Electroluminodynamic therapy for the treatment of drug-resistant pathogen infection

The administration of antibiotics has been the primary strategy for combating bacterial infections[1,2].However,the widespread and excessive use of antibiotics has resulted in the alarming rise of bacterial resistance,posing a significant threat to human health[3–5].Therefore,it is imperative to exploit innovative treatment strategy.

Ambiently fostering solid electrolyte interphase for low-temperature lithium metal batteries

Despite being a leading candidate to meet stringent energy targets,lithium(Li) metal batteries(LMBs)face severe challenges at low temperatures such as dramatic increase in impedance,capacity loss and dendrite growth.Unambiguously fingerprinting rate-limited factors of low-temperature LMBs would encourage targeted approaches to promote performances.Herein,the charge transfer impedance across solid electrolyte interphase(SEI) is identified to restrict battery operation under low temperature,and we propose a facile approach on the basis of ambiently fostering SEI(af-SEI) to facilitate charge transfer.The concept of af-SEI stems from kinetic benefits and structural merits to construct SEI at ambient temperature over low temperature developed SEI that is temporally consuming to achieve steady state and that is structurally defective to incur dendrite growth.The af-SEI allows ionically conductive and morphologically uniform layer on the anode surface,which exhibits a lower resistance and induces an even deposition of Li in the subsequent low temperature battery operation.Armed with af-SEI,the LMBs deliver the improved rate performance and prolonged cycle life when subjected to low temperature cycling.This work unveils the underlying causes that limit low temperature LMB performances,and enlightens the facile test protocols to build up favorable SEI,beyond scope of material and morphology design.

Correlation between growth differentiation factor-15 and collagen metabolism indicators in patients with myocardial infarction and heart failure

BackgroundGrowth differentiation factor （GDF）-15, a divergent member of the transforming growth factor beta super-family does appear to be up-regulated in response to experimental pressure overload and progression of heart failure （HF）. HF frequently develops after myocardial infarction （MI）, contributing to worse outcome. The aim of this study is to assess the correlation between GDF-15 levels and markers related to collagen turnover in different stages of HF.MethodsThe study consists of a cohort of 179 patients, including stable angina pectoris patients （AP group,n= 50）, old MI patients without HF （OMI group,n = 56）, old MI patients with HF （OMI-HF group,n= 38） and normal Control group （n = 35）. Both indicators reflecting the synthesis and degradation rates of collagen including precollagen I N-terminal peptide （PINP）, type I collagen carboxy-terminal peptide （ICTP）, precollagen III N-terminal peptide （PIIINP） and GDF-15 were measured using an enzyme-linked inmunosorbent assay.ResultsThe plasma GDF-15 level was higher in OMI-HF group （1373.4 ± 275.4 ng/L） than OMI group （1036.1 ± 248.6 ng/L）, AP group （784.6 ± 222.4 ng/L） and Control group （483.8 ± 186.4 ng/L） （P〈 0.001）. The indi-cators of collagen turnover （ICTP, PINP, PIIINP） all increased in the OMI-HF group compared with Control group （3.03 ± 1.02μg/Lvs. 2.08 ± 0.95μg/L, 22.2 ± 6.6μg/Lvs. 16.7 ± 5.1μg/L and 13.2 ± 7.9μg/Lvs. 6.4 ± 2.1μg/L, respectively;P〈 0.01）. GDF-15 positively cor-related with ICTP and PIIINP （r = 0.302,P〈 0.001 andr= 0.206,P= 0.006, respectively）. GDF-15 positively correlated to the echocardio-graphic diastolic indicators E/Em and left atrial pressure （r= 0.349 and r= 0.358, respectively;P〈 0.01）, and inversely correlated to the systolic indicators left ventricular ejection fraction and the average of peak systolic myocardial velocities （Sm） （r=-0.623 and r=-0.365, respectively;P〈 0.01）.ConclusionPlasma GDF-15 is associated with the indicators of type I and III collagen turnover.

Numerical simulation of flow separation over a backward-facing step with high Reynolds number

Large eddy simulation (LES) explicitly calculates the large-scale vortex field and parameterizes the small-scale vortices.In this study,LES and κ-ε models were developed for a specific geometrical configuration of backward-facing step (BFS).The simulation results were validated with particle image velocimetry (PIV) measurements and direct numerical simulation (DNS).This LES simulation was carried out with a Reynolds number of 9000 in a pressurized water tunnel with an expansion ratio of 2.00.The results indicate that the LES model can reveal largescale vortex motion although with a larger grid-cell size.However,the LES model tends to overestimate the top wall separation and the Reynolds stress components for the BFS flow simulation without a sufficiently fine grid.Overall,LES is a potential tool for simulating separated flow controlled by large-scale vortices.

