In-situ monitoring of refractive index change during water-ice phase transition with a multiresonant fiber grating.

In-situ monitoring of refractive index changes during a liquid-solid phase transition is achieved by measurement of the transmission spectrum from a single tilted fiber Bragg grating immersed in water. Differential wavelength shifts of multiple mode resonances are used to eliminate cross-talk from temperature, throughout the phase transition, and from strains occurring after solidification. The measured sudden shift of refractive index at the phase transition is shown to be consistent with the expected difference from water to ice, in spite of the observed onset of compressive strain on the fiber by the frozen water. Beyond the obvious application to research on the dynamics of liquid-solid phase transitions, this work demonstrates the multiparameter measurement capabilities of multiresonant gratings.

Vernier effect of two cascaded in-fiber Mach-Zehnder interferometers based on a spherical-shaped structure.

The Vernier effect of two cascaded in-fiber Mach-Zehnder interferometers (MZIs) based on a spherical-shaped structure has been investigated. The envelope based on the Vernier effect is actually formed by a frequency component of the superimposed spectrum, and the frequency value is determined by the subtraction between the optical path differences of two cascaded MZIs. A method based on band-pass filtering is put forward to extract the envelope efficiently; strain and curvature measurements are carried out to verify the validity of the method. The results show that the strain and curvature sensitivities are enhanced to -8.47 pm/µÎµ and -33.70 nm/m-1 with magnification factors of 5.4 and -5.4, respectively. The detection limit of the sensors with the Vernier effect is also discussed.

Sagnac interferometer hydrogen sensor based on panda fiber with Pt-loaded WO3/SiO2 coating.

A highly sensitive optical fiber Sagnac interferometer hydrogen sensor is proposed and demonstrated. The device is fabricated by inserting a segment of panda fiber coated with Pt-loaded WO3/SiO2 into a Sagnac interferometer loop. When Pt/WO3 film is exposed to hydrogen, the exothermic reaction raises the temperature of the panda fiber, resulting in the resonant wavelength shift of the interferometer, and the resonant dip obtained has a large extinction ratio of ∼25 dB and a narrow linewidth of 2.5 nm. Such a device responds fast to hydrogen, exhibits a high sensitivity of -7.877 nm/% (vol. %) within the range of 0%-1.0% and is robust, low cost, and easy to fabricate.

Recent Progress in the Application of Metal Organic Frameworks in Surface-Enhanced Raman Scattering Detection.

Metal-organic framework (MOF) compounds are centered on metal ions or metal ion clusters, forming lattices with a highly ordered periodic porous network structure by connecting organic ligands. As MOFs have the advantages of high porosity, large specific surface area, controllable pore size, etc., they are widely used in gas storage, catalysis, adsorption, separation and other fields. SERS substrate based on MOFs can not only improve the sensitivity of SERS analysis but also solve the problem of easy aggregation of substrate nanoparticles. By combining MOFs with SERS, SERS performance is further improved, and tremendous research progress has been made in recent years. In this review, three methods of preparing MOF-based SERS substrates are introduced, and the latest applications of MOF-based SERS substrates in biosensors, the environment, gases and medical treatments are discussed. Finally, the current status and prospects of MOF-based SERS analysis are summarized.

miR-29 regulates metabolism by inhibiting JNK-1 expression in non-obese patients with type 2 diabetes mellitus and NAFLD.

Previous studies have shown that microRNAs (miRNAs) are involved in the regulation of a variety of metabolic diseases, which related to some important signal pathways. Our aim was to explore the possible mechanism of miRNAs by revealing the differential expression of serum miRNAs in different BMI of type 2 diabetes mellitus (T2DM) patients with non-alcoholic fatty liver disease (NAFLD). We found that miR-29 decreased liver aminotransferase gamma-GGT and uric acid levels by inhibiting the expression of JNK-1 in non-obese T2DM patients with NAFLD, and down-regulated the expression of atherosclerosis-related factor lipoprotein phospholipase A2 (Lp-PLA2). Combined with bioinformatics analysis, we speculate that this may be mediated by the AMPK signaling. These findings suggest that miR-29 may be a potential targeted therapeutic strategy in T2DM patients with NAFLD.

