Low-loss microwave photonic switching for satellite communication.

For traditional switching architecture, packet switching performs fine granularity data packet forwarding, but its digital signal processing (DSP) has high power consumption (PC). All-optical switching provides rapid exchange of wavelength resources, which has coarse granularity. In scenarios where the PC is limited, such as broadband satcom, a switching architecture with lower PC and finer granularity than optical switching would be useful. In this paper, we propose a novel, to the best of our knowledge, low-loss microwave photonic switching architecture that can exchange subband signals across beams and frequency bands. The switching process is realized by exchanging optical carriers instead of payload signals, which does not degrade the signal power, guaranteeing the signal-to-noise ratio (SNR). We conducted a proof-of-concept experiment of 2 × 2 switching with two 1.2-GBaud quadrature phase-shift keying (QPSK) signals; an error vector magnitude (EVM) of or less than 13.87% is realized after forwarding. The proposed system has the advantages of low PC, high SNR, and fine granularity, and is very promising for flexible forwarding in future satcom systems.

Efficacy and Safety of Ferric Citrate on Hyperphosphatemia among Chinese Patients with Chronic Kidney Disease Undergoing Hemodialysis: A Phase III Multicenter Randomized Open-Label Active-Drug-Controlled Study.

INTRODUCTION: Hyperphosphatemia in chronic kidney disease (CKD) patients is positively associated with mortality. Ferric citrate is a potent phosphorus binder that lowers serum phosphorus level and improves iron metabolism. We compared its efficacy and safety with active drugs in Chinese CKD patients with hemodialysis. METHODS: Chinese patients undergoing hemodialysis were randomized into two treatment groups in a 1:1 ratio, receiving either ferric citrate or sevelamer carbonate, respectively, for 12 weeks. Serum phosphorus levels, calcium concentration, and iron metabolism parameters were evaluated every 2 weeks. Frequency and severity of adverse events were recorded. RESULTS: 217 (90.4%) patients completed the study with balanced demographic and baseline characteristics between two groups. Ferric citrate decreased the serum phosphorus level to 0.59 ± 0.54 mmol/L, comparable to 0.56 ± 0.62 mmol/L by sevelamer carbonate. There was no significant difference between two groups (p > 0.05) in the proportion of patients with serum phosphorus levels reaching the target range, the response rate to the study drug, and the changes of corrected serum calcium concentrations, and intact-PTH levels at the end of treatment. The change of iron metabolism indicators in the ferric citrate group was significantly higher than those in the sevelamer carbonate group. There are 47 (40.5%) patients in the ferric citrate group, and 26 (21.3%) patients in the sevelamer carbonate group experienced drug-related treatment emergent adverse events (TEAEs); most were mild and tolerable. Common drug-related TEAEs were gastrointestinal disorders, including diarrhea (12.9 vs. 2.5%), fecal discoloration (14.7 vs. 0%), and constipation (1.7 vs. 7.4%) in ferric citrate and sevelamer carbonate group. CONCLUSION: Ferric citrate capsules have good efficacy and safety in the control of hyperphosphatemia in adult patients with CKD undergoing hemodialysis. Efficacy is not inferior to sevelamer carbonate. The TEAEs were mostly mild and tolerated by the patients.

Broadband dual-channel channelizer based on a microwave photonic power tunable image rejection down-conversion.

