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Compressible two-fluid flows are difficult to numerically simulate. Indeed, classic conservative finite volume schemes do not preserve the velocity and pressure equilibrium at the two-fluid interface. This leads to oscillations, lack of precision and even, in some liquid-gas simulations, to the crash of the computation. Several cures have been proposed to obtain better schemes (see [1] and included references). The resulting schemes are generally not conservative. Based on ideas of [2], we propose a new Lagrange-Projection scheme. The projection step is based on a random sampling strategy at the interface. The scheme has the following properties: it preserves constant velocity and pressure at the two-fluid interface, it preserves a perfectly sharp interface and it is fully conservative (in a statistical sense). The scheme can be extended to higher space dimensions through Strang dimensional splitting. Finally, it is very simple to implement and thus well adapted to massively parallel GPU computations.

We have studied a time response of electromagnetically induced transparency (EIT) in a rubidium vapor to a rapid variation of optical phase. We have observed a very fast growth of the absorption when the phase of the optical field has been abruptly changed, followed by a slow return to the level of steady-state absorption. The recovery time decreases with increasing optical power. A simple theoretical analysis shows that under our experimental conditions the low power limit of the recovery time is determined by the ground relaxation time. In our case it is defined by a time-of-flight of rubidium atoms through laser beam. The obtained value of the ground state relaxation time is in a good agreement with result of direct measurements by ‘relaxation in the dark’ method. Our technique based on phase dynamics in EIT can be used for investigation of the ground state relaxation and the fast control of EIT.

Focusing on the binary polymer mixture films under the off-critical condition, the phase dynamics and wetting layer formation mechanisms of pattern-directed phase separation are numerically investigated. The simulated results demonstrate that, for different compositions, the polymer mixtures on the strip patterned surface can exhibit various phase morphologies in the strips of the bulk, which can be used to tailor the microscopic structures of films. The evolutions of these phase structures in the strips of the bulk obey almost the same power law with an exponent of 1/3, i.e., the Lifshitz–Slyozov growth law for the films with various off-critical degrees. It is found that the wetting layer thickness near the patterned surface grows logarithmically at the initial stages, just like the wetting layer formation mechanism of the polymer mixture near the surface with an isotropic potential. This revels that only patterning the surface potential may not change the growth law of the wetting layer. The simulated results also indicate that the diffusion of the component in the direction parallel to the surface originates from the edge of the strips.

Based on the semiclassical density-matrix equations, ultrafast probe gain and phase dynamics in bulk semiconductor optical amplifiers excited by a 200 fs Gaussian pump pulse centered at 1,558 nm are numerically investigated and compared over a wide material gain region (1,460–1,650 nm). It is predicted that the recovery time of phase may be longer or shorter than that of gain depending on probe wavelengths. Besides, as functions of probe wavelength, the dynamic gain range and the dynamic phase range have different shapes. Moreover, the wavelength dependence of phase recovery overshoot is illustrated. At last, the probe chirp dynamics and the wavelength dependence of the chirp characteristics are described. These interesting features result from a restriction of the Kramers–Kronig relations and different ways of the competition or cooperation among the effects of spectral-hole burning, carrier heating and two-photon absorption on subpicosecond timescale over the whole concerned band.

Objective To assess factors that might contribute to a delayed sleep schedule in young adults with sub-clinical features of delayed sleep phase disorder. Methods Two groups of 14 young adults (eight women) were compared: one group complaining of a delayed sleep schedule and a control group with an earlier bedtime and no complaint. For one week, each subject maintained a target bedtime reflecting their habitual sleep schedule. Subjects were then admitted to the laboratory for the assessment of circadian phase (dim light melatonin onset), subjective sleepiness, and non-visual light sensitivity. All measures were timed relative to each participant's target bedtime. Non-visual light sensitivity was evaluated using subjective sleepiness and salivary melatonin during 1.5-h exposure to blue light, starting one hour after target bedtime. Results Compared to control subjects, delayed subjects had a later circadian phase and a slower increase of subjective sleepiness in the late evening. There was no group difference in non-visual sensitivity to blue light, but we found a positive correlation between melatonin suppression and circadian phase within the delayed group. Conclusions Our results suggest that a late circadian phase, a slow build-up of sleep need, and an increased circadian sensitivity to blue light contribute to the complaint of a delayed sleep schedule. These findings provide targets for strategies aiming to decreasing the severity of a sleep delay and the negative consequences on daytime functioning and health.

Study of weakly non-linear dynamics of a reaction–super-diffusion system near a Hopf bifurcation by means of fractional analogues of complex Ginzburg-Landau and Kuramoto-Sivashinsky equations is presented. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Adaptive control of a two-dimensional model of a flexible spacecraft with noncolocated sensors and actuators is achieved by output feedback using knowledge of only the system's impulse response. The model is composed of two planar rigid bodies linked by a torsional spring that emulates a multibody spacecraft with base body actuation and appendage pointing. Retrospective cost adaptive control is applied to a command-following problem. The controller uses a finite impulse response filter built from the Markov parameters of the nonminimum-phase (NMP) linearized model. Accordingly, this filter is constructed to contain an estimate of the location of the NMP zero; the filter's order is chosen to correspond to the number of time steps after which the plant's step response becomes positive.

