Microwave-photonic optical fiber interferometers for wavelength interrogation of fiber Bragg grating sensors with high sensitivity and a tunable dynamic range.

We propose and demonstrate a new, to the best of our knowledge, microwave interference-based scheme with high sensitivity and tunable measurement range, which is realized by a Mach-Zehnder interferometer (MZI). A chirped fiber Bragg grating and single-mode fiber serve as the two unbalanced arms of the RF interferometer. The induced differential chromatic dispersion transfers the wavelength shift of the fiber Bragg gratings to the change of the RF phase difference between the two interferometric carriers, which ultimately leads to the variation of the RF signal intensity. The phase sensitivity can be improved by adjusting the power ratio of the two beams in the interferometer and coarse adjustment of the optical variable delay line (OVDL). The OVDL is also employed to tune the measurement range of the system by adjusting the time delay difference between the two arms of the MZI. The system effectively solves the problem of unavoidable attenuation of the sensitivity of the optical carrier-based microwave interferometry system caused by the change of phase difference due to the change of measurement parameters, avoiding the mutual constraint between the measurement range and high sensitivity.

High-precision temperature-compensated fiber Bragg grating axial strain sensing system based on a dual-loop optoelectronic oscillator with the enhanced Vernier effect.

A temperature-compensated fiber Bragg grating (FBG) axial strain sensor based on a two-dual-loop optoelectronic oscillator (OEO) with the enhanced Vernier effect is proposed and experimentally demonstrated. The sensing head consists of two cascaded FBGs, one of which acts as a sensing FBG to measure both the axial strain and temperature and the other as a reference FBG to detect temperature. Acting as the optical carrier, the reflected optical signal of the sensing head is divided into two paths with opposite dispersion coefficients and slightly different lengths to achieve an enhanced Vernier effect. After being divided by a wavelength division multiplexer, the optical signal launches into two electrical paths with different electrical bandpass filters (EBPFs) for frequency division multiplexing. The EBPF I selects the microwave signal generated by the sensing FBG, while the EBPF II selects the microwave signal generated by the reference FBG. Therefore, the axial strain and temperature can be recovered by recording the microwave frequency within EBPF I, and the temperature can be interrogated by tracking the microwave frequency within EBPF II. The axial strain applied on the sensing FBG can be distinguished by solving the cross-sensitivity matrix. The results show that the sensitivity of the dual-loop OEO is much greater than that of the single-loop OEO. The maximum measurement error for the axial strain is 0.112µÎµ, and the maximum temperature compensation error is as low as 0.024°C in the dual-loop OEO, which is far less than that in the single-loop OEO. The enhanced Vernier effect not only improves the sensitivity, but also reduces the temperature compensation error.

Distributed strain interrogation with a linearly chirped fiber Bragg grating based on an optoelectronic oscillator.

A novel distributed strain sensor method, to the best of our knowledge, based on a linearly chirped fiber Bragg grating (LCFBG), which can simultaneously determine the strain value and ascertain the position, is proposed and experimentally demonstrated. Different from the traditional distributed grating interrogation system via analyzing the optical spectrum of an LCFBG, the system is mainly based on the frequency domain measurement by using an optoelectronic oscillator (OEO) structure, which has the characteristics of fast response and high resolution. Based on this structure, when the distributed strain is applied to the LCFBG, the frequency response of the OEO for a reflective point of a certain wavelength will change. The strain value can be obtained by detecting the frequency shift of the OEO. Combined with the one-to-one correspondence between the wavelength and the spatial position of the LCFBG, the exact position of the strain point can be determined. In a proof-of-concept experiment, interrogation of fully distributed grating sensors with nonuniform strain distributions is demonstrated experimentally. A spatial resolution of ∼3µm over a gauge length of 53 mm and a strain resolution of <1µÎµ have been achieved.

Applications and challenges of low temperature plasma in pharmaceutical field.

Low temperature plasma (LTP) technology has shown an outstanding application value in the pharmaceutical filed in recent ten years. This paper reviews the research advances in LTP, including its effects on enhancing or inhibiting drug activity, its combined use with drugs to treat cancers, its effects on the improvement of drug delivery system, its use in preparation of new inactivated virus vaccines, its use with mass spectrometry for rapid detection of drug quality, and the anti-tumor and sterilization effects of plasma-activated liquids. The paper also analyzes the challenges of LTP in the pharmaceutical filed, hoping to promote related research.

Decolorization effect and related mechanism of atmospheric pressure plasma jet on Eriochrome Black T.

In this study, Eriochrome Black T (EBT) in water was decolorized by means of argon atmospheric pressure plasma jet (APPJ), which showed great decolorization performance. The results showed that the relatively high decolorization rate (approximately 80%) was obtained after plasma treatment for 6 min. Changes to some reactive oxygen and nitrogen species (RONS) in the liquid phase were detected. The contents of peroxide, HO·, O2 -·, and NO· in the plasma-treated EBT solution were much less than those in the activated water. The roles of H2O2 and HO· in the decolorization of EBT solution were explored by evaluating the effects of their scavengers, and by exploring the direct effect of H2O2. The results indicated that reactive oxygen species (ROS), especially HO· and O2 -·, played significant roles in the decolorization of the EBT solution. Analysis of degradation by-products indicated that plasma discharge could destroy the azo bond first and gradually break the aromatic rings of EBT molecules into small molecular compounds.

Low-temperature Plasma Promotes Fibroblast Proliferation in Wound Healing by ROS-activated NF-κB Signaling Pathway.

Low-temperature plasma (LTP) has shown great promise in wound healing, although the underlying mechanism remains poorly understood. In the present study, an argon atmospheric pressure plasma jet was employed to treat L929 murine fibroblasts cultured in vitro and skin wounds in BALB/c mice. The in vitro analysis revealed that treatment of fibroblasts with LTP for 15 s resulted in a significant increase in cell proliferation, secretion of epidermal growth factor (EGF) and transforming growth factor-ßi (TGF-ßi), production of intracellular reactive oxygen species (ROS), and the percentage of cells in S phase, protein expression of phosphorylated p65 (P-p65) and cyclinD1, but a noted decrease in the protein expression of inhibitor kappa B (IκB). The in vitro experiments demonstrated that 30-s LTP treatment enhanced the number of fibroblasts and the ability of collagen synthesis, while 50-s treatment led to the opposite outcomes. These results suggested that LTP treatment promotes the fibroblast proliferation in wound healing by inducing the generation of ROS, upregulating the expression of P-p65, downregulating the expression of IκB, and activating the NF-κB signaling pathway and consequently altering cell cycle progression (increased DNA synthesis in S phage).