Search

Glucose monitoring sensors with high softness and flexibility are critical for the developments of wearable and implantable healthcare devices that enable diagnosis, prognosis, and management of diabetes. The design and implementation of such sensors have been extensively exploited by electrochemical strategies, which, however, suffer from poor reusability and complex modification procedures, and necessitate frequent calibration or sensor replacement due to enzymatic reaction instability. Here, a soft and plasmonic hydrogel optical sensor is created for quantitative and continuous glucose monitoring under physiological conditions. The optical sensor consists of a flexible optical fiber made from composites of gold nanoparticles and glucose-responsive hydrogels. The reversible binding of glucose to the nanocomposite optical fiber results in dynamic volume expansion of the hydrogel matrix, which modulates the localized surface plasmon resonance effect, enabling glucose to be quantified from the light transmission. To achieve robust readout, a dual-wavelength differential approach is employed to endow the sensor with self calibration capability. We show that the sensor is reversible and reusable for detecting physiological glucose levels with high linearity and negligible hysteresis. The soft and flexible glucose sensor holds great promises of serving as a minimally-invasive probe for point-of-care glucose monitoring in clinics.

Nonlinear optical microscopy (NOM) has been widely adopted in neural imaging in vivo for its advantages in deep penetration, three‐dimensional resolution, and low phototoxicity, etc. However, it relies on femtosecond laser sources for signal excitation, which are complex and bulky for conventional solid‐state ultrafast lasers. Alternatively, the development of mode‐locking fiber lasers has successfully promoted their applications in biomedical imaging. This paper focuses on the advances of mode‐locking fiber lasers in neural imaging, based on both multiphoton fluorescence microscopy and parametric NOM. Fiber laser oscillators are summarized for exciting two‐photon microscopy directly and fiber lasers based on nonlinear frequency shifting for exciting three‐photon microscopy. Besides, the applications of mode‐locking fiber lasers in parametric NOM are briefly introduced, including harmonic generation microscopy and coherent Raman microscopy. Moreover, the potentials of mode‐locking fiber lasers are highlighted in two‐photon optogenetics for neural modulation. With the emerging of novel high‐energy fiber lasers, their widespread applications are expected in the study of neuroscience. [ABSTRACT FROM AUTHOR]

Rapid and accurate identification of moving load is crucial for bridge operation management and early warning of overload events. However, it is hard to obtain them rapidly via traditional machine learning methods, due to their massive model parameters and complex network structure. To this end, this paper proposes a novel method to perform moving loads identification using MobileNetV2 and transfer learning. Specifically, the dynamic responses of a vehicle–bridge interaction system are firstly transformed into a two-dimensional time-frequency image by continuous wavelet transform to construct the database. Secondly, a pre-trained MobileNetV2 model based on ImageNet is transferred to the moving load identification task by transfer learning strategy for describing the mapping relationship between structural response and these specified moving loads. Then, load identification can be performed through inputting bridge responses into the established relationship. Finally, the effectiveness of the method is verified by numerical simulation. The results show that it can accurately identify the vehicle weight, vehicle speed information, and presents excellent strong robustness. In addition, MobileNetV2 has faster identification speed and requires less computational resources than several traditional deep convolutional neural network models in moving load identification, which can provide a novel idea for the rapid identification of moving loads. [ABSTRACT FROM AUTHOR]

We report an all-optical switch based on two-pump four-wave mixing in fibers. The switched signal is not shifted in frequency in this scheme. For different signal wavelengths, the pump wavelengths and powers can be optimized to achieve the best performance. The principle of how to design the switch is discussed in detail. A high extinction ratio of -60 dB is obtained when the pump parameters are optimized by a genetic algorithm that exhibits good convergence property and high computing efficiency. The effect of zero-dispersion wavelength fluctuations along the fiber on the switch is analyzed. OCIS codes: 060.1810, 060.4370, 190.4380, 230.1150.

We propose a feed-forward polarization mode dispersion (PMD) compensator with three segments that is capable of compensating for the first- and second-order PMD in a transmission fiber. All control parameters are analytically obtained by the PMD concatenated rules. The influence of all possible perturbations on the compensation is investigated with Monte Carlo simulations. The main advantage of our PMD compensation module over the models reported so far is that it shows excellent robustness to all possible perturbations.

