Adjoint Algorithm Design of Selective Mode Reflecting Metastructure for BAL Applications

Broad-area lasers (BALs) have found applications in a variety of crucial fields on account of their high output power and high energy transfer efficiency. However, they suffer from poor spatial beam quality due to multi-mode behavior along the waveguide transverse direction. In this paper, we propose a novel metasurface waveguide structure acting as a transverse mode selective back-reflector for BALs. In order to effectively inverse design such a structure, a digital adjoint algorithm is introduced to adapt the considerably large design area and the high degree of freedom. As a proof of the concept, a device structure with a design area of 40 × 20 μm2 is investigated. The simulation results exhibit high fundamental mode reflection (above 90%), while higher-order transverse mode reflections are suppressed below 0.2%. This is, to our knowledge, the largest device structure designed based on the inverse method. We exploited such a device and the method and further investigated the device's robustness and feasibility of the inverse method. The results are elaborately discussed.

Advances in Semiconductor Lasers Based on Parity-Time Symmetry

Semiconductor lasers, characterized by their high efficiency, small size, low weight, rich wavelength options, and direct electrical drive, have found widespread application in many fields, including military defense, medical aesthetics, industrial processing, and aerospace. The mode characteristics of lasers directly affect their output performance, including output power, beam quality, and spectral linewidth. Therefore, semiconductor lasers with high output power and beam quality are at the forefront of international research in semiconductor laser science. The novel parity-time (PT) symmetry mode-control method provides the ability to selectively modulate longitudinal modes to improve the spectral characteristics of lasers. Recently, it has gathered much attention for transverse modulation, enabling the output of fundamental transverse modes and improving the beam quality of lasers. This study begins with the basic principles of PT symmetry and provides a detailed introduction to the technical solutions and recent developments in single-mode semiconductor lasers based on PT symmetry. We categorize the different modulation methods, analyze their structures, and highlight their performance characteristics. Finally, this paper summarizes the research progress in PT-symmetric lasers and provides prospects for future development.

Deep Neural Network-Based Phase-Modulated Continuous-Wave LiDAR

LiDAR has high accuracy and resolution and is widely used in various fields. In particular, phase-modulated continuous-wave (PhMCW) LiDAR has merits such as low power, high precision, and no need for laser frequency modulation. However, with decreasing signal-to-noise ratio (SNR), the noise on the signal waveform becomes so severe that the current methods to extract the time-of-flight are no longer feasible. In this paper, a novel method that uses deep neural networks to measure the pulse width is proposed. The effects of distance resolution and SNR on the performance are explored. Recognition accuracy reaches 81.4% at a 0.1 m distance resolution and the SNR is as low as 2. We simulate a scene that contains a vehicle, a tree, a house, and a background located up to 6 m away. The reconstructed point cloud has good fidelity, the object contours are clear, and the features are restored. More precisely, the three distances are 4.73 cm, 6.00 cm, and 7.19 cm, respectively, showing that the performance of the proposed method is excellent. To the best of our knowledge, this is the first work that employs a neural network to directly process LiDAR signals and to extract their time-of-flight.

Polarization-separated feedback spectral beam combining source

A novel, to the best of our knowledge, structure for spectral beam combining (SBC) is proposed, utilizing a polarization-separated feedback (PSF). A polarization separation element is introduced to separate the laser beam into a TE-polarized light and a TM-polarized light. The lower-power light is selected as the external feedback to adjust the resonant wavelength, while the other light is combined spectrally. Compared to the conventional SBC source with a similar feedback, the power and efficiency of the PSFSBC are improved by approximately 20%. Additionally, the beam quality in the non-SBC direction is optimized by 10%, and the power on the output coupler is reduced to nearly one-third. This provides an effective method for achieving an optimized SBC performance.

A Design of High-Efficiency: Vertical Accumulation Modulators Based on Silicon Photonics

On-chip optical modulators, which are capable of converting electrical signals into optical signals, constitute the foundational components of photonic devices. Photonics modulators exhibiting high modulation efficiency and low insertion loss are highly sought after in numerous critical applications, such as optical phase steering, optical coherent imaging, and optical computing. This paper introduces a novel accumulation-type vertical modulator structure based on a silicon photonics platform. By incorporating a high-K dielectric layer of ZrO2, we have observed an increase in modulation efficiency while maintaining relatively low levels of modulation loss. Through meticulous study and optimization, the simulation results of the final device structure demonstrate a modulation efficiency of 0.16 V·cm, with a mere efficiency-loss product of 8.24 dB·V.