Polarization-dependent curvature sensor based on an in-fiber Mach-Zehnder interferometer with a difference arithmetic demodulation method.

A curvature sensor based on a polarization-dependent in-fiber Mach-Zehnder interferometer (MZI) is proposed. The MZI is fabricated by core-offset fusion splicing one section of polarization maintaining fiber (PMF) between two single mode fibers (SMFs). Two independent interference patterns corresponding to the two orthogonal polarization modes for the PMF are obtained. The couple efficiency between the core mode and the cladding mode decreased with the increasing of the bending on the MZI part. The curvature variation on the MZI part can be obtained by detecting the fringe visibility of the interference patterns. A difference arithmetic demodulation method is used to reduce the effects of the light source power fluctuations and temperature cross-sensitivity. Experimental results show that maximal sensitivity of -0.882 dB/m(-1) is obtained under a measurement range of 0.1 to 0.35 m(-1) for the curvature sensor. With the use of difference arithmetic demodulation method, the temperature-curvature cross-sensitivity and light source power fluctuations effects on the proposed sensor are decreased by 94% and 91%, respectively.

Data driven identification of international cutting edge science and technologies using SpaCy.

Difficulties in collecting, processing, and identifying massive data have slowed research on cutting-edge science and technology hotspots. Promoting these technologies will not be successful without an effective data-driven method to identify cutting-edge technologies. This paper proposes a data-driven model for identifying global cutting-edge science technologies based on SpaCy. In this model, we collected data released by 17 well-known American technology media websites from July 2019 to July 2020 using web crawling with Python. We combine graph-based neural network learning with active learning as the research method in this paper. Next, we introduced a ten-fold cross-check to train the model through machine learning with repeated experiments. The experimental results show that this model performed very well in entity recognition tasks with an F value of 98.11%. The model provides an information source for cutting-edge technology identification. It can promote innovations in cutting-edge technologies through its effective identification and tracking and explore more efficient scientific and technological research work modes.

Competitive adsorption of residual polyvinylpyrrolidone and detection molecular on flower liked silver nanoparticles.

The silver nanoparticles have been frequently used in SERS detection, for their unique optical properties and sensitive surface Raman enhancement properties. However, as the preparation of silver nanoparticles will use polyvinylpyrrolidone (PVP) to achieve the effect of reducing agent and surfactant, the surface of the prepared silver nanoparticles will be wrapped by PVP, forming an insulating layer and an ill-defined AgNPs interface, which limits the plasmonic coupling between the laminates of AgNPs. This paper reported a simple method to remove PVP for high performance and reusable SERS substrate, and the residue of PVP was studied after clean centrifugal by ethanol or water. When the number of cleaning times reached 10, there was basically no residual of PVP. The cleaned AgNPs interface effectively enhanced the plasma resonance of the local surface (LSPR) and greatly improved the SERS activity of the substrate. Moreover, probe molecules (R6G) are introduced to study the influence of single molecule PVP on subsequent detection. Through the competitive relationship between the two, it can be concluded that residual PVP has basically no influence on detection of the molecular which absorbed stronger than PVP, and the remaining PVP can be ignored.

Miniature refractometer based on modal interference in a hollow-core photonic crystal fiber with collapsed splicing.

A miniature modal interferometer based on a hollow-core photonic crystal fiber (HC-PCF) for refractive index measurement is demonstrated. The modal interferometer is fabricated by splicing the two ends of a 1.2-mm-long HC-PCF to a single-mode fiber (SMF). The air holes of the HC-PCF are fully collapsed by the discharge arc during the splicing procedure, and the length of each collapsed region is about 300 µm. The transmission spectra with different refractive indices outside the HC-PCF are measured. Measurement resolutions of an 8.1×10(-4) refractive index unit (RIU) in the range of 1.35 to 1.39, and 4.3×10(-4) RIU in the range of 1.39 to 1.43 are achieved, respectively. The temperature effect of the proposed refractometer is also analyzed.