New dietetic practitioners' perspectives on their education and training

Purpose: To elucidate the complex phenomenon of dietitian professional socialization, we examined factors that influence people's decisions to pursue a career in dietetics and how education and training processes influence the professional socialization of dietitians. Methods: Participants (n=12) had less than three years of work experience and included alumni from three Canadian universities representing different models of entry to practice. Three one-on-one interviews were conducted with each participant. Results: The key influencing factor in participants' decision to pursue dietetics was the perceived congruence between dietetics and other aspects of their lives, including early interests and experiences (sports, food and cooking, an eating disorder), career aspirations (science, health care), and social networks (the desire to be a professional). A pivotal experience during high school or while enrolled in or after graduation from another program prompted participants' awareness of and subsequent decision to pursue a career in dietetics. Supportive relationships were vital to participants' professional socialization. Conclusions: Recruitment materials and education opportunities should help aspiring dietitians develop a clear idea of what being a dietitian means. Dietetic educators must attend to the informational and relational aspects involved in shaping future practitioners' dietitian identities.     

Pigeons encode relative geometry.

Pigeons were trained to search for hidden food in a rectangular environment designed to eliminate any external cues. Following training, the authors administered unreinforced test trials in which the geometric properties of the apparatus were manipulated. During tests that preserved the relative geometry but altered the absolute geometry of the environment, the pigeons continued to choose the geometrically correct corners, indicating that they encoded the relative geometry of the enclosure. When tested in a square enclosure, which distorted both the absolute and relative geometry, the pigeons randomly chose among the 4 corners, indicating that their choices were not based on cues external to the apparatus. This study provides new insight into how metric properties of an environment are encoded by pigeons. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

运算放大器的进展

如何为不同应用选择最好的运算放大器。运算放大器自1963年问世以来,走过了很长的发展道路,并成为所有线性系统中事实上的标准部件。几乎每个大型半导体制造商的产品线中都有运算放大器这个产品。而且应用场合的不同也促使放大器的封装从TO-8的金属罐状封装发展至2mm×2mm的芯片式封装,如图1所示。目前放大器的性能水平已达到了如下指标,这在20世纪60年代是闻所未闻的。●带宽超过1GHz;●转换速率超过5000V/μs;●工作电流低于10μA;●工作电压低至0.9V;●输入失调电压低于20μV。C M O S与双极性工艺制造工艺和前沿设计技术的进步使得…     

Fruit and vegetable consumption: benefits and barriers.

Few people on Prince Edward Island meet the goal of consuming five or more servings of vegetables and fruit a day. The main objective of this qualitative study was to explore the perceptions of the nutritional benefits and barriers to vegetable and fruit intake among adult women in Prince Edward Island. Participants were 40 women aged 20-49, with or without children at home, who were or were not currently meeting the objective of eating five or more fruit and vegetable servings a day. In-home, one-on-one interviews were used for data collection. Thematic analysis was conducted on the transcribed interviews. Data were examined for trustworthiness in the context of credibility, transferability, and dependability. Most participants identified one or more benefits of eating fruit and vegetables; however, comments tended to be non-specific. The main barriers that participants identified were effort, lack of knowledge, sociopsychological and socioenvironmental factors, and availability. Internal influences, life events, and food rules were identified as encouraging women to include vegetables and fruit in their diets. Given the challenges of effecting meaningful dietary change, dietitians must look for broader dietary behavioural interventions that are sensitive to women's perceptions of benefits and barriers to fruit and vegetable intake.     

Tuning Electrical and Thermal Transport in AlGaN/GaN Heterostructures via Buffer Layer Engineering

Progress in wide bandgap, III–V material systems based on gallium nitride (GaN) has enabled the realization of high‐power and high‐frequency electronics. Since the highly conductive, 2D electron gas (2DEG) at the aluminum gallium nitride (AlGaN)/GaN interface is based on built‐in polarization fields and is confined to nanoscale thicknesses, its charge carriers exhibit much higher mobilities compared to their doped counterparts. This study shows that such 2DEGs also offer the unique ability to manipulate electrical transport separately from thermal transport, through the examination of fully suspended AlGaN/GaN diaphragms of varied GaN buffer layer thickness. Notably, ≈100 nm thin GaN layers can considerably impede heat flow without electrical transport degradation. These achieve 4× improvement in the thermoelectric figure of merit (zT) over externally doped GaN, with state‐of‐the‐art power factors of 4–7 mW m^‐1 K^‐2. The remarkable tuning behavior and thermoelectric enhancement, elucidated here for the first time in a polarization‐based heterostructure, are achieved because electrons are at the heterostructured interface, while phonons are within the material system. These results highlight the potential for using 2DEGs in III–V materials for on‐chip thermal sensing and energy harvesting.     

