Changes in a postural strategy with inter-paw distance

1994 ◽  
Vol 71 (3) ◽  
pp. 931-940 ◽  
Author(s):  
J. M. Macpherson
Keyword(s):  
Horizontal Plane ◽  
Vertebral Column ◽  
Center Of Mass ◽  
The Other ◽  
Support Surface ◽  
Quiet Stance ◽  
Postural Response ◽  
Isotropic Distribution ◽  
Platform Translation ◽  
The One

1. The purpose of this study was to examine the effect of changing initial stance conditions on the postural response of the cat to horizontal plane translations of the support surface. Cats were trained to stand, unrestrained, on a moveable force platform. The platform was translated linearly in each of 16 directions in the horizontal plane, with a ramp-and-hold displacement. The animal's response was quantified in terms of the forces exerted at the ground. The trajectory of the center of mass (CoM) was computed from the forces. 2. Stance length was varied along the longitudinal (sagittal) axis by adjusting the distance between the forepaw and hindpaw force plates. Translation perturbations of the platform were recorded at stance distances varying from 66 to 110% of the preferred stance distance. 3. Changing stance distance had a significant effect on the amplitude and direction of the active forces exerted by the cat both during quiet stance and during the response to platform translation. At long stance distances, each limb exerted a force outward, along the diagonals during quiet stance. The response to translation was characterized by an invariance in the direction of force exerted against the ground, a strategy that was described previously. At short stance distances, quiet stance forces were more laterally directed. The force constraint strategy was usually not observed for the response to translation. Nevertheless, the cats were equally effective at all stance distances in restoring the position of the center of mass after translation of the support surface. 4. There was no discrete boundary between the presence and absence of the force constraint, suggesting that the strategy for exerting forces against the support surface is characterized by a continuum of response, from a bimodal, or anisotropic distribution of force vectors on the one extreme, to a uniform, or isotropic distribution on the other. Arguments are developed to suggest that the force constraint strategy may be useful in stabilizing the vertebral column during the response to platform translation, to allow linear translation of the CoM rather than bending of the trunk.

scholarly journals 4. On a Thermomagnetic Thermoscope

1880 ◽  
Vol 10 ◽  
pp. 538-539
Author(s):  
W. Thomson
Keyword(s):  
Magnetic Moment ◽  
Horizontal Plane ◽  
Hardened Steel ◽  
The Other ◽  
Silk Fibre ◽  
Steel Wires ◽  
The One

This thermoscope is founded on the change produced in the magnetic moment of a steel magnet by change of temperature. Several different forms suggest themselves: the one which seems best adapted to give good results is to be made as follows:—(1.) Prepare an approximately astatic system of two thin, hardened steel wires, r b, r′ b′, each 1 cm. long, one of them, r, b, hung by a single silk fibre, and the other hung bifilarly from it, by fibres about 3 cms. long, so attached that the projections of the two, on a horizontal plane, shall be inclined at an angle of about ·01 of a radian (or ·57°) to one another.

Effect of galvanic vestibular stimulation on human postural responses during support surface translations

1995 ◽  
Vol 73 (2) ◽  
pp. 896-901 ◽  
Author(s):  
J. T. Inglis ◽  
C. L. Shupert ◽  
F. Hlavacka ◽  
F. B. Horak
Keyword(s):  
Vestibular System ◽  
Equilibrium Position ◽  
Critical Role ◽  
Vestibular Stimulation ◽  
Galvanic Vestibular Stimulation ◽  
Support Surface ◽  
Quiet Stance ◽  
Galvanic Current ◽  
Postural Responses ◽  
Platform Translation

1. We investigated the role of the vestibular system in postural control by combining galvanic vestibular stimulation (0.2-0.5 mA) with platform translations in standing subjects. Vestibular stimulation delivered 500 ms before and continuously during the platform translation produced little change in the earliest center of pressure (COP) and center of mass (COM) movements in response to platform translations, but resulted in large changes during the execution of the postural movement and in the final equilibrium position. 2. Vestibular stimulation produced anterior or posterior shifts in the position of COP and COM, depending on the polarity of the galvanic current. These shifts were larger during platform translations than during quiet stance. The peak of these shifts in COP and COM occurred at 1.5-2.5 s after the onset of platform translation, and increased in magnitude with increasing platform velocity. The final equilibrium positions of COP and COM were also shifted, but these shifts were smaller and not dependent on platform velocity. 3. These results imply that a tonic step of galvanic current to the vestibular system can change the final equilibrium position for an automatic postural response. Furthermore, these results indicate that the vestibular system may play a larger role in interpreting sensory reafference during postural movements, and especially during fast postural movements, than in controlling quiet stance. Finally, these results indicate that the vestibular system does not play a critical role in triggering the earliest postural responses, but it may be critical in establishing an internal reference for verticality.

