Confocal and two-photon microscopy : image enhancement /

Confocal and two-photon microcopy have become essential tools in biological research and today many investigations are not possible without their help. The valuable advantage that these two techniques offer is the ability of optical sectioning. Optical sectioning makes it possible to obtain 3D visuahzation of the structiu-es, and hence, valuable information of the structural relationships, the geometrical, and the morphological aspects of the specimen. The achievable lateral and axial resolutions by confocal and two-photon microscopy, similar to other optical imaging systems, are both defined by the diffraction theorem. Any aberration and imperfection present during the imaging results in broadening of the calculated theoretical resolution, blurring, geometrical distortions in the acquired images that interfere with the analysis of the structures, and lower the collected fluorescence from the specimen. The aberrations may have different causes and they can be classified by their sources such as specimen-induced aberrations, optics-induced aberrations, illumination aberrations, and misalignment aberrations. This thesis presents an investigation and study of image enhancement. The goal of this thesis was approached in two different directions. Initially, we investigated the sources of the imperfections. We propose methods to eliminate or minimize aberrations introduced during the image acquisition by optimizing the acquisition conditions. The impact on the resolution as a result of using a coverslip the thickness of which is mismatched with the one that the objective lens is designed for was shown and a novel technique was introduced in order to define the proper value on the correction collar of the lens. The amoimt of spherical aberration with regard to t he numerical aperture of the objective lens was investigated and it was shown that, based on the purpose of our imaging tasks, different numerical apertures must be used. The deformed beam cross section of the single-photon excitation source was corrected and the enhancement of the resolution and image quaUty was shown. Furthermore, the dependency of the scattered light on the excitation wavelength was shown empirically. In the second part, we continued the study of the image enhancement process by deconvolution techniques. Although deconvolution algorithms are used widely to improve the quality of the images, how well a deconvolution algorithm responds highly depends on the point spread function (PSF) of the imaging system applied to the algorithm and the level of its accuracy. We investigated approaches that can be done in order to obtain more precise PSF. Novel methods to improve the pattern of the PSF and reduce the noise are proposed. Furthermore, multiple soiu'ces to extract the PSFs of the imaging system are introduced and the empirical deconvolution results by using each of these PSFs are compared together. The results confirm that a greater improvement attained by applying the in situ PSF during the deconvolution process.

Teachers' processes of negotiating meaning of new curriculum

This qualitative study addresses the question of how teachers negotiate meaning of new curriculum to better understand how curriculum is transformed from a theoretical construct to a practical one. Through interviews with 5 teachers, their experiences were examined as they negotiated the process of implementing new curriculum. Three theoretical constructs provided the entry point into the study: epistemology, teacher knowledge, and teacher learning. Using inductive analysis, 4 points or attributes of negotiation emerged: reference, growth, autonomy, and reconciliation. These attributes provided a theoretical framework from which a constructivist conceptualization of teacher learning and teacher knowledge could serve to understand the process of how teachers negotiate meaning of curriculum. Studied and theorized in this way, teacher knowledge and teacher learning are seen to be inextricably linked in a relationship that is dynamically changed by forces of stability and instability. Theorizing the negotiation of meaning from a constructivist epistemology also strengthened the assertion that negotiating meaning is a unique structural process, and that knowledge construction is therefore unique to each knower and subject to experience in a particular time and place. The implications for such a theory are, first, that it questions the legitimacy of privatized teacher practice and, second, that it calls for a renewed conceptualization of collegial network and relationship to strengthen the capacity for negotiating meaning of curricular initiatives. Understanding the relationship of curricular theory and negotiating meaning also has implications for curriculum development. In particular, the study highlights the necessity of professional discretion and the generative process of negotiating meaning.