Light is the primary signal that calibrates circadian neural circuits and thus coordinates daily physiological and behavioral rhythms with solar entrainment cues. Drosophila and mammalian circadian circuits consist of diverse populations of cellular oscillators that exhibit a wide range of dynamic light responses, periods, phases, and degrees of synchrony. How heterogeneous circadian circuits can generate robust physiological rhythms while remaining flexible enough to respond to synchronizing stimuli has long remained enigmatic. Cryptochrome is a short-wavelength photoreceptor that is endogenously expressed in approximately half of Drosophila circadian neurons. In a previous study, physiological light response was measured using real-time bioluminescence recordings in Drosophila whole-brain explants, which remain intrinsically light-sensitive. Here we apply analysis of real-time bioluminescence experimental data to show detailed dynamic ensemble representations of whole circadian circuit light entrainment at single neuron resolution. Organotypic whole-brain explants were either maintained in constant darkness (DD) for 6 days or exposed to a phase-advancing light pulse on the second day. We find that stronger circadian oscillators support robust overall circuit rhythmicity in DD, whereas weaker oscillators can be pushed toward transient desynchrony and damped amplitude to facilitate a new state of phase-shifted network synchrony. Additionally, we use mathematical modeling to examine how a network composed of distinct oscillator types can give rise to complex dynamic signatures in DD conditions and in response to simulated light pulses. Simulations suggest that complementary coupling mechanisms and a combination of strong and weak oscillators may enable a robust yet flexible circadian network that promotes both synchrony and entrainment. A more complete understanding of how the properties of oscillators and their signaling mechanisms facilitate their distinct roles in light entrainment may allow us to direct and augment the circadian system to speed recovery from jet lag, shift work, and seasonal affective disorder.

Square-planar high-spin Fe(II) molecular compounds are rare, and until recently, the only four examples of non-macrocyclic or sterically driven molecular compounds of this kind shared a common FeO4 core. The trianionic pincer-type ligand [CF3-ONO]H3 (1) supports the high-spin square-planar Fe(II) complex {[CF3-ONO]FeCl}{Li(Sv)2}2 (2). In the solid state, 2 forms the dimer complex {[CF3-ONO]Fe}2{(μ-Cl)2(μ-LiTHF)4} (3) in 96% yield by simply applying a vacuum or stirring it with pentane for 2 h. A detailed high-frequency electron paramagnetic resonance and field-dependent (57)Fe Mössbauer investigation of 3 revealed a weak antiferromagnetic exchange interaction between the local iron spins which exhibit a zero-field splitting tensor characterized by negative D parameter. In solution, 2 is in equilibrium with the solvento complex {[CF3-ONO]FeCl(THF)}{Li2(Sv)4} (2·Sv) and the dimer 3. A combination of frozen solution (57)Fe Mössbauer spectroscopy and single crystal X-ray crystallography helped elucidate the solvent dependent equilibrium between these three species. The oxidation chemistry of 2·Sv was investigated. Complex 2 reacts readily with the one-electron oxidizing agent CuCl2 to give the Fe(III) complex {[CF3-ONO]FeCl2}{Li(THF)2}2 (4). Also, 2·Sv reacts with 2 equiv of TlPF6 to form the Fe(III) complex [CF3-ONO]Fe(THF)3 (5).

Using a child sample, we examined the effects of the phase of narrow-band electroencephalographic (EEG) activity at stimulus onset on the resultant event-related potentials (ERPs) in an equiprobable auditory Go/NoGo task with a fixed stimulus-onset asynchrony. We used FFT decomposition of the EEG at Cz to assess prestimulus narrow-band EEG activity (in 1 Hz bands from 1 to 13 Hz) for each trial. From the cycle at stimulus onset, trials were sorted into four phases for each of the 13 frequencies. ERPs were derived for each of these from the raw EEG activity at the midline sites. ERP responses were analysed in the context of a simple conceptualisation of orthogonal phase effects (cortical negativity vs. positivity, negative driving vs. positive driving, waxing vs. waning). At a number of frequencies, crossing the traditional frequency bands, the predicted non-random occurrence of phase-defined brain states was confirmed. The preferred states of negativity and negative driving were each associated with more efficient stimulus processing, as reflected in latency and amplitude differences of the N1 and P3 ERP components. The present results confirm the existence of preferred brain states and their impact on the efficiency of brain dynamics involved in perceptual and cognitive processing, and extend their occurrence from adults to children.

The dynamics of the phase difference of counterpropagating waves is studied theoretically and experimentally in the self-modulation oscillation regime in a solid-state ring laser. It is found that in the case of a small enough frequency nonreciprocity of the ring resonator, the phase difference of counterpropagating waves changes within a limited range, performing periodic oscillations with the intensity self-modulation frequency. The instant frequency difference of counterpropagating waves also changes periodically in time; however, its mean value is zero (the frequency locking for counterpropagating waves takes place). The width of the frequency locking region is measured. It is shown that the phase difference of the coupling coefficients considerably affects the phase dynamics. This opens up new possibilities for determining the phase difference of coupling coefficients of counterpropagating waves.

The ultrafast phase dynamics of carriers in Ge quantum dots (QDs) is studied by using photocurrent correlation phase spectroscopy (PCPS) at room temperature. For better understanding the ultrafast phase dynamics of carriers on the sublevels of Ge QDs, the sublevels in Ge QDs are first investigated by Fourier transform infrared photocurrent spectroscopy, and the result shows that there are two sublevels (0.76 and 0.84 eV) in Ge QDs. The ultrafast phase dynamics signals measured by PCPS are well behaved with a smooth wave line and oscillating trailing edge. The dephasing time has been obtained by numerically simulating the PCPS data in terms of optical Bloch equations. The dephasing time () originating in the transition from the sublevel of the Ge QDs to the conduction band is slightly longer than that () originating in the Si band-to-band transition.

