Atomic Evolution Mechanism and Suppression of Edge Threading Dislocations in Nitride Remote Heteroepitaxy.

The majority of dislocations in nitride epilayers are edge threading dislocations (TDs), which diminish the performance of nitride devices. However, it is extremely difficult to reduce the edge TDs due to the lack of available slip systems. Here, we systematically investigate the formation mechanism of edge TDs and find that besides originating at the coalescence boundaries, these dislocations are also closely related to geometrical misfit dislocations at the interface. Based on this understanding, we propose a novel strategy to reduce the edge TD density of the GaN epilayer by nearly 1 order of magnitude via graphene-assisted remote heteroepitaxy. The first-principles calculations confirm that the insertion of graphene dramatically reduces the energy barrier required for interfacial sliding, which promotes a new strain release channel. This work provides a unique approach to directly suppress the formation of edge TDs at the source, thereby facilitating the enhanced performance of photoelectronic and electronic devices.

[Determination of 14 ß-agonists in animal meat by ultra high performance liquid chromatography-tandem mass spectrometry].

The addition of ß-agonists to animal feed can significantly improve the lean-meat rate of pigs, cattle, sheep, and other animals. However, the food residues of ß-agonists are harmful to human health. When meat with ß-agonist residues is consumed, poisoning symptoms such as palpitation, dizziness, and muscle tremors may develop, and damage to the cardiovascular system, liver, and kidney may occur. In this study, a method based on ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) was established for the rapid detection of 14 ß-agonists (clenbuterol, salbutamol, ractopamine, clorprenaline, terbutaline, tulobuterol, bromobuterol, bambuterol, zilpaterol, mabuterol, fenoterol, arformoterol, cimaterol, and cimbuterol) in animal food sources. The sample pretreatment method and chromatographic conditions were optimized. The samples were hydrolyzed with ß-glucuronidase hydrochloride/aryl sulfate esterase in ammonium acetate buffer (pH 5.2). Enzymatic hydrolysis was performed in a constant-temperature water bath ((36±2) ℃) oscillator for 16 h. The samples were cooled to room temperature and extracted with 0.5% formic acid acetonitrile. NaCl was added to separate the organic and aqueous phases, and 5 mL of the upper organic layer was purified using a one-step purification solid-phase extraction column. After drying with nitrogen at 50 ℃, the residue was dissolved in 0.4 mL of 0.2% formic acid aqueous solution. The samples were passed through a 0.22 µm filter and detected by UHPLC-MS/MS with gradient elution using acetonitrile and 0.1% formic acid aqueous solution as the mobile phases. The analytes were separated on a Phenomenex Kinetex F5 column and detected by positive-ion scanning in multiple-reaction monitoring (MRM) mode. Internal and external standard methods were used for quantitative analysis. The effects of the extract pH, solid-phase extraction column, purification method, and dissolved solution on the extraction efficiency were optimized during pretreatment. UHPLC-quadrupole time-of-flight MS was used to verify the purification effect of the one-step purification solid-phase extraction column, and the results indicated that this type of column could remove most of the phospholipids, sphingolipids, and glycerides in the sample extract. The factors influencing the different chromatographic columns and mobile phases were investigated. MS scanning was conducted in positive-ion mode with needle pump injection in mass-only mode, and the two daughter ions with the highest responses for each target were selected as the quantitative and qualitative ions. The declustering potential (DP) and collision energy (CE) of each ion were separately optimized in MRM mode. The switching mode of the mass spectrum and waste liquid was used, and the mobile phase was switched to waste liquid after all the target peaks were removed. These steps ensured that impurities in the sample flowed out of the column in a timely manner and that the effects of excessive impurities on the mass spectra were avoided. The 14 ß-agonists showed good linear relationships in the range of 1.0-50 µg/L, with correlation coefficients of >0.99. The limits of detection (LODs) and quantification (LOQs) were in the range of 0.1-0.2 and 0.3-0.6 µg/kg, respectively. The average recoveries of the 14 ß-agonists ranged from 70.25% to 117.48%, with relative standard deviations (RSDs) in the range of 0.63%-14.29% at low, medium, and high spiked levels. Pork, beef, and mutton samples were selected and analyzed using the developed method. The results were close to those of the national standard method, indicating that the method is accurate and reliable. Moreover, the proposed method has good stability and high accuracy; thus, it is suitable for the qualitative and quantitative determination of ß-agonists in animal meat.

Self-Cross-Linkable Chitosan-Alginate Complexes Inspired by Mussel Glue Chemistry.

