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2018 FEB 22 (NewsRx) -- By a News Reporter-Staff News Editor at Women's Health Weekly -- A new study on Oncology - Breast Cancer is now available. According to news [...]

Intrinsic optical signal (IOS) imaging promises a noninvasive method for objective assessment of retinal function. This study demonstrates concurrent optical coherence tomography (OCT) of amplitude-IOS and phase-IOS changes in human photoreceptors. A new procedure for differential-phase-mapping (DPM) is validated to enable depth-resolved phase-IOS imaging. Dynamic OCT revealed rapid amplitude-IOS and phase-IOS changes, which occur almost right away after the stimulus onset. These IOS changes were predominantly observed within the photoreceptor outer segment (OS), particularly two boundaries connecting to the inner segment and retinal pigment epithelium. The comparative analysis supports that both amplitude-IOS and phase-IOS attribute to transient OS morphological change associated with phototransduction activation in retinal photoreceptors. A simulation modeling is proposed to discuss the relationship between the photoreceptor OS length and phase-IOS changes.

When a solute molecule is placed in solution, is it acceptable to presume that its electronic structure is essentially the same as that in the gas phase? In this paper, we address this question from a simulation perspective for the case of the sodium dimer cation (Na2+) molecule in both liquid Ar and liquid tetrahydrofuran (THF). In previous work, we showed that, when local specific interactions between a solute and solvent are energetically on the order of a hydrogen bond, the solvent can become part of the chemical identity of the solute. Here, using mixed quantum/classical molecular dynamics simulations, we see that, for the Na2+molecule, solute–solvent interactions lead to two stable, chemically distinct coordination states (Na(THF)4–Na(THF)5+and Na(THF)5–Na(THF)5+) that are not only stable themselves as gas-phase molecules but that also have a completely new electronic structure with important implications for the excited-state photodissociation of this molecule in the condensed phase. Furthermore, we show through a set of comparative classical simulations that treating the solute’s bonding electron explicitly quantum mechanically is necessary to understand both the ground-state dynamics and chemical identity of this simple diatomic molecule; even use of the quantum-derived potential of mean force is insufficient to describe the behavior of the molecule classically. Finally, we calculate the results of a proposed transient hole-burning experiment that could be used to spectroscopically disentangle the presence of the different coordination states.

A study conducted by the Russian Academy of Sciences in St. Petersburg explores the application of nonlinear dynamics methods to analyze interactions in biological rhythms related to the respiratory, cardiovascular, and nervous systems. The researchers found phase synchronization between blood pressure and respiratory fluctuations in response to external pain stimulation. They also observed a predominantly unidirectional influence of respiratory rhythm fluctuations on blood pressure variability, as well as a bidirectional relationship between neuronal and blood pressure variability. The study concludes that the time of influence of blood pressure variability on neuronal variability is reduced compared to the reverse. This research has been peer-reviewed and provides valuable insights into the relationships between physiological rhythms. [Extracted from the article]

This paper investigates the linear and non-linear instabilities during evaporation of liquid layers and droplets by means of two-phase 3D direct numerical simulations. The interface is open to the atmosphere under the consideration that vapour diffusion is the rate- limiting mechanism for evaporation. In both configurations, the vapour-liquid interface is prone to travelling thermal instabilities, i.e., hydrothermal waves (HTWs), due to the presence of temperature gradients along the interface. We have already shown in our recent work 7 that under saturated conditions (negligible evaporation) the HTWs additionally give rise to interface deformations of similar features, i.e., physical waves. We have also demonstrated 8 that phase change plays a dual role through its effect on these instabilities: the latent energy required during the evaporation process tends to inhibit the HTWs while the accompanying level reduction enhances the physical waves by minimizing the role of gravity. The dynamics of the gas phase are also discussed. We have also established that the HTW-induced convective patterns in the gas along with the travelling nature of the instabilities have a significant impact on the local evaporation flux and the vapour distribution above the interface. The Marangoni effect plays a major role in the vapour distribution generating a vacuum effect in the warm region and vapour accumulations at the cold boundary capable of inverting the phase change, i.e., the capillary flow can lead to local condensation. These results provide evidence of the inefficiencies of the traditional phase change models based on pure vapour diffusion to capture the dynamics of thermocapillary flows. To conclude, we also present results of a parallel investigation focusing on three-dimensional phenomena on evaporating sessile drops placed on heated substrates.

We have studied the phase dynamics in an oscillatory chemical system (Belousov−Zhabotinsky reaction). The phase distribution and isophase lines in the 2D phase space were reconstructed. The dynamics proved to be well described in terms of the Burgers equation. The phase dependence of the coefficients of the equation was taken into account to estimate the region of the applicability of the Burgers equation.

