Slow Trajectory Research Articles

Real-Time Planner in the Operational Space for the Automatic Handling of Kinematic Constraints

Planning problems in the operational space are characterized by implementation issues that do not occur in the joint space. For example, depending on the manipulator pose, relatively slow trajectories in the operational space could require unfeasible joint speeds, thus causing the degeneration of the system performances: Path tracking errors certainly increase but, in the worst situations, the manipulator must be stopped in order to prevent the system instability. This paper proposes a real-time planner in the operational space that is able to generate trajectories subject to dynamic constraints and devised according to the path-velocity decomposition approach. The feasibility is achieved by means of an automatic scaling system that, starting from a possibly unfeasible trajectory, modifies its longitudinal velocity in order to fulfill a given set of kinematic constraints, thus preserving an accurate path tracking. The scaling system promptly reacts to critical configurations through minimum-time transients. The proposed approach has been tested on an actual anthropomorphic manipulator by executing 6D trajectories. Note to Practitioners - The accurate path tracking must be guaranteed especially when trajectories are planned in the operational space. Unfortunately, path tracking worsens every time system limits are exceeded. The trajectory generator proposed in this paper is specifically designed for non-redundant manipulators and it is equipped with a scaling system that automatically modifies the speed of the end effector in order to guarantee an accurate path tracking. Several kinematic constraints are handled at the same time. Joint velocities are kept below the manufacturer's limits, while joint accelerations are bounded in order to achieve smooth movements. The system is also able to constrain the kinematics of the end effector. For example, in order to reduce the mechanical stress on the payload and to avoid the excitation of elastic modes, additional bounds on the velocities and accelerations of the end effector are considered and managed. The planner can also be used to generate minimum-time constrained trajectories in real-time. To this purpose, further constraints on the longitudinal velocities and accelerations have been introduced. Differently from alternative approaches, the proposed planning scheme does not require any interaction with the controller. This is an advantage, since controllers of industrial manipulators are typically not accessible or modifiable, while, in turn, proprietary trajectory planners can normally be replaced with ad-hoc implementations. The scaling system can be easily expanded in order to handle additional constraints. The trajectory smoothness, for example, can be improved by managing the jerk bounds, so that the ongoing research activity is currently focused on that target. In the same way, it could also be possible to handle some dynamic constraints, but this would impose the introduction of mutual interactions between the scaling system and the central control unit.

Associations between infant feeding and the size, tempo and velocity of infant weight gain: SITAR analysis of the Gemini twin birth cohort.

Objective:Infant growth trajectories, in terms of size, tempo and velocity, may programme lifelong obesity risk. Timing of breastfeeding cessation and weaning are both implicated in rapid infant growth; we examined the association of both simultaneously with a range of growth parameters.Design:Longitudinal population-based twin birth cohort.Subjects:The Gemini cohort provided data on 4680 UK infants with a median of 10 (interquartile range=8–15) weight measurements between birth and a median of 6.5 months. Age at breastfeeding cessation and weaning were reported by parents at mean age 8.2 months (s.d.=2.2, range=4–20). Growth trajectories were modelled using SuperImposition by Translation And Rotation (SITAR) to generate three descriptors of individual growth relative to the average trajectory: size (grams), tempo (weeks, indicating the timing of the peak growth rate) and velocity (% difference from average, reflecting mean growth rate). Complex-samples general linear models adjusting for family clustering and confounders examined associations between infant feeding and SITAR parameters.Results:Longer breastfeeding (>4 months vs never) was independently associated with lower growth velocity by 6.8% (s.e.=1.3%) and delayed growth tempo by 1.0 (s.e.=0.2 weeks), but not with smaller size. Later weaning (⩾6 months vs <4 months) was independently associated with lower growth velocity by 4.9% (s.e.=1.1%) and smaller size by 102 g (s.e.=25 g).Conclusions:Infants breastfed for longer grew slower for longer after birth (later peak growth rate) but were no different in size, while infants weaned later grew slower overall and were smaller but the timing of peak growth did not differ. Slower trajectories with a delayed peak in growth may have beneficial implications for programming later obesity risk. Replication in cohorts with longer follow-up, alternative confounding structures or randomised controlled trials are required to confirm the long-term effects and directionality, and to rule out residual confounding.

