A cytological revisit on parthenogenetic Artemia and the deficiency of a meiosis-specific recombinase DMC1 in the possible transition from bisexuality to parthenogenesis.

Although parthenogenesis is widespread in nature and known to have close relationships with bisexuality, the transitional mechanism is poorly understood. Artemia is an ideal model to address this issue because bisexuality and "contagious" obligate parthenogenesis independently exist in its congeneric members. In the present study, we first performed chromosome spreading and immunofluorescence to compare meiotic processes of Artemia adopting two distinct reproductive ways. The results showed that, unlike conventional meiosis in bisexual Artemia, meiosis II in parthenogenic Artemia is entirely absent and anaphase I is followed by a single mitosis-like equational division. Interspecific comparative transcriptomics showed that two central molecules in homologous recombination (HR), Dmc1 and Rad51, exhibited significantly higher expression in bisexual versus parthenogenetic Artemia. qRT-PCR indicated that the expression of both genes peaked at the early oogenesis and gradually decreased afterward. Knocking-down by RNAi of Dmc1 in unfertilized females of bisexual Artemia resulted in a severe deficiency of homologous chromosome pairing and produced univalents at the middle oogenesis stage, which was similar to that of parthenogenic Artemia, while in contrast, silencing Rad51 led to no significant chromosome morphological change. Our results indicated that Dmc1 is vital for HR in bisexual Artemia, and the deficiency of Dmc1 may be correlated with or even possibly one of core factors in the transition from bisexuality to parthenogenesis.

In Operando Monitoring the Stress Evolution of Silicon Anode Electrodes during Battery Operation via Optical Fiber Sensors.

Silicon (Si) anode has attracted broad attention because of its high theoretical specific capacity and low working potential. However, the severe volumetric changes of Si particles during the lithiation process cause expansion and contraction of the electrodes, which induces a repeatedly repair of solid electrolyte interphase, resulting in an excessive consuming of electrolyte and rapid capacity decay. Clearly known the deformation and stress changing at µÎµ resolution in the Si-based electrode during battery operation provides invaluable information for the battery research and development. Here, an in operando approach is developed to monitor the stress evolution of Si anode electrodes via optical fiber Bragg grating (FBG) sensors. By implanting FBG sensor at specific locations in the pouch cells with different Si anodes, the stress evolution of Si electrodes has been systematically investigated, and Δσ/areal capacity is proposed for stress assessment. The results indicate that the differences in stress evolution are nested in the morphological changes of Si particles and the evolution characteristics of electrode structures. The proposed technique provides a brand-new view for understanding the electrochemical mechanics of Si electrodes during battery operation.

Strain measurement with adaptive local feature extraction method based on special fiber OFDR system.

The optical fiber distributed strain sensor based on the optical frequency domain reflectometer (OFDR) preserves its dominant position in short-distance measurement fields with high spatial resolution, such as biomedical treatment, soft robot, etc. However, owing to the weak intensity of the Rayleigh backscattered signal (RBS) in the single-mode fiber (SMF) and complex computation, the large strain changes cannot be precisely and rapidly demodulated by the traditional cross-correlation method. In this work, the OFDR with backscattering enhanced optical fiber (BEOF) is proposed and demonstrated for fast and large strain measurement. By enhancing the RBS amplitude, the signal-to-noise ratio (SNR) is improved, resulting in a higher similarity between the reference signal and test signal, which is beneficial for the expansion of the strain measurement range. Moreover, the adaptive local feature extraction and matching (ALFEM) algorithm is presented and demonstrated, which replaces the traditional cross-correlation method for strain demodulation and fast measurement. On account of the enhancement ratio of BEOF, the dominant characteristic data segment can be extracted from whole wavelength data. In the experiments, the enhancing ratio of BEOF is designed as 10, resulting in the spatial resolution reaches 400µm and the strain measurement range is greatly increased to 4800µÉ›. Further, the effectiveness of the ALFEM algorithm has been verified, in which the strain demodulation time is approximately 25% of that of the traditional method. This scheme fully exploits the enhancement characteristic of the BEOF and is also applicable to the systems based on other types of BEOF, different strain changes and sensing distances.

