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The phase dynamics of bulk (SOA) examined with regard with all-optical switching applications.

The Southern African Customs Union is the oldest customs union in the world and the member states form a currency union with the South African Rand being the regional currency anchor. Therefore, currency movements amongst SACU member are dependent on the developments on the Rand which, in turn, can affect stock market development in the region. We examine the time-frequency relationship between exchange rates and stock market returns in SACU countries using continuous wavelet transforms. Our empirical analysis is two-staged. Firstly, we employ wavelet power spectrum to examine the time-frequency properties of the individual series. Secondly, we use wavelet coherence analysis and phase dynamics to examine the synchronization between the variables in a time-frequency space. Our findings show stronger (weaker) exchange rate-stock returns relations are found during periods of higher (lower) inflation whereas we observe a stronger (weaker) relationship during periods of lower interest rate environment. Moreover, we find more significant long-run relationships for countries with more independent monetary policy (South Africa and Botswana) whereas these relations are more prominent over the short-run for countries with pegged exchange rates (Eswatini and Namibia). We also observe that periods of oil and currency shocks impact the exchange rate-stock returns relationship in SACU countries with pegged exchange rates (Eswatini and Namibia). Our findings bear important implications for different stakeholders. For instance, this study has implications for exchange rate policy as it addresses the issue of whether the exchange rate can be used to improve market performance or exchange rate developments spillover into the stock market. Furthermore, corporate managers and stock market participants would be interested in our findings as it identifies periods of market inefficiency when exchange rates can be used to beat the stock market. JEL Classifications: C1, C2, C5 and G1 Keywords: Continuous wavelet transforms, Wavelet coherence, exchange rates, stock market, SACU, INTRODUCTION Following widespread changes in the international exchange rate system and the increased globalization of capital markets experienced over the last quarter of the century, equity and currency markets have [...]

Communication over the noncoherent additive white Gaussian noise (AWGN) channel is considered, where the transmitted signal undergoes a phase rotation, unknown to the transmitter and the receiver. The effects of phase dynamics are explicitly taken into account by considering a block-independent model for the phase process: the unknown phase is constant for a block of N complex symbols and independent from block to block. In the first part of the paper, the capacity-achieving input distribution is characterized. In particular, it is shown that the maximizing density has circular symmetry, is discrete in amplitude with infinite number of mass points, and always has a mass point at zero. Furthermore, asymptotic expressions and bounds for the capacity are derived. Based on these results, the capacity is evaluated through numerical optimizations for unconstrained and modulation-constrained input distributions. In the second part of this paper, inspired by the capacity results, two classes of coding and modulation schemes are proposed for fast and moderate phase dynamics. In the case of fast phase dynamics (i.e., small N), optimized modulation alphabets are designed having exponential complexity with N at the demodulator. In the case of moderate phase dynamics (i.e., moderate values of N), specially designed modulation alphabets are utilized that have linear complexity with N. These alphabets are used together with optimized irregular low-density parity-check (LDPC) codes. Simulation results show that these codes can achieve close-to-capacity performance with moderate complexity, and outperform the best known codes so far. Index Terms--Block-independent noncoherent channel, channel capacity, coding for noncoherent channel, noncoherent channel.

Phase dynamics and phase noise of N coupled phase-locked loops (PLLs) with N independent oscillators are analyzed. The phase noise of coupled PLLs with independent oscillators is analyzed by using the signal flow graph and Mason's gain rules. The near-carrier phase noise of PLL elements in the array can be reduced to 1/N that of a single independent (without coupling) VCO oF the PLL element, and return to its free-running phase noise far from the carrier frequency, provided the coupling network is reciprocal, the feedback loop gain of the PLL elements is large, and the Phase detector and amplifier noise are neglected. The phase dynamics and noise improvement of coupled PLL arrays are verified by using two coupled PLLs with independent GaAs MESFET x oscillators operating at X-band. Index Terms--Active antenna array, AM noise, beam control, coupled oscillators, coupled phase-locked loops (PLLs), feedback loop, injection locked, locking range, Mason's gain rule, oscillator, phase locked, phase noise (PM noise), PLL, signal flow graph (SFG).

Amorphous phase dynamics in Poly(lactic acid) (PLA) with different crystallinity degrees have been investigated from the vitreous state to the glass transition by means of two calorimetric methods. Temperature Modulated Differential Scanning Calorimetry was used to characterize the heat capacity signals and the average cooperativity length at the glass transition in non-aged materials. Standard DSC was used to study the physical aging. It is shown that amorphous and fully crystallized PLA exhibit different relaxation parameters. For semicrystalline PLA with an intermediate degree of crystallinity, the peaks of the enthalpy of recovery and the out-of-phase heat capacity component are bimodal. The bimodality of the peaks is attributed to the relaxations of the inter-spherulitic and intraspherulitic amorphous phases, respectively. Thus, in partially crystallized PLA, the non-crystalline fraction of the material could be divided in three fractions, namely the Rigid Amorphous Fraction, the interspherulitic Mobile Amorphous Phase (MAP), and the intra-spherulitic MAP. Each of them exhibits a distinct molecular mobility. POLYM. ENG. SCI., 54:1144-1150, 2014., INTRODUCTION In recent years, environmental concerns have increased the interest in biodegradable and/or biosourced packaging materials to replace commonly used plastics issued from petrochemistry [1]. Nevertheless, using these kinds of [...]