Radiofrequency (RF) channelization has potential high frequency and wideband advantages in frequency-domain channel segmentation and down-conversion reception. In this paper, we propose a compact dual-channel channelizer that can process high-frequency wideband signals. It uses double-polarization double-sideband electro-optic modulation and Hartley structure photoelectric conversion to realize down-conversion channelization of the high-frequency wideband signal. The power matching between two polarization signals can be realized by controlling the modulator bias, so the crosstalk between the two output signals can be suppressed. The proposed channelizer has a compact structure since the electro-optic modulation is based on one single laser and one single integrated modulator. No filters are used in the structure, contributing to a very wide RF operation bandwidth and low constraints of laser wavelength. In the experiment, the single frequency signal pairs from 9 GHz to 15 GHz can achieve an inter-channel image rejection ratio of 53 dB. Furthermore, the channelizer slices multi-octave bandwidth quadrature phase shift keying (QPSK) signals up to 16 GHz with the wideband isolation higher than 10 dB and outputs them to two channels in parallel. The error vector magnitudes (EVM) of 9-17 GHz and 18-26 GHz band QPSK signals are guaranteed to be under 23.58% after channelized separation. To the best of our knowledge, the proposed channelizer provides high inter-channel interference suppression at dual-band adjacent signals with 8 GHz bandwidth for the first time. Therefore, the proposed channelizer has great application value for the reception and processing of millimeter signals in the future.

Light Emitting Diodes Irradiation Regulates miRNA-877-3p to Promote Cardiomyocyte Proliferation.

Mammalian cardiomyocytes (CMs) maintain a low capacity for self-renewal in adulthood, therefore the induction of CMs cycle re-entry is an important approach to promote myocardial repair after injury. Recently, photobiomodulation (PBM) has been used to manipulate physiological activities of various tissues and organs by non-invasive means. Here, we demonstrate that conditioned PBM using light-emitting diodes with a wavelength of 630 nm (LED-Red) was capable of promoting the proliferation of neonatal CMs. Further studies showed that low-power LED-Red affected the expression of miR-877-3p and promoted the proliferation of CMs. In contrast, silencing of miR-877-3p partially abolished the pro-proliferative actions of LED-Red irradiation on CMs. Mechanistically, GADD45g was identified as a downstream target gene of miR-877-3p. Conditioned LED-Red irradiation also inhibited the expression of GADD45g in neonatal CMs. Moreover, GADD45g siRNA reversed the positive effect of LED-Red on the proliferation of neonatal CMs. Taken together, conditioned LED-Red irradiation increased miR-877-3p expression and promoted the proliferation of neonatal CMs by targeting GADD45g. This finding provides a new insight into the role of LED-Red irradiation in neonatal CMs biology and suggests its potential application in myocardial injury repair.

Generation of rotational orbital angular momentum beams in the radio frequency based on an optical-controlled circular antenna array.

The orbital angular momentum (OAM) has been widely used in the wireless short-range communication system, but for long-distance communication, the huge difficulty of beam receiving is a great challenge. In this paper, to overcome this challenge, a generation system of radio-frequency rotational orbital angular momentum (RF-ROAM) beams based on an optical-controlled circular antenna array (CAA) is proposed. The ROAM beam is an OAM beam rotating at a certain speed around the beam axis. According to the rotational Doppler effect, the rotation of the OAM beam will induce a frequency shift proportional to the OAM mode and the rotation speed. Thereby, by rotating an OAM beam at a fixed speed scheduled in advance in the transmitting end, the beam can be mode-distinguished by just detecting the frequency shift without receiving the whole wavefront vertical to the beam axis in the receiving end. This provides a partial reception scheme for the OAM-based wireless communication system. The generation system of RF-ROAM beams is proposed and constructed, and the proof-of-concept experiment is performed. In the system, the optical-controlled CAA is constructed to generate the general RF-OAM beam, the optical signal processor (OSP) is employed to control the phase shifts to further control the OAM mode, and the signal with time-varying phase is generated as the rotation factor to control the rotation speed. In the experiment, the RF-ROAM beams with different mode and mode combination are generated and successfully measured by detecting the frequency shift of the signal received in a fixed point.

Analog radio of fiber link of 2-Gbaud OOK/BPSK radio frequency-orbital angular momentum beam transmission over 19.4 km.

