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1
Lagrange, Andre H. "Valproate Enhances Neuropeptide Y Expression: Modulating the Modulators." Epilepsy Currents 7, no. 4 (July 2007): 107–9. http://dx.doi.org/10.1111/j.1535-7511.2007.00167.x.
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Chronic Valproic Acid Treatment Triggers Increased Neuropeptide Y Expression and Signaling in Rat Nucleus Reticularis Thalami. Brill J, Lee M, Zhao S, Fernald RD, Huguenard JR. J Neurosci 2006;26:6813–6822. Valproate (VPA) can suppress absence and other seizures, but its precise mechanisms of action are not completely understood. We investigated whether VPA influences the expression of neuropeptide Y (NPY), an endogenous anticonvulsant. Chronic VPA administration to young rats (300–600 mg · kg–1 · d–1 in divided doses over 4 d) resulted in a 30–50% increase in NPY mRNA and protein expression in the nucleus reticularis thalami (nRt) and hippocampus, but not in the neocortex, as shown by real-time PCR, radioimmunoassay, and immunohistochemistry. No increased expression was observed after a single acute dose of VPA. Chronic treatment with the pharmacologically inactive VPA analog octanoic acid did not elicit changes in NPY expression. No significant expression changes could be shown for the mRNAs of the Y1 receptor or of the neuropeptides somatostatin, vasoactive intestinal polypeptide, and choleocystokinin. Fewer synchronous spontaneous epileptiform oscillations were recorded in thalamic slices from VPA-treated animals, and oscillation duration as well as the period of spontaneous and evoked oscillations were decreased. Application of the Y1 receptor inhibitor N2-(diphenylacetyl)- N-[(4-hydroxyphenyl)methyl]-d-arginine-amide (BIBP3226) enhanced thalamic oscillations, indicating that NPY is released during those oscillations and acts to downregulate oscillatory strength. Chronic VPA treatment significantly potentiated the effect of BIBP3226 on oscillation duration but not on oscillation period. These results demonstrate a novel mechanism for the antiepileptic actions of chronic VPA therapy.
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Chen, C. K., L. Wang, J. T. Yang, and L. T. Chen. "Experimental and Computational Analysis of Periodic Flow Structure in Oscillatory Gas Flow Meters." Journal of Mechanics 22, no. 2 (June 2006): 137–44. http://dx.doi.org/10.1017/s1727719100004433.
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AbstractThe oscillatory characteristics and dynamic structure of periodic flow in an oscillatory gas flow meter were studied experimentally and numerically. The flow oscillations were triggered by the Coanda effect and an universal correlation between Strouhal number and Reynolds number, Str = 1.09 × 10−3 for ReHD >800, was deduced based on spectral analysis of the pressure fluctuations in the flow channel. Numerical simulation indicated that the evolution of the flow patterns was classified into stages of induction and sustainable periodic oscillation. The transformation between the two stages was noticeably affected by the design of the feedback channels. The results further revealed that the development of the main vortex in the oscillating chamber and the small vortices at the entrance of the feedback channels concurrently modulate the mechanism of oscillation. The small vortices located at both entrances of the feedback channels play the role of a pair of modulating valves, which alternatively switch on and off the bypass flow through each feedback channel, thus reinforcing the periodic oscillation.
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Chen, Hua-Pin, San-Fu wang, Yu-Nan Chen, and Qi-Geng Huang. "Electronically Tunable Third-Order Quadrature Oscillator Using VDTAs." Journal of Circuits, Systems and Computers 28, no. 04 (March 31, 2019): 1950066. http://dx.doi.org/10.1142/s021812661950066x.
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This study proposes a new electronically tunable third-order quadrature oscillator using two multi-output voltage difference transconductance amplifiers (VDTAs) and three grounded capacitors. The proposed circuit provides three quadrature voltage outputs, two high-impedance quadrature current outputs, and one high-impedance current output with controllable amplitude. The proposed circuit can provide amplitude modulation/amplitude shift keying signals when the input bias current of the second VDTA is a modulating signal. The oscillation condition and oscillation frequency can be separately adjusted by the input bias currents of two multi-output VDTAs, and it is suitable for use on custom sensor networks. Experimental and H-Spice simulation results are given to confirm theoretical analyses.
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Marsh, Donald J., Olga V. Sosnovtseva, Alexey N. Pavlov, Kay-Pong Yip, and Niels-Henrik Holstein-Rathlou. "Frequency encoding in renal blood flow regulation." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 288, no. 5 (May 2005): R1160—R1167. http://dx.doi.org/10.1152/ajpregu.00540.2004.
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With a model of renal blood flow regulation, we examined consequences of tubuloglomerular feedback (TGF) coupling to the myogenic mechanism via voltage-gated Ca channels. The model reproduces the characteristic oscillations of the two mechanisms and predicts frequency and amplitude modulation of the myogenic oscillation by TGF. Analysis by wavelet transforms of single-nephron blood flow confirms that both amplitude and frequency of the myogenic oscillation are modulated by TGF. We developed a double-wavelet transform technique to estimate modulation frequency. Median value of the ratio of modulation frequency to TGF frequency in measurements from 10 rats was 0.95 for amplitude modulation and 0.97 for frequency modulation, a result consistent with TGF as the modulating signal. The simulation predicted that the modulation was regular, while the experimental data showed much greater variability from one TGF cycle to the next. We used a blood pressure signal recorded by telemetry from a conscious rat as the input to the model. Blood pressure fluctuations induced variability in the modulation records similar to those found in the nephron blood flow results. Frequency and amplitude modulation can provide robust communication between TGF and the myogenic mechanism.
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Cho, Jun-Hyung, Hyo-Sang Jeong, and Hyuk-Kee Sung. "Spurious Tone Reduction and Signal Stabilization of Optoelectronic Oscillators by Low-Frequency RF Signal Modulation." Photonics 9, no. 5 (May 12, 2022): 339. http://dx.doi.org/10.3390/photonics9050339.
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In this study, the oscillation signal stabilization and spurious tone suppression of a directly modulated optoelectronic oscillator (DM-OEO) are simultaneously achieved by modulating a laser with a low-frequency radio frequency (RF) signal. The laser in the DM-OEO is modulated by a rectangular wave with a period inversely proportional to the frequency interval of the spurious tones and a duty cycle of 50%. The optical sidebands of the rectangular wave-modulated laser pulled the optical gain of the spurious tones of the DM-OEO, resulting in a spurious tone suppression and time stabilization in the DM-OEO signal. We achieve a 15 GHz DM-OEO with a 40.14 dB side-mode suppression ratio (SMSR) and 2.55 dB improvement in the oscillation power stability compared to that without RF modulation.
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WANG, Xinlin, Xiaoyue QIU, Xuchu WENG, and Ping YANG. "Modulating working memory related-oscillation via entrainment of neural oscillation." Advances in Psychological Science 30, no. 4 (2022): 802. http://dx.doi.org/10.3724/sp.j.1042.2022.00802.
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Sihn, Duho, and Sung-Phil Kim. "Differential modulation of behavior by infraslow activities of different brain regions." PeerJ 10 (February 1, 2022): e12875. http://dx.doi.org/10.7717/peerj.12875.
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The oscillation phase of electroencephalograms (EEGs) is associated with behavioral performance. Several studies have demonstrated this association for relatively fast oscillations (>1 Hz); a similar finding has also been reported for slower oscillations, showing that behavioral performance is correlated with the phase of infraslow activity (ISA, 0.01–0.1 Hz) of electroencephalography (EEG). However, the previous study only investigated ISA in a local brain region using a relatively simple task (somatosensory discrimination task), leaving it difficult to determine how the EEG ISA for various brain regions is associated with behavioral performance. In addition, it is not known whether the EEG ISA phase modulates more complex behavioral task performance. In the present study, we analyzed the ISA of whole-brain EEG of participants performing various behaviors while playing video games. We found that behavior was associated with the specific oscillation phase of EEG ISA when that behavior was independent of other behaviors. In addition, we found that the EEG ISA oscillation phases modulating the different behaviors varied across brain regions. Our results suggest that the EEG ISA for different brain regions modulates behavioral performance in different ways and such modulation of EEG ISA can be generalized to diverse behaviors. This study may deepen the understanding of how EEG ISA modulates behavior and increases the applicability of EEG ISA.
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Kim, MinKyung, and UnCheol Lee. "Alpha oscillation, criticality, and responsiveness in complex brain networks." Network Neuroscience 4, no. 1 (January 2020): 155–73. http://dx.doi.org/10.1162/netn_a_00113.
