Influence of surface roughness on the color of dental-resin composites     

Ghinea R  Ugarte-Alvan L  Yebra A  Pecho OE  Paravina RD  Perez Mdel M 《Journal of Zhejiang University. Science. B》2011,12(7):552-562

This study deals with the influence of surface roughness on the color of resin composites. Ten resin composites (microfilled, hybrid, and microhybrid) were each polished with 500-grit, 1 200-grit, 2 000-grit, and 4 000-grit SiC papers. The roughness parameter (R _a) was measured using a Plμ confocal microscope, and field-emission scanning electron microscope (Fe-SEM) images were used to investigate filler morphology. Color was measured using a spectroradiometer and a D65 standard illuminant (geometry diffuse/0° specular component excluded (SCE) mode). Surface roughness decreased with grit number and was not influenced by filler size or size distribution. A significant influence of R _a on lightness (L*) was found. Lightness increased with decreases in roughness, except for specimens that underwent polishing procedure 4 (PP4; 500-grit, 1 200-grit, 2 000-grit, and 4 000-grit SiC papers consecutively). Generally, it was found that surface roughness influenced the color of resin composites. The composites that underwent PP1 (500-grit SiC paper) exhibited significant differences in chroma (C*), hue (h°), and lightness (L*) compared to composites that underwent PP3 (500-grit, 1 200-grit, and 2 000-grit SiC papers consecutively) and PP4. Color difference (ΔE*) between the polishing procedures was within acceptability thresholds in dentistry.  相似文献   

Writing childbirth: women’s rhetorical agency in labor and online     

Laura J. Jackman 《Technical Communication Quarterly》2019,28(3):296-298

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Attributions and Attitudes of Mothers and Fathers in Colombia     

Di Giunta L  Tirado LM  Márquez LA 《Parenting, science and practice》2011,11(2-3):116-128

OBJECTIVE: The present study examined mean level similarities and differences as well as correlations between mothers' and fathers' attributions regarding successes and failures in caregiving situations and progressive versus authoritarian attitudes. DESIGN: Interviews were conducted with both mothers and fathers in 108 Colombian families. RESULTS: Fathers reported higher uncontrollable success attributions and higher authoritarian attitudes than did mothers, whereas mothers reported higher modernity of attitudes than did fathers; only the gender differences related to parental attitudes remained significant after controlling for parents' age, education, and possible social desirability bias. Medium effect sizes were found for concordance between parents in the same family for attributions regarding uncontrollable success and progressive attitudes after controlling for parents' age, education, and possible social desirability bias. CONCLUSIONS: This work elucidates ways that parent gender relates to attributions regarding parents' success and failure in caregiving and to progressive versus authoritarian parenting attitudes in Colombia.  相似文献   

Certain Changes to Training Companies Due to Social Web Development     

Manuel Fandos Igado  ;Jose Ignacio Aguaded Gomez 《美中教育评论》2011,(3):346-353

Companies use many different marketing strategies in order to make their products known and place their corporate images and brandings in the market. Besides, nowadays, being on the Intemet is a must for every company striving for success. The development and implementation of Web 2.0 or social web are threatening the basis of the ways of mixing with other people. A company devoted to open and distance learning, such as Master-D Corporation, a clear example of how a proper and planned use of the different possibilities offered by the Web 2.0, based on blogs, allows a company to achieve bigger market shares and brand positioning following the win-win principle. Blogs are, undoubtedly, channels of communication that prove the power of attraction of good information. These changes are affecting everybody and, in particular, companies and institutions related to people＇s education, teaching and training for their inclusion in society and labor market. This essay brings up some reflections in two ways： The first one deals with some reasons why education is also related to the concept of ＂company＂; and the second one deals with how these changes generated by Web 2.0 are affecting some training companies, represented in this case by Master-D,  相似文献   

Sound Archive Access: Revealing Emergent Cultures     

Laura Garbes 《Journal of Radio & Audio Media》2019,26(1):79-87

This article contends that researchers can and should be active participants in making sound archives more accessible. In fact, such advocacy can be consequential in setting up possibilities for creative research on race within radio history and sound studies. Using the example of NPR’s All Things Considered archive spanning from 1971–1983, I demonstrate how academics and archivists can work together to make possible the preservation and accessibility of sound archives. This particular collaboration offers an opportunity to take a cultural approach to understanding newsroom diversity, more specifically: the cultural constraints of linguistic norms and the emergent cultures that arise as aberrations from such norms. The article reflects on this project’s implications for other scholars who work with archives that wish to invest in sound archive preservation and use.  相似文献   

Managing Serials in a Large Digital Library: Case Study of the UNT Libraries Digital Collections     

Hannah Tarver  Laura Waugh  Daniel Gelaw Alemneh  Mark Phillips 《期刊图书馆员》2015,68(1-4):353-360

