Time-domain Vernier effect-based optical fiber sensor.

In this Letter, we demonstrate an easy-to-fabricate time-domain Vernier-effect-based sensor. An all-fiber variable optical delay line (VODL) is utilized to drive an OPD scan of two interferometers simultaneously, and fiber Bragg gratings are used to filter out two slightly detuned time-domain interferometric signals. Then two normalized interferograms with different spatial frequencies can be achieved and utilized to generate an envelope modulation, viz., a Vernier envelope, with enhanced sensitivity in comparison to the native state of the interferometers used. The sensitivity magnification factor of our structure can be regulated simply via altering the resonant wavelength difference of FBGs rather than optimizing the OPDs of the interferometers. The proposed sensor is independent of the precise and complicated fabrication procedures. The Vernier signal can be demodulated without a broadband light source and spectrometer. We argue that the proposed structure may inspire a new concept for constructing simple and cheap Vernier effect-based sensors that are well suited for practical applications.

Design and assessment of a micro-nano positioning hexapod platform with flexure hinges for large aperture telescopes.

In order to compensate the optical system bias, which is caused by the change of elevation angle and thermal gradient during the optical alignment of the telescope, a novel high stiffness micro-nano positioning hexapod platform with flexure hinges is proposed in this paper. The novel flexure hinge has a mechanical limit, and its equivalent model is established and analyzed. In addition, in order to speed up the solution process, a novel simplified inverse kinematic model is developed based on the rigid body kinematic theory. Then, an effective rigid-flexible coupling simulation system is built to verify the correctness and applicability of the inverse kinematic model. Finally, a systematic experimental test method and a statistical-based data analysis theory are proposed. The experimental results show that the resolution and repeatability of translation and rotation and lateral stiffness are as follows: 0.3 mm and 0.5 arc sec, ± 0.5 µm and ±0.5 arc sec, 131.6N⋅µm-1 and 133.0N⋅µm-1. The proposed hexapod platform can be used to correct the optical system bias of large-aperture telescopes.

Extracellular matrix stiffness mediates uterine repair via the Rap1a/ARHGAP35/RhoA/F-actin/YAP axis.

The integrity of the structure and function of the endometrium is essential for the maintenance of fertility. However, the repair mechanisms of uterine injury remain largely unknown. Here, we showed that the disturbance of mechanical cue homeostasis occurs after uterine injury. Applying a multimodal approach, we identified YAP as a sensor of biophysical forces that drives endometrial regeneration. Through protein activation level analysis of the combinatorial space of mechanical force strength and of the presence of particular kinase inhibitors and gene silencing reagents, we demonstrated that mechanical cues related to extracellular matrix rigidity can turn off the Rap1a switch, leading to the inactivation of ARHGAP35and then induced activation of RhoA, which in turn depends on the polymerization of the agonist protein F-actin to activate YAP. Further study confirmed that mechanotransduction significantly accelerates remodeling of the uterus by promoting the proliferation of endometrial stromal cells in vitro and in vivo. These studies provide new insights into the dynamic regulatory mechanisms behind uterine remodeling and the function of mechanotransduction. Video Abstract.

Miniature Fourier transform spectrometer based on a fiber-tip interferometer.

The miniaturization of spectrometers have attracted much attention owning to the demand for portable or in situ spectral analysis in a wide variety of fields, but it is a great challenge to push them into practical applications due to high cost, complicated configuration, and sensitivity to external disturbance. We report on a miniature Fourier transform (FT) spectrometer based on fiber-tip Fizeau interferometer. Hand pulling or any other types of force can be used to drive optical path difference (OPD) scan. Interferences are monitored as a function of time by two photodetectors, one is used to detect the whole interferogram while the other to measure single-wavelength interferogram. In this design, the instantaneous interference intensity as well as OPD can be obtained in an accurate way so that the exact spatial interferogram of the incident spectrum can be worked out. Consequently, the incident spectrum can be retrieved by FT method. A resolution of 7.69 cm-1 in the wavelength range of 1400 nm ∼ 1700 nm is achieved. Experimental results show that the performance of our device is comparable to the commercial benchtop spectrometer. Our device is independent of the complicated fabrication procedures, easy of usage, and cost effective. We envision that the proposed design will inspire a new concept for constructing simple and cheap spectrometers that is well suited for practical applications.