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.apergo.2008.12.005 Byline: Leslie Decker (a), Jeremy J. Houser (c), John M. Noble (a), Gregory M. Karst (d), Nicholas Stergiou (a)(b) Abstract: This study aims to investigate the effects of shoe traction and obstacle height on lower extremity relative phase dynamics (analysis of intralimb coordination) during walking to better understand the mechanisms employed to avoid slippage following obstacle clearance. Ten participants walked at a self-selected pace during eight conditions: four obstacle heights (0%, 10%, 20%, and 40% of limb length) while wearing two pairs of shoes (low and high traction). A coordination analysis was used and phasing relationships between lower extremity segments were examined. The results demonstrated that significant behavioral changes were elicited under varied obstacle heights and frictional conditions. Both decreasing shoe traction and increasing obstacle height resulted in a more in-phase relationship between the interacting lower limb segments. The higher the obstacle and the lower the shoe traction, the more unstable the system became. These changes in phasing relationship and variability are indicators of alterations in coordinative behavior, which if pushed further may have lead to falling. Author Affiliation: (a) Nebraska Biomechanics Core Facility, University of Nebraska at Omaha, 6001 Dodge Street, Omaha, NE 68182-0216, USA (b) Environmental, Agricultural and Occupational Health, College of Public Health, University of Nebraska Medical Center, 987850 Nebraska Medical Center, Omaha, NE 68198-7850, USA (c) Department of Health and Exercise Sciences, School of Health Sciences and Education, Truman State University, 212 Pershing Building, 100 E. Normal St., Kirksville, MO 63501, USA (d) Division of Physical Therapy Education, University of Nebraska Medical Center, 984420 Nebraska Medical Center, Omaha, NE 68198-4420, USA Article History: Received 5 October 2007; Accepted 29 December 2008

The analysis and experimental results of an antenna array using injection locked coupled oscillators with self-tuning of oscillator free-running frequencies are presented. With the use of coupled type-II phase locked loops for tuning oscillator free-running frequencies and an external injection signal for stabilizing the array operating frequency, this antenna array can steer its beam through a single control voltage and hold its output frequency at the injection signal frequency in operation. In addition, its beam-pointing error arising from phase errors in coupled oscillators can be reduced and the array works well over a certain frequency band. Phase dynamics and stability are studied and experimentally verified. Experimental results of a three-element injection locked coupled oscillator array show that its uniform phase progression ranges between -16[degrees] and 52[degrees], and the phase errors are less than 5[degrees] at 2.7 GHz. The operation bandwidth is shown from 2.68-2.72 GHz. By loading the injection locked coupled oscillator array with rectangular patch antennas, the beam-steering radiation characteristics are measured at various control voltages. Index Terms--Coupled oscillators, injection locked oscillators, phase locked loops, stability.

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 loop delay are also discussed. Index Terms--Charge-pump phase-locked loop (PLL), phase dynamics, stability.

The paper addresses the problem of output power regulation of fixed-pitch variable-speed wind energy conversion systems. Operation is constrained by practical reasons to the low-speed side of the turbine power--speed curve. Unfortunately, this region is characterized by a nonminimum phase dynamics which is an obstacle to perform the regulation task. A dynamical variable structure controller is developed that accomplishes the control objective despite this limitation. The proposed control strategy presents attractive features such as robustness to parametric uncertainties of the turbine and generator as well as to electric grid disturbances. Index Terms--Power generation control, variable structure systems, wind energy.

In this paper, we consider iterative detection over bandpass channels that introduce an unknown phase rotation in the transmitted signal. This work focuses on the comparison between two adaptive detection strategies for trellis-based coded modulation: limited-tree-search (LTS) detection, obtained by reducing a tree search to a limited trellis search, and truncated-memory (TM) detection, based on channel-memory truncation, which automatically leads to a trellis search. Both strategies are used to derive trellis-based forward-backward (FB) algorithms. A quantitative analysis based on simulations, with various coding and modulation schemes, is carried out to evaluate and compare the two approaches. The results show that the channel-phase dynamics should significantly influence the choice of the detection strategy: For low-phase variations, LTS algorithms are a simple and reasonable choice, while for moderate to fast phase variations, TM algorithms show a considerable robustness. Index Terms--Adaptive iterative detection, noncoherent detection, truncated-memory detection.

The phase dynamics of double-barrier Josephson junction that is implemented in the rapid-single-flux-quantum (RSFQ) circuits and their current use in voltage standards is discussed. Decreasing the switching time of Josephson elements and reducing the excess wiring are the ways by which microscopic analyses allows optimization of the performance of the double-barrier Josephson junction-based RSFQ

In this paper, design and robustness of rotationally invariant (RI) codes is investigated. In the first part of this paper, RI codes are extended to the case of serially concatenated (SC) trellis-coded modulation (TCM) and several high-rate powerful RI-SCTCM codes are designed over 8-phase-shift keying and 16-quadrature amplitude modulation alphabets. The investigation continues by considering more realistic channels that introduce cycle slips during phase estimation, and thus rotate only part of the transmitted codeword. It is proven that RI codes with small state space are robust in these channels, even when traditional coherent decoders are utilized. Furthermore, it is demonstrated through simulations that the addition of a simple stopping criterion to the coherent iterative decoding algorithm is sufficient for robustness of the more powerful RI-SCTCM codes when partial codeword rotations are considered. Finally, the issue of whether RI codes are useful for transmission in the noncoherent channel is investigated. It is proven that RI codes are as good as any other good codes for this channel when the phase dynamics are low, and optimal decoding is performed. However, it is shown that for a certain class of receivers, RI codes are also robust to partial phase rotations in this channel. Index Terms--Noncoherent channels, rotationally invariant codes, trellis codes, turbo codes.

We describe the effect of phase synchronization of chaotic oscillators. It is shown that phase can be defined for continuous time dynamical oscillators with chaotic dynamics, and effects of phase and frequency locking can be observed. We introduce several tools which characterize this weak synchronization and demonstrate phase and frequency locking by external periodic force, as well as due to weak interaction of nonidentical chaotic oscillators. In the synchronous state the phases of two systems are locked, while the amplitudes remain chaotic and noncorrelated. The intermittency phenomenon at the synchronization transition is considered. The application to the analysis of bivariate experimental data is discussed. Index Terms - Chaotic oscillators, frequency locking, phase dynamics, weak interaction.