Low complexity sub-baud rate sampling reception in a bandwidth-limited IM/DD system.

This Letter presents what is to our knowledge a novel approach to reduce the digital signal processing (DSP) complexity in intensity modulation and direct detection (IM/DD) systems, which is critical for short-reach optical communication systems with severe bandwidth limitations. We propose a sub-baud rate sampling reception method utilizing a polyphase feedforward equalizer-based maximum likelihood sequence estimation (PFFE-MLSE), which could operate effectively under a sampling rate of 0.6 samples per symbol. This new architecture eliminates the need for resampling, allowing the adaptive equalizer to operate with significantly reduced complexity-over 60% compared to traditional FFE-MLSE. An offline experiment, transmitting a 100-Gbaud on-off keying (OOK) signal over a 5-km single-mode fiber (SMF) link, demonstrates the feasibility of our approach with bit error ratio (BER) meeting the KP4-forward error correction (KP4-FEC) threshold in the optical back-to-back (OBTB) scenario and 7% hard-decision FEC (HD-FEC) threshold in the 5-km SMF transmission.

Identification and characterization of the Doublesex gene and its mRNA isoforms in the brine shrimp Artemia franciscana.

Doublesex (DSX) proteins are members of the Doublesex/mab-3-related (DMRT) protein family and play crucial roles in sex determination and differentiation among the animal kingdom. In the present study, we identified two Doublesex (Dsx)-like mRNA isoforms in the brine shrimp Artemia franciscana (Kellogg 1906), which are generated by the combination of alternative promoters, alternative splicing and alternative polyadenylation. The two transcripts exhibited sex-biased enrichment, which we termed AfrDsxM and AfrDsxF. They share a common region which encodes an identical N-terminal DNA-binding (DM) domain. RT-qPCR analyses showed that AfrDsxM is dominantly expressed in male Artemia while AfrDsxF is specifically expressed in females. Expression levels of both isoforms increased along with the developmental stages of their respective sexes. RNA interference with dsRNA showed that the knockdown of AfrDsxM in male larvae led to the appearance of female traits including an ovary-like structure in the original male reproductive system and an elevated expression of vitellogenin. However, silencing of AfrDsxF induced no clear phenotypic change in female Artemia. These results indicated that the male AfrDSXM may act as inhibiting regulator upon the default female developmental mode in Artemia. Furthermore, electrophoretic mobility shift assay analyses revealed that the unique DM domain of AfrDSXs can specifically bind to promoter segments of potential downstream target genes like AfrVtg. These data show that AfrDSXs play crucial roles in regulating sexual development in Artemia, and further provide insight into the evolution of sex determination/differentiation in sexual organisms.

0.017†nm, 143†ps passively mode-locked fiber laser based on nonlinear polarization rotation.

Mode-locked lasers with ultra-narrow spectral widths and durations of hundreds of picoseconds can be versatile light sources for a variety of newly emergent applications. However, less attention seems to be given to mode-locked lasers that generate narrow spectral bandwidths. We demonstrate a passively mode-locked erbium-doped fiber laser (EDFL) system that relies on a standard fiber Bragg grating (FBG) and the nonlinear polarization rotation (NPR) effect. This laser achieves the longest reported pulse width (to the best of our knowledge) of 143 ps based on NPR and an ultra-narrow spectral bandwidth of 0.017 nm (2.13 GHz) under Fourier transform-limited conditions. The average output power is 2.8 mW, and the single-pulse energy is 0.19 nJ at a pump power of 360 mW.

Fiber Bragg grating displacement sensor based on synchronous deformation sensing for real-time monitoring of a tunnel lining.

