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Shargorodskyi, Serhiy, Volodymyr Rutkevych i Vadym Zakrevskyi. "Modeling of Working Processes of an Adjustable APN Type PVC 1.85 Taking Into Account Parametric Oscillations". Central Ukrainian Scientific Bulletin. Technical Sciences, nr 4(35) (2021): 33–43. http://dx.doi.org/10.32515/2664-262x.2021.4(35).33-43.
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The paper presents the calculation results of the two mathematical models of the variable displacement axial piston pumps PVC 1.85. In the first mathematical model of the pistons averaged force was used, the application point of which corresponds to the offset of the swash plate’s swivel axis. In the second mathematical model the parametric change of the pistons consolidated force magnitude and the coordinates of its application point was taken into account.
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Lückoff, F., M. Naster, J. S. Müller, M. Sieber, I. Litvinov i K. Oberleithner. "Impact of runner crown shape modifications on the onset of the precessing vortex core". IOP Conference Series: Earth and Environmental Science 1079, nr 1 (1.09.2022): 012051. http://dx.doi.org/10.1088/1755-1315/1079/1/012051.
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Abstract In this experimental study, a passive flow control concept is provided to extend the stable part load operation regime by shifting the rise of the precessing vortex core (PVC), also known as vortex rope, toward lower mass flows respectively deeper part loads. A parametrized runner crown design working as a passive flow control device is derived. This control device aims for shifting the bifurcation point of the PVC to lower flow rates. To determine the most influential design parameters and derive an optimized runner crown design, a design of experiments (DoE) approach is used. This DoE approach is based on data obtained from differential pressure sensors inside the draft tube wall of a generic hydro turbine test rig using air as working fluid. By means of stochastic modeling, the growth rate of the PVC mode is derived from the statistics of the measured pressure signals. The growth rate is used to estimate the bifurcation point of the PVC characterized by a certain normalized flow rate. It is shown that the stable part load operation regime is extended by up to 25% due to the passive impact of the modified runner crown. Moreover, the operational range featuring considerable PVC-induced pressure oscillations is diminished and the pressure recovery of the draft tube is improved compared to the baseline case.
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Litvinov, Ivan, Dmitriy Sharaborin, Evgeny Gorelikov, Vladimir Dulin, Sergey Shtork, Sergey Alekseenko i Kilian Oberleithner. "Modal Decomposition of the Precessing Vortex Core in a Hydro Turbine Model". Applied Sciences 12, nr 10 (19.05.2022): 5127. http://dx.doi.org/10.3390/app12105127.
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We report on the experimental study of a precessing vortex core (PVC) in an air model of a Francis turbine. The focus is placed on the modal decomposition of the PVC that occurs in the draft tube of the model turbine for a range of operation conditions. The turbulent flow fluctuations in the draft tube are assessed using stereo particle image velocimetry (PIV) measurements. Proper orthogonal decomposition (POD) is applied to the antisymmetric and symmetric components of the velocity fields to distinguish the dynamics of the azimuthal instabilities. The pressure pulsations induced by the PVC are measured by four pressure sensors mounted on the wall of the hydro turbine draft tube. Spatial Fourier decomposition is applied to the signals of the pressure sensors to identify the contributions of azimuthal modes, m=1 and m=2, to the total pressure fluctuations. The analysis based on velocity and pressure data shows similar results regarding the identification of the PVC. The contribution of the m=2 mode to the overall turbulent kinetic energy is significant for the part load regimes, where the flow rates are twice as low as at the best efficiency point (BEP). It is also shown that this mode is not the higher harmonic of the PVC, suggesting that it is driven by a different instability. Finally, we show a linear fit of the saturation amplitudes of the m=1 and m=2 oscillations to determine the critical bifurcation points of these modes. This yields critical swirl numbers of Scr=0.47 and 0.61, respectively. The fact that the PVC dynamics in hydro turbines are driven by two individual instabilities is relevant for the development of tailored active flow control of the PVC.
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Grimble, T. A., i A. Agarwal. "Characterisation of acoustically linked oscillations in cyclone separators". Journal of Fluid Mechanics 780 (2.09.2015): 45–59. http://dx.doi.org/10.1017/jfm.2015.441.
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The hydrodynamic oscillations of a cyclone separator – in particular the precessing vortex core (PVC) phenomena – are investigated by measuring their radiated sound spectra. Strong coherence was observed between internal flow oscillations measured via hot wire anemometry and the external acoustic field measured via microphone. This means that the oscillations can be characterised by using acoustics as a proxy. The oscillations cause narrow-band noise, referred to as cyclone hum. System characterisation by dimensional analysis used velocity and length scales of the vortex core region as scaling parameters. The relevant non-dimensional parameters are a Strouhal number for the cyclone hum centre frequency, a Reynolds number, a geometry based swirl number and numerous geometric scales defining the shape of the device. Cyclones with multiple sizes of inlets and outlets were tested at different flow rates using external microphones to detect the cyclone hum. The results produce an excellent collapse of the data, yielding a simple relationship for Strouhal number as a function of swirl number and the outlet diameter ratio. The non-invasive method of examining oscillations that is presented in this paper could be applied to other swirling systems.
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Scavuzzo, Rudolph J. "Oscillating Stress on Viscoelastic Behavior of Thermoplastic Polymers". Journal of Pressure Vessel Technology 122, nr 3 (12.04.2000): 386–89. http://dx.doi.org/10.1115/1.556197.
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Polymers are used in many applications where they are subjected to cyclic stresses. PVC and HDPE piping are often used in systems that include rotating machinery that cause mechanical vibration. Recent testing of thermoplastics indicates that there may be a large effect on the viscoelastic strains of thermoplastics from oscillating stresses. Cyclic loading on the permanent set of cross-linked elastomers has been studied. Perhaps, as expected, the effect of the oscillating behavior is measurable. Two types of tests have been conducted. First, tensile tests on HDPE standard specimens were conducted where oscillating stresses were superimposed onto an initial static or mean stress. These measurements showed a rapid decrease in the oscillating stresses when compared to measurements when steady nonoscillating stresses are applied to the same type of specimen. In the second test series, pressurized HDPE piping was subject to oscillating bending stresses. Ratcheting of the hoop strains in the pipe occurs. Results show that these strains follow the constitutive relationships of linear viscoelasticity and experimental results imply that viscoelastic changes are accelerated by stress oscillations. These preliminary results seem to indicate that the effects of oscillating stresses on the viscoelastic behavior of thermoplastics may be significant. A systematic study is required to further understand this behavior. [S0094-9930(00)02403-3]
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Kirollos, Ramy, Robert S. Allison i Stephen Palmisano. "Cortical Correlates of the Simulated Viewpoint Oscillation Advantage for Vection". Multisensory Research 30, nr 7-8 (2017): 739–61. http://dx.doi.org/10.1163/22134808-00002593.
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Behavioural studies have consistently found stronger vection responses for oscillating, compared to smooth/constant, patterns of radial flow (the simulated viewpoint oscillation advantage for vection). Traditional accounts predict that simulated viewpoint oscillation should impair vection by increasing visual–vestibular conflicts in stationary observers (as this visual oscillation simulates self-accelerations that should strongly stimulate the vestibular apparatus). However, support for increased vestibular activity during accelerating vection has been mixed in the brain imaging literature. This fMRI study examined BOLD activity in visual (cingulate sulcus visual area — CSv; medial temporal complex — MT+; V6; precuneus motion area — PcM) and vestibular regions (parieto-insular vestibular cortex — PIVC/posterior insular cortex — PIC; ventral intraparietal region — VIP) when stationary observers were exposed to vection-inducing optic flow (i.e., globally coherent oscillating and smooth self-motion displays) as well as two suitable control displays. In line with earlier studies in which no vection occurred, CSv and PIVC/PIC both showed significantly increased BOLD activity during oscillating global motion compared to the other motion conditions (although this effect was found for fewer subjects in PIVC/PIC). The increase in BOLD activity in PIVC/PIC during prolonged exposure to the oscillating (compared to smooth) patterns of global optical flow appears consistent with vestibular facilitation.
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Paternina-Verona, Duban A., Oscar E. Coronado-Hernández, Hector G. Espinoza-Román, Vicente S. Fuertes-Miquel i Helena M. Ramos. "Rapid Filling Analysis with an Entrapped Air Pocket in Water Pipelines Using a 3D CFD Model". Water 15, nr 5 (21.02.2023): 834. http://dx.doi.org/10.3390/w15050834.
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A filling operation generates continuous changes over the shape of an air–water interface, which can be captured using a 3D CFD model. This research analyses the influence of different hydro-pneumatic tank pressures and air pocket sizes as initial conditions for studying rapid filling operations in a 7.6 m long PVC pipeline with an irregular profile, using the OpenFOAM software. The analysed scenarios were validated using experimental measurements, where the 3D CFD model was suitable for simulating them. In addition, a mesh sensitivity analysis was performed. Air pocket pressure patterns, water velocity oscillations, and the different shapes of the air–water interface were analysed.
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Roy, S., T. Yi, N. Jiang, G. H. Gunaratne, I. Chterev, B. Emerson, T. Lieuwen, A. W. Caswell i J. R. Gord. "Dynamics of robust structures in turbulent swirling reacting flows". Journal of Fluid Mechanics 816 (8.03.2017): 554–85. http://dx.doi.org/10.1017/jfm.2017.71.
