Marine ecological security shelter in China: Concept, policy framework, mechanism and implementation obstacles.

Building a marine ecological security shelter (MESS) has become the main strategy to adapt marine ecological threats in China. As China's marine policy lacks a robust framework document, it is necessary to consider whether the policy system can effectively support the construction of MESS. However, the linkage between the construction measures of MESS and related policies is not clear. Therefore, the purpose of this paper is to clarify the concept of MESS and its connection with policy, by adopting the policy content analysis method to analyze the evolution process of MESS-related policy system. The legislative shortcomings and implementation obstacles of the MESS-related policy system are then summarized and discussed. The results show that from 1981 to 2021 the MESS-related policy system has been continuously improved. However, the policy system's support and guarantee capacity for building MESS still needs to be improved. (1) Due to the lack of basic laws and special laws, the coordination among governance subjects and among policies lacks legislative guarantee. (2) The construction of MESS continues the inter-regional and inter-department administrative barriers in collaborative governance of marine environment. To establish an effective collaborative governance model, it is essential to improve the governance structure and mechanism. (3) The government-led governance pattern faces the problem of mechanism failure. The command and control instrument accounts for more than 82%, and the public and enterprises lack strong policy guarantees to participate in marine governance. (4) The policy system's adaptability to emerging threats must be improved. Marine policies rarely involve emerging threats such as climate change and new pollutants. Meanwhile, the real-time supervision and monitoring mechanism is weak. The real-time supervision is only accounting for about 10%. Generally speaking, as a complex and long-term system engineering, the construction of MESS will inevitably encounter contradictions in politics, culture, and economy. China should deepen the construction of marine ecological civilization and form a governance concept based on ecosystems. Overall, this paper helps to understand the internal connection between MESS and policy comprehensively and provides a new perspective for improving China's marine governance capacity.

Enhanced wide-range gas pressure sensing with an all-solid open Fabry-Pérot interferometer.

The sensors with a wide gas pressure detection range are urgently demanded in many industrial applications. Here, we propose a gas pressure sensor based on an all-solid open Fabry-Pérot interferometer, which is prepared by using optical contact bonding to ensure high structural strength and high-quality factor of 8.8 × 105. The applied pressure induces a change in the refractive index of the air, leading to the shift of the resonant spectrum. The pressure is detected by calibrating this shift. The sensor exhibits a pressure sensitivity of 4.20 ± 0.01 nm/MPa in a pressure range of 0 to 10 MPa and has a minimum pressure resolution of 0.005 MPa. Additionally, it shows a lower temperature cross-sensitivity of -0.25 kPa/°C. These findings affirm that the sensor achieves high-sensitivity pressure sensing across a wide detection range. Moreover, owing to its exceptional mechanical strength, it holds great promise for applications in harsh environments, such as high temperature and high pressure.

Research on high-temperature characteristics of a miniature Fabry-Pérot cavity acoustic sensor.

The applications of fiber-optic acoustic sensors are expanded to the high-temperature field, but it still faces challenges to realize the wide-band and high-sensitivity acoustic signal detection in high-temperature environments. Here, we propose a miniature membrane-free fiber-optic acoustic sensor based on a rigid Fabry-Pérot (F-P) cavity and construct an acoustic signal detection system. The system can achieve high-sensitivity acoustic detection while maintaining a wide frequency band in temperatures ranging from 20 °C to 200 °C. The prepared F-P cavity based on optical contact technology is the sensitive unit of the sensor, and has a high-quality factor of 8.8×105. Specifically, with the increasing of temperature, the sensitivity gradually increases, and the frequency response range does not change. A maximum sensitivity of 491.2 mV/Pa and a high signal-to-noise ratio of 60.9 dB are achieved at 200 °C. The sensor has an excellent acoustic signal response in the frequency range of 10 Hz-50 kHz with a flatness of ±2 dB. This study is important for the application of the fiber-optic acoustic sensor in high-temperature environments.

Compact fiber-optic Fabry-Perot cavity based on sandwich structure adopting direct bonding of quartz glass.

A compact fiber-optic Fabry-Perot (F-P) cavity for a sensor is designed based on a sandwich structure, adopting direct bonding of quartz glass. The reflective F-P cavity is manufactured by a fiber optic with a quartz glass ferrule and the sandwich structure with an air cavity, which is achieved by direct bonding of quartz glass. This fabrication process includes plasma surface activation, hydrophilic pre-bonding, high-temperature annealing, and dicing. The cross section of the bonding interface tested by a scanning electron microscope indicates that the sandwich structure is well bonded, and the air cavity is not deformed. Experiments show that the quality factor of the F-P cavity is 2711. Tensile strength testing shows that the bond strength exceeds 35 MPa. The advantage of direct bonding of quartz glass is that high consistency and mass production of the cavity can be realized. Moreover, the cavity is free of problems caused by the mismatch of thermal expansion coefficients between different materials. Therefore, the F-P cavity can be made into a sensor, which is promising in detecting air pressure, acoustic and high temperature.

