A Novel Silicon Forward-Biased PIN Mach-Zehnder Modulator with Two Operating States.

In this paper, we demonstrate a silicon forward-biased positive intrinsic negative (PIN) Mach-Zehnder modulator (MZM), which has two operating states of high efficiency and high speed. The two operating states are switched by changing the position where the electric signal is loaded. The modulator incorporates a PIN phase shifter integrated with the passive resistance and capacitance (RC) equalizer (PIN-RC), which expands the electro-optic (E-O) bandwidth by equalizing it with modulation efficiency. The fabricated modulator exhibits a low insertion loss of 1.29 dB in two operating states and a compact design with a phase shifter length of 500 µm. The modulation efficiencies are 0.0088 V·cm and 1.43 V·cm, and the corresponding 3 dB E-O bandwidths are 200 MHz and 7 GHz, respectively. The high-speed modulation performance of the modulator is confirmed by non-return-to-zero (NRZ) modulation with a data rate of 15 Gbps without any pre-emphasis or post-processing. The presented modulator shows functional flexibility, low insertion loss, and a compact footprint, and it can be suitable for applications like optical switch arrays and analog signal processing.

Comparison of Arthroscopic-Assisted Percutaneous Internal Fixation With a Modified Reducer Versus Open Reduction and Internal Fixation for Schatzker Type II and III Tibial Plateau Fractures.

Background: Tibial plateau fractures require anatomical reduction and stable fixation to achieve satisfactory results. In addition, addressing any related injuries is of paramount importance. Arthroscopic reduction and internal fixation (ARIF) has been promoted as a possible technique to treat tibial plateau fractures. Purpose: To compare the effectiveness of ARIF with this modified reducer and open reduction and internal fixation (ORIF) for Schatzker types II and III tibial plateau fractures. Study Design: Cohort study; Level of evidence, 3. Methods: We retrospectively reviewed 68 patients who were treated for Schatzker type II or III tibial plateau fractures between August 1, 2014, and October 31, 2018. Patients were categorized into the ARIF (n = 33) and ORIF groups (n = 35). The groups were compared regarding intra-articular injuries, duration of hospital stay, complications, and clinical outcomes-including the International Knee Documentation Committee (IKDC) score, the Hospital for Special Surgery (HSS) score, and range of motion (ROM). The paired t test was used to compare preoperative and postoperative data, and the chi-square test was used to compare the IKDC and HSS scores. Results: The median follow-up period was 36 months (26-40 months). Additional intra-articular lesions were found in 29 patients-21 in the ARIF group and 8 in the ORIF group (P = .02). A significant difference was observed in the duration of hospital stay-3.58 ± 1.46 days for the ARIF group and 4.57 ± 1.12 days for the ORIF group (t = -3.169; P = .002). All fractures healed within 3 months after surgery. The complication rate for all patients was 11%, with no significant difference between the ARIF and ORIF groups (t = 1.244; P = .265). At the final follow-up, there were no significant differences between the 2 groups in the IKDC score, HSS score, and ROM (P > .05 for all). Conclusion: ARIF with a modified reducer was found to be an effective, reliable, and safe procedure for the treatment of Schatzker types II and III tibial plateau fractures. Both ARIF and ORIF provided equally good results, while ARIF offered a more precise evaluation and reduced the duration of hospital stay.

Silicon nitride assisted tri-layer edge coupler on lithium niobate-on-insulator platform.

Lithium niobate-on-insulator (LNOI) is a promising integration platform for various applications, such as optical communication, microwave photonics, and nonlinear optics. To make Lithium niobate (LN) photonic integrated circuits (PICs) more practical, low-loss fiber-chip coupling is essential. In this Letter, we propose and experimentally demonstrate a silicon nitride (SiN) assisted tri-layer edge coupler on LNOI platform. The edge coupler consists of a bilayer LN taper and an interlayer coupling structure composed of an 80 nm-thick SiN waveguide and an LN strip waveguide. The measured fiber-chip coupling loss for the TE mode is 0.75 dB/facet at 1550 nm. Transition loss between the SiN waveguide and LN strip waveguide is ∼0.15 dB. In addition, the fabrication tolerance of the SiN waveguide in the tri-layer edge coupler is high.

[Development and clinical application of a new reduction device for the treatment of tibial plateau fracture under arthroscopic monitoring].