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High-speed synchronized stereo particle-imaging velocimetry and OH planar laser-induced fluorescence (PIV/OH-PLIF) measurements are performed on multiple $R{-}\unicode[STIX]{x1D703}$ planes downstream of a high-Reynolds-number swirling jet. Dynamic-mode decomposition (DMD) – a frequency-resolved data-reduction technique – is used to identify and characterize recurrent flow structures. Illustrative results are presented in a swirling flow field for two cases – the nominal flow dynamics and where self-excited combustion driven oscillations provide strong axisymmetric narrowband forcing of the flow. The robust constituent of the nominal reacting swirl flow corresponds to a helical shear-layer disturbance at a Strouhal number ($St$) of ${\sim}0.30$, $St=fD/U_{0}$, where $f$, $D$ and $U_{0}$ denote the precessing vortex core (PVC) frequency (${\sim}800~\text{Hz}$), the swirler exit diameter (19 mm) and the bulk velocity at the swirler exit ($50~\text{m}~\text{s}^{-1}$) respectively. Planar projections of the PVC reveal a pair of oscillating skew-symmetric regions of velocity, vorticity and OH-PLIF intensity that rotate in the same direction as the mean tangential flow. During combustion instabilities, the large-amplitude acoustics-induced axisymmetric forcing of the flow results in a fundamentally different flow response dominated by a nearly axisymmetric disturbance and almost complete suppression of the large-scale helical shear-layer disturbances dominating the nominal flow. In addition, reverse axial flows around the centreline are significantly reduced. Time traces of the robust constituent show reverse axial flows around the centreline and negative axial vorticity along the inner swirling shear layer when the planar velocity is in the same direction as the mean tangential flow. For both stable and unstable combustion, recurrent flow structures decay rapidly downstream of the air swirler, as revealed by the decreasing amplitude of the velocity, axial vorticity and OH-PLIF intensity.
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Brown, Jessica, Ben Grayson, Joanna C. Neill, Michael Harte, Mark J. Wall i Richard T. Ngomba. "Oscillatory Deficits in the Sub-Chronic PCP Rat Model for Schizophrenia Are Reversed by mGlu5 Receptor-Positive Allosteric Modulators VU0409551 and VU0360172". Cells 12, nr 6 (16.03.2023): 919. http://dx.doi.org/10.3390/cells12060919.
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The cognitive deficits of schizophrenia are linked to imbalanced excitatory and inhibitory signalling in the prefrontal cortex (PFC), disrupting gamma oscillations. We previously demonstrated that two mGlu5 receptor-positive allosteric modulators (PAMs), VU0409551 and VU0360172, restore cognitive deficits in the sub-chronic PCP (scPCP) rodent model for schizophrenia via distinct changes in PFC intracellular signalling molecules. Here, we have assessed ex vivo gamma oscillatory activity in PFC slices from scPCP rats and investigated the effects of VU0409551 and VU0360172 upon oscillatory power. mGlu5 receptor, protein kinase C (PKC), and phospholipase C (PLC) inhibition were also used to examine ‘modulation bias’ in PAM activity. The amplitude and area power of gamma oscillations were significantly diminished in the scPCP model. Slice incubation with either VU0409551 or VU0360172 rescued scPCP-induced oscillatory deficits in a concentration-dependent manner. MTEP blocked the PAM-induced restoration of oscillatory power, confirming the requirement of mGlu5 receptor modulation. Whilst PLC inhibition prevented the power increase mediated by both PAMs, PKC inhibition diminished the effects of VU0360172 but not VU0409551. This aligns with previous reports that VU0409551 exhibits preferential activation of the phosphatidylinositol-3-kinase (PI3K) signalling pathway over the PKC cascade. Restoration of the excitatory/inhibitory signalling balance and gamma oscillations may therefore underlie the mGluR5 PAM-mediated correction of scPCP-induced cognitive deficits.
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Violin, Jonathan D., Jin Zhang, Roger Y. Tsien i Alexandra C. Newton. "A genetically encoded fluorescent reporter reveals oscillatory phosphorylation by protein kinase C". Journal of Cell Biology 161, nr 5 (2.06.2003): 899–909. http://dx.doi.org/10.1083/jcb.200302125.
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Signals transduced by kinases depend on the extent and duration of substrate phosphorylation. We generated genetically encoded fluorescent reporters for PKC activity that reversibly respond to stimuli activating PKC. Specifically, phosphorylation of the reporter expressed in mammalian cells causes changes in fluorescence resonance energy transfer (FRET), allowing real time imaging of phosphorylation resulting from PKC activation. Targeting of the reporter to the plasma membrane, where PKC is activated, reveals oscillatory phosphorylation in HeLa cells in response to histamine. Each oscillation in substrate phosphorylation follows a calcium oscillation with a lag of ∼10 s. Novel FRET-based reporters for PKC translocation, phosphoinositide bisphosphate conversion to IP3, and diacylglycerol show that in HeLa cells the oscillatory phosphorylations correlate with Ca2+-controlled translocation of conventional PKC to the membrane without oscillations of PLC activity or diacylglycerol. However, in MDCK cells stimulated with ATP, PLC and diacylglycerol fluctuate together with Ca2+ and phosphorylation. Thus, specificity of PKC signaling depends on the local second messenger-controlled equilibrium between kinase and phosphatase activities to result in strict calcium-controlled temporal regulation of substrate phosphorylation.
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del Pozo, R., V. Diez i G. Salazar. "Start-up of a pilot-scale anaerobic fixed film reactor at low temperature treating slaughterhouse wastewater". Water Science and Technology 46, nr 4-5 (1.08.2002): 215–22. http://dx.doi.org/10.2166/wst.2002.0590.
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A pilot-scale anaerobic fixed film reactor (AFFR) with vertically arranged PVC tubes as biomass carrier, treating poultry slaughterhouse wastewater was started-up in 74 days at temperatures between 20-24°C. The start-up process consisted of a long acclimatization phase followed by a low loaded growth phase, a gradual increase of OLR up to 9.2 kg COD/m3d, and a final maturation phase at moderated loads of 2.7 kg COD/m3d at which total COD removal efficiencies of 57% were achieved. Alkalinity ratio IA:PA was found to be the best control parameter to avoid VFA accumulation. OLR increase based on pH control was not satisfactory because changes in CO2 solubility caused daily by temperature and flow variations led to pH oscillations of 0.2 units. The low wastewater alkalinity, 260 mg/l CaCO3, was insufficient to buffer the pH system, therefore the pH decrease associated with the VFA accumulation was not easily detected and could not be used as a way of OLR control. Organic matter removal took place by accumulation and biodegradation processes. Limitation in the reactor hydrodynamics and particulate fraction hydrolysis was detected at high flow rates.
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Tsunoda, Y., H. Yoshida i C. Owyang. "Structural requirements of CCK analogues to differentiate second messengers and pancreatic secretion". American Journal of Physiology-Gastrointestinal and Liver Physiology 271, nr 1 (1.07.1996): G8—G19. http://dx.doi.org/10.1152/ajpgi.1996.271.1.g8.
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We previously demonstrated that, in rat pancreatic acinar cells, the high-affinity cholecystokinin (CCK) receptor agonist JMV-180 utilizes the phospholipase A2 (PLA2) cascade to mediate Ca2+ oscillations and amylase secretion. In contrast, the low-affinity CCK receptor utilizes the phospholipase C beta 1 (PLC beta 1) pathway. We have investigated structural requirements of CCK analogues to activate different intracellular pathways. CCK analogues such as CCK-8 [Met28,31; half-maximal effective concentration (EC50) = 0.4 pM], CCK-7 (Met28,31; EC50 = 0.7 pM), and NONA (Thr28/Nle31; EC50 = 5 pM) caused a biphasic amylase secretion. Reduction of secretion occurred with high doses of these peptides (> 100 pM). In contrast, CCK-5 (Met31; EC50 = 20,000pM), JMV-180 (Nle28,31; 1,500 pM), and OPE (Nle28,31; 200 pM) caused a monophasic secretion. CCK-8, but not JMV-180, increased protein kinase C (PKC) activities. The PKC activator phorbol ester inhibited an increase in myo-inositol 1,4,5-trisphosphate levels induced by CCK-8 and abolished monophasic amylase secretion induced by OPE. CCK-8, CCK-7, and NONA caused Ca2+ oscillations (< 100 pM) or large Ca2+ transients (> 100 pM). In contrast, JMV-180 and OPE evoked Ca2+ oscillations, even in high doses. Ca(2+)-signaling modes induced by CCK-5 were intermediate types between CCK-8 and JMV-180. CCK-8- and CCK-7-stimulated Ca2+ spikes were inhibited by the PLC inhibitor U-73122, but not by the PLA2 inhibitor ONO-RS-082. The action of CCK-5 was only partially sensitive to the PLC inhibitor. In contrast, JMV-180- and OPE-stimulated Ca2+ oscillations were inhibited by the PLA2, but not by the PLC, inhibitor. NONA was sensitive to PLC and PLA2 inhibitors. Although JMV-180 differs from CCK-8 by having an Asp-2 phenylethylester, rather than an Asp-phenylalanine amide, it is unlikely that these differences in the carboxyl terminus are important in determining which second-messenger systems will be activated. This is because CCK-5 (Phe33-CONH2) causes monophasic amylase secretion and Ca2+ oscillation in a manner similar to those induced by JMV-180 (2-phenylethylester). Meanwhile NONA (Phe33-CONH2) appeared to activate PLC and PLA2 pathways. The actions of all CCK analogues were abolished by L-364,718, indicating mediation by CCK-A receptors. Therefore, depending on the agonists used, CCK-A receptor activation in pancreatic acini may result in differential involvement of second-messenger systems, Ca2+ signal transduction, and amylase secretion. On the basis of the amino acid sequence of the carboxy terminus of CCK analogues, it appears that key amino acids for this differentiation are Met28 (or Thr28) for PLC pathways and Nle28 for PLA2 pathways.
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Espelt, Maria V., Ana Y. Estevez, Xiaoyan Yin i Kevin Strange. "Oscillatory Ca2+ Signaling in the Isolated Caenorhabditis elegans Intestine". Journal of General Physiology 126, nr 4 (26.09.2005): 379–92. http://dx.doi.org/10.1085/jgp.200509355.
