Cooperative Jahn–Teller transition in Li[Li x Mn2–x ]O4: a muon-spin rotaion/relaxation (μSR) view

The magnetic nature of the spinel antiferromagnet Li[Li _x Mn_2–x ]O₄ with x = 0?0.15 has been studied with muon-spin-rotation and relaxation (μ⁺SR) spectroscopy. Both weak transverse field and zero field μ⁺SR measurements indicate that the whole sample enters into a static disordered magnetic phase below T _N for all the samples measured; T _N = 61 K for LiMn₂O₄, whereas 27–23 K for the x = 0.05?0.15 samples. It was also clarified that both the field distribution width and the field fluctuation rate show a clear change at the Jahn–Teller transition temperature (T _JT = 280 K) for LiMn₂O₄, and a short-range cooperative JT distortion appears below 280 K even for Li[Li_0.15Mn_1.85]O₄.     

Cultural relevance of a fruit and vegetable food frequency questionnaire.

PURPOSE: Canada's multicultural population poses challenges for culturally competent nutrition research and practice. In this qualitative study, the cultural relevance of a widely used semi-quantitative fruit and vegetable food frequency questionnaire (FFQ) was examined among convenience samples of adults from Toronto's Cantonese-, Mandarin-, Portuguese-, and Vietnamese-speaking communities. METHODS: Eighty-nine participants were recruited through community-based organizations, programs, and advertisements to participate in semi-structured interviews moderated in their native language. Data from the interviews were translated into English and transcribed for analysis using the constant comparative approach. RESULTS: Four main themes emerged from the analysis: the cultural relevance of the foods listed on the FFQ, words with multiple meanings, the need for culturally appropriate portion-size prompts, and the telephone survey as a Western concept. CONCLUSIONS: This research highlights the importance of investing resources to develop culturally relevant dietary assessment tools that ensure dietary assessment accuracy and, more important, reduce ethnocentric biases in food and nutrition research and practice. The transferability of findings must be established through further research.     

便携式应用领域电源MOSFET的选择

随着封装技术和硅工艺的进步,具有更高电源密度和更高效率的小尺寸MOSFET正在逐步克服原来与器件尺寸相关的电源处理能力和处理效率问题。     

Tightly linked systems: Reciprocal relations between maternal depressive symptoms and maternal reports of adolescent externalizing behavior.

The frequently observed link between maternal depressive symptoms and heightened maternal reporting of adolescent externalizing behavior was examined from an integrative, systems perspective using a community sample of 180 adolescents, their mothers, fathers, and close peers, assessed twice over a 3-year period. Consistent with this perspective, the maternal depression–adolescent externalizing link was found to reflect not simply maternal reporting biases, but heightened maternal sensitivity to independently observable teen misbehavior as well as long-term, predictive links between maternal symptoms and teen behavior. Maternal depressive symptoms predicted relative increases over time in teen externalizing behavior. Child effects were also found, however, in which teen externalizing behavior predicted future relative increases in maternal depressive symptoms. Findings are interpreted as revealing a tightly linked behavioral-affective system in families with mothers experiencing depressive symptoms and teens engaged in externalizing behavior and further suggest that research on depressive symptoms in women with adolescent offspring should now consider offspring externalizing behaviors as a significant risk factor. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Heuristic Scheduling for Cyclic Steam Injection Projects

This article presents a well steam injection scheduling model which attempts to maximize the profit per day for oil production leases. The model consists of nonlinear regression, nonlinear optimization and a scheduling algorithm. Weekly well production data from a production reporting system is utilized to extend the system to a reporting, operating control and planning system. Thus, it not only provides management with production history but analysis tools for better decisions as well.     

Stability Analysis of Nonlinear System Identification via Delayed Neural Networks

In this brief, the identification problem for time-delay nonlinear system is discussed. We use a delayed dynamic neural network to do on-line identification. This neural network has dynamic series-parallel structure. The stability conditions of on-line identification are derived by Lyapunov-Krasovskii approach, which are described by linear matrix inequality. The conditions for passivity, asymptotic stability and uniform stability are established in some senses. We conclude that the gradient algorithm for updating the weights of the delayed neural networks is stable to any bounded uncertainties     

The sensitivity of fixed-bed biological perchlorate removal to changes in operating conditions and water quality characteristics

Flow rate, electron donor addition, and biomass control were evaluated in order to optimize perchlorate (ClO₄⁻) removal from drinking water using biologically active carbon (BAC) filtration. Influent dissolved oxygen (DO) was lowered from ambient conditions to approximately 2.5 mg/L for all experiments using a nitrogen sparge. When influent nitrate concentration was 0-2.0 mg/L, 1.6-2.8 mg/L as carbon of acetate or ethanol was required to achieve and sustain the complete removal of 50 μg/L perchlorate in a BAC filter. Most or all of the exogenous acetate and ethanol was removed during biofiltration. When a 72-h electron donor feed failure was simulated, a maximum perchlorate breakthrough of 18 μg/L was observed and, once electron donor was reapplied, 9 days were required to reestablish complete perchlorate removal. During a 24-h electron donor feed failure simulation, the maximum effluent perchlorate concentration detected was 6.7 μg/L. Within 24 h of reactivating the electron donor, the filter regained its capacity to consistently remove 50 μg/L perchlorate to below detection. Although biomass growth diminished the filter's ability to consistently remove perchlorate, a cleaning procedure immediately restored stable, complete perchlorate removal. This cleaning procedure was required approximately every 50 days (4800 bed volumes) when influent DO concentration was 2.5 mg/L. Empty-bed contact time (EBCT) experiments showed that 80% perchlorate removal was achieved using a 5-min EBCT, and complete perchlorate removal was observed for an EBCT of 9 min. It was also demonstrated that BAC filtration consistently removed perchlorate to below detection for influent perchlorate concentrations ranging from 10 to 300 μg/L, influent sulfate concentrations between 0 and 220 mg/L, influent pH values of 6.5-9.0, and operating temperatures of 5-22°C.