Single-photon cesium Rydberg excitation spectroscopy using 318.6-nm UV laser and room-temperature vapor cell.

We demonstrate a single-photon Rydberg excitation spectroscopy of cesium (Cs) atoms in a room-temperature vapor cell. Cs atoms are excited directly from 6S1/2 ground state to nP3/2 (n = 70 - 100) Rydberg states with a 318.6 nm ultraviolet (UV) laser, and Rydberg excitation spectra are obtained by transmission enhancement of a probe beam resonant to Cs 6S1/2, F = 4 - 6P3/2, F' = 5 transition as partial population on F = 4 ground state are transferred to Rydberg state. Analysis reveals that the observed spectra are velocity-selective spectroscopy of Rydberg state, from which the amplitude and linewidth influenced by lasers' Rabi frequency have been investigated. Fitting to energies of Cs nP3/2 (n = 70 -100) states, the determined quantum defect is 3.56671(42). The demodulated spectra can also be employed as frequency references to stabilize the UV laser frequency to specific Cs Rydberg transition.

Cavity-enhanced frequency doubling from 795nm to 397.5nm ultra-violet coherent radiation with PPKTP crystals in the low pump power regime.

We demonstrate a simple, compact and cost-efficient diode laser pumped frequency doubling system at 795 nm in the low power regime. In two configurations, a bow-tie four-mirror ring enhancement cavity with a PPKTP crystal inside and a semi-monolithic PPKTP enhancement cavity, we obtain 397.5nm ultra-violet coherent radiation of 35mW and 47mW respectively with a mode-matched fundamental power of about 110mW, corresponding to a conversion efficiency of 32% and 41%. The low loss semi-monolithic cavity leads to the better results. The constructed ultra-violet coherent radiation has good power stability and beam quality, and the system has huge potential in quantum optics and cold atom physics.

A Large-Range and High-Sensitivity Fiber-Optic Fabry-Perot Pressure Sensor Based on a Membrane-Hole-Base Structure.

In the field of in situ measurement of high-temperature pressure, fiber-optic Fabry-Perot pressure sensors have been extensively studied and applied in recent years thanks to their compact size and excellent anti-interference and anti-shock capabilities. However, such sensors have high technological difficulty, limited pressure measurement range, and low sensitivity. This paper proposes a fiber-optic Fabry-Perot pressure sensor based on a membrane-hole-base structure. The sensitive core was fabricated by laser cutting technology and direct bonding technology of three-layer sapphire and develops a supporting large-cavity-length demodulation algorithm for the sensor's Fabry-Perot cavity. The sensor exhibits enhanced sensitivity, a simplified structure, convenient preparation procedures, as well as improved pressure resistance and anti-harsh environment capabilities, and has large-range pressure sensing capability of 0-10 MPa in the temperature range of 20-370 °C. The sensor sensitivity is 918.9 nm/MPa, the temperature coefficient is 0.0695 nm/(MPa∙°C), and the error over the full temperature range is better than 2.312%.

Acoustic Sensing Performance Investigation Based on Grooves Etched in the Ring Resonators.

Acoustic detection based on optical technology has moved in the direction of high sensitivity and resolution. In this study, an optical waveguide acoustic sensor based on a ring resonator with the evanescent field is proposed. Grooves are introduced into the ring resonators as a direct sensitive structure to excite the evanescent field. A series of resonators with diverse grooves are fabricated for a comparative analysis of acoustic performance. The acoustic parameters of bandwidth, sensitivity, and signal-to-noise ratio (SNR) vary with different grooves indicated by the Q-factor. The results show that the ring resonators with variable-sized grooves exhibit excellent capability of acoustics detection. A maximum frequency of 160 kHz and a high sensitivity of 60.075 mV/Pa is achieved, with the minimum detectable sound pressure being 131.34 µPa/Hz1/2. Furthermore, the resonators with high Q-factors represent a remarkable sound resolution reaching 0.2 Hz. This work is of great significance for optimizing acoustic sensors and broadening the application range.

Alternative Approach to Design and Optimization of High-Q Ring Resonators for Membrane-Free Acoustic Sensors.

