The effect of mountain bike wheel size on cross-country performance

ABSTRACT

The purpose of this study was to determine the influence of different wheel size diameters on indicators of cross-country mountain bike time trial performance. Nine competitive male mountain bikers (age 34.7 ± 10.7 years; stature 177.7 ± 5.6 cm; body mass 73.2 ± 8.6 kg) performed 1 lap of a 3.48 km mountain bike (MTB) course as fast as possible on 26″, 27.5″ and 29″ wheeled MTB. Time (s), mean power (W), cadence (revs · min^?1) and velocity (km · h^?1) were recorded for the whole lap and during ascent and descent sections. One-way repeated measure ANOVA was used to determine significant differences. Results revealed no significant main effects for any variables by wheel size during all trials, with the exception of cadence during the descent (F_{(2, 16)} = 8.96; P = .002; P² = .53). Post hoc comparisons revealed differences lay between the 26″ and 29″ wheels (P = .02). The findings indicate that wheel size does not significantly influence performance during cross-country when ridden by trained mountain bikers, and that wheel choice is likely due to personal choice or sponsorship commitments.     

An analytical solution for the multidimensional degradation of a packed bed thermocline

A multidimensional, time-dependent model of the thermocline degradation in a packed bed thermal storage tank is presented. The formulation includes the effects of finite tank length, multidimensional thermal conduction, heat transfer between the fluid and solid portions of the bed, and heat losses across all tank surfaces. The technique used to solve the coupled pair of parabolic partial differential equations describing the degradation of the thermocline is based on a vectorized separation of variables approach. Assuming cylindrical geometry, the analysis leads to separate eigenvalue problems for the radial, angular, and axial spatial dependencies of the fluid and solid temperatures in the bed. The eigenvalues are readily calculated and the corresponding eigenfunctions are shown to form a complete set of spatial basis functions for the solution space. The method and results are illustrated by several examples.     

Effect of response mode and subject characteristics on learning in programed instruction

60 Ss took a program in one of three ways: writing the answer, “thinking” the answer without writing it, or reading a program with the answers filled in. Results indicated no significant differences among the groups on two measures of amount learned. Low positive correlations were obtained between amount learned and IQ and reading comprehension of the Ss. Percent error on test frames within the program was negatively correlated with adjusted gain scores (r = −0.71). Results were also related to possible pragmatic applications.     

Detecting subtle yet fast skeletal muscle contractions with ultrasoft and durable graphene-based cellular materials

Human bodily movements are primarily controlled by the contractions of skeletal muscles. Unlike joint or skeletal movements that are generally performed in the large displacement range, the contractions of the skeletal muscles that underpin these movements are subtle in intensity yet high in frequency. This subtlety of movement makes it a formidable challenge to develop wearable and durable soft materials to electrically monitor such motions with high fidelity for the purpose of, for example, muscle/neuromuscular disease diagnosis. Here we report that an intrinsically fragile ultralow-density graphene-based cellular monolith sandwiched between silicone rubbers can exhibit a highly effective stress and strain transfer mechanism at its interface with the rubber, with a remarkable improvement in stretchability (>100%). In particular, this hybrid also exhibits a highly sensitive, broadband-frequency electrical response (up to 180 Hz) for a wide range of strains. By correlating the mechanical signal of muscle movements obtained from this hybrid material with electromyography, we demonstrate that the strain sensor based on this hybrid material may provide a new, soft and wearable mechanomyography approach for real-time monitoring of complex neuromuscular–skeletal interactions in a broad range of healthcare and human–machine interface applications. This work also provides a new architecture-enabled functional soft material platform for wearable electronics.     

Using and updating local norms

The most useful kind of norms are local norms collected by a test interpreter on a population with which s/he is familiar. We present a rationale for the use of local norms and a procedure, illustrated with an example, for updating a norm group's test score mean and variance. It was concluded that test interpreters should build local norms to be used in conjunction with norms based on a national sample, since local norms can be more recent, relevant, and representative for local groups.     

A replication of a survey of school psychologists: Congruence between training,practice, preferred role,and competence

The present study is a replication of an earlier effort by Meacham and Peckham (1978) that surveyed practicing school psychologists to obtain their perceptions regarding the congruency between the role functions of assessment, interpretation, remediation, consultation, change agent, and research and training, present job, preferred job, and competence. Overall, results indicate a greater congruency between the training and practice of school psychologists. Other findings are discussed in terms of their implications for the training and practice of school psychology.     

Concurrent Validity of the standard progressive matrices for Hispanic and nonHispanic and seventh-grade students

Correlations between the Standard Progressive Matrices test (SPM) and the California Achievement Test, Reading, Language, and Mathematics Tests were examined for 99 Hispanic and 93 nonHispanic Caucasian seventh-grade students in the Southwest. All correlations were highly significant, indicating concurrent validity of the SPM. Correlations computed separately for Hispanic and nonHispanic students also were compared; those differences were not significant. This evidence supports the continued use of the SPM as a measure of nonverbal intellectual ability for Hispanic and nonHispanic students.     

WISC-R performance of children referred to a university center for learning disabilities

This study compared the WISC-R performance of 40 children ranging in age from 6–6 to 15–10, referred to a university center for suspected learning disabilities, with that of two clinically defined groups of learning disabled children. The university center children were found to have WISC-R profiles similar to those of the learning disabled children, with higher overall levels of performance. It was speculated that these children avoid classification as learning disabled by virtue of possessing higher cognitive abilities than those children who are classified. Implications were raised concerning the role of university centers with children experiencing learning difficulties and the accuracy of parental perceptions of learning disabilities.