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OTTERSTEDT, R. D., N. I. JAEGER i P. J. PLATH. "VARIOUS WAVE PHENOMENA DURING THE OSCILLATORY ELECTRODISSOLUTION OF COBALT". International Journal of Bifurcation and Chaos 04, nr 05 (październik 1994): 1265–73. http://dx.doi.org/10.1142/s0218127494000952.
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Experimental studies have been carried out with disk-like cobalt sheets in unstirred diluted phosphoric acid under potentiostatic control. Voltages were chosen such that oscillations of the integral current indicating transitions between the active and the passive state of the metal occurred. Spatiotemporal patterns during these transitions, visible due to changes of the reflectivity of the surface, were recorded with a video camera. High-amplitude periodic relaxation oscillations of the integral current are linked to the accelerated propagation of activation waves covering the whole electrode surface. Low-amplitude aperiodic oscillations of the integral current are associated with propagation in a series of pulses, i.e., accelerating and decelerating waves. Often, the stepwise propagating waves emit during acceleration another wave backwards. Annihilation of waves was also observed.
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Gelens, Lendert, Graham A. Anderson i James E. Ferrell. "Spatial trigger waves: positive feedback gets you a long way". Molecular Biology of the Cell 25, nr 22 (5.11.2014): 3486–93. http://dx.doi.org/10.1091/mbc.e14-08-1306.
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Trigger waves are a recurring biological phenomenon involved in transmitting information quickly and reliably over large distances. Well-characterized examples include action potentials propagating along the axon of a neuron, calcium waves in various tissues, and mitotic waves in Xenopus eggs. Here we use the FitzHugh-Nagumo model, a simple model inspired by the action potential that is widely used in physics and theoretical biology, to examine different types of trigger waves—spatial switches, pulses, and oscillations—and to show how they arise.
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Kostenko, V., O. Zavialova, S. Pozdieiev, T. Kostenko i A. Vinyukov. "SUBSTANTIATION OF DESIGN PARAMETERS OF COAL DUST EXPLOSION CONTAINMENT SYSTEM". Series of Geology and Technical Sciences 447, nr 3 (15.06.2021): 72–79. http://dx.doi.org/10.32014/2021.2518-170x.65.
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The aim of the paper is to identify the qualitative and quantitative parameters of seismic waves and accelerations on the mine working contour after an explosion of the gas-and-dust mixture. Information about the formation of seismic waves in the rock mass accommodating the mine working was received using modelling in order to improve the means of containment of explosion of further developed dust-air mixture. The parameters of seismic waves, such as propagation velocity and acceleration, amplitude, and frequency of oscillations of mine working walls, were established for the conditions of the experimental structure, which allows to scientifically substantiating the design parameters of the systems protecting the miners against explosion. The energy of the explosion propagates in the rock mass in the form of a series of peak-like pulses and oscillations with smaller amplitude. Modulus of acceleration is an informational indicator, which suits the most for registration by seismic sensors responding, specifically, to the most powerful peak pulses formed by seismic waves. By revealing the qualitative and quantitative indicators of seismic wave propagation on the mine working contour and in the rock mass, the parameters of seismic sensors of the systems protecting the miners against explosion can be substantiated.
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Young, Bruce A., Skye Greer i Michael Cramberg. "Slithering CSF: Cerebrospinal Fluid Dynamics in the Stationary and Moving Viper Boa, Candoia aspera". Biology 10, nr 7 (16.07.2021): 672. http://dx.doi.org/10.3390/biology10070672.
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In the viper boa (Candoia aspera), the cerebrospinal fluid (CSF) shows two stable overlapping patterns of pulsations: low-frequency (0.08 Hz) pulses with a mean amplitude of 4.1 mmHg that correspond to the ventilatory cycle, and higher-frequency (0.66 Hz) pulses with a mean amplitude of 1.2 mmHg that correspond to the cardiac cycle. Manual oscillations of anesthetized C. aspera induced propagating sinusoidal body waves. These waves resulted in a different pattern of CSF pulsations with frequencies corresponding to the displacement frequency of the body and with amplitudes greater than those of the cardiac or ventilatory cycles. After recovery from anesthesia, the snakes moved independently using lateral undulation and concertina locomotion. The episodes of lateral undulation produced similar influences on the CSF pressure as were observed during the manual oscillations, though the induced CSF pulsations were of lower amplitude during lateral undulation. No impact on the CSF was found while C. aspera was performing concertina locomotion. The relationship between the propagation of the body and the CSF pulsations suggests that the body movements produce an impulse on the spinal CSF.
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Pagano, P., i I. De Moortel. "Contribution of observed multi frequency spectrum of Alfvén waves to coronal heating". Astronomy & Astrophysics 623 (27.02.2019): A37. http://dx.doi.org/10.1051/0004-6361/201834158.
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Context. Whilst there are observational indications that transverse magnetohydrodynamic (MHD) waves carry enough energy to maintain the thermal structure of the solar corona, it is not clear whether such energy can be efficiently and effectively converted into heating. Phase-mixing of Alfvén waves is considered a candidate mechanism, as it can develop transverse gradient where magnetic energy can be converted into thermal energy. However, phase-mixing is a process that crucially depends on the amplitude and period of the transverse oscillations, and only recently have we obtained a complete measurement of the power spectrum for transverse oscillations in the corona. Aims. We aim to investigate the heating generated by phase-mixing of transverse oscillations triggered by buffeting of a coronal loop that follows from the observed coronal power spectrum as well as the impact of these persistent oscillations on the structure of coronal loops. Methods. We considered a 3D MHD model of an active region coronal loop and we perturbed its footpoints with a 2D horizontal driver that represents a random buffeting motion of the loop footpoints. Our driver was composed of 1000 pulses superimposed to generate the observed power spectrum. Results. We find that the heating supply from the observed power spectrum in the solar corona through phase-mixing is not sufficient to maintain the million-degree active region solar corona. We also find that the development of Kelvin–Helmholtz instabilities could be a common phenomenon in coronal loops that could affect their apparent life time. Conclusions. This study concludes that is unlikely that phase-mixing of Alfvén waves resulting from an observed power spectrum of transverse coronal loop oscillations can heat the active region solar corona. However, transverse waves could play an important role in the development of small scale structures.
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Macdonald, Kurt D., Eva Fifkova, Michael S. Jones i Daniel S. Barth. "Focal Stimulation of the Thalamic Reticular Nucleus Induces Focal Gamma Waves in Cortex". Journal of Neurophysiology 79, nr 1 (1.01.1998): 474–77. http://dx.doi.org/10.1152/jn.1998.79.1.474.
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MacDonald, Kurt D., Eva Fifkova, Michael S. Jones, and Daniel S. Barth. Focal stimulation of the thalamic reticular nucleus induces focal gamma waves in cortex. J. Neurophysiol. 79: 474–477, 1998. Electrical stimulation of the thalamic reticular nucleus (TRN; 0.5-s trains of 500-Hz 0.5-ms pulses at 5–10 μA) evokes focal oscillations of cortical electrical potentials in the gamma frequency band (∼35–55 Hz). These evoked oscillations are specific to either the somatosensory or auditory cortex and to subregions of the cortical receptotopic map, depending on what part of the TRN is stimulated. Focal stimulation of the internal capsule, however, evokes focal slow potentials, without gamma activity. Our results suggest that the TRN's role extends beyond that of general cortical arousal to include specific modality and submodality activation of the forebrain.
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Bastrakova, Marina, Nikolay Klenov, Vsevolod Ruzhickiy, Igor Soloviev i Arkady Satanin. "Sub-nanosecond operations on superconducting quantum register based on Ramsey patterns". Superconductor Science and Technology 35, nr 5 (22.03.2022): 055003. http://dx.doi.org/10.1088/1361-6668/ac5505.
