Portfolios and pedagogy : an examination of ideology and use

Portfolio use in writing studies contexts is becoming ubiquitous and, as such, portfolios are in danger of being rendered meaningless and thus require that we more fully theorize and historicize portfolios. To this end, I examine portfolios: both the standardized portfolio used for assessment purposes and the personalized portfolio used for entering the job market. I take a critical look at portfolios as a form of technology and acknowledge some of the dangers of blindly using portfolios for gaining employment in the current economic structure of fast capitalism. As educators in the writing studies fields, it is paramount that instructors have a critical awareness of the consequences of portfolio creation on students as designers, lifelong learners, and citizens of a larger society. I argue that a better understanding of the pedagogical implications for portfolio use is imperative before implementing them in the classroom, and that a social-epistemic approach provides a valuable rethinking of portfolio use for assessment purposes. Further, I argue for the notions of meditation and transformation to be added alongside collection, selection, and reflection because they enable portfolio designers and evaluators alike to thoughtfully consider new ways of meaning-making and innovation. Also important and included with meditation and transformation is the understanding that students are ideologically positioned in the educational system. For them to begin recognizing their situatedness is a step toward becoming designers of change. The portfolio can be a site for that change, and a way for them to document their own learning and ways of making meaning over a lifetime.

Non-invasive method to predict viscosity and size using total internal reflection fluorescence microscopy (TIRFM) system

This study develops an automated analysis tool by combining total internal reflection fluorescence microscopy (TIRFM), an evanescent wave microscopic imaging technique to capture time-sequential images and the corresponding image processing Matlab code to identify movements of single individual particles. The developed code will enable us to examine two dimensional hindered tangential Brownian motion of nanoparticles with a sub-pixel resolution (nanoscale). The measured mean square displacements of nanoparticles are compared with theoretical predictions to estimate particle diameters and fluid viscosity using a nonlinear regression technique. These estimated values will be confirmed by the diameters and viscosities given by manufacturers to validate this analysis tool. Nano-particles used in these experiments are yellow-green polystyrene fluorescent nanospheres (200 nm, 500 nm and 1000 nm in diameter (nominal); 505 nm excitation and 515 nm emission wavelengths). Solutions used in this experiment are de-ionized (DI) water, 10% d-glucose and 10% glycerol. Mean square displacements obtained near the surface shows significant deviation from theoretical predictions which are attributed to DLVO forces in the region but it conforms to theoretical predictions after ~125 nm onwards. The proposed automation analysis tool will be powerfully employed in the bio-application fields needed for examination of single protein (DNA and/or vesicle) tracking, drug delivery, and cyto-toxicity unlike the traditional measurement techniques that require fixing the cells. Furthermore, this tool can be also usefully applied for the microfluidic areas of non-invasive thermometry, particle tracking velocimetry (PTV), and non-invasive viscometry.