All-solid highly sensitive fiber-tip magnetic field sensor based on a Fabry-Perot interferometer with a breakpoint structure.

An all-solid fiber-tip Fabry-Perot interferometer (FPI) coated with a nickel film is proposed and experimentally verified for magnetic field sensing with high sensitivity. It is fabricated by splicing a segment of a thin-wall capillary tube to a standard single-mode fiber (SMF), then inserting a tiny segment of fiber with a smaller diameter into the capillary tube, and creating an ultra-narrow air-gap at the SMF end to form an FPI. When the device is exposed to magnetic field, the capillary tube is strained due to the magnetostrictive effect of the nickel film coated on its outer surface. In addition, owing to the unique breakpoint sensitivity-enhancement structure of the air-gap FPI, the elongation of the capillary tube whose length is over 100 times longer than the air-gap width is entirely transferred to the cavity length change of the FPI, and the sensor is extremely sensitive to the magnetic field as proved by our experiments, achieving a high sensitivity of up to 2.236 nm/mT for a linear magnetic field range from 40 to 60 mT, as well as a low-temperature cross-sensitivity of 56 µT/°C. The all-solid stable structure, compact size (total length of ∼3.0 mm), and reflective working mode with high magnetic field sensitivity indicate that this sensor has good application prospects.

Speckle wavemeter based on a multi-core fiber and compressive imaging.

Random speckle patterns contain valuable information about the incident light. Researchers have successfully constructed spectrometers and wavemeters by utilizing the speckles generated by inter-mode interferences of a multimode fiber (MMF). However, cameras were often employed to record the speckle data in previous reports. The camera's high cost (especially in the near-infrared range), large size, and low response speed limit the applications in optical communications, metrology, and optical sensing. A seven-core fiber (SCF) was fused with an MMF to capture the speckle pattern, where each core coupled part of the speckle field. Furthermore, we take advantage of the space division multiplexing capability of the SCF by incorporating an optical switch. This allows the variety of speckles generated by the incidence of different cores into the MMF. A convolutional neural network (CNN) regression algorithm was designed to analyze the complicated speckle data. The experimental results show that the proposed wavemeter can resolve adjacent wavelengths of 1 pm with an error of about 0.2 pm. We also discussed how different lengths of MMF influence the wavelength resolution. In conclusion, our research presents a robust and cost-effective approach to a wavelength measurement device by use of a seven-core optical fiber.

New triterpenoids from the aerial parts of the Uygur medicine Salvia deserta.

Phytochemical investigation on the aerial parts of Salvia deserta led to the isolation of eight new pentacyclic triterpenoids including three oleanane- (1 - 3) and five ursane-type (4 - 8) triterpenoids, whose structures were elucidated based on extensive spectroscopic analysis and quantum chemical calculation. Weak immunosuppressive potency was observed for compounds 1, 2, and 4 - 8 via inhibiting the secretion of cytokines TNF-α and IL-6 in LPS-induced macrophages RAW264.7 at 20 µM. In addition, compounds 1, 2, and 4 - 6 exhibited moderate protective activity on t-BHP-induced oxidative injury in HepG2 cells.

Function and autophagy of monocyte-derived dendritic cells is affected by hepatitis B virus infection.

BACKGROUND: The role of dendritic cells and the autophagy state of dendritic cells in the immune response of hepatitis B virus (HBV) infection was still controversial. In this study, we carefully examined the phenotype, function and autophagy pathway of dendritic cells in HBV infection. METHODS: Monocyte-derived dendritic cells from healthy blood donors and patients with chronic HBV infection were stimulated by lipopolysaccharide, supernatant of HepG2.2.15 cells or supernatant of HepG2 cells respectively. Phenotype of dendritic cells was examined by flow cytometry and cytokines secretion was detected by enzyme-linked immunosorbent assay. Autophagy related proteins were detected by western blot and immunofluorescence analysis. RESULTS: Our results showed that the expression of both major histocompatibility complex II molecules and co-stimulated molecules including cluster of differentiation antigen 80, cluster of differentiation antigen 86 in the monocyte-derived dendritic cells from patients with chronic HBV infection was significantly higher than that from healthy donors when cultured with supernatant of HepG2.2.15 cells. The amount of cytokines, including tumour necrosis factor-α, interleukin-10 and interleukin-12, secreted by monocyte-derived dendritic cells from patients with chronic HBV infection was also significantly higher than that from healthy donors when stimulate by HBV. Interestingly, the expression level of autophagy-related proteins including autophagy-related protein5 and associated protein 1 light chain in dendritic cells from patients with chronic HBV infection was significantly increased when compared with that from healthy donors when re-exposed to HBV. CONCLUSIONS: Our results indicated that dendritic cells from patients with chronic HBV infection could intensively present antigen and express co-stimulatory molecules. The increased activation of dendritic cells might be related to the enhanced autophagy of dendritic cells in HBV infection.