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Abstract An ultrafast qubit control concept is proposed and analyzed theoretically to reduce the duration of operations with single and multiple superconducting qubits. It is based on the generation of Ramsey fringes due to unipolar sub-nanosecond control pulses. The interference of waves of qubit states population propagating forward and backward in time play a key role in the concept. The influence of the shape and duration of control pulses on the contrast of the interference pattern is revealed in the frame of Ramsey’s paradigm. Protocols for the observation of Ramsey oscillations and an implementation of various gate operations are developed for flux qubits. We also suggest a notional engineering solution for creating the required sub-nanosecond control pulses with the desired shape and amplitude. It is demonstrated that this makes it possible to control the quantum states of the system with a fidelity of more than 99%.
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Lu, Yao, Wilson Truccolo, Fabien B. Wagner, Carlos E. Vargas-Irwin, Ilker Ozden, Jonas B. Zimmermann, Travis May, Naubahar S. Agha, Jing Wang i Arto V. Nurmikko. "Optogenetically induced spatiotemporal gamma oscillations and neuronal spiking activity in primate motor cortex". Journal of Neurophysiology 113, nr 10 (czerwiec 2015): 3574–87. http://dx.doi.org/10.1152/jn.00792.2014.
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Transient gamma-band (40–80 Hz) spatiotemporal patterns are hypothesized to play important roles in cortical function. Here we report the direct observation of gamma oscillations as spatiotemporal waves induced by targeted optogenetic stimulation, recorded by intracortical multichannel extracellular techniques in macaque monkeys during their awake resting states. Microelectrode arrays integrating an optical fiber at their center were chronically implanted in primary motor (M1) and ventral premotor (PMv) cortices of two subjects. Targeted brain tissue was transduced with the red-shifted opsin C1V1(T/T). Constant (1-s square pulses) and ramp stimulation induced narrowband gamma oscillations during awake resting states. Recordings across 95 microelectrodes (4 × 4-mm array) enabled us to track the transient gamma spatiotemporal patterns manifested, e.g., as concentric expanding and spiral waves. Gamma oscillations were induced well beyond the light stimulation volume, via network interactions at distal electrode sites, depending on optical power. Despite stimulation-related modulation in spiking rates, neuronal spiking remained highly asynchronous during induced gamma oscillations. In one subject we examined stimulation effects during preparation and execution of a motor task and observed that movement execution largely attenuated optically induced gamma oscillations. Our findings demonstrate that, beyond previously reported induced gamma activity under periodic drive, a prolonged constant stimulus above a certain threshold may carry primate motor cortex network dynamics into gamma oscillations, likely via a Hopf bifurcation. More broadly, the experimental capability in combining microelectrode array recordings and optogenetic stimulation provides an important approach for probing spatiotemporal dynamics in primate cortical networks during various physiological and behavioral conditions.
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Annenkov, Vladimir, Evgeny Berendeev, Evgeniia Volchok i Igor Timofeev. "Particle-in-Cell Simulations of High-Power THz Generator Based on the Collision of Strongly Focused Relativistic Electron Beams in Plasma". Photonics 8, nr 6 (21.05.2021): 172. http://dx.doi.org/10.3390/photonics8060172.
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Based on particle-in-cell simulations, we propose to generate sub-nanosecond pulses of narrowband terahertz radiation with tens of MW power using unique properties of kiloampere relativistic (2 MeV) electron beams produced by linear induction accelerators. Due to small emittance of such beams, they can be focused into millimeter and sub-millimeter spots comparable in sizes with the wavelength of THz radiation. If such a beam is injected into a plasma, it becomes unstable against the two-stream instability and excites plasma oscillations that can be converted to electromagnetic waves at the plasma frequency and its harmonics. It is shown that several radiation mechanisms with high efficiency of power conversion (∼1%) come into play when the radial size of the beam–plasma system becomes comparable with the wavelength of the emitted waves.
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Charloux, Anne, Claude Gronfier, Evelyne Lonsdorfer-Wolf, François Piquard i Gabrielle Brandenberger. "Aldosterone release during the sleep-wake cycle in humans". American Journal of Physiology-Endocrinology and Metabolism 276, nr 1 (1.01.1999): E43—E49. http://dx.doi.org/10.1152/ajpendo.1999.276.1.e43.
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The aim of this study was to assess the relative influence on the 24-h aldosterone profile of the adrenocorticotropic system, primarily modulated by a circadian rhythmicity, and the renin-angiotensin system, which is influenced by sleep. Cortisol, plasma renin activity (PRA), and aldosterone were measured for 24 h in healthy subjects under basal conditions, once with nocturnal sleep and once with a night of sleep deprivation followed by 8 h of daytime sleep. The sleep period displayed high mean aldosterone levels, pulse amplitude, and frequency that were reduced during waking periods. During sleep, aldosterone pulses were mainly related to PRA oscillations, whereas they were mainly associated with cortisol pulses during waking periods. Cross-correlation analysis between sleep electroencephalographic activity in the delta band and aldosterone levels yielded significant results, aldosterone following delta waves by ∼30 min. This study demonstrates that the 24-h aldosterone profile is strongly influenced by sleep processes. A dual influence, by the renin-angiotensin system during sleep and by the adrenocorticotropic system during wakefulness, is exerted on aldosterone pulses throughout the 24-h period.
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Chovnyuk, Y., A. Priymachenko, Р. Cherednichenko, O. Ostapushchenko i I. Kravchenko. "ELASTIC WAVEFORMS ANALYSIS IN THE LOAD LIFTING CRANES ROPES". Modern construction and architecture, nr 4 (28.06.2023): 23–32. http://dx.doi.org/10.31650/2786-6696-2023-4-23-32.
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In the article the boundary value problem on the elastic longitudinal waves motion in the load lifting cranes and mine mechanisms variable length ropes is considered. Solutions of the Cauchy problem, which describe longitudinal oscillations propagation in the ropes (flexible suspensions) as in areas with moving boarders, are found. Displacements and stresses dynamic fields in variable length steel ropes of the specified load lifting mechanisms are investigated. Usually the ropes are balanced, and the main rope carries concentrated stress which before the systems movement was at the main ropes lower end. Dynamic forces in perfectly elastic variable length steel ropes estimation is shown, that only when lifting ropes without end loads under non-integrated boundary conditions, their efforts do not increase. However, practical experience shows that this phenomenon is not observed at moderate lifting speeds due to the fact that along with the dynamic forces amplitudes increase. Due to the decrease in length there is a simultaneous decrease in the amplitudes of their oscillations. The object of analysis refers to a wide range of variable length oscillations one-dimensional objects. A classical mathematical model to describe oscillations and waveforms is used. When studying wave fields in areas with moving boundaries the reflection of pulses from such boundaries is established. Elastic type waveforms in variable length rods (rope models) taking into account the fact that these rods have circular cross section of variable (length of rope/rod) area (rods are cylindrical, rotational paraboloids form, conical rods) is considered. Method based on the possibility of constructing wave equation from waves reflected from fixed and moving given boundaries of a semi-infinite domain solutions is applied.
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van Groesen, E. "Optical Pulse Deformation in Second Order Nonlinear Media". Journal of Nonlinear Optical Physics & Materials 12, nr 02 (czerwiec 2003): 221–34. http://dx.doi.org/10.1142/s0218863503001353.
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The deformation of optical pulses in one dimensional lossless second order nonlinear media is considered. Using a KdV-type of equation, with dispersion determined by the material properties, the deformation of a bichromatic initial signal is studied. An explicit expression for a third order approximation is used and the maximal temporal amplitude MTA is investigated. This MTA is obtained by looking at the maximum over time of the amplitude at each position. It is shown that modulations of the carrier waves and of the envelopes of the bound and free third order terms determine respectively the oscillations and the recurrence of the MTA curve. We will illustrate the explicit formula with numerical displays for the characteristic cases.
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Verma, Deepa, Armelle Michau, Angela Vasanelli, Carlo Sirtori i Khaled Hassouni. "Terahertz emission from a bounded plasma". Physics of Plasmas 30, nr 1 (styczeń 2023): 013507. http://dx.doi.org/10.1063/5.0116748.
