This paper proposes a novel magnetic field sensor based on a microfiber coupler (MFC) combined with a magnetic fluid (MF) in a Sagnac loop formed from a polarization maintaining fiber (PMF). Thanks to the small (~2.6 μm) waist diameter of the MFC, the resulting interference is strongly influenced by the presence of the MF and this leads to the desirable high sensitivity of the structure to the applied magnetic field. The maximum magnetic field sensitivities of −100 pm/mT and −488 pm/mT have been experimentally demonstrated with the PMF lengths of 75 cm and 20 cm respectively in the range of magnetic field strengths from 0 to 200 mT. The dependence of the magnetic field orientation on the performance of the proposed sensor was also examined. The proposed magnetic field sensor is advantageous for applications requiring higher sensitivity over a wide magnetic field range.

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Abstract:A new type of fiber optic relative humidity (RH) sensor based on an agarose coated silica microsphere resonator is proposed and experimentally demonstrated. Whispering gallery modes (WGMs) in the micro resonator are excited by evanescent coupling using a tapered fiber with ~3.3 µm waist diameter. A change in the relative humidity of the surrounding the resonator air induces changes in the refractive index (RI) and thickness of the Agarose coating layer. These changes in turn lead to a spectral shift of the WGM resonances, which can be related to the RH value after a suitable calibration. Studies of the repeatability, long-term stability, measurement accuracy and temperature dependence of the proposed sensor are carried out. The RH sensitivity of the proposed sensor depends on the concentration of the agarose gel which determines the initial thickness of the deposited coating layer. Studies of the micro-resonators with coating layers fabricated from gels with three different Agarose concentrations of 0.5%, 1.125% and 2.25 wt./vol.% showed that an increase in the initial thickness of the coating material results in an increase in sensitivity but also leads to a decrease of quality factor (Q) of the micro resonator. The highest sensitivity achieved in our experiments was 518 pm/%RH in the RH range from 30% to 70%. The proposed sensor offers the advantages of a very compact form factor, low hysteresis, good repeatability, and low cross sensitivity to temperature.

Objective To determine the relative benefit of mirror therapy and mental imagery in phantom limb pain. Design Prospective randomized controlled trial. Setting Physical Medicine and Rehabilitation Department, All India Institute of Medical Sciences, Patna. Participants Amputees (N=92) with no significant difference in baseline characteristics. There was a male predominance in both groups (mirror therapy: 36 men, 10 women; mental imagery: 37 men, 9 women). Intervention Patients of both groups underwent a conventional amputee rehabilitation program and daily treatment of either mirror therapy or mental imagery on a regular basis, first in a rehabilitation care unit and later at home. Main Outcome Measures Phantom limb pain (PLP) was measured by visual analog scale (VAS) score at baseline (0) and at 4, 8, and 12 months. Results This study included 92 patients ranging in age from 12 to 75 years (average, 34.79y). There was no significant difference in VAS score between the groups at baseline, but we found a significant reduction of pain in both groups at follow-up. However, upon comparing the improvement in both groups, we determined that the mirror therapy group had better improvement (from 7.07±1.74 to 2.74±0.77) compared with the mental imagery group (from 7.85±0.76 to 5.87±1.41). Conclusions Mirror therapy and mental imagery are both good and cost-effective rehabilitation aids for amputee patients to reduce PLP, but mirror therapy appears to be more effective than mental imagery.

A novel fiber optic sensing configuration for simultaneously measuring ammonia vapor (NH 3) concentration and relative humidity (RH) in air is proposed and experimentally demonstrated. The system comprised two silica whispering gallery mode (WGM) microsphere resonators coated with different polymer layers. One of the microspheres was dip-coated with sol gel silica polymer and another with a 0.5 % wt./vol. agarose hydrogel. WGMs in both microspheres were excited simultaneously by evanescent coupling using a single adiabatic fiber taper. The optical properties of both coating layers change due to their exposure to ammonia and water molecules in the surrounding atmosphere, resulting in the spectral shifts of the WGM resonances relevant to each of the microspheres. By measuring the relevant WGMs' spectral shifts, the NH 3 concentration in air and the RH can be determined simultaneously. The experimentally demonstrated sensitivity of the proposed sensor array to ammonia was estimated as 19.07 pm/ppm (NH 3 molecules in air) and its sensitivity to relative humidity as 1.07 pm/% RH. Detailed studies of the coatings' cross-sensitivity and temperature dependence are also presented. The proposed sensor array is compact, highly sensitive and potentially low cost.