Coexistence of stability and mobility in postural control: evidence from postural compensation for respiration

This study evaluated the extent to which movement of the lower limbs and pelvis may compensate for the disturbance to posture that results from respiratory movement of the thorax and abdomen. Motion of the neck, pelvis, leg and centre of pressure (COP) were recorded with high resolution in conjunction with electromyographic activity (EMG) of flexor and extensor muscles of the trunk and hip. Respiration was measured from ribcage motion. Subjects breathed quietly, and with increased volume due to hypercapnoca (as a result of breathing with increased dead-space) and a voluntary increase in respiration. Additional recordings were made during apnoea. The relationship between respiration and other parameters was measured from the correlation between data in the frequency domain (i.e. coherence) and from time-locked averages triggered from respiration. In quiet standing, small angular displacements (similar to0.5degrees) of the trunk and leg were identified in raw data. Correspondingly, there were peaks in the power spectra of the angular movements and EMG. While body movement and EMG were coherent with respiration (>0.5), the coherence between respiration and COP displacement was low (

Vocalizations of primary forest frog species in the Central Amazon.

The calls of 18 species of Amazonian forest frogs were recorded in 3 localities: the Tapajos National Park near Itaituba, the Reserva Ducke near Manaus, and the INPA-WWF reserves near Manaus. Structural and time parameters and sonographs of these calls including previously undescribed vocalization by 10 species are presented. Unlike open habitat species, several forest frong species characteriscally demonstrated one on more of the following temporal parameters: very low call rates, sporadic intervals, infrequent nights of calling and synchronized chorusing. It is hypothesized that predation has influenced the evolution of vocal behaviour in Amazonian forest frogs.

Time-scale and other invariants of integrative mechanical behavior in living cells.

In dealing with systems as complex as the cytoskeleton, we need organizing principles or, short of that, an empirical framework into which these systems fit. We report here unexpected invariants of cytoskeletal behavior that comprise such an empirical framework. We measured elastic and frictional moduli of a variety of cell types over a wide range of time scales and using a variety of biological interventions. In all instances elastic stresses dominated at frequencies below 300 Hz, increased only weakly with frequency, and followed a power law; no characteristic time scale was evident. Frictional stresses paralleled the elastic behavior at frequencies below 10 Hz but approached a Newtonian viscous behavior at higher frequencies. Surprisingly, all data could be collapsed onto master curves, the existence of which implies that elastic and frictional stresses share a common underlying mechanism. Taken together, these findings define an unanticipated integrative framework for studying protein interactions within the complex microenvironment of the cell body, and appear to set limits on what can be predicted about integrated mechanical behavior of the matrix based solely on cytoskeletal constituents considered in isolation. Moreover, these observations are consistent with the hypothesis that the cytoskeleton of the living cell behaves as a soft glassy material, wherein cytoskeletal proteins modulate cell mechanical properties mainly by changing an effective temperature of the cytoskeletal matrix. If so, then the effective temperature becomes an easily quantified determinant of the ability of the cytoskeleton to deform, flow, and reorganize.

Mechanical properties of cultured human airway smooth muscle cells from 0.05 to 0.4 Hz.

We investigated the rheological properties of living human airway smooth muscle cells in culture and monitored the changes in rheological properties induced by exogenous stimuli. We oscillated small magnetic microbeads bound specifically to integrin receptors and computed the storage modulus (G') and loss modulus (G") from the applied torque and the resulting rotational motion of the beads as determined from their remanent magnetic field. Under baseline conditions, G' increased weakly with frequency, whereas G" was independent of the frequency. The cell was predominantly elastic, with the ratio of G" to G' (defined as eta) being ~0.35 at all frequencies. G' and G" increased together after contractile activation and decreased together after deactivation, whereas eta remained unaltered in each case. Thus elastic and dissipative stresses were coupled during changes in contractile activation. G' and G" decreased with disruption of the actin fibers by cytochalasin D, but eta increased. These results imply that the mechanisms for frictional energy loss and elastic energy storage in the living cell are coupled and reside within the cytoskeleton.

Scaling the microrheology of living cells

We report a scaling law that governs both the elastic and frictional properties of a wide variety of living cell types, over a wide range of time scales and under a variety of biological interventions. This scaling identifies these cells as soft glassy materials existing close to a glass transition, and implies that cytoskeletal proteins may regulate cell mechanical properties mainly by modulating the effective noise temperature of the matrix. The practical implications are that the effective noise temperature is an easily quantified measure of the ability of the cytoskeleton to deform, flow, and reorganize.

An analytical approach to sorting in periodic and random potentials

There has been a recent revolution in the ability to manipulate micrometer-sized objects on surfaces patterned by traps or obstacles of controllable configurations and shapes. One application of this technology is to separate particles driven across such a surface by an external force according to some particle characteristic such as size or index of refraction. The surface features cause the trajectories of particles driven across the surface to deviate from the direction of the force by an amount that depends on the particular characteristic, thus leading to sorting. While models of this behavior have provided a good understanding of these observations, the solutions have so far been primarily numerical. In this paper we provide analytic predictions for the dependence of the angle between the direction of motion and the external force on a number of model parameters for periodic as well as random surfaces. We test these predictions against exact numerical simulations.

