Time-varying propagation model and dynamic-feedback-phase correction for multiplexed orbital angular momentum beams in atmospheric turbulence.

Freespace optical (FSO) communication in an outdoor setting is complicated by atmospheric turbulence (AT). A time-varying (TV) multiplexed orbital angular momentum (OAM) propagation model to consider AT under transverse-wind conditions is formulated for the first time, and optimized dynamic correction periods for various TV AT situations are found to improve the transmission efficiency. The TV nature of AT has until now been neglected from modeling of OAM propagation models, but it is shown to be important. First, according to the Taylor frozen-turbulence hypothesis, a series of AT phase screens influenced by transverse wind are introduced into the conventional angular-spectrum propagation analysis method to model both the temporal and spatial propagation characteristics of multiplexed OAM beams. Our model shows that while in weak TV AT, the power standard deviation of lower-order modes is usually smaller than that of higher-order modes, the phenomena in strong TV AT are qualitatively different. Moreover, after analyzing the effective time of each OAM phase correction, optimized dynamic correction periods for a dynamic feedback communication link are obtained. An optimized result shows that, under the moderate TV AT, both a system BER within the forward-error-correction limit and a low iterative computation volume with 6% of the real-time correction could be achieved with a correction period of 0.18 s. The research emphasizes the significance of establishing a TV propagation model for exploring the effect of TV AT on multiplexed OAM beams and proposing an optimized phase-correction mechanism to mitigate performance degradation caused by TV AT, ultimately enhancing overall transmission efficiency.

Elevated circulating BMP9 aggravates pulmonary angiogenesis in hepatopulmonary syndrome rats through ALK1-Endoglin-Smad1/5/9 signalling.

BACKGROUND: Bone morphogenetic protein 9 (BMP9) is a hepatokine that plays a pivotal role in the progression of liver diseases. Moreover, an increasing number of studies have shown that BMP9 is associated with hepatopulmonary syndrome (HPS), but its role in HPS is unclear. Here, we evaluated the influence of CBDL on BMP9 expression and investigated potential mechanisms of BMP9 signalling in HPS. METHODS: We profiled the circulating BMP9 levels in common bile duct ligation-induced HPS rat model, and then investigated the effects and mechanisms of HPS rat serum on pulmonary vascular endothelial dysfunction in rat model, as well as in primarily cultured rat pulmonary microvascular endothelial cells. RESULTS: Our data revealed that circulating BMP9 levels were significantly increased in the HPS rats compared to control group. Besides, the elevated BMP9 in HPS rat serum was not only crucial for promoting endothelial cell proliferation and tube formation through the activin receptor-like kinase1 (ALK1)-Endoglin-Smad1/5/9 pathway, but also important for accumulation of monocytes. Treatments with ALK1-Fc or silencing ALK1 expression to inhibit the BMP9 signalling pathway effectively eliminated these effects. In agreement with these observations, increased circulating BMP9 was associated with an increase in lung vessel density and accumulation of pro-angiogenic monocytes in the microvasculature in HPS rats. CONCLUSIONS: This study provided evidence that elevated circulating BMP9, secreted from the liver, promote pulmonary angiogenesis in HPS rats via ALK1-Endoglin-Smad1/5/9 pathway. In addition, BMP9-regulated pathways are also involved in accumulation of pro-angiogenic monocytes in the pulmonary microvasculature in HPS rats.

Indoor visible light communication denoising system combining iterative variational mode decomposition and multiple frequency shift keying modulation.

To reduce noise in indoor visible light communication (IVLC), the Pearson correlation coefficient difference (PCCD), a denoising system combining iterative variational mode decomposition (IVMD) and multiple frequency shift keying modulation (MFSK), is proposed. Compared with VMD, the method can directly determine the optimal number of VMD modes and solve the issue of VMD penalty factor selection to some extent. The simulation results show that, when the input SNRs vary from -15 to -8d B, the proposed method can improve the output SNRs of the 2FSK signal by an average of 15.5 dB and reduce the BER by 55.8%, improve the output SNR of the 4FSK signal by an average of 13 dB, and reduce the BER by 54.4%. The proposed method can also effectively suppress noise interference in real IVLC experiments at a distance of 1 m. In addition, the IVMD-MFSK denoising system can be applied to denoise all frequency-modulated signals with high applicability.