Vygotsky and Piaget: Scientific concepts

Introduction: Basic distinctionsJean Piaget's perspective is often compared with Lev Vygotsky's because both authors acknowledged the active role of humans in the construction of knowledge. However, they differ in that, unlike Piaget, Vygotsky thought that the assimilation of new information does not have to wait for an appropriate level of development but must, on the contrary, produce that development: organization of scientific concepts in children constitutes an important practical problem for schools (Vygotsky, 1934/2007, p. 222).Piaget framed his cognitive theory in biological context, repeatedly referring to his intellectual roots in Immanuel Kant's, C. H. Waddington's, and Henri Bergson's thoughts, as well as focusing on evolutionism and structuralism. He based his orientation and his psychogenetic theory on five principles: reason is rooted in action; it stands on two a priori mechanisms, adaptation and organization; reason is pure and non-temporal; structuralism is an independent concept.Piaget seems to have been mostly interested in spontaneous concepts. In his research, he stated that the development of formal reasoning and scientific concepts depends on the experience of cognitive conflict, which promotes imbalance, thus forcing the emergence of successive new assimilations. The reorganization of thought then takes place naturally. This description of the development of higher mental functions has been designated nonhistorical in opposition to Vygotsky's historical, or cultural, understanding.Vygotsky's work was strongly influenced by Karl Marx and Friedrich Engels, by Charles Darwin's evolutionism, and by Spinoza's dynamic insights on universal development. Based on the ideas of these philosophers he defined the five distinctive principles that should orient epistemological research: psychology is the science of historical human being; higher psychological processes originate in social action; there exist three distinct classes of mediators: signs/instruments, individual acts, and interpersonal relationships; specific functions as well as social reality emerge from transformational acts or work; there exists fundamental unity between body and mind--that is, people global beings.According to Vygotsky, spontaneous and scientific conceptual structures both develop through continuous interaction between individual partners in an historical context and don't result from cognitive conflicts between two thought processes. In his view, spontaneous and scientific concepts belong to dialectical unity and become organized together along opposite paths: spontaneous concepts proceed from the concrete to the abstract; scientific concepts, from the abstract to the concrete.Spontaneous concepts primarily inductive, nonsystematic, and based on perceptual attributes; they embody elementary aspects of experienced reality and imbued with life and dynamics. In turn, scientific concepts, culturally formulated and transmitted, provide structure; they elevate the horizon of consciousness and its ponderings. Scientific concepts grow downward through the involvement of spontaneous concepts; spontaneous concepts grow upward through the use of scientific concepts. In Vygotsky's words:By forcing its slow upward trajectory, an everyday concept paves the way for scientific concept and its descendant development. It creates series of structures necessary for the evolution of the most primitive and elementary aspects of concept, giving it body and vitality. Scientific concepts, in turn, provide structures for the upward development of spontaneous concepts in relation to consciousness and deliberate use by the child. (1934/2003, pp. 93-94)Thus, everyday concepts emerge from dealings with concrete situations: these concepts are ontological, intuitive categories developed by each individual not counting on formal schooling. Consequently, they nonsystematic, qualified by contextual situations, their associations being affected by concrete analogies or related to isolated generalizations (Damazio, 2000, p. …

A Novel Direct Inverse Modeling Approach for Hysteresis Compensation of Piezoelectric Actuator in Feedforward Applications