Use of metagenomic next-generation sequencing for diagnosis of peritonitis in end-stage liver disease.

Background: Conventional methods are low in positive rates and time-consuming for ascites pathogen detection in patients with end-stage liver disease (ESLD). With many advantages, metagenomic next-generation sequencing (mNGS) may be a good alternative method. However, the related studies are still lacking. Methods: Ascites from 50 ESLD patients were sampled for pathogen detection using mNGS and conventional methods (culture and polymorphonuclear neutrophils detection) in this prospective observational study. Results: Forty-two samples were detected positive using mNGS. 29 strains of bacteria, 11 strains of fungi, and 9 strains of viruses were detected. 46% of patients were detected to be co-infected with 2 or more pathogens by mNGS. Moreover, mNGS showed similar and high positive rates in ESLD patients with different clinical characteristics. Compared to conventional methods, mNGS had higher positivity rates (84% vs. 20%, P<0.001), sensitivity (45.2% vs. 23.8%, P=0.039), broader pathogen spectrum, shorter detection time (24 hours vs. 3-7 days), but lower specificity (25% vs 100%, P = 0.010). Furthermore, compared to conventional methods, mNGS showed similar consistence with final diagnosis (42% vs. 36%, P=0.539). Conclusions: mNGS may be a good supplement for conventional methods and helpful to early etiological diagnosis of peritonitis, and thus improve ESLD patients' survival.

Demodulation of Fabry-Perot sensors using random speckles.

Random speckles are proposed to demodulate Fabry-Perot (FP) sensors in this study. A piece of multimode fiber is used to interrogate the FP transmission spectrum, and tiny spectral changes lead to significant variations in the generated speckle patterns. In the demonstration experiments, the pressure resolution of 0.001 MPa can be obtained from an open cavity FP sensor based on the convolutional neural network (CNN) demodulation algorithm. It is worth noting that the spectral differences in neighboring orders can be precisely distinguished due to the high sensitivity of speckles. Thus, the fringe-order ambiguity problem is solved and the dynamic measurement range can be greatly improved. The speckle-based demodulation scheme provides a new way to balance resolution, dynamic range, speed, and cost of FP sensors.

Safety and antibody response to inactivated COVID-19 vaccine in patients with chronic hepatitis B virus infection.

BACKGROUND AND AIMS: The safety and antibody responses of coronavirus disease 2019 (COVID-19) vaccination in patients with chronic hepatitis B (CHB) virus infection is still unclear, and exploration in safety and antibody responses of COVID-19 vaccination in CHB patients is significant in clinical practice. METHODS: 362 adult CHB patients and 87 healthy controls at an interval of at least 21 days after a full-course vaccination (21-105 days) were enrolled. Adverse events (AEs) were collected by questionnaire. The antibody profiles at 1, 2 and 3 months were elucidated by determination of anti-spike IgG, anti-receptor-binding domain (RBD) IgG, and RBD-angiotensin-converting enzyme 2 blocking antibody. SARS-CoV-2 specific B cells were also analysed. RESULTS: All AEs were mild and self-limiting, and the incidence was similar between CHB patients and controls. Seropositivity rates of three antibodies were similar between CHB patients and healthy controls at 1, 2 and 3 months, but CHB patients had lower titers of three antibodies at 1 month. Compared to healthy controls, HBeAg-positive CHB patients had higher titers of three antibodies at 3 months (all P < .05) and a slower decline in antibody titers. Frequency of RBD-specific B cells was positively correlated with titers of anti-RBD IgG (OR = 1.067, P = .004), while liver cirrhosis, antiviral treatment, levels of HBV DNA, alanine aminotransferase (ALT) and aspartate aminotransferase (AST) and total bilirubin (TB) were not correlated with titers of anti-RBD IgG. CONCLUSIONS: Inactivated COVID-19 vaccines were well tolerated, and induced effective antibody response against SARS-CoV-2 in CHB patients.

Gastroscopic results for the asymptomatic, average-risk population in Northern China: a cross-sectional study of 60,519 adults.