We investigate power-dependent phase-matched four-wave mixing (FWM) in wavelength division multiplexing transmission lines, in which positive and negative dispersion fibers are alternately arranged to manage the dispersion and the dispersion slope. The FWM effect shows power-independent phase matching when the channel power is low. However, it is power dependent at high power. The maximum FWM conversion efficiency is shifted away from the zero channel space in the case of power-dependent phase matching. Optimization of the dispersion system for suppression of the FWM effect is determined. OCIS codes: 060.4370, 190.4380.

Staphylococcus aureus (S. aureus) is one of the most common clinical pathogenic bacteria with strong pathogenicity and usually leads to various suppurative infections with high fatality. Traditional bacterial culture for the detection of S. aureus is prone to diagnosis and antimicrobial treatment delays because of its long-time consumption and low sensitivity. In this study, we successfully developed a quantum dots immunofluorescence biosensor for S. aureus detection. The biosensor combined the advantages of biosensors with the high specificity of antigen-antibody immune interactions and the high sensitivity and stability of quantum dots fluorescence. The results demonstrated that the biosensor possessed high specificity and high sensitivity for S. aureus detection. The detection limit of S. aureus reached 1 × 104 CFU/ml or even 1 × 103 CFU/ml, and moreover, the fluorescence intensity had a significant positive linear correlation relationship with the logarithm of the S. aureus concentration in the range of 103–107 CFU/ml (correlation coefficient R 2 = 0.9731, P = 0.011). A specificity experiment showed that this biosensor could effectively distinguish S. aureus (1 × 104 CFU/ml and above) from other common pathogenic (non- S. aureus) bacteria in nosocomial infections, such as Klebsiella pneumoniae , Pseudomonas aeruginosa , Acinetobacter baumannii and Escherichia coli. Additionally, the whole detection procedure spent only 2 h. In addition, the biosensor in this study may not be affected by the interference of the biofilm or other secretions since the clinical biological specimens are need to be fully liquefied to digest and dissolve viscous secretions such as biofilms before the detection procedure of the biosensor in this study. In conclusion, the biosensor could meet the need for rapid and accurate S. aureus detection for clinical application. [ABSTRACT FROM AUTHOR]

Bidirectional oscillations can be supported in a single photorefractive ring resonator using Ce:BaTiO[sub 3]. We show that two oscillation beams can simultaneously propagate in opposite directions under different geometries. The difference in power between the two oscillation beams can reach two orders of magnitude and their stability depends on the pump beam angle of incidence and the crystal’s configuration. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

This study evaluated the effects of oral mucosal transplantation on epidermal growth factor (EGF) and vascular endothelial growth factor C (VEGF-C) in skin wound repair. Sixty-four rats were randomly separated into group A, B, C and D (16 rats in each group). The right abdomen skin was excised 1, 3, 5 and 7 days after injury, respectively. Oral mucosa of the rat tongue was transplanted to the right abdomen skin. Fourteen days after the healing of the oral mucosa graft, the rat skin full-thickness model was prepared at the transplant site (the study group) and the contralateral site (the control group). Rats in each group were anesthetized and sacrificed at 1, 3, 5 and 7 days after injury. Expression of EGF and VEGF-C in skin tissue was detected by RT-qPCR and ELISA. At 3 days, expression levels of EGF and VEGF-C mRNA and protein in skin tissue were significantly higher than those at 1 day (P<0.05). At 5 days, expression levels of EGF and VEGF-C mRNA and protein in skin tissue were significantly higher than those at 3 days (P<0.05). At 7 days, expression levels of EGF mRNA and protein in skin tissue were significantly lower than those at 5 days (P<0.05), while VEGF-C levels were significantly increased (P<0.05). Expression levels of EGF and VEGF-C mRNA and protein in the skin tissue of the study group were significantly lower than those in the control group at all days (P<0.05). EGF and VEGF-C may be involved in scar formation, and play an important role in the process of skin wound repair. [ABSTRACT FROM AUTHOR]

Presents a study that reported the optical absorption and photorefractive properties of a series of cerium-doped barium titanate crystals. Factors that increase with cerium-doping concentration; Excitation cross section of shallow traps; Factors that contribute to the coupling coefficient.