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The dynamics of electrons submitted to voltage pulses in a thin semiconductor layer is investigated using a kinetic approach based on the solution of the electron Boltzmann equation using particle-in-cell/Monte Carlo collision simulations. The results showed that due to the fairly high plasma density, oscillations emerge from a highly nonlinear interaction between the space-charge field and the electrons. The voltage pulse excites electron waves with dynamics and phase-space trajectories that depend on the doping level. High-amplitude oscillations take place during the relaxation phase and are subsequently damped over time-scales in the range 100 –400 fs and decrease with the doping level. The power spectra of these oscillations show a high-energy band and a low-energy peak that were attributed to bounded plasma resonances and to a sheath effect. The high-energy THz domain reduces to sharp and well-defined peaks for the high doping case. The radiative power that would be emitted by the thin semiconductor layer strongly depends on the competition between damping and radiative decay in the electron dynamics. Simulations showed that higher doping level favor enhanced magnitude and much slower damping for the high-frequency current, which would strongly enhance the emitted level of THz radiation.
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Srivastava, Abhishek K., i Balveer Singh. "Numerical Simulations of the Decaying Transverse Oscillations in the Cool Jet". Physics 5, nr 3 (25.06.2023): 655–71. http://dx.doi.org/10.3390/physics5030043.
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In the present paper, we describe a 2.5D (two-and-a-half-dimensional) magnetohydrodynamic (MHD) simulation that provides a detailed picture of the evolution of cool jets triggered by initial vertical velocity perturbations in the solar chromosphere. We implement random multiple velocity, Vy, pulses of amplitude 20–50 km s−1 between 1 Mm and 1.5 Mm in the Sun’s atmosphere below its transition region (TR). These pulses also consist of different switch-off periods between 50 s and 300 s. The applied vertical velocity pulses create a series of magnetoacoustic shocks steepening above the TR. These shocks interact with each other in the inner corona, leading to complex localized velocity fields. The upward propagation of such perturbations creates low-pressure regions behind them, which propel a variety of cool jets and plasma flows in the localized corona. The localized complex velocity fields generate transverse oscillations in some of these jets during their evolution. We study the transverse oscillations of a representative cool jet J1, which moves up to the height of 6.2 Mm above the TR from its origin point. During its evolution, the plasma flows make the spine of jet J1 radially inhomogeneous, which is visible in the density and Alfvén speed smoothly varying across the jet. The highly dense J1, which is triggered along the significantly curved magnetic field lines, supports the propagating transverse wave of period of approximately 195 s with a phase speed of about 125 km s−1. In the distance–time map of density, it is manifested as a transverse kink wave. However, the careful investigation of the distance–time maps of the x- and z-components of velocity reveals that these transverse waves are actually of mixed Alfvénic modes. The transverse wave shows evidence of damping in the jet. We conclude that the cross-field structuring of the density and characteristic Alfvén speed within J1 causes the onset of the resonant conversion and leakage of the wave energy outward to dissipate these transverse oscillations via resonant absorption. The wave energy flux is estimated as approximately of 1.0 × 106 ergs cm−2 s−1. This energy, if it dissipates through the resonant absorption into the corona where the jet is propagated, is sufficient energy for the localized coronal heating.
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Sahai, Aakash A., Toshiki Tajima, Peter Taborek i Vladimir D. Shiltsev. "Solid-state tube wakefield accelerator using surface waves in crystals". International Journal of Modern Physics A 34, nr 34 (10.12.2019): 1943009. http://dx.doi.org/10.1142/s0217751x19430097.
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Solid-state or crystal acceleration has for long been regarded as an attractive frontier in advanced particle acceleration. However, experimental investigations of solid-state acceleration mechanisms which offer [Formula: see text] acceleration gradients have been hampered by several technological constraints. The primary constraint has been the unavailability of attosecond particle or photon sources suitable for excitation of collective modes in bulk crystals. Secondly, there are significant difficulties with direct high-intensity irradiation of bulk solids, such as beam instabilities due to crystal imperfections and collisions etc. Recent advances in ultrafast technology with the advent of submicron long electron bunches and thin-film compressed attosecond x-ray pulses have now made accessible ultrafast sources that are nearly the same order of magnitude in dimensions and energy density as the scales of collective electron oscillations in crystals. Moreover, nanotechnology enabled growth of crystal tube structures not only mitigates the direct high-intensity irradiation of materials, with the most intense part of the ultrafast source propagating within the tube but also enables a high degree of control over the crystal properties. In this work, we model an experimentally practicable solid-state acceleration mechanism using collective electron oscillations in crystals that sustain propagating surface waves. These surface waves are driven in the wake of a submicron long particle beam, ideally also of submicron transverse dimensions, in tube shaped nanostructured crystals with tube wall densities, [Formula: see text]. Particle-In-Cell (PIC) simulations carried out under experimental constraints demonstrate the possibility of accessing average acceleration gradients of several [Formula: see text] using the solid-state tube wakefield acceleration regime. Furthermore, our modeling demonstrates the possibility that as the surface oscillations and resultantly the surface wave transitions into a nonlinear or “crunch-in” regime under [Formula: see text], not only does the average gradient increase but strong transverse focusing fields extend down to the tube axis. This work thus demonstrates the near-term experimental realizability of Solid-State Tube Wakefield Accelerator (SOTWA). The ongoing progress in nanoengineering and attosecond source technology thereby now offers the potential to experimentally realize the promise of solid-state or crystal acceleration, opening up unprecedented pathways in miniaturization of accelerators.
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Kamchatnov, A. M., i D. V. Shaykin. "Propagation of instability fronts in modulationally unstable systems". Europhysics Letters 136, nr 4 (1.11.2021): 40001. http://dx.doi.org/10.1209/0295-5075/ac5083.
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Abstract We study the evolution of pulses propagating through focusing nonlinear media. A small disturbance of a smooth initial non-uniform pulse amplitude leads to formation of a region of strong nonlinear oscillations. We develop here an asymptotic method for finding the law of motion of the front of this region. The method is based on the conjecture that instability fronts propagate with the minimal group velocity of linear waves. To support this conjecture, at first we review several physical situations where this statement was obtained as a result of direct calculations. Then we generalize it to situations with a non-uniform flow and apply it to the focusing nonlinear Schrödinger equation for the particular cases of Talanov and Akhmanov-Sukhorukov-Khokhlov initial distributions. The approximate analytical results agree very well with the exact numerical solutions for these two problems.
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Cartella, A., T. F. Nova, M. Fechner, R. Merlin i A. Cavalleri. "Parametric amplification of optical phonons". Proceedings of the National Academy of Sciences 115, nr 48 (14.11.2018): 12148–51. http://dx.doi.org/10.1073/pnas.1809725115.
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We use coherent midinfrared optical pulses to resonantly excite large-amplitude oscillations of the Si–C stretching mode in silicon carbide. When probing the sample with a second pulse, we observe parametric optical gain at all wavelengths throughout the reststrahlen band. This effect reflects the amplification of light by phonon-mediated four-wave mixing and, by extension, of optical-phonon fluctuations. Density functional theory calculations clarify aspects of the microscopic mechanism for this phenomenon. The high-frequency dielectric permittivity and the phonon oscillator strength depend quadratically on the lattice coordinate; they oscillate at twice the frequency of the optical field and provide a parametric drive for the lattice mode. Parametric gain in phononic four-wave mixing is a generic mechanism that can be extended to all polar modes of solids, as a means to control the kinetics of phase transitions, to amplify many-body interactions or to control phonon-polariton waves.
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Sturis, J., W. L. Pugh, J. Tang, D. M. Ostrega, J. S. Polonsky i K. S. Polonsky. "Alterations in pulsatile insulin secretion in the Zucker diabetic fatty rat". American Journal of Physiology-Endocrinology and Metabolism 267, nr 2 (1.08.1994): E250—E259. http://dx.doi.org/10.1152/ajpendo.1994.267.2.e250.