The Prandtl-Ishlinskii (PI) model is widely utilized in hysteresis modeling and compensation of piezoelectric actuators. For systems with rate-independent hysteresis, the inverse PI model is analytically feasible and it can be adopted as a feedforward compensator for the hysteretic nonlinearity of piezoelectric actuators. However, for the rate-dependent PI model, the applicable valid inversion methodology is not yet available. Although simply replacing all the rate-independent terms in the conventional inversion law with the rate-dependent terms can achieve acceptable results at very slow trajectories. However, a large theoretical modeling error is inevitable at fast trajectories, which is investigated through simulations. This paper proposes a new direct approach to derive the inverse PI model directly from experimental data. As no inversion calculation is involved, the proposed direct approach is efficient and the theoretical modeling error can be avoided. In order to validate the accuracy of the direct approach, a number of experiments have been implemented on a piezo-driven compliant mechanism by utilizing the inverse PI model as a feedforward controller. The tracking performance of the mechanism is significantly improved by the direct approach.

Valence and vertical space: Saccade trajectory deviations reveal metaphorical spatial activation

Concepts of positive and negative valence are metaphorically structured in space (e.g., happy is up, sad is down). In fact, coupling a conceptual task (e.g., evaluating words as positive or negative) with a visuospatial task (e.g., identifying stimuli above or below fixation) often gives rise to metaphorical congruency effects. For instance, after reading a positive concept, visual target processing is facilitated above fixation. However, it is possible that tasks requiring upwards and downwards attentional orienting artificially strengthen the link between vertical space and semantic valence. For this reason, in the present study the vertical axis was uncoupled from the response axis. Participants made eye movements along the horizontal axis after reading positive or negative affect words, while their saccade movement trajectories were recorded. Based on previous research on saccade trajectory deviation, we predicted that fast saccade trajectories curve towards the salient segment of space, whereas slow saccade trajectories would curve away from the salient segment. Examining saccadic trajectories revealed a pattern of deviations along the vertical axis consistent with the metaphorical congruency account, although this pattern was mainly driven by positive concepts. These results suggest that semantic processing of valence can automatically recruit spatial features along the vertical axis.

Hiding or dead? A computationally efficient model of selective fisheries mortality

100 years after Rosa Lee (1912) showed that higher mortality on faster growing fish can alter length-at-age distributions in fish populations, we present a computationally-efficient and parsimonious method for modeling size-selective mortality within a commonly-used assessment model, Stock Synthesis. Stock Synthesis allows the normal distribution of length-at-age to be partitioned into three or five overlapping platoons with slow, medium, or fast growth trajectories. The platoons are tracked separately in the model, and experience different degrees of size-selective fishing pressure and mortality, but are assumed to be unobservable except through changes in the length distribution. Simulations are used to explore this phenomenon in conjunction with dome-shaped selectivity, an alternative explanation for observing fewer than expected large fish in sampled data, but with very different implications for population productivity. For data simulated both with and without platoons, misspecification of the assumptions about growth are found to bias model results, with selectivity often incorrectly identified as the cause of fewer observations of larger fish. Trends in dome-shaped selectivity were explored as a potential diagnostic of model misspecification.

Trajectories of Recovery and Dysfunction after Acute Illness, with Implications for Clinical Trial Design

Trajectories of Recovery and Dysfunction after Acute Illness, with Implications for Clinical Trial Design

Molecular dynamics of excited state intramolecular proton transfer: 3-hydroxyflavone in solution

The ultrafast enol-keto photoisomerization in the lowest singlet excited state of 3-hydroxyflavone is investigated using classical molecular dynamics in conjunction with empirical valence bond (EVB) potentials for the description of intramolecular interactions, and a molecular mechanics and variable partial charge model, dependent on transferring proton position, for the description of solute-solvent interactions. A parallel multi-level genetic program was used to accurately fit the EVB potential energy surfaces to high level ab initio data. We have studied the excited state intramolecular proton transfer (ESIPT) reaction in three different solvent environments: methylcyclohexane, acetonitrile, and methanol. The effects of the environment on the proton transfer time and the underlying mechanisms responsible for the varied time scales of the ESIPT reaction rates are analyzed. We find that simulations with our EVB potential energy surfaces accurately reproduce experimentally determined reaction rates, fluorescence spectra, and vibrational frequency spectra in all three solvents. Furthermore, we find that the ultrafast ESIPT process results from a combination of ballistic transfer, and intramolecular vibrational redistribution, which leads to the excitation of a set of low frequency promoting vibrational modes. From this set of promoting modes, we find that an O-O in plane bend and a C-H out of plane bend are present in all three solvents, indicating that they are fundamental to the ultrafast proton transfer. Analysis of the slow proton transfer trajectories reveals a solvent mediated proton transfer mechanism, which is diffusion limited.

