Microstructural characteristics and mechanical properties of bobbin-tool friction stir welded 2024–T3 aluminum alloy

Cold-rolled 2024-T3 sheet alloy was subjected to bobbin-tool friction stir welding （BTFSW）. The microstructural characteristics and mechanical properties of the nugget zone in the as-welded state were investigated. The results show that the equiaxed grain size of BTFSW 2024-T3 alloy decreases from 7.6 to 2.8 μm as the welding speed is increased from 80 to 120 mm/min; in addition, fine grains are generated in the nugget zone and the size distribution is non-uniform. All A12CuMg （S＇） precipitates dissolve into the A1 matrix, whereas Mn-rich phases confirmed as T phases （Al20CuEMn3, A16Mn, or AlaMn） remain unchanged. The optimized parameters for BTFSW are veri- fied as the rotation speed of 350 r/min and the travel speed of 100 mm/min. The variations in precipitation and dislocation play more impor- tant roles than grain size in the nugget zone with respect to influencing the mechanical properties during the BTFSW process. After the BTFSW process, the fracture mode of base material 2024-T3 alloy transforms from ductile rupture to ductile-brittle mixed fi＇acture.

Synaptotagmins family affect glucose transport in retinal pigment epithelial cells through their ubiquitination-mediated degradation and glucose transporter-1 regulation

BACKGROUND Synaptotagmins(SYTs)are a family of 17 membrane transporters that function as calcium ion sensors during the release of Ca2+-dependent neurotransmitters and hormones.However,few studies have reported whether members of the SYT family play a role in glucose uptake in diabetic retinopathy(DR)through Ca2+/glucose transporter-1(GLUT1)and the possible regulatory mechanism of SYTs.AIM To elucidate the role of the SYT family in the regulation of glucose transport in retinal pigment epithelial cells and explore its potential as a therapeutic target for the clinical management of DR.METHODS DR was induced by streptozotocin in C57BL/6J mice and by high glucose medium in human retinal pigment epithelial cells(ARPE-19).Bioinformatics analysis,reverse transcriptase-polymerase chain reaction,Western blot,flow cytometry,ELISA,HE staining,and TUNEL staining were used for analysis.RESULTS Six differentially expressed proteins(SYT2,SYT3,SYT4,SYT7,SYT11,and SYT13)were found between the DR and control groups,and SYT4 was highly expressed.Hyperglycemia induces SYT4 overexpression,manipulates Ca2+influx to induce GLUT1 fusion with the plasma membrane,promotes abnormal expression of the glucose transporter GLUT1 and excessive glucose uptake,induces ARPE-19 cell apoptosis,and promotes DR progression.Parkin deficiency inhibits the proteasomal degradation of SYT4 in DR,resulting in SYT4 accumulation and enhanced GLUT1 fusion with the plasma membrane,and these effects were blocked by oe-Parkin treatment.Moreover,dysregulation of the myelin transcription factor 1(Myt1)-induced transcription of SYT4 in DR further activated the SYT4-mediated stimulus-secretion coupling process,and this process was inhibited in the oe-MYT1-treated group.CONCLUSION Our study reveals the key role of SYT4 in regulating glucose transport in retinal pigment epithelial cells during the pathogenesis of DR and the underlying mechanism and suggests potential therapeutic targets for clinical DR.

Investigation on influencing factors of wheel polygonization of a plateau high-speed EMU train

Purpose–This study aims to investigate the cause of high-order wheel polygonization in a plateau high-speed electric multiple unit(EMU)train.Design/methodology/approach–A series of field tests were conducted to measure the vibration accelerations of the axle box and bogie when the wheels of the EMU train passed through tracks with normal rail roughness after re-profiling.Additionally,the dynamic characteristics of the track,wheelset and bogie were also measured.These measurements provided insights into the mechanisms that lead to wheel polygonization.Findings–The results of the field tests indicate that wheel polygonal wear in theEMUtrain primarily exhibits 14–16 and 25–27 harmonic orders.The passing frequencies of wheel polygonization were approximately 283–323 Hz and 505–545 Hz,which closely match the dominated frequencies of axle box and bogie vibrations.These findings suggest that the fixed-frequency vibrations originate from the natural modes of the wheelset and bogie,which can be excited by wheel/rail irregularities.Originality/value–The study provides novel insights into the mechanisms of high-order wheel polygonization in plateau high-speed EMU trains.Futher,the results indicate that operating the EMU train on mixed lines at variable speeds could potentially mitigate high-order polygonal wear,providing practical value for improving the safety,performance and maintenance efficiency of high-speed EMU trains.