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Insulin secretion from the isolated perfused pancreas is characterized by pulses occurring every 5-15 min. The present experiments were performed to explore the role of glucose in regulating these pulses. The pancreata from 12 Wistar (W), 12 Zucker diabetic fatty (ZDF), and 6 nondiabetic lean Zucker control (ZC) male rats were isolated and perfused at 37 degrees C with an oxygenated Krebs Ringer solution containing bovine serum albumin and glucose. In W and ZDF, insulin secretion was pulsatile during constant glucose, as assessed by pulse analysis (ULTRA). The pulse period in W was significantly shorter than in ZDF (7.1 +/- 0.6 vs. 14.7 +/- 1.0 min; P < 0.001), whereas the median relative pulse amplitude was not different. When glucose was administered as a series of 10-min sine waves, spectral analysis showed that the normalized spectral power at 10 min was greater in W and ZC compared with ZDF (34.2 +/- 5.9 and 32.9 +/- 2.9 vs. 3.2 +/- 0.9; P < 0.0001), demonstrating entrainment of the insulin pulses to the exogenous glucose oscillations in W and ZC but not in ZDF. Furthermore, in ZDF, the insulin secretory rates were not higher when 28 mM rather than 7 mM glucose were used. In additional studies, islets of Langerhans from one W, three ZDF, and three ZC rats were isolated and perifused using an oscillatory glucose concentration. Single and groups of islets were studied. Islets from diabetic rats demonstrated the same lack of entrainment by glucose seen in the perfused pancreas, suggesting that the defect is at the cellular level.(ABSTRACT TRUNCATED AT 250 WORDS)
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Contreras, D., R. Curro Dossi i M. Steriade. "Bursting and tonic discharges in two classes of reticular thalamic neurons". Journal of Neurophysiology 68, nr 3 (1.09.1992): 973–77. http://dx.doi.org/10.1152/jn.1992.68.3.973.
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1. Two types of cat reticular (RE) thalamic cells were disclosed by means of intracellular recordings under urethan anesthesia. The RE neurons were identified by their typical depolarizing spindle oscillations in response to synchronous stimulation of the internal capsule. 2. In type I neurons (n = 41), depolarizing current pulses induced tonic firing at the resting or slightly depolarized membrane potential (Vm) and triggered high-frequency spike bursts at a Vm more negative than -75 mV. As well, these cells discharged rebound bursts at the break of a hyperpolarizing current pulse. Internal capsule stimulation elicited spindle sequences made off by depolarizing waves giving rise to spike bursts. 3. Type II cells (n = 9) did not discharge spike bursts to large depolarizing current pulses even when the Vm reached -100 mV, nor did they fire rebound bursts after long-lasting hyperpolarizing current pulses or spike bursts riding on the rhythmic depolarizing components of spindle sequences. 4. Compared with type I cells, type II cells showed less frequency accommodation during tonic firing. The latter neuronal class discharged at high frequencies (40 Hz) with slight DC depolarization, approximately 8-10 Hz at the resting Vm, and no underlying synaptic or subthreshold oscillatory events could be detected when the firing was blocked by DC hyperpolarization. 5. The presence of two cell classes in the RE nucleus challenges the common view that this nucleus consists of a single neuronal class. We suggest that a different set of conductances is present in type II RE neurons, thus preventing the low-threshold Ca2+ current from dominating the behavior of these cells.
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Swann, Karl. "The soluble sperm oscillogen hypothesis". Zygote 1, nr 4 (listopad 1993): 273–76. http://dx.doi.org/10.1017/s0967199400001581.
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It is now accepted that sperm trigger deuterostome egg activation by causing an increase in egg cytoplasmic Ca2+ levels (Jaffe, 1983; Whitaker & Swann, 1993). This increase generally takes the form of a single wave of Ca2+ release that crosses the egg from the point of sperm-egg interaction (Jaffe, 1983)eggs Ca2+ waves occur repetitively and soon turn into synchronous pulses, or homogeneous oscillations, that last for hours after sperm-egg fusion (Miyazaki et al., 1993b; Homa et al., 1993). Despite their extensive characterisation it is still not established how sperm trigger these Ca2+ changes in eggs. The signal transduction mechanism is missing. There is a proliferation of overlapping and complex schemes for how the sperm may initiate Ca2+ release (Miyazaki et al., 1993b;Whitaker & Swann, 1993). Here, my aim is to present one simple scheme in its generic form. The brevity of this essay restricts citations and necessitates using reviews to reference original work.
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Grimaldi, Daniela, Christian Mikutta, Kathryn Reid, Nelly Papalambros, Roneil Malkani, Sabra Abbott, Ken Paller i Phyllis Zee. "0059 Acoustic enhancement of sleep slow oscillations nested to spindles relative to delta waves improves memory consolidation". SLEEP 46, Supplement_1 (1.05.2023): A28. http://dx.doi.org/10.1093/sleep/zsad077.0059.
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Abstract Introduction The nesting of electroencephalographic (EEG) sleep slow oscillations (SOs) to spindles has been shown to be important for sleep-dependent memory consolidation. However, recent evidence indicates that a higher proportion of SOs nested to spindles, relative to δ waves, might be even more critical for sleep-dependent memory consolidation. Acoustic stimulation during slow wave sleep has been shown to be effective in improving memory consolidation. Here, we examined the contribution of SOs nested to spindles relative to δ waves on sleep-dependent declarative memory consolidation associated with acoustic stimulation. Methods Twenty subjects (18-35 years, 75% females) participated in a randomized cross-over study. At each visit participants received either stimulation (stim) or sham following an adaption night. Stim occurred in blocks of 5 pulses (ON intervals) followed by a period of equal length with no stimulation (OFF intervals). Participants learned 40 Arabic-English word pairs and were tested before sleep and after sleep in the morning and again in the afternoon. Detection of SOs (< 2 Hz), δ waves (2-4 Hz), spindles (11-16Hz), and the ratio (%) of spindles nested to SO over δ waves (SO/δ Nesting Index) were calculated during ON intervals for stim and sham conditions. Results Overnight mean (SD) percentage change in word recall between conditions was similar in the morning (stim 6(3)%, sham 4(6)%, p=0.68), but was higher in the afternoon in stim compared to the sham condition (stim 10(4)%, sham 4(6)%, p=0.02). The SO/δ Nesting Index was higher in stim compared to the sham condition (stim 21(13)%, sham 13(10%), p=0.004). Within-subject improvement from sham to stim condition in afternoon memory was associated with a greater change in SO/δ Nesting Index (R=0.63, p=0.03), this association was not observed for spindles nested to SOs (R=0.33, p=0.202) or spindles nested to δ waves (R=-0.18, p=0.811). Conclusion Enhancement of memory consolidation with acoustic stimulation may be dependent on its ability to increase SOs nested to spindles relative to δ waves. Dynamic changes in the relationships between SOs, δ waves and spindles can help inform novel EEG-derived markers and targets to enhance sleep-dependent memory consolidation. Support (if any) DARPA award W911NF-16- 2-0021
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Jury, Mark R. "Atmosphere-Ocean Processes Governing Inflow to the Northern Caribbean Sea". Journal of Marine Science and Engineering 11, nr 4 (26.03.2023): 718. http://dx.doi.org/10.3390/jmse11040718.
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Near-surface currents entering the northern Caribbean from the Atlantic are described using ocean reanalysis at monthly to daily timescales, underpinned by satellite data assimilation. Statistical analyses involved spatial clustering into current vector modes with associated time scores for quantifying spectral power and regression onto atmospheric fields. Inflow across the Anegada, Mona, Windward (AMW) Passages peaks at ~100 m depth at ~0.2 m/s during summer and pulses at periods of 45, 100, and 365 days, and at 3, 6.5 years. The intra-seasonal periods may relate to Madden–Julian Oscillations and westward ocean Rossby waves, while inter-annual periods associate with regional climate anomalies. An empirical orthogonal function analysis demonstrates that AMW inflow varies across multiple timescales and is enhanced when the subtropical high-pressure ridge penetrates into the western Caribbean. A case study reveals key features during a surge of inflow to the northern Caribbean. Marine climate change involves heat advected poleward by currents along the western edge of the tropical Atlantic, fed through the Caribbean Sea. Consequently, the study of inflows garners wide interest.
