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Communication—An Analysis of Shear Forces in Post-CMP PVA Brush Scrubbing for Stationary and Rotating Wafers
No full textAfter defining certain sign conventions for sliding velocity and shear force for a PVA brush scrubbing process, a simple kinematics model is used to calculate net sliding velocities in the brush-wafer contact region. Next, a series of experiments are performed where brush velocity is gradually increased while the wafer is kept stationery, and repeated again with the wafer rotating at a certain velocity. For a stationary wafer, with increasing brush velocity, partial lubrication takes effect which results in less brush asperity contact (i.e. a reduction in SF). For a rotating wafer, SF decreases significantly. We attribute this to the net negative sliding velocity across the wafer that partially offsets the positive SF values. However, SF rises with brush velocity which is likely due to fluid distribution effects and increased brush asperity-wafer contact
Understanding the Reasons Behind Defect Levels in Post-Copper-CMP Cleaning Processes with Different Chemistries and PVA Brushes
Get PDFResults from a series of post-CMP PVA scrubbing marathon runs performed in a high-volume manufacturing fab are scientifically explained via a series of controlled laboratory tests. The major differences in the ingredients within the cleaning solutions, and some of the key physical properties of the brushes are identified and their effects on various critical factors are studied. These include the magnitude of shear forces present in the brush-solution-wafer interface, the water uptake and porosity of the brushes, the diffusivity of a given cleaning solution through the micro-pores and macro-pores of each type of brush, the open-circuit potential in a dynamic process, and the availability of the cleaning fluid between the brush nodules and the wafer surface. Results show a strong inverse correlation between wafer-level defects and shear force. The latter is shown to decrease with solution availability at the brush-wafer interface which in turn is shown to depend on brush porosity and the diffusion rate of the solution through the pores. Our understanding is further strengthened by dynamic electrochemical analysis data where we see a greater interfacial chemical activity (i.e., an increase in corrosion current) as solution availability is increased
Strategic Design of Antimicrobial Hydrogels Containing Biomimetic Additives for Enhanced Matrix Responsiveness and HDFa Wound Healing Rates
No full textSupramolecular nanocomposite materials have emerged as a leading interdisciplinary research area that exploits synergistic relationships at the nanoscale to enhance the properties (mechanical and chemical) of next-generation biopolymeric materials. Hydrogels synthesized from natural biopolymers have emerged because of their intrinsic properties such as noncytotoxicity and biodegradability as well as their well-defined three-dimensional, noncovalent network that is ideal for modification and functionalization. Therefore, it is critical to develop a mechanistic understanding tailored to the nuances involved in the interactions of the biopolymer scaffold with the functional additives present in these complex matrixes. This work will discuss the strategic design of hydrogels placing emphasis on the selection of the biopolymer network and the critical role that the incorporation of additives such as biomimetic cross-linking agents (lactones/amino acids) and antimicrobial nanoparticles (NPs) has on the properties and responsiveness of the final nanocomposite. Results have shown that the hydrogen bonding capacity of the biomimetic additives and antimicrobial agents (i.e., AgNPs) impacts the packing density of the hydrogel network and therefore modulates the resultant swellability. Furthermore, the addition of Ag-coated TiO2 NPs (Ag/TiO2 NPs) and biomimetic additives provided antimicrobial activity along with enhanced closure rates of simulated wounds in adult human dermal fibroblasts
A Window, Mirror, and Wall: How Educators Use Twitter for Professional Learning
Get PDFTeachers and other professionals increasingly utilize Twitter as a medium for professional expression and professional learning. These types of Twitter exchanges often take place in formal chats which are moderated by professional organizations or other knowledge brokers in the field. As moderated public online forums become more common, educators may wish to understand the benefits and limitations of this type of professional learning. This paper reports on a study of educators’ discourse in two hosted Twitter chats focused on global education and analyzes the ways in which these types of chats align with research on high-quality professional learning. Results indicate that Twitter chats provide multiple components of high-quality professional learning, namely a focus on content, collaboration, and teacher agency; to a lesser extent, they may provide peer coaching and allow for conversations across a sustained duration. However, other components of meaningful professional learning are not possible in this context, as it is not job-embedded and does not provide active learning or supported opportunities to practice
Participatory Action Research in a Time of Digital Literacies
No full textKatie is a high school science teacher who participated in an ongoing participatory action research project. She is part of a larger professional development program (PROJECT) that aims to incorporate students’ funds of knowledge to assist in the development of curriculum that promotes greater equitable outcomes for English learners (ELs). Katie’s reflection of the way in which language plays a significant role in students’ content development aims for a better understanding of why an integrative approach to curriculum development is critical. Katie’s yearlong participatory action research project included the use of digital literacies to support her students’ science and language development. The use of digital literacies in the classroom allowed her ELs to have exposure to the English language and collectively pushed them to maintain their native language as an asset to their academic success. This article investigates the following two questions: (1) “How can the use of digital literacy foster students’ language learning and maintenance of a native language?” and “How does this practice lead to instruction that promotes equitable learning outcomes?
Sustainability in Agriculture and Local Food Systems: A Solution to a Global Crisis (Chapter from Zero Hunger)
Get PDFThe Food and Agriculture Organization of the United Nations defines a food system as the entire range of stakeholders and their interlinked value-adding activities involved in the production, distribution and aggregation, processing, marketing, consumption and waste management of food products that originate from agriculture, forestry, and parts of the broader economic, societal and natural environments in which they are embedded (Take and Systems 2015). To be considered sustainable, a food system must deliver food security and nutrition for all in such a way that the economic, social, and environmental bases to generate food security and nutrition for future generations are not compromised (Bassarab et al. 2019; FAO 2017; FAO et al. 2018). A sustainable food system lies at the heart of the United Nations’ Sustainable Development Goals (SDGs).https://digitalcommons.lewisu.edu/biology_fac-books/1000/thumbnail.jp
Understanding a Child’s Social-Emotional Development
No full textChildren encounter numerous forms of stressors in their daily living. Some of these stressors are mild, and the child can continue to function with minimal negative consequences. Other stressors are more impactful on the child\u27s development and can result in various levels of impairment. Often children experience difficulties in their social-emotional functioning when faced with severe stressors. The ACE survey outlines the negative impact on a child\u27s overall living when one or more stressors are present in their life. The ability of a counselor to understand what influences a child\u27s social-emotional development is critical to helping that child adjust successfully. This workshop will focus on identifying various stressors in a child\u27s life that can have a negative outcome on their overall academic, social, and emotional development. Additionally, participants will learn about the role of healthy relationships and techniques to endure adverse experiences in childhood