面向大规模定制的产品配置设计研究

大规模定制生产逐渐成为21世纪制造业发展的主流生产模式.面向大规模定制生产的产品配置设计能够较好的解决用户需求的多样化、个性化同企业低成本、高效益之间的平衡问题.本文从已有产品实例出发,系统的研究了以产品族模型、配置规则库为核心的产品配置平台的建模技术,并利用实例推理和规则推理两种方法实现了基于此平台的产品配置.     

Comparison of Low Pressure and Medium Pressure UV Lamps for UV/H2O2 Treatment of Natural Waters Containing Micro Pollutants

UV/H₂O₂ advanced oxidation is an effective barrier against organic micro pollutants. Several studies have focused on the degradation of a wide range of pollutants, but regarding the comparison of low-pressure mercury lamps (LP) with medium-pressure mercury lamps (MP) with respect to energy consumption by the UV/H₂O₂ process, little is known so far. Although the absorbance of H₂O₂ at 254 nm is low, the results of this research show that the yield of hydroxyl radical formation (OH_CT) with LP lamps is comparable or higher than with MP lamps. In a water matrix with a background absorbance due to organics and nitrate, H₂O₂ absorbs UV light very effectively at 254 nm. Generally, due to the contribution of direct photolysis, the degradation of pollutants is better with MP-UV/H₂O₂ than with LP-UV/H₂O₂ at the same UV fluence. Therefore, with LP-UV/H₂O₂ micro pollutants are predominantly degraded through reaction with OH radicals. However, due to the much higher efficiency of LP lamps in converting electrical energy to UV-C light, the energy required to achieve 90% degradation (E_EO) of pesticides and pharmaceuticals can be significantly lower with LP-UV/H₂O₂ than with MP-UV/H₂O₂. Results of bench-scale tests show E_EO data of the LP-UV/H₂O₂ process to be 30%–50% lower than for the MP-UV/H₂O₂ process. At these process conditions MS2 phage inactivation was found to be more than 8 logs for both MP-UV/H₂O₂ and LP-UV/H₂O₂.     

Food intake and academic performance among adolescents

Purpose: Prince Edward Island adolescents' food use was examined, as were possible associations between food use and grade, sex, and academic performance. Methods: Participants (n=325) were purposively selected from four junior high schools. Dietary data were collected using an adaptation of the 2003 Youth Risk Behavior Survey. Demographic information and self-reported academic performance were also assessed. Vegetable and fruit (VF) and milk scores were created, and multivariate analysis was performed to identify which combination of grade, sex, VF score, and milk score predicted academic performance best. Results: Mean daily intakes of VF (4.3 +/- 2.9 servings) and milk (1.7 +/- 1.4 servings) were below recommended levels. Students with higher academic performance (average grades above 90%) were more likely to consume milk, vegetables, and fruit daily than were those who reported lower grades. There was no significant difference in the proportion of adequate milk intakes between students reporting higher and lower academic performance. Conclusions: The association between VF intake and academic performance supports the need for further research with a larger, more representative sample.     

Rats (Rattus norvegicus) encode the shape of an array of discrete objects.

To navigate efficiently, a traveler must establish a heading using a frame of reference. A large body of evidence has indicated that humans and a variety of nonhuman animals utilize the geometry, or shape, of enclosed spaces as a frame of reference to determine their heading. An important and yet unresolved question is whether shape information from arrays of discrete objects and enclosed environments are represented, and utilized, in the same way. In the present study, rats were presented with a reference memory task in which they had to find water that was hidden in 1 of 4 discrete and unique objects placed at the vertices of a rectangle. The results indicate that rats could utilize both feature and geometry cues to locate the hidden goal. The rats' performance declined during transformation tests using a triangular array, indicating that the rats may have encoded the primary axis of the object array, rather than local cues, to direct their search. (PsycINFO Database Record (c) 2010 APA, all rights reserved)