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Brains in unconsciousness are characterized by significantly limited responsiveness to stimuli. Even during conscious wakefulness, responsiveness is highly dependent on ongoing brain activity, specifically, of alpha oscillations (∼10 Hz). We hypothesized that the variety of brain responses to external stimuli result from the interaction between state-specific and transient alpha oscillations and stimuli. To justify this hypothesis, we simulated various alpha oscillations in the human brain network, modulating criticality (a balanced state between order and disorder), and investigated specific alpha oscillation properties (instantaneous amplitude, phase, and global synchronization) that induce a large or small response. As a result, we found that the alpha oscillations near a critical state show a more complex and long-lasting response, which is more prominent when stimuli are given to globally desynchronized and low-amplitude oscillations. We also found specific phases of alpha oscillation that barely respond to stimuli, which implies the presence of temporal windows in the alpha cycle for a large or small response. The results explain why brain responses are so variable across conscious and unconscious states and across time windows even during conscious wakefulness, and emphasize the importance of considering ongoing alpha oscillations for effective brain stimulation.
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Kozhevnikov, Vasily, Andrey Kozyrev, Vladimir Konev, and Aleksey Klimov. "The phase stability of nanosecond Gunn oscillators." Vojnotehnicki glasnik 70, no. 2 (2022): 461–74. http://dx.doi.org/10.5937/vojtehg70-36094.
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Introduction/purpose: Detailed theoretical and experimental studies have been carried out in order to investigate the problem of a phase stability in electrodynamically uncoupled Gunn oscillators. Methods: The influence of modulating pulse instabilities has been investigated by means of computer simulation in the framework of a nonlinear one-dimensional theoretical model of the GaAs Gunn diode semiconductor active region. Experimental observations were also conducted including microwave measurements and antenna far-field estimation. They confirm the main theoretical results and extend the key work conclusions. Results: It was shown that the initial phase of the microwave oscillation out of the Gunn oscillator is independent of internal noises of the semiconductor structure and can be fixed only by the modulating voltage pulse. Conclusion: Gunn-diodes based microwave oscillators were stabilized using the leading edge of the voltage pulse from the modulating power supply. These results open up serious prospects for designing antenna phased arrays based on Gunn oscillators without mutual feedback (electrodynamically independent).
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Restrepo, Juan Camilo, Aldemar Higgins, Jaime Escobar, Silvio Ospino, and Natalia Hoyos. "Contribution of low-frequency climatic–oceanic oscillations to streamflow variability in small, coastal rivers of the Sierra Nevada de Santa Marta (Colombia)." Hydrology and Earth System Sciences 23, no. 5 (May 16, 2019): 2379–400. http://dx.doi.org/10.5194/hess-23-2379-2019.
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Abstract. This study evaluated the influence of low-frequency oscillations, that are linked to large-scale oceanographic–atmospheric processes, on streamflow variability in small tropical coastal mountain rivers of the Sierra Nevada de Santa Marta, Colombia. We used data from six rivers that had > 32 years of complete, continuous monthly streamflow records. This investigation employed spectral analyses to (1) explore temporal characteristics of streamflow variability, (2) estimate the net contribution to the energy spectrum of low-frequency oscillations to streamflow anomalies, and (3) analyze the linkages between streamflow anomalies and large-scale, low-frequency oceanographic–atmospheric processes. Wavelet analyses indicate that the 8–12-year component exhibited a quasi-stationary state, with a peak of maximum power between 1985 and 2005. These oscillations were nearly in phase in all rivers. Maximum power peaks occurred for the Palomino and Rancheria rivers in 1985 and 1995, respectively. The wavelet spectrum highlights a change in river variability patterns between 1995 and 2015, characterized by a shift towards the low-frequency oscillations' domain (8–12 years). The net contribution of these oscillations to the energy spectrum was as high as 51 %, a value much larger than previously thought for rivers in northwestern South America. The simultaneous occurrence of hydrologic oscillations, as well as the increase in the amplitude of the 8–12-year band, defined periods of extremely anomalous wet seasons during 1989–1990, 1998–2002 and 2010–2011, reflecting the role of low-frequency oscillations in modulating streamflow variability in these rivers. Cross-wavelet transform and wavelet coherence revealed high common powers and significant coherences in low-frequency bands (>96 months) between streamflow anomalies and Atlantic Meridional Oscillation (AMO), Pacific Decadal Oscillation (PDO) and the Tropical North Atlantic Index (TNA). These results show the role of large-scale, low-frequency oceanographic–climate processes in modulating the long-term hydrological variability of these rivers.
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Silber, I., C. G. Price, and C. J. Rodger. "Semi-annual oscillation (SAO) of the nighttime ionospheric D-region as detected through ground-based VLF receivers." Atmospheric Chemistry and Physics Discussions 15, no. 21 (November 4, 2015): 30383–407. http://dx.doi.org/10.5194/acpd-15-30383-2015.
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Abstract. Earth's middle and upper atmosphere exhibits several dominant large scale oscillations in many measured parameters. One of these oscillations is the semi-annual oscillation (SAO). The SAO can be detected in the ionospheric total electron content (TEC), the ionospheric transition height, the wind regime in the mesosphere-lower-thermosphere (MLT), and in the MLT temperatures. In addition, as we report for the first time in this study, the SAO is among the most dominant oscillations in nighttime very low frequencies (VLF) narrow-band subionospheric measurements. As VLF signals are reflected off the ionospheric D-region (at altitudes of ~65 and ~85 km, during the day and night, respectively), this implies that the upper part of the D-region is experiencing this oscillation as well, through changes in the dominating electron or ion densities, or by changes in the electron collision frequency, recombination rates, and attachment rates, all of which could be driven by oscillatory MLT temperature changes. We conclude that the main source of the SAO in the nighttime D-region is due to NOx molecules transport from the lower levels of the thermosphere, resulting in enhanced ionization and the creation of free electrons in the nighttime D-region, thus modulating the SAO signature in VLF NB measurements. While the cause for the observed SAO is still a subject of debate, this oscillation should be taken into account when modeling the D-region in general and VLF wave propagation in particular.
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Silber, Israel, Colin Price, and Craig J. Rodger. "Semi-annual oscillation (SAO) of the nighttime ionospheric D region as detected through ground-based VLF receivers." Atmospheric Chemistry and Physics 16, no. 5 (March 14, 2016): 3279–88. http://dx.doi.org/10.5194/acp-16-3279-2016.
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Abstract. Earth's middle and upper atmosphere exhibits several dominant large-scale oscillations in many measured parameters. One of these oscillations is the semi-annual oscillation (SAO). The SAO can be detected in the ionospheric total electron content (TEC), the ionospheric transition height, the wind regime in the mesosphere–lower thermosphere (MLT), and in the MLT temperatures. In addition, as we report for the first time in this study, the SAO is among the most dominant oscillations in nighttime very low frequency (VLF) narrowband (NB) subionospheric measurements. As VLF signals are reflected off the ionospheric D region (at altitudes of ∼ 65 and ∼ 85 km, during the day and night, respectively), this implies that the upper part of the D region is experiencing this oscillation as well, through changes in the dominating electron or ion densities, or by changes in the electron collision frequency, recombination rates, and attachment rates, all of which could be driven by oscillatory MLT temperature changes. We conclude that the main source of the SAO in the nighttime D region is NOx molecule transport from the lower levels of the thermosphere, resulting in enhanced ionization and the creation of free electrons in the nighttime D region, thus modulating the SAO signature in VLF NB measurements. While the cause for the observed SAO is still a subject of debate, this oscillation should be taken into account when modeling the D region in general and VLF wave propagation in particular.
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Singh, Madhu, and R. Bhatla. "Role of Madden–Julian Oscillation in Modulating Monsoon Retreat." Pure and Applied Geophysics 175, no. 6 (January 30, 2018): 2341–50. http://dx.doi.org/10.1007/s00024-018-1788-y.
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Melendez-Alvarez, Juan, Changhan He, Rong Zhang, Yang Kuang, and Xiao-Jun Tian. "Emergent Damped Oscillation Induced by Nutrient-Modulating Growth Feedback." ACS Synthetic Biology 10, no. 5 (April 29, 2021): 1227–36. http://dx.doi.org/10.1021/acssynbio.1c00041.
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Westra, Seth, Benjamin Renard, and Mark Thyer. "The ENSO–Precipitation Teleconnection and Its Modulation by the Interdecadal Pacific Oscillation." Journal of Climate 28, no. 12 (June 11, 2015): 4753–73. http://dx.doi.org/10.1175/jcli-d-14-00722.1.
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Abstract This study evaluates the role of the interdecadal Pacific oscillation (IPO) in modulating the El Niño–Southern Oscillation (ENSO)–precipitation relationship. The standard IPO index is described together with several alternatives that were derived using a low-frequency ENSO filter, demonstrating that an equivalent IPO index can be obtained as a low-frequency version of ENSO. Several statistical artifacts that arise from using a combination of raw and smoothed ENSO indices in modeling the ENSO–precipitation teleconnection are then described. These artifacts include the potentially spurious identification of low-frequency variability in a response variable resulting from the use of smoothed predictors and the potentially spurious modulation of a predictor–response relationship by the low-frequency version of the predictor under model misspecification. The role of the IPO index in modulating the ENSO–precipitation relationship is evaluated using a global gridded precipitation dataset, based on three alternative statistical models: stratified, linear, and piecewise linear. In general, the information brought by the IPO index, beyond that already contained in the Niño-3.4 index, is limited and not statistically significant. An exception is in northeastern Australia using annual precipitation data, and only for the linear model. Stratification by the IPO index induces a nonlinear ENSO–precipitation relationship, suggesting that the apparent modulation by the IPO is likely to be spurious and attributable to the combination of sample stratification and model misspecification. Caution is therefore required when using smoothed climate indices to model or explain low-frequency variability in precipitation.