Alterable interferential fineness for high temperature sensing calibration based on Bragg hollow core fiber.

We propose, what we believe to be, a novel method for high temperature sensing calibration based on the mechanism of alterable interferential fineness in Bragg hollow core fiber (BHCF). To verify the proof-of-concept, the fabricated sensing structure is sandwiched by two sections with different length of BHCF. Two interferential fineness fringes dominate the transmission spectrum, where the high-fineness fringes formed by anti-resonant reflecting optical waveguide (ARROW) plays the role for high temperature measurement. Meanwhile, the low-fineness fringes induced by short Fabry-Perot (F-P) cavity are exploited as temperature calibration. The experimental results show that the ARROW mechanism-based temperature sensitivity can reach 26.03 pm/°C, and the intrinsic temperature sensitivity of BHCF is 1.02 pm/°C. Here, the relatively lower magnitude of the temperature sensitivity is considered as the standard value since it merely relies on the material properties of silicon. Additionally, a large dynamic temperature range from 100 °C to 800 °C presents linear response of the proposed sensing structure, which may shine the light on the sensing applications in the harsh environment.

Compact and high Q-factor multimode racetrack ring resonator based on transformation optics.

The ring resonator is a versatile and functional component in the silicon-based integrated optical circuit. Most of the previously reported ring resonators work in the single-mode case. With the rapid development of mode division multiplexing technology, a multimode ring resonator (MMRR) has been proposed and the usage beyond the limit of a conventional single mode ring resonator has been explored. However, the reported MMRRs are either large in size or low in quality factor. In this paper, we designed a compact silicon MMRR with a small bending radius of 15µm, in which the three lowest TE modes all have high Q-factors. For suppressing the mode loss and inter-mode crosstalk in MMRR, a multimode waveguide bend (MWB) with mode adiabatic evolution was designed based on transformation optics and waveguide shape optimization. The independent excitation of each order mode of the MMRR is realized by using bending directional coupler and asymmetric directional coupler. We successfully fabricated the device on a silicon-on-insulator (SOI) platform using simple one-step lithography. The measured loaded Q-factors of the three lowest TE modes are 5.9 × 104, 4.5 × 104, and 4.7 × 104, respectively.

Annular phase grating-assisted recording of an ultrahigh-order optical orbital angular momentum.

Ultrahigh-order optical orbital angular momentum (OAM) states of the identification over ±270 orders are implemented by annular phase grating (APG) and Gaussian beams with different wavelengths. Particularly, the far-field diffraction intensity patterns feature the spiral stripes instead of Hermitian-Gaussian (HG)-like fringes. It's worth noting that the spiral stripes present uniform distribution, thus the order of OAM states can be intuitively acquired. More specifically, the OAM states can be confirmed from the total amount and rotating direction of the spiral stripes. Compared with traditional methods, the propose scheme contributes to the perfect-distributed and sharper spiral stripes. Moreover, it also makes an easier observation of the patterns in the CCD camera with limited imaging targets. In our experimental setup, the optical filter is removed and the APG parameters are not strictly required. Therefore, the propose optical transmission system is equipped with the advantages of efficiency, robustness and low cost, which paves a promising way for the communication capacity enhancement.

FISH-Based Karyotype Analyses of Four Dracaena Species.

The genus Dracaena is the main source of dragon's blood, which is a plant resin and has been used as traditional medicine since ancient times in different civilizations. However, the chromosome numbers and karyotypes present in this genus remain poorly understood. In this study, fluorescence in situ hybridization (FISH) using oligonucleotide probes for ribosomal DNAs (5S and 45S rDNA) and telomeric repeats (TTTAGGG)3 was applied to analyze 4 related species: Dracaena terniflora Roxb., Dracaena cambodiana Pierre ex Gagnep., Aizong (Dracaena sp.), and Dracaena cochinchinensis (Lour.) S.C. Chen. In all 4 species, both 5S and 45S rDNA showed hybridization signals in the paracentromeric region of a pair of chromosomes; the sizes of the 45S rDNA signals were larger than those of the 5S rDNA. Importantly, the telomeric repeat signals were located in the telomeric regions of almost all chromosomes. The results indicated that the chromosome number of all 4 Dracaena species is 2n = 40, and the lengths of the mitotic metaphase chromosomes range from 0.99 to 2.98 µm. Our results provide useful cytogenetic information, which will be beneficial to future studies in genome structure of the genus Dracaena.