Accuracy of growth chart use in monitoring and assessing under-nutrition in Kenya

Aims To find out how well healthcare workers in Kenya plot and interpret information on growth charts. Methods Doctors and clinical officers (12), nurses, nutritionists and community health care workers (27) who were actively involved in growth monitoring were surveyed at primary care clinics around Nairobi, Kenya in June 2011. They completed questionnaires which included plotting of weights at ages 2, 6 and 9 months using the road to health chart (RTH) currently in use in Kenya and interpretation of 8 plotted scenarios permutated through 2 versions of the questionnaire, with each respondent rating two growth trajectories from a well baby clinic and two for children being treated for malnutrition. Results There were high levels of plotting errors; up to 78% (29) plotted weights less than 0.5 kg and 41% (16) plotted ages more than 0.5 months from the true value. This seemed to reflect the difficulty of plotting on the RTH chart. Nurses and nutritionists were rather more accurate in plotting charts compared to doctors and clinical officers. From the well-baby clinic scenario, 30% (18 out of 60) correctly identified a slow weight trajectory (fall of 2 weight SD) while 65% (11 out of 17) recognised steady growth. In the malnutrition clinic scenarios 39% (15 out of 39) recognised catch up growth (rise of 1 weight SD). For children seen in well baby clinics 70% (41 out of 59) recognised the need to offer extra care to a child with slow weight gain but 57% (9 out of 16) stated extra care was needed for a small child who had been growing steadily (−2 SD). For the malnutrition clinic scenario, 94% (36 out of 38) healthcare workers recognised that a child without catch up required extra care, but 72% (32 out of 39) also felt this was needed in a child with catch up growth. Conclusion Growth charts were not plotted accurately, partly due to poor chart design. Healthcare workers did not seem to discriminate between size and weight gain, with the result that they seemed to be concerned about healthy growth patterns when seen in relatively small children.

The Relationship between Economic Growth and Transformation of Democracy of Bangladesh (A Historical and Strategic Analysis)

The Relationship between Economic Growth and Transformation of Democracy of Bangladesh (A Historical and Strategic Analysis)

Effects of Priming Exercise on V˙O2 Kinetics and the Power-Duration Relationship

This study aimed to investigate the influence of prior heavy- and severe-intensity exercise on the oxygen uptake (V·O₂) kinetics and the power-duration relationship. Ten cyclists performed 13 exercise tests during a 4-wk period, consisting of a ramp test to determine the gas exchange threshold (GET) and the peak V·O₂, followed by a series of square-wave tests to exhaustion under three conditions: no prior exercise (control), prior heavy exercise (6 min at a work rate above GET but below critical power [CP)], and prior severe exercise (6 min at a work rate above the CP). Pulmonary gas exchange was measured throughout the exhaustive exercise bouts and the parameters of the power-duration relationship (CP and the curvature constant, W') were determined from the linear work-time model. Prior heavy exercise increased the amplitude of the primary V·O₂ response (by ∼ 0.19 ± 0.28 L·min(-1), P = 0.001), reduced the V·O₂ slow component trajectory (by 0.04 ± 0.09 L·min(-2), P = 0.002), and increased the time to exhaustion (by ∼ 52 ± 92 s, P = 0.005). The CP was unchanged (control vs prior heavy: 284 ± 47 vs 283 ± 44 W; 95% confidence interval, -7 to 5 W), whereas the W' was increased by heavy-intensity priming (16.0 ± 4.8 vs 18.7 ± 4.8 kJ; 95% confidence interval, 0.3-5.2 kJ). Severe-intensity exercise had a similar effect on the V·O₂ kinetics but had no effect on the time to exhaustion, the CP (275 ± 45 W), or the W' (16.7 ± 4.7 kJ). Prior heavy-intensity exercise primes the V·O₂ kinetics and increases the amount of work that can be performed above the CP.

