibougamau to the northeastern end of Lake Mistassini. Six portable seismic recorders (two of them 3-component) were moved every day. A total of 45 locations were occupied, with observations being made in a fan-like manner.The apparent crust and upper mantle velocities as determined by a least squares analysis of all the data are 6.43 ±.03 km/s (43 observations) and 8.15 ±.03 km/s (70 observations) respectively. From an analysis involving combined seismic and gravitational observations along with synthetic seismograms, the following structure emerges. The mean velocity of the upper crust is 6.31 km/s, but because of the lateral variations in its structure the true velocity varies from 6.1 to 6.6 km/s, the higher values occurring just south of the Grenville Front. No clear evidence for layering could be found throughout the crust, but both seismic and gravitational observations indicated that the mean velocity of the lower portion of the crust was 6.55 km/s with this value increasing to at least 7 km/s just above the Moho. The apparent velocities of smaller regional samples of Pn observations varied erratically as a result of topography on the Moho. However values obtained from arrays oriented parallel to the Grenville Front were significantly higher, indicating that the upper mantle may be behaving in an anisotropic manner.

Azimuth and slowness anomalies of seismic waves measured on the central California seismographic array. Part I. Observations

1966 ◽  
Vol 56 (1) ◽  
pp. 223-239 ◽  
Author(s):  
Michio Otsuka
Keyword(s):  
Upper Mantle ◽  
Measurement Errors ◽  
Seismic Waves ◽  
Crust And Upper Mantle ◽  
Arrival Times ◽  
Central California ◽  
The North ◽  
Upper Mantle Structure ◽  
Coast Ranges ◽  
The University

abstract Arrays of seismographs are usually considered to be detectors which give enhanced signals from distant earthquakes. They also provide, however, a new way of learning more about the structure of the crust and upper mantle. The deviation of the seismic-wave surface from its expected configuration may be regarded as a consequence of non-homogeneous and anisotropic conditions in the earth. The operations of the University of California network of telemetry stations in the Coast Ranges of California provides an opportunity to discover the practicality of this approach. The situation of this network near the continental margin gives the study particular interest. The differences in arrival-times between array elements of coherent peaks or troughs of P and pP phases from 28 teleseisms in the period of 1963-1964 were read from the telemetry records of the central California seismographic array. The direction of approach and velocities of the wave fronts were then determined and compared with the great circle azimuths and with the apparent velocities calculated from the Jeffreys-Bullen tables. The observed anomalies in direction of approach and apparent velocites are found to be cyclic functions of the direction of the source. The amplitudes of these functions are almost 10 degrees in azimuth anomaly and 1.0 sec/deg in slowness anomaly. Error analyses show that the anomaly functions cannot be attributed to the measurement errors. The derived anomaly functions provide a powerful means of examining crustal and upper mantle structure under the array and perhaps at the source. Variations between subsets of the array indicate significant differences in structure between portions of the Coast Ranges to the north and to the south of Hollister.

Heat Transfer From an Oscillating Horizontal Wire to Water

1962 ◽  
Vol 84 (3) ◽  
pp. 251-254 ◽  
Author(s):  
F. K. Deaver ◽  
W. R. Penney ◽  
T. B. Jefferson
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Reynolds Number ◽  
Mixed Convection ◽  
Low Frequency ◽  
Mean Velocity ◽  
Transfer Rates ◽  
Low Frequency Oscillations ◽  
The Mean ◽  
Horizontal Wire

An investigation has been made to determine the effect of low frequency oscillations of relatively large amplitude on the rate of heat transfer from a small horizontal wire to water. Frequencies from 0 to 4.25 cps and amplitudes to 2.76 in. were employed. Temperature differences up to 140 deg F provided heat flux from 2000 to 300,000 Btu/hr ft2. A Reynolds number was defined based on the mean velocity of the wire, and it was shown that heat-transfer rates may be predicted by either forced, free, or mixed convection correlations depending on the relative magnitudes of Reynolds and Grashof numbers.

