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Encapsulation of microfiber Mach-Zehnder interferometer (MMZI) sensor for temperature and salinity sensing in seawater is developed. It includes a C-shape metal tube with a slit on the bottom and polymer adhesive with large elasticity modulus, by which a more robust sensor with relatively fast response can be obtained. To evaluate the performance of sensor after encapsulation, effects of different polymer adhesives on tension withstanding, temperature and salinity sensitivities are evaluated, and dependence of response time on shape of metal tube is investigated. Results show that sensitivities of the sensor in temperature and salinity sensing can reach to be about −1.77 nm/°C and 1.18 nm/ ‰, and response times are about 219.0 ms and 12.5 ms, respectively. By comparing temperatures and salinities measured by sensor with those measured by commercial device, accuracy of the sensor after encapsulation is proved. In addition, cross-sensitivities of strain/pressure and short/long-term stability after encapsulation are also evaluated. Finally, based on the basic structure, further improvements are attempted, such as double encapsulation with stainless steel mesh and complex encapsulation with two kinds of polymer. Encapsulations of MMZI demonstrated here show advantages of low cost, improved robustness, relatively fast response, long-term stability and easy expandability, which will not only afford a critical support for optical sensors operated in the ocean, but also offer some useful references for microfiber sensors used in other sensing applications. [ABSTRACT FROM AUTHOR]

Simultaneous measurement of pressure and temperature in seawater is realized based on polydimethylsiloxane (PDMS) sealed microfiber Mach–Zehnder interferometer (MZI). Benefitting from the high thermal-optic coefficient and large elasticity of PDMS, high sensitivity and robust structure can be obtained. In theoretical modeling, significant enhanced pressure response in fiber is observed clearly, and pressure or temperature sensitivities are calculated theoretically. In experiment, PDMS sealed MZI is fabricated by a two-step sealing method. Using this MZI, sensitivity of 13.31 nm/MPa for pressure sensing and −7.41 nm/°C for temperature sensing are demonstrated, respectively, which are about one order higher than bare fiber MZIs (without PDMS sealing). To verify the accuracy of sensor, several tests under arbitrarily pressure and temperature are performed with average errors of 4.38% and 1.44%, respectively. In addition, effects of encapsulation on avoiding cross-sensitivity with salinity, PDMS thickness on pressure sensitivity, response time, repeatability, time stability, and polarization of the sensor are also evaluated by experiment. Sensors demonstrated here show advantages of low cost, simple fabrication, robust and compact structure, high-pressure resistance, high sensitivity, good repeatability, and long-term stability. [ABSTRACT FROM AUTHOR]

Response time of optical microfiber temperature sensor is investigated based on the microfiber modal interferometer (MMI). Sensitivity of −406pm/°C is obtained in temperature sensing, which is one order higher than those of fiber Bragg gratings (FBGs) and microfiber resonators, and response time of 13.1ms is measured, which is twice as fast as FBGs. Based on the theoretical expression of time constant in temperature sensing, dependences of response time on many factors, such as heat transfer coefficient, fiber diameter and ambient temperature are investigated, respectively. In addition, relationship of time constant and response time, dependence of response time on detection device or fiber length, and repeatability of sensor are also discussed. Results demonstrated here may afford some useful references for optical sensors used in obtaining temperature profile and transient process in seawater or analyzing temporal response of temperature sensors in other liquid surroundings. [ABSTRACT FROM AUTHOR]

Objective: The aim of this study is to identify the common microorganisms causing PJI as well as the drug‐resistant spectrum for each microorganism, to help orthopaedic surgeons to choose appropriate antibiotics. Method: One hundred and sixty patients who suffered from failure of primary or revision total hip or knee arthroplasty for different reasons were prospectively recruited. These patients underwent revision or re‐revision total hip or knee arthroplasty in our institution between August 2013 to August 2016. The details of patients’ medical history and comprehensive physical examination, as well as demographic data were recorded precisely. Routine blood test results, erythrocyte sedimentation rate (ESR), C‐reactive protein (CRP), high sensitive C‐reactive protein (hs‐CRP), interleukin‐6 (IL‐6) levels, and synovial leukocyte counts were collected. Additionally, aspiration was conducted during surgery to avoid pollution unless when PJI was strongly suspected, in which case, joint puncture and aspiration were conducted before surgery. Intraoperatively, the implant‐surrounding tissue and the prosthesis were collected under aseptic conditions. Postoperatively, the prosthesis, implant‐surrounding tissue and synovium were sent to the laboratory immediately. The sonicate extraction (the prosthesis was sent for ultrasound sonication first), implant surrounding tissue and synovium were sent for microbiologic culture, and the implant‐surrounding tissue was also sent for pathological examination. The isolated bacteria strains and drug‐resistance rates for each pathogen for different antibiotics were presented. Results: There were 59 PJI cases in the infectious group and 101 cases in the non‐infectious group (PJI is diagnosed according to the diagnosing criteria from the Workgroup of the Musculoskeletal Infection Society). Of 69 strains of pathogens isolated, Gram‐positive bacterium is the most common pathogenic bacteria causing PJI (60, 86.96%). Staphylococcus epidermidis and Staphylococcus aureus played an important role as well, followed by Gram‐negative bacteria (8, 11.59%) and fungus (1, 1.45%). Penicillin (78.57%), erythromycin (66.67%) and clindamycin (44.74%) showed high antibiotic resistance rate. In addition, the second‐generation cephalosporin, usually as the prophylactic antibiotic, resistance rate was high (20%) as well. Fortunately, no vancomycin‐resistant bacteria were discovered in the current study. Conclusion: This study provides some information on the most common pathogens in our institution and the selection of antibiotics in the perioperative period in northern China. Cefuroxime and clindamycin might not be appropriate for use as prophylactic antibiotics in revision total knee or hip arthroplasty. Vancomycin is ideal for empiric antibiotic use in suspected PJI cases because of the low drug‐resistance rate. [ABSTRACT FROM AUTHOR]

• A comprehensive theoretical analysis on mode excitation of in-line MZI is performed. • Main excited modes can be predicted by calculating field profiles of modes supported. • Irregularity of spectrum can be predicted generally by calculating n eff s in fibers. • An equivalent mode approximation approach is proposed and verified experimentally. • The MZIs show advantages of low cost, easy fabrication and relative high sensitivity. Mode excitation of in-line Mach-Zehnder interferometer (MZI) with offset splicing between standard single-mode fiber (SMF) and thin-core fiber (TCF) is investigated. Based on the mode field profiles of high order modes in TCF, dependence of mode excitation on core offset is researched firstly. It is revealed that which modes can be significantly excited is strongly dependent on the mode fields matching between LP 01 mode in SMF and LP 1n mode in TCF, by which the dominant excited modes can be predicted and this method can be expanded to any two fibers with offset splicing. Based on the energy distributions of excited modes with/without considering interference among cladding modes, transmission spectra can be calculated by interference equations theoretically. By comparing with experimental results, it can be concluded that for kind of MZIs based on offset splicing, it is difficult to make the calculated results to be identical with experimental results due to the large number of modes excited, so an equivalent mode approach is proposed to solve this problem and verified by the temperature sensing experiment. In addition, dependence of mode excitation on probing wavelength or refractive index (RI) of surroundings, and effect of fiber parameters on signal shape are also studied. The MZI proposed here shows advantages of low cost, easy fabrication, no special splicing equipment required, and relative high sensitivity. Results shown here will provide valuable information for kind of MZIs based on core-offset splicing between TCF and SMF, and afford useful references for other kinds of in-line MZIs based on the interference between core and cladding modes. [ABSTRACT FROM AUTHOR]