The purpose of this investigation was to use relative phase dynamics to evaluate gait in individuals with a reconstructed anterior cruciate ligament (ACL) during walking and running. Relative phase dynamics can describe the coordination strategies between the interacting segments at the lower extremity. Ten subjects who had undergone ACL reconstruction using the central third of their patellar tendon and ten healthy controls walked and ran on a treadmill at a self-selected pace. Relative phase dynamics were calculated for the foot-shank and shank-thigh coordinative relationships. Statistical differences between the groups were noted for the foot-shank relationship (p < 0.05) during both walking and running and for the shank-thigh relationship (p < 0.05) during walking. Our results indicate that current ACL reconstructive techniques may result in altered relative phase dynamics. These changes in relative phase dynamics could be related to a loss of sensory information about joint position and velocity that is typically provided by the intact ACL. Additionally, relative phase adaptations could be a learned response from the early stages of postsurgical rehabilitation. Relative phase dynamics provide quantitative information about the dynamic status of the ACL-reconstructed knee that cannot be gained from the conventional time-series evaluation of gait analysis data. Relative phase dynamics measures should supplement the conventional gait analysis measures that are used today for the clinical evaluation of the functional dynamic stability of the reconstructed knee. The examination of relative phase dynamics could be clinically important for the quantification of new ACL surgical interventions and of patient performance at various stages of rehabilitation. Further research should incorporate relative phase dynamics to understand the influence of ACL reconstruction on coordination and functional patient outcomes.

It has long been considered that the Trans-Mexican Volcanic Belt (TMVB) is related to subduction along the Middle America trench. Within this view, it is expected that the tectonic dynamics of the Cocos plate can be reflected, to some extent, in the Popocatepetl's volcanic activity This work uses detrended fluctuation analysis, a method borrowed from statistical mechanics, to quantify the fractality and autocorrelations in the exhalation sequence of the Popocatepetl. It is found that the autocorrelations exhibit cyclic, non-periodic, dynamics with dominant periods of the order of 0.85 to 1.25 years. Interestingly, it is shown that the occurrence of slow-slip events in Southern (Guerrero and Oaxaca) Mexico coincides with peaks of the autocorrelation cycle of the exhalation sequence. The result suggests the use of the volcano exhalation sequence as a proxy of aseismic events in the Cocos-North American plate boundary. That is, by monitoring the autocorrelation dynamics of the exhalation sequence in the Popocatepetl, one could be able to suspect the occurrence of a slow-slip event in Southern Mexico.

In any physical dynamical system an understanding of both the intensity and phase dynamics can provide an unique insight into the dynamical behaviour observed. A thorough picture of the phase and intensity dynamics of an optical system can greatly aid in understanding the device dynamics from the perspective of fundamental physics as well as providing a deeper insight into device performance. This work details a novel interferometric analysis technique which allows the measurement and visualisation of the complex electric field of a laser source in a time-resolved, single shot format. To demonstrate the effectiveness of this technique, it has been applied to the dynamically rich system of a semiconductor laser undergoing external optical injection, allowing for the first time a direct study of the phase trajectories of the various non-linear dynamical responses observed in such a system. Furthermore a full electric field reconstruction of a fast frequency swept source has also been performed. A time-resolved analysis of this wide bandwidth laser allows direct measurement of many fast time-scale dynamics and a precise calculation of many device parameters which were previously inaccessible. This novel technique allows for previously unobtainable insights into the underlying dynamics of laser systems with many potential applications for this technique in studying future light sources and in gaining further understanding of fundamental laser dynamics.

This paper deals with output synchronization problem in nonlinear multi-agent systems. The main contribution of the paper is to guarantee output synchronization in the network while the dynamics of agents exhibit non-minimum phase behavior. To achieve this goal, a control signal is presented for each agent consisting of two terms. The first term is a linear function of each agent states employed in order to overcome the non-minimum phase dynamics of the multi-agent system, whereas the second term is a function of the output of neighboring agents which provides coupling among agents and guarantees output synchronization in the network. A numerical example is presented to verify the effectiveness of the proposed approach.

The phase dynamics that occur in bulk InGaAsP-InP semiconductor optical amplifiers (SOAs) in response to picosecond pulse excitations at 10 and 40 GHz are studied experimentally and numerically for various amplifier lengths. The time dependencies of the phase changes and of the absolute gain of the amplifier are measured simultaneously. The total phase shifts induced by 1.5-ps pulses at 10 GHz are higher than /spl pi/ in SOAs with active region lengths between 0.5 and 2 mm and exceed 2/spl pi/ in a 1.5-mm-long amplifier. Phase shifts above /spl pi/ are measured at 40 GHz in 1.5- and 2-mm-long SOAs. The dependence of the total phase shift on the amplifier bias current and length and on pump pulse energy is investigated. Numerical simulations based on a comprehensive time-domain SOA model allow us to confirm the experimental results for a wide range of amplifier parameters. In particular, SOAs with lengths up to 5 mm have been modeled, and the calculations suggest that the maximum phase shifts occur in amplifiers of approximately 2-mm length. The phase dynamics measurements are illustrated at the example of an optical time division multiplexing add-drop multiplexer, based on a SLALOM switch, gated by 10- or 40-GHz control pulses. We find that simultaneous good dropping and clearing is possible if the length and the operating conditions of the SOA in the switch are chosen such as to induce a full /spl pi/ phase shift.