The 5G mobile communication system provides ultrareliable, low-latency communications at up to 10 Gbps. However, the scale and power consumption of 5G is tremendous owing to a large number of antenna drivers required by the massive multiple-input multiple-output technique. The 6G system will require an architectural paradigm shift to resolve this problem. In this study, we propose an analog RoF downlink scheme for 6G wireless communications. The upcoming oversized base station problem is solved using photonics techniques. The antennas are driven together within the optical domain at a centralized station. The proposed system uses orbital angular momentum (OAM) beams as the generated space-division-multiplexing beams. An RF-OAM beam has a weak coupling effect between different modes, which will dramatically decrease the complexity of the signal processing. In our proof-of-concept experiment, the generated RF-OAM beam was shown to carry a 2-Gbaud OOK/BPSK signal in the Ku-band. Signals were transmitted over a 19.4-km RoF link without dispersion-induced power fading. In addition, by switching the OAM beams, a two-dimensional direction scanning was achieved.

Data-aided channel equalization scheme for FAST radio over fiber transmission system.

The Five-hundred-meter Aperture Spherical radio Telescope (FAST) located in Guizhou, China, is a very sensitive single dish telescope. Due to the large size of the telescope, optical fiber is used for the transmission of the 3-km astronomical signal from the telescope to the signal processing center. The optical fibers are suspended in the air above the telescope reflector, very easy to slide when the telescope feed cabin moves, resulting in phase drifts for the transmission signal. This phase drift has a negative impact on the observation mode of very long baseline interferometry, and can be compensated by the frequency transfer system in the FAST. In this manuscript, we propose a new phase drift compensation scheme, which is denoted as data-aided channel equalization scheme. The proposed scheme is based on a hypothesis of linear phase relationship between different wavelengths in the same optical fiber, and uses the channel response information of the data-aided channel to conduct signal recovery for the astronomical signal channel. Not only the phase drift, but also the frequency-dependent distortion of the broadband transmission link can be compensated. The proposed scheme has simple transmission structure, and the function part is well modularized, so that the Astronomer users can easily turn it on or off. In the proof-of-concept experiments, the estimation deviation can be significantly reduced by estimated channel responses averaging over training sequence repetitions, showing very high accuracy of the astronomical signal channel estimation.

Loss of m6A methyltransferase METTL3 promotes heart regeneration and repair after myocardial injury.

AIMS: N6-Methyladenosine (m6A), one of the important epigenitic modifications, is very commom in messenger RNAs (mRNAs) of eukaryotes, and has been involved in various diseases. However, the role of m6A modification in heart regeneration after injury remains unclear. The study was conducted to investigate whether targeting methyltransferase-like 3 (METTL3) could replenish the loss of cardiomyocytes (CMs) and improve cardiac function after myocardial infarction (MI). METHODS AND RESULTS: METTL3 knockout mouse line was generated. A series of functional experiments were carried out and the molecular mechanism was further explored. We identified that METTL3, a methyltransferase of m6A methylation, is upregulated in mouse hearts after birth, which is the opposite of the changes in CMs proliferation. Furthermore, both METTL3 heterozygous knockout mice and administration of METTL3 shRNA adenovirus in mice exhibited CMs cell cycle re-entered, infract size decreased and cardiac function improved after MI. Mechanically, the silencing of METTL3 promoted CMs proliferation by reducing primary miR-143 (pri-miR-143) m6A modificaiton, thereby inhibiting the pri-miR-143 into mature miR-143-3p. Moreover, we found that miR-143-3p has targeting effects on Yap and Ctnnd1 so as to regulate CMs proliferation. CONCLUSION: METTL3 deficiency contributes to heart regeneration after MI via METTL3-pri-miR-143-(miR-143)-Yap/Ctnnd1 axis. This study provides new insights into the significance of RNA m6A modification in heart regeneration.

YAP/TEAD3 signal mediates cardiac lineage commitment of human-induced pluripotent stem cells.

