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31.
AC Faradaic reactions have been reported as a mechanism inducing non-ideal phenomena such as flow reversal and cell deformation in electrokinetic microfluidic systems. Prior published work described experiments in parallel electrode arrays below the electrode charging frequency (fc), the frequency for electrical double layer charging at the electrode. However, 2D spatially non-uniform AC electric fields are required for applications such as in plane AC electroosmosis, AC electrothermal pumps, and dielectrophoresis. Many microscale experimental applications utilize AC frequencies around or above fc. In this work, a pH sensitive fluorescein sodium salt dye was used to detect [H+] as an indicator of Faradaic reactions in aqueous solutions within non-uniform AC electric fields. Comparison experiments with (a) parallel (2D uniform fields) electrodes and (b) organic media were employed to deduce the electrode charging mechanism at 5 kHz (1.5fc). Time dependency analysis illustrated that Faradaic reactions exist above the theoretically predicted electrode charging frequency. Spatial analysis showed [H+] varied spatially due to electric field non-uniformities and local pH changed at length scales greater than 50 μm away from the electrode surface. Thus, non-uniform AC fields yielded spatially varied pH gradients as a direct consequence of ion path length differences while uniform fields did not yield pH gradients; the latter is consistent with prior published data. Frequency dependence was examined from 5 kHz to 12 kHz at 5.5 Vpp potential, and voltage dependency was explored from 3.5 to 7.5 Vpp at 5 kHz. Results suggest that Faradaic reactions can still proceed within electrochemical systems in the absence of well-established electrical double layers. This work also illustrates that in microfluidic systems, spatial medium variations must be considered as a function of experiment time, initial medium conditions, electric signal potential, frequency, and spatial position. 相似文献
32.
A view of science as a culturally‐mediated way of thinking and knowing suggests that learning can be defined as engagement with scientific practices. How students engage in school science is influenced by whether and how students view themselves and whether or not they are the kind of person who engages in science. It is therefore crucial to understand students' identities and how they do or do not overlap with school science identities. In this paper, we describe four middle school African American girls' engagement with science. They were selected in the 7th grade because they expressed a fondness for science in school or because they had science‐related hobbies outside of school. The data were collected from the following sources: interviews of students, their parents and their teachers; observations in science classes; journal writing; and focus groups. These girls' stories provide us with a better understanding of the variety of ways girls choose to engage in science and how this engagement is shaped by their views of what kind of girl they are. © 2000 John Wiley & Sons, Inc. J Res Sci Teach 37: 441–458, 2000. 相似文献
33.
Marianne Skopnik-Chicago Katherine Poblete-Cordero Natali Zamora Roberto Bastías Pablo A. Lizana 《Anatomical sciences education》2021,14(6):836-846
One of the most widely used solutions to fix and preserve organic tissues is formaldehyde, despite reservations regarding its toxicity and the fact that formaldehyde-embalmed bodies lose their original characteristics. Anatomy laboratories have been replacing formaldehyde with solutions that retain the characteristics of fresh tissue. For this purpose, alternative solutions with a very low concentration of formaldehyde or without any formaldehyde have been analyzed. The objective of this study was to compare biometry, coloration, haptic properties, and bacterial load on animal specimens (pig kidneys) embalmed with formaldehyde, and with Chilean Conservative Fixative Solution with and without formaldehyde (formaldehyde chCFS and formaldehyde-free chCFS). Also, the perception of health and biological science students toward specimens treated with different solutions was assessed. The results indicated that there were no significant differences in specimens’ retraction, or bacterial load. Students showed a preference for organs embalmed in formaldehyde chCFS and formaldehyde-free chCFS; indicating that with these treatments they could better visualize structures and that the prosections had greater flexibility and the colors were more similar to those of fresh tissue. Additionally, students recommended the material embalmed in formaldehyde chCFS and formaldehyde-free chCFS for anatomy learning. In contrast, students indicated that formaldehyde-fixation negatively affected their practical experience. In conclusion, embalming with formaldehyde chCFS or formaldehyde-free chCFS provides an advantageous practical experience over the use of formaldehyde and may be an alternative to replace the use of formaldehyde in anatomy laboratories. 相似文献
34.