A fiber Bragg grating (FBG) displacement sensor based on synchronous sensing is developed for real-time monitoring of a tunnel lining. The sensing principle and mechanical structure of the proposed sensor are analyzed and simulated, and its sensitization effectiveness and temperature compensation are verified. Equivalent model tests show that the sensor has a good linear sensitivity of 19.48 pm/mm and an excellent precision of 5.13×10-2 m m in the displacement range of 0-25 mm, which is basically consistent with the simulation results. The key traffic parameters of the train were successfully obtained by real-time monitoring of the tunnel lining in a field trial, which shows the superior capability of micro-displacement measurement of the sensor. Furthermore, good stability and excellent creep resistance have also been demonstrated. Our results provide theoretical guidance for the fabrication and package of the FBG displacement sensor, which is valuable for structure health monitoring (SHM) in civil engineering applications.

Monitoring Your Weight-Loss Process Online: The Impacts of Prior Experiences and Online Social Support on Subsequent Weight-Loss Outcome.

Online weight-loss communities (OWCs) have become increasingly popular for weight management; they enable individuals to monitor (i.e. self-monitoring) and discuss (i.e. social interaction) their weight-loss experiences. This study investigates the relationship between prior weight-loss experiences (success and failure), online social support, and subsequent weight-loss outcome in the context of OWCs and based on self-determination theory. We collected the data of 1465 users from one popular OWC and deployed two logit regression models to estimate the effects of prior weight-loss experiences on subsequent weight-loss success as well as the moderating role of social support. The results revealed that prior successful weight-loss experiences were positively related to subsequent weight-loss outcome, while the relationship between prior failed weight-loss experiences and subsequent weight-loss outcome was negative. Meanwhile, online social support can not only be positively related to subsequent weight-loss outcome, but also buffer the negative role of prior failed weight-loss experiences. Nevertheless, social support had no significant moderating role in the relationship between prior successful weight-loss experiences and subsequent weight-loss outcome. This study contributes to the literature on prior experiences and online social support in the context of OWCs and provides valuable insights to improve participants' engagement and their weight-loss success.

Diffraction characteristics of radiated tilted fiber grating and its spectrometer application.

We have numerically and experimentally presented the diffraction characteristics of radiated tilted fiber grating (RTFG) in terms of the spectrum, bandwidth, degree of polarization, angular dispersion, and temperature crosstalk. The theoretical and experimental results have shown that the polarization property, bandwidth, and dispersion of RTFG highly depended on the tilt angle of RTFG, and the RTFG has ultra-low temperature crosstalk. We have simulated the transmission spectrum of the RTFG with different tilt angles (25°, 31°, 38°, 45°, and 54°), in which the results show that the larger tilt angle has the wider bandwidth. The RTFGs with the tilt angle of 25°, 31°, 38°, 45°, and 54° have the 3dB bandwidth of 110 nm, 144 nm, 182 nm, 242 nm, and 301 nm, respectively. Besides, the degree of polarization (DOP) of the radiated light from RTFG with the different tilt angles are 0.876, 0.944, 0.967, 0.998, and 0.970, respectively, and the RTFG has the maximum DOP at the tilt angle of 45°, which could be used as single-polarization diffraction device. The experimental results show that with further increase or decrease of the tilt angle, the DOP of radiated light of RTFG would decrease. Both the theoretical and experimental results show that the smaller tilt angle could greatly improve the diffraction angular dispersion of RTFG, in which the 25°, 31°, 38°, and 45° RTFG have the angular dispersion of 0.2288 °/nm, 0.1026 °/nm, 0.0714 °/nm, and 0.0528 °/nm, respectively. Due to the broad working bandwidth, the diffraction angles of RTFG have ultra-low temperature crosstalk, where -0.00042, -0.00054, -0.00064, and -0.00099 degree / °C at the tilt angle of 25°, 31°, 38°, and 45°. Finally, we have demonstrated a miniaturized spectrometer integrated by a 25° RTFG, which has a high spectral resolution of 0.08 nm. The proposed RTFG would be an ideal in-fiber diffraction device and widely applied in spectral analysis, space optical communication, and Lidar areas.

