자연주의적 탐구조사(Naturalistic Inquiry)

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Qualitative research for education: An introduction to theories and methods

How we Think

Much has been written about theory and practice in the law, and the tension between practitioners and theorists. Judges do not cite theoretical articles often; they rarely "apply" theories to particular cases. These arguments are not revisited. Instead the Essay explores the working and interaction of theory and practice, practitioners and theorists. The Essay starts with a story about solving a legal issue using our intellectual tools - theory, practice, and their progenies: experience and "gut." Next the Essay elaborates on the nature of theory, practice, experience and "gut." The third part of the Essay discusses theories that are helpful to practitioners and those that are less helpful. The Essay concludes that practitioners theorize, and theorists practice. They use these intellectual tools differently because the goals and orientations of theorists and practitioners, and the constraints under which they act, differ. Theory, practice, experience and "gut" help us think, remember, decide and create. They complement each other like the two sides of the same coin: distinct but inseparable.

Of Theory and Practice

https://www.cell.com/trends/biotechnology/pdf/S0167-7799(12)00115-1.pdf

Recent advances in bone tissue engineering scaffolds.

Bone is a hierarchically structured composite material which, in addition to its obvious biological value, has been well studied by the materials engineering community because of its unique structure and mechanical properties. This article will review the existing bone literature, with emphasis on the prevailing theories regarding bone formation and structure, which lay the groundwork for proposing a new model to explain how intrafibrillar mineralization of collagen can be achieved during bone formation. Intrafibrillar refers to the fact that growth of the mineral phase is somehow directed by the collagen matrix, which leads to a nanostructured architecture consisting of uniaxially oriented nanocrystals of hydroxyapatite embedded within and roughly [0 0 1] aligned parallel to the long collagen fibril axes. Secondary (osteonal) bone, the focus of this review, is a laminated organic–inorganic composite composed primarily of collagen, hydroxyapatite, and water; but minor constituents, such as non-collagenous proteins (NCPs), are also present and are thought to play an important role in bone formation. To date, there has been no clear understanding of the role of these NCPs, although it has been generally assumed that the NCPs regulate solution crystal growth via some type of ‘epitaxial’ relationship between specific crystallographic faces and specific protein conformers. Indeed, ‘epitaxial’ relationships have been calculated; but in practice, it has not been demonstrated that intrafibrillar mineralization can be accomplished via this route. Because of the difficulty in examining biomineralization processes in vivo , the authors of this article have turned to using in vitro model systems to investigate the possible physicochemical mechanisms that may be involved in biomineralization. In the case of bone biomineral, we have now been able to duplicate the most fundamental level of bone structure, the interpenetrating nanostructured architecture, using relatively simple anionic polypeptides that mimic the polyanionic character of the NCPs. We propose that the charged polymer acts as a process-directing agent, by which the conventional solution crystallization is converted into a precursor process. This polymer-induced liquid-precursor (PILP) process generates an amorphous liquid-phase mineral precursor to hydroxyapatite which facilitates intrafibrillar mineralization of type-I collagen because the fluidic character of the amorphous precursor phase enables it to be drawn into the nanoscopic gaps and grooves of collagen fibrils by capillary action. The precursor then solidifies and crystallizes upon loss of hydration waters into the more thermodynamically stable phase, leaving the collagen fibrils embedded with nanoscopic hydroxyapatite (HA) crystals. Electron diffraction patterns of the highly mineralized collagen fibrils are nearly identical to those of natural bone, indicating that the HA crystallites are preferentially aligned with [0 0 1] orientation along the collagen fibril axes. In addition, studies of etched samples of natural bone and our mineralized collagen suggest that the long accepted “deck of cards” model of bone's nanostructured architecture is not entirely accurate. Most importantly, this in vitro model demonstrates that a highly specific, epitaxial-type interaction with NCPs is not needed to stimulate crystal nucleation and regulate crystal orientation, as has long been assumed. Instead, we propose that collagen is the primary template for crystal organization, but with the important caveat that this templating occurs only for crystals formed from an infiltrated amorphous precursor. These results suggest that the 25-year-old debate regarding bone formation via an amorphous precursor phase needs to be revisited. From a biomedical perspective, in addition to providing possible insight into the role of NCPs in bone formation, this in vitro system may pave the way toward the ultimate goal of fabricating a synthetic bone substitute that not only has a composition similar to bone, but has comparable mechanical properties and bioresorptive potential as natural bone. From a materials chemistry perspective, the non-specificity of the PILP process and capillary infiltration mechanism suggests that non-biological materials could also be fabricated into nanostructured composites using this “biomimetic” strategy.

