Suppressing backscattering noise of a resonant fiber optic gyroscope using coherent detection.

This paper provides a novel, to the best of our knowledge, method for suppressing backscattering noise of a resonant fiber optic gyroscope (RFOG) with a coherent detection technique. The light from the fiber ring resonator is mixed with a reference beam rather than being demodulated directly in traditional configurations, generating a coherent signal with a radio frequency. The central frequencies of the two reference lights used for the clockwise and counterclockwise waves are different to avoid the effect of backscattered waves. Besides, a common phase modulation is applied on the two counter-propagating waves to eliminate the parasitic effect due to the residual amplitude modulation in the phase modulator. Two demodulation schemes for the rotation rate detection from the coherent signals are then proposed and demonstrated, with performance on noise suppression tested. One is the beat-frequency demodulation, and the other is the self-mixing demodulation technique. The influence of backscattering intensity is reduced from 270°/h to 3°/h and 0.05°/h with the two demodulation techniques, respectively, showing a full suppression of backscattering noise.

Performance of a resonant fiber-optic gyroscope based on a broadband source.

A resonant fiber-optic gyroscope (RFOG) based on a broadband source can avoid the fundamental drawback of coherence detection processing while possessing the greater sensitivity afforded by the finesse of the fiber-optic ring resonator. In this paper, the basic operation principle is presented and demonstrated in detail, and various noise sources, as well as the temperature effect encountered in this broadband source-driven RFOG, are studied and analyzed. Then a combined modulation technique is proposed to suppress the residual backscattering noise. To further reduce the effect of temperature transience, an asymmetric fiber ring resonator is designed. In the experiment, a bias stability of 0.01°/h is successfully demonstrated with a 100 m-long fiber ring resonator of 8 cm diameter in a laboratory environment without temperature control.

Resonant fiber optical gyroscope using the single-mode fiber ring resonator.

This paper provides a scheme for realizing high-accuracy, low-cost resonant fiber optical gyroscopes (RFOGs) with single-mode (SM) fibers. The temperature-related polarization noise, which deteriorates the bias stability of the RFOG, has been suppressed thanks to a much longer birefringence beat length of SM fibers. It is also helpful to improve the theoretical sensitivity of the RFOG because of the very low loss of the SM fiber components. A transmissive 39-m-long SM fiber ring resonator (FRR) is fabricated. The measured finesse is 58.7, and its total loss is calculated to be less than 0.3 dB. Using this SM-FRR as the sensing element, an RFOG is then set up that achieves an angular random walk of 0.0039∘/√h and a bias stability of 0.05°/h. The experimental results show that the SM-FRR scheme would be a good candidate for producing high-accuracy and low-cost RFOGs.

Signal processing improvement of passive resonant fiber optic gyroscope using a reciprocal modulation-demodulation technique.

A resonant fiber optic gyroscope (RFOG) based on the reciprocal phase modulation-demodulation technique is proposed and demonstrated. The residual amplitude modulation induced error of the phase modulator, and the effect of laser frequency noise are all suppressed thanks to the reciprocity of the proposed signal processing scheme. Compared with the past separate modulation-demodulation RFOG, the angular random walk is improved by a factor of 15 times from 0.08°/√h to 0.0052°/√h, and the bias stability is improved from 0.3°/h to 0.06°/h.

Performance improvement of a resonant fiber optic gyroscope with a hybrid photonic crystal fiber ring resonator.

The photonic crystal fiber (PCF) with better thermal stability and polarization-maintaining performance is applied to the resonant fiber optic gyroscope (RFOG). A hybrid fiber ring resonator is fabricated using the conventional polarization-maintaining fiber (PMF) and PCF with close mode field diameters (MFDs) to reduce MFD-mismatch-induced splicing loss. Furthermore, the temperature-dependent birefringence coefficients of the PMF and the PCF are measured to differ almost four times in absolute value and be opposite in sign. The polarization stability of the hybrid PCF-PMF ring resonator is improved by a factor of 7 compared with the PMF ring resonator with the same length of PMF. The RFOG equipped with this hybrid PCF-PMF ring resonator achieves a bias stability of 1.67°/h.

Single-polarization fiber-pigtailed high-finesse silica waveguide ring resonator for a resonant micro-optic gyroscope.