Temperature-insensitive polarimetric vibration sensor.

Vibration measurement is a frequent measurement requirement in a number of areas. Optical vibration sensors have many advantages over electrical counterparts. A common approach is to optically detect the vibration induced mechanical movement of a cantilever. Nevertheless, their practical applications are hindered by the cross-sensitivity of temperature and dynamic instability of the mechanical structure, which lead to unreliable vibration measurements. Here, we demonstrate a temperature insensitive vibration sensor that involves an enclosed suspended cantilever integrated with a readout fiber, providing in-line measurement of vibration. The cantilever is fabricated from a highly birefringent photonic crystal fiber by chemical etching and fused to a single-polarization fiber. Mechanical vibration induced periodic bending of the cantilever can significantly modify the state of polarization of the light that propagates along the photonic crystal fiber. The single-polarization fiber finally converts the state of polarization fluctuation into the change of output optical power. Therefore, the vibration could be demodulated by monitoring the output power of the proposed structure. Due to the special design of the structure, the polarization fluctuation induced by a variation of the ambient temperature can be significantly suppressed. The sensor has a linear response over the frequency range of 5 Hz to 5 kHz with a maximum signal-to-noise ratio of 60 dB and is nearly temperature independent.

Nanoparticle self-assembled technique applied to a whispering-gallery-mode laser.

The low threshold microlaser is the fundamental component of integrated optical circuits. The fabrication method of the microcavity determines the dimension and threshold of lasers, while the doping method limits the available gain materials and emitted wavelength. Here we propose a silica nanoparticles self-assembly technique to fabricate a microlaser with a radius of ∼100 um and Q factor of 2000. The aggregation state of gain molecules is investigated to be J-type dimers with high fluorescence to support the laser generation. The laser can emit a ∼600 nm waveband multimode laser with a low threshold of ∼12 µJ. Such a laser is promising as a coherent light source integrated on the photonic microchips and opens up a new orientation in material science.

Spherical microcavity-based membrane-free Fizeau interferometric acoustic sensor.

The monitoring of acoustic waves is essential for a variety of applications, ranging from photoacoustic imaging to industrial non-destructive evaluation and monitoring. Optical acoustic sensors have many advantages over electrical counterparts such as passivity and immunity to electromagnetic interference, and can be quite compact with all-fiber structures. A common approach is to optically detect the acoustically induced mechanical movement of a cantilever or a reflective membrane. However, sensors based on moving mechanical parts have limitations, because they are influenced by the mechanical properties of the structures involved that behave as a coupled spring-mass system. Here a new type of optical acoustic sensing concept based on a spherical microcavity fiber Fizeau interferometer is described. The sensor is fabricated by inserting a section of single-mode fiber into a spherical microcavity to form a Fizeau interferometer. Thanks to the elasto-optic effect, the sound pressure modifies the refractive index of the microcavity; then a corresponding change in the interferometric spectrum can be observed. The sensor was successfully used to detect acoustic waves under the whole audible region, from 20 Hz to 20 kHz. The experimental results show that the sensitivity can be improved via altering the length of microcavity. The structure is membrane-free, and the sensitivity will not be limited by these size restrictions which makes the technology an interesting alternative to conventional transducers for acoustic wave measurement.

Smartphone based multispectral imager and its potential for point-of-care testing.

We report a smartphone based multispectral imager (MSI), a promising tool for point-of-care (POC) testing, which utilizes a bio-inspired MSI chip to capture both the spectral and spatial information of a target simultaneously. As the key component for compact MSI, the proposed MSI chip mimics the structure of an insect compound-eye, wherein each sub-eye responds to a specific spectral band. This could allow a smartphone to be transformed into an MSI device that could acquire a snap-shot spectral image in a single exposure. An orthogonal polarization imaging method is adopted, to boost the capability of the smartphone MSI for chemical analysis. The feasibility and application potential of the proposed device are demonstrated non-invasively for skin lesion and dental plaque analysis. The experimental results are consistent with the physiological expectations, validating the ability of the smartphone MSI for multispectral image acquisition and further analytical determination. The chemical analysis capability, portability and cost-effectiveness of the smartphone MSI make it a promising analytical tool for POC testing, from chemical analysis to in vivo pathological diagnosis.