35.
This investigation reports a typology of maintenance behaviors that were derived through inductive analyses of papers students wrote about their strategies for maintaining various relationships. Ten major strategies were inductively derived: positivity; openness; assurances; sharing tasks; social networks; joint activities; cards/letters/calls; avoidance; anti‐social; and humor. These strategies extend the previous research on relational maintenance strategies. More specifically, the latter five strategies and the subcategories of all the strategies are additions to Stafford and Canary's (1991)typology. In addition, analyses revealed the positivity, openness, assurances, sharing tasks, and cards/letters/calls differed in their frequency of use among lovers, relatives, friends and others. 相似文献
36.
Attitudes and approaches toward the collection, use, and care of color photographs have evolved enormously since the official arrival of commercially viable color photographic processes in the early twentieth century. This article traces the evolution of collection, exhibition, and preservation practices for works of art in color photography over the last few decades, as represented by one institution, The Metropolitan Museum of Art. 相似文献
37.
Katherine M. Hertlein Markie L. C. Twist 《Journal of College Student Psychotherapy》2017,31(3):215-230
The practice of sexting is becoming increasingly common among college students but has the potential to both initiate productive interactions with others and interfere with relationship development. The purpose of this paper is to report on the findings of a study on sexting among college students and to provide a framework through which practitioners working with this population would be able to effectively intervene. Implications for clinical practice include more specific assessment questions for practitioners, focus on better managing riskier behavior, and guidance toward using technology in relationally responsible and supportive ways. 相似文献
38.
Katherine I. Miller - Katherine Miller is a Professor Director of Graduate Studies in the 《Journal of Applied Communication Research》2008,36(1):8-32
There is growing interest in the role of emotion when considering communication in the workplace. This work has most often considered workers in front-line service positions in investigations of emotional labor, and human service workers in investigations of empathy and emotional work. In this study, we consider processes of both emotional labor and emotional work in the financial planning profession. Financial planners occupy a role requiring ongoing relationships with clients, conversations about the often emotional topic of money, and a need to manage emotion in a variety of interaction contexts. Thus, from extant theory and literature regarding emotion and communication, we proposed research questions regarding the roles of emotional labor and emotional work in the financial planning profession. These questions were investigated in a web-based survey study of almost 300 professional financial planners and supporting interviews with 14 financial planners. Results indicate support for existing theory on emotional work, extensions to current research regarding emotional labor, and important implications for the role of emotion and communication in a range of professional service roles. 相似文献
39.
运动对糖尿病大鼠ASP影响的研究 总被引:1,自引:0,他引:1
研究运动对链脲佐菌素所致糖尿病大鼠ASP的影响。选用雄性SD大鼠,随机分为4组(每组10只),即:正常对照组,正常运动组,糖尿病模型组,糖尿病模型+运动组。运动组进行10周的游泳训练。结果表明:1)糖尿病模型组与正常对照组大鼠相比,血浆ASP浓度、血糖、TG、和LDL明显升高,血清FFA有升高趋势,血清胰岛素和ISI明显降低;2)糖尿病模型+运动组较其非运动组血浆ASP浓度、血糖、TG、TC、FFA和LDL明显降低,血清胰岛素和HDL含量明显升高。提示:糖尿病机体血浆ASP浓度升高,伴随着其活性下降,使得FFA和富舍TG的脂蛋白消除障碍,长期中等负荷运动可以降低血浆中ASP浓度,增加其活性,进而降低FFA和TG水平,升高HDL,改善糖尿病机体的脂质代谢,预防其慢性并发症的发生。 相似文献
40.
Katherine Turpin 《Religious education (Chicago, Ill.)》2017,112(4):407-417
Christian education served as a tool of White supremacy that played a central role in the devastation of millions of human lives throughout the colonial era of Western expansion. An adequate account of how Christian education paired with colonial imperatives helps to identify where the legacy of White supremacy and imperial domination lives on in contemporary practices of Christian faith formation and religious education. While any educational venture requires authority and is an act of power, humility is an essential partnering virtue for Christian educators who do not wish to replicate this history of domination. 相似文献