In this study, mussel-inspired chemistry, based on catechol-amine reactions, was adopted to develop self-cross-linkable chitosan-alginate (Chi-Alg) complexes. To do so, the biopolymers were each substituted with ∼20% catechol groups (ChiC and AlgC), and then four complex combinations (Chi-Alg, ChiC-Alg, Chi-AlgC, ChiC-AlgC) were prepared at the surface and in bulk solution. Based on QCM-D and lap shear adhesion tests, the complex with catechol only on Chi (ChiC-Alg) did not show a significant variation from the control complex (Chi-Alg). Conversely, the complexes with catechol on alginate (Chi-AlgC and ChiC-AlgC) rendered a self-cross-linking property and enhanced cohesive properties.

Lattice modulation strategies for 2D material assisted epitaxial growth.

As an emerging single crystals growth technique, the 2D-material-assisted epitaxy shows excellent advantages in flexible and transferable structure fabrication, dissimilar materials integration, and matter assembly, which offers opportunities for novel optoelectronics and electronics development and opens a pathway for the next-generation integrated system fabrication. Studying and understanding the lattice modulation mechanism in 2D-material-assisted epitaxy could greatly benefit its practical application and further development. In this review, we overview the tremendous experimental and theoretical findings in varied 2D-material-assisted epitaxy. The lattice guidance mechanism and corresponding epitaxial relationship construction strategy in remote epitaxy, van der Waals epitaxy, and quasi van der Waals epitaxy are discussed, respectively. Besides, the possible application scenarios and future development directions of 2D-material-assisted epitaxy are also given. We believe the discussions and perspectives exhibited here could help to provide insight into the essence of the 2D-material-assisted epitaxy and motivate novel structure design and offer solutions to heterogeneous integration via the 2D-material-assisted epitaxy method.

The Structural Evolution of Semipolar (11-22) Plane AlN Tem-Plate on m-Plane Sapphire Prepared by Sputtering and High Temperature Annealing.

In this work, the epitaxial semipolar (11-22) AlN was prepared on nonpolar m-sapphire substrate by combining sputtering and high-temperature annealing. According to our systematic measurements and analysis from XRD, Raman spectra, and AFM, the evolution of crystalline structure and morphology was investigated upon increasing AlN thickness and annealing duration. The annealing operation intensively resets the lattice and improves the crystalline quality. By varying the film thickness, the contribution from the AlN-sapphire interface on crystalline quality and lattice parameters during the annealing process was investigated, and its contribution was found to be not so obvious when the thickness increased from 300 nm to 1000 nm. When the annealing was performed under durations from 1 to 5 h, the crystalline quality was found unchanged; meanwhile, the evolution of morphology was pronounced, and it means the crystalline reorganization happens prior to morphology reset. Finally, the annealing treatment enabled a zig-zag morphology on the AlN template along the sapphire [0001] direction in the plane, which potentially affects the subsequent device epitaxy process. Therefore, our results act as important experience for the semipolar nitride semiconductor laser device preparation, particularly for the epitaxy of microcavity structure through providing the crystalline evolution.

Deep-Ultraviolet Micro-LEDs Exhibiting High Output Power and High Modulation Bandwidth Simultaneously.

Deep-ultraviolet (DUV) solar-blind communication (SBC) shows distinct advantages of non-line-of-sight propagation and background noise negligibility over conventional visible-light communication. AlGaN-based DUV micro-light-emitting diodes (µ-LEDs) are an excellent candidate for a DUV-SBC light source due to their small size, low power consumption, and high modulation bandwidth. A long-haul DUV-SBC system requires the light source exhibiting high output power, high modulation bandwidth, and high rate, simultaneously. Such a device is rarely reported. A parallel-arrayed planar (PAP) approach is here proposed to satisfy those requirements. By reducing the dimensions of the active emission mesa to micrometer scale, DUV µ-LEDs with ultrahigh power density are created due to their homogeneous injection current and enhanced planar isotropic light emission. Interconnected PAP µ-LEDs with a diameter of 25 µm are produced. This device has an output power of 83.5 mW with a density of 405 W cm-2 at 230 mA, a wall-plug efficiency (WPE) of 4.7% at 155 mA, and a high -3 dB modulation bandwidth of 380 MHz. The remarkable high output power and efficiency make those devices a reliable platform to develop high-modulation-bandwidth wireless communication and to meet the requirements for bio-elimination.

A plant-by-plant strategy for high-ambition coal power phaseout in China.

More than half of current coal power capacity is in China. A key strategy for meeting China's 2060 carbon neutrality goal and the global 1.5 °C climate goal is to rapidly shift away from unabated coal use. Here we detail how to structure a high-ambition coal phaseout in China while balancing multiple national needs. We evaluate the 1037 currently operating coal plants based on comprehensive technical, economic and environmental criteria and develop a metric for prioritizing plants for early retirement. We find that 18% of plants consistently score poorly across all three criteria and are thus low-hanging fruits for rapid retirement. We develop plant-by-plant phaseout strategies for each province by combining our retirement algorithm with an integrated assessment model. With rapid retirement of the low-hanging fruits, other existing plants can operate with a 20- or 30-year minimum lifetime and gradually reduced utilization to achieve the 1.5 °C or well-below 2 °C climate goals, respectively, with complete phaseout by 2045 and 2055.