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Wang, Hao-Tian, i Xiao-Yong Wen. "Dynamics of multi-soliton and breather solutions for a new semi-discrete coupled system related to coupled NLS and coupled complex mKdV equations". Modern Physics Letters B 32, nr 28 (4.10.2018): 1850340. http://dx.doi.org/10.1142/s0217984918503402.
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In this paper, a new semi-discrete coupled system which was firstly proposed by Bronsard and Pelinovsky is under investigation. Based on its known Lax pair, the infinitely-many conservation laws and discrete N-fold DT for this system are constructed. As applications, bell-shaped multi-soliton and breather solutions in terms of determinants for this system are firstly derived by means of the discrete N-fold DT. Propagation and elastic interaction structures of such soliton solutions are shown graphically: (1) Propagation characteristics of one-, two-, three- and four-soliton solutions are discussed from vanishing background. (2) Propagation characteristics of one- and two-breather solutions are analyzed from the plane wave background. The details of the dynamical evolutions for such soliton and breather solutions are studied via numerical simulations. Numerical results show the accuracy of our numerical scheme and the stable evolutions of these solitons with or without a noise in a relatively short period of time, while the evolutions exhibit obviously larger oscillations and strong instability with the increase in time. These results may be useful for understanding the propagation of orthogonally polarized optical waves in an isotropic medium and circularly polarized few-cycle pulses in Kerr media described by the coupled NLS and coupled complex mKdV equations, respectively.
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Walker, A. D. M. "Excitation of field line resonances by sources outside the magnetosphere". Annales Geophysicae 23, nr 10 (30.11.2005): 3375–88. http://dx.doi.org/10.5194/angeo-23-3375-2005.
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Abstract. Field line resonances are thought to be excited by sources either at the magnetopause or outside it. Recent observations suggest that they may be associated with coherent oscillations or pressure pulses in the solar wind. In either case the excitation mechanism can be understood by considering the incidence of a harmonic wave on the magnetopause from outside the magnetosphere. Calculations are performed in a plane stratified model that consists of (i) a magnetosheath region streaming tailward at uniform velocity (ii) a sharp boundary representing the magnetopause, (iii) a magnetosphere region in which the Alfvén speed increases monotonically with distance from the magnetopause. The structure implies the existence of a propagating region within the magnetopause bounded by a reflection level or turning point. Beyond this is a region in which waves are evanescent and a resonance level. The reflection and transmission of harmonic waves incident from the magnetosheath is considered in this model. It is shown that, in most cases, because of the mismatch between the magnetosphere and the magnetopause, the wave is reflected from the magnetopause with little penetration. At critical frequencies corresponding to the natural frequencies of the cavity formed between the magnetopause and turning point the signal excites the cavity and may leak evanescently to the resonance. The calculation includes the effect of the counter-streaming magnetosheath and magnetosphere plasmas on the wave. This can lead to amplification or attenuation. The nature of the processes that lead to transmission of the wave from magnetosheath to resonance are considered by synthesising the signal from plane wave spectra. A number of mechanisms for exciting cavity modes are reviewed and the relationship of the calculations to these mechanisms are discussed. Observations needed to discriminate between the mechanisms are specified.
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Abramova, E. S., S. F. Balandin, V. A. Donchenko, V. F. Myshkin, V. A. Khan i M. S. Pavlova. "PHYSICAL PROCESSES IN THE ATMOSPHERE IONIZED BY LASER RADIATION DURING THE CREATION OF A RADIO COMMUNICATION LINE". T-Comm 16, nr 8 (2022): 4–11. http://dx.doi.org/10.36724/2072-8735-2022-16-8-4-11.
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The results of studies of ionization processes in the atmosphere that occur under the action of laser radiation make it possible to consider the possibility of using directed laser beams for location or formation of a communication channel. To do this, with the help of laser radiation in the atmosphere, a channel with a weakly ionized wall is formed, into which radio emission is introduced. The mini mum electron concentration Ne in the ionized channel, which ensures the reflection of the transmitted electromagnetic wave, depends on its frequency. If the frequency of electromagnetic radiation propagating in the channel is less than the frequency of plasma oscillations in the medium, then the waves are completely reflected from the ionized layer. In the range of long waves (1000-3000 m), the effect of self-radiation of plasma centers can be used to transmit information. By changing the dimensions of the plasma source in space, by modulating the laser radiation, it is possible to vary the frequency and amplitude of the emitted electromagnetic waves in a given range. The main mechanisms of creation of weak ionization channels in the atmosphere by laser radiation are considered. A scheme for the transmission of electromagnetic energy is proposed and its parameters are calculated. A variant of electromagnetic energy transfer by creating a plasma mirror in the atmosphere is considered. The frequency, duration, and energy of laser pulses necessary to create weak ionization channels in the atmosphere and ionosphere are estimated. The calculations and experiments carried out showed that an IR laser sub nanosecond radiation source with a pulse repetition rate of 108 Hz and providing a breakdown or pre-breakdown ionization mode can be used to transfer electromagnetic microwave energy in the atmosphere. It has been established that in the atmosphere it is possible to use both the breakdown mode and the pre-breakdown mode for generating and transmitting long-wave and microwave electromagnetic radiation. It is shown that in the pre-breakdown mode of aerosol ionization, anomalous scattering on plasma particle halos may occur due to the formation of plasmons, which increase the scattering intensity by 2-3 orders of magnitude.
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Wang, Youmei, M. Y. Yu, Z. Y. Chen i Gaimin Lu. "Excitation of large amplitude wake electron oscillations in adiabatic plasma". Laser and Particle Beams 31, nr 1 (1.02.2013): 155–61. http://dx.doi.org/10.1017/s0263034612000973.
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AbstractElectron plasma waves excited and/or modified by finite objects such as laser and charged particle pulses are investigated nonperturbatively using a simple model where the driver is unaffected by the interaction. It is shown that smooth as well as sharply peaked electron plasma wake waves of large amplitude can exist. In particular, two charged pulses moving in tandem can excite a highly localized electron plasma wave without producing the expected long wake wave, a configuration that should be particularly useful for efficient trapping and acceleration of electrons to high energies.
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Pape, Hans-Christian, Denis Paré i Robert B. Driesang. "Two Types of Intrinsic Oscillations in Neurons of the Lateral and Basolateral Nuclei of the Amygdala". Journal of Neurophysiology 79, nr 1 (1.01.1998): 205–16. http://dx.doi.org/10.1152/jn.1998.79.1.205.