A new record for high-finesse silica waveguide ring resonators (WRRs), to the best of our knowledge, is demonstrated experimentally. The achieved finesse and resonant depths of the silica WRR with a length of 7.9 cm and a diameter of 2.5 cm are 196.7% and 98%, respectively. In addition, the silica WRR chip is coupled with single-polarization fiber to improve the polarization extinction ratio (PER) and, thus, to reduce the polarization error. With the application of this high-finesse and high-PER WRR to the resonant micro-optic gyroscope (RMOG), a bias stability of 0.004°/s is observed over a 1 h timeframe. To the best of our knowledge, this is the first RMOG reported in the open literature that can sense the earth's rotation rate (15°/h).

Large left circumflex coronary artery with a fistula to superior vena cava: Diagnosis by echocardiography.

The left circumflex coronary artery associated with a fistula to superior vena cava is a rare entity. We describe a 7-year-old girl who presented with a cardiac murmur and was diagnosed with a coronary artery fistula between the left circumflex artery and superior vena cava by echocardiography. The surgical occlusion of the fistula was successful.

Measurement of the reflection and loss of the hybrid air-core photonic-bandgap fiber ring resonator.

A fiber ring resonator is the key element in a resonant fiber optic gyroscope (RFOG). Both reflection and loss characteristics can severely decrease the accuracy of the RFOG. This paper first implements optical frequency domain reflectometry (OFDR) to measure the reflection and loss coefficients of the hybrid air-core photonic-bandgap fiber (PBF) ring resonator. Compared with the traditional measurement method of the resonant curve, OFDR can clearly distinguish the two junctions between the air-core PBF and the solid-core fiber. The measured reflection coefficients at the two splicing points are 1.77% and 2.65%, respectively. The excess losses are 2.28 dB and 3.22 dB, respectively. Thus, the measurement of the junctions in the fiber ring resonator is realized.

Effect of Fresnel reflections in a hybrid air-core photonic-bandgap fiber ring-resonator gyro.

A novel hybrid polarization-maintaining (PM) air-core photonic bandgap fiber (PBF) ring resonator is firstly demonstrated by using a conventional solid-core PM fiber optical coupler formed by splicing a section of PM air-core PBF into the resonator. Due to Fresnel reflections exist at the two junctions between the air-core PBF and the solid-core fiber, the forward output signal of this hybrid ring resonator is the normal resonant curve with the superposition of the lightwaves that experienced even numbers of Fresnel reflections and the backward output signal is composed of lightwaves that experienced odd numbers of Fresnel reflections. Rigorous derivations of the forward and backward output signals are given out. The biggest resonant depth and finesse of the hybrid air-core PBF ring resonator predicted are 0.352 and 6.3 respectively by assuming a splice loss of 1.8 dB per junction. These predictions are finally confirmed by testing both the forward and backward output signals of the hybrid ring resonator. With the countermeasures against the influences of the odd numbers of Fresnel reflections, a bias stability of 0.007°/s is successfully demonstrated in a hybrid PM air-core PBF ring-resonator gyro.

The Alteration Profiles of m6A-Tagged circRNAs in the Peri-Infarct Cortex After Cerebral Ischemia in Mice.

The N6-methyladenosine (m6A) modification acts as a dynamic regulatory factor in diseases by regulating the metabolism and function of the transcriptome, especially mRNAs. However, little is known regarding the functional effects of m6A modifications on circRNAs. In this research, we established a distal middle cerebral artery occlusion (MCAO) model in adult C57BL/6J mice. The mice were divided into three groups: sham surgery, 3 days after MCAO (3d), and 7 days after MCAO (7d). Reverse transcription quantitative polymerase chain reaction (RT-qPCR) demonstrated that the mRNA expression levels of m6A-related methyltransferases (METTL3, METTL14), demethylases (FTO, ALKBH5), and reading proteins (YTHDF1, YTHDF3) altered compared to the sham group. Furthermore, the translation level of ALKBH5 and YTHDF3 was significantly decreased in the 3d group while increased in 7d group. Methylated RNA immunoprecipitation (MeRIP) and circRNA microarray indicated 85 hypermethylated and 1621 hypomethylated circRNAs in the 3d group. In the 7d group, the methylation level increased in 57 and decreased in 66 circRNAs. Subsequently, our results were verified by MeRIP-qPCR. Bioinformatics analysis was performed to analyze the functions of differentially m6A-modified circRNAs. We found some m6A modified-circRNAs associated with cerebral infarction, providing a new direction for the molecular mechanism of stroke.

Transplantation of a beating heart: A first in man.