scholarly journals Ship’s Horizontal Plane Determination by Means of Three Laser Range Sensors in Pilot Navigation and Docking System / WYZNACZENIE POŁOŻENIA UMOWNEJ WODNICY STATKU ZA POMOCĄ TRZECH DALMIERZY LASEROWYCH W PILOTOWYM SYSTEMIE NAWIGACYJNO-DOKUJĄCYM

2012 ◽  
Vol 24 (1) ◽  
pp. 161-169 ◽  
Author(s):  
Paweł Zalewski
Keyword(s):  
Risk Taking ◽  
Reference System ◽  
Horizontal Plane ◽  
Support Systems ◽  
The Other ◽  
Laser Range ◽  
Laser Head ◽  
Navigation Support ◽  
The One ◽  
Prime Source

Abstract Modern ship’s navigation support systems relay mainly on GNSS technology, as prime source of position. The advantages of such solution are obvious and undeniable. On the other hand in critical situations the dependency of the one system presents a great deal of risk. Taking above into consideration the idea of building GNSS independent Pilot Navigation and Docking System (PNDS) was put into practice. PNDS utilizes the range measurements between laser head and ship’s side to determine the ship’s horizontal plane presented on the screen. The study comprises the case in which three networked rangefinders were deployed on the berth side in a line. Such location of sensors causes uncertainty in determining of ship’s outline contour and speed in relation to assigned coordinate reference system. The final algorithm presented in the article, taking into account all underdetermined conditions, has been tested in PNDS system constructed in Maritime University in Szczecin.

Bilateral Vestibular Loss in Cats Leads to Active Destabilization of Balance During Pitch and Roll Rotations of the Support Surface

2007 ◽  
Vol 97 (6) ◽  
pp. 4357-4367 ◽  
Author(s):  
Jane M. Macpherson ◽  
Dirk G. Everaert ◽  
Paul J. Stapley ◽  
Lena H. Ting
Keyword(s):  
Center Of Mass ◽  
The Body ◽  
Support Surface ◽  
Postural Response ◽  
Vestibular Loss ◽  
Bilateral Vestibular Loss ◽  
Automatic Postural Response ◽  
Vestibular Information ◽  
Body Center ◽  
Proprioceptive Inputs

Although the balance difficulties accompanying vestibular loss are well known, the underlying cause remains unclear. We examined the role of vestibular inputs in the automatic postural response (APR) to pitch and roll rotations of the support surface in freely standing cats before and in the first week after bilateral labyrinthectomy. Support surface rotations accelerate the body center of mass toward the downhill side. The normal APR consists of inhibition in the extensors of the uphill limbs and excitation in the downhill limbs to decelerate the body and maintain the alignment of the limbs with respect to earth-vertical. After vestibular lesion, cats were unstable during rotation perturbations and actively pushed themselves downhill rather than uphill, using a postural response that was opposite to that seen in the control trials. The extensors of the uphill rather than downhill limbs were activated, whereas those of the downhill limbs were inhibited rather than being excited. We propose that vestibular inputs provide an important reference to earth-vertical, which is critical to computing the appropriate postural response during active orientation to the vertical. In the absence of this vestibular information, subjects orient to the support surface using proprioceptive inputs, which drives the body downhill resulting in instability and falling. This is consistent with current models of sensory integration for computation of body posture and orientation.

Bilateral labyrinthectomy in the cat: effects on the postural response to translation

1995 ◽  
Vol 73 (3) ◽  
pp. 1181-1191 ◽  
Author(s):  
J. T. Inglis ◽  
J. M. Macpherson
Keyword(s):  
Visual Information ◽  
Center Of Mass ◽  
Afferent Input ◽  
Support Surface ◽  
Postural Response ◽  
Automatic Postural Response ◽  
Somatosensory Information ◽  
Postural Responses ◽  
Before And After ◽  
Evoked Activity

