We introduce a method for improved dielectrophoretic (DEP) discrimination and separation of viable and nonviable yeast cells. Due to the higher cell wall permeability of nonviable yeast cells compared with their viable counterpart, the cross-linking agent glutaraldehyde (GLT) is shown to selectively cross-link nonviable cells to a much greater extent than viable yeast. The DEP crossover frequency (cof) of both viable and nonviable yeast cells was measured over a large range of buffer conductivities (22 μS∕cm–400 μS∕cm) in order to study this effect. The results indicate that due to selective nonviable cell cross-linking, GLT modifies the DEP cof of nonviable cells, while viable cell cof remains relatively unaffected. To investigate this in more detail, a dual-shelled oblate spheroid model was evoked and fitted to the cof data to study cell electrical properties. GLT treatment is shown to minimize ion leakage out of the nonviable yeast cells by minimizing changes in cytoplasm conductivity over a large range of ionic concentrations. This effect is only observable in nonviable cells where GLT treatment serves to stabilize the cell cytoplasm conductivity over a large range of buffer conductivity and allow for much greater differences between viable and nonviable cell cofs. As such, by taking advantage of differences in cell wall permeability GLT magnifies the effect DEP has on the field induced separation of viable and nonviable yeasts. 相似文献
Abstract The Science Explorations program was developed by the Milwaukee Public Museum (MPM) out of a desire to use the unique resources of MPM to advance informal science education and to address a community need of local and national concern: improving science education and accessibility for underserved audiences. In 2002, with support from the National Science Foundation (NSF) and private donors, MPM launched this after‐school program for a target group of urban, mostly minority, middle school girls, a group at risk for underachievement in science and technology. The museum staff built a combined program with five middle schools and also sought to reach out to family members of the participating girls in order to increase support for the young women's science endeavors. A three‐year evaluation of the Science Explorations program demonstrated positive findings from primarily quantitative data. An aim of this article is to present findings from the qualitative data to shed light on the reasons this program met nearly all of its targets. Findings from case studies and qualitative interviews suggest that the museum staff's efforts to demystify science—a process that provided ongoing access to real scientific endeavors and invited personal contact with scientists—influenced the program's success. Findings also suggest that strong school liaisons may help increase family support for young women's scientific pursuits, which can in turn play a role in their success in this program. 相似文献
This research is distinctive in that it not only provides an example of one of the few cross-cultural studies in science education, but also it used multiple research methods from different paradigms in exploring classroom learning environments in Taiwan and Australia. This article describes the validation and use of an English and Mandarin version of the What is Happening in this Class? (WIHIC) questionnaire in junior high school science classes in Australia and Taiwan. When the WIHIC was administered to 1,081 students in 50 classes in Australia and to 1,879 students in 50 classes in Taiwan, data analysis supported the reliability and factorial validity of the questionnaire, and revealed differences between Taiwanese and Australian classrooms. Although the study commenced from a more positivistic framework, favouring a more objectivist view, as the study progressed, it employed an interpretative framework and drew on elements of constructivist and critical theory paradigms. This article outlines the researchers' use of multiple research methods including classroom observations, in-depth interviews and narratives. The themes which emerged from the data gathered using these methods helped to make sense of classroom environments that were created in each country.
Many studies examine the development of infants born at risk for medical and developmental problems during the early years of life, but far fewer follow these children into their school years. This project compared high-risk vs. low-risk children in their performance on the WPPSI at pre- and postkindergarten levels. In general, both groups of children demonstrated increases in performance; however, their patterns of performance were different. The high-risk children showed increases predominantly in the Performance areas of the test, whereas the low-risk children demonstrated increases predominantly in the Verbal areas. 相似文献
The Journal of the Medical Library Association (JMLA) selects new editorial board members every year. In the spring of 2021, JMLA used a new process for reviewing and selecting applicants for the limited number of open editorial board positions. This reevaluation of the selection process was spurred by a desire to create a more diverse and representative board. Changes to the procedures for selecting new editorial board members included having an open call for editorial board members, creating an application form, creating a selection committee to screen applicants, creating a form for the selection committee to extract data from applications, and creating a two-step process for screening and then selecting board members. As part of construction of this new process, areas for continued improvement were also identified, such as refining the application form to allow more specific answers to areas of interest to the selection committee. The newly created selection process for editorial board members constitutes a significant change in JMLA processes; however, more can be done to build on this work by further refining the selection process and ensuring that new members are selected in a transparent and streamlined manner. 相似文献
This article aims to help teacher educators consider how to build racial literacy in their White teacher candidates, providing guidance through pedagogical strategies and approaches based on our and others’ research. In addition, much of the pedagogy that we developed in working with our White teacher candidates can be translated to teachers working with White students at other levels, and it can also help teacher educators develop their own racial literacy. 相似文献