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Defecation in the nematode Caenorhabditis elegans is a readily observable ultradian behavioral rhythm that occurs once every 45–50 s and is mediated in part by posterior body wall muscle contraction (pBoc). pBoc is not regulated by neural input but instead is likely controlled by rhythmic Ca2+ oscillations in the intestinal epithelium. We developed an isolated nematode intestine preparation that allows combined physiological, genetic, and molecular characterization of oscillatory Ca2+ signaling. Isolated intestines loaded with fluo-4 AM exhibit spontaneous rhythmic Ca2+ oscillations with a period of ∼50 s. Oscillations were only detected in the apical cell pole of the intestinal epithelium and occur as a posterior-to-anterior moving intercellular Ca2+ wave. Loss-of-function mutations in the inositol-1,4,5-trisphosphate (IP3) receptor ITR-1 reduce pBoc and Ca2+ oscillation frequency and intercellular Ca2+ wave velocity. In contrast, gain-of-function mutations in the IP3 binding and regulatory domains of ITR-1 have no effect on pBoc or Ca2+ oscillation frequency but dramatically increase the speed of the intercellular Ca2+ wave. Systemic RNA interference (RNAi) screening of the six C. elegans phospholipase C (PLC)–encoding genes demonstrated that pBoc and Ca2+ oscillations require the combined function of PLC-γ and PLC-β homologues. Disruption of PLC-γ and PLC-β activity by mutation or RNAi induced arrhythmia in pBoc and intestinal Ca2+ oscillations. The function of the two enzymes is additive. Epistasis analysis suggests that PLC-γ functions primarily to generate IP3 that controls ITR-1 activity. In contrast, IP3 generated by PLC-β appears to play little or no direct role in ITR-1 regulation. PLC-β may function instead to control PIP2 levels and/or G protein signaling events. Our findings provide new insights into intestinal cell Ca2+ signaling mechanisms and establish C. elegans as a powerful model system for defining the gene networks and molecular mechanisms that underlie the generation and regulation of Ca2+ oscillations and intercellular Ca2+ waves in nonexcitable cells.
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Jia, Xin. "The Analysis of Parkinsons Disease using Phase-Amplitude Coupling Method". Theoretical and Natural Science 4, nr 1 (28.04.2023): 735–42. http://dx.doi.org/10.54254/2753-8818/4/20220695.
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Parkinson's disease (PD) is now the second most prevalent chronic neurological illness worldwide. For motor symptoms of PD, PD is linked to a number of dyskinesia, including rigidity, bradykinesia, postural instability, and tremor at rest. PD dyskinesia is the most common cause of Parkinsonism. Meanwhile, PD dyskinesia may be closely linked to the neural oscillations between neural circuits. PD dyskinesia is associated, in particular, with beta oscillation, which is directly related to the incidence and development of the motor. For the purpose of analysing neural oscillations between neural circuits, phase-amplitude coupling (PAC) can be utilised as a biomarker. As a potential biomarker of beta oscillation, PAC has been widely used in the research of PD. Therefore, this article reviews the latest concepts of dyskinesia, methods of calculating PAC and applications of PAC in Parkinson's disease, aiming to provide a good theoretical basis for finding neural circuits involved in PD dyskinesia to establish better deep brain stimulation therapy.
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Yin, Liyong, Fan Tian, Rui Hu, Zhaohui Li i Fuzai Yin. "Estimating Phase Amplitude Coupling between Neural Oscillations Based on Permutation and Entropy". Entropy 23, nr 8 (18.08.2021): 1070. http://dx.doi.org/10.3390/e23081070.
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Cross-frequency phase–amplitude coupling (PAC) plays an important role in neuronal oscillations network, reflecting the interaction between the phase of low-frequency oscillation (LFO) and amplitude of the high-frequency oscillations (HFO). Thus, we applied four methods based on permutation analysis to measure PAC, including multiscale permutation mutual information (MPMI), permutation conditional mutual information (PCMI), symbolic joint entropy (SJE), and weighted-permutation mutual information (WPMI). To verify the ability of these four algorithms, a performance test including the effects of coupling strength, signal-to-noise ratios (SNRs), and data length was evaluated by using simulation data. It was shown that the performance of SJE was similar to that of other approaches when measuring PAC strength, but the computational efficiency of SJE was the highest among all these four methods. Moreover, SJE can also accurately identify the PAC frequency range under the interference of spike noise. All in all, the results demonstrate that SJE is better for evaluating PAC between neural oscillations.
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Sase, Takumi, i Keiichi Kitajo. "The metastable brain associated with autistic-like traits of typically developing individuals". PLOS Computational Biology 17, nr 4 (16.04.2021): e1008929. http://dx.doi.org/10.1371/journal.pcbi.1008929.
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Metastability in the brain is thought to be a mechanism involved in the dynamic organization of cognitive and behavioral functions across multiple spatiotemporal scales. However, it is not clear how such organization is realized in underlying neural oscillations in a high-dimensional state space. It was shown that macroscopic oscillations often form phase-phase coupling (PPC) and phase-amplitude coupling (PAC), which result in synchronization and amplitude modulation, respectively, even without external stimuli. These oscillations can also make spontaneous transitions across synchronous states at rest. Using resting-state electroencephalographic signals and the autism-spectrum quotient scores acquired from healthy humans, we show experimental evidence that the PAC combined with PPC allows amplitude modulation to be transient, and that the metastable dynamics with this transient modulation is associated with autistic-like traits. In individuals with a longer attention span, such dynamics tended to show fewer transitions between states by forming delta-alpha PAC. We identified these states as two-dimensional metastable states that could share consistent patterns across individuals. Our findings suggest that the human brain dynamically organizes inter-individual differences in a hierarchy of macroscopic oscillations with multiple timescales by utilizing metastability.
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Wang, JianGang, XiaHuan Gao, YaLi Wang, MengMeng Wang, ChunBo Ge, ZhiHua Liu, Xin-E. Xie, ZhengYue Chen, JingGui Song i ChengBiao Lu. "The physiological modulation by intracellular kinases of hippocampal γ-oscillation in vitro". American Journal of Physiology-Cell Physiology 318, nr 5 (1.05.2020): C879—C888. http://dx.doi.org/10.1152/ajpcell.00199.2019.
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Hippocampal network oscillations at gamma frequency band (γ-oscillation, 20–80 Hz) are synchronized synaptic activities generated by the interactions between the excitatory and inhibitory interneurons and are associated with higher brain function such as learning and memory. Despite extensive studies about the modulation of intracellular kinases on synaptic transmission and plasticity, little is known about the effects of these kinases on γ-oscillations. In this study, we examined the effects of several critical intracellular kinases such as cyclic AMP-dependent protein kinase (PKA), protein kinase B (PKB)/Akt, protein kinase C (PKC), extracellular-regulated protein kinases (ERK) and AMP-activated protein kinase (AMPK), known to regulate synaptic transmission, on hippocampal γ-oscillations in vitro. We found that AMPK inhibitor but not PKA, PKC, or ERK inhibitor, strongly enhanced the power of γ-oscillation (γ-power) and that Akt inhibitor weakly increased γ-power. Western blot analysis confirmed that AMPK inhibitor reduced the expression of p-AMPK but not total AMPK. By using the slice whole cell voltage-clamp technique, we found that AMPK inhibitor increased the frequency but not amplitude of spontaneous inhibitory postsynaptic currents (sIPSC) and had no effect on either frequency or amplitude of spontaneous excitatory postsynaptic currents (sEPSC). Therefore, AMPK activation negatively modulates hippocampal γ-oscillation via modulation of the inhibitory neurons.
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Zhong, Weiwei, Mareva Ciatipis, Thérèse Wolfenstetter, Jakob Jessberger, Carola Müller, Simon Ponsel, Yevgenij Yanovsky, Jurij Brankačk, Adriano B. L. Tort i Andreas Draguhn. "Selective entrainment of gamma subbands by different slow network oscillations". Proceedings of the National Academy of Sciences 114, nr 17 (10.04.2017): 4519–24. http://dx.doi.org/10.1073/pnas.1617249114.
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Theta oscillations (4–12 Hz) are thought to provide a common temporal reference for the exchange of information among distant brain networks. On the other hand, faster gamma-frequency oscillations (30–160 Hz) nested within theta cycles are believed to underlie local information processing. Whether oscillatory coupling between global and local oscillations, as showcased by theta-gamma coupling, is a general coding mechanism remains unknown. Here, we investigated two different patterns of oscillatory network activity, theta and respiration-induced network rhythms, in four brain regions of freely moving mice: olfactory bulb (OB), prelimbic cortex (PLC), parietal cortex (PAC), and dorsal hippocampus [cornu ammonis 1 (CA1)]. We report differential state- and region-specific coupling between the slow large-scale rhythms and superimposed fast oscillations. During awake immobility, all four regions displayed a respiration-entrained rhythm (RR) with decreasing power from OB to CA1, which coupled exclusively to the 80- to 120-Hz gamma subband (γ2). During exploration, when theta activity was prevailing, OB and PLC still showed exclusive coupling of RR with γ2 and no theta-gamma coupling, whereas PAC and CA1 switched to selective coupling of theta with 40- to 80-Hz (γ1) and 120- to 160-Hz (γ3) gamma subbands. Our data illustrate a strong, specific interaction between neuronal activity patterns and respiration. Moreover, our results suggest that the coupling between slow and fast oscillations is a general brain mechanism not limited to the theta rhythm.
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Silva, Loreine Hermida da Silva e., Siglia Andressa Pinto Monteiro do Nascimento Alves, Fernanda Campante Magina, Sinda Beatriz Vianna Carvalhal Gomes, Ricardo Da Silva Cardoso, Carlos Henrique Soares Caetano i Alcides Wagner Serpa Guarino. "Cianobactérias Psâmicas Marinhas da Praia das Flexeiras, Estado do Rio de Janeiro, Sudeste do Brasil". Anuário do Instituto de Geociências 34, nr 1 (1.01.2011): 46–51. http://dx.doi.org/10.11137/2011_1_46-51.