OBJECTIVE: To develop a reduction device for the arthroscopy-assisted treatment of tibial plateau fracture and explore its clinical efficacy. METHODS: From May 2018 to September 2019, 21 patients with tibial plateau fracture were treated, including 17 males and 4 females. Their ages ranged from 18 to 55 years old with an average of (38.6±8.7) years old. There were 5 cases of Schatzker typeⅡand 16 cases of Schatzker type Ⅲ. The self-designed reductor combined with arthroscope was used for auxiliary reduction and fixation(minimally invasive percutaneous plate osteosynthesis). The efficacy was analyzed by observing the operation time, blood loss, fracture healing time and knee function(HSS and IKDC scoring criteria). RESULTS: All the 21 patients were followed up for 8 to 24 with an average of(14.0±3.1) months. The operative time ranged from 70 to 95 min with an average of(81.7±7.6)min, incision length ranged from 4 to 7 cm with an average of(5.3±0.9) cm, intraoperative blood loss ranged from 20 to 50 ml with an average of(35.3±5.2) ml, postoperative weight-bearing time ranged from 30 to 50 d with an average of(35.1±9.2) d, fracture healing time ranged from 65 to 90 d with an average of(75.0±4.4) d, and complications were 0 cases, respectively. The fracture was well healed and no screw plate fracture was observed. The knee function scores of HSS and IKDC 18 months after operation were significantly higher than those before operation(P<0.05). CONCLUSION: The custom-made reduction tool for the arthroscopic management of tibial plateau fracture is reasonable in design and simple in operation. The specific reduction tool could effectively reduce the fracture, and shorten the fixation time with minimally invasive procedure.

Photonic sampled and quantized analog-to- digital converters on thin-film lithium niobate platform.

In this paper, an on-chip photonic sampled and quantized analog-to-digital converter (ADC) on thin-film lithium niobate platform is experimentally demonstrated. Using two phase modulators as a sampler and a 5×5 multimode interference (MMI) coupler as a quantizer, a 1 GHz sinusoidal analog input signal was successfully converted to a digitized output with a 20 GSample/s sampling rate. To evaluate the system performance, the quantization curves together with the transfer function of the ADC were measured. The experimental effective number of bits (ENOB) was 3.17. The demonstrated device is capable of operating at a high frequency over 67 GHz, making it a promising solution for on-chip ultra-high speed analog-to-digital conversion.

Analysis of Differential Gene Expression of the Aquatic Insect Protohermes costalis (Walker) (Megaloptera: Corydalidae) in Response to Cadmium Exposure.

Heavy metal pollution in freshwater ecosystems is a serious threat to aquatic organisms. Species of Megaloptera are important predators of aquatic invertebrates and have been widely used as bioindicators in assessing the quality of freshwater ecosystems. In this study, we determined the differential gene expression profile of Protohermes costalis (Walker) (Megaloptera: Corydalidae) in response to cadmium (Cd) exposure by using transcriptome analysis. A total of 60,627 unigenes were obtained in the transcriptomes of 150 mg/liter (PL), 1,000 mg/liter (PH) CdCl2 treatment, and the no Cd control (PC). Differential expression gene (DEG) analysis by pairwise comparison identified 2,794 DEGs after filtering the noninsect genes and repetitive counts. 606 DEGs were shared in comparisons of PL versus PC and PH versus PC, with 165 DEGs consistently up-regulated and 441 down-regulated by both PL and PH. Six heat shock proteins (HSPs) in the HSP70 family were identified in P. costalis and PcosHSP68 was up-regulated by both PL and PH. Real-time quantitative polymerase chain reaction (RT-qPCR) confirmed that the expression levels of PcosHSP68 in PL and PH were higher than that of PC by 31 and 197%, respectively. These results showed that exposure to Cd altered the gene expression profiles of P. costalis and the transcriptome data presented in this study provide insight into future studying on molecular mechanisms of Cd toxicity to these insects.

C-band four-channel CWDM (de-)multiplexers on a thin film lithium niobate-silicon rich nitride hybrid platform.

A four-channel coarse wavelength division multiplexing (CWDM) (de)multiplexer on a thin film lithium niobate-silicon rich nitride hybrid platform has been designed, fabricated, and experimentally measured. Enabled by cascaded multimode waveguide Bragg gratings, the (de)multiplexer has a box-like spectral response, wide 1-dB bandwidth (10 nm), low excess loss (<1.08dB), and low channel cross talk (<-18dB). The central wavelengths of the (de-)multiplexer are 1531/1551/1571/1591 nm, which align to the wavelength grids stipulated by the standard ITU-T G.694.2.

On-chip four-mode (de-)multiplexer on thin film lithium niobate-silicon rich nitride hybrid platform.

A four-mode (de-)multiplexer with transverse electric field light (TE0-TE3) is experimentally demonstrated on a thin film lithium niobate-silicon rich nitride hybrid platform. Enabled by cascaded asymmetrical directional couplers, a (de-)multiplexer with low insertion loss (0.38 dB to 1.6 dB) and low cross talk (-18.46dB to -20.43dB) is obtained at 1550 nm. All channels have cross talk <-16dB from 1480 nm to 1580 nm. The transmission of 4×50 Gbps on-off keying signals is experimentally achieved on the proposed (de-)multiplexer. Experimental results show that the proposed (de-)multiplexer is a promising approach to enhance the transmission capacity in thin film lithium niobate based photonics integrated circuits.