Self-assembly three-dimensional optical devices: from microsphere to microlens array.

We report rapid formation of three-dimensional micro optical devices by silica nanoparticle self-assembly in a face-centered cubic (fcc) structure. By controlling the hydrophobic interactions, the self-assembled products are fabricated into different morphologies, which include microsphere and hemisphere. These structures have specific applications in microsphere resonant cavities and microlens arrays. The whispering gallery mode of the formed microsphere is excited by the tapered fiber to demonstrate the optical characters of the microsphere. Moreover, the properties of the fabricated microlens and microlens array are tested through insertion in an imaging system. Ultimately, the optical devices with advanced functions are demonstrated by the secondary phase infiltrating into the interstitial space of silica nanoparticles. This report will open a new direction in manufacturing multifunctional and miniature optical devices by an ultrasimple self-assembly approach.

Exciting surface plasmons on metal-coated multimode optical waveguides using skew rays.

Multipoint surface plasmon resonance (SPR) excitation using a skew ray within a multimode plastic optical waveguide coated with gold, Au, is reported. The effect of skew rays on the performance of SPR has been studied both theoretically and experimentally. The approach also entails a novel method of measuring the SPR angle that is in agreement with theoretically predicted values.

Drawing optical fibers from three-dimensional printers.

The temperature distribution within extrusion nozzles of three low-cost desktop 3D printers is characterized using fiber Bragg gratings (FBGs) to assess their compatibility as micro-furnaces for optical fiber and taper production. These profiles show remarkably consistent distributions suitable for direct drawing of optical fiber. As proof of principle, coreless optical fibers (φ=30 µm) made from fluorinated acrylonitrile butadiene styrene (ABS) and polyethylene terephthalate glycol (PETG) are drawn. Cutback measurements demonstrate propagation losses as low as α=0.26 dB/cm, which are comparable with standard optical fiber losses with some room for improvement. This work points toward direct optical fiber manufacture of any material from 3D printers.

Step-index optical fiber drawn from 3D printed preforms.

Optical fiber is drawn from a dual-head 3D printer fabricated preform made of two optically transparent plastics with a high-index core (NA∼0.25, V>60). The asymmetry observed in the fiber arises from asymmetry in the 3D printing process. The highly multimode optical fiber has losses measured by cut-back as low as α∼0.44 dB/cm in the near IR.

Silica microwire-based interferometric electric field sensor.

Silica microwire, as an optical waveguide whose diameter is close to or smaller than the wavelength of the guided light, is of great interest because it exhibits a number of excellent properties such as tight confinement, large evanescent fields, and great configurability. Here, we report a silica microwire-based compact photonic sensor for real-time detection of high electric field. This device contains an interferometer with propylene carbonate cladding. Based on the Kerr electro-optic effect of propylene carbonate, the applied intensive transient electric field can change the refractive index of propylene carbonate, which shifts the interferometric fringe. Therefore, the electric field could be demodulated by monitoring the fringe shift. The sensor was successfully used to detect alternating electric field with frequency of 50 Hz and impulse electric field with duration time of 200 µs. This work lays a foundation for future applications in electric field sensing.

Effectiveness of sigmoidoscopy or colonoscopy screening on colorectal cancer incidence and mortality: a systematic review and meta-analysis of randomized controlled trial.

