Computational and dynamic NMR investigation of 2,2-dimesityl-1,1,1,3,3,3-hexamethyltrisilane.

The structure and rotational barrier for the mesityl-silicon bond of 2,2-dimesityl-1,1,1,3,3,3-hexamethyltrisilane have been investigated by 1 H- and 13 C-variable temperature nuclear magnetic resonance (NMR) as well as by density functional theory structural calculations. The calculations show that the lowest energy structure has C2 symmetry with nonequivalent ortho methyl groups, consistent with the crystal structure and solution NMR. The nonequivalent ortho methyl groups exchange through a Cs transition state with a calculated relative free energy of 11.0 kcal mol-1 . The barrier for this rotation found by dynamic NMR is 13.4 ± 0.2 kcal mol-1 at 298 K.

What works? Process evaluation of a school-based fruit and vegetable distribution program in Mississippi.

BACKGROUND: During the 2004-2005 school year, the Mississippi Department of Education, Office of Child Nutrition, initiated a pilot program to distribute free fruit and vegetable snacks to students during the school day. This article describes the first-year implementation of the Mississippi Fruit and Vegetable Pilot Program. METHODS: The process evaluation addressed where, when, and how produce was distributed; what was distributed; challenges and successes; and recommended modifications. Five of the 25 program schools were selected to participate in the evaluation; selection was based on grade levels served and demographic characteristics. Data were collected from program staff (N = 11) and administrators (N = 6) via interviews and logs; student (N = 42) and parent (N = 19) focus groups; student questionnaires (N = 660); and school staff questionnaires (N = 207). RESULTS: Distributing fresh fruit and vegetable snacks at school was well received by staff and students. Most schools distributed the fresh fruit and vegetable snacks at morning break in classrooms or a central courtyard. Twenty-two types of fresh fruit, 4 types of dried fruit, and 7 types of vegetables were served to students during the program year. Commonly distributed fruit included apples, oranges, pears, bananas, and tangerines. Carrots were the staple vegetable, followed by celery. Key challenges included getting students to try new foods and receiving the produce in a timely manner without spoiling. Main successes included seeing students try new fruit and vegetable snacks, having the program run smoothly, and teacher support. CONCLUSIONS: The program fit well within the school structure and could be an effective component of a multifaceted approach to enhancing child nutrition.