Instantaneous frequency measurement based on photonic compressive sensing with sub-Nyquist pseudo-random binary sequences.

We propose a novel, to the best of our knowledge, approach to realizing instantaneous frequency measurement with ultrahigh measurement bandwidth, which utilizes three-channel photonic compressive sensing (CS) with sub-Nyquist pseudo-random binary sequences (PRBSs). In each CS channel, an alias frequency is recovered due to the sub-Nyquist property of the applied PRBS. A frequency identification algorithm is employed to determine the frequency of the signal under measurement according to the three alias frequencies. The proposed approach significantly reduces the bit rate of the applied PRBSs and the sampling rate required by the digitizers in CS. A proof-of-concept experiment for measuring frequency in the Ku band is demonstrated using PRBSs at 1 Gb/s and digitizers with a sampling rate of 250 MS/s.

Harmonic active mode-locking optoelectronic oscillator with suppressed supermode noise based on pulse intensity feedback.

A harmonic active mode-locking optoelectronic oscillator (HAML-OEO) with pulse intensity feedback is proposed and experimentally demonstrated. It is capable of generating microwave pulses characterized by suppressed supermode noise, uniform intensity, and tunable repetition rates. Unlike traditional HAML-OEOs, active mode-locking and pulse intensity feedback are simultaneously achieved through the use of a dual-drive Mach-Zehnder modulator (DDMZM). By synchronously feeding back the generated microwave pulses to the DDMZM, each pulse undergoes a loss proportional to its intensity, facilitating pulse intensity equalization and supermode noise suppression. In the experiment, intensity-equalized microwave pulse trains with repetition rates of 499 kHz and 998 kHz are generated by the 5th- and 10th-order HAML-OEOs, respectively, with the measured supermode noise suppression ratios exceeding 40 dB.

Photonic generation and transmission for an X-band dual-chirp waveform with frequency multiplication and power-fading compensation.

The generation of an X-band dual-chirp waveform, which is capable of pulse compression, plays an important role in radar, electric warfare, and satellite communication systems. With the development of applications such as multi-static radar, transmission over long distances has attracted considerable attention. In this paper, a photonic system for X-band dual-chirp waveform generation and transmission based on frequency multiplication and power-fading compensation is put forward and experimentally carried out. Based on a compact dual-parallel Mach-Zehnder modulator (DPMZM), the dual-chirp waveforms of 8.6-9.6 GHz and 9.6-10.6 GHz are generated by an RF carrier of 4.8 GHz and transmitted through a 40 km single-mode fiber (SMF) spool. The dispersion-induced power fading of the chirp waveform is compensated for by about 13 dB. The full width at half maximum (FWHM) and the peak-to-sidelobe ratio (PSR) of the compressed pulses are 1 ns and 11.5 dB, respectively. Moreover, the compensation of power fading in the entire X-band is verified to demonstrate the applicability of our system. By flexibly adjusting the bias voltage of the built-in phase shifter, the system can be applied in more scenarios.

The apple autophagy-related gene MdATG10 improves drought tolerance and water use efficiency in transgenic apple plants.

The Loess Plateau is the main apple production area in China; low precipitation is one of the most important factors limiting apple production here. Autophagy is a conserved process in eukaryotes that recycles cell contents or damaged macromolecules. Previously, we identified an autophagy-related gene MdATG10 from apple plants, which was involved in the responses to stressed conditions. In this study, we found that MdATG10 improved the drought tolerance and water use efficiency (WUE) of transgenic apple plants. MdATG10-overexpressing (OE) apple plants were more tolerant of short-term drought stress, as evidenced by their fewer drought-related injuries, compared with wild-type (WT) apple plants. In addition, the WUE of OE plants was higher than that of WT plants under long-term moderate water deficit conditions. The growth rate, biomass accumulation, photosynthetic efficiency, and stomatal aperture were higher in OE plants than in WT plants under long-term moderate drought conditions. During the process of adapting to drought, the expressions of genes involved in the abscisic acid (ABA) pathway were reduced in OE plants to decrease the synthesis of ABA, which helped maintain the stomatal opening for gas exchange. Furthermore, autophagic activity was higher in OE plants than in WT plants, as evidenced by the higher expressions of ATG genes and the greater number of autophagy bodies. In sum, our results suggested that overexpression of MdATG10 improved drought tolerance and WUE in apple plants, possibly by regulating stomatal movement and enhancing autophagic activity, which then enhanced the photosynthetic efficiency and reduced damage, as well as the reactive oxygen species (ROS) accumulation in apple plants.

Photonic angle-of-arrival measurement of microwave signals using a triangular wave.