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Li, Xuewei, Xidong Wang, Peter C. Chu, and Dongliang Zhao. "Low-Frequency Variability of the Yellow Sea Cold Water Mass Identified from the China Coastal Waters and Adjacent Seas Reanalysis." Advances in Meteorology 2015 (2015): 1–14. http://dx.doi.org/10.1155/2015/269859.
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This study uses the China Coastal Waters and Adjacent Seas Reanalysis (CORA) data to investigate the interannual and decadal variability of the Yellow Sea cold water mass (YSCWM) and its relationship to climate indices including the Arctic Oscillation (AO), El Niño/Southern Oscillation (ENSO), and Pacific Decadal Oscillation (PDO). On the interannual timescale, the strong correlation between winter PDO and the YSCWM may indicate the dominant effect of winter PDO on the YSCWM through the modulation of local heat flux and wind stress. It is also found that the local wind stress and heat flux in summer have little impact on the interannual variability of the YSCWM. On the decadal time scale, the YSCWM is associated with winter AO and winter PDO. Winter AO mainly controls local heat flux, modulating the decadal variability of the YSCWM. In contrast, winter PDO is strongly connected with winter heat flux and wind stress to modulate the decadal variability of the YSCWM. In summer, for three climate factors, ENSO is the dominant factor controlling the decadal variability of the YSCWM.
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Krause, Matthew R., Pedro G. Vieira, Jean-Philippe Thivierge, and Christopher C. Pack. "Brain stimulation competes with ongoing oscillations for control of spike timing in the primate brain." PLOS Biology 20, no. 5 (May 25, 2022): e3001650. http://dx.doi.org/10.1371/journal.pbio.3001650.
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Transcranial alternating current stimulation (tACS) is a popular method for modulating brain activity noninvasively. In particular, tACS is often used as a targeted intervention that enhances a neural oscillation at a specific frequency to affect a particular behavior. However, these interventions often yield highly variable results. Here, we provide a potential explanation for this variability: tACS competes with the brain’s ongoing oscillations. Using neural recordings from alert nonhuman primates, we find that when neural firing is independent of ongoing brain oscillations, tACS readily entrains spiking activity, but when neurons are strongly entrained to ongoing oscillations, tACS often causes a decrease in entrainment instead. Consequently, tACS can yield categorically different results on neural activity, even when the stimulation protocol is fixed. Mathematical analysis suggests that this competition is likely to occur under many experimental conditions. Attempting to impose an external rhythm on the brain may therefore often yield precisely the opposite effect.
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Kirpichnikova, I. M., and A. Yu Sologubov. "Multivariable Control of Solar Battery Power by Extremum Seeking: Starting from Linear Analysis." Machines 7, no. 4 (October 4, 2019): 64. http://dx.doi.org/10.3390/machines7040064.
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In this study, we tried to combine maximum power point trackers (MPPT) and «Extremum Seeking» in a single multi-parameter extremum seekeng system for orienting solar panels and draw attention to the problem of a deeper study of nonlinear adaptive control using appropriate methods for their analysis. MPPT controller becomes one of the extremum seeking loops, and as a result, the maximum power is achieved not only by searching for the optimal voltage value, but also due to the optimal angular position of the solar panel in Euclidean space, because the photocurrent depends on the angle of inclination of the Sun’s rays to the surface. The task of tuning extremum seeking loops becomes more analytically difficult, which is associated with nonlinear and multiply connected properties. This requires starting the solution from a simpler “linear” level. We applied the approach associated with the passage of modulating oscillations with a given frequency and amplitude through an open-loop system. This approach, which is generalized in this work at least for extremum seeking of the solar panels power, should be used for approximate calculations if there are no strict requirements for convergence and energy loss for the search. Research design is as follows: parametric identification of the current-voltage and volt-watt curves; obtaining the transfer function by the semi-automated sparse matrix method; reducing the order of the transfer function of coordinate electric drives by introducing a scaling factor. To the most important theoretical result, we attribute the property of the generalized amplitude of the solar panel power oscillations with multi-parameter control to be a combination of input modulating oscillations superimposed on the signals of the control integrators. Having revealed the relationship of their properties, it becomes possible to eliminate non-linearity from the system and operate only with the analytical relationship of the input modulating oscillations and the generalized oscillation of the controlled parameter. We attribute the prediction of the effect to one of the most interesting physical results, in which, for the same amplitude of modulating oscillations, the amplitudes of the photocurrent oscillations and the power of the solar panel at different angular positions will be generally different.
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Chen, Shangfeng, Wen Chen, Renguang Wu, and Linye Song. "Impacts of the Atlantic Multidecadal Oscillation on the Relationship of the Spring Arctic Oscillation and the Following East Asian Summer Monsoon." Journal of Climate 33, no. 15 (August 1, 2020): 6651–72. http://dx.doi.org/10.1175/jcli-d-19-0978.1.
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AbstractPrevious studies indicated that spring Arctic Oscillation (AO) can influence the following East Asian summer monsoon (EASM). This study reveals that the Atlantic multidecadal oscillation (AMO) has a pronounced modulation of the spring AO–EASM connection. Spring AO has a close relation with the EASM during the negative AMO (−AMO) phase. However, during the positive AMO (+AMO) phase, the spring AO–EASM connection is weak. During the −AMO phase, a marked dipole atmospheric anomaly pattern (with an anticyclonic anomaly over the midlatitudes and a cyclonic anomaly over the subtropics) and a pronounced tripole sea surface temperature (SST) anomaly pattern is formed in the North Pacific during positive spring AO years. The cyclonic anomaly, SST, and precipitation anomalies over the subtropical western North Pacific (WNP) maintain and propagate southwestward in the following summer via a positive air–sea feedback, which further impacts the EASM variation. During the +AMO phase, the Pacific center of the spring AO (i.e., the anticyclonic anomaly over the midlatitudes) is weak. As such, the cyclonic anomaly cannot be induced over the subtropical WNP by the spring AO via wave–mean flow interaction. Hence, the spring AO–EASM connection disappears during the +AMO phase. The AMO impacts the Pacific center of the spring AO via modulating the Aleutian low intensity and North Pacific storm track intensity. The observed AMO modulation of the spring AO–EASM connection and Pacific center of the spring AO can be captured by the long historical simulation in a coupled global climate model.
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Wang, Tianning, Yuhong Zou, Ning Huang, Junlin Teng, and Jianguo Chen. "CCDC84 Acetylation Oscillation Regulates Centrosome Duplication by Modulating HsSAS-6 Degradation." Cell Reports 29, no. 7 (November 2019): 2078–91. http://dx.doi.org/10.1016/j.celrep.2019.10.028.
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Sattinger, Stanley S., Yedidia Neumeier, Aharon Nabi, Ben T. Zinn, David J. Amos, and Douglas D. Darling. "Sub-Scale Demonstration of the Active Feedback Control of Gas-Turbine Combustion Instabilities." Journal of Engineering for Gas Turbines and Power 122, no. 2 (January 3, 2000): 262–68. http://dx.doi.org/10.1115/1.483204.
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Described are sub-scale tests that successfully demonstrate active feedback control as a means of suppressing damaging combustion oscillations in natural-gas-fueled, lean-premix combustors. The control approach is to damp the oscillations by suitably modulating an auxiliary flow of fuel injected near the flame. The control system incorporates state observer software that can ascertain the frequency, amplitude, and phase of the dominant modes of combustion oscillation, and a sub-scale fuel flow modulator that responds to frequencies well above 1 kHz. The demonstration was conducted on a test combustor that could sustain acoustically coupled combustion instabilities at preheat and pressurization conditions approaching those of gas-turbine engine operation. With the control system inactive, two separate instabilities occurred with combined amplitudes of pressure oscillations exceeding 70 kPa (10 psi). The active control system produced four-fold overall reduction in these amplitudes. With the exception of an explainable control response limitation at one frequency, this reduction represented a major milestone in the implementation of active control. [S0742-4795(00)00702-X]
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Ivasić, Sara, Ivana Herceg-Bulić, and Martin P. King. "Recent weakening in the winter ENSO teleconnection over the North Atlantic-European region." Climate Dynamics 57, no. 7-8 (May 4, 2021): 1953–72. http://dx.doi.org/10.1007/s00382-021-05783-z.