Cardiomyocytes differentiated from human-induced pluripotent stem cells (hiPSCs) hold great potential for therapy of heart diseases. However, the underlying mechanisms of its cardiac differentiation have not been fully elucidated. Hippo-YAP signal pathway plays important roles in cell differentiation, tissue homeostasis, and organ size. Here, we identify the role of Hippo-YAP signal pathway in determining cardiac differentiation fate of hiPSCs. We found that cardiac differentiation of hiPSCs were significantly inhibited after treatment with verteporfin (a selective and potent YAP inhibitor). During hiPSCs differentiation from mesoderm cells (MESs) into cardiomyocytes, verteporfin treatment caused the cells retained in the earlier cardiovascular progenitor cells (CVPCs) stage. Interestingly, during hiPSCs differentiation from CVPC into cardiomyocytes, verteporfin treatment induced cells dedifferentiation into the earlier CVPC stage. Mechanistically, we found that YAP interacted with transcriptional enhanced associate domain transcription factor 3 (TEAD3) to regulate cardiac differentiation of hiPSCs during the CVPC stage. Consistently, RNAi-based silencing of TEAD3 mimicked the phenotype as the cells treated with verteporfin. Collectively, our study suggests that YAP-TEAD3 signaling is important for cardiomyocyte differentiation of hiPSCs. Our findings provide new insight into the function of Hippo-YAP signal in cardiovascular lineage commitment.

All-optical generation of binary phase-coded microwave pulses without baseband components based on a dual-parallel Mach-Zehnder modulator.

In this paper, we propose an all-optical system for the generation of binary phase-coded microwave pulses without baseband components. The scheme is based on a dual-parallel Mach-Zehnder modulator (DPMZM). By properly applying the coding signals and the microwave signals to the precisely biased DPMZM, accurate π phase shift binary phase-coded microwave pulses without baseband components can be generated. The proposed system has an extremely simple and stable all-optical structure, leading to a large frequency tuning range and a high signal quality. The operation of the system is very easy. The generation of the 2-Gbit/s 14-GHz and 4-Gbit/s 16-GHz binary phase-coded microwave pulses under different coding signal amplitudes and microwave carrier powers are experimental verified. The results show that the proposed binary phase-coded microwave pulses generation system has high quality and performance.

Photonic generation of background-free binary and quaternary phase-coded microwave pulses based on vector sum.

A photonic microwave phase-coded pulse generator is proposed and experimentally demonstrated based on the principle of vector sum. The key component of the proposed pulse generator is an integrated polarization-division multiplexing Mach-Zehnder modulator (PDM-MZM) and a 90° hybrid coupler. By properly setting the data sequences applied to the specially biased PDM-MZM, binary and quaternary phase-coded microwave pulses (PCMPs) that are free from the background signals can be generated. Since no filters and polarization adjustment are involved, the proposed pulse generator is characterized by a simple structure, low-loss, flexible frequency tunability and high long-term stability. The experimental results show that background-free 4 Gb/s Barker and Frank PCMPs at 18 GHz and 2 Gb/s Barker and Frank PCMPs at 24 GHz are successfully generated. The calculated pulse compression ratio and peak-to-side lobe ratio are in good agreement with the theoretical values.

Chromatic dispersion immune microwave photonic phase shifter based on double-sideband modulation.

A chromatic dispersion (CD) immune microwave photonic phase shifter (MPPS) based on double-sideband (DSB) modulation is proposed and demonstrated. An optical spectrum processor introduces the phase shift to the MPPS. The DSB signals along two orthogonal polarizations are demodulated to two RF signals with both quadrature amplitude and phase items, transferring the CD-induced power fading to the phase item of the synthetic RF signals. Experimental results show that the RF signals over 14-25 GHz obtain random phase shift in 360° range without a power fading point (PFP) after passing through a dispersion compensation fiber with CD of -331 ps/nm. The phase variation and power variation of the phase-shifted signal are <±5.7° and <±0.9 dB, respectively, at the original PFP at 16 GHz.