Volcanic eruptions involve high-speed turbulent flows of gas and magma mixtures in which peak gas velocities often approach 600 m s−1. Such speeds are well in excess of the slow mixture sound speeds of approximately 150 m s−1 predicted by pseudo-gas theory, in which the gas and magma phases are assumed to be locked to each other; eruptions thus appear to be highly super-sonic. Indeed, flow in the volcanic conduit will choke when it reaches the sound speed and to attain supersonic velocities one must invoke special conduit nozzle shapes. However, the pseudo-gas approximation is a long-wavelength assumption, while choking and acoustic shocks are a short-wavelength effect; thus, the approximation is likely inapplicable for the choking phenomenon. To allow for non-pseudo-gas effects, such as phase separation, in the short-wavelength limit requires a more complete treatment of two-phase eruptions. We therefore develop and explore a model for two-phase, high Reynolds number flow of a compacting suspension of magma particles in a compressible gas. Flow properties, such as mixture density, are controlled both by gas content as well as gas compressibility, both of which vary according to different processes of compaction and compression, respectively. The two phases of the mixture separate because of their different densities, and the interaction forces (turbulent drag and inertial exchange) can be complex. The model is used to examine acoustic-porosity wave propagation and the development of shocks or choking structures in a volcanic conduit. Sound waves in separable mixtures are highly dispersive with fast waves propagating at the pure gas sound speed at small wavelengths, slow waves travelling at the pseudo-gas speed at long wavelengths, and pure attenuation and sound blocking at intermediate wavelengths. As shock fronts in gas density develop they become increasingly short wavelength features and thus will only cause choking if the maximum speed in the flow reaches the pure gas sound speed. Non-linear, finite-amplitude steady-state models of eruptions in a volcanic conduit show that compaction occurs over the magma particle gravitational deceleration height, and either suppresses gas expansion for fast eruptions, or isopycnally collapses the gas volume near the base of the erupting column for slow eruptions. Once compaction ceases, the gas expands toward a shock structure or choking point, which is coincident with a rapid gas acceleration and a high-speed vent eruption. Increased turbulent drag between the gas and particles suppresses compaction effects but greatly sharpens the shock front at the choking point. Although the standard pseudo-gas models predict such choking to occur at low velocities, the full two-phase theory always has choking occur when the gas reaches the pure gas sound speed, in keeping with the sound-speed dispersion analysis. Therefore, the full two-phase theory predicts choking to occur at the pure gas sound speed, which (for water vapour at the relevant high temperatures) is about 700 m s−1. Eruption velocities of 600 m s−1 are therefore fully consistent with the limit imposed by this choking condition, and no special conditions to obtain supersonic eruptions, such as nozzled conduit geometries, are necessary.

Despite its simple mathematical structure, the Sprott E flow displays a chaotic dynamics whose complexity increases with the bifurcation parameter. This complexity shows up in the phase dynamics, which becomes highly incoherent. Such behavior is interpreted as the superposition of the dynamics of several different embedded standard maps.

We examine the mutual coherence and phase dynamics of two solid-state lasers, generated adjacent to each other in a single Nd:YAG rod. The coupling of the lasers is varied by changing the separation of the pump beams. A model is formulated to interpret the experimental results, and theoretical predictions are obtained that are in excellent agreement with the measurements.

The radiation phase dynamics of a solid-state ring laser with a periodic pump modulation operating in a dynamic chaotic regime is studied theoretically and experimentally. It is found that, in the regime of synchronised dynamic chaos, the optical phases of counterpropagating waves change by {pi} in intervals between two adjacent chaotic radiation pulses. It is shown that spontaneous radiation has a significant effect on the chaotic dynamics of the counterpropagating wave intensities, but its effect on the phase dynamics in a solid-state ring laser is negligible. (laser applications and other topics in quantum electronics)

In this note we will introduce in the first section the concept of phase dynamics, followed by an outline of some recent developments associated with the properties of nonlinear phase equations, and we will conclude with an extensive list of references on phase dynamics and closely related subjects including envelope equations, the motion of defects, and the coupling between amplitude and phase equations.

The phase dynamics of the coupled Josephson junctions in the framework of CCJJ and CCJJ+DC models is studied. The current voltage characteristics (CVC) are numerically calculated for the stacks with different number of junctions at different model parameters. We manifest the difference of these models for the branching at I = Ic and in the hysteretic region. The essential difference is observed in the breakpoint region, where the longitudinal plasma wave is created. We discuss the main features of both models, related with the role of the diffusion current between the superconducting layers.

Synchronization in the system of coupled non-identical non-isochronous van der Pol–Duffing oscillators with inertial and dissipative coupling is discussed. Generalized Adler’s equation is obtained and investigated in the presence of all relevant factors affecting the synchronization (non-isochronism of the oscillators, their non-identity, coupling of the dissipative and inertial types). Characteristic symmetries are revealed for the Adler’s equation responsible for equivalence of some of the factors. Numerical study of the parameters space of the initial differential equations is carried out using the method of charts of dynamic regimes in the parameter planes. Results obtained by both these approaches are compared and discussed.

Temperature modulated differential scanning calorimetry (TMDSC) and dynamic mechanical analysis (DMA) are used to calculate cooperative rearranging region (CRR) average sizes for drawn poly(ethylene terephthalate) (PET) with different draw ratios (λ) ranging from λ=1 to 4, according to Donth’s approach. It is shown for both studies that the CRR size decreases when increases, due to the amorphous phase confinement by the crystals generated during the drawing. However, differences observed between the values calculated from TMDSC and DMA investigations are explained by the differences between a mechanical uniaxial dynamic solicitation (DMA) or a thermal solicitation (TMDSC) in terms of cooperative rearrangements at the glass transition.

