We demonstrate a common-path tomographic diffractive microscopy technique for three-dimensional (3D) refractive-index (RI) imaging of unstained living cells. A diffraction grating is utilized to generate a reference beam that traverses a blank region of the sample in a common-path off-axis interferometry setup. Single-shot phase images captured at multiple illumination angles are used for 3D RI reconstruction based on optical diffraction tomography. The common-path configuration shows lower temporal phase fluctuations and better RI resolution than a Mach-Zehnder configuration. 3D subcellular RI distributions of live HeLa cells are quantified.
Hepatobiliary metabolism is one of the major functions of the liver. However, little is known of the relationship between the physiological location of the hepatocytes and their metabolic potential. By the combination of time-lapse multiphoton microscopy and first order kinetic constant image analysis, the hepatocellular metabolic rate of the model compound 6-carboxyfluorescein diacetate (6-CFDA) is quantified at the single cell level. We found that the mouse liver can be divided into three zones, each with distinct metabolic rate constants. The sinusoidal uptake coefficients k of Zones 1, 2, and 3 are respectively 0.239 ± 0.077, 0.295 ± 0.087, and 0.338 ± 0.133 min, the apical excreting coefficients k of Zones 1, 2, and 3 are 0.0117 ± 0.0052, 0.0175 ± 0.0052, and 0.0332 ± 0.0195 min, respectively. Our results show not only the existence of heterogeneities in hepatobiliary metabolism, but they also show that Zone 3 is the main area of metabolism.
To facilitate the application of plasmonic nanoparticles (PNPs) in high-throughput detection, we develop a hyperspectral imaging system (HSIS) combining dark-filed microscopy and imaging Fourier transform spectrometry to measure scattering spectra from immobilized PNPs. The current setup has acquisition time of 5 seconds and spectral resolution of 21.4 nm at 532.1 nm. We demonstrate the applicability of the HSIS in conjunction with spectral data analysis to quantify multiple types of PNPs and detect small changes in localized surface plasmon resonance wavelengths of PNPs due to changes in the environmental refractive index.
Relay-aided multiuser communications are crucial for future 5G systems. In this paper, we consider the twouser multiple access relay channel (MARC), in which two users transmit messages to a common destination with the assistance of a half-duplex relay. The decode-and-forward (DF) based lattice coding was shown to be effective for the MARC in our previous work [1]. However when the links from the users to the relay are weak, DF protocol may fail to decode all users at the relay. Aiming to solve this problem, we propose a new lattice coding where the relay only needs to decode an integer-weightedsum of users' lattice codewords, re-maps it with a modulobased mapper and then forwards the corresponding codeword. Although the decoding at the relay is akin to the orthogonal compute-and-forward protocol, we relax the restriction imposed by previous works that the users have to be silent when the relay is transmitting to avoid interference. The key ingredient is the joint multi-user lattice decoding performed at the destination. This jointly decoding strategy not only complicates the corresponding code design but also the error analysis. To find the proper integerweighted-sum at the relay for the destination's joint decoder, we also solve a non-convex integer problem by carefully transforming and relaxing it to a convex one. Simulation results show that the proposed non-orthogonal lattice coding can outperform existing schemes in a variety of channel settings.
Fractional photothermolysis (FP) induces discrete columns of photothermal damage in skin dermis, thereby promoting collagen regeneration. This technique has been widely used for treating wrinkles, sun damage, and scar. In this study, we evaluate the potential of multiphoton microscopy as a noninvasive imaging modality for the monitoring of skin rejuvenation following FP treatment. The dorsal skin of a nude mouse underwent FP treatment in order to induce microthermal zones (MTZs). We evaluated the effect of FP on skin remodeling at 7 and 14 days after treatment. Corresponding histology was performed for comparison. After 14 days of FP treatment at 10 mJ, the second harmonic generation signal recovered faster than the skin treated with 30 mJ, indicating a more rapid regeneration of dermal collagen at 10 mJ. Our results indicate that nonlinear optical microscopy is effective in detecting the damaged areas of MTZ and monitoring collagen regeneration following FP treatment.
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