[Food water sources analysis of adults in four cities of China in summer].

OBJECTIVE: To investigate the food water sources of adults in the four cities of China in summer. METHODS: A total of 64 adults aged 18 - 60 yrs from four cities (Beijing, Shanghai, Chengdu and Guangzhou)were selected using convenient sampling method. The food samples were collected by using duplicate portion method and the water content of food samples were determined by using the national standard. The information on amounts and types of daily drinking soup was recorded by subjects using a quantitative measurement. RESULTS: A total of 63 subjects had completed the investigation. The median of daily water from food of subjects was 1157 ml, while water from staple food was 480 ml, the median ratio of which accounting for 41.8% of water from food. Water from dishes was 427 ml, the median ratio of which accounting for 37.9% of water from food. Water from soups was 133 ml, the median ratio of which accounting for 13.8% of water from food. Water from snacks was 0 ml, the median ratio of which accounting for 6.4% of water from food. The medians of water from staple food (384, 388 and 435 ml, respectively) in Beijing, Shanghai and Guangzhou was significant lower than that of Chengdu subjects' (900 ml, χ(2) = 21.27, P = 0.000). But the median proportion of water from staple food of subjects in Beijing (47.7%) was significantly higher than that in Chengdu (43.2%), Shanghai (42.9%) and Guangzhou (33.9%) (χ(2) = 8.69, P = 0.034). The median of amount and proportion of water from soups of subjects in Guangzhou (267 ml, 24.4%) and Chengdu(278 ml, 15.7%) was significantly higher than that in Shanghai (133 ml, 9.0%) and Beijing (100 ml, 5.8%) (amount: χ(2) = 22.52, P = 0.000;proportion: χ(2) = 16.27, P = 0.001). CONCLUSION: The staple food and dishes are the main sources of daily food water.

Superconductivity modulated by quantum size effects.

We have fabricated ultrathin lead films on silicon substrates with atomic-scale control of the thickness over a macroscopic area. We observed oscillatory behavior of the superconducting transition temperature when the film thickness was increased by one atomic layer at a time. This oscillating behavior was shown to be a manifestation of the Fabry-Perot interference modes of electron de Broglie waves (quantum well states) in the films, which modulate the electron density of states near the Fermi level and the electron-phonon coupling, which are the two factors that control superconductivity transitions. This result suggests the possibility of modifying superconductivity and other physical properties of a thin film by exploiting well-controlled and thickness-dependent quantum size effects.