40 GHz high-efficiency Michelson interferometer modulator on a silicon-rich nitride and thin-film lithium niobate hybrid platform.

We propose and demonstrate a Michelson interferometer modulator with integrated Bragg reflectors on a silicon-rich nitride-thin-film lithium niobate hybrid platform. High-reflectivity Bragg reflectors are placed at the ends of both arms, which double the electro-optic (E-O) interaction length and reduce the velocity mismatch between the microwave and optical wave. The presented Michelson interferometer modulator achieves a measured half-wave voltage length product as low as 1.06 V cm and high-speed modulation up to 70 Gbps. A 3-dB E-O bandwidth beyond 40 GHz is also achieved, which is, to the best of our knowledge, the highest modulation bandwidth of Michelson interferometer modulators.

Efficient grating couplers on a thin film lithium niobate-silicon rich nitride hybrid platform.

A grating coupler on a thin film x-cut lithium niobate-silicon rich nitride hybrid platform is proposed and demonstrated. An inverse taper is applied to suppress higher-order mode excitation. A coupling efficiency of -5.82dB and 3 dB bandwidth of 57 nm are obtained near the wavelength of 1550 nm between the standard single-mode fiber (SMF-28) and sub-micrometer waveguides.

Ultra-compact low-loss variable-ratio 1×2 power splitter with ultra-low phase deviation based on asymmetric ladder-shaped multimode interference coupler.

We propose a novel optical 1×2 power splitter based on an asymmetric ladder-shaped multimode interference (MMI) coupler in silicon-on-insulator (SOI) which has an ultra-compact size of 3.3 µm×2.4 µm. A trapezoid with a small region is removed from the bottom left corner of the MMI coupler to achieve variable splitting ratio. The comparison with the asymmetric rectangular 1×2 splitter is numerically analyzed. By carefully optimizing the width of input taper, the proposed splitter shows a low phase deviation for the two output ports while keeping both of a low-loss performance and feasible splitting ratio. The simulated results show that the splitter can operate with an insertion loss less than 0.67 dB, a large range of splitting ratio from 50:50 to 11:89 and an ultra-low phase deviation less than 2.8° among the C band spectra.

Passive silicon ring-assisted Mach-Zehnder interleavers operating in the broadband spectral range.

We propose and experimentally demonstrate a passive and compact interleaver on a silicon on insulator (SOI) platform using a ring-assisted asymmetrical Mach-Zehnder interferometer configuration. The wavelength-insensitive couplers, i.e., multimode interference couplers and adiabatic 3-dB couplers, are introduced to eliminate the effect of an unequal splitting ratio and wavelength on crosstalk and the operating spectral range. In addition, there exists an inherent phase shift between the two couplers; the device can be fully passive and works well without additional thermal tuning. In the calculation, the influence of wavelength sensitivity of self-coupling coefficients and couplers on the performance of the interleaver is considered. The experiment shows that, by employing wavelength-insensitive couplers, the operating spectral range of the proposed interleavers was extended to be >140nm for all sorts of channel spacing and channel count. The measured free spectral range is 4.6 nm, and the crosstalk is as low as -46.6dB for the best case.

TE/TM-pass polarizers based on lateral leakage in a thin film lithium niobate-silicon nitride hybrid platform.

TE/TM-pass polarizers based on the lithium niobate-silicon nitride hybrid platform are numerically proposed for the first time, to the best of our knowledge. By utilizing the lateral leakage of a shallowly etched rib waveguide, 1-mm-long TE/TM-pass polarizers with high extinction ratios of 28.72/24.03 dB are obtained. Because of the anisotropy of the lithium niobate, the lateral leakage of TE/TM polarization modes can occur along crystallographic z/y directions, respectively. Such TE/TM-pass polarizers can be integrated in the same wafer.

TE/TM-pass polarizers based on lateral leakage in a thin film lithium niobate-silicon nitride hybrid platform: publisher's note.

This publisher's note contains a correction to Opt. Lett.45, 4915 (2020)OPLEDP0146-959210.1364/OL.404197.

Comparative Study on the Elucidation of Sedimentary Phosphorus Species Using Two Methods, the SMT and SEDEX Methods.