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AbstractNew observational evidence for variability of the atmospheric response to wintertime El Niño-Southern Oscillation (ENSO) is found. Using different approaches and datasets, a weakening in the recent ENSO teleconnection over the North Atlantic-European (NAE) region is demonstrated. Changes in both pattern and strength of the teleconnection indicate a turning point in the 1970s with a shift from a response resembling the North Atlantic Oscillation (NAO) to an anomaly pattern orthogonal to NAO with very weak or statistically non-significant values; and to nearly non-existent teleconnection in the most recent decades. Results shows the importance of the background sea surface temperature (SST) state and sea-ice climatology having opposite effects in modulating the ENSO-NAE teleconnection. As indicated with targeted simulations, the recent change in the SST climatology in the Atlantic and Arctic has contributed to the weakening of the ENSO effect. The findings of this study can have implications on our understanding of modulations of ENSO teleconnections and ENSO as a source of predictability in the NAE sector.
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Trutnev, G. A., K. K. Perevozchikov, and S. B. Nazarov. "Sensing System and Methods for Measuring Oscillations in the Resonator of a Hemispherical Resonator Gyroscope." Herald of the Bauman Moscow State Technical University. Series Instrument Engineering, no. 1 (130) (February 2020): 50–63. http://dx.doi.org/10.18698/0236-3933-2020-1-50-63.
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The paper considers a hemispherical resonator gyroscope and methods for combining eight capacitive displacement sensors into a measuring instrument. We propose a circuit diagram for a measuring instrument based on operational amplifiers. The diagram makes it possible to implement oscillation measurement for direct and alternating resonator voltages as well as a combined scenario. We derived a mathematical model simulating the output signal of the measuring instrument. We analysed the sensitivity of our system for different implementations of the measuring instrument. For the case when the modulating signal frequency and resonator oscillation frequency are multiples of each other, we derived expressions to find the angular wave position and offset signals for the control system. We used the linear term of the signal model to derive these equations, provided estimations of the errors occurring and guidelines on reducing them. We also investigated the case when the frequencies of the modulating and modulated signals are not multiples. We consider a general approach to evaluating wave pattern parameters, taking the emerging errors into account
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Afonin, A., and I. Vikhrova. "Structural analysis of seasonal dynamics of daily growth of annual shoots of woolly-stemmed willow." Bulletin of Science and Practice 5, no. 3 (March 15, 2019): 11–21. http://dx.doi.org/10.33619/2414-2948/40/01.
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Given the complex characteristics of woolly–stemmed willow. The necessity of studying the regularities of seasonal dynamics of daily growth of annual shoots is substantiated. The study used material from the model inbred-clone population. Empirical data were processed using structural–harmonic analysis methods. It was found that the seasonal dynamics of the daily growth of shoots is cyclic quasi–periodic. Empirical series of dynamics at the highest level of significance are approximated by sums of elementary harmonics with a period of oscillation of 9.2 to 92.0 days. Revealed high-amplitude harmonic with the oscillation period of 23.0 to 92.0 day and low amplitude with a period of oscillation of 9.2 to 18.4 days. On all the studied shoots only the fourth harmonics coincide with the oscillation period of 23.0 days. The main contribution to the seasonal dynamics of shoot growth is made by three high-amplitude harmonics, which form two main signals with oscillation periods of 23 and 36 days. Other harmonics have a modulating effect on the seasonal dynamics of shoot growth. The first harmonics with a period of oscillation 92.0 days determine the nonlinearity of the seasonal trend of growth of shoots. Higher harmonics with a period of oscillation of 9.2 to 15.3 days form the resulting quasi–cyclic oscillation. Significant interclonal and intraclonal differences in the rhythm of daily growth of annual shoots were not revealed. On this basis, the proposed recommendations for agroforestry–technical events in the plantings of woolly–stemmed willow.
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Han, Chuanliang, Tian Wang, Yujie Wu, Yang Li, Yi Yang, Liang Li, Yizheng Wang, and Dajun Xing. "The Generation and Modulation of Distinct Gamma Oscillations with Local, Horizontal, and Feedback Connections in the Primary Visual Cortex: A Model Study on Large-Scale Networks." Neural Plasticity 2021 (January 18, 2021): 1–17. http://dx.doi.org/10.1155/2021/8874516.
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Gamma oscillation (GAMMA) in the local field potential (LFP) is a synchronized activity commonly found in many brain regions, and it has been thought as a functional signature of network connectivity in the brain, which plays important roles in information processing. Studies have shown that the response property of GAMMA is related to neural interaction through local recurrent connections (RC), feed-forward (FF), and feedback (FB) connections. However, the relationship between GAMMA and long-range horizontal connections (HC) in the brain remains unclear. Here, we aimed to understand this question in a large-scale network model for the primary visual cortex (V1). We created a computational model composed of multiple excitatory and inhibitory units with biologically plausible connectivity patterns for RC, FF, FB, and HC in V1; then, we quantitated GAMMA in network models at different strength levels of HC and other connection types. Surprisingly, we found that HC and FB, the two types of large-scale connections, play very different roles in generating and modulating GAMMA. While both FB and HC modulate a fast gamma oscillation (around 50-60 Hz) generated by FF and RC, HC generates a new GAMMA oscillating around 30 Hz, whose power and peak frequency can also be modulated by FB. Furthermore, response properties of the two GAMMAs in a network with both HC and FB are different in a way that is highly consistent with a recent experimental finding for distinct GAMMAs in macaque V1. The results suggest that distinct GAMMAs are signatures for neural connections in different spatial scales and they might be related to different functions for information integration. Our study, for the first time, pinpoints the underlying circuits for distinct GAMMAs in a mechanistic model for macaque V1, which might provide a new framework to study multiple gamma oscillations in other cortical regions.
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Zhang, Hao, Shih-Chieh Lin, and Miguel A. L. Nicolelis. "A distinctive subpopulation of medial septal slow-firing neurons promote hippocampal activation and theta oscillations." Journal of Neurophysiology 106, no. 5 (November 2011): 2749–63. http://dx.doi.org/10.1152/jn.00267.2011.
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The medial septum-vertical limb of the diagonal band of Broca (MSvDB) is important for normal hippocampal functions and theta oscillations. Although many previous studies have focused on understanding how MSVDB neurons fire rhythmic bursts to pace hippocampal theta oscillations, a significant portion of MSVDB neurons are slow-firing and thus do not pace theta oscillations. The function of these MSVDB neurons, especially their role in modulating hippocampal activity, remains unknown. We recorded MSVDB neuronal ensembles in behaving rats, and identified a distinct physiologically homogeneous subpopulation of slow-firing neurons (overall firing <4 Hz) that shared three features: 1) much higher firing rate during rapid eye movement sleep than during slow-wave (SW) sleep; 2) temporary activation associated with transient arousals during SW sleep; 3) brief responses (latency 15∼30 ms) to auditory stimuli. Analysis of the fine temporal relationship of their spiking and theta oscillations showed that unlike the theta-pacing neurons, the firing of these “pro-arousal” neurons follows theta oscillations. However, their activity precedes short-term increases in hippocampal oscillation power in the theta and gamma range lasting for a few seconds. Together, these results suggest that these pro-arousal slow-firing MSvDB neurons may function collectively to promote hippocampal activation.
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Zhu, J., G. Zhou, R. H. Zhang, and Z. Sun. "On the role of oceanic entrainment temperature (<I>T</I><sub>e</sub>) in decadal changes of El Niño/Southern Oscillation." Annales Geophysicae 29, no. 3 (March 10, 2011): 529–40. http://dx.doi.org/10.5194/angeo-29-529-2011.
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Abstract. The role of decadal changes in ocean thermal structure in modulating El Niño/Southern Oscillation (ENSO) properties was examined using a hybrid coupled model (HCM), consisting of a statistical atmospheric model and an oceanic general circulation model (OGCM) with an explicitly embedded empirical parameterization for the temperature of subsurface water entrained into the mixed layer (Te), which was constructed via an EOF analysis of model-based historical data. Using the empirical Te models constructed from two subperiods, 1963–1979 (Te63−79) and 1980–1996 (Te80−96), the coupled system exhibits striking different properties of interannual variability, including oscillation periods and the propagation characteristic of sea surface temperature anomalies (SSTAs) along the equator. In the Te63−79 run, the model features a 2–3 yr oscillation and a westward propagation of SSTAs along the equator, while in the Te80−96 run, it is characterized by a 4–5 yr oscillation and an eastward propagation. Furthermore, a Lag Covariance Analysis (LCOA) was utilized to illustrate the leading physical processes responsible for decadal change in SST. It is shown that the change in the structure of Te acts to modulate the relative strength of the zonal advective and thermocline feedbacks in the coupled system, leading to changes in ENSO properties. Two additional sensitive experiments were conducted to further illustrate the respective roles of the changes in ocean mean states and in Te in modulating ENSO behaviors. These decadal changes in the simulated ENSO properties are consistent with the observed shift occurred in the late 1970s and a previous simulation performed with an intermediate coupled model (ICM) described in Zhang and Busalacchi (2005), indicating a dominant role Te plays in decadal ENSO changes.