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Pape, Hans-Christian, Denis Paré, and Robert B. Driesang. Two types of intrinsic oscillations in neurons of the lateral and basolateral nuclei of the amygdala. J. Neurophysiol. 79: 205–216, 1998. Intracellular recordings in the guinea pig and cat basolateral amygdaloid (BL) complex maintained as slices in vitro revealed that a subpopulation of neurons (79%) in the lateral (AL) and basolateral (ABl) nuclei generated two types of slow oscillations of the membrane potential upon steady depolarization from resting potential. The cells were of a stellate or pyramidal-like shape and possessed spiny dendrites and an axon leaving the local synaptic environment, and thus presumably represented projection neurons. Similar oscillatory activity was observed in projection neurons of the cat AL nucleus recorded in vivo. Oscillatory activity with a low threshold of activation (low-threshold oscillation, LTO) appeared as rhythmic deflections (amplitudes, 2–6 mV) of the membrane potential positive to −60 mV. Fast Fourier transformation (FFT) demonstrated a range of frequencies of LTOs between 0.5 and 9 Hz, with >80% occurring at 1–3.5 Hz and an average at 2.3 ± 1.1 Hz. LTOs were more regular after pharmacological blockade of synaptic transmission and were blocked by tetrodotoxin (TTX). Blockade of LTOs and Na+ spikes revealed a second type of oscillatory activity (high-threshold oscillation, HTO) at depolarizations beyond −40 mV, which was capable of triggering high-threshold spikes. HTOs ranged between 1 and 7.5 Hz, with >80% occurring at 2–6 Hz and an average at 5.8 ± 1.1 Hz. HTOs vanished at a steady membrane polarization positive to −20 mV. Current versus voltage relations obtained under voltage-clamp conditions revealed two regions of negative slope conductance at −55 to −40 mV and at around −30 mV, which largely overlapped with the voltage ranges of LTOs and HTOs. TTX abolished the first region of negative slope conductance (−55 to −40 mV) and did not significantly influence the second region of negative slope conductance. Neuronal responses to maintained depolarizing current pulses consisted of an initial high-frequency discharge (up to 100 Hz), the frequency of which depended on the amplitude of the depolarizing current pulse, followed by a progressive decline (“adaptation”) toward a slow-rhythmic firing pattern. The decay in firing frequency followed a double-exponential function, with time constants averaging 57 ± 28 ms and 3.29 ± 1.85 s, and approached steady-state frequencies at 6.3 ± 2.9 Hz ( n = 17). Slow-rhythmic firing remained at this frequency over a wide range of membrane polarization between approximately −50 and −20 mV, although individual electrogenic events changed from Na+ spikes and underlying LTOs to high-threshold spikes and underlying HTOs. Rhythmic regular firing was only interrupted at an intermediate range of membrane polarization by the occurrence of spike doublets. In conclusion, the integrative behavior of a class of neurons in the BL complex appears to be largely shaped by the slow-oscillatory properties of the membrane. While LTOs are likely to synchronize synaptic signals near firing threshold, HTOs are a major determinant for the slow steady-state firing patterns during maintained depolarizing influence. These intrinsic oscillatory mechanisms, in turn, can be assumed to promote population activity at this particular frequency, which ranges well within that of the limbic theta (Θ) rhythm and the delta (δ) waves in the electroencephalogram during slow-wave sleep.
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Ballerini, Laura, Enrico Bracci i Andrea Nistri. "Pharmacological Block of the Electrogenic Sodium Pump Disrupts Rhythmic Bursting Induced by Strychnine and Bicuculline in the Neonatal Rat Spinal Cord". Journal of Neurophysiology 77, nr 1 (1.01.1997): 17–23. http://dx.doi.org/10.1152/jn.1997.77.1.17.
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Ballerini, Laura, Enrico Bracci, and Andrea Nistri. Pharmacological block of the electrogenic sodium pump disrupts rhythmic bursting induced by strychnine and bicuculline in the neonatal rat spinal cord. J. Neurophysiol. 77: 17–23, 1997. The cellular mechanisms underlying rhythmic bursts induced in the isolated neonatal rat spinal cord by bath application of strychnine and bicuculline (which block glycine- and γ-aminobutyric acid-A-receptor-mediated inhibition, respectively) were probed with pharmacological tools. Such spontaneous bursts were recorded either intracellularly from lumbar motoneurons or extracellularly from ventral roots. As previously described, these network-driven events consisted of large-amplitude depolarizations arising abruptly from baseline with a highly regular period (on average 28 s). Burst episodes (lasting on average 7 s) comprised several oscillations and appeared synchronously on flexor and extensor motoneuron pools of both sides of the spinal cord. Their diffuse location made convenient to use bath-applied substances in the attempt to selectively block distinct membrane processes operating through the network. Application of apamin (0.4 μM) shortened both cycle period and burst duration without changing their regular rhythmicity. Similar results were obtained with carbachol (10 μM). Cs+ (4 mM) reversibly hyperpolarized the motoneuron membrane potential and largely increased burst duration, which was characterized by a long series of repetitive oscillatory waves. Cycle period and rhythmicity remained unaltered. Ouabain (10 μM), strophanthidin (4 μM), or K+-free solutions disrupted rhythmic bursting, which was fragmented into irregularly occurring paroxysmal activity mixed with short depolarizing events, still developing simultaneously on both sides of the spinal cord. Bursting activity eventually ceased after ∼30–40 min of application of ouabain or strophanthidin. Prolonged washout of strophanthidin or K+-free solutions reestablished regular bursting patterns, whereas no recovery from ouabain was observed. At the time of strong depression of bursting, it was still possible to evoke bursts by single electrical pulses applied to the segmental dorsal root. Antidromic spikes of motoneurons could still be evoked by ventral root stimulation. These results demonstrate that, in a spinal bursting network mainly made up by excitatory processes, blockers of slow Ca2+-dependent K+ currents, such as apamin or carbachol, or of the slow inward rectifier, such as Cs+, did not suppress rhythmicity, suggesting that these conductances simply contributed to control cycle period and/or burst duration. Conversely, pharmacological blockers of the electrogenic Na+ pump such as ouabain, strophanthidin, or K+-free solutions severely disrupted all characteristics of rhythmic bursting. It is proposed that the operation of the electrogenic Na+ pump of premotoneurons was a crucial element for rhythmic bursting.
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Grakovski, Alexander, Yuri Krasnitski, Igor Kabashkin i Victor Truhachov. "Some Approaches to the Rolling Wheels’ Dynamics Modelling in the Weight-in-Motion Problem". Transport and Telecommunication Journal 14, nr 1 (1.03.2013): 57–78. http://dx.doi.org/10.2478/ttj-2013-0007.
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Abstract Some possibilities of fibre-optic sensors (FOS) application for measuring the weight of moving vehicles realized in weightin- motion (WIM) systems are discussed. As the first, the model of small-buried seismic sensor transient response excited by a car tyre interaction with asphalt-concrete road pavement is proposed. It is supposed that a seismic wave received by the sensor is the vertical component of surface Raleigh wave. The model is based on supposition that a tyre footprint is acceptable to consider as some array of point sources of these waves. The proper algorithms permit to vary different parameters of the array excitation, as to footprint dimensions, load distribution, car velocities and others. The set of Matlab codes is worked out for seismic pulses modelling and processing. The second way considered is to simulate the FOS signal in the basis of differential equations describing a deformable wheel behaviour, or wheel oscillations, in order to identify relations with optoelectronic mechanical parameters. An attempt to find the mass of the vehicle is based on minimizing the discrepancy between the actual FOS signal and the solution of the differential equation. The accuracy of the evaluated weight depends on many external factors, the mathematical modelling of them are expressed in the numerical values of the coefficients and external stimuli. The influence of these factors are analysed and tested by simulations and field experiments. One of ideas in dynamic weighing problem solution should consist in evaluation of position of virtual gravity centre of the vehicle in time. The processing algorithm of the data received from the FOS is proposed based on conception of database retaining in some reference system memory. Certain requirements concerning the elements and blocks of the algorithm are defined as well. The reference system is realized as the digital filter with the finite impulse response. The method to estimate the filter coefficients is worked out. Several experiments with this algorithm have been carried out for the vehicle identification with the reference loads adopted from real data. The different factors have an influence on the measurement accuracy of FOS. The roadbed features, temperature, nonlinearities and delay effects in FOS are among them. The results of laboratory and field measurements with FOS responses to different axle’s loadings are presented. Charging and inertial characteristics of FOS under the impact of various external factors (protective cover, temperature, contact area, and installation mode especially) as well as their approximations are investigated. It is found that the final calibration of the FOS has to be done individually and only after it has been installed in the pavement. Certain methods and algorithms of linearization, as well temperature and dynamic errors compensation of FOS data are discussed.
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Gosak, Marko, Richard Yan-Do, Haopeng Lin, Patrick E. MacDonald i Andraž Stožer. "Ca2+ Oscillations, Waves, and Networks in Islets from Human Donors With and Without Type 2 Diabetes". Diabetes, 6.09.2022. http://dx.doi.org/10.2337/db22-0004.
