Mechanisms of temporal variation in single-nephron blood flow in rats

1993 ◽  
Vol 264 (3) ◽  
pp. F427-F434 ◽  
Author(s):  
K. P. Yip ◽  
N. H. Holstein-Rathlou ◽  
D. J. Marsh
Keyword(s):  
Blood Flow ◽  
High Frequency ◽  
Laser Doppler Velocimetry ◽  
Low Frequency ◽  
Tubuloglomerular Feedback ◽  
High Frequency Oscillation ◽  
Frequency Oscillation ◽  
Acute Hypertension ◽  
Efferent Arteriole ◽  
Single Nephron

Modified laser-Doppler velocimetry was used to determine the number of different mechanisms regulating single-nephron blood flow. Two oscillations were identified in star vessel blood flow, one at 20-50 mHz and another at 100-200 mHz. Tubuloglomerular feedback (TGF) mediates the slower oscillation, and the faster one is probably myogenic in origin. Acute hypertension increased autospectral power in the 20-50 mHz and 100-200 mHz frequency bands to 282 +/- 50 and 248 +/- 64%, respectively, of control even though mean single-nephron blood flow was autoregulated. Mean blood flow increased 24.6 +/- 6.1% when TGF was inhibited by intratubular perfusion with furosemide, and it decreased 42.8 +/- 3.9% when TGF was saturated by tubular perfusion with artificial tubular fluid at high rates. Autospectral power in the low-frequency band decreased 50.5 +/- 9.6% during furosemide and decreased 74.9 +/- 5.9% during TGF saturation, consistent with a TGF origin of the slow oscillation. In contrast, autospectral power of the high-frequency oscillation increased 75.4 +/- 23.9% during TGF inhibition and decreased 35.8 +/- 11% when TGF was saturated, suggesting interactions between the two spontaneously oscillating components in efferent arteriole blood flow.

Analysis of Fast-Scale Bifurcation in Peak Current Controlled Buck-Boost Inverter Based on Unified Averaged Model

2016 ◽  
Vol 26 (05) ◽  
pp. 1650074 ◽  
Author(s):  
Hao Zhang ◽  
Shuai Dong ◽  
Weimin Guan ◽  
Ye Liu
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Period Doubling ◽  
Current Control ◽  
High Frequency Oscillation ◽  
Switching Frequency ◽  
Unified Framework ◽  
Frequency Oscillation ◽  
Peak Current ◽  
Averaged Model

In this paper, a unified averaged modeling method is proposed to investigate the fast-scale period-doubling bifurcation of a full-bridge integrated buck-boost inverter with peak current control. In order to increase the resolution of the conventional classic averaged model to half the switching frequency, sample-and-hold effect of inductor current is absorbed into the averaged model, i.e. the proposed unified averaged model can capture the high-frequency dynamical characteristics of the buck-boost inverter, which is both an extension and a modification of conventional averaged model. Based on the unified mode, fast-scale bifurcation is identified, and the corresponding bifurcation point is predicted with the help of the locus movement of all the poles, and their underlying mechanisms are revealed. Detailed analysis shows that the occurrence of high-frequency oscillation means fast-scale bifurcation, while the occurrence of low-frequency oscillation leads to slow-scale bifurcation. Finally, it is demonstrated that the unified averaged model can provide not only a general method to investigate both the slow- and fast-scale bifurcations in a unified framework but also a quite straightforward design-oriented method which can be directly applicable.

Ventilation with external high frequency oscillation around a negative baseline increases pulmonary blood flow after the Fontan operation

1992 ◽  
Vol 2 (3) ◽  
pp. 277-280 ◽  
Author(s):  
Daniel J. Penny ◽  
Zamir Hayek ◽  
Peter Rawle ◽  
Michael L. Rigby ◽  
Andrew N. Redington
Keyword(s):  
Blood Flow ◽  
Negative Pressure ◽  
High Frequency ◽  
Pulmonary Blood Flow ◽  
Positive Pressure Ventilation ◽  
Fontan Operation ◽  
Intermittent Positive Pressure Ventilation ◽  
High Frequency Oscillation ◽  
Positive Pressure ◽  
Frequency Oscillation