DNA supercoils are generated in genome regulation processes such as transcription and replication and provide mechanical feedback to such processes. Under tension, a DNA supercoil can present a coexistence state of plectonemic and stretched phases. Experiments have revealed the dynamic behaviors of plectonemes, e.g., diffusion, nucleation, and hopping. To represent these dynamics with conformational changes, we demonstrated first the fast dynamics on the DNA to reach torque equilibrium within the plectonemic and stretched phases, and then identified the two-phase boundaries as collective slow variables to describe the essential dynamics. According to the timescale separation demonstrated here, we developed a two-phase model on the dynamics of DNA supercoiling, which can capture physiologically relevant events across timescales of several orders of magnitudes. In this model, we systematically characterized the slow dynamics between the two phases and compared the numerical results with those from the DNA polymer physics-based worm-like chain model. The supercoiling dynamics, including the nucleation, diffusion, and hopping of plectonemes, have been well represented and reproduced, using the two-phase dynamic model, at trivial computational costs. Our current developments, therefore, can be implemented to explore multiscale physical mechanisms of the DNA supercoiling-dependent physiological processes.

We investigate the dynamics of probability distributions of an initially one-mode coherent field interacting with a four-state molecular system, which is a single magnet with a tunneling across an anisotropic barrier, using a numerically exact approach. The population for each state, the phase properties of and , and ), the entropy are calculated for a model system. The model predicts that the molecule and field become asymptotically disentangled at half of the revival time, and that optical Schrödinger-cat and magnetic Schrödinger-cat states are generated.

Recently there has been a surge of new interest in three-dimensional wake patterns. In the present work, we have devised a method to control the spanwise end conditions and wake patterns using “end suction”, which is both continuously-variable and admits transient control. Classical steady-state patterns, such as parallel or oblique shedding or the “chevron” patterns are simply induced. The wake, at a given Reynolds number, is receptive to a continuous range of oblique shedding angles (?), rather than to discrete angles, and there is excellent agreement with the “cos ?” formula for oblique-shedding frequencies. We show that the laminar shedding regime exists up to Reynolds numbers (Re) of 205, and that the immense disparity among reported critical Re for wake transition (Re = 140–190) can be explained in terms of spanwise end contamination. Our transient experiments have resulted in the discovery of new phenomena such as “phase shocks” and “phase expansions”, which can be explained in terms of a simple model assuming constant normal wavelength of the wake pattern. Peter Monkewitz (Lausanne) also predicts such transient phenomena from a Guinzburg-Landau model for the wake.

The purpose of this study was to determine the effect of varying prosthetic shank mass, while maintaining the mass centre location and moment of inertia, on the swing phase kinematics, kinetics and hip muscular effort of free speed above-knee (AK) amputee gait. Six AK amputees, wearing similar prosthetic designs, had three load conditions applied to their prosthetic shank: 1) Load 0-unloaded (X - 39.1% sound shank mass), 2) Load 1-75%, and 3) Load 2-100% sound leg mass. Despite increases in shank mass from 1.33 to 3.37 kg the AK amputee was able to maintain a consistent swing time and walking speed. As load increased, there were significant changes in the maximum knee and hip displacements, as well as phasic shifting. The prosthetic knee Resultant Joint Moment (RJM) was negligible while the shank was accelerating (periods 1 and 2), but was a major contributor during shank deceleration (periods 3 and 4). During periods 1 and 2 the principle contributors to the shank acceleration (forces resisting excessive knee flexion) were the gravitational moment (S-G) and the moment due to thigh angular acceleration (S-AT). During the periods of shank acceleration (sections 1 and 2), there was not a significant increase in the hip muscular effort. However, during sections 3 and4, the periods associated with shank deceleration, there were siginficant increases in the hip muscular effort. The hip muscular effort for the complete swing phase increased as load increased by 36.7% and 71.3% for loads 1 and 2. Despite the significant increases in hip muscular effort, four of the six subjects preferred load 1 condition.

The wavelength and the bubble separation diameter and frequency have been measured for the film boiling of liquid nitrogen on a thin horizontal wire at acceleration loads ?=375. A description of the process is given. The results obtained are compared with the available experimental and theoretical data.

Quasi-elastic light scattering of Carnauba wax in the liquid phase is done in a homodyne setup and is interpreted as due partially to polarized clusters. A dynamics model is proposed, and effective parameters are obtained in the 85–130°C temperature range. Some evidence exists that the local field seen by a polarized cluster is much higher than the applied static electric field.

Collisions lead to the collapse and revival of the interference fringes between two atomic Bose–Einstein condensates. We study the collapses and revivals of the relative phase between the condensates for two different initial states. One state invokes Bose–broken symmetry allowing us to write the wavefunction as a superposition of total number (of both condensates) states whereas the other does not.

