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In this paper, an all-fiber Mach-Zehnder interferometer (MZI) sensor for refractive index (RI) measuring is presented, which is based on Multimode–Single-mode–Multimode (MSM) fiber. The effects of both reducing the radius of the sensing part and the surface plasmon resonance (SPR) on its efficiency are investigated. Increasing the interaction of high-order modes with external media, caused by etching the cladding layer of the single-mode fiber part, significantly improves the sensitivity. Both wavelength and intensity interrogation approaches are employed to study the Multimode–etched Single-mode–Multimode (MESM) fiber sensor. The intensity and the wavelength sensitivities for the RI measurement in the range of 1.428-1.458 are obtained as -2308.92 %/RIU and 1313.14 nm/RIU, respectively. Finally, the MESM-SPR sensor is proposed and characterized. Results exhibit high performance in the RI range of 1.333 to 1.357, in which the sensitivity of 1433 nm/RIU is achieved. The advantages like low cost, high sensitivity, and simple fabrication methods make these sensors promising devices for chemical, food industry, and biosensing applications.

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Background: Papillary thyroid carcinoma (PTC) is the most prevalent endocrine malignancy. Despite nearly three-fold increase in incidence over three decades, the mortality rate remains unchanged. Biomarkers related to early diagnosis and prognosis of PTC are poorly investigated. Autophagy pathways and related miRNAs is considered to play an important role in PTC pathophysiology.Methods and Results: Tissue samples from patients with PTC undergoing thyroidectomy were collected. Total RNA content of tumor and margin samples were purified and converted to cDNA. Gene expression levels of mRNA (FOXO1) and miRNAs (miR-30d-5p, miR- 182-5p and miR-183-5p) were evaluated using qPCR method in PTC and adjacent normal tissue. A 6.51-fold decrease in miR-30d-5p level was detected in tumor samples compared to adjacent tissues. Moreover, miR-182-5p and miR-183-5p (FOXO1 as the main target) showed 1.73- and 4.31-fold increases in their levels, respectively. We also observed a 2.66-fold decrease in FOXO1 mRNA level in relation to these miRNA fold changes indicating a possible correlation between autophagy-linked molecular events and PTC.Conclusions: Significant increase in miR-183-5p and miR-182-5p expression, as well as a decrease in FOXO1 and miR-30d-5p expression, suggest that PTC has active autophagy machinery. This can possibly be used as a novel diagnostic or prognostic biomarker.