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Results for “spatiotemporal coupling”

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PubMed2026

Elevated water levels drive greenhouse gas mitigation in the riparian zone profile.

Wetlands are critical for climate regulation, with their hyporheic zone serving as sensitive interfaces for groundwater-soil-atmosphere exchange. These zones are active hotspots for carbon-nitrogen cycling and greenhouse gas (GHG) emissions (CO2, CH4, N2O), yet the impact of water level fluctuations on these emissions and their microbial drivers in freshwater wetlands remains poorly understood. This study investigated the spatiotemporal dynamics of GHG emissions and carbon-nitrogen coupling processes along riparian soil profiles of Baiyangdian Lake during water level fluctuations. Employing static chamber measurements, microcosms, quantitative PCR, Metagenome-Assembled genome (MAG) analyses, and Structural Equation Modeling (SEM), we observed that GHG emissions were significantly affected by water level fluctuations. Specifically, CO2 and N2O fluxes, as well as CO2 production potential were significantly lower at high-water-level conditions. Water level also emerged as a key driver of microbial community structure, with Methylococcaceae and Methanosarcinaceae as key regulators of CH4 emission, and Anaeromyxobacteraceae as central to N2O dynamics. A high-quality Methylomirabilales-like MAG, possessing the complete pathway for coupled nitrate reduction and methane oxidation, was identified. Its abundance negatively correlated with water level, suggesting that these C-N coupling bacteria contribute to reducing GHG emissions. This study provides crucial theoretical insights and identifies microbial targets for mitigating wetland GHG emission through hydrological management.

Greenhouse Gases↗

PubMed2003

Mechanism of persistent protein kinase D1 translocation and activation.

The specificity of many signal transduction pathways relies on the spatiotemporal features of each signaling step. G protein-coupled receptor-mediated activation of protein kinases leads to diverse cellular effects. Upon receptor activation, PKD1 and several C-type protein kinases (PKCs), translocate to the plasma membrane and become catalytically active. Here we show that, unlike PKCs, PKD1 remains active at the membrane for hours. The two DAG binding C1 domains of PKD1 have distinct functional roles in targeting and maintaining PKD1 at the plasma membrane. C1A achieves fast, maximal, and reversible translocation, while C1B translocates partially, but persistently, to the plasma membrane. The persistent localization requires the C1B domain of PKD1, which binds Galphaq. We incorporate the kinetics of PKD1 translocation into a three-state model that suggests how PKD1 binding to DAG and Galphaq uniquely encodes frequency-dependent PKD1 signaling.

Cell Membrane↗

PubMed2004

Spatio-temporal expression of the germ cell marker genes MATER, ZAR1, GDF9, BMP15,andVASA in adult bovine tissues, oocytes, and preimplantation embryos.

We have cloned the bovine homologue of Mater (maternal antigen that embryos require) cDNA, potentially the first germ cell-specific maternal-effect gene in this species. The 3297 base-pair longest open reading frame encodes a putative protein of 1098 amino acids with a domain organization similar to its human counterpart. By reverse transcription coupled to polymerase chain reaction, we have analyzed the spatiotemporal expression of MATER, along with other potential markers of germ cells or oocytes: ZAR1 (zygotic arrest 1), GDF9 (growth and differentiation factor 9), BMP15 (bone morphogenetic protein 15), and VASA. In agreement with a preferential oocyte origin, MATER, ZAR1, GDF9, and BMP15 transcripts were detected in the oocyte itself at a much higher level than in the gonads, while no significant expression was detected in our panel of somatic tissues (uterus, heart, spleen, intestine, liver, lung, mammary gland, muscle). In situ hybridization confirmed oocyte-restricted expression of MATER and ZAR1 within the ovary, as early as preantral follicle stages. VASA was highly represented in the testis and the ovary, and still present in the oocyte from antral follicles. Maternal MATER, ZAR1, GDF9, and BMP15 transcripts persisted during oocyte in vitro maturation and fertilization and in preimplantation embryo until the five- to eight-cell or morula stage, but transcription was not reactivated at the time of embryonic genome activation.

Animals↗

PubMed2000

Synchronization and control of coupled ginzburg-landau equations using local coupling

In this paper we discuss the properties of a recently introduced coupling scheme for spatially extended systems based on local spatially averaged coupling signals [see Z. Tasev et al., Int. J. Bifurcation Chaos Appl. Sci. Eng. (to be published); and L. Junge et al., Int. J. Bifurcation Chaos Appl. Sci. Eng. 9, 2265 (1999)]. Using the Ginzburg-Landau model, we performed an extensive numerical examination of this coupling scheme, i.e., a complete scan through the relevant coupling parameters. Furthermore, we demonstrate suppression and control of spatiotemporal chaos, e.g., stabilizing the homogeneous steady state and spatially localized control. As an application all model parameters of the Ginzburg-Landau equation are estimated given only the local information of the system.

