Observation of molecular processes inside living cells is fundamental to a quantitative understanding of how biological systems function. Specifically, decoding the complex behavior of single molecules enables us to measure kinetics, transport, and self-assembly at this fundamental level that is often veiled in ensemble experiments. In the past decade, rapid developments in fluorescence microscopy, fluorescence correlation spectroscopy, and fluorescent labeling techniques have enabled new experiments to investigate the robustness and stochasticity of diverse molecular mechanisms with high spatiotemporal resolution. This review discusses the concepts and strategies of structural and functional imaging in living cells at the single-molecule level with minimal perturbations to the specimen.

The influence of low-temperature gaseous carburization on the fatigue behavior of AISI 316L austenitic stainless steel was investigated. Tension-compression axial fatigue tests were performed under ambient conditions on untreated and carburized AISI 316L. The results show that the carburized AISI 316L has a 22% higher endurance limit compared to untreated AISI 316L. Fractography investigations with scanning electron microscope (SEM) reveal that for the untreated AISI 316L fatigue cracks initiate at the surface regardless of the applied stress level. For the carburized AISI 316L fatigue cracks initiate at the surface for relatively high-level stresses; for relatively low-level stresses fatigue cracks initiate at inclusions beyond the carburized case. After carburization, the ductility in the outmost 10 μm of the carburized case has significantly reduced, leading to micro-crack occurrence during fatigue tests and associated relaxation of compressive residual stress in this region. Beyond this surface-adjacent region, no evident stress relaxation occurs due to the enhanced yield strength

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