BACKGROUND: Studies on average-risk individuals undergoing gastroscopy screening in China are scarce. OBJECTIVE: To determine and compare the prevalence of lesions found by gastroscopy and the association between sex, age, Helicobacter pylori infection and gastric premalignant lesions. METHODS: Gastroscopy results were analysed for 60,519 individuals enrolled from January 2013 to December 2019. RESULTS: The median age was 49.84 years (SD, 9.47 years) for women and 48.90 years (SD, 8.82 years) for men, and the ratio of females to males was 35.10% (n = 21,240) to 64.90% (n = 39,279). The most common lesions detected by endoscopy were chronic gastritis, reflux oesophagitis, duodenitis and gastric polyps, detected in 24.48%, 10.28%, 3.96% and 3.61%, respectively. Oesophageal cancer and gastric cancer were detected in 0.33% and 0.47% of patients, respectively. The prevalence of chronic gastritis increased with age and was higher in males than in females (26.47% [n = 10396] versus 20.80% [n = 4417], p < .001). The prevalence of gastric ulcers was highest in the elderly group, and the H. pylori infection rate of gastric ulcer patients was 47.28%. The prevalence of gastric polyps was higher in females than in males (5.47% [n = 1161] versus 2.61% [n = 1024], p < .001), and the H. pylori infection rate in inflammatory polyp patients was higher than that in fundic gland polyp patients (28.32% [n = 442] versus 7.29% [n = 29], p < .001). CONCLUSION: The prevalence of upper gastrointestinal endoscopic lesions is high in the asymptomatic population undergoing physical examination and is associated with sex, age, and H. pylori infection.

[The clinical value of von Willebrand factor and VITRO score in evaluating disease progression in patients with HBV infection].

Objective: To explore the clinical value of von Willebrand Factor (vWF) and VITRO score (vWF:Ag/platelet count) in assessing disease progression in patients with HBV infection. Methods: Randomly collect relevant clinical data of 308 patients with HBV infection (including 154 cases of chronic hepatitis B, 66 cases of hepatitis B cirrhosis in compensatory period, 88 cases of hepatitis B cirrhosis in decompensated period) from December 1, 2018 to January 5, 2021 in the Second Affiliated Hospital of Chongqing Medical University. The vWF values are measured by a uniform optical method, and all data are included using a uniform standard. Analyze the difference and significance of plasma vWF level and VITRO score in chronic hepatitis B, hepatitis B cirrhosis in the compensatory phase and decompensated phase. Results: The plasma vWF level and VITRO score of the chronic hepatitis B group were (139.47±76.44) and (0.86±0.8), respectively, and the hepatitis B cirrhosis compensated group was (164.95±67.12 and 1.44±1.14), respectively. Hepatitis cirrhosis decompensated group were (317.48±103.32 and 6.81±4.98), respectively; plasma vWF level and VITRO score increased with the progression of HBV infection, and the difference was statistically significant (F=133.669,P=0.000F=137.598,P=0.000).The plasma vWF level and VITRO score in patients with hepatitis B cirrhosis were (185.65±85.07 and 2.3±2.37) in the Child-Pugh A group, (304.74±105.81 and 6.37±5.19) in the B grade group, and (369.48±73.238.28±5.38) in the C grade group; plasma vWF level and VITRO score in patients with hepatitis B cirrhosis increased with the increase of Child-Pugh grade, and the difference was statistically significant (F=60.236, P=0.000F=32.854, P=0.000). The area under the curve (AUC) of plasma vWF level and VITRO score for diagnosing the decompensated stage of hepatitis B cirrhosis were 0.897 [95% confidence interval (CI): 0.855-0.940, P＜0.01], 0.949 [95% CI: 0.916-0.982, P＜0.01). When the vWF level and VITRO score were taken as cut-off values of 238.5% and 1.65, respectively, the sensitivity of diagnosing the decompensated stage of hepatitis B cirrhosis was 79.5% and 94.3%, the specificity was 92.3% and 87.7%, and the positive predictive value was 80.5% and 94.3%, the negative predictive value was 91.9% and 97.5%, and the diagnostic accuracy was 88.6% and 89.3%. Among the patients with decompensated hepatitis B cirrhosis, the level of vWF in the group with gastrointestinal bleeding (367.24±68.29)% was significantly higher than that in the group without gastrointestinal bleeding (286.15±109.69)%, and the difference was statistically significant (P＜0.001) The VITRO score of the group with gastrointestinal bleeding (9.12±5.4) was significantly higher than that of the group without gastrointestinal bleeding (5.36±4.13), and the difference was statistically significant (P＜0.01). The vWF level in the spontaneous peritonitis group was (341.73±87.92)% higher than that in the non-spontaneous peritonitis group (296.32±111.74)%, and the difference was statistically significant (P＜0.05). There was no statistical difference in VITRO score between the two groups. significance. Conclusion: Plasma vWF level and VITRO score can evaluate the progression of liver disease and the degree of decompensation of liver cirrhosis in patients with HBV infection, and have a predictive effect on various complications after decompensation of liver cirrhosis, and have certain guiding significance for early intervention measures.