Ultra-broadband depolarization based on directly-coupled quantum wire-to-well modulation and their aliasing effect for polarization-insensitive light-emitting diodes

Nowadays, strained quantum structures have been widely used in various light-emitting devices with a variety of compounds for progressive applications. However, the lattice-mismatch-induced strains in the materials would cause a problem of polarization dependence for polarization-independent optical applications. To address this issue, in this paper we propose a novel ultra-broadband depolarization mechanism and approach based on a directly-coupled well-wire-hybrid nanostructure. It contains quantum wire-to-well modulation and their aliasing effects on strain, energy-band structure and optical gain to obtain independent and comparable bipolarization of optical signals. The material structure involves a special well and on-well quantum wires with gradually-changing band-gaps, which are formed by utilizing the indium (In)-segregation effect and the growth-orientation-dependent multi-atomic step effect. With this special hybrid nanostructure, the depolarization efficiency can be 95% higher than that of a single compressive-strained quantum well. A low polarization degree of 0.05 and a very small gain difference of |GTE - GTM| < 1.3 cm-1 in different polarizations are achieved over a very broad gain bandwidth (870-950 nm) for an InGaAs material system. Therefore, this is a new chance for the development of ultra-broadband and polarization-insensitive optical applications.

Geochemical mercury pools regulate diverse communities of hgcA microbes and MeHg levels in paddy soils

Rice paddies are unique artificial wetlands generating methylmercury (MeHg), a highly potent neurotoxin. However, the impact of diverse mercury (Hg) pools on the Hg-methylating communities during rice growth is unclear. This study investigates soil treated with five mercury forms (HgCl2, α-HgS, β-HgS, nano-HgS, and Hg-DOM) at two levels (5 mg/kg and 50 mg/kg). The results showed a varying abundance of sulphate-reducing bacteria, Geobacteraceae, methanogens, and hgcA microbes in the soils across rice grown under different mercury treatments and concentrations. Soils treated with HgCl2, nano-HgS and β-HgS had higher than average levels of hgcA-methanogen abundance, and the abundance significantly and positively correlated with MeHg concentration in all samples (p < 0.05). The shifting trends in Hg-methylating microbial structure following treatment with α-HgS, β-HgS, nano-HgS and Hg-DOM at both 5 and 50 mg/kg Hg levels were diverse compared with the control group. HgCl2 treatment showed contrasting trends in community distribution of Hg methylators at 5 and 50 mg/kg Hg levels during rice growth. Dissolved organic carbon, redox potential and sulphate levels significantly correlated with variation in the Hg-methylating microbial community structure and MeHg production in soils.

Variation analysis of photonic lantern mode control ability under mode oscillation: a new approach

In this Letter, we present a novel, to the best of our knowledge, image-based approach to analyze the mode control ability of a photonic lantern employed in diode laser beam combining, aiming to achieve a stable beam output. The proposed method is founded on theories of power flow and mode coupling and is validated through experiments. The findings demonstrate that the analysis of the beam combining process is highly reliable when the main mode component of the output light is the fundamental mode. Moreover, it is experimentally demonstrated that the mode control performance of the photonic lantern significantly influences the beam combining loss and the fundamental mode purity. In the essence of the variation-based analysis, a key advantage of the proposed method is its applicability even in the situation of a poor combined beam stability. The experiment only requires the collection of the far-field light images of the photonic lantern to characterize the model control ability, achieving an accuracy greater than 98%.

[Clinicopathological analysis of primary gastric (gastrointestinal)-type mucoglandular lesion of endometrium]

Objective: To investigate the clinical and pathological features of primary gastric (gastrointestinal)-type mucoglandular lesions of the endometrium. Methods: Eight cases of primary gastric (gastrointestinal)-type mucoglandular lesions of endometrium diagnosed between 2014 to 2022 were retrieved from pathology archives of the Obstetrics and Gynecology Hospital Affiliated to Fudan University, Shanghai, China. The clinical history, pathological sections and follow-ups were analyzed. Results: The eight patients ranged in age from 35 to 67 years, with an average age of 55.5 years. Seven patients were examined for high-risk human papillary virus (HPV) before operation. Only one of them was positive for high-risk HPV52. No cervical mucinous lesions were found in any of the patients. Two cases were invasive gastric (gastrointestinal)-type adenocarcinoma, 2 cases were benign gastric (gastrointestinal)-type mucinous metaplasia, and the other 4 cases were atypical gastric (gastrointestinal)-type mucinous gland hyperplasia. Microscopically, tumor cells showed mucous epithelium with gastrointestinal differentiation. Immunophenotyping showed that MUC6 was diffusely or focally positive in 5 cases, CK20 and CDX2 were positive in 3 cases. And p16 was negative or focally positive in 5 cases and strongly positive in 1 case. ER was expressed in both benign and atypical lesions, and weakly positive or negative in the invasive adenocarcinoma. p53 showed mutant expression in one case and wild-type expression in the rest. HPV in situ hybridization was negative. Conclusions: Primary gastric (gastrointestinal)-type mucoglandular lesions of the endometrium show various forms of gastrointestinal differentiation, which are high-risk HPV independent. Morphology combined with immunohistochemistry is helpful for the diagnosis, which can only be made on exclusion of cervical gastrointestinal glandular lesion, gastrointestinal metastatic carcinoma and the mucinous subtype of endometrioid carcinoma.

