The prediction on in-line vortex-induced vibration of slender marine structures

The in-line （IL） vortex-induced vibration （VIV） that occurs frequently in ocean engineering may cause severe fatigue damage in slender marine structures. To the best knowledge of the authors, in existing literatures, there is no efficient analytical model for predicting pure IL VIV. In this paper, a wake oscillator model capable of analyzing the IL VIV of slender marine structures has been developed. Two different kinds of van der Pol equations are used to describe the near wake dynamics related to the fluctuating nature of symmetric vortex shedding in the first excitation region and alternate vortex shedding in the second one. Some comparisons are carried out between the present model results and experimental data. It is found that many phenomena observed in experiments could be reproduced by the present wake oscillator model.

Comparison of very-high-frequency ultrasound assessment of radial arterial wall layers after first and repeated transradial coronary procedures

Background Transradial coronary procedure （TRP） traumatizes the radial artery （RA）, especially resulting in changes to arterial wall morphology. This study explored the significance of the early onset of traumatic effects to wall layers of the RA following the first TRP （FTRP） and repeat TRP （RTRP） using very-high-frequency ultrabiomicroscopy （VHFUBM）. Methods A total of 1431 patients that re- ceived TRP were divided into the FTRP group that comprised 781 patients and the RTRP group that comprised 650 patients depending on the number of procedures. Two-dimensional RA images were acquired by 30-55 MHz ultrasound one day before and one day after the pro- cedure. Results After TRP, the incidence of intimal tears, medial dissections and external elastic lamina fracture were greater in the RTRP （P 〈 0.001）. The RTRP group showed significantly thicker intimal thickness （IT）, media thickness （MT）, adventitia thickness and all complex layer thicknesses as compared with the FTRP group （P 〈 0.001）. Conclusions Multivariate linear regression analysis discovered that repeated TRP and other observations were independent predictors of increased IT in post-operative RA. VHFUBM provides an approach to study structural and histopathological injury in the wall layers of RA which showed increased trauma to the RA following RTRP.

Recombinant Apoptin Gene Retrovirus Induces Apoptosis in Human Breast Cancer Cells 435

Objective： To construct recombinant Apoptin gene （vp3） retrovirus pLVP3 and to study its apoptosis inducing effect on human breast cancer cells 435 as well as to discuss its mechanism in vitro and in vivo. Methods： vp3 gene was cloned and recombinated into retrovirus vector pLP-LNCX-VP3 （pLVP3） at loxP site, which was transformed into package cell line PT67 and then into NIH3T3 cells for titer assay. The human breast cancer cell line 435 was infected with retrovirus pLVP3, and then MTT assay and Western blotting were adopted to detect cellular proliferation and Apoptin protein expression. Forty-eight hours after infection flow cytometry （FCM） was used for apoptosis detection and Surface Enhanced Laser Desorption Ionization-Time of Flight-Mass Spectrometry （SELDI-TOF-MS） was used for protein profile assay. Nude mice model of human breast cancer cells 435 was set up to observe the tumor inhibiting rates of pLVP3, and TUNEL assay was used to detect tumor apoptosis as well as real-time PCR for vp3 gene expression. Results： Recombinant plasmid pLVP3 was successfully constructed. Virus titer reached to 5×10^8 pfu/ml in the PT67 culture supernatant. Forty-eight hours after infection, cellular inhibition rate was 65.1% in MTT assay, higher than that in blank control （P〈0.05） and Apoptin protein expressed more in test group in Western blotting. FCM assay showed apoptotic peaks with a percentage of 15.42%. SELDI-TOF-MS findings suggested that two protein peaks, M_2544.1＋H and M_3712.4＋H, were statistically different between infection group and control group （P〈0.05）. The tumor inhibition rates in pLVP3 group were 65.52% and 68.23%, much higher than that of control group （t=4.06, P〈0.01）. TUNEL assay findings showed that positive yellow stains were seen in pLVP3 retrovirus group and 5-FU positive control group without difference （t1=1.05, t2=0.84, P〉0.05）. Conclusion： The experiment demonstrated that vp3 could induce apoptosis in tumor cells in vivo and in vitro, which laid a basis for further study on molecular mechanism of tumor cell apoptosis induced by Apoptin and provided valuable reference for tumor gene therapy.

Transfection of the glial cell line-derived neurotrophic factor gene promotes neuronal differentiation

Glial cell line-derived neurotrophic factor recombinant adenovirus vector-transfected bone marrow mesenchymal stem cells were induced to differentiate into neuron-like cells using inductive medium containing retinoic acid and epidermal growth factor. Cell viability, micro- tubule-associated protein 2-positive cell ratio, and the expression levels of glial cell line-derived neurotrophic factor, nerve growth factor and growth-associated protein-43 protein in the su- pernatant were significantly higher in glial cell line-derived neurotrophic factor/bone marrow mesenchymal stem cells compared with empty virus plasmid-transfected bone marrow mes- enchymal stem cells. Furthermore, microtubule-associated protein 2, glial cell line-derived neurotrophic factor, nerve growth factor and growth-associated protein743 mRNA levels in cell pellets were statistically higher in glial cell line-derived neurotrophic factor/bone marrow mesen- chymal stem cells compared with empty virus plasmid-transfected bone marrow mesenchymal stem cells. These results suggest that glial cell line-derived neurotrophic factor/bone marrow mesenchymal stem cells have a higher rate of induction into neuron-like cells, and this enhanced differentiation into neuron-like cells may be associated with up-regulated expression of glial cell line-derived neurotrophic factor, nerve growth factor and growth-associated protein-43.

Synthesis of mechanically robust porous carbon monoliths for CO2 adsorption and separation

Porous carbon materials with developed porosity,high surface area and good thermal-and chemicalresistance are advantageous for gas adsorption and separation.However,most carbon adsorbents are in powder form which exhibit high pressure drop when deployed in practical separation bed.While monolithic carbons have largely addressed the pulverization problem and preserved kinetics and usually suffer from abrasion during multiple adsorption-desorption cycles.Herein,we proposed the designed synthesis of mechanically robust carbon monoliths with hierarchical pores,solid nitrogen-containing framework.The synthesis started with the polymerization of resorcinol and formaldehyde under weakly acidic conditions generated from cyanuric acid,and then an appropriate amount of hexamethylenetetramine(HMTA)was added as a crosslinker to prompt the formation of three dimensional frameworks.After carbonization process,the as-obtained porous carbon monoliths have a high radial compressive strength of 886 N/cm as well as a BET specific surface area of up to 683 m2/g.At approximately 1 bar,the CO2 equilibrium capacities of the monoliths are in the range of 3.1–4.0 mmol/g at 273 K and of 2.3–3.0 mmol/g at 298 K,exhibiting high selectivity for the capture of CO2 over N2 from a stream which consists of 16.7%(v%)CO2 in N2.Meanwhile,they undergo a facile CO2 release in an argon stream at 298 K,indicating a good regeneration capacity.After cycle testing,sieving and regeneration,the adsorbent has no mass loss,compared to that of its fresh counterpart.

The serum anion gap is associated with disease severity and all-cause mortality in coronary artery disease

Objective To evaluate the associations between the serum anion gap （AG） with the severity and prognosis of coronary artery disease （CAD）. Methods We measured serum electrolytes in 18,115 CAD patients indicated by coronary angiography. The serum AG was calculated according to the equation： AG = Na^＋ [（mmol/L） ＋ K^＋ （mmol/L）] - [Cl^- （mmol/L） ＋ HCO3^- （mmol/L）]. Results A total of 4510 （24.9%） participants had their AG levels greater than 16 mmol/L. The serum AG was independently associated with measures of CAD severity, including more severe clinical types of CAD （P 〈 0.001） and worse cardiac function （P = 0.004）. Patients in the 4th quartile of serum AG （≥ 15.92 mmol/L） had a 5.171-fold increased risk of 30 days all-cause death （P 〈 0.001）. This association was robust, even after adjustment for age, sex, evaluated glomerular filtration rate [hazard ratio （HR）： 4.861, 95% confidence interval （CI）： 2.150–10.993, P 〈 0.001], clinical diagnosis, severity of coronary artery stenosis, cardiac function grades, and other confounders （HR： 3.318, 95% CI： 1.76–2.27, P = 0.009）. Conclusion In this large population-based study, our findings reveal a high percentage of increased serum AG in CAD. Higher AG is associated with more severe clinical types of CAD and worse cardiac function. Furthermore, the increased serum AG is an independent, significant, and strong predictor of all-cause mortality. These findings support a role for the serum AG in the risk-stratification of CAD.

Machine learning-based estimates of aboveground biomass of subalpine forests using Landsat 8 OLI and Sentinel-2B images in the Jiuzhaigou National Nature Reserve,Eastern Tibet Plateau

Accurate estimates of forest aboveground biomass(AGB)are critical for supporting strategies of ecosystem conservation and climate change mitigation.The Jiuzhaigou National Nature Reserve,located in Eastern Tibet Plateau,has rich forest resources on steep slopes and is very sensitive to climate change but plays an important role in the regulation of regional carbon cycles.However,an estimation of AGB of subalpine forests in the Nature Reserve has not been carried out and whether a global biomass model is available has not been determined.To provide this information,Landsat 8 OLI and Sentinel-2B data were combined to estimate subalpine forest AGB using linear regression,and two machine learning approaches–random forest and extreme gradient boosting,with 54 inventory plots.Regardless of forest type,Observed AGB of the Reserve varied from 61.7 to 475.1 Mg hawith an average of 180.6 Mg ha.Results indicate that integrating the Landsat 8 OLI and Sentinel-2B imagery significantly improved model efficiency regardless of modelling approaches.The results highlight a potential way to improve the prediction of forest AGB in mountainous regions.Modelled AGB indicated a strong spatial variability.However,the modelled biomass varied greatly with global biomass products,indicating that global biomass products should be evaluated in regional AGB estimates and more field observations are required,particularly for areas with complex terrain to improve model accuracy.

Preparation of novel biodegradable pHEMA hydrogel for a tissue engineering scaffold by microwave-assisted polymerization

Objective:To prepare a novel biodegradable poly(2-hydroxyethylmethacrilate)(pHEMAt hydrogel as tissue engineering scaffold.Methods:The pHEMA hydrogel was synthesized by microwaveassisted polymerization using 2-hydroxyethyl methacrylale(IIEMA)as the raw material,potassium persulfate as the initiator,and PCI.X as the cross-linking additive.The hvdrogels was characterized with FTIR and NMR spectroscopy.The physical and chemical properties of the prepared hydrogel were evaluated,and its degradation performance was tested.The cytotoxicity of the optimum composite hydrogel was measured by an MTT assay to confirm the feasibility of its use in tissue engineering.Results:The optimum conditions under which the hydrogel was prepared by microwave-assisted polymerization are as follows:1.5 g cross-linking additive,0.3 g initiator,reaction temperature of 80°C,and microwave power of 800 W.Degradation studies showed good degradation profiles with 75%in 17 days.Additionally,the hydrogels did not elicit any cytotoxic response in in vitro cytotoxic assays.Conclusion:A biodegradable pIIEMA hydrogel was successfully prepared by microwave-assisted polymerization,as confirmed from FTIR and NMR results.The hydrogel shows promising applications in tissue engineering,and its healing ability and biocompatibilily will be evaluated in detail in the future.

The roles of serum IL-18, IL-10, TNF-α and sIL-2R in patients with chronic hepatitis C

To identify the roles of serum IL-18, IL- 10, TNF-α and sIL-2R in the pathogenisis of chronic hepatitis C and the effects of interferon on the men- tioned serum cytokines. Methods: The levels of IL-18, IL-10, TNF-α and sIL-2R were detected in 10 healthy controls, 24 a- symptomatic HCV carriers, and 27 patients with chronic hepatitis C (before and after IFN treatment) by enzyme linked immunosorbent assay (ELISA). Results: The levels of IL-18, IL-10, TNF-α and sIL- 2R in the patients of chronic hepatitis C were higher than those in the healthy controls (P<0.05) and in asymptomatic HCV carriers (P<0. 05). The values of the mentioned cytokines showed a significant posi- tive correlation to GPT. The levels of the mentioned cytokines decreased obviously after IFN treatment (P <0. 05), while the serum levels of IL-10 and sIL-2R reduced in sequence in no-response group, partial- response group and complete-response group. Conclusions: IL-18, IL-10, TNF-α and sIL-2R co- participate in the pathogenisis of chronic hepatitis C, and are used to evaluate the effect of IFN on the im- mune state of organisms, and IL-10 and sIL-2R are important for predicting the anti-viral efficacy of IFN.

High-Order Bound-Preserving Finite Difference Methods for Multispecies and Multireaction Detonations

In this paper,we apply high-order finite difference(FD)schemes for multispecies and multireaction detonations(MMD).In MMD,the density and pressure are positive and the mass fraction of the ith species in the chemical reaction,say zi,is between 0 and 1,withΣz_(i)=1.Due to the lack of maximum-principle,most of the previous bound-preserving technique cannot be applied directly.To preserve those bounds,we will use the positivity-preserving technique to all the zi'is and enforceΣz_(i)=1 by constructing conservative schemes,thanks to conservative time integrations and consistent numerical fluxes in the system.Moreover,detonation is an extreme singular mode of flame propagation in premixed gas,and the model contains a significant stiff source.It is well known that for hyperbolic equations with stiff source,the transition points in the numerical approximations near the shocks may trigger spurious shock speed,leading to wrong shock position.Intuitively,the high-order weighted essentially non-oscillatory(WENO)scheme,which can suppress oscillations near the discontinuities,would be a good choice for spatial discretization.However,with the nonlinear weights,the numerical fluxes are no longer“consistent”,leading to nonconservative numerical schemes and the bound-preserving technique does not work.Numerical experiments demonstrate that,without further numerical techniques such as subcell resolutions,the conservative FD method with linear weights can yield better numerical approximations than the nonconservative WENO scheme.

Maximum-Principle-Preserving Local Discontinuous Galerkin Methods for Allen-Cahn Equations

In this paper, we study the classical Allen-Cahn equations and investigate the maximum- principle-preserving (MPP) techniques. The Allen-Cahn equation has been widely used in mathematical models for problems in materials science and fluid dynamics. It enjoys the energy stability and the maximum-principle. Moreover, it is well known that the Allen- Cahn equation may yield thin interface layer, and nonuniform meshes might be useful in the numerical solutions. Therefore, we apply the local discontinuous Galerkin (LDG) method due to its flexibility on h-p adaptivity and complex geometry. However, the MPP LDG methods require slope limiters, then the energy stability may not be easy to obtain. In this paper, we only discuss the MPP technique and use numerical experiments to dem-onstrate the energy decay property. Moreover, due to the stiff source given in the equation, we use the conservative modified exponential Runge-Kutta methods and thus can use rela-tively large time step sizes. Thanks to the conservative time integration, the bounds of the unknown function will not decay. Numerical experiments will be given to demonstrate the good performance of the MPP LDG scheme.

Hydraulic role in differential stomatal behaviors at two contrasting elevations in three dominant tree species of a mixed coniferous and broad-leaved forest in low subtropical China

Quantifying the variation in stomatal behavior and functional traits of trees with elevation can provide a better understanding of the adaptative strategies to a changing climate. In this study, six water-and carbon-related functional traits were examined for three dominant tree species, Schima superba, Pinus massoniana and Castanopsis chinensis, in a mixed coniferous and broad-leaved forest at two elevations(70 and 360 m above sea level,respectively) in low subtropical China. We hypothesized that trees at higher elevations would develop more efficient strategies of stomatal regulations and greater water transport capacity to cope with more variable hydrothermal conditions than those at lower elevations. Results show that the hydraulic conductivity did not differ between trees at the two elevations, contrary to our expectation. The C. chinensis trees had greater values of leaf mass per unit area(LMA), and the S. superba and C. chinensis trees had greater values of wood density(WD),relative stem water content(RWC), and ratio of sapwood area to leaf area(Hv) at the 360-m elevation than at 70-m elevation. The mean canopy stomatal conductance was greater and more sensitive to vapor deficit pressure at360 m than at 70 m for both S. superba and C. chinensis, while stomatal sensitivity did not differ between the two contrasting elevations for P. massoniana. The midday leaf water potential(ψL) in P. massoniana was significantly more negative at 360 m than at 70 m, but did not vary with increasing elevation in both S. superba and C. chinensis.Variations in Hvcan be related to the differential stomatal behaviors between the two elevations. The variations of stomatal behavior and ψLwith elevation suggested the isohydric strategy for the two broad-leaved species and the anisohydric strategy for the conifer species. The species-specific differences in LMA, WD, RWC, and Hvbetween the two elevations may reflect conservative resource use strategies at the higher elevation. Our findings revealed a close relationship between hydraulic and stomatal behavior and may help better understand the functional responses of forests to changing environmental conditions.

Primary membranous nephrotic syndrome with chylothorax as first presentation:A case report and literature review

BACKGROUND Primary membranous nephrotic syndrome with chylothorax as the first manifestation is an unusual condition.To date,only a few cases have been reported in clinical practice.CASE SUMMARY The clinical data of a 48-year-old man with primary nephrotic syndrome combined with chylothorax admitted to the Department of Respiratory and Critical Care Medicine of Shaanxi Provincial People's Hospital were retrospec-tively analysed.The patient was admitted to the hospital for 12 d due to shortness of breath.Imaging showed pleural effusion,laboratory tests confirmed true chylothorax,and renal biopsy revealed membranous nephropathy.After primary disease treatment and early active symptom treatment,the prognosis of the patient was good.This case suggests that chylothorax is a rare complication of primary membranous nephrotic syndrome in adults,and early lymphan-giography and renal biopsy can assist in the diagnosis when there are no contrain-dications.CONCLUSION Primary membranous nephrotic syndrome combined with chylothorax is rare in clinical practice.We report a relevant case to provide case information for clinicians and to improve diagnosis and treatment.