Deep-learning-assisted fiber Bragg grating interrogation by random speckles.

Fiber Bragg gratings (FBGs) have been widely employed as a sensor for temperature, vibration, strain, etc. measurements. However, extant methods for FBG interrogation still face challenges in the aspects of sensitivity, measurement speed, and cost. In this Letter, we introduced random speckles as the FBG's reflection spectrum information carrier for demodulation. Instead of the commonly used InGaAs cameras, a quadrant detector (QD) was first utilized to record the speckle patterns in the experiments. Although the speckle images were severely compressed into four channel signals by the QD, the spectral features of the FBGs can still be precisely extracted with the assistance of a deep convolution neural network (CNN). The temperature and vibration experiments were demonstrated with a resolution of 1.2 pm. These results show that the new, to the best of our knowledge, speckle-based demodulation scheme can satisfy the requirements of both high-resolution and high-speed measurements, which should pave a new way for the optical fiber sensors.

Variable-fiber optical power splitter design based on a triangular prism.

Fiber optical power splitters (OPSs) have been widely employed in optical communications, optical sensors, optical measurements, and optical fiber lasers. It has been found that OPSs with variable power ratios can simplify the structure and increase the flexibility of optical systems. In this study, a variable-fiber OPS based on a triangular prism is proposed and demonstrated. By adjusting the output beam width of the prism, the power ratio can be continuously tuned. The optical simulations show that the horizontal displacement design is better than the traditional tilt angle design. Our scheme combines a dual-fiber collimator, a focus lens, and a triangular prism with a vertex angle of 120°. By changing the axial displacement of the prism, the power splitting ratio can be altered from 50:50 to 90:10. The polarization and wavelength dependence of the variable OPS were also investigated.

Identification of microRNAs in developing wheat grain that are potentially involved in regulating grain characteristics and the response to nitrogen levels.

BACKGROUND: MicroRNAs (miRNAs) play crucial roles in the regulation of plant development and growth, but little information is available concerning their roles during grain development under different nitrogen (N) application levels. Our objective was to identify miRNAs related to the regulation of grain characteristics and the response to different N fertilizer conditions. RESULTS: A total of 79 miRNAs (46 known and 33 novel miRNAs) were identified that showed significant differential expression during grain development under both high nitrogen (HN) and low nitrogen (LN) treatments. The miRNAs that were significantly upregulated early in grain development target genes involved mainly in cell differentiation, auxin-activated signaling, and transcription, which may be associated with grain size; miRNAs abundant in the middle and later stages target genes mainly involved in carbohydrate and nitrogen metabolism, transport, and kinase activity and may be associated with grain filling. Additionally, we identified 50 miRNAs (22 known and 28 novel miRNAs), of which 11, 9, and 39 were differentially expressed between the HN and LN libraries at 7, 17, and 27 days after anthesis (DAA). The miRNAs that were differentially expressed in response to nitrogen conditions target genes involved mainly in carbohydrate and nitrogen metabolism, the defense response, and transport as well as genes that encode ubiquitin ligase. Only one novel miRNA (PC-5p-2614_215) was significantly upregulated in response to LN treatment at all three stages, and 21 miRNAs showed significant differential expression between HN and LN conditions only at 27 DAA. We therefore propose a model for target gene regulation by miRNAs during grain development with N-responsive patterns. CONCLUSIONS: The potential targets of the identified miRNAs are related to various biological processes, such as carbohydrate/nitrogen metabolism, transcription, cellular differentiation, transport, and defense. Our results indicate that miRNA-mediated networks, via posttranscriptional regulation, play crucial roles in grain development and the N response, which determine wheat grain weight and quality. Our study provides useful information for future research of regulatory mechanisms that focus on improving grain yield and quality.

Application of calibration-free high repetition rate laser-ablation spark-induced breakdown spectroscopy for the quantitative elemental analysis of a silver alloy.