1. This study examined the role of vestibular afferent information on the postural responses of four cats, evoked by movements of the support surface during stance. Animals were exposed to linear translations of the supporting surface in eight evenly spaced directions in the horizontal plane, before and after bilateral labyrinthectomy. Postural responses were quantified in terms of the ground reaction forces under each paw and the evoked activity in selected muscles. 2. The cats were able to stand on the platform within 1-3 days after labyrinthectomy and were able to maintain balance during all perturbations of stance, even when they stood in total darkness, completely deprived of visual information. After lesion, postural responses were characterized by normal latency and normal spatial and temporal patterning of electromyographic (EMG) response. The pattern of force response showed the force constraint strategy that characterizes postural responses in the intact animal. 3. The only deficit in the postural response after lesion was a hypermetria, or active over-response that caused the animals to overbalance somewhat but did not impair their ability to remain upright. Analysis of the trajectory of the animal's center of mass during the trials indicated that the hypermetria was due to an abnormally large, active response on the part of the animal and could not be attributed to changes in the passive stiffness of the musculoskeletal system. The hypermetria was transient, and response amplitude returned to control levels after the rapid compensation phase of 10-15 days. 4. It is concluded that vestibular information is not essential for triggering the rapid, automatic postural response to translations of the support surface, nor is it necessary for the selection or shaping of the evoked response. Instead, somatosensory information appears to predominate in these postural adjustments. However, vestibular afferent input does influence the scaling of the postural response.

scholarly journals On the classification of the reptilia

1916 ◽  
Vol 89 (615) ◽  
pp. 261-276 ◽  
Keyword(s):  
Vertebral Column ◽  
The Other ◽  
Temporal Region ◽  
Starting Point ◽  
Mode Of Life ◽  
Modern Classification ◽  
The One ◽  
Relationship Of ◽  
Exact Relationship

It is gradually becoming recognised that the class Reptilia is not a monophyletic group of diverging forms sprung from a common stem, like the class Aves or the class Mammalia; but is an assemblage containing, on the one hand, the ancestors of the Mammalia, and, on the other hand, the ancestors of the Birds, together with the early Amphibian-like Amniotes, which became adapted to a terrestrial mode of life. In fact, the Reptilia represent not a class but a grade of structure. This group includes a main stem leading from the Stegocephalian type to a central point of divergence of two main branches, one giving rise to the Birds, the other to the Mammals (as shown in the diagram, fig. 1). In addition, there are, of course, many abortive side twigs. Some day, no doubt, when the exact relationship of the various living and extinct reptiles has been more accurately determined, it will be necessary to split up the artificial group Reptilia, assigning some to the Mammalia and some to the Aves; but for the present we may be content with keeping the class Eeptilia, always remembering that it is a grade of ill-defined limits. The modern views of the phylogenetic relationships of the various orders of Eeptilia may be said to have arisen chiefly from the work of Cope and Baur, following on the conclusions of Huxley and other earlier authors. To the ingenuity of Cope we owe the valuable suggestion that the starting-point of the divergence between the Amphibia and the Eeptilia was determined by the structure of the vertebral column—the vertebral body being mainly derived from the hypocentrum in the former and from the pleurocentrum in the Amniota. Being thus provided with a means of distinguishing the early reptiles from their Amphibian relatives, the next step is to seek for characters enabling us to trace out the diverging lines among the Eeptilia themselves. Here again we are indebted to Cope (13), but more especially to Baur (1, 2) for pointing out the importance of the roofing of the skull in classification. Whereas the earliest and most primitive reptiles have, like their Amphibian ancestors, a roofing complete over the temporal region, this becomes pierced in others by one or two foramina. Thus are left one or two longitudinal temporal arches. The formation of the foramina or fossæ is generally accompanied by a reduction in the number of bones covering the hinder region of the skull. It is not my intention to enter into a detailed account of these points in this paper; they have been discussed by many authors, and are well understood. It will be sufficient for our present purpose to point out how profoundly the modern classification of the Amniota has been affected by their recognition.

scholarly journals Center mass theorem in three dimensional spaces with constant curvature

2020 ◽  
Vol 56 (3) ◽  
pp. 328-334
Author(s):  
Yu. A. Kurochkin ◽  
D. V. Shoukavy ◽  
I. P. Boyarina
Keyword(s):  
Constant Curvature ◽  
Jacobi Equation ◽  
Center Of Mass ◽  
Three Dimensional ◽  
The Other ◽  
Dimensional Sphere ◽  
Internal Interaction ◽  
The One ◽  
Definition Of ◽  
Hamilton Jacobi Equation

In this paper, based on the definition of the center of mass given in [1, 2], its immobility is postulated in spaces with a constant curvature, and the problem of two particles with an internal interaction, described by a potential depending on the distance between points on a three-dimensional sphere, is considered. This approach, justified by the absence of a principle similar to the Galileo principle on the one hand and the property of isotropy of space on the other, allows us to consider the problem in the map system for the center of mass. It automatically ensures dependence only on the relative variables of the considered points. The Hamilton – Jacobi equation of the problem is formulated, its solutions and the equations of trajectories are found. It is shown that the reduced mass of the system depends on the relative distance. Given this circumstance, a modified system metric is written out.