Objectives: We conducted a comprehensive analysis to compare colonoscopy and sigmoidoscopy with standard care or fecal immunochemistry regarding colorectal cancer incidence and mortality risk. Methods: Until August 2023, literature from PubMed, Embase, Web of Science, and Cochrane was systematically reviewed. We examined the impact of colonoscopy or sigmoidoscopy versus standard care on colorectal cancer outcomes, including incidence, cancer-specific mortality, and overall mortality. Results: Among 4,265 screened articles, data from seven randomized controlled trials (involving 663,319 participants) were analyzed. The intervention group (colonoscopy or sigmoidoscopy) consisted of 258,938 participants, while the control group received standard care or fecal immunochemical testing, totaling 404,381 participants, with both groups having average colorectal cancer risk, without confounders. Pooled analyses indicated a 20% reduction in colorectal cancer incidence (RR: 0.80, 95% CI: 0.77-0.83) and a 26% decrease in colorectal cancer mortality (RR: 0.74, 95% CI: 0.69-0.80) in the intervention group compared to standard care. All-cause mortality remained unchanged (RR: 1.03, 95% CI: 0.99-1.07). Subgroup analysis favored sigmoidoscopy in reducing colorectal cancer morbidity and mortality. Conclusion: This meta-analysis of randomized controlled trials underscores the effectiveness of colonoscopy and, notably, sigmoidoscopy in reducing colorectal cancer incidence and mortality among average-risk populations. In comparison to fecal immunochemical testing, both colonoscopy and sigmoidoscopy did not significantly impact colorectal cancer incidence and mortality in this population. Systematic review registration: https://www.crd.york.ac.uk/PROSPERO/, identifier CRD42023460007.

Vehicle Lane-Changing scenario generation using time-series generative adversarial networks with an Adaptative parameter optimization strategy.

Connected and automated vehicles (CAVs) hold promise for enhancing transportation safety and efficiency. However, their large-scale deployment necessitates rigorous testing across diverse driving scenarios to ensure safety performance. In order to address two challenges of test scenario diversity and comprehensive evaluation, this study proposes a vehicle lane-changing scenario generation method based on a time-series generative adversarial network (TimeGAN) with an adaptive parameter optimization strategy (APOS). With just 13.3% of parameter combinations tested, we successfully trained a satisfactory TimeGAN and generate a substantial number of lane-changing scenarios. Then, the generated scenarios were evaluated for diversity, fidelity, and utility, demonstrating their effectiveness in capturing a wide range of driving situations. Furthermore, we employed a Lane-Changing Risk Index (LCRI) to identify the rare adversarial cases in scenarios. Compared to real scenarios, our approach generates 27 times more adversarial cases with 1.8 times higher average risk, highlighting its potential for uncovering critical safety vulnerabilities. This study paves the way for more comprehensive and effective CAV testing, ultimately contributing to safer and more reliable autonomous driving technologies.

Integrating visual large language model and reasoning chain for driver behavior analysis and risk assessment.

Driver behavior is a critical factor in driving safety, making the development of sophisticated distraction classification methods essential. Our study presents a Distracted Driving Classification (DDC) approach utilizing a visual Large Language Model (LLM), named the Distracted Driving Language Model (DDLM). The DDLM introduces whole-body human pose estimation to isolate and analyze key postural features-head, right hand, and left hand-for precise behavior classification and better interpretability. Recognizing the inherent limitations of LLMs, particularly their lack of logical reasoning abilities, we have integrated a reasoning chain framework within the DDLM, allowing it to generate clear, reasoned explanations for its assessments. Tailored specifically with relevant data, the DDLM demonstrates enhanced performance, providing detailed, context-aware evaluations of driver behaviors and corresponding risk levels. Notably outperforming standard models in both zero-shot and few-shot learning scenarios, as evidenced by tests on the 100-Driver dataset, the DDLM stands out as an advanced tool that promises significant contributions to driving safety by accurately detecting and analyzing driving distractions.

Fatigue at the wheel: A non-visual approach to truck driver fatigue detection by multi-feature fusion.

BACKGROUND: Monitoring of long-haul truck driver fatigue state has attracted considerable interest. Conventional fatigue driving detection methods based on the physiological and visual features are scarcely applicable, due to the intrusiveness, reliability, and cost-effectiveness concerns. METHODS: We elaborately developed a fatigue driving detection method by fusion of non-visual features derived from the customized wristbands, vehicle-mounted equipment, and trip logs. To capture the spatiotemporal information within the sequential data, the bidirectional long short-term memory network with attention mechanism was proposed to determine whether the truck driver was fatigued within a fine-grained episode of one minute. The model was validated using a natural driving dataset with nine truck drivers on real-world roads in Guiyang, China during June and July 2021. RESULTS: Our approach yielded 99.21 %, 84.44 %, 82.01 %, 99.63 %, and 83.21 % in accuracy, precision, recall, specificity, and F1-score, respectively. Compared with the mainstream visual-based methods, our approach outperformed particularly in terms of precision and recall. Photoplethysmogram stood out as the most important feature for truck driver fatigue state detection. Vehicle load, driving forward angle, cumulative driving time, midnight, and recent working hours were found to be positively associated with the probability of fatigue driving, while the galvanic skin response, vehicle acceleration, current time, and recent rest hours had a negative relationship. Specifically, truck drivers were more likely to fatigue when driving at 20-40 km/h, braking abruptly at 5-10 m/s2, with vehicle loads over 70 tons, and driving more than 100 min consecutively. CONCLUSIONS: Our study is among the first to harness the natural driving dataset to delve into the real-life fatigue pattern of long-haul truck drivers without disruptions on routine driving tasks. The proposed method holds pragmatic prospects by providing a privacy-preserving, robust, real-time, and non-intrusive technical pathway for truck driver fatigue monitoring.

