12. Laboratory Investigation of P-Wave Amplitude Anisotropy in Limestone

2001 ◽  
pp. 187-204
Author(s):  
Brad A. Bessinger ◽  
Roberto Suárez-Rivera ◽  
Kurt T. Nihei ◽  
L. Brun Hilbert ◽  
Larry R. Myer ◽  
...  
Keyword(s):  
Laboratory Investigation ◽  
Wave Amplitude ◽  
P Wave ◽  
Amplitude Anisotropy

scholarly journals Simulation of the effect of stress-induced anisotropy on borehole compressional wave propagation

Geophysics ◽  
2014 ◽  
Vol 79 (4) ◽  
pp. D205-D216 ◽  
Author(s):  
Xinding Fang ◽  
Michael C. Fehler ◽  
Arthur Cheng
Keyword(s):  
Wave Propagation ◽  
Stress Concentration ◽  
Elastic Properties ◽  
Wave Velocity ◽  
Wave Amplitude ◽  
P Wave ◽  
Azimuthal Variation ◽  
P Wave Velocity ◽  
Velocity Region

Formation elastic properties near a borehole may be altered from their original state due to the stress concentration around the borehole. This can lead to an incorrect estimation of formation elastic properties measured from sonic logs. Previous work has focused on estimating the elastic properties of the formation surrounding a borehole under anisotropic stress loading. We studied the effect of borehole stress concentration on sonic logging in a moderately consolidated Berea sandstone using a two-step approach. First, we used an iterative approach, which combines a rock-physics model and a finite-element method, to calculate the stress-dependent elastic properties of the rock around a borehole subjected to an anisotropic stress loading. Second, we used the anisotropic elastic model obtained from the first step and a finite-difference method to simulate the acoustic response of the borehole. Although we neglected the effects of rock failure and stress-induced crack opening, our modeling results provided important insights into the characteristics of borehole P-wave propagation when anisotropic in situ stresses are present. Our simulation results were consistent with the published laboratory measurements, which indicate that azimuthal variation of the P-wave velocity around a borehole subjected to uniaxial loading is not a simple cosine function. However, on field scale, the azimuthal variation in P-wave velocity might not be apparent at conventional logging frequencies. We found that the low-velocity region along the wellbore acts as an acoustic focusing zone that substantially enhances the P-wave amplitude, whereas the high-velocity region caused by the stress concentration near the borehole results in a significantly reduced P-wave amplitude. This results in strong azimuthal variation of P-wave amplitude, which may be used to infer the in situ stress state.

scholarly journals ECG Measurements to Emphasize Atrial Potentials Using Modified Limb Lead System

2018 ◽  
Vol 7 (3.12) ◽  
pp. 632
Author(s):  
Manikandan K ◽  
Mohanasundaram K
Keyword(s):  
Electrical Activity ◽  
Wave Amplitude ◽  
P Wave ◽  
Electrode Placement ◽  
Atrial Arrhythmias ◽  
Lead System ◽  
Wave Duration ◽  
Normal Limits ◽  
P Wave Duration ◽  
Female Subjects

With the advancement in the field of Electrocardiology (ECG), the acquisition of electrical activity of the heart plays an important role in the diagnosis of various cardiovascular diseases. In general, this activity of conduction is acquired using Standard 12 Lead ECG system. Recently, a Modified Limb Lead system has been developed to study the atrial electrical activity for the diagnosis of atrial arrhythmias. The present study is to derive the normal limits of female subjects using Modified Limb Lead (MLL) system. This study was evaluated in 59 female subjects 19.52 ± 1 (Mean ± S.D) and is primarily involved to study atrial potentials with the use of precordial and modified limb lead position. In sinus rhythm female subjects, the P wave amplitude was 33.06 ± 21.18 µV and the Ta wave amplitude was 20.72 ± 18.16 µV. The P wave duration was 94.22 ± 10.64 ms, the Ta wave duration was 85.51 ± 17.49 ms. The results show that modifications in the limb electrode placement have significant effect on amplitudes and PR segment which may be of great importance for the assessment of atrial potentials.  

scholarly journals Cardiorespiratory and electrocardiographic effects of methadone or morphine in the perioperative period in anesthetized dogs with continuous rate infusion of propofol and submitted to ovariohysterectomy

2017 ◽  
Vol 38 (1) ◽  
pp. 209 ◽  
Author(s):  
Priscila Pavini Cintra ◽  
Celina Tie Nishimori Duque ◽  
Mariana Póvoa Silveira ◽  
Maria Augusta Adami Pereira dos Santos ◽  
Mariana Miranda Vaz da Silva ◽  
...  
Keyword(s):  
Postoperative Analgesia ◽  
Wave Amplitude ◽  
Clinical Importance ◽  
Cardiovascular Effects ◽  
Random Order ◽  
Perioperative Period ◽  
Assisted Ventilation ◽  
P Wave ◽  
Rescue Analgesia ◽  
Rate Infusion

The aims of this study were compare the electrocardiogram (ECG) and cardiopulmonary effects of methadone or morphine, both injected intravenously (IV) in dogs anesthetized with continuous infusion of propofol. Sixteen healthy female mongrel dogs were used in this study for elective ovariohysterectomy. The animals were allocated in random order into two groups assigned GME (methadone 0.3 mg kg-1, IV) or GMO (morphine 0.3 mg kg-1, IV). Parameters were evaluated: heart rate (HR), P-wave amplitude (Ps and PmV), interval between Ps and R waves (PR), QRS duration (QRS), R-wave amplitude (R), duration the interval between the Q and T waves (QT), systolic blood pressure (SBP), rectal temperature (RT), respiratory rate (RR), end tidal of carbon dioxide (ETCO2) and periferic oxyhemoglobin saturation (SpO2). Postoperative analgesia was assessed by mechanical nociceptive stimulus based on the scale proposed by Firth and Haldane (1999) and rescue analgesia based on the visual analogue scale. HR was lower in GME in relation to GMO. The P, PmV, PR, QRS, R and QT values remained within their normality tracks, showing no clinical importance. Apnea and ETCO2 increased in both groups. There was no difference between groups of the analgesic effects. It can be concluded that methadone and morphine promote similar cardiovascular effects after IV injection during surgery in dogs anesthetized with propofol by continuous rate infusion, however, when methadone used, assisted ventilation is required. In addition, both drugs promote postoperative analgesia until six hours.

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