A novel, to the best of our knowledge, photonics-assisted approach for measuring the angle-of-arrival (AOA) of microwave signals with a large measurement range is proposed. The system utilizes a dual-drive Mach-Zehnder modulator (DDMZM) for signal modulation, followed by an optical filter for sideband selection. The dc port of the DDMZM is fed by a triangular wave to generate a pair of opposite frequency shifts. An intermediate frequency (IF) signal with a periodic phase jump is obtained after photodetection. The AOA of the incoming signals can be estimated by measuring the value of the phase jump. The key novelty of the proposed scheme lies in the application of a triangular wave to shift the frequency of optical signals, which introduces a periodic phase jump to the IF signal. The system incorporates only a single optical channel, largely reducing the system complexity. Experimental results show that an AOA measurement with a range of -70.8° to 70.8° is realized, with errors confined to within ±2°.

Distinguishing the impact of tourism development on ecosystem service trade-offs in ecological functional zone.

Tourism in ecological functional zones (EFZs) is rapidly becoming an increasing trend; however, its impact on ecosystem services remains poorly understood owing to the absence of a consistent quantification framework. This study uses the Taihang Mountains (THM), an EFZ in China, as an example to develop a framework for evaluating the direct and indirect impact pathways of scenic spots on the trade-offs between multiple ecosystem services by identifying the linkages between scenic spot development, socioeconomic change, land use transitions, and ecosystem services. The results show that the continued conversion of agricultural land, grassland, and forest to constructed land around scenic spots in 2000-2020 was accompanied by a decline in water yield (WY) and habitat quality (HQ); while food production (FP), carbon storage (CS), and soil retention (SR) increased. Land use and ecosystem service changes around scenic spots in the THM also exhibited significant spatial gradient effects. In particular, a 10-km buffer area was identified as a distinct "influence zone" where the ecosystem services trade-offs and land use changes were the most pronounced. In 2010, scenic spot revenue was the dominant factor that increased the trade-offs between SR with FP and CS via direct pathways. However, in 2020, the dominant factor was scenic spot level, which shifted the impact toward the relationship between CS and WY and HQ by intensifying the trade-offs to facilitating synergies. This was accomplished in an indirect manner, such as the facilitation of local population growth, industrial restructuring, and infrastructure development. This study reveals the varying effects of scenic spot development via different pathways, thereby providing useful insights for global EFZs to more precisely design policies that can adequately balance human activities with ecosystem services.

Effect of ultraviolet radiation on Beauveria bassiana virulence and development of protective formulations.

Locusta migratoria is a serious agricultural pest in China. Beauveria bassiana is one of the most important pathogens of grasshoppers and locusts. The effects of ultraviolet light were evaluated on the B. bassiana strain BbZJ1. The results showed that 253.7 and 360 nm wavelength UV (Ultra Violet) did not affect the germination of B. bassiana after its recovery from UV treatments. Nevertheless, the virulence of B. bassiana BbZJ1 after its recovery from radiation of UV (253.7 nm) increased. The mortality rates were 85.00% for the BbZJ1 control, was 96.67% for BbZJ1 recovered from radiation of UV (253.7 nm) for 60 min. After treatment with 253.7 nm UV radiation for 60 min, the expression levels of stress-resistant genes BbAlg9 and Bbadh2 in BbZJ1 strain were 2.68 and 2.29 times higher than those in the control group, respectively. Meanwhile, the B. bassiana prepared in 5% groundnut oil showed highest tolerance levels to the ultraviolet radiation. The 5% groundnut oil was the most suitable potential UV-protectant for B. bassiana in terms of cost and availability.

Ku-band analog photonic down-conversion link with coherent I/Q image rejection and digital linearization.

Analog photonic down-conversion links have been widely used in radar, electronic warfare, and satellite communication systems. Aiming at the optimization demands of the link performance, we demonstrate and experimentally verify a Ku-band photonic down-conversion link based on coherent in-phase/quadrature (I/Q) image rejection and digital nonlinear compensation. The image-rejection ratio at 17.5 GHz is measured to be 47 dB. After digital processing, the image intermodulation distortions (MMD) and the intermodulation distortions (IMD3) are suppressed by 18.1 dB and 10.9 dB, respectively. The corresponding spurious-free dynamic range (SFDR) reaches 108.83 dB·Hz2/3.

Coexistence of multiple microcombs in monochromatically pumped Si3N4 microresonators.

We experimentally demonstrate that multiple microcombs can coexist in monochromatically pumped Si3N4 microresonators. By pumping around the mode crossing using a CW laser with mixed polarization, three types of coherent microcombs are generated simultaneously: (i) TE-polarized soliton microcomb; (ii) TM-polarized Turing rolls microcomb; and (iii) cross-phase-modulation-induced TM-polarized microcomb. It is proved that the type-(iii) microcomb shares the same comb line spacing with the type-(i) microcomb although the free spectral ranges of TE and TM modes are different. In addition, a 22.95-GHz signal is extracted from a ∼100-GHz microresonator by heterodyning the TE and TM comb lines, and phase noise analysis reveals their coherence characteristics.