In vitro differentiation of adipose-derived stem cells and bone marrow-derived stromal stem cells into neuronal-like cells

Adipose-derived stem cells and bone marrow-derived stromal stem cells were co-cultured with untreated or Aβ1-40-treated PC12 cells, or grown in supernatant derived from untreated or Aβ1-40-treated PC12 cells. Analysis by western blot and quantitative real-time PCR showed that protein levels of Nanog, Oct4, and Sox2, and mRNA levels of miR/125a/3p were decreased, while expression of insulin-like growth factor-2 and neuron specific enolase was increased. In comparison the generation of neuron specific enolase-positive cells was most successful when adipose-derived stem cells were co-cultured with Aβ1-40-treated PC12 cells. Our results demonstrate that adipose-derived stem cells and bone marrow-derived stromal stem cells exhibit trends of neuronal-like cell differentiation after co-culture with Aβ1-40-treated PC12 cells. This process may relate to a downregulation of miR-125a-3p mRNA expression and increased levels of insulin-like growth factor-2 expression.

Characteristics of Vibration and Sound Radiation of Metro Resilient Wheel

Resilient wheels are extensively used in urban rail transit, especially for tramway systems, owing to its advantages in noise reduction. A new type of resilient wheel for a metro is designed, and its characteristics of vibration and sound radiation, including the rolling noise of a resilient single wheel coupled with a track, are studied in this paper. A two-step research is presented. Firstly, laboratory experiments were conducted to obtain the vibration response of the designed resilient wheel under the radial excitation on its tread. Secondly, the rolling noise model of the resilient wheel coupled with a slab track used in a metro line is developed. The wheel model is based on the 3 D finite elementand boundary element methods and verified by using the experimental results obtained from the laboratory. The track vibration model is based on the wavenumber finite element method, and the track sound radiation is calculatedby using an e cient frequency-domain Rayleigh method. The interaction of the resilient wheel and the slab track is analyzed considering the measured wheel/rail roughness of the metro. The contribution of the resilient wheel to the reduction of wheel/rail system noise is analyzed. The results show that the resilient wheel can e ectively reduce the wheel/rail rolling noise by approximately 2 dB(A) to 3 dB(A), mainly because the radiated noise by the rail is reduced. In addition, the elastic modulus of the rubber has an important influence on the noise reduction of resilient wheels.

A FEM-DFN model for the interaction and propagation of multi-cluster fractures during variable fluid-viscosity injection in layered shale oil reservoir

To investigate the height growth of multi-cluster fractures during variable fluid-viscosity fracturing in a layered shale oil reservoir,a two-dimensional finite element method(FEM)-discrete fracture network(DFN)model coupled with flow,stress and damage is proposed.A traction-separation law is used to describe the mixed-mode response of the damaged adhesive fractures,and the cubic law is used to describe the fluid flow within the fractures.The rock deformation is controlled by the in-situ stress,fracture cohesion and fluid pressure on the hydraulic fracture surface.The coupled finite element equations are solved by the explicit time difference method.The effects of the fracturing treatment parameters including fluid viscosity,pumping rate and cluster spacing on the geometries of multifractures are investigated.The results show that variable fluid-viscosity injection can improve the complexity of the fracture network and height of the main fractures simultaneously.The pumping rate of15 m^(3)/min,variable fluid-viscosity of 3-9-21-36-45 mPa s with a cluster spacing of 7.5 m is the ideal treatment strategy.The field application shows that the peak daily production of the application well with the optimized injection procedu re of variable fluid-viscosity fracturing is 171 tons(about 2.85 times that of the adjacent well),which is the highest daily production record of a single shale oil well in China,marking a strategic breakthrough of commercial shale oil production in the Jiyang Depression,Shengli Oilfield.The variable fluid-viscosity fracturing technique is proved to be very effective for improving shale oil production.

Tailoring the mercaptan ligands for high performance inverted perovskite solar cells with efficiency exceeding 21%

Interface passivation engineering has been recognized as an effective way to simultaneously contribute to the optoelectronic characteristic and stability of perovskite solar cells(PSCs). Herein, a p-conjugated dual-ligand 1,4-phenylmercaptan(PHMT) is explored to rationally tailor the surface of perovskite film.The experimental and theoretical results show that the PHMT presents planar structure and obvious electron delocalization characteristics, which allow it to anchor on the surface of perovskite with a certain orientation, thereby promoting the transport of interface charge. Moreover, the two sulfhydryl groups in PHMT reduce the trap density of the perovskite film by passivating under-coordinated lead ions.Consequently, the PHMT-modified inverted device based on MAPbI_(3)(MA: methylammonium) achieves enhanced efficiency from 18.11%(control) to 21.11%, along with the ambient stability up to 3500 h.After being placed at 85 °C for 500 h or illuminated for 600 h, the modified device remains over 89%or 86% of initial efficiency. This discovery opens a new window for the choice of passivators to improve the performance of PSCs.

Neuronal differentiation of adipose-derived stem cells and their transplantation for cerebral ischemia

OBJECTIVE： To review published data on the biological characteristics, differentiation and applications of adipose-derived stem cells in ischemic diseases. DATA RETRIEVAL： A computer-based online search of reports published from January 2005 to June 2012 related to the development of adipose-derived stem cells and their transplantation for treatment of cerebral ischemia was performed in Web of Science using the key words ＂adipose-derived stem cells＂, ＂neural-like cells＂, ＂transplantation＂, ＂stroke＂, and ＂cerebral ischemia＂. SELECTION CRITERIA： The documents associated with the development of adipose-derived stem cells and their transplantation for treatment of cerebral ischemia were selected, and those published in the last 3-5 years or in authoritative journals were preferred in the same field. Totally 89 articles were obtained in the initial retrieval, of which 53 were chosen based on the inclusion criteria. MAIN OUTCOME MEASURES： Biological characteristics and induced differentiation of adipose-derived stem cells and cell transplantation for disease treatment as well as the underlying mechanism of clinical application. RESULTS： The advantages of adipose-derived stem cells include their ease of procurement, wide availability, rapid expansion, low tumorigenesis, low immunogenicity, and absence of ethical constraints. Preclinical experiments have demonstrated that transplanted adipose-derived stem cells can improve neurological functions, reduce small regions of cerebral infarction, promote angiogenesis, and express neuron-specific markers. The improvement of neurological functions was demonstrated in experiments using different methods and time courses of adipose-derived stem cell transplantation, but the mechanisms remain unclear. CONCLUSION： Further research into the treatment of ischemic disease by adipose-derived stem cell transplantation is needed to determine their mechanism of action.

Subway Embedded Track Geometric Irregularity Safety Limits

A coupling dynamic model of a subway train and an embedded track is established to study the safety limits of track irregularities.The simulated vehicle system was a 74-degrees of freedom multi-rigid body model,and the rail was a Timoshenko beam.The slab was a three-dimensional solid finite element model.The sensitive wavelength irregularity was first studied,and then the safety limit of the sensitive wavelength was analyzed.The wheel-rail lateral force exhibited a substantial effect on the track alignment and gauge irregularity safety limit.The wheel-rail vertical force and the rate of wheel load reduction significantly affected the height and cross-level irregularity safety limit.The results demonstrate that the safety limits of the alignment,gauge,height,and cross-level embedded track geometric irregularity are 5.3 mm,[−10.5,8]mm,5.6 mm,and 6 mm,respectively.

Redox history of the Three Gorges region during the Ediacaran and Early Cambrian as indicated by the Fe isotope

The Ediacaran-Cambrian transition is characterized by numerous events such as the emergence of large multi-cellular metazoans and surface environmental disturbances.Based on geological evidence,it has been proposed that this transition coincided with the increase in the atmospheric oxygen level that was key to the evolution of life.Even though ancient redox conditions can be inferred from the composition of sedimentary iron mineral species,this method is not necessarily applicable to all rocks.In the Earth system,the cycling of iron is of considerable interest owing to its sensitivity to redox conditions.Information regarding the paleo-oceanic iron cycle is revealed in the iron isotopic composition of ironbearing minerals.Unfortunately,only limited iron isotopic data exists for Ediacaran-to Cambrianperiod oceans.To circumvent this deficiency,we drilled a fossiliferous Ediacaran to Early Cambrian sedimentary succession in the Three Gorges region,South China.We analyzed the iron isotope ratios(δ^(56/54)Fe)of pyrite grains in the drill cores using laser ablation multi collector inductively coupled plasma mass spectrometry.The results demonstrate large variations inδ^(56/54)Fe,from-1.6 to 1.6‰,and positive iron isotope ratios are observed in many successions.The presence of positiveδ^(56/54)Fe in pyrite indicates that the ferrous iron in the seawater was partially oxidized,suggesting that seawater at Three Gorges was ferruginous during the Ediacaran and Early Cambrian periods.However,aggregated pyrite grains in organic carbon-rich black shales at Member 4 of the Doushantuo Formation and the base of the Shuijingtuo Formation yield near-zeroδ^(56/54)Fe values;this suggests that the ocean was transiently dominated by sulfidic conditions during these periods.Notably negativeδ^(56/54)Fe values,lower than-1‰,can be interpreted as a signature of DIR.The DIR also might contribute in part to the re-mineralization of organic matter during the largest negative carbon isotope anomaly in the Ediacaran.

Citron C-05 inhibits both the penetration and colonization of Xanthomonas citri subsp.citri to achieve resistance to citrus canker disease

Citrus canker,caused by Xanthomonas citri subsp.citri(Xcc),is a serious bacterial disease that affects citrus production worldwide.Citron C-05(Citrus medica)is the only germplasm in the Citrus genus that has been identified to exhibit strong resistance to Xcc.However,it has not been determined when,where,and how Xcc is restricted in the tissues of Citron C-05 during the infection process.In the present study,we investigated the spatiotemporal growth dynamics of an eGFP-labeled virulent Xcc(eGFP-Xcc)strain in Citron C-05 along with five susceptible biotypes(i.e.,lemon,pummelo,sour orange,sweet orange,and ponkan mandarin)upon inoculation via the spraying or leaf infiltration of a bacterial suspension.The results from extensive confocal laser scanning microscopy analyses showed that while Xcc grew rapidly in plants of all five susceptible genotypes,Xcc was severely restricted in the epidermal and mesophyll cell layers of the leaves of Citron C-05 in the early stage of infection.Not surprisingly,resistance against Xcc in Citron C-05 was found to be associated with the production of reactive oxygen species and hypersensitive response-like cell death,as well as greater upregulation of several defense-related genes,including a pathogenesis-related gene(PR1)and a glutathione S-transferase gene(GST1),compared with sweet orange as a susceptible control.Taken together,our results not only provide further valuable details of the spatiotemporal dynamics of the host entry,propagation,and spread of Xcc in both resistant and susceptible citrus plants but also suggest that resistance to Xcc in Citron C-05 may be attributed to the activation of multiple defense mechanisms.

Study of electrospray ionization tandem mass spectrometry of the benzofuranone compounds

A detailed analysis of benzofuranone compounds under multiple tandem mass spectrometry （ESI-MS^n） conditions is reported. Element composition data of the fragment ions were obtained with the aid of comparison of the multiple tandem mass spectra of four compounds, and the structures of which are identical except for some substituted groups or epimers or cis-trans-isomers. Attempts have been made to provide rational pathways for the formation of the fragment ions from these protonated compounds. And the structure-fragmentation relationships will facilitate the characterization of the structures of other analogs.

广州市白云区2010—2017年5岁以下儿童死亡监测结果分析

目的分析广州市白云区2010-2017年5岁以下儿童死亡原因与变化趋势。方法选取2009年10月1日至2017年9月30日间8个统计年度广州市白云区5岁以下儿童死亡个案,回顾性分析5岁以下儿童死亡水平与变化趋势、主要死因及顺位、主要病种死因别死亡率。结果广州市白云区2010-2017年活产儿总计82 797例,监测5岁以下儿童死亡总数341例,死亡率为4. 12‰,2010-2017年5岁以下儿童死亡率整体呈下降趋势(P <0. 05)。2010-2017年,白云区5岁以下儿童死因顺位前5位依次为早产儿、先天性心脏病、感染性疾病、伤害、肿瘤,占全部5岁以下儿童死亡的70. 09%(239/341)。2010-2017年,白云区5岁以下儿童主要死因中先天性心脏病、伤害死亡率呈下降趋势(均P <0. 05),早产儿、感染性疾病和肿瘤死亡率无明显变化趋势(均P> 0. 05)。结论 2010-2017年,广州市白云区5岁以下儿童死亡率整体呈下降趋势,死因主要是早产儿、先天性心脏病、感染性疾病、伤害与肿瘤。

Transfer Path Contribution to Floor Vibration of Metro Vehicles Based on Operational Transfer Path Analysis Method

Operational transfer path analysis(OTPA)is an advanced vibration and noise transfer path identification and contribution evaluation method.However,the application of OTPA to rail transit vehicles considers only the excitation amplitude and ignores the influence of the excitation phase.This study considers the influence of the excitation amplitude and phase,and analyzes the contribution of the secondary suspension path to the floor vibration when the metro vehicle runs at 60 km/h,using an analysis based on the OTPA method.The results show that the vertical direction of the anti-rolling torsion bar area provides the maximum contribution to the floor vibration,with a contribution of 22.1%,followed by the longitudinal vibration of the air spring area,with a contribution of 17.1%.Based on the contribution analysis,a transfer path optimization scheme is proposed,which may provide a reference for the optimization of the transfer path of metro vehicles in the future.

固相萃取技术在水果氨基酸分析前处理中的应用——一个仪器分析综合实验

为提高学生的理论水平和实践能力,设计了针对欧李果实氨基酸测定的仪器分析综合实验。引入样品分析前处理环节,构建完整的仪器分析过程。通过氨基酸提取方法比较及固相萃取技术在氨基酸净化过程的方法探索,有效促进学生理论知识和实践能力的融合,在解决实际问题的过程中提升学生的科学素养及综合思维能力。

广州市白云区基层医疗机构儿童保健人力资源配置状况分析

目的了解广州市白云区基层医疗机构儿童保健人力资源配置情况。方法以白云区基层医疗机构为调查对象,调查机构一般情况及儿保医生基本情况,分析区域机构与儿童保健人员配置状况,并用Lorenz曲线和Gini系数评价配置的公平性。结果按服务人口测算,每11.1万名常住人口设置一所基层医疗机构,每万名常住人口拥有0.26名儿童保健医生,基层医疗机构及儿童保健医生人力资源配置的Gini系数分别为0.1603、0.1598;按照管理面积测算,每36.2平方公里设置一所基层医疗机构,每平方公里配备0.08名儿童保健医生,基层医疗机构及儿童保健医生人力资源配置的Gini系数分别为0.6034、0.6567。按照管理面积测算的Gini系数处于公平性配置危险状态。结论白云区基层医疗机构布局不合理,基层医疗机构儿童保健医生人力资源总量严重不足,数量和公平性急需改善。

武汉军山长江大桥ERE钢桥面铺装技术应用

为了解决现有双层SMA钢桥面铺装出现的病害,武汉军山长江大桥钢桥面铺装大修采用了由我国自主研发的树脂沥青组合体系(ERE)技术,目前该技术的应用研究及成熟经验较少。基于此,依托武汉军山长江大桥,从技术特点、混合料配合比设计及性能和质量控制标准等方面对ERE铺装结构进行研究。

Optimization of decoupling combustion characteristics of coal briquettes and biomass pellets in household stoves

Burning coal briquettes or biomass pellets in household decoupling stoves is of significance to the reduction of residential pollutant emissions such as NO and CO. In order to make full use of the superiority of decoupling combustion technology, the household stoves should be specially designed and optimized to adapt to fuel types and combustion characteristics. Using numerical simulation and experimental validation, this study quantitatively clarified that the reducibility of devolatilization char plays an important role in the suppression of NO emission in the decoupling combustion of coal, while the reducibility of pyrolysis gases has a dominant effect on the reduction of NO in the decoupling combustion of biomass. An optimal parameter combination of throat height and grate angle was obtained for the simultaneous suppression of NO and CO emissions in the household decoupling stove burning coal briquettes. Two types of decoupling stoves were developed to enable the clean combustion of biomass pellets. The A-type biomass stove with a multi-pass smoke tunnel shows a better comprehensive NO and CO reduction effectiveness than the B-type biomass stove consisting of a two-stage grate structure and an S-shaped pyrolysis chamber. The optimal structural parameters provided references for the design and manufacture of commercial decoupling coal and biomass stoves.

A high-resolution chemostratigraphy of post-Marinoan Cap Carbonate using drill core samples in the Three Gorges area, South China

Cap Carbonates overlie the Marinoan Snowball Earth-related glacial diamictite, and possibly record the drastic surface environmental change and biological evolution after the Snowball Earth. We conducted on-land drilling from the Liantuo Formation, through the Nantuo, to the lower Doushantuo Formation in the Three Gorges area of South China to collect fresh, continuous samples in the Three Gorges area. We obtained high-resolution chemostratigraphies of ~13C and 6180 values of carbonates from the topmost part of the Nantuo Formation to the Cap Carbonate, in order to decode the detailed surface environmental change in the shallow marine setting. The δ3C chemostratigraphy possesses some unique characteristics： （1） stable δ13C values as a whole, but ubiquitous low δ13C anomalies through the Cap Carbonate, （2） increase of the δ13C values from -3 to ＋5‰ across the C2/C3 boundary, （3） no δ13C anomaly between the CI and C2 boundary, and （4） presence of an anomalous high δ13C value （＋2.3%0） and a faint positive correlation between δ13C and δ18O values in the C1 unit. Evidence of quite low δ13C anomalies （with a nadir of -41‰）, ubiquitous negative δ13C anomalies through the Cap Carbonate, and a high 613C anomaly accompanied with a faint positive correlation between δ13C and δ18O values in the C1 unit supports decomposition and formation of methane hydrate during Cap Carbonate formation. The drastic increase of δ13C values from the upper C2 to C3 units in- dicates enhancement of primary productivity and organic carbon burial, possibly due to high continental fluxes after the Snowball Earth event, evidenced by high Sr isotope values. The increase is restricted to the proximal side of the inner shelf in South China, and the timing of the increase of δ13C values of carbonates is earlier at Three Gorges area than any other area, suggesting that the enhancement of primary productivity started in the proximal environment because of higher continental influxes. The increase in oxygen contents of seawater due to the enhanced primary productivity possibly resulted in the emergence of multicellular animals soon after Cap Carbonate deposition.

Rail Roughness Acceptance Criterion Based on Metro Interior Noise

Severe rail roughness leads to a series of problems in metro systems,particularly the vehicle noise problem.To ensure a better acoustic environment,rail roughness control is therefore one of the main concerns for the metro operators.But the existing roughness acceptance criteria are not suitable for metro interior noise control.It is an appropriate method to determine the rail roughness limit based on interior noise.A rail roughness acceptance criterion based on metro interior noise is accordingly proposed in this paper.The relationship between rail roughness and interior noise can be derived with wheel-rail noise as link.With this objective,a combined test and simulation method is adopted.A validated wheel-rfigil noise prediction model is thus established to determine the relationship between rail roughness and wheel-rail noise.Moreover,the transfer function of wheel-rail noise to interior noise is developed based on extensive field test.Using this method,the noise sensitivity to roughness wavelength and acceptance criteria at different speeds and track structures are investigated.Finally,an eclectic rail corrugation acceptance criterion on curved track is suggested in consideration of practical application.