The mean velocity profile of turbulent boundary layers with system rotation

2000 ◽  
Vol 408 ◽  
pp. 323-345 ◽  
Author(s):  
T. B. NICKELS ◽  
P. N. JOUBERT
Keyword(s):  
Velocity Profile ◽  
Boundary Layers ◽  
Turbulent Boundary Layers ◽  
Secondary Flows ◽  
Pressure Gradients ◽  
Mean Velocity ◽  
System Rotation ◽  
Linear Correction ◽  
The Mean ◽  
The University

This paper examines changes in the mean velocity profiles of turbulent boundary layers subjected to system rotation. Analysis of the data from several studies conducted in the large rotating wind tunnel at the University of Melbourne shows the existence of a universal linear correction to the velocity profile in the logarithmic region. The appropriate parameters relevant to rotation are derived and correlations are found between the parameters. Flows with adverse pressure gradients, zero pressure gradients and secondary flows are examined and all appear to exhibit the universal linear correction, suggesting that it is robust.

Behavior of Separation Bubble and Reattached Boundary Layer Around a Circular Leading Edge

1994 ◽  
Author(s):  
B. K. Hazarika ◽  
C. Hirsch
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Separation Bubble ◽  
Low Frequency ◽  
Leading Edge ◽  
Reynolds Numbers ◽  
Mean Velocity ◽  
Low Frequency Oscillations ◽  
Lower Reynolds Number ◽  
The Mean

The flow around a circular leading edge airfoil is investigated in an incompressible, low turbulence freestream. Hot-wire measurements are performed through the separation bubble, the reattachment and the recovery region till development of the fully turbulent boundary layer. The results of the experiments in the range of Reynolds numbers 1.7×103 to 11.8×103 are analysed and presented in this paper. A separation bubble is present near the leading edge at all Reynolds numbers. At the lowest Reynolds number investigated, the transition is preceded by strong low frequency oscillations. The correlation given by Mayle for prediction of transition of short separation bubbles is successful at the lower Reynolds number cases. The length of the separation bubble reduces considerably with increasing Reynolds number in the range investigated. The turbulence in the reattached flow persists even when the Reynolds number based on momentum thickness of the reattached boundary layer is small. The recovery length of the reattached layer is relatively short and the mean velocity profile follows logarithmic law within a short distance downstream of the reattachment point and the friction coefficient conforms to Prandtl-Schlichting skin-friction formula for a smooth flat plate at zero incidence.

The structure of the crust and upper mantle under the highest ranges of the Canadian Rockies from a seismic refraction survey

1977 ◽  
Vol 14 (2) ◽  
pp. 196-208 ◽  
Author(s):  
R. F. Mereu ◽  
S. C. Majumdar ◽  
R. E. White
Keyword(s):  
Upper Mantle ◽  
Seismic Waves ◽  
Seismic Refraction ◽  
Rocky Mountain ◽  
P Wave ◽  
Crust And Upper Mantle ◽  
Seismic Experiment ◽  
Mantle Layer ◽  
Seismic Refraction Survey ◽  
The University

In the Project Edzoe seismic experiment, the seismic waves from a series of shots fired in Greenbush Lake near Revelstoke B.C. were recorded by the University of Western Ontario at approximately 100 stations along two seismic lines. The first began in the Rocky Mountain Trench, crossed the mountains near Jasper, Alberta and then extended NE across the Plains to Fort McMurray, Alberta, the maximum distance from the shotpoint being 800 km. The second line was roughly in line with the shotpoint and extended from Stanley Falls to Whitecourt, Alberta.An interpretation of the results revealed that the topography of the Moho under the highest ranges of the Rocky Mountains is relatively flat when compared with results from similar experiments on the Canadian Shield. In addition to the typical Pn layer, a very high velocity upper mantle layer (8.5 to 8.8 km/s) also exists at a depth of 60 km or approximately 10 km below the Moho. An interesting feature observed on the record sections was the echelon pattern formed by the crustal P wave trains. From a study of theoretical amplitudes it was found that this pattern could be explained by the presence of large positive gradients within the lower crust coupled with a relatively low value of Q near the Moho.