COVID-19 in gastroenterology and hepatology:Lessons learned and questions to be answered

BACKGROUND Although coronavirus disease 2019(COVID-19)presents primarily as a lower respiratory tract infection,increasing data suggests multiorgan,including the gastrointestinal(GI)tract and liver,involvement in patients who are infected by severe acute respiratory syndrome coronavirus 2(SARS-CoV-2).AIM To provide a comprehensive overview of COVID-19 in gastroenterology and hepatology.METHODS Relevant studies on COVID-19 related to the study aim were undertaken through a literature search to synthesize the extracted data.RESULTS We found that digestive symptoms and liver injury are not uncommon in patients with COVID-19 and varies in different individuals.The most common GI symptoms reported are diarrhea,nausea,vomiting,and abdominal discomfort.Other atypical GI symptoms,such as loss of smell and taste and GI bleeding,have also been reported along with the evolvement of COVID-19.Liver chemistry abnormalities mainly include elevation of aspartate transferase,alanine transferase,and total bilirubin.It is postulated to be related to the binding of severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)virus to the angiotensin converting enzyme-2 receptor located on several different human cells.CONCLUSION Standardized criteria should be established for diagnosis and grading of the severity of GI symptoms in COVID-19 patients.Gastroenterology and hepatology in special populations,such as children and elderly,should be the focus of further research.Future long-term data regarding GI symptoms should not be overlooked.

Precision Medicine in Cardiovascular Diseases

Since President Obama announced the Precision Medicine Initiative in the United States,more and more attention has been paid to precision medicine.However,clinicians have already used it to treat conditions such as cancer.Many cardiovascular diseases have a familial presentation,and genetic variants are associated with the prevention,diagnosis,and treatment of cardiovascular diseases,which are the basis for providing precise care to patients with cardiovascular diseases.Large-scale cohorts and multiomics are critical components of precision medicine.Here we summarize the application of precision medicine to cardiovascular diseases based on cohort and omic studies,and hope to elicit discussion about future health care.

Degree of Humification in Fresh Litter from a Subtropical Mixed Plantation Forest in Southwest China

The humification degree of fresh litter directly controls the accumulation of soil humus derived from plant litter,but very little information on this process is available.Planted forests are well known to restrict soil fertility,which is often indicated by the soil humus level.In this study,fresh litter was collected during different plant phenological stages during 2016 and 2017 in a mixed plantation in Southwest China.The values of hue coefficientΔlogK(absorbance ratio of 400 nm and 600 nm on a logarithmic scale),optical density E4/E6(absorbance ratio of 400 nm and 600 nm)and A600/C(absorbance at 600 mm per mg of carbon per ml of extraction)and the concentration of extractable humus carbon(HC)were determined in four litter components(foliar,twigs,reproductive organs and miscellaneous)of the dominant species(Pterocarya stenoptera,Quercus acutissima,Cunninghamia lanceolata and Toxicodendron vernicifluum).All of the litter components exhibited obvious humification characteristics,and showed the highest concentration of extractable HC during the leaf maturation period.The miscellaneous and foliar litters showed greater humification than the other litter types.The components of Pterocarya stenoptera litter exhibited greater degrees of humification than those of the other species,with lowerΔlogK and E4/E6 values and higher A600/C values.The litter from coniferous and evergreen species showed lower humification than that from broad-leaf and deciduous species regardless of the litter component examined.The present results provide new insights into the management of plantations and theoretical data to accurately improve the quality of plantations and maintain soil fertility under a global change.

