Dimensional studies of specific microscopic fibre structures in deteriorated parchment before and during shrinkage

This paper reports the first systematic study of the dimensions of morphological changed microscopic collagen fibres in historical and new reference parchments with the aim to improve the knowledge on deterioration and the diagnosis of their damage in connection with conservation activities. The dimensions of fibres from the parchments were measured before and during shrinkage, with special emphasis on fibres with degradation characteristics designated as “pearls on a string” and “butterflies”. In addition, measurements of the total shrinkage of the length of fibres and pieces of parchment were also carried out. The observations support the assumption that in vivo transformation of the fibre structure by natural ageing is similar to that taking place when heating parchment and fibres in water. Based on statistical cluster analysis, four subpopulations of pearls representing different stages of deterioration are found. Moreover, the dimensional changes in the specific structures observed at room temperature can be related to specific temperatures in the interval of shrinkage suggesting that the hydrothermal stability of the fibres may be predicted on the basis of the ratio between length and width of the so-called pearls (P_l/P_w). The total shrinkage measured is drastic, in average around 56% for fibres and 43 to 48% for pieces of parchment depending on the direction of the skin. The total shrinkage of fibres corresponds to a mean change in the ratio P_l/P_w from around 10 to around 2.3. Finally, relations between the measured dimensions at the microscopic level with those of collagen at nanoscopic and molecular levels including known and potential chemical splitting points strongly indicate that the formation of the butterfly-like fragments formed by cleavage of two adjacent pearls in the fibre can be ascribed to chemical modification of specific tripeptides in the collagen molecule.     

ORGANIZING,MANAGING, AND EVALUATING SERVICE-LEARNING PROJECTS

As educators work to develop methods to capture the attention of greater numbers of students, they are finding merit in some of the tried-and-true methods of the past. Service-learning is one of those methods with a sound reputation that is now enjoying a comeback. Previously known as experiential learning, service-learning expands on the best aspects of volunteerism and classical internships. Service-learning projects are beneficial for students, faculty members, site providers, and clients. Regardless of whether projects are loosely constructed with little oversight or highly prescribed and closely monitored, a systematic approach to organization, management, and evaluation is important. This article offers an adaptable framework for educators who wish to incorporate new or improve existing service-learning experiences within their gerontology programs.     

Teacher MA attainment rates, 1970–2000

The share of female teachers in the U.S. with an MA more than doubled between 1970 and 2000. This increase is puzzling, as it is much larger than that of other college-educated women, and it occurred over a period of declining teacher aptitude. I estimate the contribution of changes in teacher demographic characteristics, increases in the returns to an MA, and changes in teacher certification requirements to increases in teacher MA attainment rates. I find that the majority of the rise in attainment not attributable to secular trends and increases in the average age of teachers can be explained by increases in the returns to an MA among teachers. The increase in MA returns among teachers presents a second puzzle, as there is little evidence that master's degrees increase teacher productivity.     

Humidity Control in Historic Buildings in Denmark

ABSTRACT

Historic buildings in Denmark have a high relative humidity (RH) all year, so the interiors are exposed to biological degradation. The acceptable range for RH is 60–70%, which is higher than the usual recommendations for museums and galleries. There are two options for humidity control: conservation heating or mechanical dehumidification. Calculation of the energy performance of a generic building was used to determine which method is the most efficient. Studies of a cottage in Liselund Park, and of two medieval churches in Hellerup and Vemb have confirmed these predictions: dehumidification is less energy consuming than conservation heating in buildings with poor thermal insulation and a moderate air infiltration rate (AER?<?0.6?h^?1). Dehumidification is suitable for historic buildings, where heating is not needed for human comfort. A condensing dehumidifier uses less than half the energy per kg water compared to an absorption dehumidifier. But it does not work at temperatures below 2°C. The combination of a condensing dehumidifier and a little heating to prevent frost is the most energy efficient solution for humidity control. These results are only valid in mild and humid climatic conditions similar to Denmark.     

Proofs and refutations in the undergraduate mathematics classroom

In his 1976 book, Proofs and Refutations, Lakatos presents a collection of case studies to illustrate methods of mathematical discovery in the history of mathematics. In this paper, we reframe these methods in ways that we have found make them more amenable for use as a framework for research on learning and teaching mathematics. We present an episode from an undergraduate abstract algebra classroom to illustrate the guided reinvention of mathematics through processes that strongly parallel those described by Lakatos. Our analysis suggests that the constructs described by Lakatos can provide a useful framework for making sense of the mathematical activity in classrooms where students are actively engaged in the development of mathematical ideas and provide design heuristics for instructional approaches that support the learning of mathematics through the process of guided reinvention.     