scholarly journals VI. Experiments upon the heart of the dog with reference to the maximum volume of blood sent out by the left ventricle in a single beat and the influence of variations in venous pressure, arterial pressure, and pulse-rate upon the work done by the heart

1884 ◽  
Vol 175 ◽  
pp. 139-160 ◽  
Keyword(s):  
Venous Pressure ◽  
Uncertain Data ◽  
Mean Velocity ◽  
Long Time ◽  
Cause Of Failure ◽  
The Mean ◽  
The Right ◽  
The University ◽  
Short Time ◽  
Work Done

The most important factor to be determined before calculating the work done by the heart is the quantity of blood forced from the ventricles at each systole. Most of the efforts to determine this quantity have been based either upon faulty observations upon the dead heart, or upon the uncertain data obtained by estimating the mean velocity of the stream of blood in the aorta. Professor Martin accordingly suggested to us that we should attempt to measure it directly on the isolated Dog’s heart. The work thus undertaken was carried on during the greater part of the university session, 1881-82, and the results obtained are given in the following pages. The method of isolating the heart was essentially that described in Professor Martin’s paper (Phil. Trans., 1883, p. 663). In the course of this work many unexpected difficulties arose, necessitating changes in the apparatus and the method of operating, and preventing us for a long time from obtaining any successful results. In our experiments it was necessary not only that the heart should live and beat, but that it should be in the best possible physiological condition, and any marked pulmonary œdema made an experiment nearly valueless. This most frequent cause of failure was mainly owing to the fact that, on account of the large quantity of blood required for an experiment, we were obliged to use Calf’s blood obtained from the butcher; very often this blood, as Professor Martin states in his paper, will bring about œdema of the lungs in a short time; large quantities of exuded serum pour out of the tracheal cannula, the air-passages in the lungs become choked up with liquid, and the circulation from the right to the left side of the heart is greatly impeded. We have succeeded, however, in making a considerable number of experiments in which all the conditions were favourable, the œdema of the lungs not occurring to any marked extent until after many observations had been made.

Effect of Surgical Versus Pharmacological Decompression of Ludwig’s Angina on Airway Compromise among Nigerian Patients

2020 ◽  
Author(s):  
Ekaniyere EB
Keyword(s):  
Length Of Hospital Stay ◽  
Surgical Decompression ◽  
Airway Compromise ◽  
Inclusion Criteria ◽  
Hospital Stays ◽  
Ludwig’S Angina ◽  
The Mean ◽  
The University ◽  
Ludwig's Angina ◽  
Gender Type

Background: Even though the decompression of the cellulitis phase of Ludwig’s angina (LA) by surgical or pharmacological approach is well documented, it is unclear which approach is more effective. Objective: We aim to compare the outcome of treatment between surgical versus pharmacological decompression in patients with LA. Subjects and Methods: A retrospective cohort study was designed. Data were collected from the case notes of patients that met the inclusion criteria from 2004 to 2018 at the University of Benin Teaching Hospital, Nigeria.The data were age, gender, type of decompression approach, length of hospital stay (LOS) and airway compromise. Result: A total of 62 patients comprising 37(59.7%) surgical decompression group and 25(40.3%) pharmacological decompression group were studied. Thirty-six (58.1%) males and 26 (41.9%) females were studied. Their mean age and standard deviation were 40.6 years and 11.9 years respectively. The mean length of hospital stays between the pharmacological and surgical decompression groups were 8.05 days and 13.8 days respectively. The incidence of airway compromise in the surgical decompression group was 19.9% lower than that of the pharmacological decompression group (P=0.47), which was not significant. The type of decompression approach also failed to influence the incidence of airway compromise (P = 0.41). Conclusion: The use of surgical versus pharmacological decompression does not significantly alter the incidence of airway compromise in the management of LA. The Patients that had surgical decompression had a shorter stay in the hospital as compared to those who had pharmacological decompression. This was not statistically significant.

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