Complete two-dimensional photonic bandgap in refractive-index ratio 2.1 photonic crystals due to high-order bands.

We find that in a suitably designed photonic crystal (PC) certain high-order photonic bands are less affected by the refractive-index ratio (RIR) than low-order bands, enabling the realization of a robust and complete two-dimensional (2D) photonic bandgap in a moderate refractive-index-ratio PC. A detailed theoretical investigation of low- and high-order bandgaps in a series of PCs with different configurations is performed that shows that high-order bands may favor substantial complete photonic bandgaps (CPBGs) for systems with a moderate RIR. Furthermore, the importance of the geometry and structural parameters on achieving a high-order CPBG is found. Specifically, a hexagonal lattice PC of annular-hole-peripheral connecting rods is proposed, which can support a CPBG with a refractive-index ratio (RIR) as low as nhigh:nlow=2.1; to the best of our knowledge, this is the lowest RIR used to obtain a 2D CPBG in a PC.

Deterministic design of focusing apodized subwavelength grating coupler based on weak form and transformation optics.

The focusing apodized subwavelength grating coupler (F-ASGC) has advantages of high coupling efficiency, small footprint and simple fabrication process, which make it a popular component for chip-scale coupling and testing of integrated optical circuit. However, the design of F-ASGC based on effective medium theory lacks accuracy, causing the drawbacks of peak wavelength deviation and performance degradation. In this work, we propose a deterministic design method of F-ASGC. Our grating coupler is formed by assembling various subwavelength grating units according to their complex effective indexes. The complex effective indexes of these grating units are accurately obtained by the weak form calculation. Then combining with transformation optics, we strictly analyze the F-ASGC for the first time. The simulation results show that the deterministically designed F-ASGC has high coupling efficiency of -2.51 dB, 3 dB bandwidth of 51 nm, and accurate central wavelength of 1553.1 nm. And we also fabricated it on the commercial SOI wafer. The measured maximum efficiency is -3.10 dB, the 3 dB bandwidth is 55 nm, and the central wavelength is 1551.5 nm.

Combined ultrasound and nerve stimulator-guided deep nerve block may decrease the rate of local anesthetics systemic toxicity: a randomized clinical trial.

BACKGROUND: Ultrasound guidance might decrease the incidence of local anesthetics systemic toxicity (LAST) for many peripheral nerve blocks compared with nerve stimulator guidance. However, it remains uncertain whether ultrasound guidance is superior to nerve stimulator guidance for deep nerve block of the lower extremity. This study was designed to investigate whether deep nerve block with ultrasound guidance would decrease the incidence of LAST compared with that with nerve stimulator guidance, and to identify associated risk factors of LAST. METHODS: Three hundred patients undergoing elective lower limb surgery and desiring lumbar plexus blocks (LPBs) and sciatic nerve blocks (SNBs) were enrolled in this study. The patients were randomly assigned to receive LPBs and SNBs with ultrasound guidance (group U), nerve stimulator guidance (group N) or dual guidance (group M). The primary outcome was the incidence of LAST. The secondary outcomes were the number of needle redirection, motor and sensory block onset and nerve distribution restoration time, as well as associated risk factors. RESULTS: There were 18 patients with LAST, including 12 in group U, 4 in group N and 2 in group M. By multiple comparisons among the three groups, we found that the incidence of LAST in group U (12%) was significantly higher than that in group N (4%)(P = 0.037) and group M(2%)(P = 0.006). The OR of LAST with hepatitis B (HBV) infection and the female sex was 3.352 (95% CI,1.233-9.108, P = 0.013) and 9.488 (95% CI,2.142-42.093, P = 0.0004), respectively. CONCLUSIONS: Ultrasound guidance, HBV infection and the female sex were risk factors of LAST with LPBs and SNBs. For patients infected with HBV or female patients receiving LPBs and SNBs, we recommended that combined ultrasound and nerve stimulator guidance should be used to improve the safety. TRIAL REGISTRATION: This study was approved by the Ethical Committee of the First Affiliated Hospital of Army Medical University. The protocol was registered prospectively with the Chinese Clinical Trial Registry ( ChiCTR-IOR-16008099 ) on March 15, 2016.

