Sensitivity Of Dip Research Articles

Optical fiber refractive index sensor based on SMF-TCF-NCF-SMF interference structure

A novel optical fiber refractive index (RI) and strain sensor based on the combination of single-mode fiber (SMF), thin-core fiber (TCF), and no-core fiber (NCF) was proposed. Due to the inter-mode interference caused by the mode mismatch, the sensor is sensitive to the RI of the environment but insensitive to temperature. The experimental results show that in the RI range of 1.3333–1.3794, the sensitivity of dip A (1543 nm) and dip B (1565 nm) are 101.9446 nm/RIU and 109.9009 nm/RIU, respectively. In the temperature range of 15–85 ℃, the maximum wavelength shifts are only -3.5 pm/℃ and -4.9 pm/℃ respecitvely for dip A and dip B, indicating that the sensor can eliminate the cross-sensitivity of temperature to the RI. The sensor was used to detect alcohol, sucrose, NaCl and glycerin solution with the same RI and there is no obvious dip shift of the interference spectra. This sensor has the advantages of high RI sensitivities, strong anti-temperature interference ability, compact structure and has the potential application in the health and security monitoring.

A new method to improve the sensitivity of nitrate concentration measurement in seawater based on dispersion turning point

The nitrate concentration is extremely low in seawater, which needs highly sensitive sensors to measure. In this paper, a new method to improve the sensitivity of nitrate concentration measurement in seawater based on dispersion turning point (DTP) theory is demonstrated using a microfiber mode interferometric sensor. The high sensitivity is achieved by the interference of HE11 mode and HE12 mode. Different parameters that influence DTP have been calculated theoretically, including positions of dips and diameters for obtaining DTP, the relationship between DTP and group effective refractive index difference, and the effects of refractive indexes of solutions on the DTP. Calculated results show that the sensitivity of dip will be ultra-high near the DTP and the ultra-high sensitivity region is very narrow in a certain band or a certain diameter. In the experiment, six sensors with different diameters are fabricated to realize the concentration of sodium nitrate sensing in seawater. By optimizing the parameters of sensor, the maximum sensitivity and detection limit of sodium nitrate in seawater can reach to be 5.98 pm/ppm (refractive index sensitivity is 50396.09 nm/RIU) and 0.17 ppm, respectively. The sensor demonstrated here shows advantages of easy to construct, low cost, high precision and high sensitivity, which provides a new optical detection method for in-situ detection of marine environment or low concentration substances sensing in other liquids.

Dual-wavelength terahertz sensing based on anisotropic Fano resonance metamaterials.

Higher order Fano resonance metamaterials provide a desirable platform for biosensing applications. In this work we exhibit higher order Fano modes by designing an elliptical metallic ring. The simulation results show that for Fano resonant metamaterials, the higher order modes lead to improved sensitivity to refractive index change and larger frequency shifts. Numerically, the sensitivity of dip A (quadrupole mode) is 112GHz/RIU, whereas the sensitivity of dip B (octupole mode) is 234GHz/RIU, over 2 times that of dip A. According to our experimental results, the Fano resonant frequencies of dip A and dip B exhibit redshift as the concentration of the anti-cancer drug methotrexate decreases from 120 to 90μM, with the cell analyte concentration of A549 cells at 5×105 cell/ml. For dip A (quadrupole mode), there is a frequency shift of 0.84GHz for drug concentration of 120μM and a frequency shift of 22GHz for a 90μM drug-treated sample. For dip B (octupole mode), there is a frequency shift of 6.767GHz for the drug concentration of 120μM treated sample and a frequency shift of 51.815GHz for the drug concentration of 90μM treated sample. Furthermore, the frequency shift of dip A is always smaller than that of dip B for both 90μM and 120μM drug concentrations. Such phenomena indicate that dip B is much more sensitive than dip A. The enhanced sensitivity of higher order Fano metamaterials makes it possible to realize high-performance terahertz sensing for biomedical applications.

The action of serotonin (5-hydroxytryptamine) in vivo upon the microfilariae of Dirofilaria, Loa and five other species.

When serotonin is injected intravenously into certain animals containing microfilariae it causes a sharp short rise in the microfilaria count in the blood, i.e. liberation of microfilariae from the lungs. This happens in the case of Dirofilaria immitis (in dog), D. repens (in dog), Loa loa (in drill), Edesonfilaria malayensis and another Dirofilaria-like microfilaria (in monkey), Monnigofilaria setariosa (in mongoose), and Dipetalonema gracile (in squirrel monkey); but not with Dip. witei (in gerbil) and Litomosoides carinii in cotton rats.This action (upon D. immitis) is not inhibited by atropine. Administration of reserpine, harmine or harmaline to dogs did not exert any definite action on the microfilaria count of D. immitis. Serotonin had no obvious effect on the in vitro activity of microfilariae of L. loa or E. malayensis. Melatonin had no action in vivo upon any of the above microfilariae.The action of serotonin upon microfilariae in vivo is similar to that of acetylcholine but it is not identical with it since the sensitivity of Dip. gracile and Dip. witei to the two compounds is different.Apparently this action is not involved in the production of the 24 h periodicity shown by many microfilariae. It may depend upon disturbance of the normal neuromuscular mechanisms of the microfilariae by which they are retained in the small vessels of the lungs.