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Zhang, Wenjun, Xuebin Mei, Xin Geng, Andrew G. Turner, and Fei-Fei Jin. "A Nonstationary ENSO–NAO Relationship Due to AMO Modulation." Journal of Climate 32, no. 1 (December 4, 2018): 33–43. http://dx.doi.org/10.1175/jcli-d-18-0365.1.
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Abstract Many previous studies have demonstrated a high uncertainty in the relationship between El Niño–Southern Oscillation (ENSO) and the North Atlantic Oscillation (NAO). In the present work, decadal modulation by the Atlantic multidecadal oscillation (AMO) is investigated as a possible cause of the nonstationary ENSO–NAO relationship based on observed and reanalysis data. It is found that the negative ENSO–NAO correlation in late winter is significant only when ENSO and the AMO are in phase (AMO+/El Niño and AMO−/La Niña). However, no significant ENSO-driven atmospheric anomalies can be observed over the North Atlantic when ENSO and the AMO are out of phase (AMO−/El Niño and AMO+/La Niña). Further analysis indicates that the sea surface temperature anomaly (SSTA) in the tropical North Atlantic (TNA) plays an essential role in this modulating effect. Because of broadly analogous TNA SSTA responses to both ENSO and the AMO during late winter, a warm SSTA in the TNA is evident when El Niño occurs during a positive AMO phase, resulting in a significantly weakened NAO, and vice versa when La Niña occurs during a negative AMO phase. In contrast, neither the TNA SSTA nor the NAO shows a prominent change under out-of-phase combinations of ENSO and AMO. The AMO modulation and the associated effect of the TNA SSTA are shown to be well reproduced by historical simulations of the HadCM3 coupled model and further verified by forced experiments using an atmospheric circulation model. These offer hope that similar models will be able to make predictions for the NAO when appropriately initialized.
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Hu, Zeyuan, Aixue Hu, and Yongyun Hu. "Contributions of Interdecadal Pacific Oscillation and Atlantic Multidecadal Oscillation to Global Ocean Heat Content Distribution." Journal of Climate 31, no. 3 (January 22, 2018): 1227–44. http://dx.doi.org/10.1175/jcli-d-17-0204.1.
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Abstract Regional sea surface temperature (SST) mode variabilities, especially the La Niña–like Pacific Ocean temperature pattern known as the negative phase of the interdecadal Pacific oscillation (IPO) and the associated heat redistribution within the ocean, are the leading mechanisms explaining the recent global warming hiatus. Here version 1 of the Community Earth System Model (CESM) is used to examine how different phases of two leading decadal time scale SST modes, namely the IPO and the Atlantic multidecadal oscillation (AMO), contribute to heat redistribution in the global ocean in the absence of time-evolving external forcings. The results show that both the IPO and AMO contribute a similar magnitude to global mean surface temperature and ocean heat redistribution. Both modes contribute warmer surface temperature and higher upper ocean heat content in their positive phase, and the reverse in their negative phase. Regionally, patterns of ocean heat distribution in the upper few hundred meters of the tropical and subtropical Pacific Ocean depend highly on the IPO phase via the IPO-associated changes in the subtropical cell. In the Atlantic, ocean heat content is primarily associated with the state of the AMO. The interconnections between the IPO, AMO, and global ocean heat distribution are established through the atmospheric bridge and the Atlantic meridional overturning circulation. An in-phase variant of the IPO and AMO can lead to much higher surface temperatures and heat content changes than an out-of-phase variation. This result suggests that changes in the IPO and AMO are potentially capable of modulating externally forced SST and heat content trends.
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Chen, Jau-Ming, Ching-Hsuan Wu, Pei-Hsuan Chung, and Chung-Hsiung Sui. "Influence of Intraseasonal–Interannual Oscillations on Tropical Cyclone Genesis in the Western North Pacific." Journal of Climate 31, no. 12 (June 2018): 4949–61. http://dx.doi.org/10.1175/jcli-d-17-0601.1.
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Influences of intraseasonal–interannual oscillations on tropical cyclone (TC) genesis are evaluated by productivity of TC genesis ( PTCG) from the developing (TC d) and nondeveloping (TC n) precursory tropical disturbances (PTDs). A PTD is identified by a cyclonic tropical disturbance with a strong-enough intensity, a large-enough maximum center, and a long-enough lifespan. The percentage value of PTDs evolving into TC d is defined as PTCG. The analysis is performed over the western North Pacific (WNP) basin during the 1990–2014 warm season (May–September). The climatological PTCG in the WNP basin is 0.35. Counted in a common period, mean numbers of PTDs in the favorable and unfavorable conditions of climate oscillations for TC genesis [such as equatorial Rossby waves (ERWs), the Madden–Julian oscillation (MJO), and El Niño–Southern Oscillation (ENSO)], all exhibit a stable value close to the climatological mean [~31 (100 days)−1]. However, PTCG increases (decreases) during the phases of positive-vorticity (negative-vorticity) ERWs, the active (inactive) MJO, and El Niño (La Niña) years. PTCG varies from 0.17 in the most unfavorable environment (La Niña, inactive MJO, and negative-vorticity ERW) to 0.56 in the most favorable environment (El Niño, active MJO, and positive-vorticity ERW). ERWs are most effective in modulating TC genesis, especially in the negative-vorticity phases. Overall, increased PTCG is facilitated with strong and elongated 850-hPa relative vorticity overlapping a cyclonic shear line pattern, while decreased PTCG is related to weak relative vorticity. Relative vorticity acts as the most important factor to modulate PTCG, when compared with vertical wind shear and 700-hPa relative humidity.
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Zhang, Rong-Hua, and Antonio J. Busalacchi. "Interdecadal Change in Properties of El Niño–Southern Oscillation in an Intermediate Coupled Model." Journal of Climate 18, no. 9 (May 1, 2005): 1369–80. http://dx.doi.org/10.1175/jcli3340.1.
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Abstract The role of subsurface temperature variability in modulating El Niño–Southern Oscillation (ENSO) properties is examined using an intermediate coupled model (ICM), consisting of an intermediate dynamic ocean model and a sea surface temperature (SST) anomaly model. An empirical procedure is used to parameterize the temperature of subsurface water entrained into the mixed layer (Te) from sea level (SL) anomalies via a singular value decomposition (SVD) analysis for use in simulating sea surface temperature anomalies (SSTAs). The ocean model is coupled to a statistical atmospheric model that estimates wind stress anomalies also from an SVD analysis. Using the empirical Te models constructed from two subperiods, 1963–79 (T63–79e) and 1980–96 (T80–96e), the coupled system exhibits strikingly different properties of interannual variability (the oscillation period, spatial structure, and temporal evolution). For the T63–79e model, the system features a 2-yr oscillation and westward propagation of SSTAs on the equator, while for the T80–96e model, it is characterized by a 5-yr oscillation and eastward propagation. These changes in ENSO properties are consistent with the behavior shift of El Niño observed in the late 1970s. Heat budget analyses further demonstrate a controlling role played by the vertical advection of subsurface temperature anomalies in determining the ENSO properties.
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Manisty, Charlotte H., Keith Willson, Justin E. R. Davies, Zachary I. Whinnett, Resham Baruah, Yoseph Mebrate, Prapa Kanagaratnam, et al. "Induction of oscillatory ventilation pattern using dynamic modulation of heart rate through a pacemaker." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 295, no. 1 (July 2008): R219—R227. http://dx.doi.org/10.1152/ajpregu.00064.2008.
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For disease states characterized by oscillatory ventilation, an ideal dynamic therapy would apply a counteracting oscillation in ventilation. Modulating respiratory gas transport through the circulation might allow this. We explore the ability of repetitive alternations in heart rate, using a cardiac pacemaker, to elicit oscillations in respiratory variables and discuss the potential for therapeutic exploitation. By incorporating acute cardiac output manipulations into an integrated mathematical model, we observed that a rise in cardiac output should yield a gradual rise in end-tidal CO2 and, subsequently, ventilation. An alternating pattern of cardiac output might, therefore, create oscillations in CO2 and ventilation. We studied the effect of repeated alternations in heart rate of 30 beats/min with periodicity of 60 s, on cardiac output, respiratory gases, and ventilation in 22 subjects with implanted cardiac pacemakers and stable breathing patterns. End-tidal CO2 and ventilation developed consistent oscillations with a period of 60 s during the heart rate alternations, with mean peak-to-trough relative excursions of 8.4 ± 5.0% ( P < 0.0001) and 24.4 ± 18.8% ( P < 0.0001), respectively. Furthermore, we verified the mathematical prediction that the amplitude of these oscillations would depend on those in cardiac output ( r = 0.59, P = 0.001). Repetitive alternations in heart rate can elicit reproducible oscillations in end-tidal CO2 and ventilation. The size of this effect depends on the magnitude of the cardiac output response. Harnessed and timed appropriately, this cardiorespiratory mechanism might be exploited to create an active dynamic responsive pacing algorithm to counteract spontaneous respiratory oscillations, such as those causing apneic breathing disorders.