Research Progress of Horizontal Cavity Surface-Emitting Laser

The horizontal cavity surface emitting laser (HCSEL) boasts excellent properties, including high power, high beam quality, and ease of packaging and integration. It fundamentally resolves the problem of the large divergence angle in traditional edge-emitting semiconductor lasers, making it a feasible scheme for realizing high-power, small-divergence-angle, and high-beam-quality semiconductor lasers. Here, we introduce the technical scheme and review the development status of HCSELs. Firstly, we thoroughly analyze the structure, working principles, and performance characteristics of HCSELs according to different structures, such as the structural characteristics and key technologies. Additionally, we describe their optical properties. Finally, we analyze and discuss potential development prospects and challenges for HCSELs.

[Study of incubation period of infection with 2019-nCoV Omicron variant BA.5.1.3]

Objective: To study the incubation period of the infection with 2019-nCoV Omicron variant BA.5.1.3. Methods: Based on the epidemiological survey data of 315 COVID-19 cases and the characteristics of interval censored data structure, log-normal distribution and Gamma distribution were used to estimate the incubation. Bayes estimation was performed for the parameters of each distribution function using discrete time Markov chain Monte Carlo algorithm. Results: The mean age of the 315 COVID-19 cases was (42.01±16.54) years, and men accounted for 30.16%. A total of 156 cases with mean age of (41.65±16.32) years reported the times when symptoms occurred. The log-normal distribution and Gamma distribution indicated that the M (Q₁, Q₃) of the incubation period from exposure to symptom onset was 2.53 (1.86, 3.44) days and 2.64 (1.91, 3.52) days, respectively, and the M (Q₁, Q₃) of the incubation period from exposure to the first positive nucleic acid detection was 2.45 (1.76, 3.40) days and 2.57 (1.81, 3.52) days, respectively. Conclusions: The incubation period by Bayes estimation based on log-normal distribution and Gamma distribution, respectively, was similar to each other, and the best distribution of incubation period was Gamma distribution, the difference between the incubation period from exposure to the first positive nucleic acid detection and the incubation period from exposure to symptom onset was small. The median of incubation period of infection caused by Omicron variant BA.5.1.3 was shorter than those of previous Omicron variants.

Spatial Distribution, Pollution, and Ecological Risk Assessment of Metal(loid)s in Multiple Spheres of the Shennongjia Alpine Critical Zone, Central China

The development of Earth's critical zone concept has strengthened the capacity of environmental science to better solve real-world problems, such as metal(loid) pollution in the remote alpine areas. The selected metal(loid) contents in soil, moss, and water were investigated to explore the geochemical distribution patterns, pollution levels, and potential ecological risks of metal(loid)s in the Shennongjia (SNJ) alpine critical zone of central China. The distribution of metal(loid)s in different spheres had horizontal and vertical differences. The maximum V, Ni, and Zn contents in water occurred at the sampling sites close to the Hohhot-Beihai Highway, while Dajiuhu Lake had the maximum Cu, Cr, and Mn contents. Most metal(loid) contents in the mosses showed an increasing trend from the northeast low-altitude area to the southwest high-altitude area, while As, Co, V, Ni, Cr, and Zn in soil decreased significantly with altitude and were enriched near the service areas and the highway. The contents of water Co and Ni, soil Cu and Mn, and moss As were evenly distributed and showed no significant differences with altitude. The enrichment factors, pollution index, Nemerow integrated pollution index, geo-accumulation index, heavy metal pollution index, contamination factor, and potential ecological risk index (PERI) were used to assess the pollution levels and ecological risks of SNJ soil, water, and atmosphere. The overall pollution levels of SNJ soil, moss, and water were low to moderate, low, and low, respectively. Soil V, Cu, Zn, moss As, Co, V, and Dajiuhu Lake water Mn were the main pollution factors. The ecological risks in the three spheres of the SNJ alpine critical zone were low to moderate, and As, Co, and V were the most critical potential ecological risk factors. The metal(loid)s pollution problem caused by the continuous development of tourism needs further attention.