Forest models based on the gap dynamics hypothesis ('gap models') have gained an important role in forest ecology and have grown rather complex in the last 20 yr. They have been applied extensively to study the impacts of climatic change on ecosystems although they originally were not built for this purpose. The objectives of this study were (1) to develop a new forest gap model, FORCLIM, that includes only a minimum number of ecological assumptions but robust parameterizations of the effects of climate on plant population dynamics; (2) to test the realism of FORCLIM as compared to its predecessor model, FORECE; and (3) to examine the behavior of FORECE and FORCLIM systematically along climate gradients in Europe. FORCLIM is composed of three modular submodels: FORCLIM-P for plant population dynamics, FORCLIM-S for soil carbon/nitrogen turnover, and FORCLIM-E for providing reliable parameterizations of the abiotic environment. For the core model, FORCLIM-P, it was found that only four factors are sufficient to model tree growth, another four factors are required to model tree establishment, and only two factors are required to model tree mortality. The behavior of FORCLIM was tested at a large number of sites in the European Alps. The model yields tree species compositions that conform to field data and are very similar to those of the predecessor model. Based on this evaluation alone, it would not be possible to favor one of the models over the other. The behavior of both models then was examined systematically in a parameter space spanned by the annual mean temperature and the annual precipitation sum. From this exercise it became evident that both the pattern of aboveground biomass and the realized niches of the dominating tree species are simulated realistically by FORCLIM. Extremely steep gradients are characteristic of FORECE, and many ecotones are simulated to occur in the wrong places in FORECE. Thus, some of the current forest gap models can be simplified without reducing the realism of their behavior, and models other than FORECE should be scrutinized in this respect as well. The present study also suggests that the evaluation of model behavior at scattered sites is insufficient to show their validity for simulating forest dynamics along climate gradients. Further rigorous model comparisons and validation studies are required to increase the reliability of this promising class of models. Key words: climatic change; Europe; FORCLIM; forest ecology; forest gap models; model comparisons; model simplification; modular modeling; niche theory; validation., INTRODUCTION During the past 25 yr, quantitative models of tree population dynamics based on the gap-phase dynamics hypothesis (Watt 1947) have attracted increasing scientific attention and have produced a rich [...]

This paper presents a simple method for the calculation of the frequency and power variation of an active antenna operated in the presence of a reflecting surface. The situation modeled accounts for interdependent amplitude and phase dynamics and also allows for the extraction of active antenna array coupling coefficients. Analytical and experimental results are presented for both frequency and power variations of an individual element when operated in a strongly coupled imaged array environment. Here the nearest neighbor coupling is shown to be the dominant coupling mechanism.

This paper considers the analysis of an oscillator array with an arbitrary coupling network, described in terms of N-port circuit parameters. A Kurokawa analysis is used to transform the frequency domain network description into a set of equations for the oscillator amplitude and phase dynamics. The results reduce to previous work with 'loosely' coupled Van der Pol oscillators, provided that the coupling network satisfies a broadband condition: the Q-factor of the coupling network must be much smaller than that of the oscillator. The theory is verified using a new coupling structure and a six-element patch oscillator array operating at 4 GHz, which produced a 70 [degrees] scanning range using a phase-shifterless technique.

Theoretical studies involving cross- and time-covariance functions of the variables controlling Langevin noise sources help examine the noise in semiconductor lasers. Analytical expressions represent frequency noise, carrier noise spectrum, the AM and FM noise and the phase change modification. Approximations of the phase dynamics require the inclusion of the shot noise factor in addition to carrier contributions.

Arrays of coupled oscillators can be used for power-combining at microwave and millimeter-wave frequencies, and have been successfully demonstrated with a variety of devices. Such arrays have also recently been mode-locked for pulse generation, and can be configured for phase-shifterless beam-scanning. The nonlinear theory of coupled-oscillator phase dynamics depends crucially on the parameters describing the coupling between oscillators. Methods for experimental characterization of these parameters are described here, and simple models are developed which reproduce the measurements quite well. The models apply to radiative coupling and the effects of external reflectors which are sometimes used for stabilization. The theory is verified with a two-oscillator system.

SUMMARY (1) A computer model was developed to simulate natural forest dynamics. Relationships of leaf area to sapwood area, stem respiration to sapwood volume and vigour to growth efficiency provide equations for tree growth, leaf-area dynamics and canopy structure. The model simulates mixed-age, mixed-species populations of trees on a [1000-m.sup.2] patch. (2) The test site, Fiby urskog (central Sweden), has been unmanaged since a catastrophic storm in 1795. Pinas sylvestris (light-demanding) and Picea abies (shade-bearing) are dominant today. The Pinus trees are > 70 years old with high crowns, the Picea trees are all-aged; single-tree gaps are filled by saplings or small trees of Picea. The model was run for 190 years to simulate the natural succession. Present height and diameter distributions of Pinus and Picea, measured on a 0-5-ha stand, fell mostly within 95% limits from replicate model runs. (3) Simulated basal areas of Pinus and Picea were plotted as a function of variations in the species' potential growth rates. Picea abundance increased sigmoidally as its growth conditions improved, but Pinas was abundant only under conditions unfavourable to Picea. (4) A wide range of patch sizes produced accurate simulations, but if the patch size was toosmall (< 50 [m.sup.2]) the model allowed gap-phase replacement of Picea by Pinus. Such replacement was not observed. (5) A simulation with Betula pubescens and Populus tremula included reproduced the approximate composition of the stand. Pinus, Betula and Populus (all light-demanders) were important early in the simulated succession but were eventually replaced by Picea. This result also applied to patch sizes down to c. 50 [m.sup.2]; smaller patch sizes produced cyclical regeneration. (6) Even-aged stands of Pinus were simulated. After an initial phase with low mortality, the stands followed a self-thinning line until they reached a maximum biomas. (7) Some forests show gap-phase dynamics as described by Watt; others require disturbances producing multiple-tree gaps to complete the regeneration cycle. Boreal forests are of the latter type. The distinction is an emergent property of vegetation, determined by the ratio of maximum plant size to the natural scale of interactions between plants.