Recent advances in spoilage mechanisms and preservation technologies in beef quality: A review.

Beef is a popular meat product that can spoil and lose quality during postharvest handling and storage. This review examines different preservation methods for beef, from conventional techniques like low-temperature preservation, irradiation, vacuum packing, and chemical preservatives, to novel approaches like bacteriocin, essential oil, and non-thermal technologies. It also discusses how these methods work and affect beef quality. The review shows that beef spoilage is mainly due to enzymatic and microbial activities that impact beef freshness, texture, and quality. Although traditional preservation methods can extend beef shelf life, they have some drawbacks and limitations. Therefore, innovative preservation methods have been created and tested to improve beef quality and safety. These methods have promising results and potential applications in the beef industry. However, more research is needed to overcome the challenges and barriers for their commercialization. This review gives a comprehensive and critical overview of the current and emerging preservation methods for beef and their implications for the beef supply chain.

Crosstalk between Extracellular Matrix Stiffness and ROS Drives Endometrial Repair via the HIF-1α/YAP Axis during Menstruation.

Although the menstrual cycle driven by sex steroid hormones is an uncomplicated physiological process, it is important for female health, fertility and regenerative biology. However, our understanding of this unique type of tissue homeostasis remains unclear. Here, we examined the biological effects of mechanical force by evaluating the changing trend of extracellular matrix (ECM) stiffness, and the results suggested that ECM stiffness was reduced and that breaking of mechanotransduction delayed endometrium repair in a mouse model of simulated menses. We constructed an ECM stiffness interference model in vitro to explain the mechanical force conduction mechanism during endometrial regeneration. We discovered that ECM stiffness increased the expression and nuclear transfer of YAP, which improved the creation of a microenvironment, in a manner that induced proliferation and angiogenesis for endometrial repair by activating YAP. In addition, we observed that physiological endometrial hypoxia occurs during the menstrual cycle and that the expression of HIF-1α was increased. Mechanistically, in addition to the classical F-actin/YAP pathway, we also found that the ROS/HIF-1α/YAP axis was involved in the transmission of mechanical signals. This study provides novel insights into the essential menstrual cycle and presents an effective, nonhormonal treatment for menstrual disorders.

A miniature fiber-optic microphone based on plano-concave micro-interferometer.

The sensitive detection of sound waves is essential for a variety of applications. In this work, we propose a miniature diaphragm-free fiber-optic microphone based on a plano-concave optical micro-interferometer. A solid plano-concave micro-interferometer is formed at the end of a cleaved fiber by depositing a tiny volume of liquefied glass. Sound wave induced periodic variation of pressure can significantly modify the refractive index of the plano-concave glass due to the elasto-optic effect, and then, the phase difference between two interferometric beams will be remarkably changed accordingly. The interferometer finally converts the fluctuation of the phase difference into the change in the output optical power. Consequently, the sound wave can be demodulated by detecting the output power of the microphone. The experimental results show that the proposed microphone has the ability to detect sound waves in the whole audible range and almost omnidirectional. The noise-limited minimum detectable sound pressure is around 12 µPa/Hz. In addition, the human voice detection test shows that the performance of our microphone is competitive with the most advanced commercial device. The structure is stable without any movable mechanical parts, and the size is as small as 0.25 mm, which makes the proposed microphone an attractive alternative to the conventional one for sound wave detection.