This report seeks to examine the literature related to written corrective feedback in second/foreign language classrooms in order to inform the most effective pedagogical practices related to this topic. I begin with an article by Truscott which would set the tone for the academic debate on whether or not to provide written corrective feedback in L2 classrooms. In his 1996 article Truscott claims that written corrective feedback a) is not helpful, b) is harmful, and c) should be eliminated entirely. Chapter 1 covers this debate, referred to as the Truscott Debate, reviewing the many articles that directly answer the challenge laid down by Truscott (1996). Following a review of this academic debate, I examine the literature that investigates the specific providers of feedback (teachers or peer feedback), the types of feedback (direct or indirect) and the degree of focus related to those feedback options. Chapter 4 reviews other factors that can also affect the efficacy of written corrective feedback, such as student motivation, learner levels, and oral feedback in conjunction with written feedback and online feedback. Chapter 5 puts forth particular circumstances in which each type of feedback can be efficacious, offering a guide for the provision of feedback in a variety of circumstances. / text

This work presents the development and analysis of a system that combines the concepts of light field microscopy and particle image velocimetry (PIV) to measure three-dimensional velocities within a microvolume. Rectanglar microchannels were fabricated with dimensions on the order of 350-950 micrometers using a photolithographic process and polydimethylsiloxane (PDMS). The flow was seeded with fluorescent particles and pumped through microchannels at Reynolds numbers ranging from 0.016 to 0.028. Flow at Reynolds numbers in the range of 0.02 to 0.03 was seeded with fluorescent particles and pumped through microchannels. A light field microscope with a lateral resolution of 6.25 micrometers and an axial resolution of 15.5 micrometers was designed and built based on the concepts described by Levoy et al. Light field images were captured continuously at a frame rate of 3.9 frames per second using a Canon 5D Mark II DSLR camera. Each image was post processed to render a stack of two-dimensional images. The focal stacks were further post processed using various methods including bandpass filtering, 3D deconvolution, and intensity-based thresholding, to remove effects of diffraction and blurring. Subsequently, a multi-pass, three-dimensional PIV algorithm was used to measure channel velocities. Results from PIV analysis were compared with an analytical solution for fully-developed cases, and with CFD simulations for developing flows. Relative errors for fully-developed flow measurements, within the light field microscope refocusing range, were approximately 5% or less. Overall, the main limitations are the reduction in lateral resolution, and the somewhat low axial resolution. Advantages include the relatively low cost, ease of incorporation into existing micro-PIV systems, simple self-calibration process, and potential for resolving instantaneous three-dimensional velocities in a microvolume.