The Portal to Texas History (http://texashistory.unt.edu) and the University of North Texas (UNT) Digital Library (http://digital.library.unt.edu) contain more than 445,000 items collectively, hosted by the UNT Libraries. These collections include a variety of serial publications such as newsletters, magazines, scholarly journals, annual reports, and yearbooks. Many of these serials are key resources for the user groups of both repositories. In this article, we discuss the importance of serials within our collections, some of the challenges, the standards we use, and how we leverage metadata to facilitate access to serials for diverse global users.  相似文献   

Modeling of musculoskeletal structure and function using a modular bond graph approach     

Laura A. Wojcik 《Journal of The Franklin Institute》2003,340(1):63-76

The dynamic effects of muscle strength, timing of muscle activations, and body geometry have been modeled for a wide variety of human activities. These types of models require the development of complex system equations that account for the effects of rigid-body dynamics, musculotendon actuators, passive and active resistance to motion, and other physiological structures. One way in which model refinement can be expedited is through the use of bond graph modeling techniques. While bond graph techniques have been used extensively in a broad variety of applications, they have been used only sparingly in the field of biomechanics, despite the potential suitability of a modular, multidomain approach to the modeling of musculoskeletal function. In the current paper, bond graph modules representing muscle function and rigid-body motions of underlying bone structures are introduced. The system equations generated with the use of these models are equivalent to those developed with more traditional techniques, but the modules can be more easily used in conjunction with control models of neuromuscular function for the simulation of overall dynamic motor performance.  相似文献   

The influence of task and gender on search and evaluation behavior using Google     

Lori Lorigo  Bing Pan  Helene Hembrooke  Thorsten Joachims  Laura Granka  Geri Gay 《Information processing & management》2006

To improve search engine effectiveness, we have observed an increased interest in gathering additional feedback about users’ information needs that goes beyond the queries they type in. Adaptive search engines use explicit and implicit feedback indicators to model users or search tasks. In order to create appropriate models, it is essential to understand how users interact with search engines, including the determining factors of their actions. Using eye tracking, we extend this understanding by analyzing the sequences and patterns with which users evaluate query result returned to them when using Google. We find that the query result abstracts are viewed in the order of their ranking in only about one fifth of the cases, and only an average of about three abstracts per result page are viewed at all. We also compare search behavior variability with respect to different classes of users and different classes of search tasks to reveal whether user models or task models may be greater predictors of behavior. We discover that gender and task significantly influence different kinds of search behaviors discussed here. The results are suggestive of improvements to query-based search interface designs with respect to both their use of space and workflow.  相似文献   

The development and use of an instrument to measure willingness to seek help from peers and teachers when studying college mathematics     

Tracy L. Morris  Shing-Huei Lee  Laura L. B. Barnes 《Learning Environments Research》2008,11(3):227-243

As part of a three-phase study, 18 items were developed to measure aspects of a student’s willingness to seek help from and/or work with peers and teachers when studying college mathematics. In the first phase, 24 items were developed and administered to 165 undergraduate college students. During the second phase, 20 items, modified from the first instrument, were completed by a sample of 314 undergraduate college students. The sample was randomly divided in half and principal factor analysis with varimax rotation was performed on the first half. Two factors emerged and were interpreted as: Willingness to Work with Students (nine items); and Willingness to Seek Help from Teachers (nine items). Based on the results of the exploratory factor analysis, confirmatory factor analysis was performed on the second half of the sample. Coefficient α estimates were calculated to assess internal consistency. In the third phase, the final 18-item survey was given to 140 undergraduate college students and confirmatory factor analysis was again performed based on the results of the exploratory factor analysis from Phase II. Recommendations for future uses of these scales are given.  相似文献   

The contrasting discourses in the professional lives of educators in Vancouver, Canada     

Peter P. Grimmett  Diane Dagenais  Laura D’Amico  Marianne Jacquet  Roumi Ilieva 《Journal of Educational Change》2008,9(2):101-121

This study investigated the relationship between education policy changes and the working conditions of teachers and school leaders in Vancouver, Canada. We found that policy does shape educators’ discourse about their work conditions. This shaping manifested itself in the emotions teachers experience as they attempt to construct their identity as professional educators. Apparent contradictions emerged in educators’ discussions of their work conditions, particularly their contrasting reports of feeling satisfied with their working environment, yet concerned about issues related to workload and recognition. Two different discourses, the political and the professional, emerged at a deep level of practice. These discourses express conflicting emotions about teaching and teachers’ identity struggles in a context of rapid policy changes. The political discourse is framed around a partisan response to policy changes. The professional discourse focuses on engagement in satisfying educational activities. This study proffers a different conclusion to other studies implying a lack of understanding of practice by policy reformers. It suggests that, while teachers are very aware of policy changes, frequently engaging in a partisan critique thereof, they nevertheless temper that critique with a professional discourse shaped by pedagogical concerns in the local context. This concern with the classroom context enables them to focus their energies on constructing their sense of professional identity that frequently leads them to reinterpret policy initiatives from a local educator’s perspective. While the political discourse has trappings of despair, the professional–pedagogical contains glimpses of hope. We wish to express our appreciation of the work of Barbara Waldern in the analysis that supports the findings about the professional lives of educators.  相似文献