High-precision distributed detection of rail defects by tracking the acoustic propagation waves.

Nowadays, early defect detection plays a significant role for the railway safety warning. However, the existing methods cannot satisfy the requirements of real-time and high-precision detection. Here, a high-precision, distributed and on-line method for detecting rail defect is proposed and demonstrated. When a train goes through defects, the instantaneous elastic waves will be excited by the wheel-rail interaction, which will further propagate along railway tracks bidirectionally. Through mounting the backscattering enhanced optical fiber on the railway as sensors, the fiber optic distributed acoustic sensing system can record the propagation trace precisely. Further, the acoustic propagation fitting method is applied onto the propagation data to detect and locate defects along the long-distance railway. Especially, the dual-frequency joint-processing algorithm is proposed to improve the location accuracy. The field test proves that multiple defects along the railway can be successfully identified and located with a standard deviation of 0.314m. To the best of our knowledge, this work is the first report of distributed rail defect detection, which will bring a breakthrough for high-precision structural damage detection in the infrastructures such as the railway, pipeline and tunnel.

Spatio-temporal joint oversampling-downsampling technique for ultra-high resolution fiber optic distributed acoustic sensing.

In order to suppress the noise of the coherent fiber distributed acoustic sensing (DAS) system, the spatio-temporal joint oversampling-downsampling technique is proposed. The spatial oversampling is used for artificially dense sampling, whose spacing is far less than the target spatial resolution. Then the spatial downsampling performed by the average of multiple differential sub-vectors is utilized to reduce the influence of noise vectors, which could completely eliminate the interfere fading without increasing any system complexity and introducing any crosstalk. Meanwhile, the temporal oversampling-downsampling is analyzed from the perspective of theory and simulation, demonstrating that the noise floor will decrease with the increase of downsampling coefficient. The temporal oversampling is carried out to expand the noise distribution bandwidth and ensure the correct quantization of the noise frequency. Then the temporal downsampling of differential phase reconstruction is utilized to recover the target bandwidth and reduce the out-of-band noise. The experimental results prove that the noise floor is inversely correlated with the spatiotemporal downsampling factors. The strain resolution of the DAS system with the proposed scheme can reach 2.58pε/√Hz@100Hz-500Hz and 9.47pε/√Hz@10Hz under the condition of DC-500Hz target bandwidth, as well as the probability of the large-noise sensing channels is greatly reduced from 44.32% to 0%. Moreover, the demodulated SNR of dynamic signal is improved by 20.8dB compared with the traditional method. Without any crosstalk, the noise floor is optimized 8dB lower than the averaging technique. Based on the proposed method, the high-performance DAS system has significant competitiveness in the applications with the demand of high-precision and high-sensitivity, such as passive-source seismic imaging and VSP exploration.

Meta-learning-enabled accurate OSNR monitoring of directly detected QAM signals with one-shot training.

We experimentally demonstrate meta-learning-enabled accurate optical signal-to-noise ratio (OSNR) monitoring of directly detected 16QAM signals with extremely few training data. When one-shot training, where one amplitude histogram (AH) for each OSNR value includes only 2000 data samples, is implemented for a 16QAM signal within a variable OSNR range of 15-24 dB, the experimental root mean squared error (RMSE) of the retraining technique is 1.53 dB. For transfer learning from the 16QAM simulation to the experimentally generated AH, the RMSE can be reduced to 1.11 dB. In comparison with both the retraining and transfer learning techniques, the RMSE of meta-learning-enabled OSNR monitoring can be further reduced by 42.8% and 22.3%, respectively. In order to reach the optimal accuracy with an RMSE of 0.66 dB, the meta-learning technique requires only 15 AHs for each OSNR value to be monitored, while the retraining and the transfer learning techniques need 20 and 25 AHs, respectively.