Identification and characterization of Fe_(3)O_(4)/peroxodisulfate advanced oxidation products from sulfameter

Sulfonamides(SAs)are one of the most widely used antibiotics and their residuals in the environment could cause some negative environmental issues.Advanced oxidation such as Fenton-like reaction has been widely applied in the treatment of SAs polluted water.Degradation rates of 95%-99.7%were achieved in this work for the tested 8 SAs,including sulfisomidine,sulfameter(SME),phthalylsulfathiazole,sulfamethoxypyridazine,sulfamonomethoxine,sulfisoxazole,sulfachloropyridazine,and sulfadimethoxine,in the Fe_(3)O_(4)/peroxodisulfate(PDS)oxidation system after the optimization of PDS concentration and p H.Meanwhile,it was found that a lot of unknown oxidation products were formed,which brought up the uncertainty of health risks to the environment,and the identification of these unknown products was critical.Therefore,SME was selected as the model compound,from which the oxidation products were never elucidated,to identify these intermediates/products.With liquid chromatography-high resolution tandem mass spectrometry(LC-HRMS/MS),10 new products were identified,in which 2-amino-5-methoxypyrimidine(AMP)was confirmed by its standard.The investigation of the oxidation process of SME indicated that most of the products were not stable and the degradation pathways were very complicated as multiple reactions,such as oxidation of the amino group,SO_(2)extrusion,and potential cross-reaction occurred simultaneously.Though most of the products were not verified due to the lack of standards,our results could be helpful in the evaluation of the treatment performance of SAs containing wastewater.

环辛二烯氘代、开环易位聚合及其聚合物的固相催化加成

氘(氚)代聚合物是一类很有前景的惯性约束聚变靶材料.为制备具有较多加氚位点的氘代聚合物,开展了环辛二烯的氘代及开环易位聚合实验研究.对1,5-环辛二烯反应过程中间产物组分进行分析,研究了其氘代反应机理.通过核磁共振波谱(1H-NMR、2H-NMR、13C-NMR)分析,表明环辛二烯氘代后的副产物为氘代环辛烯.研究了温度、添加剂、反应时间对产物氘代率及副产物生成率的影响,获得了优化的反应条件,并制备了氘代率高达96%的氘代1,3-环辛二烯.开展了(氘代)1,3-环辛二烯的开环易位聚合实验,其中大量连续共轭双键的存在导致聚合物结晶使得其溶解性较差.在5 wt%的Pd/BaSO4与Grubbs二代催化剂的存在下,开展了聚1,3-环辛二烯、氘代1,3-环辛二烯与氘代环辛烯共聚物的固相催化加氘实验,均可加氘至接近饱和,在此过程中伴随着明显的氢同位素交换反应.发展了一种均相固相催化氢同位素加成的方法,有望实现在已成型的氘代聚合物靶丸上直接加氚,从而制备氘-氚代聚合物靶丸.

Distributed power conditioning unit of large-scale space solar power station

In this paper,a multi-bus distributed Power Conditioning Unit(PCU)is proposed for the Space Solar Power Station with large scale photovoltaic(PV)array and power levels reaching MW level.In this unit,there are multiple independent PV arrays.In each PV array,there are multiple independent PV subarrays.In this paper,a V-P droop control method with adaptive droop coefficient is proposed,which modifies the droop intercept based on the bus voltage deviation and the power per unit value of the PV array.This method ensures the accuracy of bus voltage and achieves proportional distribution of power between PV arrays based on the proposed topology structure in this paper.When the load changes or the output power of the PV array fluctuates,this method can ensure that power is distributed proportionally.The principle and control method of the proposed droop control method is analyzed in this paper.The effectiveness of the method is verified through MATLAB/Simulink simulation and experiment.Simulation and experimental results show that the proposed method can achieve power distributed proportionally when load changes and PV output power fluctuates,reduce bus voltage error caused by line impedance and differences in rated power of different PV arrays,and improve the performance of PV power generation system applied to space.

Cathodic corrosion as a facile and universal method for scalable preparation of powdery single atom electrocatalysts

Top-down strategy has been widely applied for synthesis of metal single atom catalysts(SACs)via converting metal nanoparticles or bulk metals into atomically dispersed species.Here,we report a simple electrochemical atomic migration strategy for top-down synthesis of SACs via a facile cathodic corrosion process without involving high temperature or harsh atmosphere.Atoms of metal nanoparticles on cathode are firstly disbanded under high negative voltage,and emitted into the electrolyte in the form of atomic metal anions in Zintl phase.The escaped atomically dispersed metal species are then oxidized by water molecules and captured by the defects on the pre-added nitrogen doped carbon carriers in the electrolyte.This cathodic corrosion strategy is confirmed to be suitable for scalable synthesis of kinds of metal SACs(e.g.,Pt,Pd,and Ir)on doped carbon materials.Typically,the as-prepared nitrogen doped carbon powder supported Pt SACs exhibit superior catalytic activity toward hydrogen evolution reaction(HER)with a low overpotential of 0.024 V at 10 mA·cm^(−2)and a low Tafel slope of 29.7 mV·dec^(−1)as well as a long-term durability.