13 research outputs found

    Resonant Particle Heating of an Electron Plasma by Oscillating Sheaths,” Phys

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    The first unambiguous measurements of a bounce-resonance effect in a non-neutral plasma are presented. Two striking signatures are observed when a magnetized electron column is heated by oscillating an end sheath. First, the heating rate increases by a factor of 10 4 as the oscillation frequency is increased by a factor of 10 near the thermal electron bounce frequency. Second, the heating is enhanced when the sheaths at both ends are oscillated out of phase, but is suppressed when they are in phase. The measured rates are in quantitative agreement with a resonant particle heating theory. [S0031-9007(98

    Amount of Time to Eat Lunch Is Associated with Children’s Selection and Consumption of School Meal Entrée, Fruits, Vegetables, and Milk

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    Background There are currently no national standards for school lunch period length and little is known about the association between the amount of time students have to eat and school food selection and consumption. Objective Our aim was to examine plate-waste measurements from students in the control arm of the Modifying Eating and Lifestyles at School study (2011 to 2012 school year) to determine the association between amount of time to eat and school meal selection and consumption. Design We used a prospective study design using up to six repeated measures among students during the school year. Participants/setting One thousand and one students in grades 3 to 8 attending six participating elementary and middle schools in an urban, low-income school district where lunch period lengths varied from 20 to 30 minutes were included. Main outcome measures School food selection and consumption were collected using plate-waste methodology. Statistical analyses performed Logistic regression and mixed-model analysis of variance was used to examine food selection and consumption. Results Compared with meal-component selection when students had at least 25 minutes to eat, students were significantly less likely to select a fruit (44% vs 57%; PPPP Conclusions During the school year, a substantial number of students had insufficient time to eat, which was associated with significantly decreased entrée, milk, and vegetable consumption compared with students who had more time to eat. School policies that encourage lunches with at least 25 minutes of seated time might reduce food waste and improve dietary intake

    Dynamics of non‐neutral plasmas

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