A Trade-Off Study Revealing Nested Timescales of Constraint

This study investigates human performance in a cyclic Fitts task at three different scales of observation, either in the presence (difficult condition) or in the absence (easy condition) of a speed–accuracy trade-off. At the fastest scale, the harmonicity of the back and forth movements, which reflects the dissipation of mechanical energy, was measured within the timeframe of single trials. At an intermediate scale, speed and accuracy measures were determined over a trial. The slowest scale pertains to the temporal structure of movement variability, which evolves over multiple trials. In the difficult condition, reliable correlations across each of the measures corroborated a coupling of nested scales of performance. Participants who predominantly emphasized the speed-side of the trade-off (despite the instruction to be both fast and accurate) produced more harmonic movements and clearer 1/f scaling in the produced movement time series, but were less accurate and produced more random variability in the produced movement amplitudes (vice versa for more accurate participants). This implied that speed–accuracy trade-off was accompanied by a trade-off between temporal and spatial streams of 1/f scaling, as confirmed by entropy measures. In the easy condition, however, no trade-offs nor couplings among scales of performance were observed. Together, these results suggest that 1/f scaling is more than just a byproduct of cognition. These findings rather support the claim that interaction-dominant dynamics constitute a coordinative basis for goal-directed behavior

Brazilian Immigrant Mothers’ Beliefs and Practices Related to Infant Feeding: A Qualitative Study

Background: Exclusive breastfeeding for the first 6 months of life and timely introduction of appropriate solid foods are important determinants of weight status in infancy and later life stages. Disparities in obesity rates among young children suggest that maternal feeding practices during the first 2 years of life may contribute to these disparities. Brazilians are a growing immigrant group in the United States, yet little research has focused on parental beliefs and behaviors affecting the health of Brazilian immigrant children in the United States. Research aim: This study aimed to explore beliefs and infant-feeding practices of Brazilian immigrant mothers in the United States. Methods: Focus group discussions were conducted with Brazilian immigrant mothers. Transcripts were analyzed using thematic analysis and themes categorized using the socioecological model. Results: Twenty-nine immigrant Brazilian mothers participated in the study. Analyses revealed that all participants breastfed their infants. The majority initiated breastfeeding soon after childbirth. However, most mothers did not exclusively breastfeed. They used formula and human milk concomitantly. Family and culture influenced mothers’ infant-feeding beliefs and practices in early introduction of solid foods. Conclusion: As the number of children in the United States growing up in families of immigrant parents increases, understanding influences on Brazilian immigrant mothers’ infant-feeding practices will be important to the development of effective interventions to promote healthy infant feeding and weight status among Brazilian children. Interventions designed for Brazilian immigrant families should incorporate an understanding of social context, family, and cultural factors to develop health promotion messages tailored to the needs of this ethnic group

Thermal-Shock Resistance and Fracture-Strength Behavior of Two Tool Carbides

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66260/1/j.1151-2916.1976.tb09415.x.pd

Stress-Biased Anisotropic Microcracking in Zirconia Polycrystals

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65263/1/j.1151-2916.1990.tb05152.x.pd

Response to Comment on “Estimating the reproducibility of psychological science”

Gilbert et al. conclude that evidence from the Open Science Collaboration's Reproducibility Project: Psychology indicates high reproducibility, given the study methodology. Their very optimistic assessment is limited by statistical misconceptions and by causal inferences from selectively interpreted, correlational data. Using the Reproducibility Project: Psychology data, both optimistic and pessimistic conclusions about reproducibility are possible, and neither are yet warranted.status: publishe

Task-Dependent Inhomogeneous Muscle Activities within the Bi-Articular Human Rectus Femoris Muscle

The motor nerve of the bi-articular rectus femoris muscle is generally split from the femoral nerve trunk into two sub-branches just before it reaches the distal and proximal regions of the muscle. In this study, we examined whether the regional difference in muscle activities exists within the human rectus femoris muscle during maximal voluntary isometric contractions of knee extension and hip flexion. Surface electromyographic signals were recorded from the distal, middle, and proximal regions. In addition, twitch responses were evoked by stimulating the femoral nerve with supramaximal intensity. The root mean square value of electromyographic amplitude during each voluntary task was normalized to the maximal compound muscle action potential amplitude (M-wave) for each region. The electromyographic amplitudes were significantly smaller during hip flexion than during knee extension task for all regions. There was no significant difference in the normalized electromyographic amplitude during knee extension among regions within the rectus femoris muscle, whereas those were significantly smaller in the distal than in the middle and proximal regions during hip flexion task. These results indicate that the bi-articular rectus femoris muscle is differentially controlled along the longitudinal direction and that in particular the distal region of the muscle cannot be fully activated during hip flexion