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Flexeiras beach (22º56' S, 43º53'W) is located at Ilha de Itacuruçá (Itacuruçá Island) in Sepetiba Bay, on the southern coast of Rio de Janeiro State. It is a protected beach in relation to wave exposition, due to its geographic position, which faces the opening Bay. This work aims at contributing with the knowledge of abundance of psamic cyanobacteria species, which compound Brazilian sea-communities. It had occurred monthly collections, from December 2006 to January 2008, during syzygy's low tide. Samples were obtained through PVC pipes, measuring 1,5 cm of internal diameter and 6 cm length. They were also fractionated into 3 segments, 2 cm distant. After that, samples had been places in opaque plastic flasks referring to each segment and preserved in a 4% formol aqueous solution. Flexeiras beach has sediments made by sand, presenting grain size varying from 0,22 to 0,32 mm (fine sand). Estimated average declivity was of 1/21,4m (À 4,07) and 1/28,7m (À 15,8), respectively, for two transects. The water chlorophyll concentration in interdital areas presented an average of 3,03 g/L (À2,29) and total Phosphorus presented an average of 0,12 mg/L (À 0,04). Average salinity was of 35%, don't having considerable oscillations during the months studied. The qualitative analysis has detected the presence of 12 psamic cyanobacteria tax. Family Chroococcaceae Nägeli 1849 is the most frequent, responsible for 33,4% of encountered species. The geological importance of psamic cyanobacteria is intrinsically associated to the fact of them composing the first unconsolidated substract for microbial mats' formation, essential structures in this group preservation.
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Crespo-Garcia, Maite, Diego Pinal, Jose L. Cantero, Fernando Díaz, Montserrat Zurrón i Mercedes Atienza. "Working Memory Processes Are Mediated by Local and Long-range Synchronization of Alpha Oscillations". Journal of Cognitive Neuroscience 25, nr 8 (sierpień 2013): 1343–57. http://dx.doi.org/10.1162/jocn_a_00379.
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Different cortical dynamics of alpha oscillations (8–13 Hz) have been associated with increased working memory load, which have been mostly interpreted as a neural correlate of functional inhibition. This study aims at determining whether different manifestations of load-dependent amplitude and phase dynamics in the alpha band can coexist over different cortical regions. To address this question, we increased information load by manipulating the number and spatial configuration of domino spots. Time–frequency analysis of EEG source activity revealed (i) load-independent increases of both alpha power and interregional alpha-phase synchrony within task-irrelevant, posterior cortical regions and (ii) load-dependent decreases of alpha power over areas of the left pFC and bilateral posterior parietal cortex (PPC) preceded in time by load-dependent decreases of alpha-phase synchrony between the left pFC and the left PPC. The former results support the role of alpha oscillations in inhibiting irrelevant sensorimotor processing, whereas the latter likely reflect release of parietal task-relevant areas from top–down inhibition with load increase. This interpretation found further support in a significant latency shift of 15 msec from pFC to the PPC. Together, these results suggest that amplitude and phase alpha dynamics in both local and long-range cortical networks reflect different neural mechanisms of top–down control that might be crucial in mediating the different working memory processes.
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Raju, V. Rama. "β-oscillations linked by neuronal-spiking within the STN neurons via deep brain stimulation (DBS) in parkinson disease: Part – II". IP Indian Journal of Neurosciences 8, nr 3 (15.09.2022): 179–83. http://dx.doi.org/10.18231/j.ijn.2022.045.
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In the microelectrode recording and in the macrostimulations through DBS leads, the coupling was highest on the abaxial, i.e., dorsal- sub thalamic nucleus frontier-edge. The results proved that the larger β-high frequency oscillations and phase angle coupling is within the vicinity macro-leads contact which were clinically useful evaluated by continuing un effective-contacts, implying that PAC could prognostic of retort to STN-DBS. Neural-spiking was confined to the shape of 7Hz–30Hz oscillations(/fluctuations in the membranes), then longitudinal topography of spike-shape locking (S.S.L.)/ or spike-phase-locking(SPL) was analogous to PAC. Differences of phase amplitude coupling plus SPL indicated a lack—of spatio-temporal-correlations. β-coupled H.F.O.s and electrical-field protected (locked/fused) neurons have got unique and ideal phase-angles, i.e., signal/waveform-shapes above (+Ve) x-axis coordinates and below (-Ve) axis coordinates 2D spatio-temporal regions, did not occurred in the similar phase of modulating-oscillation. Therefore, our findings help which β – H.F.O—PAC could be key to patho physiology of Parkinson disease which suggests— locally electrical field-locked neurons are inadequate alone for the appearance of high frequency β-coupled oscillations.
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WANG, Zhexu, Rei KAWASHIMA i Kimiya KOMURASAKI. "A fast convergence fourth-order Vlasov model for Hall thruster ionization oscillation analyses". Plasma Science and Technology 24, nr 2 (22.12.2021): 025502. http://dx.doi.org/10.1088/2058-6272/ac3970.
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Abstract A 1D1V hybrid Vlasov-fluid model was developed for this study to elucidate discharge current oscillations of Hall thrusters (HTs). The Vlasov equation for ions velocity distribution function with ionization source term is solved using a constrained interpolation profile conservative semi-Lagrangian method. The fourth-order weighted essentially non-oscillatory (4th WENO) limiter is applied to the first derivative value to minimize numerical oscillation in the discharge oscillation analyses. The fourth-order accuracy is verified through a 1D scalar test case. Nonoscillatory and high-resolution features of the Vlasov model are confirmed by simulating the test cases of the Vlasov–Poisson system and by comparing the results with a particle-in-cell (PIC) method. A 1D1V HT simulation is performed through the hybrid Vlasov model. The ionization oscillation is analyzed. The oscillation amplitude and plasma density are compared with those obtained from a hybrid PIC method. The comparison indicates that the hybrid Vlasov-fluid model yields noiseless results and that the steady-state waveform is calculable in a short time period.
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Raju, V. Rama. "β-oscillations linked by neuronal-spiking in the STN via DBS of parkinson disease: Part – I". IP Indian Journal of Neurosciences 8, nr 3 (15.09.2022): 167–71. http://dx.doi.org/10.18231/j.ijn.2022.035.
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Typical head-worn brain surface (wired or wireless) EEG electrodes beta (β) band frequencies are amongst 13Hz to 30Hz. However, in the Parkinson`s the high beata frequency is between 20 Hz to 30 Hz. Atypical β-oscillations in BG were linked in the field of Patho physiology of Parkinson disease. 13Hz-30Hz β-oscillations into STN of Parkinson subjects has been verified to distress the spatio-temporal dynamics of high-frequency oscillations (HFOs) typically ranging from 200Hz–500Hz coupled with individual (single) neurons, probably and so hypothetically cooperating the functional litheness (or suppleness) of the motor-circuit. This study experimented the connections through concurrently gathering the field-potentials (i.e.,LFPs) plus single-unit-activity(SUA) from the parallelly connected basal-ganglion circuitry of 15 subjects (PD-patients) in deep-brain-stimulation(DBS) surgical-procedure of bilateral-STN. Stimulus phase-amplitude coupling (PAC) around nuclei was limited to β-phase plus HFO stimulus-amplitude. Coupling was greatest on the abaxial, i.e., dorsal- STN frontier-edge. Findings showed that greater β-HFO-PAC in close proximity (within the vicinity) macro-leads contact which were clinically useful evaluated by continuing un effective-contacts, implying that PAC could prognostic of retort to STN-DBS. Neural-spiking was confined to the shape of 7Hz–30Hz oscillations (/fluctuations in the membranes), then longitudinal-topo-graphy of spike-shape-locking(SSL)/ or spike-phase-locking(SPL) was analogous to PAC. Differences of PAC plus SSL/(SPL) indicated a lack—of spatio-temporal-correlations. β-coupled H.F.O.s and electrical-field protected (locked/fused) neurons have got unique and ideal phase-angles, i.e., signal/waveform-shapes above(+) x-axis and below (-) axis 2D spatio-temporal regions, didn`t transpired in the similar phase of modulating-oscillation. Hence, results yield further help which β-HFO-P.A.C might be key to pathos physiology of Parkinson which advises local electrical field-locked neurons are inadequate alone for the appearance of high frequency β-coupled oscillations.
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Ponzi, Adam, Salvador Dura-Bernal i Michele Migliore. "Theta-gamma phase amplitude coupling in a hippocampal CA1 microcircuit". PLOS Computational Biology 19, nr 3 (23.03.2023): e1010942. http://dx.doi.org/10.1371/journal.pcbi.1010942.
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Phase amplitude coupling (PAC) between slow and fast oscillations is found throughout the brain and plays important functional roles. Its neural origin remains unclear. Experimental findings are often puzzling and sometimes contradictory. Most computational models rely on pairs of pacemaker neurons or neural populations tuned at different frequencies to produce PAC. Here, using a data-driven model of a hippocampal microcircuit, we demonstrate that PAC can naturally emerge from a single feedback mechanism involving an inhibitory and excitatory neuron population, which interplay to generate theta frequency periodic bursts of higher frequency gamma. The model suggests the conditions under which a CA1 microcircuit can operate to elicit theta-gamma PAC, and highlights the modulatory role of OLM and PVBC cells, recurrent connectivity, and short term synaptic plasticity. Surprisingly, the results suggest the experimentally testable prediction that the generation of the slow population oscillation requires the fast one and cannot occur without it.
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Hyafil, Alexandre. "Disharmony in neural oscillations". Journal of Neurophysiology 118, nr 1 (1.07.2017): 1–3. http://dx.doi.org/10.1152/jn.00026.2017.
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Cross-frequency phase coupling (PPC) may play an important role in neural processing and cognition. However, a new study unveils a statistical bias in how PPC is detected in neural recordings, questions prior evidence for PPC in hippocampus, and shows PPC tests are dramatically flawed by their confounds with oscillation harmonics.
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Nuwal, Nakul, Toyofumi Yamauchi, Animesh Sharma, Deborah A. Levin i Joshua L. Rovey. "Kinetic modeling and experiments of a pulsed-bias plasma in a multipole plasma chamber". Physics of Plasmas 29, nr 11 (listopad 2022): 112105. http://dx.doi.org/10.1063/5.0126692.
