Efficient out-of-plane microphotonic fiber-to-chip coupler designs

Thesis (M. Eng. and S.B.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2006.Includes bibliographical references (p. 59).Due to the tremendous increase of data rates in optical communication, and as a result the forthcoming reliance on photonic circuits for all-optical switching, routing and signal processing, efficient coupling of light between a nanophotonic waveguide and a fiber has become a critical and interesting issue to investigate. The objective of this thesis is to explore new strategies for efficient fiber-to-chip coupler design and to come up with design rules based on these strategies and a competent device design. Some of the previous research in the area of coupler design is reviewed, and a novel out-of-plane fiber-to-chip coupler design that is based on phase-canceling gratings is proposed. The principle of operation of this grating is explained and may be applied to other grating designs.by Mingyan Fan.M.Eng.and S.B

Realistic Noise Synthesis with Diffusion Models

Deep learning-based approaches have achieved remarkable performance in single-image denoising. However, training denoising models typically requires a large amount of data, which can be difficult to obtain in real-world scenarios. Furthermore, synthetic noise used in the past has often produced significant differences compared to real-world noise due to the complexity of the latter and the poor modeling ability of noise distributions of Generative Adversarial Network (GAN) models, resulting in residual noise and artifacts within denoising models. To address these challenges, we propose a novel method for synthesizing realistic noise using diffusion models. This approach enables us to generate large amounts of high-quality data for training denoising models by controlling camera settings to simulate different environmental conditions and employing guided multi-scale content information to ensure that our method is more capable of generating real noise with multi-frequency spatial correlations. In particular, we design an inversion mechanism for the setting, which extends our method to more public datasets without setting information. Based on the noise dataset we synthesized, we have conducted sufficient experiments on multiple benchmarks, and experimental results demonstrate that our method outperforms state-of-the-art methods on multiple benchmarks and metrics, demonstrating its effectiveness in synthesizing realistic noise for training denoising models

High Directivity, Vertical Fiber-to-Chip Coupler with Anisotropically Radiating Grating Teeth

Abstract: Efficient vertical grating-coupler designs are proposed that allow near 50:1 up/down directivity using only two lithographic layers, without top/bottom mirrors, in high-index-contrast silicon waveguides. FDTD simulations predict single-mode-fiber-coupling efficiencies of 75% even for non-apodized gratings. The concept of using periodic structures such as gratings to couple out-of-plane light into waveguides has seen a revived interest recently for high index-contrast (HIC) microphotonics due to the strong HIC scattering that enables all input light to be coupled out vertically over a 10μm grating length, which is close to the mode field diameter of standard single-mode fiber, a necessary condition for efficient coupling to it We propose in this paper an out-of-plane fiber-to-chip coupler design with a high out-of-plane directivity (preference for upward radiation over downward radiation), achieved by engineering of the tooth shape, through a minimum of lithographic layers (two), and without any need for top or bottom reflector layers required by previous designs By modeling each sub-tooth as a point scatterer, Δθ upward is defined as the phase difference between radiation scattered upward by the both sub-teeth and Δθ downward is that for radiation scattered downward, then Δθ upward = θ v -θ h and Δθ downward = θ v + θ h (se

Effect of extract from ginseng rust rot on the inhibition of human hepatocellular carcinoma cells in vitro

Hepatocellular carcinoma (HCC) is one of major leading causes of cancer death worldwide. As a traditional medicine, the anti-cancer function of ginseng is being growingly recognized and investigated. However, the effect of ginseng rust rot on human HCC is unknown yet. In this study, the HCC cells were treated with different parts of mountain cultivated ginseng rust rot and compared with human normal liver cells. The morphology, survival rate and β-actin expression of the cells were changed by introducing the ginseng epidermis during the incubation process. Notably, the results reveal that the ginseng epidermis can induce apoptosis by altering the morphologies of cells, indicating the practical implication for the HCC treatment and drug development

Application of 18F-FDG PET/CT imaging in gallbladder inflammatory pseudotumor with elevated CA199: a case report and review of literature

BackgroundGallbladder inflammatory pseudotumor (GIPT) is a nonspecific chronic proliferative inflammation of the gallbladder. At present, the pathogenesis is not clear, which may be related to bacterial and viral infections, congenital diseases, gallstones, chronic cholangitis and so on. GIPT is rare and the imaging examination has no obvious specificity. There are few reports on the 18F-FDG PET/CT imaging characteristics of GIPT. In this paper, 18F-FDG PET/CT findings of GIPT with elevated CA199 are reported and the literature is reviewed.Case descriptionA 69-year-old female patient presented with recurrent intermittent right upper abdominal pain for more than 1 year, followed by nausea and vomiting for 3 hours, without fever, dizziness, chest tightness and other symptoms. Complete CT, MRI, PET/CT and related laboratory tests, CEA (-), AFP (-), Ca199 224.50U/mL ↑,18F-FDG PET/CT images showed uneven thickening at the bottom of the gallbladder, slightly increased gallbladder volume, eccentric and localized thickening of the gallbladder body wall, nodular soft tissue density shadow, clear boundary, smooth gallbladder wall, presence and smooth hepatobiliary interface, increased FDG radioactivity uptake, SUVmax was 10.2.The tumor was resected after operation and was diagnosed as gallbladder inflammatory pseudotumor by postoperative pathology.Conclusion18F-FDGPET/CT imaging has a certain significance for gallbladder inflammatory pseudotumor. In patients with chronic cholecystitis, when the CA199 increases, the gallbladder wall appears localized thickening, the hepatobiliary interface exists and is smooth, and the 18F-FDG metabolism is mildly to moderately increase. Gallbladder cancer cannot be diagnosed alone, and the possibility of gallbladder inflammatory pseudotumor should also be considered. However, it should be noted that the cases with unclear diagnosis should still be actively treated with surgery, so as not to delay the treatment opportunity

Cardioprotective Effects of Salvianolic Acid A on Myocardial Ischemia-Reperfusion Injury In Vivo and In Vitro

Salvianolic acid A (SAA), one of the major active components of Danshen that is a traditional Chinese medicine, has been reported to possess protective effect in cardiac diseases and antioxidative activity. This study aims to investigate the cardioprotection of SAA in vivo and in vitro using the model of myocardial ischemia-reperfusion in rat and hydrogen peroxide (H2O2)-induced H9c2 rat cardiomyoblasts apoptosis. It was found that SAA significantly limited infarct size of ischemic myocardium when given immediately prior to reperfusion. SAA also significantly suppressed cellular injury and apoptotic cell death. Additionally, the results of western blot and phospho-specific antibody microarray analysis showed that SAA could up-regulate Bcl-2 expression and increase the phosphorylation of proteins such as Akt, p42/p44 extracellular signal-related kinases (Erk1/2), and their related effectors. The phosphorylation of those points was related to suppress apoptosis. In summary, SAA possesses marked protective effect on myocardial ischemia-reperfusion injury, which is related to its ability to reduce myocardial cell apoptosis and damage induced by oxidative stress. The protection is achieved via up-regulation of Bcl-2 expression and affecting protein phosphorylation. These findings indicate that SAA may be of value in cardioprotection during myocardial ischemia-reperfusion injury, which provide pharmacological evidence for clinical application