Renewal theory of coupled neuronal pools: Stable states and slow trajectories

A theory is provided to analyze the dynamics of delay-coupled pools of spiking neurons based on stability analysis of stationary firing. Transitions between stable and unstable regimes can be predicted by bifurcation analysis of the underlying integral dynamics. Close to the bifurcation point the network exhibits slowly changing activities and allows for slow collective phenomena like continuous attractors.

Stochastic Inflation in Compact Extra Dimensions

While moving down the potential on its classical slow roll trajectory, the inflaton field is subject to quantum jumps, which take it up or down the potential at random. In "stochastic inflation", the impact of these quantum jumps is modeled by smoothing out the field over (at least) Hubble-patch sized domains and treating fluctuations on smaller scales as noise. The inflaton thus becomes a stochastic process whose values at a given time are calculated using its probability distribution. We generalize this approach for non-canonic kinetic terms of Dirac Born Infeld (DBI) type and investigate the resulting modifications of the field's trajectory. Since models of DBI inflation arise from string-inspired scenarios in which the scalar field has a geometric interpretation, we insist that field value restrictions imposed by the model's string origin must be respected at the quantum level.

Contributors to excess antagonist activity during movement in children with secondary dystonia due to cerebral palsy

Children with secondary dystonia due to cerebral palsy exhibit abnormal upper extremity postures and slow voluntary movement. However, the interaction between abnormal postures and abnormal movement in dystonia is still unclear. Some mechanisms by which postures are maintained in dystonia include stretch reflexes, overflow of muscle activation to other muscles, and direct coactivation of antagonist muscles. This study explored the independent contributions of each of these postural mechanisms to abnormal biceps brachii (antagonist) activity during elbow extension, which slows movement. A linear model of biceps activation as a function of velocity-dependent reflexes, triceps-dependent overflow, and direct drive to the biceps was fitted to experimental data from 11 children and young adults with secondary dystonia due to cerebral palsy and 11 age-matched control subjects. Subjects performed elbow extension movements against each of four levels of resistance without perturbations or in each of two perturbation conditions. Results show that biceps activity in children with dystonia consists of significant contributions of reflex activation, overflow from triceps, and direct muscular drive. Additionally, stretch reflexes during movement are shown to be elevated at three latencies after stretch. These findings suggest that there are postural mechanisms involved in stabilizing the elbow along its slow trajectory during movement and provide a quantitative basis for the selection of treatments targeting specific impairments in children with secondary dystonia due to cerebral palsy.

Turbulent phenomena in protein folding

Protein folding and hydrodynamic turbulence are two long-standing challenges, in molecular biophysics and fluid dynamics, respectively. The theories of these phenomena have been developed independently and used different formalisms. Here we show that the protein folding flows can be surprisingly similar to turbulent fluid flows. Studying a benchmark model protein (an SH3 domain), we have found that the flows for the slow folding trajectories of the protein, in which a partly formed N- and C-terminal β sheet hinders the RT loop from attaching to the protein core, have many properties of turbulent flows of a fluid. The flows are analyzed in a three-dimensional (3D) space of collective variables, which are the numbers of native contacts between the terminal β strands, between the RT loop and the protein core, and the rest of the native contacts. We have found that the flows have fractal nature and are filled with 3D eddies; the latter contain strange attractors, at which the tracer flow paths behave as saddle trajectories. Two regions of the space increment have been observed, in which the flux variations are self-similar with the scaling exponent h=1/3, in surprising agreement with the Kolmogorov inertial range theory of turbulence. In one region, the cascade of protein rearrangements is directed from larger to smaller scales (net folding), and in the other, it is oppositely directed (net unfolding). Folding flows for the fast trajectories are essentially "laminar" and do not have the property of self-similarity. Based on the results of our study, we infer, and support this inference by simulations, that the origin of the similarity between the protein folding and turbulent motion of a fluid is in a cascade mechanism of structural transformations in the systems that underlies these phenomena.