The length dynamics both of microtubule-associated protein (MAP)-rich and MAP-depleted bovine brain microtubules were examined at polymer mass steady state. In both preparations, the microtubules exhibited length redistributions shortly after polymer mass steady state was attained. With time, however, both populations relaxed to a state in which no further changes in length distributions could be detected. Shearing the microtubules or diluting the microtubule suspensions transiently increased the extent to which microtubule length redistributions occurred, but again the microtubules relaxed to a state in which changes in the polymer length distributions were not detected. Under steady-state conditions of constant polymer mass and stable microtubule length distribution, both MAP-rich and MAP-depleted microtubules exhibited behavior consistent with treadmilling. MAPs strongly suppressed the magnitude of length redistributions and the steady-state treadmilling rates. These data indicate that the inherent tendency of microtubules in vitro is to relax to a steady state in which net changes in the microtubule length distributions are zero. If the basis of the observed length redistributions is the spontaneous loss and regain of GTP-tubulin ("GTP caps") at microtubule ends, then in order to account for stable length distributions the microtubule ends must reside in the capped state far longer than in the uncapped state, and uncapped microtubule ends must be rapidly recapped. The data suggest that microtubules in cells may have an inherent tendency to remain in the polymerized state, and that microtubule disassembly must be induced actively.

A holocinematography system based on the copper vapor laser is described where a series of spatially multiplex holograms is recorded in rapid succession (up to 10 kHz).

Quasi-elastic light scattering of carnauba wax in the liquid phase is obtained in a heterodyne setup, and dynamic processes are analyzed through electrophoresis. Nonspherical polar clusters are found, containing a net electrical charge. An applied square-wave electric field induces drift and rotation of these clusters. These effects are dependent on strength and frequency of the applied electric field. At 373 K and in the low frequency limit the local electric field strength is approximately 70 times the strength of the applied one. This enhancement is believed to be caused by collective orientation of the clusters. The electrophoretic mobility is 1.1 × 10^−12 m^2/V sec in the high frequency limit and 7.4 × 10^−11 m^2/V sec in the low frequency limit. The electric dipole moment is 6.3 × 10^−16N^−1/2 m^−1/2 where N is the cluster density/cubic meter and the net charge is about one or two elementary charges.

First order phase reduced model is a good approximation of the dynamics of forced nonlinear oscillators near its limit cycle. The phase evolution is determined by the unforced frequency, the forcing term, and the phase response curve (PRC). Such models arise in biological oscillations such as in circadian rhythm, neural signaling, heart beat, etc. This technical note focuses on the phase regulation of the circadian rhythm using light intensity as the input. Though the model is simple, the circle topology of the state space needs to be carefully addressed. The most common entrainment method is to use a periodic input, such as in our daily light-dark cycle. We obtain the complete stable entrainment condition based on the entraiment input and the PRC. Motivated by the jet-lag problem, we also consider the minimum time entrainment control to achieve a specified phase shift. Application of the Pontryagin Minimum Principle leads to an efficient solution strategy for the optimal control, without solving the two-point boundary value problem. The optimal control may be further represented as a feedback control law based on the current and desired phases. Our analysis allows the answer to questions such as: When traveling from New York to Paris, is it faster to use light to shift the phase forward by 6 hours or delay the phase by 18 hours? The answer is somewhat counter-intuitive—delaying by 18 hours requires less time. The general answer depends on the light intensity level and the shape of the PRC. PRCs for human and Drosophila from the literature are used to illustrate the results. [ABSTRACT FROM PUBLISHER]

The Euclidean invariant equation of motion is derived for a deformed periodic pattern exhibited as a solution of a general nonlinear evolution equation. The formalism is not restricted to the vicinity of the instability threshold, above which the spatially uniform state becomes unstable and a non-propagating periodic structure is continuously formed. The ratio of the basic period to the characteristic length of the deformation is the only smallness parameter in the theory. Thus as far as the modulation is sufficiently smooth, one can develop a systematic way of constructing the non-linear phase dynamics.

Nonlinear phase dynamics of weakly unstable two-dimensional periodic patterns is studied. Four distinct physical situations are specifically considered. They correspond to the Eckhaus instability and zig-zag instability occurring in each of propagating and non-propagating patterns. Consequently, four prototype partial differential equations for phase function are obtained. Their derivation is totally based on symmetry- and scaling arguments. A simple interpretation of the origin of nonlinearity is given. Although the main part of the present theory is phenomenological, a more rigorous asymptonic theory is also developed for reaction-diffusion eqations.