A one-dimensional reactive transport model including mass, momentum and volume conservation for the solid, aqueous, and gaseous phases is developed to explore the fate of free methane gas in marine sediments. The model assumes steady–state compaction for the solid phase in addition to decoupled gas and aqueous phase transport, instigated by processes such as buoyancy, externally impressed flows and compaction. Chemical species distributions are governed by gas advection, dissolved advection and diffusion as well as by reaction processes, which include organoclastic sulfate reduction, methanogenesis and anaerobic oxidation of methane (AOM). The model is applied to Eckernforde Bay, a shallow-water environment where acoustic profiles confirm a widespread occurrence of year-round biogenic free methane gas within the muddy regions of the sediment, and where subsurface methanogenesis, overlaid by a zone of AOM has been reported. The model results reveal that, under steady-state conditions, upward gas migration is an effective methane transport mechanism from oversaturated to undersaturated intervals of the sediment. Furthermore, sensitivity tests show that when methanogenesis rates increase, the gas flux to the AOM zone becomes progressively more important and may reach values comparable to those of the aqueous methane diffusive flux. Nevertheless, the model also proves that the gas transport rates always remain smaller than the removal rates by combined gaseous methane dissolution and oxidation. Consequently, for the range of environmental conditions investigated here, the AOM zone acts as an efficient subsurface barrier for both aqueous and gaseous methane, preventing methane escape from the sediments to the water column.

Complex continuous wavelet transforms are used to study the dynamics of instantaneous phase difference Δφ between the fluctuations of arterial blood pressure (ABP) and cerebral blood flow velocity (CBFV) in a middle cerebral artery. For healthy individuals, this phase difference changes slowly over time and has an almost uniform distribution for the very low-frequency (0.02–0.07 Hz) part of the spectrum. We quantify phase dynamics with the help of the synchronization index γ = 〈sinΔφ〉2 + 〈cosΔφ〉2that may vary between 0 (uniform distribution of phase differences, so the time series are statistically independent of one another) and 1 (phase locking of ABP and CBFV, so the former drives the latter). For healthy individuals, the group-averaged index γ has two distinct peaks, one at 0.11 Hz [γ = 0.59 ± 0.09] and another at 0.33 Hz (γ = 0.55 ± 0.17). In the very low-frequency range (0.02–0.07 Hz), phase difference variability is an inherent property of an intact autoregulation system. Consequently, the average value of the synchronization parameter in this part of the spectrum is equal to 0.13 ± 0.03. The phase difference variability sheds new light on the nature of cerebral hemodynamics, which so far has been predominantly characterized with the help of the high-pass filter model. In this intrinsically stationary approach, based on the transfer function formalism, the efficient autoregulation is associated with the positive phase shift between oscillations of CBFV and ABP. However, the method is applicable only in the part of the spectrum (0.1–0.3 Hz) where the coherence of these signals is high. We point out that synchrony analysis through the use of wavelet transforms is more general and allows us to study nonstationary aspects of cerebral hemodynamics in the very low-frequency range where the physiological significance of autoregulation is most strongly pronounced.

The peculiarities of the phase dynamics are studied in a ring solid-state laser operating in transient quasi-sinusoidal oscillation regimes of the first and second kinds (QS-1 and QS-2) appearing upon periodic modulation of the pump power. It is shown that recording of a change in the phase difference of counterpropagating waves in the QS-2 regime under certain conditions makes it possible to determine directly the mutual nonreciprocity of the laser resonator.

In this study, we numerically calculate the temperature distribution and the THz phase dynamics in the mesa-structured intrinsic Josephson junctions (IJJs) using the thermal diffusion equation and the Sine–Gordon equation. We observe that the temperature distribution has a broad peak around the center region of the IJJ mesa. Under a high external current, a “hot spot” where the temperature is locally higher than the superconducting critical temperature appears around this region. The transverse Josephson plasma wave is strongly excited by the inhomogeneous temperature distribution in the mesa. This gives rise to intense THz emission.

SUMMARY Aim A major question with regard to the ecology of temperate rain forests in south-central Chile is how pioneer and shade-tolerant tree species coexist in old- growth forests. We explored the correspondence between tree regeneration dynamics and life-history traits to explain the coexistence of these two functional types in stands apparently representing a non-equilibrium mixture. Location This study was conducted in northern ChiloeIsland, Chile (41.6� S, 73.9� W) in a temperate coastal rain forest with no evidence of stand disruption by human impact. Methods We assessed stand structure by sampling all stems within two 50 · 20 m and four 5 · 100 m plots. A 600-m long transect, with 20 uniformly spaced sampling points, was used to quantify seedling and sapling densities, obtain increment cores, and randomly select 10 tree-fall gaps. We used tree-ring analysis to assess establishment periods and to relate the influences of disturbances to the regeneration dynamics of the main canopy species. Results Canopy emergent tree species were the long-lived pioneer Eucryphia cordifolia and the shade-tolerant Aextoxicon punctatum. Shade-tolerant species such as Laureliopsis philippiana and several species of Myrtaceae occupied the main canopy. The stem diameter distribution for E. cordifolia was distinctly unimodal, while for A. punctatum it was multi-modal, with all age classes represented. Myrtaceae accounted for most of the small trees. Most tree seedlings and saplings occurred beneath canopy gaps. Based on tree-ring counts, the largest individuals of A. punctatum and E. cordifolia had minimum ages estimated to be > 350 years and > 286 years, respectively. Shade-tolerant Myrtaceae species and L. philippiana had shorter life spans (< 200 years). Most growth releases, regardless of tree species, were moderate and have occurred continuously since 1750. Main conclusions We suggest that this coastal forest has remained largely free of stand-disrupting disturbances for at least 450 years, without substantial changes in canopy composition. Release patterns are consistent with this hypothesis and suggest that the disturbance regime is dominated by individual tree-fall gaps, with sporadic multiple tree falls. Long life spans, maximum height and differences in shade tolerance provide a basis for understanding the long- term coexistence of pioneer and shade-tolerant tree species in this coastal, old- growth rain forest, despite the rarity of major disturbances.