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Pancreatic islets are highly interconnected structures that produce pulses of insulin and other hormones, maintaining normal homeostasis of glucose and other nutrients. Normal stimulus-secretion and intercellular coupling are essential to regulated secretory responses and these hallmarks are known to be altered in diabetes. In the present study, we used calcium imaging of isolated human islets to assess their collective behavior. The activity occurred in the form of calcium oscillations, was synchronized across different regions of islets through calcium waves, and was glucose-dependent: higher glucose enhanced the activity, elicited a greater proportion of global calcium waves, and led to denser and less fragmented functional networks. Hub regions were identified in stimulatory conditions and they were characterized by long active times. Moreover, calcium waves were found to be initiated in different subregions and the roles of initiators and hubs did not overlap. In type 2 diabetes, glucose-dependence was retained, but a reduced activity, locally restricted waves, and more segregated networks were detected compared with control islets. Interestingly, hub regions seemed to suffer the most by losing a disproportionately large fraction of connections. These changes affected islets from donors with diabetes in a heterogeneous manner.
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Zloshchastiev, Konstantin G. "Acoustic oscillations in cigar-shaped logarithmic Bose–Einstein condensate in the Thomas–Fermi approximation". International Journal of Modern Physics B, 5.08.2021, 2150229. http://dx.doi.org/10.1142/s0217979221502295.
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We consider the dynamical properties of density fluctuations in the cigar-shaped Bose–Einstein condensate described by the logarithmic wave equation with a constant nonlinear coupling by using the Thomas–Fermi and linear approximations. It is shown that the propagation of small density fluctuations along the long axis of a condensed lump in a strongly anisotropic trap is essentially one-dimensional, while the trapping potential can be disregarded in the linear regime. Depending on the sign of nonlinear coupling, the fluctuations either take the form of translationally symmetric pulses and standing waves or become oscillations with varying amplitudes. We also study the condensate in an axial harmonic trap, by using elasticity theory’s notions. Linear particle density and energy also behave differently depending on the nonlinear coupling’s value. If it is negative, the density monotonously grows along with lump’s radius, while energy is a monotonous function of density. For the positive coupling, the density is bound from above, whereas energy grows monotonously as a function of density until it reaches its global maximum.
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Li, Runze, H. E. Elsayed-Ali, Jie Chen, Dinesh Dhankhar, Arjun Krishnamoorthi i Peter M. Rentzepis. "Ultrafast time-resolved structural changes of thin-film ferromagnetic metal heated with femtosecond optical pulses". Journal of Chemical Physics 151, nr 12 (24.09.2019). http://dx.doi.org/10.1063/1.5111578.
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As a classic ferromagnetic material, nickel has been an important research candidate used to study dynamics and interactions of electron, spin, and lattice degrees of freedom. In this study, we specifically chose a thick, 150 nm ferromagnetic nickel (111) single crystal rather than 10–20 nm thin crystals that are typically used in ultrafast studies, and we revealed both the ultrafast heating within the skin depth and the heat transfer from the surface (skin) layer to the bulk of the crystal. The lattice deformation after femtosecond laser excitation was investigated by means of 8.04 keV subpicosecond x-ray pulses, generated from a table-top laser-plasma based source. The temperature evolution of the electron, spin, and lattice was determined using a three temperature model. In addition to coherent phonon oscillations, the blast force and sonic waves, induced by the hot electron temperature gradient, were also observed by monitoring the lattice contractions during the first couple of picoseconds after laser irradiation. This study further revealed the tens of picoseconds time required for heating the hundred nanometer bulk of the Ni (111) single crystals.
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Ye, Meijun, Krystyna Solarana, Harmain Rafi, Shyama Patel, Marjan Nabili, Yunbo Liu, Stanley Huang i in. "Longitudinal Functional Assessment of Brain Injury Induced by High-Intensity Ultrasound Pulse Sequences". Scientific Reports 9, nr 1 (29.10.2019). http://dx.doi.org/10.1038/s41598-019-51876-5.
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Abstract Exposure of the brain to high-intensity stress waves creates the potential for long-term functional deficits not related to thermal or cavitational damage. Possible sources of such exposure include overpressure from blast explosions or high-intensity focused ultrasound (HIFU). While current ultrasound clinical protocols do not normally produce long-term neurological deficits, the rapid expansion of potential therapeutic applications and ultrasound pulse-train protocols highlights the importance of establishing a safety envelope beyond which therapeutic ultrasound can cause neurological deficits not detectable by standard histological assessment for thermal and cavitational damage. In this study, we assessed the neuroinflammatory response, behavioral effects, and brain micro-electrocorticographic (µECoG) signals in mice following exposure to a train of transcranial pulses above normal clinical parameters. We found that the HIFU exposure induced a mild regional neuroinflammation not localized to the primary focal site, and impaired locomotor and exploratory behavior for up to 1 month post-exposure. In addition, low frequency (δ) and high frequency (β, γ) oscillations recorded by ECoG were altered at acute and chronic time points following HIFU application. ECoG signal changes on the hemisphere ipsilateral to HIFU exposure are of greater magnitude than the contralateral hemisphere, and persist for up to three months. These results are useful for describing the upper limit of transcranial ultrasound protocols, and the neurological sequelae of injury induced by high-intensity stress waves.
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Baratta, Mirko, Andrea Emilio Catania i Alessandro Ferrari. "Hydraulic Circuit Design Rules to Remove the Dependence of the Injected Fuel Amount on Dwell Time in Multijet CR Systems". Journal of Fluids Engineering 130, nr 12 (27.10.2008). http://dx.doi.org/10.1115/1.2969443.
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In multijet common rail (CR) systems, the capability to manage multiple injections with full flexibility in the choice of the dwell time (DT) between consecutive solenoid current pulses is one of the most relevant design targets. Pressure oscillations triggered by the nozzle closure after each injection event induce disturbances in the amount of fuel injected during subsequent injections. This causes a remarkable dispersion in the mass of fuel injected when DT is varied. The effects of the hydraulic circuit layout of CR systems were investigated with the objective to provide design rules for reducing the dependence of the injected fuel amount on DT. A multijet CR of the latest solenoid-type generation was experimentally analyzed at different operating conditions on a high performance test bench. The considerable influence that the injector-supplying pipe dimensions can exert on the frequency and amplitude of the injection-induced pressure oscillations was widely investigated and a physical explanation of cause-effect relationships was found by energetics considerations, starting from experimental tests. A parametric study was performed to identify the best geometrical configurations of the injector-supplying pipe so as to minimize pressure oscillations. The analysis was carried out with the aid of a previously developed simple zero-dimensional model, allowing the evaluation of pressure-wave frequencies as functions of main system geometric data. Pipes of innovative aspect ratio and capable of halving the amplitude of injected-volume fluctuations versus DT were proposed. Purposely designed orifices were introduced into the rail-pipe connectors of a commercial automotive injection system, so as to damp pressure oscillations. Their effects on multiple-injection performance were experimentally determined as being sensible. The resulting reduction in the injector fueling capacity was quantified. It increased by lowering the orifice diameter. The application of the orifice to the injector inlet-pipe with innovative aspect ratio led to a hydraulic circuit solution, which coupled active and passive damping of the pressure waves and minimized the disturbances in injected fuel volumes. Finally, the influence of the rail capacity on pressure-wave dynamics was studied and the possibility of severely reducing the rail volume (up to one-fourth) was assessed. This can lead to a system not only with reduced overall sizes but also with a prompter dynamic response during engine transients.
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Sharma, Deepak, Kevin K. W. Ng, Ingvars Birznieks i Richard M. Vickery. "Auditory clicks elicit equivalent temporal frequency perception to tactile pulses: A cross-modal psychophysical study". Frontiers in Neuroscience 16 (9.09.2022). http://dx.doi.org/10.3389/fnins.2022.1006185.