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Cai, Wenju, and Peter van Rensch. "Austral Summer Teleconnections of Indo-Pacific Variability: Their Nonlinearity and Impacts on Australian Climate." Journal of Climate 26, no. 9 (April 26, 2013): 2796–810. http://dx.doi.org/10.1175/jcli-d-12-00458.1.
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Abstract In austral summer, El Niño–Southern Oscillation (ENSO) covaries with the Indian Ocean Basin Mode (IOBM) and with the southern annular mode (SAM). The present study addresses how the IOBM and the SAM modulate the impact of ENSO on Australia. The authors show that the modulating effect of the SAM is limited; in particular, the SAM does not modify the ENSO teleconnection pattern. However, the IOBM extends ENSO-induced convection anomalies westward over northern Australia and over the eastern Indian Ocean, whereby extending the ENSO tropical teleconnection to the northwest of Australia. The IOBM also generates an equivalent-barotropic Rossby wave train through convection anomalies over northern Australia. The wave train shares an anomaly center over the Tasman Sea latitudes with the Pacific–South American (PSA) pattern, shifting the anomaly center of the PSA pattern to within a closer proximity to Australia. There is a strong asymmetry in the IOBM modulating effect. During an IOBM negative phase, which tends to coincide with La Niña events, the rainfall increase is far greater than the reduction during a positive IOBM phase, which tends to coincide with El Niño events. This modulation asymmetry is consistent with an asymmetry in the ENSO–rainfall teleconnection over Australia, in which the La Niña–rainfall teleconnection is stronger than the El Niño–rainfall teleconnection. This asymmetric ENSO–rainfall teleconnection ensures a higher coherence of northern Australia convective anomalies with La Niña or with a negative phase of the IOBM, hence a greater modification of the PSA pattern, underpinning the asymmetric modulating role of the IOBM.
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Wang, Rong, Peihua Feng, Yongchen Fan, and Ying Wu. "Spontaneous Electromagnetic Induction Modulating the Neuronal Dynamical Response." International Journal of Bifurcation and Chaos 29, no. 01 (January 2019): 1950005. http://dx.doi.org/10.1142/s0218127419500056.
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Spontaneous electromagnetic induction originating from neuronal electrical activity is believed to reflect the memory ability in the neural system and significantly modulates neural information transmission, but its fundamental effect on the neuronal dynamic properties is still not well understood. In this paper, we use a memristor to couple neuronal electrical activity and magnetic fields and study how the spontaneous electromagnetic induction modulates the neuronal dynamical response to external stimulation. It is found that the negative feedback of electromagnetic induction on the neuron significantly reduces the dynamical response range, decreases the oscillation amplitude and induces a higher firing frequency. Meanwhile, the memory effect on electromagnetic induction can induce two kinds of bistability, including the coexistence of a stable limit cycle and a fixed point, and the coexistence of two stable limit cycles. Furthermore, high electric driving for electromagnetic induction produces complex firing patterns with single, double and multiple frequencies. Our results not only further confirm the efficacy of spontaneous electromagnetic induction in modulating the neuronal dynamical properties but also provide insights into the possibilities of choosing suitable parameter spaces in studying the effects of external magnetic induction on brain functions.
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Jiang, Wen Bin, Qing Li, and Xiong Li. "The Development of a New Electromagnetic Field Generator for Anti-Scaling." Applied Mechanics and Materials 105-107 (September 2011): 2162–68. http://dx.doi.org/10.4028/www.scientific.net/amm.105-107.2162.
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Scaling exists commonly and its harm is huge. Because of this, design an amplitude-modulating electromagnetic field generator. The drive signal is obtained by amplitude modulation and power amplification. Generate two sine signals by the wien bridge and make the two signals through the MC1496 multiplier, the carrier’s amplitude changes with the modulator’s rule. And the frequency of carrier and modulator could be changed with the adjustment of the Oscillation resistance. Then, make use of D class amplifier TDA8920BTH to enlarge the power of modulated signal. At last, load the drive signal on a ferrite of magnetic coil to gain an electromagnetic field whose strength is modulated. Differ from the ordinary form of winding pipe with wire line, this design is making the magnetic coil close to a pipe. That’s more convenient for installing and removing. Of course, the concrete effect of descaling is needed to test by further experiments.
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Rouillard, A., and M. Lockwood. "Oscillations in the open solar magnetic flux with a period of 1.68 years: imprint on galactic cosmic rays and implications for heliospheric shielding." Annales Geophysicae 22, no. 12 (December 22, 2004): 4381–95. http://dx.doi.org/10.5194/angeo-22-4381-2004.
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Abstract. An understanding of how the heliosphere modulates galactic cosmic ray (GCR) fluxes and spectra is important, not only for studies of their origin, acceleration and propagation in our galaxy, but also for predicting their effects (on technology and on the Earth's environment and organisms) and for interpreting abundances of cosmogenic isotopes in meteorites and terrestrial reservoirs. In contrast to the early interplanetary measurements, there is growing evidence for a dominant role in GCR shielding of the total open magnetic flux, which emerges from the solar atmosphere and enters the heliosphere. In this paper, we relate a strong 1.68-year oscillation in GCR fluxes to a corresponding oscillation in the open solar magnetic flux and infer cosmic-ray propagation paths confirming the predictions of theories in which drift is important in modulating the cosmic ray flux. Key words. Interplanetary physics (Cosmic rays, Interplanetary magnetic fields)
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Pohl, B., N. Fauchereau, C. J. C. Reason, and M. Rouault. "Relationships between the Antarctic Oscillation, the Madden–Julian Oscillation, and ENSO, and Consequences for Rainfall Analysis." Journal of Climate 23, no. 2 (January 15, 2010): 238–54. http://dx.doi.org/10.1175/2009jcli2443.1.
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Abstract The Antarctic Oscillation (AAO) is the leading mode of atmospheric variability in the Southern Hemisphere mid- and high latitudes (south of 20°S). In this paper, the authors examine its statistical relationships with the major tropical climate signals at the intraseasonal and interannual time scales and their consequences on its potential influence on rainfall variability at regional scales. At the intraseasonal time scale, although the AAO shows its most energetic fluctuations in the 30–60-day range, it is not unambiguously related to the global-scale Madden–Julian oscillation (MJO) activity, with in particular no coherent phase relationship with the MJO index. Moreover, in the high southern latitudes, the MJO-associated anomaly fields do not appear to project coherently on the well-known AAO patterns and are never of an annular nature. At the interannual time scale, a strong teleconnection with ENSO is found during the peak of the austral summer season, corroborating previous studies. El Niño (La Niña) tends to correspond to a negative (positive) AAO phase. The results are statistically significant only when the seasonal mean fields averaged for the November through February season are considered. Based on these results, the authors then isolate the specific influence of the AAO on rainfall variability at both intraseasonal and interannual time scales. The example taken here is southern Africa, a region under the influence of both the MJO and ENSO, experiencing its main rainy season in austral summer and containing a relatively dense network of rain gauge measurements. At the interannual time scale, the significance of the teleconnections between southern African rainfall and the AAO reveals itself to be a statistical artifact and becomes very weak once the influence of ENSO is removed. At the intraseasonal time scale, the AAO is seen to significantly affect the rainfall amounts over much of the country, without interference with other modes of variability. Its influence in modulating the rain appears to be strongest during La Niña years.
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Zhang, Jing, Huili Li, Huajing Teng, Ting Zhang, Yonglun Luo, Mei Zhao, Yun-Qing Li, and Zhong Sheng Sun. "Regulation of Peripheral Clock to Oscillation of Substance P Contributes to Circadian Inflammatory Pain." Anesthesiology 117, no. 1 (July 1, 2012): 149–60. http://dx.doi.org/10.1097/aln.0b013e31825b4fc1.
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Background The daily fluctuations of many physiologic and behavioral parameters are differentially influenced by either central or peripheral clocks in mammals. Since substance P (SP) oscillates in some brain tissues and plays an indispensable role in modulating inflammatory pain at the spinal level, we speculated that SP mediates circadian nociception transmission at the spinal level. Methods In the present study behavioral observation, real-time polymerase chain reaction, luciferase assay, chromatin immunoprecipitation, and immunohistochemistry stain methods were used to investigate the role of SP in the spinal circadian nociception transmission and its regulation mechanism. Results Our results showed that under transcriptional regulation of BMAL1:CLOCK heterodimers, SP's coding gene Tac1 expression oscillates in dorsal root ganglion (n = 36), but not in the spinal dorsal horn. Further, the expression of SP cycled in the spinal dorsal horn, and this rhythmicity was potentially determined by circadian expression of Tac1 in dorsal root ganglion. Furthermore, the variation of SP expression induced by formalin was fluctuated in a similar rhythm to behavioral nociceptive response induced by formalin (n = 48); and the nociceptive behavioral circadian rhythm could be abolished through blockade of the SP-Neurokinin 1 receptor pathway (n = 70). Lastly, the variations of spinal SP expression and behavioral nociceptive response were in step, and both were changed by the deletion mutation of clock gene. Conclusions We conclude that spinal SP probably plays a pivotal role in modulating circadian inflammatory pain and suggest that peripheral circadian-regulated signaling is potentially an essential pathway for circadian nociceptive transmission.
