Biomedical subjects

François Poulin

Publications and source records attributed to François Poulin.

6 recordsLinked to original sources

PubMed2004

Is there a dark side of positive illusions? Overestimation of social competence and subsequent adjustment in aggressive and nonaggressive children.

This study examined (a) the links between children's overly positive perceptions about the relations with the peer group and with their best friend to subsequent behavioral, emotional, and social adjustment, and (b) whether these links are moderated by children's aggression. Using a short-term longitudinal design, the study was based on a sample of 819 4th- to 6th-graders (427 girls) from low to average SES families. Results showed that positive illusions about their social relations with classmates and with friends were related to an increase in children's peer-rated social preference and fostered the stability of children's dyadic friendships, regardless of children's level of aggression. In addition, overestimation of social competence with the peer group and overestimation of friendship quality were both related to a decrease in children's depressive feelings. Extreme overestimation as well as extreme underestimation of social competence with the peer group was also related to an increase in children's aggression. This latter result, however, was only true for children who were highly aggressive to begin with. The theoretical and practical implications of these results are discussed.

Adolescent↗

PubMed2004

Computed tomography-based navigation for hip, knee, and spine surgery.

A review of CT-based orthopaedic navigation is presented with a specific emphasis on arthroplasty for the hip and the knee. Fundamental issues about the laboratory and clinical validation of the applications are addressed. The ability to compute the position and orientation of an acetabular implant using a postoperative CT scan was investigated. Angle deviations relative to known positions were computed with an error of less than 1 degree. Then, the system accuracy for three-dimensional reconstruction and registration of two cadaveric pelvis specimens was measured with more than 350 registrations. We observed a maximal inclination error of 5 degrees in 99% of cases and a maximal anteversion error of 5 degrees in 97% of cases. The accuracy of the three-dimensional reconstruction and registration for knee arthroplasty also was measured and computed with an angular accuracy of 0.5 degrees in the AP plane and accuracy of 3 degrees in the lateral plane. A clinical study then was done in 109 cases where 96% of implants were installed with a hip-knee-ankle angle of 180 +/- 3 degrees . Computed tomography-based navigation for orthopaedic surgery provides greater accuracy and reproducibility than conventional surgery. As noted by learning curves, software improvements are needed to bring it into daily clinical routine.

Arthroplasty, Replacement↗

PubMed2002

Interference during the use of an electromagnetic tracking system under OR conditions.

Many computer-assisted surgery applications use electromagnetic tracking devices and several sources of interference may reduce the accuracy of this type of system in clinical situations. This study aims to quantify interference sources in an operating room (OR) and determine if their impact on the tracking system is excessive for applications requiring millimetric accuracy. Electromagnetic noise levels were measured in a controlled environment and compared with measurements in an OR. Errors generated by this noise remained below the 0.15mm RMS level. OR equipment was also brought in proximity to the electromagnetic receivers and the errors generated by the ensuing interference were measured. Ferromagnetic and electrical devices can produce large interference (translation errors up to 8.4mm RMS and rotation up to 166 degrees ). However, these devices can be identified and placed at sufficient distances to decrease the magnitude of their interference. In conclusion, in the absence of significant ferromagnetic or electromagnetic distortion caused by equipment often present in an OR, this electromagnetic tracking system provides valid relative measurements with millimetric accuracy to computer-assisted surgical applications. This distortion can be reduced by maximizing the distances to the interfering OR equipment and integrating noise-reducing algorithms in associated software.

Artifacts↗

PubMed2002

Assessing aggressive and depressed children's social relations with classmates and friends: a matter of perspective.

This study examined aggressive, depressed, and aggressive-depressed children's peer relations from the children's own and from their peers' perspective. Participants were 819 fourth through sixth graders (50.2% girls) who were assessed twice during the same school year. Measures included children's aggression and depression, self-rated and peer-rated social acceptance, number of reciprocal friends, and self-rated and friend-rated friendship quality. Analyses revealed different patterns, depending on the perspective considered. Depression but not aggression was significantly related to difficulties with the peer group and with dyadic friends from the children's own perspective, whereas the opposite pattern was found according to the peers' view. The co-occurrence of aggression and depression entailed significant difficulties with peers regardless of perspective. The implications of these results for the links between children's aggression and depression and their interpersonal relationships are discussed.

Adolescent↗

PubMedDate not supplied

Group identification in early adolescence: its relation with peer adjustment and its moderator effect on peer influence.

This study was conducted to test whether group identification (importance of the group to the individual) covaried with individual-group similarity on problem behavior; and whether group identification moderated peer group influence on the individual's development of delinquent behavior across a 1-year period. The level of reciprocated nominations within the individual's self-nominated group was controlled for in all analyses. Participants were 190 sixth and seventh graders (during the first year of the study) from the north of Italy. Level of reciprocated nominations within the group, but not identification, was found to covary with individual-group behavioral similarity (group behavior interacted with reciprocity of group nominations in predicting individual behavior). Group identification, but not reciprocated nominations, was found to moderate peer group influence on the individual's change in delinquent behavior, across 1 year. The individual's peer status within the classroom, level of reciprocated nominations, and gender all were related to the individual's level of group identification. Results are discussed in terms of understanding peer group influence on the individual.

Adolescent↗

PubMedDate not supplied

Peer relations across contexts: individual-network homophily and network inclusion in and after school.

Peer relations across 2 contexts (in school and after school) were examined for 577 participants, approximately 12 years old, from 3 middle schools in Milan, Italy. The primary research questions were: Do peer networks from different contexts uniquely contribute to explaining variance in individual behavior? Do measures of peer preference and peer network inclusion across contexts uniquely contribute to explaining individual depressive symptoms? Structural equation models showed that both the in-school and the after-school peer networks uniquely contributed to explaining variance in 2 types of individual problem behavior (in-school problem behavior, after-school delinquency), and that similarity with the 2 peer networks varied according to behaviors specific to each context and across gender. Finally, both in-school and after-school peer network inclusion contributed to explaining variance in depressive symptoms, after controlling for classroom peer preference.

Adolescent↗