Application of Pb Isotopes and REY Patterns in Tracing Heavy Metals in Farmland Soils from the Upper-Middle Area of Yangtze River

Farmland heavy metal pollution-caused by both human activity and natural processes-is a major global issue. In the current study, principal component analysis (PCA), cluster analysis (CA), rare earth elements and yttrium (REY) analysis, and isotope fingerprinting were combined to identify sources of heavy metal pollution in soil from different farmland types in the upper-middle area of the Yangtze River. The concentrations of Zn and Cu were found to be higher in the vegetable base and tea plantation soil compared with their concentrations in the orangery soil. On the other hand, greater accumulation of Cd and Pb was observed in the orangery soil versus the vegetable base and tea plantation soils. Influenced by the type of bedrock, REY was significantly enriched in the orangery soil and depleted in the vegetable base soil, as compared with the tea plantation soil. The Pb isotopic compositions of the tea plantation (1.173-1.193 for 206Pb/207Pb and 2.070-2.110 for 208Pb/206Pb) and vegetable base (1.181-1.217 for 206Pb/207Pb and 2.052-2.116 for 208Pb/206Pb) soils were comparable to those of coal combustion soil. The compositions of 206Pb/207Pb (1.149-1.170) and 208Pb/206Pb (2.121-2.143) in the orangery soil fell between those observed in soils obtained from coal combustion and ore smelting sites. Using the IsoSource model, the atmospheric Pb contributions of the vegetable base, tea plantation, and orangery soils were calculated to be 66.6%, 90.1%, and 82.0%, respectively, and the bedrock contributions of Pb were calculated to be 33.3%, 9.90%, and 18.1%, respectively. Based on the PCA, CA, and REY results, as well as the Pb isotope model, it appears that heavy metals in the orangery soil may be derived from atmospheric deposition and bedrock weathering, while heavy metals in the vegetable base and tea plantation soils may be derived from mining and the use of fertilizer.

Effects of hydrological connectivity project on heavy metals in Wuhan urban lakes on the time scale

Metal pollution in lakes threatens the ecological environment and human health. When environmental conditions change, heavy metals (HMs) in lake sediments can cause secondary pollution. At present, the implementation of the Hydrological Connectivity Project (HCP) is a significant means of lake governance. In this study, the accumulation, potential ecological risk, and sources of HMs in Four lakes (Houguan Lake, Tangxun Lake, Moshui Lake, and Chen Lake) in Wuhan city were compared before and after the completion of the HCP. The results indicated that the HCP reduced the enrichment factor of HMs and the potential ecological risk in the heavily polluted Moshui Lake but caused secondary pollution in the less polluted Houguan Lake. Moreover, the degree of purification of lakes that took a longer time to complete the HCP (Moshui Lake) was significantly higher than that of lakes with a shorter HCP completion time (Tangxun Lake). Water exchange caused by the HCP leading to exchange of the primary pollution source between Houguan Lake and Moshui Lake to a certain extent. This study provides a reference for evaluating the implementation effect of the HCP on HM pollution in lakes and for future governance planning.

Optimal Design and Analysis of 4.7 μm Hybrid Deep Dielectric High Efficiency Transmission Gratings

There is currently no transmission grating with good diffraction efficiency in the 4.7 μm band. Metal gratings at this wavelength are all reflective gratings which has a diffraction efficiency of lower than 90% and lower laser damage threshold. In this paper, we bring up a design of a multi-layer transmission grating with both high diffraction efficiency and wide working wavelength band. We have proved that the transmission grating made of composite materials has an average diffraction effectiveness of more than 96% throughout the whole spectral range of 200 nm. Meanwhile, the theoretically computed transmission grating has a highest first-order diffraction efficiency of more than 99.77% at 4746 nm. This multilayer dielectric film transmission grating's optimized design may further boost spectral beam combining power, providing a practical technique for increasing SBC power and brightness.