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A pulse of electron timescale applied to a planar electrode immersed in a homogeneous plasma in a multipole plasma chamber (MPC) is modeled using a fully kinetic particle-in-cell (PIC) approach. In the time-explicit PIC simulations, we observed that the ion-sheath expansion is accompanied by electron timescale harmonic plasma oscillations at the sheath edge that decay after applying the pulse. First, we validate our PIC approach by comparing it with previous analytical and semi-empirical sheath expansion studies. Then, we compare our PIC results with experiments conducted in the MPC where similar electron frequency oscillations were excited when an electron timescale pulse was applied to a flat-conductor plate. In both PIC simulations and experiments, we find that the shape of the applied pulse dictates the amplitude of the sheath edge oscillations. In the PIC simulations, we observe that Landau damping has no discernible effect on these oscillations. However, in the experiments, the presence of a hot electron population results in a higher damping of electron oscillations. In both PIC simulations and experiments, the amplitude of the electron frequency oscillations decreases with the applied pulse width and these oscillations disappear for a linear pulse of a longer timescale of [Formula: see text] ([Formula: see text]), in the PIC simulations.
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Cowin, Stephen C., Gaffar Gailani i Mohammed Benalla. "Hierarchical poroelasticity: movement of interstitial fluid between porosity levels in bones". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 367, nr 1902 (13.09.2009): 3401–44. http://dx.doi.org/10.1098/rsta.2009.0099.
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The governing equations for the theory of poroelastic materials with hierarchical pore space architecture and compressible constituents undergoing small deformations are developed. These equations are applied to the problem of determining the exchange of pore fluid between the vascular porosity (PV) and the lacunar–canalicular porosity (PLC) in bone tissue due to cyclic mechanical loading and blood pressure oscillations. The result is basic to the understanding of interstitial flow in bone tissue that, in turn, is basic to understanding of nutrient transport from the vasculature to the bone cells buried in the bone tissue and to the process of mechanotransduction by these cells. A formula for the volume of fluid that moves between the PLC and PV in a cyclic loading is obtained as a function of the cyclic mechanical loading and blood pressure oscillations. Formulas for the oscillating fluid pore pressure in both the PLC and the PV are obtained as functions of the two driving forces, the cyclic mechanical straining and the blood pressure, both with specified amplitude and frequency. The results of this study also suggest a PV permeability greater than 10 −9 m 2 and perhaps a little lower than 10 −8 m 2 . Previous estimates of this permeability have been as small as 10 −14 m 2 .
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Chen, Chen, Hongyao Tang, Jianye Hao, Wulong Liu i Zhaopeng Meng. "Addressing Action Oscillations through Learning Policy Inertia". Proceedings of the AAAI Conference on Artificial Intelligence 35, nr 8 (18.05.2021): 7020–27. http://dx.doi.org/10.1609/aaai.v35i8.16864.
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Deep reinforcement learning (DRL) algorithms have been demonstrated to be effective on a wide range of challenging decision making and control tasks. However, these methods typically suffer from severe action oscillations in particular in discrete action setting, which means that agents select different actions within consecutive steps even though states only slightly differ. This issue is often neglected since we usually evaluate the quality of a policy using cumulative rewards only. Action oscillation strongly affects the user experience and even causes serious potential security menace especially in real-world domains with the main concern of safety, such as autonomous driving. In this paper, we introduce Policy Inertia Controller (PIC) which serves as a generic plug-in framework to off-the-shelf DRL algorithms, to enable adaptive balance between the optimality and smoothness in a formal way. We propose Nested Policy Iteration as a general training algorithm for PIC-augmented policy which ensures monotonically non-decreasing updates.Further, we derive a practical DRL algorithm, namely Nested Soft Actor-Critic. Experiments on a collection of autonomous driving tasks and several Atari games suggest that our approach demonstrates substantial oscillation reduction than a range of commonly adopted baselines with almost no performance degradation.
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Alathamneh, Mohammad, Haneen Ghanayem, Xingyu Yang i R. M. Nelms. "Three-Phase Grid-Connected Inverter Power Control under Unbalanced Grid Conditions Using a Proportional-Resonant Control Method". Energies 15, nr 19 (26.09.2022): 7051. http://dx.doi.org/10.3390/en15197051.
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Proposed in this article is bidirectional real and reactive power control of a three-phase grid-connected inverter under unbalanced grid conditions using a proportional-resonance controller. Different unbalanced grid conditions have been studied, such as unbalanced three-phase load and unbalanced grid impedance. These unbalanced scenarios generate unbalanced grid currents and unbalanced point-of-common-coupling (PCC) voltages, causing large oscillations in both real and reactive power transferred to the grid. The purposes of the suggested technique are to balance the grid currents and point-of-common-coupling voltages as well as control the power injected into the grid. As a result, balanced PCC voltages are guaranteed, the oscillation in real and reactive power is reduced, and power control is achieved. The proposed method’s performance has been verified in MATLAB/SIMULINK simulation software, and different experimental results have been obtained using a real-time interface platform, dSPACE DS1202.
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Ott, Torben, Stephanie Westendorff i Andreas Nieder. "Dopamine Receptors Influence Internally Generated Oscillations during Rule Processing in Primate Prefrontal Cortex". Journal of Cognitive Neuroscience 30, nr 5 (maj 2018): 770–84. http://dx.doi.org/10.1162/jocn_a_01248.
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Neural oscillations in distinct frequency bands in the prefrontal cortex (pFC) are associated with specialized roles during cognitive control. How dopamine modulates oscillations to structure pFC functions remains unknown. We trained macaques to switch between two numerical rules and recorded local field potentials from pFC while applying dopamine receptor targeting drugs using microiontophoresis. We show that the D1 and D2 family receptors (D1Rs and D2Rs, respectively) specifically altered internally generated prefrontal oscillations, whereas sensory-evoked potentials remained unchanged. Blocking D1Rs or stimulating D2Rs increased low-frequency theta and alpha oscillations known to be involved in learning and memory. In contrast, only D1R inhibition enhanced high-frequency beta oscillations, whereas only D2R stimulation increased gamma oscillations linked to top–down and bottom–up attentional processing. These findings suggest that dopamine alters neural oscillations relevant for executive functioning through dissociable actions at the receptor level.
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Tai, Chen-Jei, Sung Keun Kang i Peter C. K. Leung. "Adenosine Triphosphate-Evoked Cytosolic Calcium Oscillations in Human Granulosa-Luteal Cells: Role of Protein Kinase C1". Journal of Clinical Endocrinology & Metabolism 86, nr 2 (1.02.2001): 773–77. http://dx.doi.org/10.1210/jcem.86.2.7231.
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ATP has been shown to modulate progesterone production in human granulosa-luteal cells (hGLCs) in vitro. After binding to a G protein-coupled P2 purinergic receptor, ATP stimulates phospholipase C. The resultant production of diacylglycerol and inositol triphosphate activates protein kinase C (PKC) and intracellular calcium [Ca2+]i mobilization, respectively. In the present study, we examined the potential cross-talk between the PKC and Ca2+ pathway in ATP signal transduction. Specifically, the effect of PKC on regulating ATP-evoked[ Ca2+]i oscillations were examined in hGLCs. Using microspectrofluorimetry, [Ca2+]i oscillations were detected in Fura-2 loaded hGLCs in primary culture. The amplitudes of the ATP-triggered [Ca2+]i oscillations were reduced in a dose-dependent manner by pretreating the cells with various concentrations (1 nm to 10μ m) of the PKC activator, phorbol-12-myristate-13-acetate (PMA). A 10 μm concentration of PMA completely suppressed 10 μm ATP-induced oscillations. The inhibitory effect occurred even when PMA was given during the plateau phase of ATP evoked [Ca2+]i oscillations, suggesting that extracellular calcium influx was inhibited. The role of PKC was further substantiated by the observation that, in the presence of a PKC inhibitor, bisindolylmaleimide I, ATP-induced[ Ca2+]i oscillations were not completely suppressed by PMA. Furthermore, homologous desensitization of ATP-induced calcium oscillations was partially reversed by bisindolylmaleimide I, suggesting that activated PKC may be involved in the mechanism of desensitization. These results demonstrate that PKC negatively regulates the ATP-evoked [Ca2+]i mobilization from both intracellular stores and extracellular influx in hGLCs and further support a modulatory role of ATP and P2 purinoceptor in ovarian steroidogenesis.
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Morley, Paul, Balu R. Chakravarthy, Geoffrey AR Mealing, Benjamin K. Tsang i James F. Whitfield. "Role of protein kinase C in the regulation of ATP-triggered intracellular Ca2+ oscillations in chicken granulosa cells". European Journal of Endocrinology 134, nr 6 (czerwiec 1996): 743–50. http://dx.doi.org/10.1530/eje.0.1340743.