Journal Article↗

PubMed2004

Global spatiotemporal order and induced stochastic resonance due to a locally applied signal.

We study the phenomenon of spatiotemporal stochastic resonance (STSR) in a chain of diffusively coupled bistable oscillators. In particular, we examine the situation in which the global STSR response is controlled by a locally applied signal and reveal a wave-front propagation. In order to deepen the understanding of the system dynamics, we introduce, on the time scale of STSR, the study of the effective statistical renormalization of a generic lattice system. Using this technique we provide a criterion for STSR, and predict and observe numerically a bifurcationlike behavior that reflects the difference between the most probable value of the local quasiequilibrium density and its mean value. Our results, tested with a chain of nonlinear oscillators, appear to possess some universal qualities and may stimulate a deeper search for more generic phenomena.

Journal Article↗

PubMed2004

Multifrequency control of Faraday wave patterns.

We show how pattern formation in Faraday waves may be manipulated by varying the harmonic content of the periodic forcing function. Our approach relies on the crucial influence of resonant triad interactions coupling pairs of critical standing wave modes with damped, spatiotemporally resonant modes. Under the assumption of weak damping and forcing, we perform a symmetry-based analysis that reveals the damped modes most relevant for pattern selection, and how the strength of the corresponding triad interactions depends on the forcing frequencies, amplitudes, and phases. In many cases, the further assumption of Hamiltonian structure in the inviscid limit determines whether the given triad interaction has an enhancing or suppressing effect on related patterns. Surprisingly, even for forcing functions with arbitrarily many frequency components, there are at most five frequencies that affect each of the important triad interactions at leading order. The relative phases of those forcing components play a key role, sometimes making the difference between an enhancing and suppressing effect. In numerical examples, we examine the validity of our results for larger values of the damping and forcing. Finally, we apply our findings to one-dimensional periodic patterns obtained with impulsive forcing and to two-dimensional superlattice patterns and quasipatterns obtained with multifrequency forcing.

Journal Article↗

PubMed2004

Experimental synchronization of spatiotemporal disorder.

We report experimental evidence of a time-lag synchronization of spatiotemporal complexity. The experiments were performed on two unidirectionally coupled, nonlinear-optical systems of single-feedback type. Synchronization was investigated for different degrees of complexity of the spontaneous structures, which were analyzed with cross-correlation functions and mutual information. Numerical simulations yield comparable results and throw a light on the impeding role of spatial inhomogeneities.

Journal Article↗

PubMed2004

A new spatiotemporally chaotic cryptosystem and its security and performance analyses.

A one-way-coupled chaotic map lattice is proposed for cryptography of self-synchronizing stream cipher. The system performs basic floating-point analytical computation on real numbers, incorporating auxiliarily with few simple algebraic operations on integer numbers. Parallel encryption (decryption) operations of multiple chaotic sites are conducted. It is observed that the system has high practical security, fast encryption (decryption) speed with software realization, and excellent reliability against strong channel noise, and its overall cryptographic properties are considerably better than both known chaotic cryptosystems and currently used conventional cryptosystems, including the advanced encryption standard.

Models, Statistical↗

PubMed2001

Predetermined recruitment of calcium release sites underlies excitation-contraction coupling in rat atrial myocytes.