Presents a study which investigated on the photorefractive diffraction dynamics in a cubic potassium tantalate niobate crystal during writing, reading and erasing. Types of writing beam spot; Description of the diffraction from the first-order and second-order gratings; Influence of the applied dc field on the diffraction intensity during writing; Information on the two photorefractive models.

We report on the experimental investigations of various self-organized structures of soliton molecules in a thulium-doped fiber laser mode-locked by a monolayer MoS2 saturable absorber. With the alteration of cavity parameters, soliton pairs, soliton triplets, and soliton quartets were successively generated, and the short-term and long-term stabilities were tested, exhibiting potential coding alphabet extension from the traditional binary coding scheme to higher coding scheme in fiber communication. Soliton pairs with the phase-difference of $\pi $ , $\pm \pi /2$ , and 0 have been observed systematically in the same thulium-doped fiber cavity, for the first time. Our results might benefit the fundamental physics research of nonlinear dynamics in fiber lasers at the mid-infrared region. [ABSTRACT FROM AUTHOR]

A complete collection of two-soliton bound states exhibiting $\pm \pi {{/ 2, 0}}$ , and $\pi $ phase differences was realized in experiment in a mode-locked erbium-doped fiber laser with a graphene saturable absorber for the first time. The graphene mode-locker possesses modulation depth of about 6% and saturation fluency of about 300 μJ/cm2. By carefully adjusting the polarization controller in the laser cavity under appropriate pumping power, diverse soliton molecules with distinct temporal separations and different phase relationships were obtained. Our experimental findings provide clear evidence that stable soliton pairs with $\pm \pi {{/ 2, 0}}$ , and $\pi $ phase differences can be tightly bounded in fiber lasers as intrinsic attractors, which is independent of cavity details such as the mode-locker we choose. In addition, our numerical simulations unravel the influence of nonlinear properties of a saturable absorber on bound states. It is found that mode-lockers with different modulation depth and/or saturation intensity play a role in interpulse separation and individual pulsewidth of generated soliton molecules while keeping the relative phases between bound solitons unchanged. This paper is instructive to explain current research works on bound states in fiber lasers with sorts of saturable absorbers and is of importance to understand the dissipative dynamics of soliton molecules. [ABSTRACT FROM AUTHOR]

Background: Aimed at underlying the molecular regulatory mechanism and overall biological functions of LINC00511 in tongue squamous cell carcinoma (TSCC).Methods: The expression level of LINC00511 was examined by QRT-PCR. In particular, Tca-8113 cell line was selected for subsequent experiments, in which the expression level of LINC00511 was the most significant. Meanwhile, the effects of LINC00511 on cells proliferation, cell cycle distribution, and invasion of TSCC cells were explored using RNA knockdown tools with CCK-8, flow cytometry analysis, colony formation, and transwell assay. Further, bioinformatic analysis and the dual-luciferase reporter assay both were conducted to invalidate the ceRNAs regulatory mechanism of LINC00511 in TSCC.Results: LINC00511 was obviously upregulated in TSCC tissues and cell lines. Moreover, it was found that LINC00511 served as a competing endogenous RNA (ceRNA) through sponging miR-765 and ultimately modulated the derepression of laminin subunit gamma 2 (LAMC2). The inhibitory effects of miR-765 on TSCC cells proliferation, invasion as well as cell cycle distribution can be restored by the ectopic overexpression of LINC00511. Additionally, the restored capacity of LINC00511 promoted the expression of LAMC2, which was a downstream target of miR-765 and can be negatively regulated by miR-765.Conclusions: A novel molecular axis of LINC00511/miR-765/LAMC2 was investigated to regulate the tumor development of TSCC. LINC00511 promoted the expression of LAMC2 via the ceRNA mechanism of sponging miR-765. The ceRNA regulatory network provided a novel understanding of TSCC pathogenesis and also shed light on exploiting the new field of lncRNA-directed therapy against TSCC. [ABSTRACT FROM AUTHOR]