Background: In the current practice, graft ischaemia and reperfusion injury (IRI) is considered an inevitable component in organ transplantation, contributes to compromised organ quality, inferior graft survival and limitations in organ availability. Among all the donor organs, the heart is most vulnerable to IRI and the tolerated ischaemic time is the shortest. Methods: By combining adapted surgical techniques and normothermic machine perfusion (NMP), we performed the first case of ischaemia-free beating heart transplantation (IFBHT) in man. The donor heart was procured after an in situ NMP circuit was established, then underwent ex situ NMP and implanted under NMP support. The post-transplant graft function was monitored. Findings: The donor heart was procured, preserved, and implanted under a continuously perfused, normothermic, oxygenated, beating state. During ex situ NMP, the donor heart beat with sinus rhythm and adequate ventricular contraction, consumed oxygen and lactate, suggesting a good cardiac function. The dynamic electrocardiogram demonstrated an absence of ischaemic injury of the donor heart during the entire procedure. The echocardiogram showed an immediate graft function with a left ventricle ejection fraction (LVEF) of 70%. The patient was discharged on post-transplantation day 20 and was followed up for 8 months with normal cardiac function and life. Interpretation: This study shows the feasibility of IFBHT procedure, which might be able to completely avoid graft IRI, has thus the potential to improve transplant outcome while increasing organ utilization. Funding: This study was funded by National Natural Science Foundation of China, Guangdong Provincial Key Laboratory Construction Projection on Organ Donation and Transplant Immunology, and Guangdong Provincial International Cooperation Base of Science and Technology.

Lnc-M2 controls M2 macrophage differentiation via the PKA/CREB pathway.

Long noncoding RNAs (lncRNAs) play an indispensable role in the process of M1 macrophage via regulating the development of macrophages and their responses to bacterial pathogens and viral infections. However, there are few studies on the lncRNA-mediated functions and regulatory mechanisms of M2 macrophage polarization. In this study, we found a number of differentially expressed lncRNAs between human monocyte derived M0 and M2 macrophages according to array analysis and quantitative polymerase chain reaction (qPCR) validation. The lncRNA RP11-389C8.2 (we named lnc-M2 in this study) was observed to be highly expressed in M2 macrophages. In Situ Localization and Quantification Analysis showed that lnc-M2 was expressed in the nucleus and cytosolic compartments of M2 macrophages. Notably, lnc-M2 knockdown enhanced the phagocytic ability of M2 macrophages. Ulteriorly, the results of RNA-Protein interaction experiments indicated that protein kinase A (PKA) was a lnc-M2 associated RNA-binding protein (RBP). Western blot showed that phosphorylated cAMP response element binding protein (p-CREB), a well-known key downstream transcription factor of PKA, was lowly phosphorylated in lnc-M2-silencing M2 macrophages. Furthermore, we found that transcriptional factor Signal Transducer And Activator Of Transcription 3 (STAT3) promoted lnc-M2 transcription along with the up-regulation of epigenetic histone modification markers at the lnc-M2 promoter locus, indicating that STAT3 activated lnc-M2 and eventually facilitated the process of M2 macrophage differentiation via the PKA/CREB pathway. Collectively, our date provide evidence that the transcription factor STAT3 can promote the transcription of lnc-M2 and facilitated the process of M2 macrophage differentiation via the PKA/CREB pathway. This study highlights a novel mechanism underlying the M2 macrophage differentiation.

Exosomal Delivery of AntagomiRs Targeting Viral and Cellular MicroRNAs Synergistically Inhibits Cancer Angiogenesis.

Nasopharyngeal carcinoma (NPC) is an Epstein-Barr virus (EBV)-associated cancer characterized by a high degree of recurrence, angiogenesis, and metastasis. The importance of alternative pro-angiogenesis pathways including viral factors has emerged after decades of directly targeting various signaling components. Using NPC as a model, we identified an essential oncogenic pathway underlying angiogenesis regulation that involves the inhibition of a tumor suppressor, Spry3, and its downstream targets by EBV-miR-BART10-5p (BART10-5p) and hsa-miR-18a (miR-18a). Overexpression of EBV-miR-BART10-5p and hsa-miR-18a strongly promotes angiogenesis in vitro and in vivo by regulating the expression of VEGF and HIF1-α in a Spry3-dependent manner. In vitro or in vivo treatment with iRGD-tagged exosomes containing antagomiR-BART10-5p and antagomiR-18a preferentially suppressed the angiogenesis and growth of NPC. Our findings first highlight the role of EBV-miR-BART10-5p and oncogenic hsa-miR-18a in NPC angiogenesis and also shed new insights into the clinical intervention and therapeutic strategies for nasopharyngeal carcinoma and other virus-associated tumors.