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Both hearing and touch are sensitive to the frequency of mechanical oscillations—sound waves and tactile vibrations, respectively. The mounting evidence of parallels in temporal frequency processing between the two sensory systems led us to directly address the question of perceptual frequency equivalence between touch and hearing using stimuli of simple and more complex temporal features. In a cross-modal psychophysical paradigm, subjects compared the perceived frequency of pulsatile mechanical vibrations to that elicited by pulsatile acoustic (click) trains, and vice versa. Non-invasive pulsatile stimulation designed to excite a fixed population of afferents was used to induce desired temporal spike trains at frequencies spanning flutter up to vibratory hum (>50 Hz). The cross-modal perceived frequency for regular test pulse trains of either modality was a close match to the presented stimulus physical frequency up to 100 Hz. We then tested whether the recently discovered “burst gap” temporal code for frequency, that is shared by the two senses, renders an equivalent cross-modal frequency perception. When subjects compared trains comprising pairs of pulses (bursts) in one modality against regular trains in the other, the cross-sensory equivalent perceptual frequency best corresponded to the silent interval between the successive bursts in both auditory and tactile test stimuli. These findings suggest that identical acoustic and vibrotactile pulse trains, regardless of pattern, elicit equivalent frequencies, and imply analogous temporal frequency computation strategies in both modalities. This perceptual correspondence raises the possibility of employing a cross-modal comparison as a robust standard to overcome the prevailing methodological limitations in psychophysical investigations and strongly encourages cross-modal approaches for transmitting sensory information such as translating pitch into a similar pattern of vibration on the skin.
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Liu, Yingjian, Gang Wang, Chao Cao, Gaorui Zhang, Emily B. Tanzi, Yang Zhang, Weidong Zhou i Yi Li. "Neuromodulation Effect of Very Low Intensity Transcranial Ultrasound Stimulation on Multiple Nuclei in Rat Brain". Frontiers in Aging Neuroscience 13 (15.04.2021). http://dx.doi.org/10.3389/fnagi.2021.656430.
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ObjectiveLow-intensity transcranial ultrasound stimulation (TUS) is a non-invasive neuromodulation technique with high spatial resolution and feasible penetration depth. To date, the mechanisms of TUS modulated neural oscillations are not fully understood. This study designed a very low acoustic intensity (AI) TUS system that produces considerably reduced AI Ultrasound pulses (ISPTA < 0.5 W/cm2) when compared to previous methods used to measure regional neural oscillation patterns under different TUS parameters.MethodsWe recorded the local field potential (LFP) of five brain nuclei under TUS with three groups of simulating parameters. Spectrum estimation, time-frequency analysis (TFA), and relative power analysis methods have been applied to investigate neural oscillation patterns under different stimulation parameters.ResultsUnder PRF, 500 Hz and 1 kHz TUS, high-amplitude LFP activity with the auto-rhythmic pattern appeared in selected nuclei when ISPTA exceeded 12 mW/cm2. With TFA, high-frequency energy (slow gamma and high gamma) was significantly increased during the auto-rhythmic patterns. We observed an initial plateau in nuclei response when ISPTA reached 16.4 mW/cm2 for RPF 500 Hz and 20.8 mW/cm2 for RPF 1 kHz. The number of responding nuclei started decreasing while ISPTA continued increasing. Under 1.5 kHz TUS, no auto-rhythmic patterns have been observed, but slow frequency power was increased during TUS. TUS inhibited most of the frequency band and generated obvious slow waves (theta and delta band) when stimulated at RPF = 1.5 kHz, ISPTA = 8.8 mW/cm2.ConclusionThese results demonstrate that very low intensity Transcranial Ultrasound Stimulation (VLTUS) exerts significant neuromodulator effects under specific parameters in rat models and may be a valid tool to study neuronal physiology.
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Podolsky, M. I., I. Y. Lilevman, O. Y. Lilevman i O. Y. Kedrovsky. "IMPROVEMENT OF MUFFLER S DESIGN FOR REDUCTION OF THE LEVEL OF SOUND PRESSURE ON SMALL TRACTORS OPERATORS". Technical and technological aspects of development and testing of new machinery and technologies for agriculture of Ukraine, nr 28(42) (czerwiec 2021). http://dx.doi.org/10.31473/2305-5987-2021-1-28(42)-3.
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Noise background, as an important factor in the working conditions of agricultural operators, has a direct impact on human health and productivity. This topic is especially relevant for small tractors, which in most cases are not equipped with cabs. One of the main means of reducing the sound pressure on the operator are the mufflers of exhaust gases, which mainly have a labyrinth-absorbing type of action. The paper proposes a fundamental approach to the design of the muffler by the criterion of reflection and scattering of sound waves with the verification of efficiency by computer simulation. The purpose of research: - to improve the working conditions of operators of small tractors that are not equipped with cabs, by reducing the sound pressure level from internal combustion engines; - to improve the noise-absorbing properties of mufflers of exhaust gases of engines with observance of requirements to manufacturability of process of their manufacturing; - to develop a structural scheme of the exhaust gases muffler based on the results of preliminary modeling and analysis of the trajectory of the gas flow in the cavity of its working part. Methods. Determination of the sound pressure level of the engine of a small tractor by mathematical (computer) modeling of the behavior of the exhaust gas flow in the muffler cavity in different frequency ranges. Results. The article analyzes the main sources of noise during the operation of agricultural machinery with internal combustion engines (ICE). On the basis of literature sources and methods, their separate degree of influence on the complex picture of noise pollution of the working space of the operator of a small tractor is established. A comparative analysis of the efficiency of mufflers, created on the generally accepted principles and approaches to the design of such devices. According to the results of previous tests, shortcomings and limitations in the application of design concepts were identified, an additional analysis of external causes and factors was made, and adjustments were made to the method of creating muffler designs. An alternative design approach to the creation of internal combustion engine mufflers of small tractors is proposed and computer modeling of the processes of sound pressure distribution and sound waves in their cavity is performed. Conclusions. 1. A layout diagram of the design of the exhaust muffler, containing a resonator chamber and a shell module, which is made in the form of a three-stage ribbed diffuser of oscillations of the exhaust flow pulses with an additional surface layer of the vibration absorber. The parameters of the exhaust flow of exhaust gases of a typical diesel engine of a small tractor with a capacity of 24 hp are calculated. (pressure - 11652 Pa, acceleration – 90-105 m / s2, frequency - 1950-3300 Hz), which performed computer simulations of the process of gas movement in the muffler cavity of the proposed layout. Optimal design parameters were selected to ensure the maximum possible noise absorption with a body diameter of 150 mm and a length of 600 mm. The calculated sound pressure when working at the crankshaft speed (1700-2000) rpm does not exceed 72 dB. At the same time, the design of the muffler is made in compliance with the requirements for economic feasibility, manufacturability and in accordance with the capabilities of industrial production. A further direction of research is the manufacture of an experimental sample of the muffler and testing for the efficiency of its noise absorption in the conditions of operation of small tractors.
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Danilov, E. A., i S. A. Uryupin. "Generation and detection of sound at the effect of femtosecond pulses on a metal film on a dielectric substrate". Journal of Applied Physics 133, nr 20 (22.05.2023). http://dx.doi.org/10.1063/5.0146517.
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The excitation of sound by a femtosecond laser pulse in a metal layer on a dielectric substrate has been studied. The modulations of the reflection coefficient of the metal, which arise due to the propagation of sound in it, are described in detail. It is shown that, in addition to oscillations corresponding to odd harmonics of sound waves, oscillations corresponding to even harmonics can be present on the profile of the Fourier image of the reflection coefficient change. The efficiency of even harmonic generation depends on the substrate material and the metal film thickness. The dependence of the reflection coefficient change on time has been studied. It has been established that if the electron heat flux reaches the metal–dielectric interface before the energy of the electrons is transferred to the lattice, then modulations are present both due to sound that occurs at the metal–vacuum interface and at the metal–dielectric interface. The wavelength of probe radiation also affects the reflection coefficient change. If real and imaginary parts of the permittivity at the wavelength of probing radiation are comparable in magnitude, then the Fourier image of the reflection coefficient change contains a smaller number of maxima, and the change in the reflection coefficient over time is accompanied by splitting of peaks.