Spatial origin of the extracellular ATP-induced cytosolic calcium signature in Arabidopsis thaliana roots: wave formation and variation with phosphate nutrition

Extracellular ATP (eATP) increases cytosolic free calcium ([Ca²⁺ ]_cyt ) as a specific second messenger 'signature' through the plasma membrane DORN1/P2K1 receptor. Previous studies revealed a biphasic signature in Arabidopsis thaliana roots that is altered by inorganic phosphate (Pi) deprivation. The relationship between the two phases of the signature and possible wave formation have been tested as a function of Pi nutrition. The bioluminescent aequorin and intensiometric GCaMP3 reporters were used to resolve the spatial origin of the eATP [Ca²⁺ ]_cyt signature in Arabidopsis root tips. Application of eATP only to the root apex allowed [Ca²⁺ ]_cyt wave resolution without the confounding effects of eATP delivery by superfusion. The first apical millimetre of the root generates the first [Ca²⁺ ]_cyt increase by eATP, regardless of nutritional status. The second increase occurs sub-apically in the root hair zone, has some autonomy and is significantly reduced in Pi-starved roots. A significant component of the Pi-replete signature does not require DORN1/P2K1, but Pi-starved roots appear to have an absolute requirement for that receptor. Application of eATP specifically to the root apex provides evidence for cell-to-cell propagation of a [Ca²⁺ ]_cyt wave that diminishes sub-apically. The apex maintains a robust [Ca²⁺ ]_cyt increase (even under Pi starvation) that is the basis of a propagative wave, with implications for the ability of the root's eATP signalling systems to signal systemically. Partial autonomy of the sub-apical region may be relevant to the perception of eATP from microbes. eATP-induced [Ca²⁺ ]_cyt increase may not have always have an obligate requirement for DORN1/P2K1.

Inputs and sources of Pb and other metals in urban area in the post leaded gasoline era

The contamination status of heavy metals in urban environment changes frequently with the industrial structure adjustment, energy conservation and emission reduction and thus requires timely investigation. Based on enrichment factor, multivariate statistical analysis and isotope fingerprinting, we assessed comprehensively the inputs and sources of heavy metals in different samples from an urban area that was less impacted by leaded gasoline exhaust. The road dust contained relatively high levels of Cr, Pb and Zn (with enrichment factor >2) that originated from both exhaust and non-exhaust traffic emissions, while the moss plants could accumulate high levels of Pb and Zn from the deposition of traffic exhaust emission. This suggest that the traffic emission is still an important source of metals in the urban area although gasoline is currently lead free. On the contrary, the occurrences of metals in the urban soils were controlled by natural sources and non-traffic anthropogenic emission. These findings revealed that different samples would receive different inputs of metals from different sources in the urban area, and the responsiveness and sensitiveness of these urban samples to metal inputs can be ranked as moss ≥ dust > soil. Taken together, our results suggested that in order to avoid generalizing and get detail source information, multi-samples and multi-measures must be adopted in the assessment of integrated urban environmental quality.

[Study of development of public health safety literacy scale in China]

Objective: To develop a suitable scale for assessing the public health safety literacy in residents in China. Methods: The initial scale of Chinese public health safety literacy was developed through theoretical conceptualization, item pooling, field verifying and item inclusion and exclusion. Then the initial scale was converted into an electronic questionnaire. A total of 2 809 residents from 4 provinces were randomly selected for field testing. Classical test theory (CTT) and item response theory (IRT) were used for item reduction. SPSS 23.0 was used for exploratory factor analysis (EFA) and unidimensional testing. Package R 4.1.1 ltm and mirt were used for the analysis of the psychometric properties of items and generate the ICC, IIC and TIF. Results: The initial scale had 30 items (B1-B30), and the test took 9.8 s to complete one item averagely. According to the CTT, B2 was deleted due to coefficient of total correlation (CITC) <0.3 and the item-dimension correlation coefficient (IDCC) <0.4. B23 was deleted due to CITC<0.3, IDCC<0.4 and difficulty index (W) <0.2. B30 was deleted due to CITC<0.3 and W<0.2. The total Cronbach's α of the scale was 0.923 after deletion. EFA indicated that 14 items should be deleted due to lower factor loadings <0.7. EFA was conducted for remaining 13 items and 2 common factors were extracted, the factor loadings of all items were >0.7, the accumulated variance contribution of the 2 common factors was 63.361%, and the total Cronbach's α was 0.891, showing unidimensionality, IRT was used to test the remaining items. B14 and B20 were deleted due to discrimination coefficient (a) <0.3, difficulty threshold coefficient (b) ∉[-3,3], the small amount of information and the flat, crowded, non-monotonic ICC, and IIC. Finally, the Cronbach's α of the 11-itemed scale was 0.936 with TLI=0.97, CFI=0.99, and RMSEA=0.03. Conclusion: The final scale has good reliability, validity, discrimination, difficulty level and feasibility, and can be applied for the rapid assessment of public health safety literacy in China.