Broadband chromatic-dispersion-induced power-fading compensation for radio-over-fiber links based on Hilbert transform.

A Hilbert-transform-based broadband chromatic dispersion (CD) compensation scheme for radio-over-fiber links is proposed and experimentally demonstrated. By constructing a Hilbert transform path, CD-induced phase shifts, which initially lead to periodic power fading of the output RF signals, are transferred to the phases of the RF signals. As a result, the powers of the output RF signals are free from the effect of CD in a broadband frequency range. Experimental results show that a flat normalized amplitude-frequency response is actualized within 2-24 GHz, with only 3.02 dB/4.27 dB power fluctuation after transmission over an equivalent of a 38.6 km/43.6 km single-mode fiber. Besides, compared with a conventional dispersive path, the proposed CD compensation scheme significantly improves the third-order spurious-free dynamic range by 23.60 dB.

Equivalent photonic switch for microwave frequency shift keying signal generation.

A photonic microwave frequency shift keying (FSK) signal generator is proposed and experimentally demonstrated based on an equivalent photonic switch (EPS). The EPS is constructed using a polarization-multiplexing dual-drive Mach-Zehnder modulator (PM-DMZM). By properly controlling the data sequences and RF signals applied to the PM-DMZM, microwave FSK signals with flexible frequency intervals can be obtained. The proposed FSK signal generator features the advantages of a simple structure, low loss, good stability, and great frequency tunability. In addition, the proposed setup can also be easily reconfigured to generate microwave amplitude shift keying and phase shift keying signals. The experimental results show that 2 Gb/s at 5/14 GHz and 1 Gb/s at 6/20 GHz microwave FSK signals are successfully generated, after transmission over 5 km single-mode fiber. The required received optical power at 7% forward error correction threshold is only -14.48 dBm.

Optical network solution to the synchronization of distributed coherent aperture radar.

Distributed coherent aperture radar (DCAR) is an important direction for next-generation radar due to its high sensitivity. The challenge to realize DCAR is the synchronization among geographically distributed radar units. We propose an optical network for DCAR synchronization. The proposed network achieves functions of phase-coded pulse generation, time synchronization, and phase synchronization with the help of microwave photonics techniques. Proof-of-concept experiments are conducted in fiber and space transmission scenarios. The combined radar beams have negligible energy loss when synchronization is achieved.

2D optically controlled radio frequency orbital angular momentum beam steering system based on a dual-parallel Mach-Zehnder modulator.

An optically controlled system for generating and continuously steering radio frequency (RF) signals with double orbital angular momentum (OAM) modes is proposed and experimentally demonstrated. The optical carrier's utilization efficiency can be doubled through the distinct electro-optical modulation, which is based on two single-sideband modulation operations on a single optical carrier through a customized dual-parallel Mach-Zehnder modulator. A constructive antenna phase feeding method of a circular antenna array for collectively forming and steering an OAM radio beam is proposed and illustrated. A proof-of-concept experiment is conducted to generate and steer a dual-mode RF-OAM beam to two different two-dimensional (2D) directions, independently and simultaneously. One 17 GHz OAM beam with mode L=1 is continuously steered to 2D directions (:, 0°, 0°), (:, 0°, 1.70°), (:, 0°, 3.87°), (:, 0°, 6.17°), and(:, 0°, 7.80°), with vortex properties, where ":" means "any value of." Meanwhile, the 19 GHz OAM beam with mode L=-1 carried is steered from (:, 0°, 0°) to (:, 0°, -6.72°), and the constellations are obtained successfully.

Anti-dispersion phase-tunable microwave mixer based on a dual-drive dual-parallel Mach-Zehnder modulator.