The motion of monodisperse spherical particles in a heterogeneous medium for the nonisothermal free convection of the carrying viscous incompressible liquid in a cylindrical reactor with nonuniform wall temperature profiles is mathematically simulated. The simulation is based on the simultaneous solution of the Navier-Stokes equations written in terms of Eulerian variables for the carrying liquid in the Boussinesq approximation and the equations written in terms of Lagrange variables for the dispersed particle. The system of Navier-Stokes equations is solved in terms of curl-stream function variables using the alternating direction implicit finite difference scheme. The monotone Samarskii’s approximation is used for the convective terms in the curl equation. The calculated results demonstrate the evolution of the curl, stream function, temperature, and particle trajectory.

In this paper we are concerned with the uniform attractor for a nonautonomous dynamical system related to the Fremond thermo-mechanical model of shape memory alloys. The dynamical system consists of a diffusive equation for the phase proportions coupled with the hyperbolic momentum balance equation, in the case when a damping term is considered in the latter and the temperature field is prescribed. We prove that the solution to the related initial-boundary value problem yields a semiprocess which is continuous on the proper phase space and satisfies a dissipativity property. Then we show the existence of a unique compact and connected uniform attractor for the system.

Udgivelsesdato: OCT 22 2000 Low-energy and high-energy collision induced dissociation techniques are used to study the dissociation behavior of the gaseous Pt(CN)(6)(2-) and Pt(CN)(4)(2-) dianion complexes in order to probe the smallest stable dianion complex. Loss of neutral molecules from Pt(CN)(6)(2-) occurs resulting in Pt(CN)(5)(2-) and Pt(CN)(4)(2-), but no indication of the existence of Pt(CN)(3)(2-) was found. This indicates that the lifetime of Pt(CN)(3)(2-) is less than 4 mus (the flight time from the collision region to the detector). In contrast, all monoanion platinum-cyanide complexes were observed, i.e., Pt(CN)(n)(-) (n=1-6). The kinetic energy released in processes where monoanions are formed is much lower than the barrier height for the reverse reaction (>1.5 eV), which indicates that electron detachment is involved, e.g., Pt(CN)(3)(-) and CN- are not formed in the same dynamical process from Pt(CN)(4)(2-), or that the dynamics of the dissociation process is slow. For comparison, the Ru(bipy)(3)(2+)*--> [Ru(bipy)(2)-H](+)+bipyH(+) reaction is associated with a kinetic-energy release of similar to0.3 eV (bipy=2,2(')-bipyridine). (C) 2000 American Institute of Physics. [S0021-9606(00)00240-3].

The assumption that a solar-heliospheric storm has five phases is formulated based on the storm that occurred in October 2003. The first phase: slow (between solar rotations) convergent motions of photospheric sources of large-scale open solar fields (LOFs) with generation of active regions (ARs) between these fields. The second phase: magnetic energy pumping with adjustment of zero lines of the photospheric magnetic field in AR to the configuration of the LOF sector (subsector) boundaries. The third phase: AR destabilization with ordering of the complex of sporadic phenomena near ARs parallel to the zero line and fragments of the nearest LOF boundary. The fourth phase: propagation of disturbances in the near-Sun space with ordering relative to the LOF boundaries. The fifth phase: propagation of a coronal mass ejection (CME) in the inner heliosphere in the case when the axial axis of a magnetic cloud in CME is parallel to the LOF boundary and to the zero line in AR. Original results of LOF modeling and a number of substantial results of the known advanced studies of individual aspects of this storm are used to justify this dynamics as applied to the storm of October 28–30. Specific contents and features of each storm phases are presented. The specific feature of the first phase, responsible for the storm space-time scales and intensity, consisted in the displacement of the entire LOF negative magnetic flux (∼5 × 1022 μs) from the north pole to the south with flowing around a midlatitude obstacle and with zonal convergent motions of LOF. The assumption of the AR configuration adjustment (the second phase) and ordering of disturbances (the third–five phases) during this storm near the subsector boundary between LOFs of identical polarity has been confirmed. It is noted that the pulse phase of the AR 0486 flare, coronal waves, and dimmings along the subsector boundary and the southwestern LOF “dam” joining ARs 0486 and 0484 (superposition of the third and fourth phases) originated almost simultaneously. The two-component disturbance structure is confirmed: halo-type CME with the axis along the LOF subsector boundary and a bright local ejection of magnetic plasma from the region above the southwestern LOF dam.

Recently, physiological findings have suggested the existence of an integrated regulatory mechanism for sleep-wake rhythms, as follows. Homeostatic regulation of the sleep-wake pattern and body temperature involves circadian oscillators and the history of activity patterns. In addition, the rest-activity pattern can modulate the dynamics of circadian oscillators via feedback mechanisms. We have developed models of sleep-wake rhythms based on the thermoregulatory function of sleep and the multi-oscillator mechanism with feedback. The former model is tentatively called the “thermoregulatory model” and the latter the “multi-oscillator model”. The application of the thermoregulatory model is confined to internally or externally entrained situations in which steady circadian oscillation and fixed-phase relationships between the oscillators can be expected to be retained. On the other hand, prediction by the multi-oscillator model is confined to the dynamics of oscillator phase, since the model consists of phase oscillators without amplitude. Making use of the mutual complementarity of these two models, an integrated model of the regulatory mechanism of sleep-wake rhythms was obtained by combining them. Although the integrated model could be valid under conditions of concurrency in which the sleep-wake/rest-activity patterns of the two models can be considered rhythmic and synchronized, the results of a simulation show that the model can be applied to predict the behavior of sleepiness as well as circadian oscillators in a wide variety of situations, such as internally or externally entrained steady states, trans-meridian flight and rotating shift work. The integrated model could provide a general framework for exploring possible physiological and dynamical regulatory mechanisms of sleep-wake rhythms as well as appropriate design of work schedules.