2m-distance external cavity VECSEL for wireless charging applications

We characterize laser generation in an ultralong air cavity (several meters in length) using an optical-pumped semiconductor gain chip for laser wireless charging applications. The study realizes laser generation in an external air cavity with a length of 200 cm, for the first time, and achieves a maximum output laser power of more than 86.3 mW. Furthermore, the laser oscillation can be maintained even when the output mirror of laser is off-axis within 1.6 cm. Thus, a long external cavity laser would ease the alignment between the laser beam and charging terminal, making it suitable for laser wireless charging applications.

Pine needles as urban atmospheric pollution indicators: Heavy metal concentrations and Pb isotopic source identification

Pine needles are reliable passive bio-samplers that can be used to monitor atmospheric pollution levels. This study applied Pb isotope and multivariate statistical analyses to pine needles to examine the characteristics, sources, and ecological risks of atmospheric heavy metal pollution in the cities of the middle reaches of the Yangtze River, China. The heavy metal concentrations were higher than those measured in pine needles elsewhere in the world. They were higher in the metropolitan city (Wuhan) than in the medium-sized city (Yichang) and lowest in the natural setting (Shennongjia Forestry District), which is consistent with trends in urbanization and industrialization. Principal component analysis grouped the metals into three main sets associated with industrial activities and traffic sources. The Pb composition determined the main anthropogenic Pb sources were vehicle exhaust and industrial activities related to the lead-zinc ore, only a few of which were coal combustion. Three risk assessment indexes (pollution load index, ecological risk index, and bioconcentration factor) suggest that atmospheric heavy metals in the study area pose moderate environmental and health risks.

Wavelength tuning robustness optimization for a high-temperature single-mode VCSEL used in chip-scale atomic sensing systems

In this paper, the wavelength current tuning characteristics of high-temperature-operation single-mode vertical-cavity surface-emitting lasers (VCSELs) for chip-scale atomic sensing systems are studied. Excellent wavelength current tuning robustness is helpful to improve the stability of atomic sensing systems. By optimizing the size of the oxide aperture combined with surface relief mode control technology, the single-mode VCSEL with an 8 µm oxide aperture can achieve 2.02 mW output power at 355 K, and the wavelength current tuning coefficient is ∼0.25nm/mA. This excellent wavelength current tuning robustness results from the low active current density and device heat generation due to the optimized oxide aperture size.

Large-aperture single-mode 795 nm VCSEL for chip-scale nuclear magnetic resonance gyroscope with an output power of 4.1 mW at 80 °C

Transverse optical confinement in oxide-confined vertical-cavity surface-emitting lasers (VCSELs) crucially depends on thickness of oxide layer and its position relative to a standing wave. Modifying the structure reduces the overlap between the oxide layer and the standing wave as well as effective refractive index difference between core and cladding of the VCSEL that subsequently decreases of the number of transverse modes and increases the mode extension beyond oxide aperture. A 795 nm VCSEL is designed and fabricated with this concept. The proposed device achieves high single-mode operation of 4.1 mW at 80 °C, SMSR of 41.68 dB, and OPSR of 27.4 dB. VCSEL is applied in a nuclear magnetic resonance gyroscope (NMRG) system as pump source due to its excellent device performance and satisfactory test results are obtained.

[Study on the development of public health and safety literacy assessment scale for university freshmen]

Objective: To develop a measurement scale for the public health and safety literacy of university freshmen. Methods: Item pooling was conducted through literature review and in-depth interview with public health experts, and a nominal group was organized to develop the initial items to form the questionnaire. A total of 250 freshmen were randomly selected to complete the questionnaire, and the assessment of psychometric properties were performed to carry out item reduction by using classical test theory and item response theory. Exploratory factor analysis method (EFA) was employed to calculate the item-factor loadings. The data collected from another 318 freshmen were analyzed using confirmatory factor analysis method (CFA). Results: The scale contained 3 dimensions and 9 items with all content validity index ≥0.8. The difficulty coefficient of 9 items was 1.18-2.43. The discriminative validity analysis showed that the difficulty index was 0.41-0.78, and the discrimination index was 0.38-0.64. Each of the remaining items had a statistically significant difference in the score value between the top 27% and lowest 27% of respondents (t>3, P<0.05). The item's Cronbach's α was 0.72-0.77, corrected item-total correlation was 0.33-0.60 and the overall α of the scale was 0.77. EFA indicated all item-factor loading were higher than 0.680, and the accumulated variance contribution of the 3 factors was 62.484%. Results of CFA showed that the overall fitness index of the model reached the fitness standard except for the χ² value. There was no statistical significance in the total score of the scale and the scores of each item among groups with different demographic characteristics (P>0.05). Conclusions: The newly developed public health safety literacy scale had a good reliability,validity,stability and item constancy.It can be used in measurement of the public health and safety literacy of university freshmen.