Naître et grandir au sein de la triade : le développement de l'alliance familiale

INTRODUCTION : L'alliance familiale : une jonction entre les approches développementale, familiale et systémique / Nicolas Pavez, France Frascarolo-Moutinot et Hervé Tissot - LA TRIADE PARENTS-BEBE : THEORIE ET EVALUATION DES INTERACTIONS : Le modèle de l'alliance familiale et le Jeu Trilogique de Lausanne (LTP) / Nicolas Favez - Observation des interactions triadiques en périnatalité : le Jeu du Change / Jérôme Rime et Werner Stadlmayr - Observation des interactions dans les familles avec plusieurs enfants : le Jeu du Pique-Nique / France Frascarolo-Moutinot et Nicolas Favez - L'observation du coparentage dans les familles biparentales : influence du contexte et de l'âge de l'enfant / Regina Kuersten-Hogan et James P. McHale - LE DEVELOPPEMENT NORMATIF DE LA GROSSESSE A L'ECOLE : La capacité triangulaire du bébé : une illustration à l'aide de deux cas contrastés / Elisabeth Fivaz-Depeursinge et Nicolas Favez - L'alliance coparentale prénatale comme prédicteur des perceptions du coparentage au post-partum / Sarah J. Schappe-Sullivan, Claire M. Kamp Dush et Daniel J. Bower - L'évolution de l'alliance familiale et son impact sur l'enfant à l'âge de 5 ans : une étude longitudinale en Suisse / Nicolas Favez, France Frascarolo-Moutinot et Chloé Lavanchy Scaiola - L'évolution de l'alliance familiale et son impact sur l'enfant à l'âge de 4 ans : une étude longitudinale en Italie / Alessandra Simonelli, Mara Bighin et Francesca De Palo - LA THÉRAPIE AVEC LES TRIADES : Alliance familiale dans les troubles fonctionnels et du comportement du nourrisson : évaluation avant et après une intervention thérapeutique. Une étude exploratoire / Marie-Joëlle Hervé... et al. - Le Jeu Trilogique de Lausanne (LTP) en clinique : application dans le contexte d'interventions de soutien à la relation parents-enfants / Silvia Mazzoni et Anna Lubrano Lavadera - Les comportements relationnels de l'enfant comme porte d'entrée pour intervenir sur le système familial / Chloé Lavanchy Scaiola et Kaija Puura - Le Reflective Family Play : un traitement de la famille entière centré sur l'attachement et le système familial / Diane Philipp et Christie Hayos - APPLICATIONS SPECIFIQUES : Le coparentage comme construit universel caractérisant diverses formes familiales : avancées et perspectives / James McHale et Rahael Kurrien - Les alliances coparentales dans les familles lesboparentales / Salvatore D'Amore, Alessandra Simonelli et Marina Miscioscia - Alliance familiale entre père, mère et leur bébé conçu par fécondation in vitro / Joëlle Darwiche... et al. - CONCLUSION : Le bébé dans la triade précoce / Nicolas Pavez, France Frascarolo-Moutinot et Hervé Tissot

Reinforcement versus Fluidization in Cytoskeletal Mechanoresponsiveness

Every adherent eukaryotic cell exerts appreciable traction forces upon its substrate. Moreover, every resident cell within the heart, great vessels, bladder, gut or lung routinely experiences large periodic stretches. As an acute response to such stretches the cytoskeleton can stiffen, increase traction forces and reinforce, as reported by some, or can soften and fluidize, as reported more recently by our laboratory, but in any given circumstance it remains unknown which response might prevail or why. Using a novel nanotechnology, we show here that in loading conditions expected in most physiological circumstances the localized reinforcement response fails to scale up to the level of homogeneous cell stretch; fluidization trumps reinforcement. Whereas the reinforcement response is known to be mediated by upstream mechanosensing and downstream signaling, results presented here show the fluidization response to be altogether novel: it is a direct physical effect of mechanical force acting upon a structural lattice that is soft and fragile. Cytoskeletal softness and fragility, we argue, is consistent with early evolutionary adaptations of the eukaryotic cell to material properties of a soft inert microenvironment.

Evaluation of the surface erosion from different timber yarding methods in Honduras

Surface runoff and sediment production from different timber yarding practices, some using Best Management Practices (BMPs) recommended for Honduras, were monitored in experimental plots during the rainy seasons of two consecutive years in pine forest highlands of central Honduras. Different timber yarding systems were applied to pseudo-replicated plots during the rainy seasons of 1999 and 2000. In 1999, two treatments were studied: tractor yarding and skyline cable (a recommended BMP). In 2000, four treatments were evaluated: tractor skidding, skyline cable, animal skidding (another recommended BMP), and undisturbed forest (reference). During the rainy seasons of these years, surface runoff volumes and sediment yield were measured at five 1.5m x 10m erosion plots in each treated area. The results showed significant differences between traditional tractor yarding and the recommended skyline cable and animal skidding methods. Tractor yarding produced six to ten times more erosion during the rainy seasons than cable and animal yarding. The improved soil retention of cable and animal yarding was especially important during September when the highest rainfall occurred in this climate.

Weekly Aurora, 21 February 1815 (vol. 5, no. 49) - Newspaper

Volumes of interest were published between 1812 and 1815 with articles about the War of 1812. Issue for Feb. 21, 1815, beginning on page 2 and continuing to take all of page 3 and some of page 4 is the full text headed: "TREATY OF PEACE" which is prefaced with an address by James Madison. Also in this issue is an article: "Victory At Orleans" and another article headed: "The War--From New Orleans".

Réponses des neurones du noyau sensoriel principal du trijumeau à la stimulation de leurs afférences primaires

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal.