On the rules for aquatic locomotion

We present unifying rules governing the efficient locomotion of swimming fish and marine mammals. Using scaling and dimensional analysis, supported by new experimental data, we show that efficient locomotion occurs when the values of the Strouhal (St) number St(=f A/U) and A∗(=A/L), two nondimensional numbers that relate forward speed U, tail-beat amplitude A, tail-beat frequency f , and the length of the swimmer L are bound to the tight ranges of 0.2–0.4 and 0.1–0.3, respectively. The tight range of 0.2–0.4 for the St number has previously been associated with optimal thrust generation. We show that the St number alone is insufficient to achieve optimal aquatic locomotion, and an additional condition on A∗ is needed. More importantly, we show that when swimming at minimal power consumption, the Strouhal number of a cruising swimmer is predetermined solely by the shape and drag characteristics of the swimmer. We show that diverse species of fish and cetaceans cruise indeed with the St number and A∗ predicted by our theory. Our findings provide a physical explanation as to why fast aquatic swimmers cruise with a relatively constant tail-beat amplitude of approximately 20% of the body length, and their swimming speed is nearly proportional to their tail-beat frequenc

Dentin dysplasia type I

This paper describes a rare case of genetically determined dentin dysplasia type I in 26-year-old male patient. The paper highlights anatomical and radiological aspects of dental abnormalities and emphasizes the significance of the education of both general practitioners and paediatricians as regards referring patients with diagnosed dentin dysplasia for a multi-specialty therapy.

How accurate are parental responses concerning their fourth-grade children's school-meal participation, and what is the relationship between children's body mass index and school-meal participation based on parental responses?

<p>Abstract</p> <p>Background</p> <p>This article investigated (1) parental response accuracy of fourth-grade children's school-meal participation and whether accuracy differed by children's body mass index (BMI), sex, and race, and (2) the relationship between BMI and school-meal participation (based on parental responses).</p> <p>Methods</p> <p>Data were from four cross-sectional studies conducted from fall 1999 to spring 2003 with fourth-grade children from 13 schools total. Consent forms asked parents to report children's usual school-meal participation. As two studies' consent forms did not ask about lunch participation, complete data were available for breakfast on 1,496 children (51% Black; 49% boys) and for lunch on 785 children (46% Black; 48% boys). Researchers compiled nametag records (during meal observations) of meal participation on randomly selected days during children's fourth-grade school year for breakfast (average nametag days across studies: 7-35) and for lunch (average nametag days across studies: 4-10) and categorized participation as "usually" (≥ 50% of days) or "not usually" (< 50% of days). Weight and height were measured. Concerning parental response accuracy, marginal regression was used with agreement between parental responses and nametag records as the dependent variable; independent variables were BMI, age, sex, race, and study. Concerning a relationship between BMI and school-meal participation, marginal regression was used with BMI as the dependent variable; independent variables were breakfast participation, lunch participation, age, sex, race, and study.</p> <p>Results</p> <p>Concerning breakfast participation and lunch participation, 74% and 92% of parents provided accurate responses, respectively. Parental response accuracy was better for older children for breakfast and lunch participation, and for Black than White children for lunch participation. Usual school-meal participation was significantly related to children's BMI but in opposite directions -- positively for breakfast and inversely for lunch.</p> <p>Conclusions</p> <p>Parental response accuracy of children's school-meal participation was moderately high; however, disparate effects for children's age and race warrant caution when relying on parental responses. The BMI results, which showed a relationship between school-meal participation (based on parental responses) and childhood obesity, conflict with results from a recent article that used data from the same four studies and found no significant relationship when participation was based on nametag records compiled for meal observations.</p

Translating it into real life: a qualitative study of the cognitions, barriers and supports for key obesogenic behaviors of parents of preschoolers

BACKGROUND: Little is known about preschool parents' cognitions, barriers, supports and modeling of key obesogenic behaviors, including breakfast, fruit and vegetable consumption, sugary beverage intake, feeding practices, portion sizes, active playtime, reduced screen-time, sleep and selection of child-care centers with characteristics that promote healthy behaviors. METHODS: Thus, the purpose of this study was to examine these factors via survey and focus groups among 139 parents of 2- to 5-year-old children. Standard content analysis procedures were used to identify trends and themes in the focus group data, and Analysis of Variance was used to test for differences between groups in the survey data. RESULTS: Results showed 80% of parents ate breakfast daily, consumed sugary beverages 2.7 ± 2.5SD days per week, and had at least two different vegetables and fruits an average of 5.2 ± 1.8SD and 4.6 ± 2.0SD days per week. Older parents and those with greater education drank significantly fewer sugary drinks. Parents played actively a mean 4.2 ± 2.2 hours/week with their preschoolers, who watched television a mean 2.4 ± 1.7 hours/day. Many parents reported having a bedtime routine for their preschooler and choosing childcare centers that replaced screen-time with active play and nutrition education. Common barriers to choosing healthful behaviors included lack of time; neighborhood safety; limited knowledge of portion size, cooking methods, and ways to prepare healthy foods or play active indoor games; the perceived cost of healthy options, and family members who were picky eaters. Supports for performing healthful behaviors included planning ahead, introducing new foods and behaviors often and in tandem with existing preferred foods and behaviors, and learning strategies from other parents. CONCLUSIONS: Future education programs with preschool parents should emphasize supports and encourage parents to share helpful strategies with each other.This item is part of the UA Faculty Publications collection. For more information this item or other items in the UA Campus Repository, contact the University of Arizona Libraries at [email protected]