Benefiting from ultrafast temporal resolution, broadband spectral bandwidth, as well as high peak power, passively mode-locked fibre lasers have attracted growing interest and exhibited great potential from fundamental sciences to industrial and military applications. As a nonlinear system containing complex interactions from gain, loss, nonlinearity, dispersion, etc., ultrafast fibre lasers deliver not only conventional single soliton but also soliton bunching with different types. In analogy to molecules consisting of several atoms in chemistry, soliton molecules (in other words, bound solitons) in fibre lasers are of vital importance for in-depth understanding of the nonlinear interaction mechanism and further exploration for high-capacity fibre-optic communications. In this Review, we summarize the state-of-the-art advances on soliton molecules in ultrafast fibre lasers. A variety of soliton molecules with different numbers of soliton, phase-differences and pulse separations were experimentally observed owing to the flexibility of parameters such as mode-locking techniques and dispersion control. Numerical simulations clearly unravel how different nonlinear interactions contribute to formation of soliton molecules. Analysis of the stability and the underlying physical mechanisms of bound solitons bring important insights to this field. For a complete view of nonlinear optical phenomena in fibre lasers, other dissipative states such as vibrating soliton pairs, soliton rains, rogue waves and coexisting dissipative solitons are also discussed. With development of advanced real-time detection techniques, the internal motion of different pulsing states is anticipated to be characterized, rendering fibre lasers a versatile platform for nonlinear complex dynamics and various practical applications. [ABSTRACT FROM AUTHOR]

In mode-locked thulium soliton fiber lasers, we experimentally observe and numerically confirm the formation of numerous dispersive-wave sidebands, following a bifurcation of the pulse dynamics into a stationary short-period pulsation. These resonant sidebands appear in addition to the Gordon–Kelly sidebands that are formed in the stationary mode-locked regime. The origin of these sidebands is discussed, highlighting their complexity that does not comply with a simple modulation instability analysis. [ABSTRACT FROM PUBLISHER]

We propose and demonstrate a supercontinuum fiber laser source for broadband coherent anti-Stokes Raman scattering (BCARS) microspectroscopy, seeded by a Yb-doped dissipative soliton fiber laser. Smooth continuum Stokes pulses ranging from 1050 to 1312 nm at –20 dB bandwidth are generated in a highly nonlinear fiber from the compact fiber seed, and the corresponding pump pulses are obtained after a narrowband filter centered at 1036 nm. With this fiber laser source, we are able to obtain BCARS spectra in 700–1900 cm–1 spectral range simultaneously with resolution less than 10 cm–1, and show its application in analyzing complex mixture. We also demonstrate the capability of our system in chemical imaging by simultaneously obtaining two two-dimensional CARS images of retinoic acid crystal at Raman shifts of ∼1574 and ∼1162 cm–1, respectively. [ABSTRACT FROM PUBLISHER]

Developments of advanced ultrasonic sensors have made significant impact in structural health monitoring as well as in other various fields including electronics, biomedicine, and geophysics. We describe a cost-effective, highly stabilized, and sensitive ultrasonic sensing system based on a tunable, narrow-linewidth fiber laser locked to resonance of a phase-shifted fiber Bragg grating (PS-FBG). Stable single-longitudinal-mode (SLM) operation of the fiber laser is achieved with a narrow-band self-written FBG that dynamically tracks the lasing wavelength. The SLM fiber laser with 1.48-kHz linewidth and 40-nm tuning range is frequency locked to the PS-FBG resonance in Pound–Drever–Hall configuration for robust and sensitive ultrasonic detection. The sensing system exhibits a high signal-to-noise ratio for ultrasonic detection and further application of the system for lamb wave detection makes it especially attractive for structural health monitoring. [ABSTRACT FROM PUBLISHER]

Examines a double 45 degree-cut mutually pumped phase conjugate mirror which has high phase conjugate reflectivities and is highly insensitive to the alignment of the two incident beams. Overview of the two-beam coupling coefficient; Angular dependent of the phase conjugate reflection; Cause of light scattering and the loss of the incident.