Protein and cell patterning in closed polymer channels by photoimmobilizing proteins on photografted poly(ethylene glycol) diacrylate

Definable surface chemistry is essential for many applications of microfluidic polymer systems. However, small cross-section channels with a high surface to volume ratio enhance passive adsorption of molecules that depletes active molecules in solution and contaminates the channel surface. Here, we present a one-step photochemical process to coat the inner surfaces of closed microfluidic channels with a nanometer thick layer of poly(ethylene glycol) (PEG), well known to strongly reduce non-specific adsorption, using only commercially available reagents in an aqueous environment. The coating consists of PEG diacrylate (PEGDA) covalently grafted to polymer surfaces via UV light activation of the water soluble photoinitiator benzoyl benzylamine, a benzophenone derivative. The PEGDA coating was shown to efficiently limit the adsorption of antibodies and other proteins to <5% of the adsorbed amount on uncoated polymer surfaces. The coating could also efficiently suppress the adhesion of mammalian cells as demonstrated using the HT-29 cancer cell line. In a subsequent equivalent process step, protein in aqueous solution could be anchored onto the PEGDA coating in spatially defined patterns with a resolution of <15 μm using an inverted microscope as a projection lithography system. Surface patterns of the cell binding protein fibronectin were photochemically defined inside a closed microfluidic device that was initially homogeneously coated by PEGDA. The resulting fibronectin patterns were shown to greatly improve cell adhesion compared to unexposed areas. This method opens for easy surface modification of closed microfluidic systems through combining a low protein binding PEG-based coating with spatially defined protein patterns of interest.     

Preparing Students for College and Careers: The Causal Role of Algebra II

In educational research and policy circles, college and career readiness is generating great interest. States are adopting various policy initiatives, such as rigorous curricular requirements, to increase students’ preparedness for life after high school. Implicit in many of these initiatives is the idea that college readiness and career readiness are essentially the same thing. This assumption has persisted, largely untested. Our paper explores this assumption in greater depth. Using two national datasets and an instrumental variables approach to mitigate selection bias, we evaluated the effects of completing Algebra II in high school on subsequent college and career outcomes (i.e., persistence and graduation as well as wages and career advancement). Results suggest Algebra II matters more for college outcomes than career outcomes and more for students completing Algebra II in the early 1990s than in the mid-2000s. Study limitations are discussed along with directions for future research, such as evaluating the opportunity cost associated with taking Algebra II for students seeking careers upon high school completion.     

Replacing Old Spatial Empires of the Mind

In this article we argue for the spatialization of research on educational transfer in the field of comparative education within a theoretical framework that focuses on networks, connections, and flows. We present what we call a "spatial empire of the mind," which is comprised of a set of taken-for-granted "truths" about space and place that have legitimized much research in the social sciences. We critique this spatial empire of the mind and present some of the core ideas associated with the spatial turn. The next part of the article reviews three possible ways that new spatial theorizing has been taken up in educational research. Here we make reference to existing educational studies that engage with new ways of rethinking space and place. The argument that we put forward is that the most promising approach, for research on educational transfer within the field of comparative education, is network spatiality. We argue that there is great value in rethinking space and place not simply as objects of study, but within a theoretical framework that focuses on networks, interconnections, and movements within and between them, as well as their productive capacity to produce and shape knowledge, identities, and human subjectivities.     

Juicing the game design process: towards a content centric framework for understanding and teaching game design in higher education

The aim of this article is to advance a framework for understanding and teaching game design in higher education, in order to address complexities inherent in teaching game design courses. Everyday teaching and learning game design often deviate from the standard textbook model of game design. In reality everyday teaching and learning operate with handling game design curriculum, how to think games, and how to organise the development process. The presented framework merge curriculum, thinking, and process guided by the game design concept of juiciness. The framework will be presented by dismantling the standard textbook model of game design into three; game design (curriculum), game design thinking (thinking), and game development (organisation). In this perspective game design is concerned with game mechanics, game design thinking preoccupied with paper prototyping, metaphor, and framing, while game developments addresses player experience including play and game testing. This article will coin vertical design as juiciness as opposed to horizontal design understood as expanding system layout. Juiciness will be placed as a guiding principle in the relationship between designers and designed content as an aspect of designer intentions and motivations. Lastly, the content centric framework will be presented by merging game design, game design thinking, game development, vertical design with selected aspects of accepted software development strategies as an approach to teaching and learning game design in higher education.