1,720,972 research outputs found
Perception action coupling in postural stability for elderly
No full textPerception action coupling in postural stability for elderl
A common perceptual parameter for stair climbing for children, young and old adults.
No full textIn this paper we examine whether a common perceptual parameter is available for guiding old adults, young adults and children in climbing the highest stair mountable in a bipedal fashion. Previous works have shown that the ratio between the height of the stair and the hip height was the body-scaled invariance adopted as information for selecting the highest stair by young adults [Journal of Experimental Psychology: Human Perception and Performance 10 (1984) 683-703] but not by older adults [Journal of Experimental Psychology: Human Perception and Performance 3 (1992) 691-697]. Indeed, for older adults additional bio-mechanical parameters needed to be added to the model due to their decrease in leg strength and flexibility.Up to now, no perceptual invariant has been identified yet for determining the relevant information used for guiding the stair climbing action for normal healthy people. We propose a new parameter as the angle defined by the ratio between the height of the stair and the distance taken from the feet to the top edge of the stair before the initiation of the movement. We show that this angle is the same for children, young adults and older adults despite the different kinematics of the motion, the anthropometrics and the skill ability exhibit by the participants. In summary we show that even when the climbability judgments, based on the simple ratio leg length-stair height, are influenced by differences in age, participants use a common perceptual variable when they are coordinating their stair climbing action
Perception-action coupling: changing “affordances” in stair climbing for young and older adults
No full textPerception-action coupling: changing “affordances” in stair climbing for young and older adult
Analysis of Kinematically Redundant Reaching Movements using the Equilibrium-Point Hypothesis
No full textSix subjects performed a planar reaching arm movement to a target while unpredictable perturbations were applied to the endpoint; the perturbations consisted of pulling springs having different stiffness. Two conditions were applied; in the first, subjects had to reach for the target despite the perturbation, in the second condition, the subjects were asked to not correct the motion as a perturbation was applied. We analyzed the kinematics profiles of the three arm segments and, by means of inverse dynamics, calculated the joint torques. The framework of the equilibrium-point (EP) hypothesis, the λ model, allowed the reconstruction of the control variables, the "equilibrium trajectories", in the "do not correct" condition for the wrist and the elbow joints as well as for the end point final position, while for the other condition, the reconstruction was less reliable. The findings support and extend to a multiple-joint planar movement, the paradigm of the EP hypothesis along with the "do not correct" instruction
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Spectroscopic and theoretical studies of some N,N-diethyl-2-[(4-substituted)phenylsulfinyl] acetamides
No full textPrevious spectroscopic (IR, 13CNMR,UV and UPS), X-ray studies performed in our laboratories on some β-carbonylsulfoxides XC(O)CH2S(O)R (X=Me, Ar, NR2, OR and SR; R= Me, Ar) [1-5], have shown that their gauche conformer is the most stable, but the cis conformer prevails for the α-sulfinylacetophenones, XC(O)CH2S(O)R [X=Ph; R=Me, Et, iPr, and Ph] [6,7] and X= p-Y-Ph (for Y = OME, Me, H, Cl, and Br; R=Et)] [8], except for R= tBu for the former series, and (Y = CN and NO2; R=Et) for the latter one for which the gauche conformer is the most stable one. The stabilization of the gauche conformers has been attributed to the πCO/σ*C-S and, to a minor extent, to the π*CO/σC-S orbital interactions, while the peculiar stabilization of the cis conformers of the α-alkylsulfinylacetophenones relative to the α-alkyl- and α-aryl-sulfinylacetones has been ascribed to the larger relaxation of the benzene ring π electron charge (due to the πPh-πCO conjugation), which originates stronger intramolecular electrostatic and charge transfer interactions between Cδ+=Oδ- and Sδ+=Oδ- dipoles.
In the MeC(O)X series [9,10] there is a progressive decrease of the experimental carbonyl oxygen lone pair (nO) ionization energy going from ester (Ei=10.45eV) to thioester (Ei=9.64eV) to butanone (Ei=9.46eV), to acetophenone (Ei=9.34eV) and to amide (Ei=9.20eV) for X= OEt, SEt, Et, Ph and NEt2, respectively, which in turn is accompanied by a corresponding increase of the negative charge on the carbonyl oxygen atom in this direction. Therefore it seems reasonable to expect a larger stabilization of the cis conformer of the α-sulfinyl-amides relative to the same conformation of the α-sulfinylacetophenones, due to stronger Cδ+=Oδ-....Sδ+=Oδ- orbital and electrostatic interactions which should operate in the cis conformation of the sulfinyl-amides.
Aiming to throw more light on the nature of the different electronic interactions which may stabilize the cis and gauche conformers of the α-sulfinylamides, this paper reports the IR study of some N,N-diethyl-2-[(4-substituted) phenylsulfinyl] acetamides Et2NC(O)CH2S(O)Ph-Y, bearing in 4- electron-donating, hydrogen and electron-withdrawing substituents i.e. Y= OMe 1,Me 2, H 3,Cl 4, Br 5, NO2 6 (Scheme 1) along with ab initio calculations of 3 and X-ray diffraction analysis of compound 6. These compounds were chosen taking into account that the orbital and Coulombic interactions, which could operate in their cis and gauche conformers, should be affected by changes in the conjugation involving the 4-substituent at the phenylsulfinyl group, and consequently should influence the stabilization of the referred conformers
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