Sec-Eliminating the SARS-CoV-2 by AlGaN Based High Power Deep Ultraviolet Light Source.

The world-wide spreading of coronavirus disease (COVID-19) has greatly shaken human society, thus effective and fast-speed methods of non-daily-life-disturbance sterilization have become extremely significant. In this work, by fully benefitting from high-quality AlN template (with threading dislocation density as low as ≈6×108 cm-2) as well as outstanding deep ultraviolet (UVC-less than 280 nm) light-emitting diodes (LEDs) structure design and epitaxy optimization, high power UVC LEDs and ultra-high-power sterilization irradiation source are achieved. Moreover, for the first time, a result in which a fast and complete elimination of SARS-CoV-2 (the virus causes COVID-19) within only 1 s is achieved by the nearly whole industry-chain-covered product. These results advance the promising potential in UVC-LED disinfection particularly in the shadow of COVID-19.

Case-based reasoning based on grey-relational theory for the optimization of boiler combustion systems.

Boiler combustion optimization is an important method to improve the flexibility of thermal power units and ensures the stability of unit operation. However, time-variability of boiler combustion systems and time-consuming optimization methods pose great challenges for the use of boiler combustion optimization techniques because many optimization methods cannot be used online in practical engineering due to time constraints. In this paper, we propose a case-based reasoning optimization method based on grey-relational theory (GR-CBR) for online optimization of a boiler combustion system. After the introduction of the proposed algorithm, we discuss the potential of applying the proposed GR-CBR optimization method to a boiler combustion system; a case study of an existing fossil fuel power plant is conducted to demonstrate the feasibility of the proposed method. A least-squares support vector machine (LS-SVM) model of the boiler combustion process is established by using the real-time operation data of a 350-MW coal-based power plant. Based on the model, a non-linear global optimization algorithm is proposed to obtain the optimal case base and real-time data mining and online optimization are used to achieve efficient and stable boiler combustion optimization. The results of combining offline optimization with online querying show that this approach is suitable for online real-time combustion optimization, and provides support for power plant operators for optimization and condition monitoring to improve boiler efficiency, reduce NOx emissions, and ensure stable and efficient operation of the power system.

Analysis of Anesthesia Methods in Percutaneous Kyphoplasty for Treatment of Vertebral Compression Fractures.

Aim: Percutaneous kyphoplasty (PKP) is a routine operation for the treatment of vertebral compression fracture (VCF). Both local anesthesia and general anesthesia are widely used for PKP. However, which type of anesthesia is better for PKP still remains uncertain. This study aimed to find out whether local anesthesia or general anesthesia is more suitable for PKP. Methods: This is a retrospective clinical trial. A total of 85 single-level VCF patients who received PKP 12 months ago were recruited in this study. 45 patients who received local anesthesia were in group L, and 40 patients with general anesthesia were in group G. Clinical, radiological, and economic data between the two groups were collected. Results: No difference was found on preoperative data between the two groups. The duration of operation time in group L was longer than that in group G. Within 12 months after PKP, more complications happened in group G than those in group L. Results: No difference was found on preoperative data between the two groups. The duration of operation time in group L was longer than that in group G. Within 12 months after PKP, more complications happened in group G than those in group L. Conclusion: Both local anesthesia and general anesthesia were reliable for PKP. However, local anesthesia was more efficient and safer with less expense and more bearable pain when compared with general anesthesia.

Amine-Triggered Dopamine Polymerization: From Aqueous Solution to Organic Solvents.

Dopamine (DA) polymerization has received significant attention in many fields, however, almost all of the works are limited to aqueous solution and hamper its wide application. This paper reports that amines can trigger DA polymerization by capturing the H+ from DA hydrochloride and intermediates to accelerate the generation of radical species in water or organic solvents. Increasing concentration and decreasing pKb of amines cause the reaction equilibrium to shift toward the product polydopamine (PDA). Water-soluble and easily-removable Na2 SO4 nanowires and NaCl cubes can be used as templates to prepare different morphologies of hollow PDA structures by DA polymerization in ethanol solution. The carbonization production of PDA nanotubes at 900 °C (PDNC-900) is obtained and demonstrates electrochemical activity in the oxygen reduction reaction that is comparable to that of Pt/C.

Broadband light-absorption InGaN photoanode assisted by imprint patterning and ZnO nanowire growth for energy conversion.