Ultrathin graphene diaphragm-based extrinsic Fabry-Perot interferometer for ultra-wideband fiber optic acoustic sensing.

An ultra-wideband fiber optic acoustic sensor based on graphene diaphragm with a thickness of 10nm has been proposed and experimentally demonstrated. The two reflectors of the extrinsic Fabry-Perot interferometer is consist of fiber endface and graphene diaphragm, and the cavity is like a horn-shape. The radius of the effective area of the ultrathin graphene diaphragm is 1mm. Attributed to the strong van der Waals force between the diaphragm and the ceramic ferrule, the sensor head can be applied not only in the air but also underwater. Experimental results illustrate that ultra-wideband frequency response is from 5Hz to 0.8MHz, covering the range from infrasound to ultrasound. The noise-limited minimum detectable pressure level of 0.77Pa/Hz1/2@5Hz and 33.97µPa/Hz1/2@10kHz can be achieved, and the applied sound pressure is 114dB and 65.8dB, respectively. The fiber optic acoustic sensor may have a great potential in seismic wave monitoring, photoacoustic spectroscopy and photoacoustic imaging application due to its compact structure, simple manufacturing, and low cost.

Simultaneous implementation of enhanced resolution and large dynamic range for fiber temperature sensing based on different optical transmission mechanisms.

In this paper, a high resolution and large dynamic range fiber optic temperature sensor without measurement crosstalk has been proposed. Two combinational mechanisms of anti-resonant reflecting optical waveguide and inline Mach-Zehnder interference structure are integrated in single hole twin eccentric cores fiber. The dual-effect composite spectrum is consist of several dominant resonant wavelengths and comb pattern, which are corresponding to the two above-mentioned mechanisms. Gauss fit and fast Fourier transform filtering are used for extracting the resonant wavelengths and comb spectrum, respectively. Accordingly, the temperature sensitivity of 42.18pm/°C and 2.057nm/°C are achieved by tracking the coherent decrease point. The lower sensitivity can guarantee a large dynamic range, while the higher one will contribute to the enhanced resolution. Therefore, the temperature monitoring is the combination of large dynamic range and enhanced resolution. Moreover, the size of the ultracompact sensor is only 950µm, which has a great potential for engineering applications.

Comparison of lumbar plexus block using the short axis in-plane method at the plane of the transverse process and at the articular process: a randomized controlled trial.

BACKGROUND: Although the safety and effectiveness of the short-axis in-plane method has been confirmed for lumbar plexus block, the operation is difficult and has a high rate of epidural spread at the plane of the articular process. Therefore, we developed a new in-plane technique, called the beach chair method, which displays images from the transverse process. We compared the operative difficulty and incidence of epidural spread of the beach chair method with those of the control method (at the plane of the articular process) in this randomized controlled clinical trial. METHODS: Sixty patients, aged 18 to 75 years, scheduled for unilateral arthroscopic knee surgery were randomized to receive double-guided lumbar plexus block by the beach chair method (n = 30) or the control method (n = 30) with 30 ml 0.5% ropivacaine hydrochloride; all patients received a sciatic nerve block with 10 ml 1% lidocaine hydrochloride and 10 ml 0.5% ropivacaine hydrochloride. RESULTS: The incidence of epidural spread after lumbar plexus block was significantly lower in the beach chair group than that in the control group [1 case (3.3%) vs. 9 (30.0%), P = 0.006]. Moreover, the imaging time (34.2 ± 16.7 s vs. 48.9 ± 16.8 s, P = 0.001), needling time (85.0 ± 45.3 s vs. 131.4 ± 88.2 s, P = 0.013) and number of needle punctures (2.7 ± 1.3 vs. 4.5 ± 2.1, P = 0.000) were significantly lower in the beach chair group than those in the control group; the ultrasound visibility score of the beach chair group was better than that of the control group. There were no significant differences in the remaining indicators. CONCLUSIONS: The beach chair method was easier and was associated with a lower incidence of epidural spread than the control method. Therefore, the beach chair method (at the plane of the transverse process) provides another promising option for lumbar plexus block for the non-obese population. TRIAL REGISTRATION: Chinese Clinical Trial Registry (ChiCTR), Registration number:ChiCTR-INR-15007505, registered on November 06, 2015.