Excitation-contraction coupling (E-C coupling) was studied in isolated fluo-3-loaded rat atrial myocytes at 22 and 37 degrees C using rapid confocal microscopy. Within a few milliseconds of electrical excitation, spatially discrete subsarcolemmal Ca2+ signals were initiated. Twenty to forty milliseconds after stimulation the spatial overlap of these Ca2+ signals gave a 'ring' of elevated Ca2+ around the periphery of the cells. However, this ring was not continuous and substantial Ca2+ gradients were observed. The discrete subsarcolemmal Ca2+-release sites, which responded in a reproducible sequence to repetitive depolarisations and displayed the highest frequencies of spontaneous Ca2+ sparks in resting cells, were denoted 'eager sites'. Immunostaining atrial myocytes for type II ryanodine receptors (RyRs) revealed both subsarcolemmal 'junctional' RyRs, and also 'non-junctional' RyRs in the central bulk of the cells. A subset of the junctional RyRs comprises the eager sites. For cells paced in the presence of 1 mM extracellular Ca2+, the response was largely restricted to a subsarcolemmal 'ring', while the central bulk of the cell displayed a approximately 5-fold lower Ca2+ signal. Under these conditions the non-junctional RyRs were only weakly activated during E-C coupling. However, these channels are functional and the Ca2+ stores were at least partially loaded, since substantial homogeneous Ca2+ signals could be stimulated in the central regions of atrial myocytes by application of 2.5 mM caffeine. Neither the location nor activation order of the eager sites was affected by increasing the trigger Ca2+ current (by increasing extracellular Ca2+ to 10 mM) or the sarcoplasmic reticulum (SR) Ca2+ load (following 1 min incubation in 10 mM extracellular Ca2+), although with increased SR Ca2+ load, but not greater Ca2+ influx, the delay between the sequential activation of eager sites was reduced. In addition, increasing the trigger Ca2+ current or the SR Ca2+ load changed the spatial pattern of the Ca2+ response, in that the Ca2+ signal propagated more reliably from the subsarcolemmal initiation sites into the centre of the cell. Due to the greater spatial spread of the Ca2+ signals, the averaged global Ca2+ transients increased by approximately 500 %. We conclude that rat atrial myocytes display a predetermined spatiotemporal pattern of Ca2+ signalling during early E-C coupling. A consistent set of eager Ca2+ release sites with a fixed location and activation order on the junctional SR serve to initiate the cellular response. The short latency for activation of these eager sites suggests that they reflect clusters of RyRs closely coupled to voltage-operated Ca2+ channels in the sarcolemma. Furthermore, their propensity to show spontaneous Ca2+ sparks is consistent with an intrinsically higher sensitivity to Ca2+-induced Ca2+ release. While the subsarcolemmal Ca2+ response can be considered as stereotypic, the central bulk of the cell grades its response in direct proportion to cellular Ca2+ load and Ca2+ influx.

Animals↗

PubMed2001

Correlation properties of binary spatiotemporal chaotic sequences and their application to multiple access communication.

This paper studies the correlation property and the spectral density of the binary spatiotemporal chaotic sequences that are generated by the one-way coupled map lattice. The results show that this kind of chaotic sequences possesses excellent randomlike property and could be used directly in the spread spectrum multiple access (SSMA) communications. The multiple access interference in the additional white Gaussian noise background is then analyzed, and the corresponding formulas are presented. The simulation and computation results indicate that the communication system adopting such spreading sequences possesses as good performance as the one employing Gold sequences. But the former has larger capacity and higher complexity. Therefore, the binary spatiotemporal chaotic sequences are good candidates for the spreading sequences in SSMA communications.

Journal Article↗

PubMed2005

Spatiotemporal coding in an electrochemical oscillatory network.

A network consisting of N relaxation electrochemical oscillators, mutually coupled by all-to-all inhibitory connections, can have (N-1) ! coexisting out-of-phase states, each state being a permutation of a periodic spiking sequence. The modification of the out-of-phase states by shots of laser pulse perturbations is shown. In such networks the phase relation of the oscillators is stored as a coded pattern. The ability of the network to function as a rewritable memory of (N-1) ! different spatiotemporal patterns is demonstrated experimentally for N=4.

Journal Article↗

PubMed2003

Direct interaction and functional coupling between metabotropic glutamate receptor subtype 1 and voltage-sensitive Cav2.1 Ca2+ channel.

Intracellular Ca2+ concentrations ([Ca2+]i) are regulated in a spatiotemporal manner via both entry of extracellular Ca2+ and mobilization of Ca2+ from intracellular stores. Metabotropic glutamate receptor subtype 1 (mGluR1) is a G protein-coupled receptor that stimulates the inositol 1,4,5-trisphosphate-Ca2+ signaling cascade, whereas Cav2.1 is a pore-forming channel protein of P/Q-type voltage-sensitive Ca2+ channels. In this investigation, we showed that mGluR1 and Cav2.1 are colocalized at dendrites of cerebellar Purkinje neurons and form the heteromeric assembly in both the brain and heterologously expressing COS-7 cells. This assembly occurs through the direct interaction between their carboxyl-terminal intracellular domains. Calcium imaging and whole-cell recording showed that mGluR1 inhibits Cav2.1-mediated [Ca2+]i increases and Ba2+ currents in HEK 293 cells expressing Cav2.1 with auxiliary alpha2/delta and beta1 subunits, respectively. This inhibition occurred in a ligand-independent manner and was enhanced by pre-activation of mGluR1 in a ligand-dependent manner. In contrast, simultaneous stimulation of mGluR1 and Cav2.1 induced large [Ca2+]i increases. Furthermore, the temporally regulated inhibition and stimulation of [Ca2+]i increases by mGluR1 and Cav2.1 were observed at dendrites but not soma of cultured Purkinje neurons. These data suggest that the assembly of mGluR1 and Cav2.1 provides the mechanism that ensures spatiotemporal regulation of [Ca2+]i in glutamatergic neurotransmission.

Animals↗

PubMed2004

Spatiotemporal rheochaos in nematic hydrodynamics.