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 study the Ginzburg-Landau equations and the corresponding phase equations to investigate the wavelength changing process through the Eckhaus instability and the transition from a phase turbulence to an amplitude turbulence. A large deformation of amplitude is necessary for the transitions and so the phase description expressing slow modulation is broken down. We show by some numerical simulations what takes place in the phase equations at the transitions.

We study different types of long wavelength phase modulation and localized modes in the dissipative media described by the Ginzburg-Landau type amplitude equations. We derive nonlinear phase equations for the phase instabilities and investigate their behaviors. When the phase description breaks down, phase slip process occurs and topologically different states come out. In a certain parameter range localized solutions or solitonlike solutions appear as stable solutions to the amplitude equations.

The standing wave solution to the coupled complex Ginzburg-Landau equations exhibits phase instabilities. The coupled Benney equations are derived near the phase instability points. The dynamical behaviors of the coupled Benney equations are numerically investigated.

The dynamic properties of a pure 1D incommensurate CDW system in an electric field are reexamined for the non-relativistic (Lee-Rice-Anderson) model, as well as the one of a relativistic (R) form. The effective Lagrangians of the system and the equations of current acceleration of the two models coincide with each other as expected at least at zero temperature. In the R model the current acceleration equation is a consequence of the chiral anomaly inherent to the 1 + 1 Dirac (electron) field. In the non-R model, on the other hand, the same equation is compatible with the conservation law of chiral charge. We also discuss how to deal with the chiral anomaly of the R model in the phase Hamiltonian method.

A new class of superfluids and superconductors with spatially periodic modulation of the superfluid density is arising1–12. It might be related to the supersolid phase of matter, in which the spontaneous breaking of gauge and translational symmetries leads to a spatially modulated macroscopic wavefunction13–16. This relation was recognized only in some cases1,2,5–9and there is the need for a universal property quantifying the differences between supersolids and ordinary matter, such as the superfluid fraction, which measures the reduction in superfluid stiffness resulting from the spatial modulation16–18. The superfluid fraction was introduced long ago16, but it has not yet been assessed experimentally. Here we demonstrate an innovative method to measure the superfluid fraction based on the Josephson effect, a ubiquitous phenomenon associated with the presence of a physical barrier between two superfluids or superconductors19, which might also be expected for supersolids20, owing to the spatial modulation. We demonstrate that individual cells of a supersolid can sustain Josephson oscillations and we show that, from the current–phase dynamics, we can derive directly the superfluid fraction. Our study of a cold-atom dipolar supersolid7reveals a relatively large sub-unity superfluid fraction that makes realistic the study of previously unknown phenomena such as partially quantized vortices and supercurrents16–18. Our results open a new direction of research that may unify the description of all supersolid-like systems.

Control of cell proliferation is critical for the lymphocyte life cycle. However, little is known about how stage-specific alterations in cell cycle behavior drive proliferation dynamics during T cell development. Here, we employed in vivodual-nucleoside pulse labeling combined with the determination of DNA replication over time as well as fluorescent ubiquitination-based cell cycle indicator mice to establish a quantitative high-resolution map of cell cycle kinetics of thymocytes. We developed an agent-based mathematical model of T cell developmental dynamics. To generate the capacity for proliferative bursts, cell cycle acceleration followed a “stretch model” characterized by the simultaneous and proportional contraction of both G1 and S phases. Analysis of cell cycle phase dynamics during regeneration showed tailored adjustments of cell cycle phase dynamics. Taken together, our results highlight intrathymic cell cycle regulation as an adjustable system to maintain physiologic tissue homeostasis and foster our understanding of dysregulation of the T cell developmental program.

The charge pump phase-locked loops with a digital sequential phase frequency detector are analyzed using linear and nonlinear models. Nonlinear analytical maps are derived. The stability analysis results agree with linear analysis results, with higher order corrections. The effects of the ioop delay are also discussed. [ABSTRACT FROM AUTHOR]

Abstract: We present a class of one-dimensional systems of nonlinear parabolic equations for which the phase dynamics at large time can be described by an ODE with a Lipschitz vector field in \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathbb R^n$$\end{document}. In the considered case of the Dirichlet boundary value problem, the sufficient conditions for a finite-dimensional reduction turn out to be much wider than the known conditions of this kind for a periodic situation.

A relativistic magneto-isolated vircator on the underlimit electron beam is studied. It contained two serial magnetic mirrors and a coaxial output of microwave radiation. Its 2.5-D particle-in-cell (PIC)-simulation is carried out. Space and phase dynamics of electrons are calculated. The mode is found at which several virtual cathodes (VCs) exist simultaneously in an electron beam, i.e., the multivircator mode is realized in the device. Spectral and power characteristics of the multivircator generation with two magnetic mirrors are calculated. The dependence of the average output microwave radiation and wave resistance of the radiation coaxial output is also calculated. The spectrogram of microwave radiation is provided.