A new technique to analyze the energy flow in liquid-phase dynamics is described. Some of the energy in the transition is transferred from the reaction coordinate to other internal degrees of the solute. The rate at which the remaining energy is transferred to the solvent is a function of the reaction of coordinate phase space point and its time derivative as well as other velocities characterizing a trajectory of the system.

The heating rate effect on the phase transitions of a pure liquid crystal octylcyanobiphenyl (8CB) is examined with the use of Differential Scanning Calorimetry (DSC) and Modulation Calorimetry (MC) techniques. The comparison of these two techniques has revealed that the MC is a practicable tool for observing the phase dynamics, whereas DSC is a good tool for studying the rate kinematics of the transitions.

1 Data from elevations ranging from mixed hardwood-conifer forest at 600 m to subalpine Abies balsamea forest at 1120 m indicate that canopy gaps are not static but expand over time due to mortality of trees at the gap margin and coalescence of gaps. Gap expansion is more frequent than gap initiation. Ultimately such disturbance patches may become more extensive than is normally considered as typical of gap-phase disturbance, but the processes of development are the same. 2 Disturbance agents involved in gap initiation tend to differ from those involved in gap expansion. Spruce beetle, dwarf mistletoe and most root diseases predominate as agents of gap initiation, while windthrow/windsnap, chronic wind stress and Armillaria root disease are important agents of gap expansion. 3 Concepts of equilibrium gap-phase dynamics and a shifting-mosaic steady state do not fully account for the dynamics of these spruce-fir forests. A spruce beetle outbreak in the late 1970s/early 1980s killed most of a cohort of dominant, emergent Picea rubens. This epidemic initiated a long-term cycle of disturbance and release that is likely to be repeated in many years when a new cohort of P. rubens becomes sufficiently large to sustain another major bark beetle outbreak. 4 Episodic disturbance agents affect long-lived, dominant species at infrequent but regular intervals (up to hundreds of years) and operate at the landscape level. Gap-phase cycles appear to be nested within the long-term cycle. Over the long term, episodic disturbance drives such 'nested bicycle' dynamics. 5 Spatial and temporal distribution of disturbance results not only from stochastic events such as storms, but also from host specificity of agents of disturbance, their tendency to attack certain age classes of trees, local and regional contagion, and susceptibility of trees at the edge of disturbance patches.

1 Few studies have addressed the mechanisms of coexistence of shade-tolerant and intolerant tree species in the canopy of old-growth, lowland rain forests of southern South America. We explored the hypothesis that their forest dynamics result from frequent, single tree-fall gap episodes. 2 We analysed the disturbance regime and assessed the regeneration modes of shade-tolerant and intolerant canopy trees in a lowland, old growth North Patagonian rain forest in Chiloe Island (42[degrees] S) using dendroecological methods. 3 Dominant canopy trees were the shade-intolerant Nothofagus nitida (Fagaceae), Drimys winteri (Winteraceae) and the tolerant Podocarpus nubigena (Podocarpaceae). The oldest individuals, however, were represented by Saxegothaea conspicua, Podocarpaceae (shade tolerant > 498 years) and Weinmannia trichosperma, Cunoniaceae (intolerant > 382 years). Shade-tolerant species have regenerated continuously for the past 400 years, but recruitment of shade-intolerant species has increased only in the past 50 years. These regeneration patterns suggest a lack of catastrophic disturbance, at least since 1650. 4 Analysis of tree radial growth patterns revealed frequent moderate releases of both shade-tolerant and intolerant tree species, consistent with frequent small-scale disturbances, such as individual tree-fall gaps. Increased releases, peaking in 1940 and followed by enhanced recruitment, may be a consequence of individual tree-falls induced by low-intensity windstorms or limited selective logging. Such disturbances have occurred for at least 250 years, but have had little overall effect on stand structure and canopy composition. 5 The replacement and coexistence of shade-tolerant and intolerant tree species in the canopy of this North Patagonian forest can be explained by frequent small-scale disturbances (i.e. gap-phase dynamics) and by the absence of large-scale natural or anthropogenic disturbances over the past four centuries.

The ability of two coupled oscillators to synchronize depends critically on the coupling network. Previous analyses have accurately predicted the performance of quasi-optical microwave oscillator arrays for both weak and strong coupling, but have been limited to coupling networks with bandwidths considerably larger than the locking bandwidths of the oscillators. In this paper, the authors develop a method for deriving a suitable system of nonlinear differential equations describing the oscillator amplitude and phase dynamics using a generalization of Kurokawa's method. The method is applied to the case of two Van der Pol oscillators coupled through a resonant network for a wide range of coupling strengths and bandwidths. Simple approximate formulas are developed for the size of the frequency locking region as functions of the basic circuit parameters. Index Terms--Injection locking, oscillators.

Biomarkers play a crucial role in clinical diagnosis and therapy. There are various types of biomarkers concerning diagnosis, monitoring, treatment response, outcome prediction, prognosis, safety, and susceptibility/risk. (1) In fields [...]

Research was conducted to examine the dynamical behavior of initially one-mode amplitude- and phase-squeezed photon fields interacting with a two-state molecular system. it was found that the splitting into two peaks and their colliding processes in the Pegg-Barnett phase and the Q function distributions correspond to the collapse and revival behavior of the molecular population. Results also showed significant differences among the features of phase dynamics for the squeezed fields and those for the coherent field.

A study was conducted to analyze the lyotropic and thermotropic phase dynamics of hydrated monoacylglycerols and characterize monovaccenin. Dry solid monovaccenin was mixed with specific amounts of water in a syringe-based mixing system. Copper K-alpha x-rays in the line and point focus modes were utilized to determine the diffraction data. Experimental results indicated that monovaccenin can support a role as controlled-release drug carries and in crystallization media.