Membrane-free acoustic sensors based on new principle and structure are becoming a research hotspot, because of many advantages, e.g., their wide bandwidth and high sensitivity. It is proposed that a membrane-free acoustic sensor employs a semi-buried optical waveguide ring resonator (SOWRR) as a sensing element. Using air as the upper cladding medium, the excited evanescent field in the air cladding medium would be modulated by acoustic wave. On this basis, the acoustic sensing model is established. Taking high Q factor and resonance depth as design criteria, the optimal design parameters are given. The optimal values of the air/SiO2: Ge/SiO2 waveguide resonator length and coupling spacing are obtained as 50 mm and 5.6 µm, respectively. The Q factor of the waveguide resonator of this size is as high as 8.33 × 106. The theoretical simulation indicates that the frequency response ranges from 1 Hz to 1.58 MHz and that the minimum detectable sound pressure is 7.48 µPa using a laser with linewidth of 1 kHz. Because of its advantages of wide bandwidth and high sensitivity, the membrane-free sensor is expected to become one of the most promising candidates for the next-generation acoustic sensor.

Acoustic Performance Study of Fiber-Optic Acoustic Sensors Based on Fabry-Pérot Etalons with Different Q Factors.

The ideal development direction of the fiber-optic acoustic sensor (FOAS) is toward broadband, a high sensitivity and a large dynamic range. In order to further promote the acoustic detection potential of the Fabry-Pérot etalon (FPE)-based FOAS, it is of great significance to study the acoustic performance of the FOAS with the quality (Q) factor of FPE as the research objective. This is because the Q factor represents the storage capability and loss characteristic of the FPE. The three FOASs with different Q factors all achieve a broadband response from 20 Hz to 70 kHz with a flatness of ±2 dB, which is consistent with the theory that the frequency response of the FOAS is not affected by the Q factor. Moreover, the sensitivity of the FOAS is proportional to the Q factor. When the Q factor is 1.04×106, the sensitivity of the FOAS is as high as 526.8 mV/Pa. Meanwhile, the minimum detectable sound pressure of 347.33 µPa/Hz1/2  is achieved. Furthermore, with a Q factor of 0.27×106, the maximum detectable sound pressure and dynamic range are 152.32 dB and 107.2 dB, respectively, which is greatly improved compared with two other FOASs. Separately, the FOASs with different Q factors exhibit an excellent acoustic performance in weak sound detection and high sound pressure detection. Therefore, different acoustic detection requirements can be met by selecting the appropriate Q factor, which further broadens the application range and detection potential of FOASs.

An Optical Acoustic Detection System Based on Fabry Pérot Etalon Stability Structure.

The optical acoustic detection system based on the Fabry Pérot Etalon (FPE) with high quality-factor (High Q) and stability structure is described and tested. The FPE contains two high-reflectivity Plano-Concave lenses, achieving high fineness and stability. The protective structure of the confocal stabilized FPE is composed of an invar tube, copper sheath, Bakelite sheath and aluminum housing to protect the sensor from the effects of ambient temperature and vibration. The audio signal is injected into the cavity through the sound hole located in the center of the cavity. Acoustic waves induce the vibration of the medium in the cavity, which leads to a simultaneous change in the FPE optical path and a shift of the interference spectrum. The acoustic detection system is built, and the frequency of the laser is locked on the resonant frequency points of the FPE by using phase modulation technology, so as to detect acoustic signals of different frequencies and amplitudes. In addition, the sensitivity of the proposed sensor exceeds 34.49 mV/Pa in the range of 20 Hz-20 kHz. A Signal-to-Noise Ratio (SNR) of 37 dB can be achieved at 20 Hz. Acoustic signal detection technology based on the FPE stability model is used to test the theoretical feasibility of the future high sensitivity Fabry Pérot Interferometric (FPI) acoustic sensors.

Association of tea consumption and the risk of thyroid cancer: a meta-analysis.

OBJECTIVES: Epidemiological studies evaluating the association of tea consumption and the risk of thyroid cancer risk have produced inconsistent results. Thus, we conducted a meta-analysis to assess the relationship between tea consumption and thyroid cancer risk. METHODS: Pertinent studies were identified by a search in PubMed and Web of Knowledge. The random effect model was used based to combine the results. Publication bias was estimated using Egger's regression asymmetry test. RESULTS: Finally, 11 articles with 14 studies (2 cohort studies and 12 case-control studies) involving 2,955 thyroid cancer cases and 106,447 participants were included in this meta-analysis. The relative risk (95% confidence interval) of thyroid cancer for the highest versus the lowest category of tea consumption was 0.774 (95% CI = 0.619-0.967), and the associations were also significant in Europe and America, but not in the Asia. No publication bias was found. CONCLUSIONS: Our analysis indicated that higher tea consumption may have a protective effect on thyroid cancer, especially in Europe and America.