Exploring the electronic structure and dynamic behavior of Mn(II) complexes reveals fascinating magnetic properties and prospective biomedical applications. In this study, we investigate the solvent phase dynamics of heptacoordinated Mn(II) complexes through ab initio molecular dynamics simulations and density functional theory (DFT) calculations with effectively varying temperatures. We observed that the complex with high stability ([Mn(pmpa)(H2O)2]) remains relatively rigid as the temperature increases to 90 °C, with only a minor change in its radial distribution functions (RDFs), compared to the RDF peaks at 25 °C. To elucidate the impact of halogens on the magnetic anisotropy of seven-coordinated Mn(II) complexes, we performed both DFT and multireference calculations. This shows that the zero-field splitting (ZFS) parameter Dfollows the order D(I)> D(Br)> D(Cl). We observed a significant increase in the D-value following the substitution of soft Se-donors in the equatorial position and heavier halogens in the axial position. The D-value of halogen derivatives of Se-analogues varies in the order of D(Cl) < D(I) < D(Br), deviating from the regular spectrochemical series with the discrepancy between the covalency of the Mn(II)–Se bond and the ligand field strength. We anticipate that this study will enhance our understanding of the solvent phase dynamics and structural aspects of ZFS in various Mn(II) complexes with different electronic environments.

Pulp-phase dynamics strongly impact flotation performance, yet flotation control and monitoring are usually limited to surface level froth characteristics. An online pulp-phase sensor promises a better understanding of flotation process dynamics and performance. This utility needs to be demonstrated through field trials with structured experimental design and testing under representative conditions. A three-factor Box-Behnken design was implemented to test airflow, pulp level, and frother reagent addition on pulp-phase measurements. The correlation of online pulp-phase measurements to offline pulp sensor measurements is analysed and discussed.

We have investigated the theoretical constraints of the interactions between coupled cortical columns. Each cortical column consists of a set of neural populations where each population is modelled as a neural mass. The existence of semi-stable states within a cortical column is dependent on the type of interaction between the neuronal populations, i.e., the form of the synaptic kernels. Current-to-current coupling has been shown, in contrast to potential-to-current coupling, to create semi-stable states within a cortical column. The interaction between semi-stable states of the cortical columns is studied where we derive the dynamics for the collected activity. For small excitations the dynamics follow the Kuramoto model; however, in contrast to previous work we derive coupled equations between phase and amplitude dynamics with the possibility of defining connectivity as a stationary and dynamic variable. The turbulent flow of phase dynamics which occurs in networks of Kuramoto oscillators would indicate turbulent changes in dynamic connectivity for coupled cortical columns which is something that has been recorded in epileptic seizures. We used the results we derived to estimate a seizure propagationmodel which allowed for inversions using the Laplace assumption (Dynamic Causal Modelling). The seizure propagation model was trialed on simulated data, and future work will investigate the estimation of the connectivity matrix from empirical data. This model can be used to predict changes in seizure evolution after virtual changes in the connectivity network, something that could be of clinical use when applied to epilepsy surgical cases.

This technical note introduces an observer-based adaptive output feedback tracking control design for multi-input-multi-output dynamical systems with matched uncertainties. The reported methodology exploits asymptotic behavior of LQG/LTR regulators. Sufficient conditions for closed-loop stability and uniform ultimate boundedness of the corresponding tracking error dynamics are formulated. This method is valid for systems whose nominal linearized dynamics are controllable and observable. We assume that the number of the system measured outputs (sensors) is greater than the number of the control inputs (actuators) and that the system output-to-input matrix product has full column rank. In this case, the system can be “squared-up” (i.e., augmented) using pseudo-control signals to yield relative degree one minimum-phase dynamics. Since it is known that the “squaring-up” problem is solvable for any controllable observable triplet (A, B, C), the proposed design is applicable to systems whose regulated output dynamics may be non-minimum phase or have a high relative degree. A simulation example is presented to demonstrate key design features. [ABSTRACT FROM AUTHOR]