Water is one of the most important, yet least understood, liquids in nature. Many anomalous properties of liquid water originate from its well-connected hydrogen bond network.sup.1, including unusually efficient vibrational energy redistribution and relaxation.sup.2. An accurate description of the ultrafast vibrational motion of water molecules is essential for understanding the nature of hydrogen bonds and many solution-phase chemical reactions. Most existing knowledge of vibrational relaxation in water is built upon ultrafast spectroscopy experiments.sup.2-7. However, these experiments cannot directly resolve the motion of the atomic positions and require difficult translation of spectral dynamics into hydrogen bond dynamics. Here, we measure the ultrafast structural response to the excitation of the OH stretching vibration in liquid water with femtosecond temporal and atomic spatial resolution using liquid ultrafast electron scattering. We observed a transient hydrogen bond contraction of roughly 0.04 Å on a timescale of 80 femtoseconds, followed by a thermalization on a timescale of approximately 1 picosecond. Molecular dynamics simulations reveal the need to treat the distribution of the shared proton in the hydrogen bond quantum mechanically to capture the structural dynamics on femtosecond timescales. Our experiment and simulations unveil the intermolecular character of the water vibration preceding the relaxation of the OH stretch. Liquid ultrafast electron scattering measures structural responses in liquid water with femtosecond temporal and atomic spatial resolution to reveal a transient hydrogen bond contraction then thermalization preceding relaxation of the OH stretch., Author(s): Jie Yang [sup.1] [sup.2] [sup.11] , Riccardo Dettori [sup.3] , J. Pedro F. Nunes [sup.4] , Nanna H. List [sup.1] [sup.2] [sup.5] , Elisa Biasin [sup.1] [sup.2] , Martin [...]

Chemical vapour deposition of carbon-containing precursors on metal substrates is currently the most promising route for the scalable synthesis of large-area, high-quality graphene films.sup.1. However, there are usually some imperfections present in the resulting films: grain boundaries, regions with additional layers (adlayers), and wrinkles or folds, all of which can degrade the performance of graphene in various applications.sup.2-7. There have been numerous studies on ways to eliminate grain boundaries.sup.8,9 and adlayers.sup.10-12, but graphene folds have been less investigated. Here we explore the wrinkling/folding process for graphene films grown from an ethylene precursor on single-crystal Cu-Ni(111) foils. We identify a critical growth temperature (1,030 kelvin) above which folds will naturally form during the subsequent cooling process. Specifically, the compressive stress that builds up owing to thermal contraction during cooling is released by the abrupt onset of step bunching in the foil at about 1,030 kelvin, triggering the formation of graphene folds perpendicular to the step edge direction. By restricting the initial growth temperature to between 1,000 kelvin and 1,030 kelvin, we can produce large areas of single-crystal monolayer graphene films that are high-quality and fold-free. The resulting films show highly uniform transport properties: field-effect transistors prepared from these films exhibit average room-temperature carrier mobilities of around (7.0 [plus or minus] 1.0) × 10.sup.3 centimetres squared per volt per second for both holes and electrons. The process is also scalable, permitting simultaneous growth of graphene of the same quality on multiple foils stacked in parallel. After electrochemical transfer of the graphene films from the foils, the foils themselves can be reused essentially indefinitely for further graphene growth. Restricting the initial growth temperatures used for chemical vapour deposition of graphene on metal foils produces optimum conditions for growing large areas of fold-free, single-crystal graphene., Author(s): Meihui Wang [sup.1] [sup.2] , Ming Huang [sup.1] [sup.5] , Da Luo [sup.1] , Yunqing Li [sup.1] [sup.3] , Myeonggi Choe [sup.1] [sup.3] , Won Kyung Seong [sup.1] , [...]

Hibiscus exhibits high variation in chromosome number both within and among species. The Hibiscus mutabilis L. karyotype was analyzed in detail using fluorescence in situ hybridization (FISH) with oligonucleotide probes for [(A[G.sub.3][T.sub.3]).sub.3] and 5S rDNA, which were tested here for the first time. In total, 90 chromosomes were counted in prometaphase and metaphase, and all exhibited similarly intense [(A[G.sub.3][T.sub.3]).sub.3] signals at both ends. [(A[G.sub.3][T.sub.3]).sub.3] showed little variation and thus did not allow discrimination among H. mutabilis chromosomes, but its location at both ends confirmed the integrity of each chromosome, thus contributing to accurate counting of the numerous, small chromosomes. Oligo-5S rDNA marked the proximal/distal regions of six chromosomes: weak signals on chromosomes 7 and 8, slightly stronger signals on chromosomes 15 and 16, and very strong signals on chromosomes 17 and 18. Therefore, 5S rDNA could assist in chromosome identification in H. mutabilis. Metaphase chromosome lengths ranged from 3.00 to 1.18 [mu]m, indicating small chromosomes. The ratios of longest to shortest chromosome length in prometaphase and metaphase were 2.58 and 2.54, respectively, indicating karyotype asymmetry in H. mutabilis. These results provide an exact chromosome number and a physical map, which will be useful for genome assembly and contribute to molecular cytogenetics in the genus Hibiscus. Key words: Malvaceae, ribosomal RNA, chromosome ends, oligonucleotides. Le genre Hibiscus presente une grande variation quant au nombre de chromosomes tant au sein des especes qu'entre elles. Le caryotype de l'Hibiscus mutabilis L. a ete analyse en detail au moyen de l'hybridation in situ en fluorescence (FISH) a l'aide de sondes oligonucleotidiques pour le motif [(A[G.sub.3][T.sub.3]).sub.3] et l'ADNr 5S, toutes deux employees pour la premiere fois. Au total, 90 chromosomes ont ete comptes en prometaphase et en metaphase et ils pre-sentaient tous un signal [(A[G.sub.3][T.sub.3]).sub.3] d'intensite semblable aux deux extremites. Les signaux [(A[G.sub.3][T.sub.3]).sub.3] variaient peu et ne permettaient donc pas de distinguer les chromosomes du H. mutabilis, mais leur localisation aux deux extremites des chromosomes a permis de confirmer l'integrite de chaque chromosome et d'assurer un decompte juste du grand nombre de petits chromosomes. L'oligo d'ADNr 5S a marque les regions proximales/distales chez six chromosomes : des signaux faibles ont ete observes sur les chromosomes 7 et 8, des signaux legerement plus eleves ont ete vus sur les chromosomes 15 et 16, et de tres forts signaux ont ete observes sur les chromosomes 17 et 18. Ainsi, l'ADNr 5S pourrait aider dans l'identification de chromosomes chez le H. mutabilis. La longueur des chromosomes en metaphase variait entre 3,00 et 1,18 [mu]m, ce qui en faisait de petits chromosomes. Les ratios entre le chromosome le plus long et le plus court en prometaphas et et en metaphase etaient respectivement de 2,58 et 2,54, ce qui indique une asymetrie caryotypique chez le H. mutabilis. Ces resultats apportent un decompte exact des chromosomes et une carte physique, lesquels seront utiles pour l'assemblage d'un genome et contribueront a la cytogenetique moleculaire chez le genre Hibiscus. [Traduit par la Redaction] Mots-cles : Malvacees, ARN ribosomique, extremites des chromosomes, oligonucleotides., Introduction The genus Hibiscus comprises approximately 470 accepted species, and its native range is from the tropics and sub-tropics to North America (Christenhusz et al. 2017). To date, ~25 species [...]