Motivated by recent observations of rheochaos in sheared wormlike micelles, we study the coupled nonlinear partial differential equations for the hydrodynamic velocity and order-parameter fields in a sheared nematogenic fluid. In a suitable parameter range, we find irregular, dynamic shear banding and establish by decisive numerical tests that the chaos we observe in the model is spatiotemporal in nature.

Journal Article↗

PubMed1996

Dynamical behavior of the multiplicative diffusion coupled map lattices.

We report a dynamical study of multiplicative diffusion coupled map lattices with the coupling between the elements only through the bifurcation parameter of the mapping function. We discuss the diffusive process of the lattice from an initially random distribution state to a homogeneous one as well as the stable range of the diffusive homogeneous attractor. For various coupling strengths we find that there are several types of spatiotemporal structures. In addition, the evolution of the lattice into chaos is studied. A largest Lyapunov exponent and a spatial correlation function have been used to characterize the dynamical behavior. (c) 1996 American Institute of Physics.

Journal Article↗

PubMed1998

Noise sustained waves in subexcitable media: From chemical waves to brain waves.

We discuss a novel type of spatiotemporal pattern that can be observed in subexcitable media when coupled to a thermal environment. These patterns have been recently observed in several different types of systems: a subexcitable photosensitive Belousov-Zhabotinsky reaction, hippocampal slices of rat brains, and astrocyte syncytium. In this paper, we introduce the basic concepts of subexcitable media, describe recent experimental observations in chemistry and neurophysiology, and put these observation into context with computer simulations. (c) 1998 American Institute of Physics.

Journal Article↗

PubMed2004

Period doubling cascade in glow discharges: local versus global differential conductivity.

Short planar glow discharges coupled to a resistive layer exhibit a wealth of spontaneous spatiotemporal patterns. Due to similarities with other pattern forming systems that are described by reaction-diffusion models, several authors have tried to derive such models from discharge physics. We investigate the temporal oscillations of the discharge system and find a cascade of period doubling events. This shows that the inner structure of the discharge is more complex than can be described by a two-component reaction-diffusion-model with negative differential conductivity. We also derive an alternative reduced model.

Journal Article↗

PubMed2002

Effects of voluntary blinks on saccades, vergence eye movements, and saccade-vergence interactions in humans.

Blinks are known to change the kinematic properties of horizontal saccades, probably by influencing the saccadic premotor circuit. The neuronal basis of this effect could be explained by changes in the activity of omnipause neurons in the nucleus raphe interpositus or in the saccade-related burst neurons of the superior colliculus. Omnipause neurons cease discharge during both saccades and vergence movements. Because eyelid blinks can influence both sets of neurons, we hypothesized that blinks would influence the kinematic parameters of saccades in all directions, vergence, and saccade-vergence interactions. To test this hypothesis, we investigated binocular eye and lid movements in five normal healthy subjects with the magnetic search coil technique. The subjects performed conjugate horizontal and vertical saccades from gaze straight ahead to targets at 20 degrees up, down, right, or left while either attempting not to blink or voluntarily blinking. While following the same blink instruction, subjects made horizontal vergence eye movements of 7 degrees and combined saccade-vergence movements with a version amplitude of 20 degrees. The movements were performed back and forth from two targets simultaneously presented nearby (38 cm) and more distant (145 cm). Small vertical saccades accompanied most vergence movements. These results show that blinks change the kinematics (saccade duration, peak velocity, peak acceleration, peak deceleration) of not only horizontal but also of vertical saccades, of horizontal vergence eye movements, and of combined saccade-vergence eye movements. Peak velocity, acceleration, and deceleration of eye movements were decreased on the average by 30%, and their duration increased by 43% on the average when they were accompanied by blinks. The blink effect was time dependent with respect to saccade and vergence onset: the greatest effect occurred 100 ms prior to saccade onset, whereas there was no effect when the blink started after saccade onset. The effects of blinks on saccades and vergence, which are tightly coupled to latency, support the hypothesis that blinks cause profound spatiotemporal perturbations of the eye movements by interfering with the normal saccade/vergence premotor circuits. However, the measured effect may to a certain degree but not exclusively be explained by mechanical interference.

Adult↗

PubMed1998

Stochastic resonance in coupled nonlinear dynamic elements.

We investigate the response of a linear chain of diffusively coupled diode resonators under the influence of thermal noise. We also examine the connection between spatiotemporal stochastic resonance and the presence of kink-antikink pairs in the array. The interplay of nucleation rates and kink speeds is briefly addressed. The experimental results are supplemented with simulations on a coupled map lattice. We furthermore present analytical results for the synchronization and signal processing properties of a Phi(4) field theory and explore the effects of various forms of nonlinear coupling. (c) 1998 American Institute of Physics.

Journal Article↗