Bone structure and formation: A new perspective

The purpose of this research review is to open dialog about quantitative, qualitative, and mixed research methods in engineering education research. Our position is that no particular method is privileged over any other. Rather, the choice must be driven by the research questions. For each approach we offer a definition, aims, appropriate research questions, evaluation criteria, and examples from the Journal of Engineering Education. Then, we present empirical results from a prestigious international conference on engineering education research. Participants expressed disappointment in the low representation of qualitative studies; nonetheless, there appeared to be a strong preference for quantitative methods, particularly classroom-based experiments. Given the wide variety of issues still to be explored within engineering education, we expect that quantitative, qualitative, and mixed approaches will be essential in the future. We encourage readers to further investigate alternate research methods by accessing some of our sources and collaborating across education/social science and engineering disciplinary boundaries.

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Quantitative, Qualitative, and Mixed Research Methods in Engineering Education

pH effects on collagen fibrillogenesis in vitro: Electrostatic interactions and phosphate binding

Biologically mineralized tissues are well recognized for their unusual crystal morphologies and hierarchically organized composite structures. The soluble acidic macromolecules associated with biominerals are thought to play an important role in modulating the mineral morphology. Our in vitro studies, which use acidic polypeptide additives to modify crystal growth of calcium-based minerals, have demonstrated a crystallization mechanism that proceeds via a liquid-phase mineral precursor. Various features of the crystals produced via this mechanism, such as "extruded" mineral fibers and mineralized collagen composites, have led us to propose the hypothesis that an amorphous, liquid-phase precursor could play a fundamental role in the morphogenesis of calcium-based biominerals. Although in vivo evidence of this process remains to be determined, we demonstrate crystallization features that mimic bone and dental enamel and suggest that this process could be relevant to biomineralization in both vertebrates and invertebrates.

A New Paradigm for Biomineral Formation: Mineralization via an Amorphous Liquid-Phase Precursor

A novel preparation method of CdS nanoparticles with controllable size and stability is presented. Poly(styrene-block-2-vinylpyridine) (PS-b-P2VP) and cadmium ions form aggregates of single micelles called compound micelles, upon addition of the cadmium acetate salt into a solution of the block copolymer in tetrahydrofuran. The growth of CdS nanoparticles is confined to the core of single micelles after introduction of hydrogen sulfide gas into the solution. UV−visible spectroscopy, fluorescence spectroscopy, and transmission electron microscopy were employed to characterize the prepared nanoparticles. UV−visible absorption spectra show that larger nanoparticles are produced at lower 2VP:Cd2+ molar ratio. UV−visible absorption spectra and fluorescence spectra both indicate that with a decrease of block copolymer concentration in tetrahydrofuran, the size of the CdS nanoparticles decreases. The stability of the CdS nanoparticles and micelles was also investigated. UV−visible results show that the prepared ...

Elliot P. Douglas

Papers

Bone structure and formation: A new perspective

Quantitative, Qualitative, and Mixed Research Methods in Engineering Education

pH effects on collagen fibrillogenesis in vitro: Electrostatic interactions and phosphate binding

A New Paradigm for Biomineral Formation: Mineralization via an Amorphous Liquid-Phase Precursor

Preparation of CdS Nanoparticles in Salt-Induced Block Copolymer Micelles