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Terray, Pascal, and Sébastien Dominiak. "Indian Ocean Sea Surface Temperature and El Niño–Southern Oscillation: A New Perspective." Journal of Climate 18, no. 9 (May 1, 2005): 1351–68. http://dx.doi.org/10.1175/jcli3338.1.
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Abstract Here the 1976–77 climate regime shift that was accompanied by a remarkable change in the lead–lag relationships between Indian Ocean sea surface temperature (SST) and El Niño evolution is shown. After the 1976–77 regime shift, a correlation analysis suggests that southern Indian Ocean SSTs observed during late boreal winter are a key precursor in predicting El Niño evolution as the traditional oceanic heat content anomalies in the equatorial Pacific or zonal wind anomalies over the equatorial western Pacific. The possible physical mechanisms underlying this highly significant statistical relationship are discussed. After the 1976–77 regime shift, southern Indian Ocean SST anomalies produced by Mascarene high pulses during boreal winter trigger coupled air–sea processes in the tropical eastern Indian Ocean during the following seasons. This produces a persistent remote forcing on the Pacific climate system, promoting wind anomalies over the western equatorial Pacific and modulating the regional Hadley cell in the southwest Pacific. These modulations, in turn, excite Rossby waves, which produce quasi-stationary circulation anomalies in the extratropical South Pacific, responsible for the development of the southern branch of the “horseshoe” El Niño pattern. The change of the background SST state that occurred in the late 1970s over the Indian Ocean may also explain why ENSO evolution is different before and after the 1976–77 regime shift. These results shed some light on the possible influence of global warming or decadal fluctuations on El Niño evolution through changes in teleconnection patterns between the Indian and Pacific Oceans.
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Middlemas, Eleanor A., Amy C. Clement, Brian Medeiros, and Ben Kirtman. "Cloud Radiative Feedbacks and El Niño–Southern Oscillation." Journal of Climate 32, no. 15 (July 2, 2019): 4661–80. http://dx.doi.org/10.1175/jcli-d-18-0842.1.
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Abstract Cloud radiative feedbacks are disabled via “cloud-locking” in the Community Earth System Model, version 1.2 (CESM1.2), to result in a shift in El Niño–Southern Oscillation (ENSO) periodicity from 2–7 years to decadal time scales. We hypothesize that cloud radiative feedbacks may impact the periodicity in three ways: by 1) modulating heat flux locally into the equatorial Pacific subsurface through negative shortwave cloud feedback on sea surface temperature anomalies (SSTA), 2) damping the persistence of subtropical southeast Pacific SSTA such that the South Pacific meridional mode impacts the duration of ENSO events, or 3) controlling the meridional width of off-equatorial westerly winds, which impacts the periodicity of ENSO by initiating longer Rossby waves. The result of cloud-locking in CESM1.2 contrasts that of another study, which found that cloud-locking in a different global climate model led to decreased ENSO magnitude across all time scales due to a lack of positive longwave feedback on the anomalous Walker circulation. CESM1.2 contains this positive longwave feedback on the anomalous Walker circulation, but either its influence on the surface is decoupled from ocean dynamics or the feedback is only active on interannual time scales. The roles of cloud radiative feedbacks in ENSO in other global climate models are additionally considered. In particular, it is shown that one cannot predict the role of cloud radiative feedbacks in ENSO through a multimodel diagnostic analysis. Instead, they must be directly altered.
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Petrosino, Simona, Ciro Ricco, Enza De Lauro, Ida Aquino, and Mariarosaria Falanga. "Time evolution of medium and long-period ground tilting at Campi Flegrei caldera." Advances in Geosciences 52 (March 5, 2020): 9–17. http://dx.doi.org/10.5194/adgeo-52-9-2020.
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Abstract. We analyse tiltmeter time series recorded from April 2015 to March 2019 at three borehole instruments installed at Campi Flegrei caldera (Italy). We evaluate the crustal response in terms of ground tilting to external excitations of medium/long-period tidal constituents by applying a polarization analysis. The azimuths of the tilt vectors show well-defined polarization directions and the ground tilting planes oscillate with the periodicity of the corresponding tidal constituents. For two of the three tiltmeters, the average ground oscillation pattern related to the monthly Mm and fortnightly Mf constituents show seasonal variations, which can be ascribed to rainfall-induced tilting. In addition, for the same two instruments, a clear seasonal amplitude modulation of the diurnal S1 constituent appears in the time series, revealing the occurrence of site thermoelastic effects. The results indicate that the tidal tilting is mainly controlled by the local stress field distribution and rheology; in addition, seasonal exogenous factors like rainfalls play a role in modulating the ground deformation.
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Yang, Yang, Mengyun Li, Hailong Wang, Huimin Li, Pinya Wang, Ke Li, Meng Gao, and Hong Liao. "ENSO modulation of summertime tropospheric ozone over China." Environmental Research Letters 17, no. 3 (February 24, 2022): 034020. http://dx.doi.org/10.1088/1748-9326/ac54cd.
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Abstract Ozone (O3) is one of the most critical pollutants affecting air quality in China in recent years. In this study, different impacts of the El Niño–Southern Oscillation (ENSO) warm/cold phases on summertime tropospheric O3 over China are examined based on model simulations, ground measurements, and reanalysis data. Summertime surface O3 concentrations in China show a positive correlation with ENSO index during years 1990–2019, with the largest increases by 20% over southern China in El Niño (warm phase) relative to La Niña (cold phase) years. The ENSO modulation extends to the middle and even upper troposphere. Our analysis indicates that O3 flux convergence associated with weakened southerlies is the primary reason for the increase in tropospheric O3 over southern China. In addition, the O3 increase during El Niño years is mainly from domestic emissions in China. This study highlights the potential significance of ENSO in modulating tropospheric O3 concentrations in China, with great implications for O3 pollution mitigation.
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YIN, WEIWEI, and EBERHARD O. VOIT. "CONSTRUCTION AND CUSTOMIZATION OF STABLE OSCILLATION MODELS IN BIOLOGY." Journal of Biological Systems 16, no. 04 (December 2008): 463–78. http://dx.doi.org/10.1142/s0218339008002502.
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Oscillations exist at all levels of biological systems and are often crucial for their proper functioning. Among the various types of oscillations, limit cycles have received particular attention for more than one hundred years. Specifically, theorems have been established that characterize whether a system might have the capability of exhibiting limit cycles. However, the practical application of these theorems is usually cumbersome and there are hardly any guidelines for devising de novo models that exhibit limit cycles of a desired form. In this paper, we propose a simple method for constructing and customizing stable limit cycles in two-dimensional systems according to desired features, including frequency, amplitude, and phase shift between system variables. The method is based on "inverting" a criterion proposed by Lewis for characterizing oscillations in two-dimensional S-system models. First, we execute comprehensive simulations that result in a set of over 2000 prototype limit cycles. Second, we show with examples how these prototypes can be further customized to adhere to predetermined specifications. This two-step process is fast and efficacious, especially when one considers the paucity of alternative methods. Finally, we illustrate how one may create systems with more complex dynamics by modulating the prototypes with external input signals.
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Mu¨ller, M. R., and P. C. Shang. "The Generation of Internal Gravity Waves in a Multilayered Moving Fluid by a Flap-Type Wave Maker." Journal of Applied Mechanics 52, no. 2 (June 1, 1985): 247–52. http://dx.doi.org/10.1115/1.3169035.
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Experiments have examined the waveforms generated by a flap-type wave maker in a moving, three-layer fluid. Results show that the observed modulating waveforms could be predicted accurately for low frequencies and that if the two interfaces are sufficiently close together, both mode-one waves (whose amplitude vary in the vertical such that there is only one maximum) and mode-two waves (with a vertical amplitude structure that contains two relative maxima) are generated of similar amplitude. This results in downstream shifts from sinuous to varicose modes of oscillation.
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Matthews, J. M., D. W. Kurtz, and W. H. Wehlau. "The rich p-mode pulsation spectrum of HD 60435." Symposium - International Astronomical Union 123 (1988): 261–64. http://dx.doi.org/10.1017/s0074180900158188.
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Twelve cool Ap stars are known at present to undergo rapid light oscillations at low amplitude (ΔB < 0m.012) and with periods of minutes. These rapidly oscillating Ap (roAp) stars also exhibit amplitude modulation with timescales of days, which correspond to the magnetic/rotation periods (when those have been measured). In at least one case (HR 3831), 180° phase shifts in the dominant oscillation are seen twice per modulation cycle.