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Morley P. Chakravarthy BR, Mealing GAR, Tsang BK, Whitfield JF. Role of protein kinase C in the regulation of ATP-triggered intracellular Ca2+ oscillations in chicken granulosa cells. Eur J Endocrinol 1996;134:743–50. ISSN 0804–4643 These studies were designed to investigate the role of protein kinase C (PKC) in the regulation of ATP-triggered intracellular Ca2+ ([Ca2+]i) oscillations in chicken granulosa cells. Granulosa cells were obtained from the two largest preovulatory follicles (F1 and F2) of hens and [Ca2+]i was measured in cells loaded with the Ca2+-responsive fluorescent dye fura-2. Adenosine triphosphate (100 μmol/l) triggered an immediate, large [Ca2+]i spike that was followed by oscillations that returned to the resting level between spikes. The ATP (100 μmol/l) also stimulated a 1.70 ± 0.1-fold increase in membrane-associated PKC activity over control levels. The frequency of the ATP-triggered [Ca2+]i oscillations was reduced in a concentration-dependent (1–10 nmol/l) manner by treating the cells for 2 min with a PKC activator, 12-O-tetradecanoyl phorbol-13-acetate (TPA). A higher TPA concentration (100 nmol/l) completely prevented ATP from triggering the initial [Ca2+]i spike and oscillations. Adding TPA during the ATP-triggered [Ca2+]i oscillations immediately stopped the oscillatory activity. Interestingly, PKC inhibitors failed to amplify the ATP-triggered [Ca2+]i oscillations. Instead, adding the PKC inhibitors staurosporine (20 nmol/l), calphostin C (200 nmol/l) or 1-(5-isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride (H7; 100 μmol/l), either before or during the ATP (100μmol/l)-triggered [Ca2+]i response, also completely blocked the [Ca2+]i oscillations. Therefore, ATP-triggered [Ca2+]i oscillations in chicken granulosa cells appear to be regulated by a negative feedback loop requiring PKC, because the [Ca2+]i oscillations were prevented by either full activation or inhibition of PKC activity. Paul Morley, Institute for Biological Sciences, National Research Council of Canada, Building M54, Montreal Road, Ottawa, Ontario, K1A OR6, Canada
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Gretenkord, Sabine, Adrian Rees, Miles A. Whittington, Sarah E. Gartside i Fiona E. N. LeBeau. "Dorsal vs. ventral differences in fast Up-state-associated oscillations in the medial prefrontal cortex of the urethane-anesthetized rat". Journal of Neurophysiology 117, nr 3 (1.03.2017): 1126–42. http://dx.doi.org/10.1152/jn.00762.2016.
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Cortical slow oscillations (0.1–1 Hz), which may play a role in memory consolidation, are a hallmark of non-rapid eye movement (NREM) sleep and also occur under anesthesia. During slow oscillations the neuronal network generates faster oscillations on the active Up-states and these nested oscillations are particularly prominent in the PFC. In rodents the medial prefrontal cortex (mPFC) consists of several subregions: anterior cingulate cortex (ACC), prelimbic (PrL), infralimbic (IL), and dorsal peduncular cortices (DP). Although each region has a distinct anatomy and function, it is not known whether slow or fast network oscillations differ between subregions in vivo. We have simultaneously recorded slow and fast network oscillations in all four subregions of the rodent mPFC under urethane anesthesia. Slow oscillations were synchronous between the mPFC subregions, and across the hemispheres, with no consistent amplitude difference between subregions. Delta (2–4 Hz) activity showed only small differences between subregions. However, oscillations in the spindle (6–15 Hz)-, beta (20–30 Hz), gamma (30–80 Hz)-, and high-gamma (80–150 Hz)-frequency bands were consistently larger in the dorsal regions (ACC and PrL) compared with ventral regions (IL and DP). In dorsal regions the peak power of spindle, beta, and gamma activity occurred early after onset of the Up-state. In the ventral regions, especially the DP, the oscillatory power in the spindle-, beta-, and gamma-frequency ranges peaked later in the Up-state. These results suggest variations in fast network oscillations within the mPFC that may reflect the different functions and connectivity of these subregions. NEW & NOTEWORTHY We demonstrate, in the urethane-anesthetized rat, that within the medial prefrontal cortex (mPFC) there are clear subregional differences in the fast network oscillations associated with the slow oscillation Up-state. These differences, particularly between the dorsal and ventral subregions of the mPFC, may reflect the different functions and connectivity of these subregions.
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Mello, Carlos Rogério de, Lloyd Darrell Norton, Nilton Curi i Silvia Nazaré Monteiro Yanagi. "Sea surface temperature (SST) and rainfall erosivity in the Upper Grande River Basin, southeast Brazil". Ciência e Agrotecnologia 36, nr 1 (luty 2012): 53–59. http://dx.doi.org/10.1590/s1413-70542012000100007.
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Relationships between regional climates and oceanic and atmospheric anomalies are important in understanding the rainfall regime of a given region. This work aimed to analyze rainfall erosivity in the Upper Grande River Basin, Southern Minas Gerais State, Brazil; namely the two most representative environments, the Mantiqueira Range (MR) and the Plateau of Campos das Vertentes (PCV). These areas can be affected by the El Niño Southern Oscillation (ENSO) phenomena, which can be evaluated by indicators such as Sea Surface Temperature (SST) for the Niño 3.4 Region. Rainfall erosivity was calculated for individual rainfall events from January, 2006 to December, 2010. Pearson's coefficient of correlation was used to evaluate the relationships between rainfall variables and SST. The coefficients of correlation were significant for both sub-regions. Correlations between the rainfall variables and negative oscillations of SST were also significant, especially in the MR sub-region, however, the Person's coefficients were lower than those obtained for the SST positive oscillations. These results demonstrate that El-Niño phenomenon can be considered an important factor in the intense rainfall behavior of the Upper Grande River Basin.
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Yan, Tianfang, Katsuyoshi Suzuki, Seiji Kameda, Masashi Maeda, Takuma Mihara i Masayuki Hirata. "Electrocorticographic effects of acute ketamine on non-human primate brains". Journal of Neural Engineering 19, nr 2 (1.04.2022): 026034. http://dx.doi.org/10.1088/1741-2552/ac6293.
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Abstract Objective. Acute blockade of glutamate N-methyl-D-aspartate receptors by ketamine induces symptoms and electrophysiological changes similar to schizophrenia. Previous studies have shown that ketamine elicits aberrant gamma oscillations in several cortical areas and impairs coupling strength between the low-frequency phase and fast frequency amplitude, which plays an important role in integrating functional information. Approach. This study utilized a customized wireless electrocorticography (ECoG) recording device to collect subdural signals from the somatosensory and primary auditory cortices in two monkeys. Ketamine was administered at a dose of 3 mg kg−1 (intramuscular) or 0.56 mg kg−1 (intravenous) to elicit brain oscillation reactions. We analyzed the raw data using methods such as power spectral density, time-frequency spectra, and phase-amplitude coupling (PAC). Main results. Acute ketamine triggered broadband gamma and high gamma oscillation power and decreased lower frequencies. The effect was stronger in the primary auditory cortex than in the somatosensory area. The coupling strength between the low phase of theta and the faster amplitude of gamma/high gamma bands was increased by a lower dose (0.56 mg kg−1 iv) and decreased with a higher dose (3 mg kg−1 im) ketamine. Significance. Our results showed that lower and higher doses of ketamine elicited differential effects on theta-gamma PAC. These findings support the utility of ECoG models as a translational platform for pharmacodynamic research in future research.
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Young, Steven H., Osvaldo Rey, James Sinnett-Smith i Enrique Rozengurt. "Intracellular Ca2+ oscillations generated via the Ca2+-sensing receptor are mediated by negative feedback by PKCα at Thr888". American Journal of Physiology-Cell Physiology 306, nr 3 (1.02.2014): C298—C306. http://dx.doi.org/10.1152/ajpcell.00194.2013.
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To clarify the mechanism(s) underlying intracellular Ca2+ concentration ([Ca2+]i) oscillations induced by an elevation in extracellular Ca2+ concentration ([Ca2+]e) via the extracellular Ca2+-sensing receptor (CaR), we analyzed the pattern of [Ca2+]i response in multiple (2,303) individual HEK-293 cells transfected with the human CaR. An increase in the [Ca2+]e from 1.5 to 3 mM produced oscillatory fluctuations in [Ca2+]i in 70% of the cell population. To determine the role of PKC in the generation of [Ca2+]i oscillations, cells were exposed to increasing concentrations (0.5–5 μM) of the preferential PKC inhibitor Ro-31-8220 before stimulation by extracellular Ca2+. Ro-31-8220 at 3–5 μM completely eliminated the [Ca2+]e-evoked [Ca2+]i oscillations and transformed the pattern to a peak and sustained plateau response. Treatment with other broad PKC inhibitors, including GFI or Gö6983, produced an identical response. Similarly, treatment with Ro-31-8220 or GFI eliminated [Ca2+]e-evoked [Ca2+]i oscillations in colon-derived SW-480 cells expressing the CaR. Treatment with inhibitors targeting classic PKCs, including Gö6976 and Ro-32-0432 as well as small interfering RNA-mediated knockdown of PKCα, strikingly reduced the proportion of cell displaying [Ca2+]e-evoked [Ca2+]i oscillations. Furthermore, none of the cells analyzed expressing a CaR mutant in which the major PKC phosphorylation site Thr888 was converted to alanine (CaRT888A) showed [Ca2+]i oscillations after CaR activation. Our results show that [Ca2+]i oscillations induced by activation of the CaR in response to an increase in extracellular Ca2+ or exposure to the calcimimetic R-568 result from negative feedback involving PKCα-mediated phosphorylation of the CaR at Thr888.
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Thörn, Carolina Wilnerzon, Vasilios Kafetzopoulos i Bernat Kocsis. "Differential Effect of Dopamine D4 Receptor Activation on Low-Frequency Oscillations in the Prefrontal Cortex and Hippocampus May Bias the Bidirectional Prefrontal–Hippocampal Coupling". International Journal of Molecular Sciences 23, nr 19 (3.10.2022): 11705. http://dx.doi.org/10.3390/ijms231911705.