The Rifled Musket in Civil War Combat: Reality and Myth (review)

Reviewed by: The Rifled Musket in Civil War Combat: Reality and Myth D. Scott Hartwig The Rifled Musket in Civil War Combat: Reality and Myth. By Earl J. Hess (Lawrence: University Press of Kansas, 2008. Pp. 288. Cloth, $29.95.) It is commonly believed that the introduction of the rifled musket on a mass scale revolutionized warfare during the American Civil War but that the generals failed to appreciate its real impact and blindly continued to employ outmoded tactics, until 1864 when losses drove both armies to dig in and fight from entrenchments. Earl Hess challenges this conclusion, arguing that many of the assumptions about the rifled musket's impact on the war either do not hold up under careful study or are exaggerated. His evidence is impressive and persuasive. Hess builds the context of his case with a brief but adequate survey of the history of the smoothbore and rifled musket heritage before the Civil War. This is followed by a review of both the U.S. and C.S. governments' efforts to equip their soldiers with rifled muskets and an examination of the gun culture of Civil War soldiers. The heart of the book is the study of the rifled musket in battle, which includes chapters on skirmishing and sharpshooting/sniping. [End Page 230] By analyzing data about numerous battles from a variety of contemporary sources Hess draws some interesting conclusions. Most infantry combat with rifled muskets took place at relatively short range, an average of just under 100 yards. That combat did not regularly occur beyond this range had to do with terrain but more with the problems inherent with the parabolic trajectory of the minie ball. To fire at a target, say 300 yards away, the individual soldier had to set the sight on his rifle for the range before firing. Because of the slow trajectory of the bullet, it traveled in an arc to reach its target at longer ranges. For over the third of the distance a bullet fired at a target at this range traveled above the height of an average man, which meant that anyone advancing in this particular zone was safe. Since soldiers did very little target practice and the process of hitting targets at longer ranges was complicated for combat conditions, most infantry officers did not let their men begin firing until the enemy was within the same range of a smoothbore musket, which was effective. Since combat generally took place within the effective range of smoothbores, Hess argues that the linear tactics developed for smoothbore weapons remained relevant and effective and were used successfully on numerous battlefields. It is difficult to disagree with this conclusion since the rate of fire of the rifled musket was no greater than that of the smoothbore, and there had been no improvements in command and control at the tactical level. Command still consisted of voice or hand signals. But eventually both armies began to dig in regularly and the standard explanation for this is the lethality of the rifled musket forced men to burrow to reduce casualties. Hess disputes this and contends that what drove the trench combat which characterized the Atlanta Campaign and Overland Campaign of 1864 was the daily close proximity of the two armies. With constant contact the possibility of enemy attack was ever present, which created the need to fortify lines to defend against it, and that even had the armies been armed with smoothbores they would have done so. To support his case that rifle muskets did not render combat more deadly, Hess draws a comparison between the Civil War's major battles and sixteen major battles fought with smoothbores in Europe from 1704 to 1815. The battles fought with smoothbores were far bloodier. Hess has not written the last word on the rifled musket and its influence on the Civil War, but he has produced an important, well-documented book that provides the first systematic study of the rifle's true impact on the battlefield. [End Page 231] D. Scott Hartwig Gettysburg National Military Park Copyright © 2010 The Kent State University Press