Biomimetic spiral grating for stable and highly efficient absorption in crystalline silicon thin-film solar cells.

By emulating the phyllotaxis structure of natural plants, which has an efficient and stable light capture capability, a two-dimensional spiral grating is introduced on the surface of crystalline silicon solar cells to obtain both efficient and stable light absorption. Using the rigorous coupled wave analysis method, the absorption performance on structural parameter variations of spiral gratings is investigated firstly. Owing to diffraction resonance and excellent superficies antireflection, the integrated absorption of the optimal spiral grating cell is raised by about 77 percent compared with the conventional slab cell. Moreover, though a 15 percent deviation of structural parameters from the optimal spiral grating is applied, only a 5 percent decrease of the absorption is observed. This reveals that the performance of the proposed grating would tolerate large structural variations. Furthermore, the angular and polarization dependence on the absorption of the optimized cell is studied. For average polarizations, a small decrease of only 11 percent from the maximum absorption is observed within an incident angle ranging from -70 to 70 degrees. The results show promising application potentials of the biomimetic spiral grating in the solar cell.

Biomimetic spiral grating for stable and highly efficient absorption in crystalline silicon thin-film solar cells: erratum.

In the original manuscript, the maximum short-circuit current in Fig. 2 and the description of angular stability for polarization in Fig. 6 are found incorrect owing to negligence. The incorrect maximum integrated absorption also led to errors appeared in Fig. 3 and Fig. 4(d), in which the mistake value was used to plot. In this erratum, all of those mistakes have been corrected. Moreover, both higher Fourier expansion order and the resolution of frequency are adopted in the recalculation to make sure the updated results to be reliable. The updated data presented still support the main conclusions drawn in the previous manuscript.

Turbulence heterodyne coherent mitigation of orbital angular momentum multiplexing in a free space optical link by auxiliary light.

A novel scheme is proposed to mitigate the atmospheric turbulence effect in free space optical (FSO) communication employing orbital angular momentum (OAM) multiplexing. In this scheme, the Gaussian beam is used as an auxiliary light with a common-path to obtain the distortion information caused by atmospheric turbulence. After turbulence, the heterodyne coherent detection technology is demonstrated to realize the turbulence mitigation. With the same turbulence distortion, the OAM beams and the Gaussian beam are respectively utilized as the signal light and the local oscillation light. Then the turbulence distortion is counteracted to a large extent. Meanwhile, a phase matching method is proposed to select the specific OAM mode. The discrimination between the neighboring OAM modes is obviously improved by detecting the output photocurrent. Moreover, two methods of beam size adjustment have been analyzed to achieve better performance for turbulence mitigation. Numerical results show that the system bit error rate (BER) can reach 10-5 under strong turbulence in simulation situation.

Single hole twin eccentric core fiber sensor based on anti-resonant effect combined with inline Mach-Zehnder interferometer.

A novel fiber curvature sensor without temperature cross interference based on a single hole twin eccentric core fiber has been proposed. Anti-resonant mechanism combined with inline Mach-Zehnder interference (MZI) structure are applied to the measurands detection. The spectrum is composed of a comb spectrum caused by the inline MZI and several dominant resonant wavelengths induced by anti-resonant effect. The curvature sensitivity of -1.54dB/m-1 can be achieved by intensity demodulation of the selected dip of Gaussian fitting. Similarly, the temperature sensitivity of 70.71pm/°C and 34.17pm/°C are respectively achieved by tracking coherent decrease point obtained by the FFT band pass filter method and Gaussian fit dip. Consequently, a relatively higher resolution of temperature measurement can be realized by the two methods mentioned above. The proposed sensor has a great potential for structural health monitoring, such as buildings, towers, bridges, and many other infrastructures due to its compact structure, easy fabrication and without cross impacts.

[Application of FTIR and Active Ingredients Quantitative Analysis on Quality Control of Dai Medicine Alstonia scholaris (L.) R. Br.].