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Dopamine D4 receptor (D4R) mechanisms are implicated in psychiatric diseases characterized by cognitive deficits, including schizophrenia, ADHD, and autism. The cellular mechanisms are poorly understood, but impaired neuronal synchronization in cortical networks was proposed to contribute to these deficits. In animal experiments, D4R activation was shown to generate aberrant increased gamma oscillations and to reduce performance on cognitive tasks requiring functional prefrontal cortex (PFC) and hippocampus (HPC) networks. While fast oscillations in the gamma range are important for local synchronization within neuronal ensembles, long-range synchronization between distant structures is achieved by slow rhythms in the delta, theta, alpha ranges. The characteristics of slow oscillations vary between structures during cognitive tasks. HPC activity is dominated by theta rhythm, whereas PFC generates unique oscillations in the 2–4 Hz range. In order to investigate the role of D4R on slow rhythms, cortical activity was recorded in rats under urethane anesthesia in which slow oscillations can be elicited in a controlled manner without behavioral confounds, by electrical stimulation of the brainstem reticular formation. The local field potential segments during stimulations were extracted and subjected to fast Fourier transform to obtain power density spectra. The selective D4R agonist A-412997 (5 and 10 mg/kg) and antagonists L-745870 (5 and 10 mg/kg) were injected systemically and the peak power in the two frequency ranges were compared before and after the injection. We found that D4R compounds significantly changed the activity of both HPC and PFC, but the direction of the effect was opposite in the two structures. D4R agonist enhanced PFC slow rhythm (delta, 2–4 Hz) and suppressed HPC theta, whereas the antagonist had an opposite effect. Analogous changes of the two slow rhythms were also found in the thalamic nucleus reuniens, which has connections to both forebrain structures. Slow oscillations play a key role in interregional cortical coupling; delta and theta oscillations were shown in particular, to entrain neuronal firing and to modulate gamma activity in interconnected forebrain structures with a relative HPC theta dominance over PFC. Thus, the results of this study indicate that D4R activation may introduce an abnormal bias in the bidirectional PFC–HPC coupling which can be reversed by D4R antagonists.
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JONES, Keith T., Miho MATSUDA, John PARRINGTON, Matilda KATAN i Karl SWANN. "Different Ca2+-releasing abilities of sperm extracts compared with tissue extracts and phospholipase C isoforms in sea urchin egg homogenate and mouse eggs". Biochemical Journal 346, nr 3 (7.03.2000): 743–49. http://dx.doi.org/10.1042/bj3460743.
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A soluble phospholipase C (PLC) from boar sperm generates InsP3 and hence causes Ca2+ release when added to sea urchin egg homogenate. This PLC activity is associated with the ability of sperm extracts to cause Ca2+ oscillations in mammalian eggs following fractionation. A sperm PLC may, therefore, be responsible for causing the observed Ca2+ oscillations at fertilization. In the present study we have further characterized this boar sperm PLC activity using sea urchin egg homogenate. Consistent with a sperm PLC acting on egg PtdIns(4,5)P2, the ability of sperm extracts to release Ca2+ was blocked by preincubation with the PLC inhibitor U73122 or by the addition of neomycin to the homogenate. The Ca2+-releasing activity was also detectable in sperm from other species and in whole testis extracts. However, activity was not observed in extracts from other tissues. Moreover recombinant PLCβ1, -γ1, -γ2, -∆1, all of which had higher specific activities than boar sperm extracts, were not able to release Ca2+ in the sea urchin egg homogenate. In addition these PLCs were not able to cause Ca2+ oscillations following microinjection into mouse eggs. These results imply that the sperm PLC possesses distinct properties that allow it to hydrolyse PtdIns(4,5)P2 in eggs.
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Nomikos, Michail. "Novel signalling mechanism and clinical applications of sperm-specific PLCζ". Biochemical Society Transactions 43, nr 3 (1.06.2015): 371–76. http://dx.doi.org/10.1042/bst20140291.
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Egg activation is the first step of embryonic development and in mammals is triggered by a series of cytoplasmic calcium (Ca2+) oscillations. Sperm–egg fusion initiates these Ca2+ oscillations by introducing a sperm-specific protein factor into the egg cytoplasm. Substantial evidence indicates that this protein is a sperm-specific phospholipase C (PLC), termed PLC-zeta (PLCζ). PLCζ stimulates cytoplasmic Ca2+ oscillations matching those at fertilization triggering early embryonic development in several mammalian species. Structurally, PLCζ is comprised of four EF-hands, a C2 domain, and X and Y catalytic domains. PLCζ is an unusual PLC since it lacks a pleckstrin homology (PH) domain. It is also distinctive in that its X–Y linker is not involved in auto-inhibition of catalytic activity, but instead binds to phosphatidylinositol 4,5-bisphosphate (PIP2). Moreover, relative to other PLC isoforms, PLCζ possesses unique potency in stimulating Ca2+ oscillations in eggs, although it does not appear to bind to plasma membrane PIP2. In contrast, PLCζ appears to interact with intracellular vesicles in eggs that contain PIP2. I discuss the recent advances in our knowledge of the intriguing biochemical and physiological properties of sperm PLCζ and postulate potential roles for PLCζ in terms of clinical diagnosis and therapy for certain forms of male infertility.
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Liu, Lei, Ling Guo Zhang i Zhe Hu. "Emergency Response Technology Using Powdered Activated Carbon for Sudden Water Pollution Accidents with Petroleum Pollutants". Advanced Materials Research 955-959 (czerwiec 2014): 2517–20. http://dx.doi.org/10.4028/www.scientific.net/amr.955-959.2517.
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Emergency disposal combined technology of sorbent cotton intercept and powdered activated carbon (PAC) adsorption was researched. The removal effects of petroleum pollutants individually treated by sorbent cotton were analyzed. The influencing factors of PAC adsorption to deal with petroleum pollutants, including PAC dosage, oscillation frequency and oscillation time, were investigated. The results showed that removal efficiency increased with increasing PAC dosage. When PAC dosage reached 50mg/L, the remaining concentration of petroleum pollutants met the standards. And after oscillated for 120min, the total removal efficiency increased to more than 99%.
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PARRINGTON, John, Keith T. JONES, F. Anthony LAI i Karl SWANN. "The soluble sperm factor that causes Ca2+ release from sea-urchin (Lytechinus pictus) egg homogenates also triggers Ca2+ oscillations after injection into mouse eggs". Biochemical Journal 341, nr 1 (24.06.1999): 1–4. http://dx.doi.org/10.1042/bj3410001.
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Cytosolic extracts of boar sperm contain a soluble phospholipase C (PLC) activity that induces Ca2+ release in sea-urchin (Lytechinus pictus) egg homogenates and an uncharacterized protein factor that causes Ca2+ oscillations when injected into mammalian eggs. In the present study we fractionated boar sperm extracts on three different FPLC chromatographic columns and found that the fractions that caused maximal Ca2+ release in sea-urchin egg homogenates were also the ones that triggered Ca2+ oscillations in mouse eggs. Our data suggests that the sperm factor which triggers Ca2+ oscillations in eggs contains a PLC and not the 33 kDa glucosamine deaminase previously suggested to be one its components.
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Izah, Rofiatul, Subiyanto Subiyanto i Dhidik Prastiyanto. "Improvement of DSOGI PLL Synchronization Algorithm with Filter on Three-Phase Grid-connected Photovoltaic System". Jurnal Elektronika dan Telekomunikasi 18, nr 1 (31.08.2018): 35. http://dx.doi.org/10.14203/jet.v18.35-45.
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Synchronous Reference Frame Phase Locked Loop (SRF PLL) has been widely used for synchronization three-phase grid-connected photovoltaic (PV) system. On the grid fault, SRF PLL distorted by negative sequence component and grid harmonic that caused an error in estimating parameter because of ripple and oscillation. This work combined SRF PLL with Dual Second Order Generalized Integrator (DSOGI) and filter to minimize ripple and minimize oscillation in the phase estimation and frequency estimation. DSOGI was used for filtering and obtaining the 90o shifted versions from the vαβ signals. These signals (vαβ) were generated from three phase grid voltage signal using Clarke transform. The vαβ signal was the inputs to the positive-sequence calculator (PSC). The positive-sequence vαβ was transformed to the dq synchronous reference frame and became an input to SRF-PLL to create the estimation frequency. This estimation frequency from SRF PLL was filtered by the low-pass filter to decrease grid harmonic. Moreover, the output of low-pass filter was a frequency adaptive. The performance of DSOGI PLL with filter is compared with DSOGI PLL, SRF PLL, and IEEE standard 1547(TM)-2003. The improvement of DSOGI PLL with filter gave better performances than DSOGI PLL and SRF PLLbecause it minimized ripples and oscillations in the phase and frequency estimations.
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Yoon, Sook-Young, i Rafael A. Fissore. "Release of phospholipase C ζand [Ca2+]i oscillation-inducing activity during mammalian fertilization". Reproduction 134, nr 5 (listopad 2007): 695–704. http://dx.doi.org/10.1530/rep-07-0259.
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During fertilization of mammalian eggs a factor from the sperm, the sperm factor (SF), is released into the ooplasm and induces persistent [Ca2+]i oscillations that are required for egg activation and embryo development. A sperm-specific phospholipase C (PLC), PLCz, is thought to be the SF. Here, we investigated whether the SF activity and PLCζare simultaneously and completely released into the ooplasm soon after sperm entry. To accomplish this, we enucleated sperm heads within 90 min of intracytoplasmic sperm injection (ICSI) and monitored the persistence of the [Ca2+]i oscillations in eggs in which the sperm had been withdrawn. We also stained the enucleatedsperm heads to ascertain the presence/absence of PLCζ. Our results show that by 90 min all the SF activity had been released from the sperm, as fertilized enucleated eggs oscillated as fertilized controls, even in cases in which oscillations were prolonged by arresting eggs at metaphase. In addition, we found that the released SF activity became associated with the pronucleus (PN), as induction of PN envelope breakdown evoked comparable [Ca2+]i responses in enucleated and non-manipulated zygotes. Lastly, we found that PLCzlocalized to the equatorial area of bull sperm and to the post-acrosomal region of mouse sperm and that by 90 min after ICSI all the sperm’s PLCζimmunoreactivity was lost in both species. Altogether, our findings show that during fertilization the SF activity and PLCζimmunoreactivity are simultaneously released from the sperm, suggesting that PLCζmay be the only [Ca2+]i oscillation-inducing factor of mammalian sperm.
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Hua, Chih-Chiang, i Yu-Jun Zhan. "A Hybrid Maximum Power Point Tracking Method without Oscillations in Steady-State for Photovoltaic Energy Systems". Energies 14, nr 18 (7.09.2021): 5590. http://dx.doi.org/10.3390/en14185590.