AbstractIn this prospective study, pulmonary blood flow was measured using transesophageal Doppler echocardiography to assess whether ventilation by means of external high frequency oscillation around a negative pressure baseline can increase pulmonary blood flow, compared to intermittent positive pressure ventilation, in five patients after the Fontan operation. Pulmonary blood flow was measured when patients were ventilated by means of intermittent positive pressure ventilation and again during equivalent negative pressure ventilation using the external oscillatory technique. When compared to that with intermittent positive pressure ventilation, ventilation using external high frequency oscillation increased pulmonary blood flow by 116 ±61.5% (p=0.013). These results show that ventilation using an external oscillatory device with a mean negative chamber pressure may provide hemodynamic advantages in patients requiring assisted ventilation after the Fontan operation.

scholarly journals LIVER BLOOD FLOW DURING HIGH FREQUENCY OSCILLATION AND CONVENTIONAL MECHANICAL VENTILATION

1984 ◽  
Vol 61 (3) ◽  
pp. A27-A27 ◽  
Author(s):  
Colin F. Mackenzie ◽  
Harold G. Roberts ◽  
Junzo Takeda ◽  
Brian H. Hoff ◽  
Gerald S. Johnston ◽  
...  
Keyword(s):  
Mechanical Ventilation ◽  
Blood Flow ◽  
High Frequency ◽  
Liver Blood Flow ◽  
Conventional Mechanical Ventilation ◽  
High Frequency Oscillation ◽  
Frequency Oscillation

scholarly journals The Effects of Negative Pressure External High Frequency Oscillation on Cerebral Blood Flow and Cardiac Output of the Monkey

1987 ◽  
Vol 21 (2) ◽  
pp. 166-169 ◽  
Author(s):  
Keith J Barrington ◽  
C Anthony Ryan ◽  
Abraham Peliowsk ◽  
Michael Nosko ◽  
Neil N Finer
Keyword(s):  
Blood Flow ◽  
Cardiac Output ◽  
Cerebral Blood Flow ◽  
Negative Pressure ◽  
High Frequency ◽  
High Frequency Oscillation ◽  
Frequency Oscillation

scholarly journals Multitaper Estimates of Phase-Amplitude Coupling

2021 ◽  
Author(s):  
Kyle Q. Lepage ◽  
Cavan N. Fleming ◽  
Mark Witcher ◽  
Sujith Vijayan
Keyword(s):  
High Frequency ◽  
Broad Band ◽  
Low Frequency ◽  
Partial Coherence ◽  
High Frequency Oscillation ◽  
Frequency Oscillation ◽  
Low Frequency Oscillation ◽  
Statistical Measures ◽  
Frequency Components ◽  
Phase Amplitude

AbstractPhase-amplitude coupling (PAC) is the association of the amplitude of a high-frequency oscillation with the phase of a low-frequency oscillation. In neuroscience, this relationship provides a mechanism by which neural activity might be coordinated between distant regions. The dangers and pitfalls of assessing phase-amplitude coupling with existing statistical measures have been well-documented. The limitations of these measures include: (i) response to non-oscillatory, high-frequency, broad-band activity, (ii) response to high-frequency components of the low-frequency oscillation, (iii) adhoc selection of analysis frequency-intervals, and (iv) reliance upon data shuffling to assess statistical significance. In this work, a multitaper phase-amplitude coupling estimator is proposed that addresses issues (i)-(iv) above. Specifically, issue (i) is addressed by replacing the analytic signal envelope estimator computed using the Hilbert transform with a multitaper estimator that down-weights non-sinusoidal activity using a classical, multitaper super-resolution technique. Issue (ii) is addressed by replacing coherence between the low-frequency and high-frequency components in a standard PAC estimator with multitaper partial coherence, while issue (iii) is addressed with a physical argument regarding meaningful neural oscillation. Finally, asymptotic statistical assessment of the multitaper estimator is introduced to address issue (iv).

High-Frequency Oscillation and Chronic Lung Disease in Very Low Birth Weight Infants

PEDIATRICS ◽  
2001 ◽  
Vol 108 (1) ◽  
pp. 212-214
Author(s):  
J. P. Shenai; ◽  
P. Rimensberger; ◽  
U. Thome ◽  
F. Pohlandt; ◽  
P. Rimensberger
Keyword(s):  
Birth Weight ◽  
Low Birth Weight ◽  
Lung Disease ◽  
Chronic Lung Disease ◽  
High Frequency ◽  
Very Low Birth Weight ◽  
High Frequency Oscillation ◽  
Frequency Oscillation ◽  
Low Birth Weight Infants
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