[Transitions on frailty status and related risk factors for its status worsening: finding from the Beijing MJ Health Screening Center]

Objective: To evaluate the transitions of frailty status and related factors influencing its worsening in middle-aged and elderly adults. Methods: Data was obtained from the Beijing MJ Health Screening Center. A total of 13 689 participants who attended health checkups at least twice during 2008-2019 and had more than three years' intervals during these two health checkups were included in the study. The frailty index comprising 28 variables was used to measure frailty status. Frailty was defined as frailty index ≥0.25, and prefrailty was defined as frailty index >0.10 and <0.25. Logistic regression analysis was performed to investigate the association of socio-demographic factors and lifestyle characteristics with the worsening of frailty status, stratified by frailty status at the first health checkup. Results: The mean age at the first and last health checkups were (42.3±9.2) and (47.9±9.3) years, respectively. The mean interval during these two health checkups was (5.7±1.9) years. At the first health checkup, the prevalence of frailty and prefrailty were 2.5% and 50.3%, respectively. While at the last health checkup, the prevalence of frailty and prefrailty rose to 3.9% and 55.4%. Of all participants, 67.3% remained in the same frailty state, 21.2% worsening, and 12.5% improving. In robust participants at the first health checkup, older age, female, low education level, smoking cessation, daily smoking, being general obesity measured by BMI or central obesity measured by WHR showed an increased the risk of worsening frailty status. However, in prefrail participants at the first health checkup, older age, female, general, or central obesity presented as risk factors for worsening frailty status. Conclusion: Modifiable factors such as low education level, smoking, and obesity may increase the risk of worsening frailty status.

Simulation and experimental research of a high-order Bragg grating semiconductor laser

In this paper, the influence of the epitaxial structure on distributed Bragg reflector (DBR) grating characteristics is studied by simulation analysis. Comparative analysis shows that the symmetrical epitaxial structure can achieve a lower threshold current and, thus, a higher power. Based on the simulated structure, a DBR laser based on a symmetric epitaxial structure was fabricated, and a single longitudinal mode laser output at ∼1060nm was obtained. The maximum power was 104.5 mW, and the side mode suppression ratio (SMSR) is 43 dB.

[Characteristics of human papillomavirus infection and abnormal cervical cytology in health check-up females in Shenzhen]

Objective: To describe the characteristics of human papillomavirus infection and thinprep cytologic test (TCT) outcome in health check-up females in Shenzhen. Methods: Use cross-sectional design, collect information from data from health check-up females in Shenzhen and describe characteristics of HPV infections screening and TCT outcomes. Results: We collected the data of 75 754 females, 103 508 females and 69 964 females received HPV detection, TCT and combined detection respectively. HPV standardized infection rate was 19.89% (95%CI: 19.45%-20.33%) and showed a "U-shaped" pattern in age distribution. The most prevalent HPV genotypes were 52, 51, 16, 58 and 53. Infection rate was higher for high-risk HPV than low-risk HPV genotype. Single infection was more common than its multiple infection. In addition, 7.48% (95%CI: 7.22%-7.75%) women were TCT positive, of whom 4.58% (95%CI: 4.40%-4.76%), 2.54% (2.40%-2.69%), 0.27% (95%CI: 0.23%-0.31%) had atypical squamous cells, low-grade squamous intraepithelial lesions and high-grade squamous intraepithelial lesions, respectively. Overall and subtype HPV infection rates increased with severity of abnormal cervical cytology. The most prevalent HPV genotypes were 52, 58 and 16 in women with abnormal cervical cytology. Conclusions: HPV prevalence remains at a high level in Shenzhen. This study suggests that attention should be paid to HPV screening, especially in young, perimenopausal women and in high risk HPV genotype infection. Timely follow-up and cervical cytology screening are required for women with high-risk HPV infection or persistent infection. Future vaccination strategies should take account of prevalent HPV genotype.

