Radiation fields from polygonal sources

The calculation of the radiation field D(x, y, z) produced by a uniform polygonal source is of considerable practical importance. Fock showed that there are advantages in replacing the traditional surface integral by a contour integral, using Stokes' theorem. This innovation, however, has not yet penetrated very deeply. It seemed worthwhile, therefore, to systematize the procedure and to show how easily results can be obtained by the Fock method. An incidental conclusion of the paper is that the radiation field from a polygonal source often differs by less than one per cent from the field produced by a circular disk of the same area. Thus the simple disk formula can often be substituted for the more complicated polygonal formula.     

Sex differences in lower extremity kinematics and patellofemoral kinetics during running

The incidence of patellofemoral pain (PFP) is 2 times greater in females compared with males of similar activity levels; however, the exact reason for this discrepancy remains unclear. Abnormal mechanics of the hip and knee in the sagittal, frontal, and transverse planes have been associated with an increased risk of PFP. The purpose of this study was to compare the mechanics of the lower extremity in males and females during running in order to better understand the reason(s) behind the sex discrepancy in PFP. Three-dimensional kinematic and kinetic data were collected as male and female participants completed overground running trials at a speed of 4.0 m · s^?1 (±5%). Patellofemoral joint stress (PFJS) was estimated using a sagittal plane knee model. The kinematics of the hip and knee in the frontal and transverse planes were also analysed. Male participants demonstrated significantly greater sagittal plane peak PFJS in comparison with the female participants (P < .001, ES = 1.9). However, the female participants demonstrated 3.5° greater peak hip adduction and 3.4° greater peak hip internal rotation (IR). As a result, it appears that the sex discrepancy in PFP is more likely to be related to differences in the kinematics of the hip in the frontal and transverse planes than differences in sagittal plane PFJS.     

Reinforcement schedules,effort vs. Ability attributions,and persistence

Two treatment studies of special education students markedly helpless with regard to arithmetic are reported. The first experiment compared an attribution retraining (Dweck, 1975) treatment to a control treatment matched to it in schedule of successes and failures. Both the attribution retraining and control treatments proved effective in alleviating helplessness, but they were not differentially effective. The second experiment compared the effects of three success-failure schedules (100% success, 76.9% success, and 46.2% success) on attributions and persistence. Only the 76.9% success schedule increased attributions of failures to lack of effort and improved behavioral persistence in the face of failure. The results were interpreted as supporting one aspect of Weiner's (1979) theory, which implies that an infrequently experienced event, i.e., failure, will be attributed to an unstable cause, i.e., lack of effort.     

Developing a Strong Program of Construct Validation: A Test Anxiety Example

What would a strong program of construct validation look like for the concept of test anxiety? What are the components of strong validation programs? In particular, how does structural equation modeling fit into such a program?