Nonlinear THz-THz-Raman (TTR) liquid spectroscopy offers new possibilities for studying and understanding condensed-phase chemical dynamics. Although TTR spectra carry rich information about the systems under study, the response is encoded in a three-point correlation function comprising of both dipole and polarizability elements. Theoretical methods are necessary for the interpretation of the experimental results. In this work, we study the liquid-phase dynamics of bromoform, a polarizable molecule with a strong TTR response. Previous work based on reduced density matrix (RDM) simulations suggests that unusually large multiquanta dipole matrix elements are needed to understand the measured spectrum of bromoform. Here, we demonstrate that a self-consistent definition of the time coordinates with respect to the reference pulse leads to a simplified experimental spectrum. Furthermore, we analytically derive a parametrization for the RDM model by integrating the dipole and polarizability elements to the 4th order in the normal modes, and we enforce inversion symmetry in the calculations by numerically canceling the components of the response that are even with respect to the field. The resulting analysis eliminates the need to invoke large multiquanta dipole matrix elements to fit the experimental spectrum; instead, the experimental spectrum is recovered using RDM simulations with dipole matrix parameters that are in agreement with independent ab initio calculations. The fundamental interpretation of the TTR signatures in terms of coupled intramolecular vibrational modes remains unchanged from the previous work.

• A high-order finite difference scheme for compressible multiphase flow is presented. • The scheme is based on weighted essentially non-oscillatory reconstruction. • The scheme applies the reconstruction on primitive field variables. • The scheme overcomes the difficulty of common schemes applied to multiphase flows. • The scheme is simple and more efficient than finite volume schemes. This paper presents a high-order weighted essentially non-oscillatory (WENO) finite difference scheme for compressible multi-fluid and multi-phase dynamics. The scheme overcomes the difficulty of applying the common flux-based WENO finite difference scheme to multi-fluid problems by applying the reconstruction on primitive variables and, thus avoiding the spurious oscillations inherent in the standard methods. Schemes of orders up to nine are introduced and analyzed. The proposed finite difference schemes are significantly more efficient than the available high-order finite volume schemes in both storage requirement, operation counts, and inter-processor message passing in parallel computations with efficiency gains being higher at higher orders and higher spatial dimensions. For the same level of accuracy, in three-dimensional calculations, a fourfold speedup or higher at fifth-order accuracy or higher over the finite volume scheme is expected. A comparison of the proposed scheme with the standard flux-based finite difference scheme in solving a single-fluid shock small entropy wave interaction is presented, demonstrating its excellent performance. In a challenging, two-fluid problem of a strong shock interacting with a helium-air interface, the accuracy, non-oscillatory, conservation, and convergence of the scheme are illustrated. Moreover, in a liquid water-air shock tube problem, the scheme effectively captures compression and expansion waves and contact discontinuity, and outperforms low-order schemes. In computations of a two-dimensional shock bubble interaction, good agreements with experimental data are obtained and competitive performance to the high-order finite volume scheme is shown. [ABSTRACT FROM AUTHOR]

In this paper, the output tracking problem for linear and nonlinear systems in normal form is revisited in the case of non-minimum phase dynamics and in the absence of any model for the exosystem generating the periodic reference signal. The asymptotic output tracking is obtained by replacing the classical stability condition for the zero dynamics driven by the reference signal with the existence of a solution to a two-point boundary value problem. The latter solution allows to generate the ideal steady-state evolution of the zero dynamics. This strategy allows to retain two interesting features of standard tracking and regulation approaches, namely, i) the use of a simple linear feedback structure and without the need of solving any partial differential equation (as in tracking) and ii) avoiding minimum phase requirements (as in output regulation). Since the same kind of two-point boundary value problem usually arises in the application of the Pontryagin Minimum Principle in optimal control, a natural question to ask is whether there is an underlying connection; hence, in the linear case, further insights are achieved by comparison with an alternative solution based on optimal control problem formulated for an auxiliary affine system.