Out of equilibrium, a lack of reciprocity is the rule rather than the exception. Non-reciprocity occurs, for instance, in active matter.sup.1-6, non-equilibrium systems.sup.7-9, networks of neurons.sup.10,11, social groups with conformist and contrarian members.sup.12, directional interface growth phenomena.sup.13-15 and metamaterials.sup.16-20. Although wave propagation in non-reciprocal media has recently been closely studied.sup.1,16-20, less is known about the consequences of non-reciprocity on the collective behaviour of many-body systems. Here we show that non-reciprocity leads to time-dependent phases in which spontaneously broken continuous symmetries are dynamically restored. We illustrate this mechanism with simple robotic demonstrations. The resulting phase transitions are controlled by spectral singularities called exceptional points.sup.21. We describe the emergence of these phases using insights from bifurcation theory.sup.22,23 and non-Hermitian quantum mechanics.sup.24,25. Our approach captures non-reciprocal generalizations of three archetypal classes of self-organization out of equilibrium: synchronization, flocking and pattern formation. Collective phenomena in these systems range from active time-(quasi)crystals to exceptional-point-enforced pattern formation and hysteresis. Our work lays the foundation for a general theory of critical phenomena in systems whose dynamics is not governed by an optimization principle. A theoretical study of non-reciprocity in collective phenomena reveals the emergence of time-dependent phases heralded by exceptional points in contexts ranging from synchronization and flocking to pattern formation., Author(s): Michel Fruchart [sup.1] , Ryo Hanai [sup.1] [sup.2] [sup.3] , Peter B. Littlewood [sup.1] , Vincenzo Vitelli [sup.1] [sup.4] Author Affiliations: (1) James Franck Institute and Department of Physics, [...]

Coherent control of quantum dynamics is key to a multitude of fundamental studies and applications.sup.1. In the visible or longer-wavelength domains, near-resonant light fields have become the primary tool with which to control electron dynamics.sup.2. Recently, coherent control in the extreme-ultraviolet range was demonstrated.sup.3, with a few-attosecond temporal resolution of the phase control. At hard-X-ray energies (above 5-10 kiloelectronvolts), Mössbauer nuclei feature narrow nuclear resonances due to their recoilless absorption and emission of light, and spectroscopy of these resonances is widely used to study the magnetic, structural and dynamical properties of matter.sup.4,5. It has been shown that the power and scope of Mössbauer spectroscopy can be greatly improved using various control techniques.sup.6-16. However, coherent control of atomic nuclei using suitably shaped near-resonant X-ray fields remains an open challenge. Here we demonstrate such control, and use the tunable phase between two X-ray pulses to switch the nuclear exciton dynamics between coherent enhanced excitation and coherent enhanced emission. We present a method of shaping single pulses delivered by state-of-the-art X-ray facilities into tunable double pulses, and demonstrate a temporal stability of the phase control on the few-zeptosecond timescale. Our results unlock coherent optical control for nuclei, and pave the way for nuclear Ramsey spectroscopy.sup.17 and spin-echo-like techniques, which should not only advance nuclear quantum optics.sup.18, but also help to realize X-ray clocks and frequency standards.sup.19. In the long term, we envision time-resolved studies of nuclear out-of-equilibrium dynamics, which is a long-standing challenge in Mössbauer science.sup.20. Suitably shaped X-ray pulses are used to coherently steer the quantum dynamics of atoms' nuclei rather than their electrons, with few-zeptosecond temporal stability of the phase control., Author(s): Kilian P. Heeg [sup.1] , Andreas Kaldun [sup.1] , Cornelius Strohm [sup.2] , Christian Ott [sup.1] , Rajagopalan Subramanian [sup.1] , Dominik Lentrodt [sup.1] , Johann Haber [sup.2] , [...]