Folding of a SH3 Domain: Standard and “Hydrodynamic” Analyses

Discrete molecular dynamics has been used to study the folding of a SH3 domain with a Calpha-based Go-model at a temperature within the native state stability region. A standard analysis of the folding process, based on consideration of the mean-force (free energy) surfaces, contact maps and folding time distributions, is complemented by a "hydrodynamic" description of folding flows (Chekmarev et al., PRL, 2008, 018107) using two and three collective variables. Two types of folding trajectories (fast and slow) follow essentially different routes in the final stage of folding. The hydrodynamic description makes possible the calculation of folding flows corresponding to these routes. The results show that the probability flows do not correspond to the free energy surface and that vortex formation is involved in the slow trajectories. Comparison of the simulation results with the experimental data suggests that the two-state kinetics observed for Fyn and Src SH3 domain folding are associated with the slow trajectories, in which a partly formed N- and C-terminal beta sheet hinders the RT-loop from attaching to the protein core; the fast trajectories are not observed because they are in the dead time (1 ms) of the experiments.

Larval over‐wintering: plasticity in the timing of life‐history events in the common frog

AbstractIn ectothermic animals living in temperate regions, winter is a critical time. During early ontogeny, the stage or size an individual reaches at the onset of winter can have a significant effect on its survival and other life‐history characteristics. Generally, temperate amphibian larvae complete metamorphosis in the summer and spend their first winter as juveniles. However, some anuran amphibians show variation in this aspect of their life history, with some individuals remaining as aquatic larvae during winter. We investigated growth and development during the larval period of Rana temporaria at a field where over‐wintering has been recorded. In the laboratory, we investigated whether larval over‐wintering could be induced at temperatures equivalent to those recorded in the field pond; this was done at both high and low food availability. Larvae within the field pond showed a bimodal distribution in developmental stage as early as July, when temperatures were still increasing, separating individuals that would metamorphose and over‐winter as juveniles from those that would spend the winter as larvae. Individuals that over‐wintered as larvae remained at a relatively undeveloped larval stage throughout the summer and autumn. The decision on whether to over‐winter as a larva appears to be made relatively early in the season. Those individuals that adopt this slow developmental trajectory may benefit in being able to metamorphose at a larger size in Spring. In the laboratory, mean temperature and food availability affected development and growth, but did not affect the life‐history stage at which individuals over‐wintered. Our results suggest that there are other factors, in addition to temperature and food availability that contribute to the observed plasticity in development pattern and over‐wintering strategy.

Functional integration across a gradient of corticostriatal channels controls UP state transitions in the dorsal striatum

Coordinated near-threshold depolarized states in cortical and striatal neurons may contribute to form functionally segregated channels of information processing. Recent anatomical studies have identified pathways that could support spiraling interactions across corticostriatal channels, but a functional outcome of such spiraling remains to be identified. Here, we examined whether plateau depolarizations (UP states) in striatal neurons relate better to active epochs in local field potentials recorded from closely related cortical areas than to those recorded in less-related cortical areas. Our results show that, in anesthetized rats, the coordination between cortical areas and striatal regions obeys a mediolateral gradient and keeps track of slow wave trajectory across the neocortex. Moreover, activity in one cortical area induced phase advances in UP state onset and phase delays in UP state termination in nonmatching striatal regions, reflecting the existence of functional connections that could encode large-scale interactions between corticostriatal channels as subthreshold influences on striatal projection neurons.

Drift of slow variables in slow-fast Hamiltonian systems

We study the drift of slow variables in a slow-fast Hamiltonian system with several fast and slow degrees of freedom. Keeping the slow variables frozen, for any periodic trajectory of the fast subsystem we define an action. For a family of periodic orbits, the action is a scalar function of the slow variables and can be considered as a Hamiltonian function which generates some slow dynamics. These dynamics depend on the family of periodic orbits. Assuming that for the frozen slow variables the fast system has a pair of hyperbolic periodic orbits connected by two transversal heteroclinic trajectories, we prove that for any path composed of a finite sequence of slow trajectories generated by action Hamiltonians, there is a trajectory of the full system whose slow component shadows the path.