Sedimentary phosphorus (P) forms are important representatives of P sources and their bioavailability as well as the potential of sediments to release P in water. In this study, surface sediments along a transect of the Changjiang Estuary and two transects along the Andong salt marsh in the southwest of Hangzhou Bay were subjected to the elucidation of sedimentary P species using the standards, measurements, and testing (SMT) and sequential extraction (SEDEX) methods. The results showed that the mean sedimentary P forms elucidated by the SMT method were as follows: organic P (OP; ∼11-14 mg/kg; ∼30-45% of total P; TP) > apatite P (∼5-15 mg/kg; ∼21-36% TP) > Fe/Al-P (∼8-14 mg/kg; ∼31-34% TP), with inorganic P (IP) composing 54-70% of TP. The mean sedimentary P forms elucidated by the SEDEX method were as follows: authigenic P (∼54-68 mg/kg; ∼41-46% TP) > extractable P (Ex-P; ∼36-53 mg/kg; ∼28-34%) > Fe-P (∼21-27 mg/kg; ∼13-19%) > OP (∼8.7-13 mg/kg; ∼5-8%) > detrital P (De-P; ∼2 mg/kg; ∼1-2% TP), with IP composed of ∼91-94% TP. These results showed that the SEDEX method elucidated higher concentrations of sedimentary P forms as well as the TP from these coastal sediments although the SMT method had the advantage of being more economic and faster. The results of both the SMT and SEDEX methods showed that the Andong salt marsh and Changjiang Estuary sediments had much bioavailable P. The mean percentages of bioavailable P from the SMT and SEDEX methods were ∼64-74% and 52-56% of TP, respectively, indicating that these sediments were prone to release P to the coastal areas.

[Repair effect of bFGF combined with bone marrow mesenchymal stem cells on spinal cord injury in rats].

OBJECTIVE: To observe the repair effect of bone marrow mesenchymal stem cells (BMSCs) combined with basic fibroblast growth factor (bFGF) on spinal cord injury in rats and explore its mechanism. METHODS: SD rat BMSCs were obtained by serum culture technique. Eighty healthy 6-week-old male SD rats(weight about 240 g) were randomly divided into 4 groups with 20 each. The sham operation group underwent simple laminectomy without damaging spinal cord and was kept in the same condition as the other 3 groups. The other 3 groups underwent left T9 spinal cord hemisection to establish spinal cord injury model. After 9 days of modeling the local transplantation was performed. The Control group was implanted with gelatin sponge containing normal saline. The BMSCs transplantation group was implanted with gelatin sponge containing BMSCs. The bFGF+BMSCs transplantation group was implanted with gelatin sponge containing bFGF+BMSCs. After 4 and 8 weeks, the expression of NF-200 and GFAP in injured spinal cord tissue was analyzed by Western blotting and the recovery of hind limb function was evaluated by Basso Beattie Bresnahan(BBB) motor function score scale. RESULTS: The BBB scores of BMSCs transplantation group and bFGF+BMSCs transplantation group were better than control group at 4 and 8 weeks after operation (P<0.05) and there was significant difference between bFGF+BMSCs transplantation group and BMSCs transplantation group (P<0.05). After 4 and 8 weeks postoperatively, NF-200 expression was minimal in control group and only a small amount was expressed in BMSCs transplantation group while in bFGF+BMSCs transplantation group NF-200 was highly expressed(P<0.05). GFAP expression was high in control group, middle in BMSCs transplantation group and low in bFGF BMSCs transplantation group(P<0.05). There was significant difference between bFGF+BMSCs transplantation group, BMSCs transplantation group and control group(P<0.05). CONCLUSIONS: The combined transplantation of BMSCs and bFGF can repair the spinal cord injury in rats. The mechanism may be related to the decrease of GFAP expression and the increase of NF-200 expression.

[Relationship of occupational stress and negative life events with low birth weight].

OBJECTIVE: To explore the influence of occupational stress and negative life events on low birth weight (LBW). METHODS: 1:1 matched case-control study was employed, in which 438 singleton LBW infants with birth weight less than 2500 g (their pregnancy term being 28 to 42 weeks) served as case group while 438 with singleton term normal birth weight served as control group matched by sex, delivery time and hospital. All of their mothers were inquired by well trained investigators about their socio-demographic characteristics, occupational stress, and negative life events occurring in different pregnancy term. After controlling for mother's age, occupation, education level and family income, conditional logistic regression was employed to asses the influence of occupational stress and negative life events on LBW. RESULTS: Compared with those with low technical skill utilization and low job decision, mothers with high technical skill utilization (OR=0.62; 95% CI=0.43 approximately 0.91) and high job decision (OR=0.67; 95% CI=0.46 approximately 0.97) significantly decreased the risk of laboring LBW. Compared with those not exposed to negative life events, mothers with negative life event score being=3 in the middle three months of pregnancy (OR=18.85; 95% CI=1.58 approximately 225.02), with negative life event score being 1 in the later three months of pregnancy (OR=2.67; 95% CI=1.14 approximately 6.28), with negative life event score being 2 (OR=2.80; 95% CI=1.04 approximately 7.52) and=3 in the whole time of pregnancy (OR=2.94; 95% CI=1.22 approximately 7.09) were the risk factors of LBW. CONCLUSION: Negative life events might affect LBW and negative life events occurring in the different term of pregnancy impact LBW differently.