FTIR fingerprint of the leaves and immature stems of Alstonia scholaris (L.) R. Br. was established as a content determination method for the detection of picrinine, ursolic acid and oleanolic acid. Different medicinal parts were identified based on principal component analysis, while exploring the influence of immature stems for the leaves and the application of FTIR and HPLC in the Dai quality control in order to speed up the pace of Dai medicine modernization. Infrared spectroscopy of different batches samples were collected and the data was preprocessed as to automatic baseline correction, smooth, ordinate normalization, second order derivative, and then to PCA, all the datum in triplicate. For content determination of picrinine, mobile phase was acetonitrile (40) water (contain 0.1% ammonia water) (60) and the wavelength was set at 287 nm. For ursolic acid and oleanolic acid, the mobile phase was mixture (12∶88) of 0.1% formic acid in water (A) and methanol (B). Wavelength was 210 nm. As the results, the original spectrum difference was not obvious for leaves and stems. Pretreatment spectroscopy had a significant variation on absorption peak number and intensity in 3 000～2 800 and 1 800～500 cm(-1). The results of PCA showed that, the leaves and stems were separated; in addition the difference of different batches leaves was bigger than the stems. The mean contents of picrinine, ursolic acid and oleanolic acid in leaves were 0.79，8.47，7.51 and 0.21，1.78，1.67 mg·g(-1) in stems, respectively. The content of ursolic acid and oleanolic acid is higher than picrinine, but ursolic acid and oleanolic acid content had no obvious difference. Mean content of three ingredients in leaves is much higher than in stems. Picrinine content in leaves was 3.8 times of immature stems, ursolic acid and oleanolic acid content were 5.1 and 4.2 times of immature stems, respectively. The variety of picrinine content in different batches samples was biggest, ursolic acid and oleanolic acid content was relatively stable. The overall quality of leaves has an obvious difference compared with the immature stems, so the leaves of A. scholaris mix with immature stems could not be as Dai medicine in Dai clinic. Infrared spectroscopy combined with chromatography can quickly identify different medicinal parts and evaluate overall quality of Dai medicine, which can apply to quality control of Dai medicine.

[Study on effect elements of anthers opening-closing movement and its cell morphology regulatory mechanism of Paris polyphylla var. yunnanensis].

In order to study the effect elements of anthers opening-closing movement of Paris polyphylla var. yunnanensis, and its cell morphology regulatory mechanism. Anthers daily opening in the morning and closing in the evening and its corresponding ecological elements changes were recorded. Different light, temperature, humidity experiment and artificial rainfall experiment were designed to observe the effect on anthers opening-closing movement, paraffin sections were made to observe the cell morphology change when the anthers daily opening and closing. The result showed that the movement of anthers daily opening and closing was regulated by ecological elements. The overall trend was high temperature and strong light, low humidity was favorable for anther opening, and low temperature, weak light, high humidity was favorable for anther closing. In this experiment, the effect of these ecological elements on the movement of anthers opening from strong to weak was humidity, temperature, light. The effect of these ecological elements on the movement of anthers closing from strong to weak was light, humidity, temperature. The direct contact of the raindrops causes the rapid closing of the anthers in the rain. Observing the cell morphology change when anthers opening and closing, it was a pollen sac dehydration and water-absorption process, different light, temperature and humidity conditions induce different physiological activities in the cell, which caused the cell osmotic pressure change, eventually resulting in anther opening and closing movement. But anthers closing caused by the rain was a simple physical adjustment process, the raindrops fell on the anthers directly, which caused anthers soaked water and change of the cell osmotic pressure, then resulting in anther closing.

Compact high extinction ratio asymmetric polarization beam splitter of periodic rods waveguide.

A compact high extinction ratio polarization beam splitter based on an asymmetric directional coupler was proposed and theoretically investigated. The asymmetric directional coupler consists of a silicon wire waveguide and a 1D periodic silicon rods waveguide, which results in an ultracompact polarization splitting length. By using the plane wave expansion method, a minimum coupling length of 3.43 µm was obtained, and the length was then confirmed by finite-difference time-domain simulation. Moreover, for 1550 nm wavelength, high extinction ratios of about 28 and 18 dB were also observed for TE and TM polarizations, respectively. The ultrahigh extinction ratio for TE polarization is mainly arising from the appearance of TM bandgap in the periodic rods waveguide. In addition, for both polarizations, the extinction ratios are all above 10 dB covering a 180 nm bandwidth, and it was also demonstrated that the device has a high transmission for TM polarization.