A Unified Decoherence-Based Model of Microparticles in a Solution

2007 ◽  
Vol 555 ◽  
pp. 405-410 ◽  
Author(s):  
J. Jeknić ◽  
M. Dugić ◽  
D. Raković
Keyword(s):  
Center Of Mass ◽  
Conformational Transitions ◽  
The Other ◽  
General Context ◽  
Complex Behavior ◽  
Physico Chemical ◽  
Solution Dynamics ◽  
The One ◽  
Definition Of

The complex behavior of microparticles in a solution calls for different theoretical backgrounds. Here, we follow the line of two, recently developed theories on individuality, on the one hand, and conformational transitions of macromolecules in a solution, on the other. Given as separate theories, the two models may raise certain controversy in respect to their mutual consistency. Needless to say, their mutual consistency is necessary for the validity of the theories both in a general context as well as in search for a unified physico/chemical picture concerning the microparticles in a solution dynamics. We point out the consistency of these theories based on the definition of a molecule through its constituent subsystems (e.g. the center-of-mass and the “conformation” subsystems).

Note on Selection of Coordinate Systems for Geodynamics

1975 ◽  
Vol 26 ◽  
pp. 395-407
Author(s):  
S. Henriksen
Keyword(s):  
Sea Level ◽  
The Other ◽  
Coordinate Systems ◽  
Mean Sea Level ◽  
The Earth ◽  
The One ◽  
Static Systems ◽  
Selection Of

The first question to be answered, in seeking coordinate systems for geodynamics, is: what is geodynamics? The answer is, of course, that geodynamics is that part of geophysics which is concerned with movements of the Earth, as opposed to geostatics which is the physics of the stationary Earth. But as far as we know, there is no stationary Earth – epur sic monere. So geodynamics is actually coextensive with geophysics, and coordinate systems suitable for the one should be suitable for the other. At the present time, there are not many coordinate systems, if any, that can be identified with a static Earth. Certainly the only coordinate of aeronomic (atmospheric) interest is the height, and this is usually either as geodynamic height or as pressure. In oceanology, the most important coordinate is depth, and this, like heights in the atmosphere, is expressed as metric depth from mean sea level, as geodynamic depth, or as pressure. Only for the earth do we find “static” systems in use, ana even here there is real question as to whether the systems are dynamic or static. So it would seem that our answer to the question, of what kind, of coordinate systems are we seeking, must be that we are looking for the same systems as are used in geophysics, and these systems are dynamic in nature already – that is, their definition involvestime.

Stories and the Self

2020 ◽  
Vol 32 (2) ◽  
pp. 47-58 ◽  
Author(s):  
Stefan Krause ◽  
Markus Appel
Keyword(s):  
Meta Analysis ◽  
The Self ◽  
The Other ◽  
Lower Degree ◽  
Contrast Effects ◽  
Self Perception ◽  
Self Perceptions ◽  
Other Hand ◽  
The One ◽  
Implicit And Explicit

Abstract. Two experiments examined the influence of stories on recipients’ self-perceptions. Extending prior theory and research, our focus was on assimilation effects (i.e., changes in self-perception in line with a protagonist’s traits) as well as on contrast effects (i.e., changes in self-perception in contrast to a protagonist’s traits). In Experiment 1 ( N = 113), implicit and explicit conscientiousness were assessed after participants read a story about either a diligent or a negligent student. Moderation analyses showed that highly transported participants and participants with lower counterarguing scores assimilate the depicted traits of a story protagonist, as indicated by explicit, self-reported conscientiousness ratings. Participants, who were more critical toward a story (i.e., higher counterarguing) and with a lower degree of transportation, showed contrast effects. In Experiment 2 ( N = 103), we manipulated transportation and counterarguing, but we could not identify an effect on participants’ self-ascribed level of conscientiousness. A mini meta-analysis across both experiments revealed significant positive overall associations between transportation and counterarguing on the one hand and story-consistent self-reported conscientiousness on the other hand.

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