In this work, we report the application of a calibration-free (CF) method combined with high repetition rate laser-ablation spark-induced breakdown spectroscopy (HRR LA-SIBS) to the analysis of a silver alloy. The sample was ablated by a fiber laser operated at a 30 kHz pulse repetition rate, and a spark discharge was applied to enhance plasma emission. Electron number density and plasma temperature were estimated using Stark broadening of spectral lines and the Saha-Boltzmann plot method, respectively. The fulfillment of the local thermodynamic equilibrium (LTE) approximation of the measurement was verified. Averaged electron density and plasma temperature were calculated as 1.11×1017cm-3 and 7355 K, respectively. The elemental composition of a silver alloy sample was determined, and the result was compared with that analyzed with inductively coupled plasma optical emission spectrometry (ICP-OES). The analytical error was within a 15% range. It was demonstrated that the CF HRR LA-SIBS technique could potentially provide elemental analysis for silver alloys without requiring a standard sample.

2,3,5,4'-Tetrahydroxystilbene-2-O-ß-D-Glucoside Attenuates Ischemia/Reperfusion-Induced Brain Injury in Rats by Promoting Angiogenesis.

Cerebral ischemia can cause brain infarcts, which are difficult to recover due to poor angiogenesis. 2,3,5,4'-Tetrahydroxystilbene-2-O-ß-D-glucoside is a natural polyphenol, has antioxidant and anti-inflammatory activity, and can protect from ischemic neuronal injury. However, little is known about the effect of 2,3,5,4'-tetrahydroxystilbene-2-O-ß-D-glucoside on brain microcirculation after stroke. This study aimed at investigating the influence of 2,3,5,4'-tetrahydroxystilbene-2-O-ß-D-glucoside on brain lesions and angiogenesis after stroke. Sprague-Dawley rats were subjected to right middle cerebral artery occlusion and treated with vehicle, nimodipine, or different doses of 2,3,5,4'-tetrahydroxystilbene-2-O-ß-D-glucoside daily beginning at 6 h post-middle cerebral artery occlusion for 14 days. The volume of cerebral infarcts, degree of neurological dysfunction, and level of microvessel density were determined longitudinally. The levels of vascular endothelial growth factor, angiopoietin 1, and angiopoietin receptor-2 expression in the brain lesions were characterized by immunohistochemistry and Western blot assays at 14 days post-middle cerebral artery occlusion. We found that 2,3,5,4'-tetrahydroxystilbene-2-O-ß-D-glucoside significantly promoted postoperative recovery in rats by minimizing the volume of cerebral infarcts and improving neurological dysfunction in a dose- and time-dependent manner. Additionally, 2,3,5,4'-tetrahydroxystilbene-2-O-ß-D-glucoside significantly increased the microvessel density in the brain and upregulated CD31 expression in ischemic penumbra, relative to that in the control. Finally, treatment with 2,3,5,4'-tetrahydroxystilbene-2-O-ß-D-glucoside significantly upregulated the relative levels of vascular endothelial growth factor, angiopoietin 1, and angiopoietin receptor-2 expression in the brain lesions of rats. Therefore, these data indicated that 2,3,5,4'-tetrahydroxystilbene-2-O-ß-D-glucoside treatment promoted angiogenesis and recovery from ischemia/reperfusion-induced brain injury in rats.

[The safety of telbivudine in preventing mother-to-infant transmission of hepatitis B virus in pregnant women after discontinuation].

OBJECTIVE: To determine the efficacy and safety of telbivudine for blocking intrauterine transmission of hepatitis B virus (HBV) in pregnant women with high-load HBV DNA. METHODS: Women in general good health and pragnant were enrolled for study between the ages of 20 to 40 year-old, with a diagnosis of HBV infection with high-load HBV DNA level (≥1*10(6) IU/ml). According to each participant's willingness, the women were divided into a telbivudine treatment group (82 women) and an untreated control group (75 women). The telbivudine treatment was initiated at gestation week 26 as oral dosing of 600 mg/d and continued until 1 month after the birth.Women in the control group had not gotten any antiviral drug treatment. All of the women delivered by cesarean section, and all of the neonates were administered the standard passive immunization therapy, which consisted of a hepatitis B immunoglobulin (200 IU) injection given within 12 hours of birth and an injection of hepatitis B vaccine (20 µg) at birth and at postnatal month 1 and 6. None of the mother's performed breastfeeding. RESULTS: The telbivudine-treated women showed a significant decrease in HBV DNA levels prior to delivery, as well as significantly decreased prenatal HBV DNA levels (>2 logl0). Efficiency of the telbivudine treatment was 100%. Immediately prior to delivery, 16 (19.5%) of the women in the telbivudine treatment group showed negative HBV DNA status, as opposed to the untreated control group in which no women showed negative status. The telbivudine treatment group had no case of maternal or fetal adverse reaction or of congenital malformation. CONCLUSION: Use of telbivudine antiviral therapy during late pregnancy in women with high-load HBV DNA can significantly reduce level of HBV DNA in maternal peripheral blood, block HBV intrauterine transmission, and provide good short-term efficacy, with good tolerability and safety.