In-fiber duplex optical antenna and its programmable spectral filter application: publisher's note.

This publisher's note contains corrections to Opt. Lett.47, 4937 (2022)10.1364/OL.468940.

In-fiber duplex optical antenna and its programmable spectral filter application.

In this Letter, we have proposed an in-fiber duplex optical antenna based on a 45° radiated titled fiber grating (RTFG), in which the 45° RTFG not only radiates the light from the fiber core to the free space, but also harvests the light from the free space back into the fiber core. Using the finite difference time domain method, we have theoretically analyzed the light recoupling efficiency of the RTFG. The simulated results have shown that the RTFG-based optical antennas have a maximum coupling efficiency of 10%. The recoupling wavelength and efficiency are related to the grating period and horizontal incidence angle. Furthermore, we demonstrate a programmable spectral filtering system based on the 45° RTFG antennas, which could achieve filtering with arbitrary spectral shapes. The spectral resolution is 0.4 nm and the insertion loss is around 20 dB. The proposed programmable spectral filtering system has a compact structure compared with the traditional filter.

Multi-channel parallel ultrasound detection based on a photothermal tunable fiber optic sensor array.

A multi-channel parallel ultrasound detection system based on a photothermal tunable fiber optic sensor array is proposed. The resonant wavelength of the ultrasound sensor has a quadratic relationship with the power of a 980-nm heating laser. The maximum tuning range is larger than 15 nm. Through photothermal tuning, the inconsistent operating wavelengths of the Fabry-Perot (FP) sensor array can be solved, and then a multiplexing capacity of up to 53 can be theoretically realized, which could greatly reduce the time required for data acquisition. Then, a fixed wavelength laser with ultra-narrow linewidth is used to interrogate the sensor array. The interrogation system demonstrates a noise equivalent pressure (NEP) as low as 0.12 kPa, which is 5.5-times lower than the commercial hydrophone. Furthermore, a prototype of a four-channel ultrasound detection system is built to demonstrate the parallel detection capability. Compared with the independent detection, the SNR of parallel detection does not deteriorate, proving that the parallel detection system and the sensor array own very low cross talk characteristics. The parallel detection technique paves a way for real-time photoacoustic/ultrasound imaging.

Wavelength-tunable noise-like fiber laser based on PbS quantum dot saturable absorber film.

A wavelength-tunable noise-like pulse (NLP) erbium-doped fiber laser incorporating PbS quantum dot (QD) polystyrene (PS) composite film as a saturable absorber (SA) is experimentally demonstrated. The wavelength tuning is implemented via a Lyot filter consisting of a segment of polarization-maintaining fiber (PMF) and a 45° tilted fiber grating. By adjusting the polarization state of the ring cavity, the laser can deliver NLP with a continuous wavelength-tunable range from 1550.21 to 1560.64 nm. During continuous wavelength tuning, the output power varies between a range of 30.88-48.8 mW. Worthwhile noting is that the output power of 48.8 mW is the reported highest output power for wavelength-tunable NLP operation in an erbium-doped fiber laser using composite film as a saturable absorber.

Fiber-optic airflow velocity sensing method based on a 45° tilt fiber grating combined with a single-walled carbon nanotube coated fiber.

We propose and experimentally demonstrate an airflow velocity sensing method based on a 45° tilt fiber grating (TFG) that is combined with a single-walled carbon nanotube (SWCNT) coated fiber Bragg grating (FBG). The principle behind which is to produce a dynamic thermal equilibrium between the light heating and the airflow cooling. For the first time, to the best of our knowledge, a 45°-TFG is used as the heating element for the hot-wire anemometer. By diagnosing the Bragg wavelength of the SWCNT coated FBG, the temperature variations of the sensing fiber are measured with respect to the airflow velocities, which vary from 0 to 1 m/s. Moreover, under low light power consumption of 20 mW, the proposed sensor is shown to have good performance. Experimental results reveal that the sensitivity of the sensor increases with the heating pump. Due to the advantages of its simplicity and reliability, alongside its high photo-thermal conversion efficiency, this technique has excellent potential for future use in remote monitoring with airflow velocity sensing.