In this research, an InGaN-based photoanode with a broadband light-absorption range from ultraviolet to green, patterned by imprint lithography and branched by ZnO nanowires, has been applied to water splitting. Over the solar spectrum range, the absorbance increases due to the scattering effect of the micro-structure compared to that of flat surface InGaN, which reaches a maximum of over 90% at 380 nm as ZnO nanowires are further employed in this novel photoanode. Consequently, the induced photocurrent density of the InGaN photoanode with a domelike structure and ZnO nanowires on the surface shows a remarkable enhancement of seven times that of the one with a flat surface. Further investigation indicates the wet-etching process for defect removal has an essential impact on photocurrent efficiency. This design demonstrates an innovative approach for water splitting.

Broadband full-color monolithic InGaN light-emitting diodes by self-assembled InGaN quantum dots.

We have presented broadband full-color monolithic InGaN light-emitting diodes (LEDs) by self-assembled InGaN quantum dots (QDs) using metal organic chemical vapor deposition (MOCVD). The electroluminescence spectra of the InGaN QDs LEDs are extremely broad span from 410 nm to 720 nm with a line-width of 164 nm, covering entire visible wavelength range. A color temperature of 3370 K and a color rendering index of 69.3 have been achieved. Temperature-dependent photoluminescence measurements reveal a strong carriers localization effect of the InGaN QDs layer by obvious blue-shift of emission peak from 50 K to 300 K. The broadband luminescence spectrum is believed to be attributed to the injected carriers captured by the different localized states of InGaN QDs with various sizes, shapes and indium compositions, leading to a full visible color emission. The successful realization of our broadband InGaN QDs LEDs provide a convenient and practical method for the fabrication of GaN-based monolithic full-color LEDs in wafer scale.

InGaN-based photoanode with ZnO nanowires for water splitting.

The water splitting properties of InGaN photoanodes equipped with ZnO nanowires were examined in this study. Over the solar spectrum range, the absorbance exhibited a remarkable increase due to the enhanced light absorption caused by the ZnO nanowires. By varying the ZnO nanowires length, the photo-to-current density of photoanodes was increased from 0.017 to 0.205 mA/cm2 at 1.23 V versus reversible hydrogen electrode. Consequently, the incident-photon-to-current efficiency was increased by a factor of 5.5 as the ZnO nanowires growth time increased from 2 to 4 h. The results of this research demonstrate the importance of light absorbance and the surface reaction sites of photoanodes on energy harvesting.

Enhanced performance of InGaN-based light emitting diodes through a special etch and regrown process in n-GaN layer.

We reported that the peak efficiency together with the efficiency droop in InGaN-based light emitting diodes could be effectively modified through a simple and low-cost etch-regrown process in n-GaN layer. The etched n-GaN template contained pyramid arrays with inclined side planes. The following lateral overgrowth process from the etched n-GaN template substantially reduced the edge dislocation density and residential compressive strain in epilayers. The efficiency droop of LED samples thus could be modified due to the reduced polarization field, resulting from the strain relaxation in epilayers. What is more, the peak efficiency and reverse current leakage were also modified due to the reduction of dislocations.

[The quantitative classification and survey of sanitation of urban secondary water supply in Haidian district of Beijing].

OBJECTIVE: To investigate the sanitary status of urban secondary water supply facilities in Haidian district of Beijing. METHODS: Adopting the quantitative classification table drafted by the Bureau for Sanitation Inspection and Supervision of Haidian district, we carried quantitative classification (A, B, C grade) on all 1725 secondary water supply facilities in Haidian district for two times. At the same time, we collected 20 residential areas with stratified random sampling method. As the public points in the first quantitative classification, the effect of level publicity on changing the sanitary grade of the secondary water supply facilities were observed. RESULTS: In the first two times of quantitative classification, A-level and B-level secondary water supply facilities took up 81.04% (1398/1725) and 89.04% (1536/1725) of all secondary water supply facilities respectively; the ratio of effective sanitary permits achieved 86.14% (1486/1725) and 92.35% (1593/1725) respectively; and the ratio of effective water quality test reports achieved 86.60% (1494/1725) and 97.10% (1675/1725) respectively. There were 52 secondary water supply facilities in 20 collected areas, including 8 A-level, 27 B-level and 17 C-level secondary water supply facilities before level publicity, and 19, 29 and 4 after level publicity. The impact of level publicity on changing the sanitary grade of the secondary water supply facilities was statistically significant (χ(2) = 12.60, P = 0.002). CONCLUSION: The city secondary water supply facilities in Haidian district are overall in good sanitary conditions. Quantitative classification and level publicity can effectively improve the sanitary status of secondary water supply facilities.