Abstract: Natural disturbances have been traditionally defined in terms of major catastrophic events originating in the physical environment and, hence, have been regarded as exogenous agents of vegetation change. Problems with this view are: (1) there is a gradient from minor to major events rather than a uniquely definable set of major catastrophes for each kind of disturbance, and (2) some disturbances are initiated or promoted by the biotic component of the system. Floras are rich in disturbance-adapted species. Disturbances have probably exerted selective pressure in the evolution of species strategies. Heathland cyclic successions and gap-phase dynamics in forests have been viewed as endogenous patterns in vegetation. When death in older individividuals imposes a rhythm on community reproduction, dynamics may indeed be the result of endogenous factors. However, documented cases of senescence in perennial plants are few and many cyclic successions and cases of gap-phase dynamics are initiated by physical factors. Forest dynamics range from those that are the result of individual tree senescence and fall, through those that are the result of blowdown of small groups of healthy trees, to those that are the result of large windstorms which level hectares of forest. The effect of wind ranges from simple pruning of dead plant parts to widespread damage of living trees. Wind speed is probably inversely proportional to occurrence frequency. Disturbances vary continuously. There is a gradient from those community dynamics that are initiated by endogenous factors to those initiated by exogenous factors. Evolution has mediated between species and environment; disturbances are often caused by physical factors but the occurrence and outplay of disturbances may be a function of the state of the community as well. Natural disturbances in North American vegetation are: fire, windstorm, ice storm, ice push on shores, cryogenic soil movement, temperature fluctuation, precipitation variability, alluvial processes, coastal processes, dune movement, saltwater inundation, landslides, lava flows, karst processes, and biotic disturbances. Disturbances vary regionally and within one landscape as a function of topography and other site variables and are characterized by their frequency, predictability, and magnitude. The landscape level is important in assessing disturbance regime. Disturbances and cyclic successions belong to the same class of events—that of recurrent dynamics in vegetation structure—irrespective of cause. Dynamics may result from periodic, abrupt, and catastrophic environmental factors or they may result from an interaction of the changing susceptability of the community and some regular environmental factor. In any case, the dynamics result in heterogeneous landscapes; the species adapted to this heterogeneity are numerous, suggesting their long time importance. The importance of disturbance regime as part of the environmental context of vegetation means that allogenic and autogenic models of vegetation are difficult to apply. Species composition can be seen to be a function of disturbance regime, as well as other environmental variables. Competitive replacement in succession occurs, then, only as disturbances cease to operate and can be viewed as allogenic adjustment to a new disturbance-free environment. Competitive divergence, separation of role, and competition avoidance may, in fact, underlie successional patterns traditionally viewed as the competitive replacement of inferior species by superiorly adapted climax species. The importance of ongoing dynamics is also difficult to reconcile with the concept of climax, founded as it is on the idea of autogenesis within a stable physical environment. Climax composition is relative to disturbance regime. Climax is only arbitrarily distinguished from succession. Climax as an organizing paradigm in plant ecology has obscured the full temporal-spatial dimensions important in understanding the vegetated landscape and the evolution of species which contribute to the landscape patterns. Whittaker’s coenocline concept is accepted with modifications: (1) natural disturbance gradients and Whittaker’s complex gradient are intimately related, (2) temporal variation in the community should be viewed as an added axis of community pattern, and (3) ongoing dynamics have important effects on specificity of species to site relations and the predictability of vegetation patterns. Recent work has suggested an r-K continuum in species strategy. In general, colonizing ability is seen as a trade-off against specialization. Frequent disruption of the community and the creation of open sites seems to result in mixes of species that are fleeting in time and do not repeat in space. Species in such mixes are often tolerant of wide environmental extremes but are compressed into early successional time if disturbance ceases. The composition of such communities is not predictable from site characteristics. Even communities with low disturbance frequency lack complete environmental determinism, and historical events are important in understanding present composition. Communities vary in level of environmental determinism and species differ in niche breadth and degree of site specificity. Management implications of vegetation dynamics are discussed.

Recently, Hsieh and Otto (2014) suggested that transport of the closed magnetic flux to the dayside reconnection region may be a key process which controls the reconfiguration of magnetotail during the substorm growth phase. We investigate this problem using global self‐consistent MHD simulations and confirm that magnetotail reconfiguration is essentially a 3‐D process which cannot be fully described based on 2‐D‐like tail evolution powered by the magnetic flux loading into the lobes. We found that near‐Earth return convection strength on the nightside is directly related to the intensity of dayside reconnection, which causes the formation of antisunward azimuthal pressure gradients that force plasma to flow toward the dayside magnetopause. This near‐Earth part of global convection develops immediately after the onset of dayside reconnection and reaches a quasi‐steady level in 10–15 min. Its magnitude exceeds the total sunward flux transport in the midtail plasma sheet at X≈−20REby an order of magnitude, causing significant amount (0.1–0.2 GWb) of closed magnetic flux to be removed from the near‐Earth plasma sheet during moderate substorm. In that region the Bzdepletion and current sheet thinning are closely related to each other, and the local Jy(Bz) relationship in the simulations matches reasonably well the power law expression found in the plasma sheet. In summary, global simulations confirm quantitatively that near‐Earth return convection is primarily responsible for the severe depletion of the closed magnetic flux in the plasma sheet, major tail stretching, and current sheet thinning in the near magnetotail at r< 15RE. Global MHD (LFM) simulations of magnetotail growth phase dynamics following north‐south IMF turningsReturn convection at r< 10REon the nightside is proportional to EKLand by an order of magnitude higher than in the midtail at X=− 20RERemoval of closed magnetic flux by return convection controls the major reconfiguration of near magnetotail during substorm growth phase

Recent in vitro studies have identified small-molecule pharmaceuticals effecting dose-dependent changes in the mammalian circadian clock, providing a novel avenue for control. Most studies employ light for clock control, however, pharmaceuticals are advantageous for clock manipulation through reduced invasiveness. In this paper, we employ a mechanistic model to predict the phase dynamics of the mammalian circadian oscillator under the effect of the pharmaceutical under investigation. These predictions are used to inform a constrained model predictive controller (MPC) to compute appropriate dosing for clock re-entrainment. Constraints in the formulation of the MPC problem arise from variation in the phase response curves (PRCs) describing drug effects, and are in many cases non-intuitive owing to the nonlinearity of oscillator phase response effects. We demonstrate through in-silico experiments that it is imperative to tune the MPC parameters based on the drug-specific PRC for optimal phase manipulation.