Generation of 64-fs L-band stretched pulses from an all-fibre Er-doped laser.

We demonstrate an L-band all-fibre erbium-doped laser mode locked by nonlinear polarisation rotation and working in the stretched-pulse regime. The use of a single segment of gain fibre with appropriate length and dispersion and a Brewster fibre grating optimised for the L band as an in-fibre polariser enables the generation of pulses at 1.59-µm central wavelength, which can be linearly compressed to 64-fs duration. Numerical simulations of the laser model support our experimental findings. Our laser design gives a route towards low-cost and low-complexity fibre-integrated laser sources for applications requiring L-band ultrashort pulses.

High resolution and large sensing range liquid level measurement using phase-sensitive optic distributed sensor.

Liquid level sensor with large sensing range and high-resolution is essential for the application of industry monitoring. In this work, a distributed optical fiber liquid level sensor is proposed and demonstrated based on phase-sensitive optical time domain reflectometry (φ-OTDR). In the basic of the thermal optic effect, the temperature change will induce the fluctuation of the effective refractive indexes of the fiber core, as well as the fluctuation of the optical path of the light transmitting in the fiber. Therefore, the φ-OTDR can detect the liquid level with a large measurement range by interrogating the phase information along the fiber due to the temperature difference between the liquid and air. Further, the scattering enhanced optical fiber (SEOF) is used as the sensing fiber to improve the signal to noise ratio (SNR) of the phase signal. Moreover, a high sensitivity liquid level sensing head by wrapping the SEOF on a heat conductive cylinder is designed and optimized to improve the sensing resolution. In the experiment, the proposed distributed liquid level sensor presents a high sensitivity of 73.4 rad/mm, corresponding to a competitive liquid level resolution of 142µm based on the noise floor of 10.4 rad within 160 s. The field test validates a large sensing range of 20 cm which is limited by the cylinder length, while a potential sensing range could reach 320 m with the sensing fiber of 40 km, proving a dynamic range of 127.1 dB. The proposed liquid level sensor with large dynamic range and high sensing resolution can benefit potential application in smart industry platforms and biomedicine monitoring.

Impacts of social distancing on the spread of infectious diseases with asymptomatic infection: A mathematical model.

Social distancing can be divided into two categories: spontaneous social distancing adopted by the individuals themselves, and public social distancing promoted by the government. Both types of social distancing have been proved to suppress the spread of infectious disease effectively. While previous studies examined the impact of each social distancing separately, the simultaneous impacts of them are less studied. In this research, we develop a mathematical model to analyze how spontaneous social distancing and public social distancing simultaneously affect the outbreak threshold of an infectious disease with asymptomatic infection. A communication-contact two-layer network is constructed to consider the difference between spontaneous social distancing and public social distancing. Based on link overlap of the two layers, the two-layer network is divided into three subnetworks: communication-only network, contact-only network, and overlapped network. Our results show that public social distancing can significantly increase the outbreak threshold of an infectious disease. To achieve better control effect, the subnetwork of higher infection risk should be more targeted by public social distancing, but the subnetworks of lower infection risk shouldn't be overlooked. The impact of spontaneous social distancing is relatively weak. On the one hand, spontaneous social distancing in the communication-only network has no impact on the outbreak threshold of the infectious disease. On the other hand, the impact of spontaneous social distancing in the overlapped network is highly dependent on the detection of asymptomatic infection sources. Moreover, public social distancing collaborates with infection detection on controlling an infectious disease, but their impacts can't add up perfectly. Besides, public social distancing is slightly less effective than infection detection, because infection detection can also promote spontaneous social distancing.