An optically-controlled phase-tunable microwave mixer based on a dual-drive dual-parallel Mach-Zehnder modulator (DDDP-MZM) is proposed, which supports wideband phase shift and immunity to power fading caused by chromatic dispersion. By using carrier-suppressed single side-band (CS-SSB) modulation for the local oscillator (LO) signal and carrier-suppressed double side-band (CS-DSB) modulation for the input signal, no vector superposition for the same output microwave frequency occurs, making the system immune from power fading caused by chromatic dispersion. Phase tuning is achieved by shifting the phase of the LO signal, and direct electrical tuning of the wideband microwave input signal is avoided, thus supporting large working bandwidth. A phase-shifted down-conversion experiment is carried out, where a phase shift with 0 ~390° and down-conversion are achieved with a phase variation of less than 5° and power variation less than 3.5 dBm when the input signal sweeps between 12 ~16 GHz. The mixer is simple and power-efficient since it uses a single compact modulator, and does not require any optical filters. No power notches are observed in the output microwave spectrum, proving that the dispersion-related frequency-selective fading is mitigated.

Measurement of the rotational Doppler frequency shift of a spinning object using a radio frequency orbital angular momentum beam.

An indirect approach based on phase measurement is proposed to measure the rotational Doppler frequency shift, which takes full advantage of the phase structure of orbital angular momentum (OAM) beams in radio domain, using a vector network analyzer (VNA) as a phase discriminator. A proof-of-concept experiment is established by an optical-controlled system with the OAM state of 1. By analyzing the experiment's results, the rotational Doppler frequency shift is measured as 24.83 Hz (max error rate 0.67%) at 50π rad/s rotational velocity, deducing the rotational velocity as 50.18π (average error rate 0.36%).

Generating the orbital angular momentum of radio frequency signals using optical-true-time-delay unit based on optical spectrum processor.

A system for generating radio frequency signals with orbital angular momentum (OAM) is proposed and certificated for the first time, which employs an array of multiple optical-true-time-delay elements and circular antennas array (CAAs). A constructive Fourier series theory about CAAs collectively forming an OAM radio beam is demonstrated. An optical spectrum processor offers the four lines high-resolution time delay by adding a series of linear optical phase shifts. The OAM radio beam with topological charge L=1 is produced and measured successfully.

Cannabidiol represses miR-143 to promote cardiomyocyte proliferation and heart regeneration after myocardial infarction.

Mammalian heart is capable to regenerate almost completely early after birth through endogenous cardiomyocyte proliferation. However, this regenerative capacity diminishes gradually with growth and is nearly lost in adulthood. Cannabidiol (CBD) is a major component of cannabis and has various biological activities to regulate oxidative stress, fibrosis, inflammation, and cell death. The present study was conducted to investigate the pharmacological effects of CBD on heart regeneration in post-MI mice. MI models in adult mice were constructed via coronary artery ligation, which were administrated with or without CBD. Our results demonstrate that systemic administration (10 mg/kg) of CBD markedly increased cardiac regenerative ability, reduced infarct size, and restored cardiac function in MI mice. Consistently, in vitro study also showed that CBD was able to promote the proliferation of neonatal cardiomyocytes. Mechanistically, the expression of miR-143-3p related to cardiomyocyte proliferation was significantly down-regulated in CBD-treated cardiomyocytes, while the overexpression of miR-143-3p inhibited cardiomyocyte mitosis and eliminated CBD-induced cardiomyocyte proliferation. Moreover, CBD enhanced the expression of Yap and Ctnnd1, which were demonstrated as the target genes of miR-143-3p. Silencing of Yap and Ctnnd1 hindered the proliferative effects of CBD. We further revealed that inhibition of the cannabinoid receptor 2 impeded the regulatory effect of CBD on miR-143-3p and its downstream target Yap/Ctnnd1, which ultimately eliminated the pro-proliferative effect of CBD on neonatal and adult cardiomyocytes. Taken together, CBD promotes cardiomyocyte proliferation and heart regeneration after MI via miR-143-3p/Yap/Ctnnd1 signaling pathway, which provides a new strategy for cardiac repair in adult myocardium.