Cohesion in networks during transitions from one consensus value to another, i.e., the ability of agents to respond in a similar manner during the transition, can be as important as achieving the new consensus value. Existing decentralized network control strategies mainly concern with the convergence speed to the final consensus value. However, even with increased convergence speed, the level of cohesion loss during transitions can be large. This loss of cohesion during transition (and tracking of varying consensus values) can be alleviated using a recently developed delayed self reinforcement (DSR) approach. However, the current DSR-based approach assumes ideal conditions with agents having instant access to neighbor information—without network delays arising during sensing or communication between neighbors, as well as computation of control actions of each agent, which can cause instability. The main contributions of this article are to use the Rouchè’s theorem to 1) prove the stability of the DSR approach if the network delay is not too large; and 2) compute an estimate of the acceptable network delay margin (DM) for stability. Additionally, a simulation example is used to illustrate the estimation approach for network DMs with DSR, and show that cohesion is maintained with DSR even with network delays when compared to the case without DSR. [ABSTRACT FROM AUTHOR]

This article develops a distributed solution to the fully heterogeneous containment control problem (CCP), for which not only the followers’ dynamics but also the leaders’ dynamics are nonidentical. A novel formulation of the fully heterogeneous CCP is first presented in which each follower constructs its virtual exosystem. To build these virtual exosystems by followers, a novel distributed algorithm is developed to calculate the so-called normalized level of influences (NLIs) of all leaders on each follower, and a novel adaptive distributed observer is designed to estimate the dynamics and states of all leaders that have an influence on each follower. Then, a distributed control protocol is proposed based on the cooperative output regulation framework, utilizing this virtual exosystem. Based on the estimations of leaders’ dynamics and states and NLIs of leaders on each follower, the solutions of the so-called linear regulator equations are calculated in a distributed manner, and consequently, a distributed control protocol is designed for solving the output containment problem. Finally, theoretical results are verified by performing numerical simulations. [ABSTRACT FROM AUTHOR]

In multi-modular process architectures with independent but interacting subsystems, identification may not be the first choice at hand for closed loop control. A robust relay-based PID autotuning strategy is presented and validated on a quadruple tank system with non-minimum phase dynamics. The controller ensures a specified closed loop robustness, which is of great benefit to the overall performance. The experimental results suggest that the proposed method fulfils the robustness requirement and performs well in various operating conditions of the testbench.

Cyclin dependent kinase 5 (Cdk5) is a determinant of PARP inhibitor and ionizing radiation (IR) sensitivity. Here we show that Cdk5-depleted (Cdk5-shRNA) HeLa cells show higher sensitivity to S-phase irradiation, chronic hydroxyurea exposure, and 5-fluorouracil and 6-thioguanine treatment, with hydroxyurea and IR sensitivity also seen in Cdk5-depleted U2OS cells. As Cdk5 is not directly implicated in DNA strand break repair we investigated in detail its proposed role in the intra-S checkpoint activation. While Cdk5-shRNA HeLa cells showed altered basal S-phase dynamics with slower replication velocity and fewer active origins per DNA megabase, checkpoint activation was impaired after a hydroxyurea block. Cdk5 depletion was associated with reduced priming phosphorylations of RPA32 serines 29 and 33 and SMC1-Serine 966 phosphorylation, lower levels of RPA serine 4 and 8 phosphorylation and DNA damage measured using the alkaline Comet assay, gamma-H2AX signal intensity, RPA and Rad51 foci, and sister chromatid exchanges resulting in impaired intra-S checkpoint activation and subsequently higher numbers of chromatin bridges. In vitrokinase assays coupled with mass spectrometry demonstrated that Cdk5 can carry out the RPA32 priming phosphorylations on serines 23, 29, and 33 necessary for this checkpoint activation. In addition we found an association between lower Cdk5 levels and longer metastasis free survival in breast cancer patients and survival in Cdk5-depleted breast tumor cells after treatment with IR and a PARP inhibitor. Taken together, these results show that Cdk5 is necessary for basal replication and replication stress checkpoint activation and highlight clinical opportunities to enhance tumor cell killing.