We study travelling wave solutions describing non-isothermal subsonic phase transitions in a van der Waals fluid. We apply the center manifold method and establish the existence of viscosity-capillarity profiles for small viscosity, large heat conduction, and large heat capacity.

Femtosecond electron diffraction (FED) is a new technique within the still-developing field of ultrafast diffraction. This paper presents an outline of the basic features of FED, including a brief history of its development in terms of the technical challenges of working with femtosecond electron pulses and the ultrathin samples required. Application of FED to melting in aluminium and gold excited by intense femtosecond laser pulses will be discussed. The interplay of experiment and theory will be explored, particularly with respect to molecular dynamics simulations of the same processes we experimentally observe. Homogeneous nucleation emerges as an important melting mechanism under the strongly-driving conditions that we employ. Future applications of FED will be discussed in terms of progress to date.

Temporal cavity solitons (CSs) enable the generation of coherent Kerr frequency combs with a broad bandwidth. Here we derive analytically and numerically the relationship between the carrier-envelope-phase (CEP) slip of CSs and the pump phase detuning. To preserve the stability of CSs, CEP slips always equal the pump phase detuning. Since the CEP slip for solitons has a contribution from the Kerr effect, the locking between the CEP slip and pump phase detuning results in a universal constraint on the peak power for CSs. The CEP dynamics is also found to affect the stability of CSs. When the CEP slip fails to follow the pump phase detuning, CSs become unstable, exhibiting periodic or chaotic breathing. Our results can be important for the self-referencing of Kerr frequency combs.

In this paper a new approach for studying slow transients, such as electromechanical transients, using three phase models of power systems is presented. Typically programs used for studying slow transients assume a positive sequence network model, limiting their application to the study of balanced power systems. While electromagnetic simulation software can be used for studying slow transients in unbalanced networks, their application to large systems can be resource and time intensive. The approach presented here overcomes the aforementioned limitations of existing software and provides a means for studying slow transients using complete three phase models of the electric network. Of the many potential applications of the approach presented, evaluating the impact of Distributed Generation (DG), such as rooftop solar photovoltaic (PV) based DG, on the stability of the electric grid is important particularly for utilities with high penetration of DG.

The process of socialization is structured by the life course of childhood; the knowledge society transforms the life phases of childhood as well as their interplay. This chapter analyses the changes in the phases of childhood, from toddler to the young adult, as well as changes in the family and peer group. The emphasis on the first years of life is related to the need for a good start in the educational society.

We investigate the quantum-phase dynamics of a dissipative molecular system interacting with a single-mode amplitude-squeezed field (with a sub-Poissonian photon-number distribution) using the Monte Carlo wave-function method. As quantum dissipation, we consider molecular coherent (phase) and population relaxations, which are caused by nuclear vibration, and cavity relaxation (the dissipation of an internal single mode to outer mode). In this study, we elucidate the effects of these dissipations on the unique quantum dynamical behaviors of this coupled system, e.g., collapse-revival behavior of Rabi oscillations, using the quasiprobability (Q function) distribution of a single-mode field and the off-diagonal molecular density matrix. It is found that although the amplitude-squeezed field exhibits a distinct revival with larger amplitudes of molecular population in the presence of the molecular phase and population relaxations as compared to the coherent field, a very slight cavity relaxation suppresses the revival of molecular population and the increase in the magnitude of off-diagonal molecular density matrices during the quiescent region in the amplitude-squeezed field case more significantly than in the coherent field case. These features are shown to be closely related to the difference in the dynamics of Q function distributions between amplitude-squeezed and coherent fields.

This paper investigates four control architectures that use adaptive control to follow step, ramp, and harmonic roll-angle commands for a linearized aircraft model with an unknown transition from minimum-phase to nonminimum-phase (NMP) dynamics. In particular, we consider retrospective cost adaptive control (RCAC) with 1) a command-feedforward control architecture; 2) an output-feedback control architecture; 3) a centralized control architecture that uses both command feedforward and output feedback; and 4) a decentralized control architecture that uses both command feedforward and output feedback. For baseline tests, we assume that the location of the NMP zero is known. The goal of this work is to improve the transient response and rate of convergence. Numerical testing shows that RCAC with the decentralized control architecture using command feedforward and output feedback gives the fastest convergence. Furthermore, resetting controller coefficients at the start of the transition improves the transient response.

The existing model of the LOCSET technique for the active phase synchronization of fiber laser arrays (T. Shay, Opt. Express, 2006) is extended to include relevant physical properties of the system, such as inherent optical path differences (OPD), line-width and group velocity dispersion (GVD), and we also include phase “jitter” of the master oscillator’s output in the model, which in experiments is implemented to induce spectral broadening for suppression of nonlinear frequency conversion. Linearization of the phase error signal, which incorrectly predicts convergence to a synchronous equilibrium state, is not performed. Instead, the closed-loop control dynamics are shown to be described by differential equations of Kuramoto type when phase corrector response dynamics are negligible. Linear stability analysis indicates that there is always one and no more than one dynamically stable state. The latter is shown to be normally synchronous, except when strong “jitter” is applied. A Liapounov function is found as subject to the validity of certain symmetry conditions.

In this work, the mode analysis technique of complex networks nonlinear selfoscillatory vortex-based spin-torque nano-oscillattors (STNOs) with nonidentity and nonisochrony is developed. We construct adjacency matrices of different type of networks and calculate the normal modes. After the calculation of normal modes we shift to truncated equations for slowly varying amplitudes and phases in the normal coordinates using generalized quasi-Hamiltonian approach. Finally, we present the phase dynamics based on the Kuramotoapproach and compare different networks to the ability of synchronization.