Effect of Bining decoction on gouty nephropathy: a network pharmacology analysis and preliminary validation of gut microbiota in a mouse model.

Background: To use network pharmacology and gut microbiota sequencing to investigate the probable mechanism of Bining decoction (BN) in the treatment of gouty nephropathy (GN). Methods: Firstly, the mechanism of therapeutic effects of BN on GN were collected by integrating network pharmacology. Secondly, the treatment effects of BN against GN in 30 Institute of Cancer Research (ICR) mice were evaluated by performing biochemical tests [uric acid, blood urea nitrogen, and creatinine (UA, BUN, and Cr)] and evaluating the renal weight index. Finally, 16S rRNA sequencing was utilized for elucidating the therapeutical effect of BN in GN. Results: The results of gut microbiota sequencing analysis showed the abundance of Faecalibaculum, Romboutsia, Bifidobacterium, Bacteroides, Odoribacter, Lachnospiraceae NK4A136 group, unclassified_f__Lachnospiraceae, Roseburia, norank_f__Lachnospiraceae, Lactobacillus, Dubosiella, norank_f__Muribaculaceae, and Turicibacter in the BN group had a significant changed between-group comparisons. Using a network pharmacology-related database, 413 active components of BN were identified, as well as 1,085 GN-associated targets. The 118 targets of disease targets and component targets were mapped, of which the top 10 genes were selected. The Kyoto Encyclopedia of Genes and Genomes (KEGG) results showed that 157 pathways were enriched, which was partially consistent with the metabolic pathways of gut microbiota sequencing analysis. Conclusions: Combining 16S rRNA gene sequencing and network pharmacology analysis, similar signaling pathways were followed: "Pathways in cancer" and "Adipocytokine signaling pathway". The results reveal that BN increases the abundance of Turicibacter, regulates the expression of JAK2 in the JAK/STAT pathway, increases the beneficial bacteria Turicibacter associated with intestinal butyric acid, which could enhance the intestinal barrier, and exert anti-inflammatory effects.

Multi-octave linearized RF/photonic link based on orthogonal modulation and optimized demodulation.

In this Letter, we propose and demonstrate a multi-octave linearized analog radio-frequency (RF)/photonic link with orthogonal modulation and optimized demodulation. In our proposed link, the DC-reserved (DCR) digital method is utilized in a parallel Mach-Zehnder-modulator scheme to greatly improve the tolerance to the in-phase/quadrature amplitude imbalance and Q-path DC error, which inevitably exist during digital processing. The fault tolerance and transmission performance of the link are theoretically analyzed and experimentally verified. Compared with the traditional digital-signal-processing method, higher signal-to-distortion ratios can be achieved by the DCR method when the amplitude imbalance and DC errors are considered. As a result, the SFDR2 and SFDR3 (spurious-free dynamic ranges) of our system are measured to be 103.74dB⋅Hz1/2 and 116.31dB⋅Hz2/3, respectively. Furthermore, the linearization of the link is demonstrated by testing the RF signals with various frequencies, which proves the potential in broadband applications.

High-SFDR 100.8km ROF link with optical homodyne detection and genetic-algorithm-assisted digital demodulation.

Radio-over-fiber (ROF) link based on phase modulation and coherent detection has been widely proposed for linear transmission. Nowadays, there are increasing demands for long-distance analog radio-frequency (RF) signal transmission, as radars and broadcast systems. In this paper, a high spurious-free-dynamic-range (SFDR) analog coherent ROF link based on optical homodyne detection and genetic-algorithm-assisted digital demodulation is proposed and experimentally investigated. The ROF link is designed for transmitting RF signals ranging from 500 kHz to 100 MHz over a long-distance fiber under the environment of wide temperature. We test the link performance by transmitting different groups of two-tone signals (580 kHz and 600 kHz, 9 MHz and 10 MHz, 49 MHz and 50 MHz, 99 MHz and 100 MHz) over a 100.8-km single-mode fiber (SMF) under the temperature varying from -40°C to 70°C, the shot-noise-limited SFDR of the link are measured to be greater than 122 dB·Hz2/3.

Frequency-demultiplication OEO for stable millimeter-wave signal generation utilizing phase-locked frequency-quadrupling.

A novel scheme for the generation and stabilization of the millimeter-wave (mmW) signal employing a frequency-demultiplication optoelectronic oscillator (FD-OEO) has been theoretically analyzed and experimentally demonstrated. The FD-OEO can keep sustaining without optical first-order sidebands, which would help to simplify the photonic-assisted frequency multiplication process and provide a wide frequency compensation range for the mmW system simultaneously. The stability of the generated 40-GHz mmW signal reaches 1.38 × 10-12 at the average time of 100s. Besides, the measured single-sideband phase noise of the generated mmW signal exhibits as low as -103 dBc/Hz at 10-kHz offset frequency, maintaining a spurious level of -97 dBc.