Geochemical cycle of mercury associated with wet deposition and inflows in a subalpine wetland

Subalpine wetland is a mercury (Hg) sensitive ecosystem, but there is poor understanding of Hg behavior in this typical wetland. Here, distribution and speciation of Hg in waters of a subalpine wetland (Dajiuhu) in China were investigated, and an initial model of the Hg geochemical cycle in the wetland was established based on Hg mass balance calculations. Concentrations of both total Hg (THg, 9.52 ± 6.61 ng L^-1) and total methyl mercury (TMeHg, 0.34 ± 0.44 ng L^-1) in the waters during the wet season were higher than in the dry season. The majority of THg was in dissolved form whereas most TMeHg was in particle form. The geochemical models suggested that, due to the wet deposition and surface runoff, the input of THg and TMeHg into the wetland in the wet season (222 and 2.74 g year^-1, respectively) was higher than that in the dry season (57.9 and 1.15 g year^-1, respectively). The output of THg and TMeHg from the wetland underground runoff in the wet season was estimated to be 154 and 2.51 g year^-1, respectively, and in the dry season was 15.9 and 0.43 g year^-1, respectively. Other losses of Hg were due to volatilization of Hg⁰ from the sediment water (30.5 and 12.5 g year^-1 in the wet and dry seasons, respectively). The flux of the settling of particulate Hg in the wet season was higher than that in the dry season. The fluxes of Hg diffusion from the porewater were relatively low in comparison to the fluxes of inflows and wet deposition. The flux of oxidation was higher than reduction, while the flux of methylation was higher than demethylation. These results indicated that the elevated levels of THg and MeHg in the Dajiuhu wetland are a consequence of rainfall and surface runoff inputs.

High-power vertical external-cavity surface-emitting laser emitting switchable wavelengths

In this paper we reported on the optically pumped VECSELs with switchable lasing wavelengths. The two lasing wavelengths of λ ≈ 954 nm and 1003 nm are generated at different pumping powers from the same gain chip. The thermal rollover of output power is observed twice, and the first rollover on the power curve indicates the switch of lasing wavelength. During the operation of our VECSEL, the increase of pumping power changes the temperature within the gain chip, and thus the gain spectrum is tuned to the one of two modes, which is defined by the dips on the reflectivity spectrum. The maximum output power of each wavelength exceeds 2.2 W at -5 °C. The dual-wavelength emission at λ ≈954 nm and 1003 nm is also demonstrated, and the output power of the dual-wavelength emission reached nearly 2 W.

High-order DBR semiconductor lasers: effect of grating parameters on grating performance: publisher's note

This publisher's note amends the author listing in Appl. Opt.59, 8789 (2020)APOPAI0003-693510.1364/AO.402699.

High-order DBR semiconductor lasers: effect of grating parameters on grating performance

In this paper, a high-order distributed Bragg reflector (DBR) semiconductor laser operating at 1064 nm is demonstrated based on simulation analysis. To get optimal Bragg grating characteristics, four parameters of the Bragg grating were analyzed in detail. Forty-nine-order Bragg gratings were designed with a reflectivity of 6% and a FWHM of 3 nm, which can realize mode selection while lasing. The Bragg gratings were designed to maximize the use of light. Transmission of the rear laser facet is theoretically 0. This simulation result provides a simple and efficient DBR semiconductor laser scheme without cavity surface coating.

Risks related to heavy metal pollution in urban construction dust fall of fast-developing Chinese cities

Urban construction is a major contributor to air pollution, but few studies have examined heavy metal pollution in urban areas caused by construction dust fall. We measured the concentrations of Cr, Ni, Cu, Zn, Pb, Cd, and Hg and particle size distribution in dust fall from various construction activities in seven fast-developing cities in China and conducted a health risk assessment. Mean metal concentrations in construction dust fall were on the order of Zn (246.3 mg/kg) > Cr (94.2 mg/kg) > Pb (56.5 mg/kg) > Cu (53.6 mg/kg) > Ni (22.8 mg/kg) > Cd (0.68 mg/kg) > Hg (0.08 mg/kg). Cu and Zn were positively correlated in areas of subway and building construction, and Pb and Cd were positively correlated in areas of road construction, likely because of the materials specific to these activities. Enrichment factors for heavy metals at all sampling sites were on the order of Cd (10.4) > Zn (6.37) > Cu (4.25) > Pb (3.84) > Hg (2.41) > Cr (2.02) > Ni (1.32). The enrichment factors for all metals except Zn indicated that heavy metal pollution was highest in road construction, followed by building and subway construction. Non-carcinogenic risks to children (hazard index >1) were 1.01-1.08 in four of the seven sampling sites, indicating possible risk from deposition of construction dust fall. In contrast, the hazard index for adults was <1 at the seven cities and total carcinogenic risks (<1 × 10^-6) were at acceptable levels. An integrated ecological risk assessment demonstrated that heavy metal particles in construction dust fall in two of the cities (Shijiazhuang and Qingdao) were likely to be suspended in the atmosphere. Our study of heavy metal pollution in construction dust fall provides data on ecological and human health impacts and suggests that extensive measures are required to control construction dust fall in China.