Current hardware approaches to biomimetic or neuromorphic artificial intelligence rely on elaborate transistor circuits to simulate biological functions. However, these can instead be more faithfully emulated by higher-order circuit elements that naturally express neuromorphic nonlinear dynamics.sup.1-4. Generating neuromorphic action potentials in a circuit element theoretically requires a minimum of third-order complexity (for example, three dynamical electrophysical processes).sup.5, but there have been few examples of second-order neuromorphic elements, and no previous demonstration of any isolated third-order element.sup.6-8. Using both experiments and modelling, here we show how multiple electrophysical processes--including Mott transition dynamics--form a nanoscale third-order circuit element. We demonstrate simple transistorless networks of third-order elements that perform Boolean operations and find analogue solutions to a computationally hard graph-partitioning problem. This work paves a way towards very compact and densely functional neuromorphic computing primitives, and energy-efficient validation of neuroscientific models. Electrophysical processes are used to create third-order nanoscale circuit elements, and these are used to realize a transistorless network that can perform Boolean operations and find solutions to a computationally hard graph-partitioning problem., Author(s): Suhas Kumar [sup.1] , R. Stanley Williams [sup.2] , Ziwen Wang [sup.3] Author Affiliations: (1) Hewlett Packard Labs, Palo Alto, USA (2) Texas A&M University, College Station, USA (3) [...]

The rate of cell growth is crucial for bacterial fitness and drives the allocation of bacterial resources, affecting, for example, the expression levels of proteins dedicated to metabolism and biosynthesis.sup.1,2. It is unclear, however, what ultimately determines growth rates in different environmental conditions. Moreover, increasing evidence suggests that other objectives are also important.sup.3-7, such as the rate of physiological adaptation to changing environments.sup.8,9. A common challenge for cells is that these objectives cannot be independently optimized, and maximizing one often reduces another. Many such trade-offs have indeed been hypothesized on the basis of qualitative correlative studies.sup.8-11. Here we report a trade-off between steady-state growth rate and physiological adaptability in Escherichia coli, observed when a growing culture is abruptly shifted from a preferred carbon source such as glucose to fermentation products such as acetate. These metabolic transitions, common for enteric bacteria, are often accompanied by multi-hour lags before growth resumes. Metabolomic analysis reveals that long lags result from the depletion of key metabolites that follows the sudden reversal in the central carbon flux owing to the imposed nutrient shifts. A model of sequential flux limitation not only explains the observed trade-off between growth and adaptability, but also allows quantitative predictions regarding the universal occurrence of such tradeoffs, based on the opposing enzyme requirements of glycolysis versus gluconeogenesis. We validate these predictions experimentally for many different nutrient shifts in E. coli, as well as for other respiro-fermentative microorganisms, including Bacillus subtilis and Saccharomyces cerevisiae. A model of sequential flux bottlenecks explains a universal trade-off between steady-state growth and physiological adaptation time in bacteria exposed to fluctuating growth conditions., Author(s): Markus Basan [sup.1] [sup.2] , Tomoya Honda [sup.3] , Dimitris Christodoulou [sup.2] , Manuel Hörl [sup.2] , Yu-Fang Chang [sup.1] , Emanuele Leoncini [sup.1] , Avik Mukherjee [sup.1] , [...]

ABSTRACT. Laughery Bluff and Dogwood Nature Preserves are two old-growth forest stands in southeastern Indiana (Ripley County). The stands, which are part of Versailles State Park, are unique in that [...]

We study the relationship between economic policy uncertainty and systemic risk for nine European countries in January 2010-September 2016 by applying conventional Granger causality tests and advanced techniques (wavelet analysis and Bayesian VARs). The country-level analyses show that the lead-lag patterns vary considerably in the short and longer run as well as at different frequencies. Nonetheless, the pivotal role of uncertainty tends to strengthen over longer time horizons (at lower frequencies) and in the BVAR framework. This is true for financially fragile economies such as Ireland, Italy, Russia, Spain. A panel BVAR model confirms this finding for the whole sample. Keywords Bayesian VAR * Dynamic factor model * Economic policy uncertainty * Systemic risk * Wavelet coherence JEL Classification C32 * C38 * G32, Introduction Systemic risk has become one of the central issues in macro-financial research. It emerges from the financial sector and has a potentially severe impact on the broader economy. The [...]

Montreal has significant seismic risk due to the combination of moderate seismicity, high population density, and vulnerable infrastructure. An important tool in damage and risk assessment is a scenario shakemap, which shows the expected ground shaking intensity distribution patterns. In this study, we use regional ground motion and site response evaluations to generate scenario shakemaps for Montreal. The impact of event location on expected ground motions and intensities was tested by considering the occurrence of a scenario (a given magnitude event) at various locations, where the scenarios are defined based on an analysis of the most likely future event locations. Variability in near surface geology plays an important role in earthquake ground shaking; we use microzonation information from Montreal to assess the expected site amplification effects. The results of this study may be used as input to seismic risk studies for Montreal. Key words: shakemap, ground motion prediction equation, site amplification. Montreal est exposee a un risque sismique eleve qui resulte de la combinaison d'une sismicite moyenne, de forte densite de population et de la presence d'infrastructures vulnerables. Un outil important devaluation des dommages et risques associes aux seismes est la <> (carte de representation des mouvements du sol produits par un seisme), qui montre les differents scenarios envisageables de repartition de l'intensite des secousses sismiques. Dans la presente etude, nous utilisons les resultats devaluation des mouvements du sol au niveau regional et des phenomenes observes a differents endroits lors de seismes, et ce afin de creer des shakemaps pour l'agglomeration de Montreal. On a etudie l'influence de la localisation des secousses sur les mouvements du sol et leur intensite en examinant l'occurrence d'un scenario (evenement de magnitude donnee) a differents endroits, les scenarios etant etablis a partir d'une analyse des endroits les plus probables des futurs evenements sismiques. Les variations de la geologie de subsurface jouent un role important dans les secousses sismiques lors de tremblements de terre. Nous utilisons des donnees de microzonage provenant de Montreal pour evaluer les effets de l'amplification a un endroit donne. Les resultats de la presente etude peuvent etre utilises comme donnees de depart pour revaluation des risques sismiques dans l'agglomeration montrealaise. [Traduit par la Redaction] Mots-cles: shakemap, equation de prediction des mouvements du sol, amplification a un endroit donne., Introduction Shakemaps (Wald et al. 1999b) are maps that show the spatial distribution of recorded and estimated peak ground motions (velocity, acceleration, and response spectra) and estimate the corresponding felt [...]

