We present a fast, accurate and robust parallel Levenberg-Marquardt minimization optimizer, GPU-LMFit, which is implemented on graphics processing unit for high performance scalable parallel model fitting processing. GPU-LMFit can provide a dramatic speed-up in massive model fitting analyses to enable real-time automated pixel-wise parametric imaging microscopy. We demonstrate the performance of GPU-LMFit for the applications in superresolution localization microscopy and fluorescence lifetime imaging microscopy.
Development of a compact fluorescence-based detection system for use in a micro-analytical system, such as a point-of-care diagnostic system, often requires a multi-channel microfluidic chip system. Since the materials used for microfluidic chips usually are transparent in the visible region and have a refractive indices higher than that of air or the surrounding environment, the fluorescence emission and scattered excitation light can propagate through the chip. We observed that such propagation can cause cross-talk between adjacent channels, and may become the major source of noise in the system and/or photo bleach the fluorescent samples in the adjacent channels, particularly for the small distances between the channels found in microfluidic chips, usually in order of several micro m. We monitored this cross-talk using fluorescein as a fluorescent sample and Mylar sheeting as a microfluidic chip material. We then discuss how this cross-talk can be avoided using a simple, inexpensive and effective method.
Laser light can exert forces on matter by exchanging momentum in form of radiation pressure and refraction. Although these forces are small, they are sufficient to trap and manipulate microscopic particles [Phys. Rev. Lett. 24, 156 (1970)]. In this paper, we study the optical trapping phenomena by using computer simulation to show a detailed account of the process of momentum exchange between a focused light and a microscopic particle in an optical trapping by use of the finite difference time domain method. This approach provides a practical routine to predict the magnitude of the exchanged momentum, track the particle in a trapping process, and determine a trapping point, where dynamic equilibrium happens. Here we also theoretically describe the transfer procedure of orbital angular momentum from a focused optical vortex to the particle.
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