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Chen, Jau-Ming, Pei-Hua Tan, Liang Wu, Hui-Shan Chen, Jin-Shuen Liu, and Ching-Feng Shih. "Interannual Variability of Summer Tropical Cyclone Rainfall in the Western North Pacific Depicted by CFSR and Associated Large-Scale Processes and ISO Modulations." Journal of Climate 31, no. 5 (March 2018): 1771–87. http://dx.doi.org/10.1175/jcli-d-16-0805.1.
Full textAbstract:
This study examines the interannual variability of summer tropical cyclone (TC) rainfall (TCR) in the western North Pacific (WNP) depicted by the Climate Forecast System Reanalysis (CFSR). This interannual variability exhibits a maximum region near Taiwan (19°–28°N, 120°–128°E). Significantly increased TCR in this region is modulated by El Niño–Southern Oscillation (ENSO)-related large-scale processes. They feature elongated sea surface temperature warming in the tropical eastern Pacific and a southeastward-intensified monsoon trough. Increased TC movements are facilitated by interannual southerly/southeasterly flows in the northeastern periphery of the intensified monsoon trough to move from the tropical WNP toward the region near Taiwan, resulting in increased TCR. The coherent dynamic relations between interannual variability of summer TCR and large-scale environmental processes justify CFSR as being able to reasonably depict interannual characteristics of summer TCR in the WNP. For intraseasonal oscillation (ISO) modulations, TCs tend to cluster around the center of a 10–24-day cyclonic anomaly and follow its northwestward propagation from the tropical WNP toward the region near Taiwan. The above TC movements are subject to favorable background conditions provided by a northwest–southeasterly extending 30–60-day cyclonic anomaly. Summer TCR tends to increase (decrease) during El Niño (La Niña) years and strong (weak) ISO years. By comparing composite TCR anomalies and correlations with TCR variability, it is found that ENSO is more influential than ISO in modulating the interannual variability of summer TCR in the WNP.
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Pietrafesa, Leonard J., Shaowu Bao, Tingzhuang Yan, Michael Slattery, and Paul T. Gayes. "On Sea Level Variability and Trends in United States Coastal Waters and Relationships with Climate Factors." Advances in Adaptive Data Analysis 07, no. 01n02 (April 2015): 1550005. http://dx.doi.org/10.1142/s1793536915500053.
Full textAbstract:
Significant portions of the United States (U.S.) property, commerce and ecosystem assets are located at or near the coast, making them vulnerable to sea level variability and change, especially relative rises. Although global mean sea level (MSL) and sea level rise (SLR) are fundamental considerations, regional mean sea level (RSL) variability along the boundaries of U.S. along the two ocean basins are critical, particularly if the amplitudes of seasonal to annual to inter-annual variability is high. Of interest is that the conventional wisdom of the U.S. agencies, the National Aeronautics and Space Administration (NASA) and the National Oceanic and Atmospheric Administration (NOAA) which both contend that the sources of sea level rise are related principally to heat absorption and release by the ocean(s) to the atmosphere and vice versa, and by Polar glacier melting and freshwater input into the ocean(s). While these phenomena are of great importance to SLR and sea level variability (SLV), we assess a suite of climate factors and the Gulf Stream, for evidence of correlations and thus possible influences; though causality is beyond the scope of this study. In this study, climate factors related to oceanic and atmospheric heat purveyors and reservoirs are analyzed and assessed for possible correlations with sea level variability and overall trends on actionable scales (localized as opposed to global scale). The results confirm that oceanic and atmospheric temperature variability and the disposition of heat accumulation or the lack thereof, are important players in sea level variability and rise, but also that the Atlantic Multi-Decadal Oscillation, the El Niño-Southern Oscillation, the Pacific Decadal Oscillation, the Arctic Oscillation, the Quasi-Biennial Oscillation, the North Atlantic Oscillation, Solar Irradiance, the Western Boundary Current-Gulf Stream, and other climate factors, can have strong correlative and perhaps even causal, modulating effects on the monthly to seasonal to annual to inter-annual to decadal to multi-decadal sea level variability at the community level.
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Tomassini, Alice, and Alessandro D’Ausilio. "Passive sensorimotor stimulation triggers long lasting alpha-band fluctuations in visual perception." Journal of Neurophysiology 119, no. 2 (February 1, 2018): 380–88. http://dx.doi.org/10.1152/jn.00496.2017.
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Movement planning and execution rely on the anticipation and online control of the incoming sensory input. Evidence suggests that sensorimotor processes may synchronize visual rhythmic activity in preparation of action performance. Indeed, we recently reported periodic fluctuations of visual contrast sensitivity that are time-locked to the onset of an intended movement of the arm. However, the origin of the observed visual modulations has so far remained unclear because of the endogenous (and thus temporally undetermined) activation of the sensorimotor system that is associated with voluntary movement initiation. In this study, we activated the sensorimotor circuitry involved in the hand control in an exogenous and controlled way by means of peripheral stimulation of the median nerve and characterized the spectrotemporal dynamics of the ensuing visual perception. The stimulation of the median nerve triggers robust and long-lasting (∼1 s) alpha-band oscillations in visual perception, whose strength is temporally modulated in a way that is consistent with the changes in alpha power described at the neurophysiological level after sensorimotor stimulation. These findings provide evidence in support of a causal role of the sensorimotor system in modulating oscillatory activity in visual areas with consequences for visual perception. NEW & NOTEWORTHY This study shows that the peripheral activation of the somatomotor hand system triggers long-lasting alpha periodicity in visual perception. This demonstrates that not only the endogenous sensorimotor processes involved in movement preparation but also the passive stimulation of the sensorimotor system can synchronize visual activity. The present work suggests that oscillation-based mechanisms may subserve core (task independent) sensorimotor integration functions.
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Peings, Y., H. Douville, J. Colin, D. Saint Martin, and Gudrun Magnusdottir. "Snow–(N)AO Teleconnection and Its Modulation by the Quasi-Biennial Oscillation." Journal of Climate 30, no. 24 (December 2017): 10211–35. http://dx.doi.org/10.1175/jcli-d-17-0041.1.
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This study explores the wintertime extratropical atmospheric response to Siberian snow anomalies in fall, using observations and two distinct atmospheric general circulation models. The role of the quasi-biennial oscillation (QBO) in modulating this response is discussed by differentiating easterly and westerly QBO years. The remote influence of Siberian snow anomalies is found to be weak in the models, especially in the stratosphere where the “Holton–Tan” effect of the QBO dominates the simulated snow influence on the polar vortex. At the surface, discrepancies between composite analyses from observations and model results question the causal relationship between snow and the atmospheric circulation, suggesting that the atmosphere might have driven snow anomalies rather than the other way around. When both forcings are combined, the simulations suggest destructive interference between the response to positive snow anomalies and easterly QBO (and vice versa), at odds with the hypothesis that the snow–North Atlantic Oscillation/Arctic Oscillation [(N)AO] teleconnection in recent decades has been promoted by the QBO. Although model limitations in capturing the relationship exist, altogether these results suggest that the snow–(N)AO teleconnection may be a stochastic artifact rather than a genuine atmospheric response to snow-cover variability. This study adds to a growing body of evidence suggesting that climate models do not capture a robust and stationary snow–(N)AO relationship. It also highlights the need for extending observations and/or improving models to progress on this matter.
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Fan, Yi, Ke Fan, Xiuhua Zhu, and Klaus Fraedrich. "El Niño–Related Summer Precipitation Anomalies in Southeast Asia Modulated by the Atlantic Multidecadal Oscillation." Journal of Climate 32, no. 22 (October 30, 2019): 7971–87. http://dx.doi.org/10.1175/jcli-d-19-0049.1.
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Abstract How the Atlantic multidecadal oscillation (AMO) affects El Niño–related signals in Southeast Asia is investigated in this study on a subseasonal scale. Based on observational and reanalysis data, as well as numerical model simulations, El Niño–related precipitation anomalies are analyzed for AMO positive and negative phases, which reveals a time-dependent modulation of the AMO. 1) In May–June, the AMO influences the precipitation in southern China (SC) and the Indochina peninsula (ICP) by modulating the El Niño–related air–sea interaction over the western North Pacific (WNP). During negative AMO phases, cold sea surface temperature anomalies (SSTAs) over the WNP favor the maintaining of the WNP anomalous anticyclone (WNPAC). The associated southerly (westerly) anomalies on the northwest (southwest) flank of the WNPAC enhance (reduce) the climatological moisture transport to SC (the ICP) and result in wetter (drier) than normal conditions. In contrast, during positive AMO phases, weak SSTAs over the WNP lead to limited influence of El Niño on precipitation in Southeast Asia. 2) In July–August, the teleconnection impact from the North Atlantic is more manifest than that in May–June. During positive AMO phases, the warmer than normal North Atlantic favors anomalous wave trains, which propagate along the “great circle route” and result in positive pressure anomalies over SC, consequently suppressing precipitation in SC and the ICP. During negative AMO phases, the anomalous wave trains tend to propagate eastward from Europe to Northeast Asia along the summer Asian jet, exerting limited influence on Southeast Asia.