Somatic TP53 mutations are highly prevalent in therapy-related acute myeloid leukaemia and myelodysplastic syndrome, which arise as complications of cytotoxic chemotherapy or radiotherapy; although it was believed that these TP53 mutations are directly induced by cytotoxic therapy, new data indicate that they predate cytotoxic therapy and that haematopoietic progenitors harbouring these pre-existing mutations may selectively expand after exposure to chemotherapy or radiotherapy. TP53 mutations predate cytotoxic therapy The clonal haematopoietic disorders known as therapy-related acute myeloid leukaemia (t-AML) and therapy-related myelodysplastic syndrome (t-MDS) typically develop 1 to 5 years after exposure to chemotherapy or radiotherapy. TP53 mutations are selectively enriched in t-AML/t-MDS, and were thought to be directly induced by cytotoxic therapy. Now Daniel Link and colleagues present genome sequencing data that suggest the TP53 mutations predate cytotoxic therapy. It appears that rare haematopoietic stem/progenitor cells in blood or bone marrow carry age-related TP53 mutations, and that these cells undergo clonal expansion only after selective pressure applied by chemotherapy. Therapy-related acute myeloid leukaemia (t-AML) and therapy-related myelodysplastic syndrome (t-MDS) are well-recognized complications of cytotoxic chemotherapy and/or radiotherapy.sup.1. There are several features that distinguish t-AML from de novo AML, including a higher incidence of TP53 mutations.sup.2,3, abnormalities of chromosomes 5 or 7, complex cytogenetics and a reduced response to chemotherapy.sup.4. However, it is not clear how prior exposure to cytotoxic therapy influences leukaemogenesis. In particular, the mechanism by which TP53 mutations are selectively enriched in t-AML/t-MDS is unknown. Here, by sequencing the genomes of 22 patients with t-AML, we show that the total number of somatic single-nucleotide variants and the percentage of chemotherapy-related transversions are similar in t-AML and de novo AML, indicating that previous chemotherapy does not induce genome-wide DNA damage. We identified four cases of t-AML/t-MDS in which the exact TP53 mutation found at diagnosis was also present at low frequencies (0.003-0.7%) in mobilized blood leukocytes or bone marrow 3-6 years before the development of t-AML/t-MDS, including two cases in which the relevant TP53 mutation was detected before any chemotherapy. Moreover, functional TP53 mutations were identified in small populations of peripheral blood cells of healthy chemotherapy-naive elderly individuals. Finally, in mouse bone marrow chimaeras containing both wild-type and Tp53.sup.+/- haematopoietic stem/progenitor cells (HSPCs), the Tp53.sup.+/- HSPCs preferentially expanded after exposure to chemotherapy. These data suggest that cytotoxic therapy does not directly induce TP53 mutations. Rather, they support a model in which rare HSPCs carrying age-related TP53 mutations are resistant to chemotherapy and expand preferentially after treatment. The early acquisition of TP53 mutations in the founding HSPC clone probably contributes to the frequent cytogenetic abnormalities and poor responses to chemotherapy that are typical of patients with t-AML/t-MDS., Author(s): Terrence N. Wong [sup.1] , Giridharan Ramsingh [sup.2] , Andrew L. Young [sup.3] , Christopher A. Miller [sup.4] , Waseem Touma [sup.1] , John S. Welch [sup.1] [sup.5] , [...]

Therapy-related acute myeloid leukaemia (t-AML) and therapy-related myelodysplastic syndrome (t-MDS) are well-recognized complications of cytotoxic chemotherapy and/or radiotherapy (1). There are several features that distinguish t-AML from denovo AML, including a higher incidence of TP53 mutations (2,3), abnormalities of chromosomes 5 or 7, complex cytogenetics and a reduced response to chemotherapy (4). However, it is not clear how prior exposure to cytotoxic therapy influences leukaemogenesis. In particular, the mechanism by which TP53 mutations are selectively enriched in t-AML/t-MDS is unknown. Here, by sequencing the genomes of 22 patients with t-AML, we show that the total number of somatic single-nucleotide variants and the percentage of chemotherapy-related transversions are similar in t-AML and denovo AML, indicating that previous chemotherapy does not induce genome-wide DNA damage. W e identified four cases of t-AML/ t-MDS in which the exact TP53 mutation found at diagnosis was also present at low frequencies (0.003-0.7%) in mobilized blood leukocytes or bone marrow 3-6 years before the development of t-AML/tMDS, including two cases in which the relevant TP53 mutation was detected before any chemotherapy. Moreover, functional TP53 mutations were identified in small populations of peripheral blood cells of healthy chemotherapy-naive elderly individuals. Finally, in mouse bone marrow chimaeras containing both wild-type and [Tp53.sup.+/-] haematopoietic stem/progenitor cells (HSPCs), the [Tp53.sup.+/-] HSPCs preferentially expanded after exposure to chemotherapy. These data suggest that cytotoxic therapy does not directly induce TP53 mutations. Rather, they support a model in which rare HSPCs carrying age-related TP53 mutations are resistant to chemotherapy and expand preferentially after treatment. The early acquisition of TP53 mutations in the founding HSPC clone probably contributes to the frequent cytogenetic abnormalities and poor responses to chemotherapy that are typical of patients with t-AML/t-MDS., t-AML and t-MDS are clonal haematopoietic disorders that typically develop 1-5 years after exposure to chemotherapy or radiotherapy (1). To understand better how prior cytotoxic therapy contributes to the high [...]