Hollow fiber-based Fabry-Perot cavity for liquid surface tension measurement.

A Fabry-Perot (FP) cavity, formed by a single-mode fiber (SMF) fusion spliced with a section of hollow fiber, was proposed and experimentally used as a sensor for liquid surface tension measurement. Due to the FP cavity length changing with different liquids, the surface tension can be measured by monitoring the interference wavelength spacing. In our experiment, five kinds of liquids were measured, and the relationship between wavelength spacing and liquid surface tension was obtained. The experimental results show that the achieved sensitivity to liquid surface tension is 30.96 nm/(N/m), and the maximum error is 5.43%.

Reflective long-period fiber grating-based sensor with Sagnac fiber loop mirror for simultaneous measurement of refractive index and temperature.

In this paper, we propose a reflective long-period grating-based sensor with a Sagnac fiber loop mirror (SFLM) for simultaneous measurement of refractive index (RI) and temperature. By cascading the SFLM to the end of a long-period fiber grating (LPFG), the LPFG works as a reflection operation, which is convenient in some applications. Further, the SFLM and the LPFG have different sensitivities to RI and temperature. As a result, RI and temperature measurement can be simultaneously achieved by monitoring the wavelength shifts of the LPFG and the SFLM's dips in the reflection spectrum. Experimental results show that the temperature sensitivity can reach 1.533 nm/°C, and the RI sensitivity is from 16.864 nm/RIU (refractive index unit) to 113.142 nm/RIU when the RI range is from 1.333 to 1.430. The application for 40 km long-distance RI and temperature measurement shows that the sensor has potential application in long-distance sensing.

High-sensitivity temperature sensor based on a droplet-like fiber circle.

A low-cost yet high-sensitivity temperature fiber sensor is proposed and demonstrated in this paper. A single-mode fiber with coating is simply bent in a droplet-like circle with a radius of several millimeters. The strong bending induces mode interferences between the silica core mode and the excited modes propagating in the polymer coating. Many resonant dips were observed in the transmission spectra and are found to shift to a shorter wavelength with the increase of environmental temperature. Our linear fitting result of the experimental data shows that the proposed sensor presents high temperature sensitivity up to -3.102 nm/°C, which is even comparable with sensors based on selective liquid-filled photonic crystal fibers. Such high temperature sensitivity results from the large thermo-optical coefficient difference between the silica core and the polymer coating. The influence of a circle radius to the sensitivities is also discussed.

A hydrogel optical fibre sensor for rapid on-site ethanol determination.

Ethanol plays a critical role in the modern chemical industry, food production, and medical research. Given its wide applications, the detection of ethanol concentration is very necessary. In this paper, a fibre device for rapid ethanol detection is proposed. The sensing head was fabricated with multimode fibre. The hydrogel was photo-cured on the fibre tip from polyethylene glycol diacrylate (PEGDA). In the hydrogel, rhodamine 6G (R6G) was immobilized as the fluorescent indicator. The sensor was designed based on the swelling behaviour of the hydrogel in liquid. The transparency of the hydrogel was modulated by the component of the water-ethanol mixture, thus, the fluorescence intensity of R6G was monitored for the determination of ethanol. Within the range of 0-62.2 vol%, the detection limit (LOD) was 0.4 vol%. A detailed comparison with other detection methods showed that the proposed sensor has the advantages of being single-ended, low LOD, cost-effective, and easy to prepare. It has great potential for on-site ethanol detection applications.

Compact micro-displacement sensor with high sensitivity based on a long-period fiber grating with an air-cavity.

We proposed and experimentally demonstrated a compact micro-displacement sensor with high sensitivity based on a long-period fiber grating (LPG) with an air-cavity. The sensor head is obtained by composing an air-cavity with the ends of a LPG and a single mode fiber (SMF). The wavelength shift of the LPG has a linear relationship with the length of the air gap which agrees well with the theoretical analysis. The experimental results show that the sensitivity is ~0.22 nm/µm within the micro-displacement range of 0 to 140 µm.