In the present paper, we derive phase equations for dynamical equations describing spatio-temporal dynamics in non-locally distributed systems. In the case of the spatial modulation of a periodic pattern, the phase equation is derived by carring out a suitable spatial average. The resulting equation has a structure with a generalized form that includes the Cahn-Hilliard equation. We also find that the phase equation for an oscillatory medium has the structure of a generalized form of the Kuramoto-Sivashinsky equation, implying the possibility of a Benjamin-Feir-type instability.

We investigate the relaxation effects on the dynamics of two-component dilute gas Bose-Einstein condensates (BEC) with relatively different two-body interactions and Josephson couplings between the two components. Three types of relaxation effects, i.e., one- and three-body losses and a pure phase relaxation caused by elastic two-body collision between condensed and noncondensed atoms, are examined on the dynamical behavior of a macroscopic superposition, i.e., Schrodinger cat state, of two states with atom-number differences between the two components, which is known to be created by the time evolution in certain parameter regimes. Although three-body losses show a relatively large suppression of the revival behavior of Schrodinger cat state and the Pegg-Barnett phase-difference distribution between the two components for a small-size Schrodinger cat state, one- and three-body loss effects are not shown to directly depend on the size of Schrodinger cat state. In contrast, the pure-phase relaxation effects, causing a reduction of phase-difference distribution and then decaying the Schrodinger cat state, significantly increase with the increase of the size of Schrodinger cat state. These features suggest that a detection of damped collapse-revival behavior is highly possible for medium-size Schrodinger cat states in small-size two-component BECs.

The plastic crystal phase forming N-methyl-N-propylpyrrolidinium tetrafluoroborate organic salt (P13BF4) was combined with 2, 5 and 10 wt.% poly(vinyl pyrrolidone) (PVP). The ternary 2 wt.% PVP/2 wt.% LiBF4/P13BF4 was also investigated. Thermal analysis, conductivity, optical thermomicroscopy, and Nuclear Magnetic Resonance (11B, 19F, 1H, 7Li) were used to probe the fundamental transport processes. Both the onset of phase I and the final melting temperature were reduced with increasing additions of PVP. Conductivity in phase I was 2.6 × 10− 4 S cm− 1 5.2 × 10− 4 S cm− 1 1.1 × 10− 4 S cm− 1 and 3.9 × 10− 5 S cm− 1 for 0, 2, 5 and 10 wt.%PVP/P13BF4, respectively. Doping with 2 wt.% LiBF4 increased the conductivity by up to an order of magnitude in phase II. Further additions of 2 wt.% PVP slightly reduced the conductivity, although it remained higher than for pure P13BF4.

We describe the phase dynamics of a timing extraction system based on direct optical injection locking of a multifrequency oscillator employing an InGaAs/InP heterojunction bipolar phototransistor. We present a general model for the locking range, jitter transfer function, and output phase noise. The model is confirmed by a series of locking experiments. We consider first fundamental timing extraction, that is, a 10-GHz oscillator extracting the clock from a 10-Gbit/s data stream. Second, we address superharmonic timing extraction where 40-Gbit/s data lock the fourth harmonic of the 10-GHz oscillator. In the superharmonic timing extraction case, a clock is extracted at 40 GHz as well as its subharmonics at 10, 20, and 30 GHz.

Nonphotic entrainment of an overt sleep-wake rhythm and a circadian pacemaker–driving temperature/melatonin rhythm suggests existence of feedback mechanisms in the human circadian system. In this study, the authors constructed a phase dynamics model that consisted of two oscillators driving temperature/melatonin and sleep-wake rhythms, and an additional oscillator generating an overt sleep-wake rhythm. The feedback mechanism was implemented by modifying couplings between the constituent oscillators according to the history of correlations between them. The model successfully simulated the behavior of human circadian rhythms in response to forced rest-activity schedules under free-run situations: the sleep-wake rhythm is reentrained with the circadian pacemaker after release from the schedule, there is a critical period for the schedule to fully entrain the sleep-wake rhythm, and the forced rest-activity schedule can entrain the circadian pacemaker with the aid of exercise. The behavior of human circadian rhythms was reproduced with variations in only a few model parameters. Because conventional models are unable to reproduce the experimental results concerned here, it was suggested that the feedback mechanisms included in this model underlie nonphotic entrainment of human circadian rhythms.

This paper presents an approach for developing an experimentally validated dynamic multisegment model to simulate human flight-phase dynamics and multijoint control. Modeling and experimental techniques were integrated to systematically examine the contribution of multiple error sources to the accuracy of the model and to determine the complexity of a model that adequately emulates the dynamic behavior at the total-body and multijoint levels during flight. The accuracy of the model and of the experimental data was assessed using an inverse dynamics simulation of flight-phase motion for two representative cases: (i) a physical model released from a bar and (ii) a gymnast performing a layout dismount from a bar. Multijoint models with varying numbers of segments were assessed in order to determine the complexity of the model that adequately simulates the flight-phase task. A five-segment model was found to adequately simulate the layout dismount performed by the gymnast. The error introduced during modeling and digitizing contributed to an apparent violation of the conservation law manifested as large external forces acting on the nonactuated joints. These results demonstrate the need to reduce sources of error prior to testing hypotheses regarding feedforward and feedback components of the multijoint control system. The proposed approach for quantifying sources of error provides a crucial step that is required in the development of experimentally based dynamic models designed to examine and test hypotheses regarding multijoint control logic.