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This paper proposes a hybrid maximum power point tracking (MPPT) method with zero oscillation in steady-state by combining genetic algorithm (GA) and perturbation and observation (P&O) method. The proposed MPPT can track the global maximum power point (GMPP) fast for a photovoltaic (PV) system even under partial shaded conditions (PSC). The oscillations around the GMPP are eliminated and the power loss can be reduced significantly. In addition, the proposed MPPT can make the PV system operate at the highest efficiencies under various atmospheric conditions. During the MPP tracking, the system will oscillate around the MPPs, resulting in unnecessary power loss. To solve the problem, the artificial intelligence (AI) algorithms, such as PSO, Bee Colony optimization, GA, etc., were developed to deal with this issue. However, the problem with the AI algorithm is that the time for convergence may be too long if the range of the MPP search space is large. In addition, if the atmospheric conditions change fast, the PV system may operate at or close to the local maximum power points (LMPPs) for a long time. In this paper, a method combining the P&O’s fast tracking and GA’s GMPP tracking ability is proposed. The proposed system can stop the oscillations as soon as the GMPP is found, thus minimizing the power loss due to oscillations. The proposed MPPT can achieve superior performance while maintaining the simplicity of implementation. Finally, the simulation and experimental results are presented to demonstrate the feasibility of the proposed system.
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Nomikos, Michail, Junaid Kashir i F. Anthony Lai. "The role and mechanism of action of sperm PLC-zeta in mammalian fertilisation". Biochemical Journal 474, nr 21 (23.10.2017): 3659–73. http://dx.doi.org/10.1042/bcj20160521.
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At mammalian fertilisation, the fundamental stimulus that triggers oocyte (egg) activation and initiation of early embryonic development is an acute rise of the intracellular-free calcium (Ca2+) concentration inside the egg cytoplasm. This essential Ca2+ increase comprises a characteristic series of repetitive Ca2+ oscillations, starting soon after sperm–egg fusion. Over the last 15 years, accumulating scientific and clinical evidence supports the notion that the physiological stimulus that precedes the cytosolic Ca2+ oscillations is a novel, testis-specific phospholipase C (PLC) isoform, known as PLC-zeta (PLCζ). Sperm PLCζ catalyses the hydrolysis of phosphatidylinositol 4,5-bisphosphate triggering cytosolic Ca2+ oscillations through the inositol 1,4,5-trisphosphate signalling pathway. PLCζ is the smallest known mammalian PLC isoform with the most elementary domain organisation. However, relative to somatic PLCs, the PLCζ isoform possesses a unique potency in stimulating Ca2+ oscillations in eggs that is attributed to its novel biochemical characteristics. In this review, we discuss the latest developments that have begun to unravel the vital role of PLCζ at mammalian fertilisation and decipher its unique mechanism of action within the fertilising egg. We also postulate the significant potential diagnostic and therapeutic capacity of PLCζ in alleviating certain types of male infertility.
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Gruber, Matthias J., Liang-Tien Hsieh, Bernhard P. Staresina, Christian E. Elger, Juergen Fell, Nikolai Axmacher i Charan Ranganath. "Theta Phase Synchronization between the Human Hippocampus and Prefrontal Cortex Increases during Encoding of Unexpected Information: A Case Study". Journal of Cognitive Neuroscience 30, nr 11 (listopad 2018): 1646–56. http://dx.doi.org/10.1162/jocn_a_01302.
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Events that violate predictions are thought to not only modulate activity within the hippocampus and PFC but also enhance communication between the two regions. Scalp and intracranial EEG studies have shown that oscillations in the theta frequency band are enhanced during processing of contextually unexpected information. Some theories suggest that the hippocampus and PFC interact during processing of unexpected events, and it is possible that theta oscillations may mediate these interactions. Here, we had the rare opportunity to conduct simultaneous electrophysiological recordings from the human hippocampus and PFC from two patients undergoing presurgical evaluation for pharmacoresistant epilepsy. Recordings were conducted during a task that involved encoding of contextually expected and unexpected visual stimuli. Across both patients, hippocampal–prefrontal theta phase synchronization was significantly higher during encoding of contextually unexpected study items, relative to contextually expected study items. Furthermore, the hippocampal–prefrontal theta phase synchronization was larger for contextually unexpected items that were later remembered compared with later forgotten items. Moreover, we did not find increased theta synchronization between the PFC and rhinal cortex, suggesting that the observed effects were specific to prefrontal–hippocampal interactions. Our findings are consistent with the idea that theta oscillations orchestrate communication between the hippocampus and PFC in support of enhanced encoding of contextually deviant information.
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Kononowicz, Tadeusz W., Tilmann Sander, Hedderik Van Rijn i Virginie van Wassenhove. "Precision Timing with α–β Oscillatory Coupling: Stopwatch or Motor Control?" Journal of Cognitive Neuroscience 32, nr 9 (wrzesień 2020): 1624–36. http://dx.doi.org/10.1162/jocn_a_01570.
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Precise timing is crucial for many behaviors ranging from conversational speech to athletic performance. The precision of motor timing has been suggested to result from the strength of phase–amplitude coupling (PAC) between the phase of alpha oscillations (α, 8–12 Hz) and the power of beta activity (β, 14–30 Hz), herein referred to as α–β PAC. The amplitude of β oscillations has been proposed to code for temporally relevant information and the locking of β power to the phase of α oscillations to maintain timing precision. Motor timing precision has at least two sources of variability: variability of timekeeping mechanism and variability of motor control. It is ambiguous to which of these two factors α–β PAC should be ascribed: α–β PAC could index precision of stopwatch-like internal timekeeping mechanisms, or α–β PAC could index motor control precision. To disentangle these two hypotheses, we tested how oscillatory coupling at different stages of a time reproduction task related to temporal precision. Human participants encoded and subsequently reproduced a time interval while magnetoencephalography was recorded. The data show a robust α–β PAC during both the encoding and reproduction of a temporal interval, a pattern that cannot be predicted by motor control accounts. Specifically, we found that timing precision resulted from the trade-off between the strength of α–β PAC during the encoding and during the reproduction of intervals. These results support the hypothesis that α–β PAC codes for the precision of temporal representations in the human brain.
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Kurilenkov, Yu K., V. P. Tarakanov, A. V. Oginov, S. Yu Gus’kov i I. S. Samoylov. "Oscillating Plasmas for Proton- Boron Fusion in Miniature Vacuum Discharge". Laser and Particle Beams 2023 (4.03.2023): 1–10. http://dx.doi.org/10.1155/2023/9563197.
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Earlier, the experiments on the aneutronic proton-boron (pB) fusion in a miniature nanosecond vacuum discharge (NVD) with oscillatory plasma confinement and correspondent α particles yield were presented. In this work, we consider some specific features of oscillatory confinement as a relatively new type of plasma confinement for fusion. Particle-in-cell (PiC) simulations of pB fusion processes have shown that the plasma in NVD, and especially on the discharge axis, is in a state close to a quasineutral one, which is rather different from the conditions in the well-known scheme of periodically oscillating plasma spheres (POPSs) suggested earlier for fusion. Apparently, small-scale oscillations in NVD are a mechanism of resonant ion heating, unlike coherent compressions in the original POPS scheme. Nevertheless, the favorable scaling of the fusion power in NVD turns out to be close to the POPS fusion but differs significantly both in the compression ratio and in the values of the parameter of quasineutrality. In addition, unlike the POPS scheme, PiC simulation reveals that the distribution functions of protons and boron ions in NVD are non-Maxwellian. Therefore, we have an aneutronic pB synthesis in a nonequilibrium plasma remaining “nonignited” on the discharge axis.
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Golovin, Ievgen, i Stefan Palis. "PFC-Based Control of Friction-Induced Instabilities in Drive Systems". Machines 9, nr 7 (16.07.2021): 134. http://dx.doi.org/10.3390/machines9070134.
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This paper is concerned with control-based damping of friction-induced self-excited oscillations that appear in electromechanical systems with an elastic shaft. This approach does not demand additional oscillations measurements or an observer design. The control system provides the angular velocity and damping control via the combination of a parallel feed-forward compensator (PFC) and adaptive λ-tracking feedback control. The PFC is designed to stabilize the zero dynamics of an augmented system and renders it almost strict positive real (ASPR). The proposed control approach is tested in simulations.
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Woodruff, Michael L., Victor V. Chaban, Christopher M. Worley i Ellen R. Dirksen. "PKC role in mechanically induced Ca2+ waves and ATP-induced Ca2+ oscillations in airway epithelial cells". American Journal of Physiology-Lung Cellular and Molecular Physiology 276, nr 4 (1.04.1999): L669—L678. http://dx.doi.org/10.1152/ajplung.1999.276.4.l669.
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Mechanical stimulation of airway epithelial cells generates the Ca2+ mobilization messenger inositol 1,4,5-trisphosphate and the protein kinase (PK) C activator diacylglycerol. Inositol 1,4,5-trisphosphate diffuses through gap junctions to mediate intercellular communication of the mechanical stimulus (a “Ca2+ wave”); the role that diacylglycerol-activated PKC might play in the response is unknown. Using primary cultures of rabbit tracheal cells, we show that 12- O-tetradecanoylphorbol 13-acetate- or 1,2-dioctanyl- sn-glycerol-induced activation of PKC slows the Ca2+wave, decreases the amplitude of induced intracellular free Ca2+ concentration ([Ca2+]i) increases, and decreases the number of affected cells. The PKC inhibitors bisindolylmaleimide and Gö 6976 slowed the spread of the wave but did not change the number of affected cells. We show that ATP-induced [Ca2+]iincreases and oscillations, responses independent of intercellular communication, were inhibited by PKC activators. Bisindolylmaleimide decreased the amplitude of ATP-induced [Ca2+]iincreases and blocked oscillations, suggesting that PKC has an initial positive effect on Ca2+mobilization and then mediates feedback inhibition. PKC activators also reduced the [Ca2+]iincrease that followed thapsigargin treatment, indicating a PKC effect associated with the Ca2+ release mechanism.