Altered serum level of cartilage oligomeric matrix protein and its association with coronary calcification in patients with coronary heart disease

Background Cartilage oligomeric matrix protein （COMP） is mainly found in the skeletal system and vascular smooth muscle cells. Recent researches showed that it had a protective function on blood vessels and could also inhibit vascular calcification. We investigated the serum COMPs in coronary heart disease （CHD） patients, and the relationship between serum COMP and the calcification of coronary artery. Methods A total of 233 consecutive chest pain patients who first underwent coronary angiography followed by multi-slice computed to- mography （MSCT） within six months were recruited and divided into two groups according to the coronary angiography luminal diameter narrowing percentages： CHD group （diameter narrowing 〉 50%, n = 194） and control group （diameter narrowing 〈 50%, n = 39）. The Gen- sini score, Syntax score and coronary artery calcium score （CACs） were calculated. The serum COMP level was determined using ELISA. Results The levels of COMP were significantly higher in the CHD group than in the control group 155.7 （124.5-194.5） ng/mL vs. 128.4 （113.0-159.9） ng/mL, P = 0.019. There were no correlation between COMP, Gensini score, Syntax score, severity of coronary stenosis and the number of coronary artery with stenosis 〉 50%. The serum COMP was correlated with age （r = 0.294, P 〈 0.001）, fasting glucose （r = 0.163, P = 0.015）, HbAlc （r = 0.194, P = 0.015） and CACs （r = 0.137, P = 0.037）. Stepwise linear regression analysis showed that COMP level and age were independent predictors of CACs in the CHD patients （fl = 0.402, t = 2.612, P = 0.015; fl = 0.472, t = 3.077, P = 0.005）. Performance of COMP for predicting CHD was shown as area under curve （AUC）： 0.632, 95% CI： 0.549-0.715 and upper tertile CACs was AUC： 0.602, 95% CI： 0.5264）.678 in receiver operating characteristic （ROC） curve analysis. Conclusion Calcification of coronary artery was an independent predictor of serum COMPs.

Prognostic value of coronary artery calcium score in patients with stable an-gina pectoris after percutaneous coronary intervention

Objectives To evaluate the prognostic value of the coronary artery calcium （CAC） score in patients with stable angina pectoris （SAP） who underwent percutaneous coronary intervention （PCI）. Methods A total of 334 consecutive patients with SAP who underwent first PCI following multi-slice computer tomography （MSCT） were enrolled from our institution between January 2007 and June 2012. The CAC score was calculated according to the standard Agatston calcium scoring algorithm. Complex PCI was defined as use of high pressure bal-loon, kissing balloon and/or rotablator. Procedure-related complications included dissection, occlusion, perforation, no/slow flow and emer-gency coronary artery bypass grafting. Main adverse cardiac events （MACE） were defined as a combined end point of death, non-fatal myo-cardial infarction, target lesion revascularization and rehospitalization for cardiac ischemic events. Results Patients with a CAC score〉300 （n=145） had significantly higher PCI complexity （13.1%vs. 5.8%, P=0.017） and rate of procedure-related complications （17.2%vs. 7.4%, P=0.005） than patients with a CAC score≤300 （n=189）. After a median follow-up of 22.5 months （4-72 months）, patients with a CAC score≤300 differ greatly than those patients with CAC score＆gt;300 in cumulative non-events survival rates （88.9 vs. 79.0%, Log rank 4.577, P=0.032）. After adjusted for other factors, the risk of MACE was significantly higher [hazard ratio （HR）：4.3, 95%confidence inter-val （95%CI）：2.4-8.2, P=0.038] in patients with a CAC score〉300 compared to patients with a lower CAC score. Conclusions The CAC score is an independent predictor for MACE in SAP patients who underwent PCI and indicates complexity of PCI and proce-dure-related complications.

Association between serum cartilage oligomeric matrix protein and coronary artery calcification in maintenance hemodialysis patients

Background Coronary artery calcification(CAC)is common in end-stage renal disease(ESRD)patients,and the extent of CAC is closely related to cardiovascular outcomes in ESRD patients.Cartilage oligomeric matrix protein(COMP),as a component of the vascular matrix,has been found to be an inhibitor of arterial calcification in basic studies.However,there is no clinical research on the correlation between COMP and CAC in maintenance hemodialysis(MHD)patients.The aim of this study was to explore the relationship between serum COMP levels and CAC and cardiovascular events in MHD patients.Methods Serum COMP levels were compared between 54 MHD patients and 66 healthy people.MHD patients were then divided into three groups according to the tertiles of the concentration of COMP level and were followed up for major adverse cardiac events(MACEs),which were defined as a combined end point of new onset angina pectoris,nonfatal myocardial infarction,heart failure,coronary artery revascularization,hospitalization due to angina pectoris and all-cause deaths.The CAC score was calculated based on computed tomography scans.Results The serum COMP level in MHD patients was significantly higher than that in the general population[984.23(248.43-1902.61)ng/mL vs.219.01(97.26-821.92)ng/mL,P<0.01].Serum COMP levels were positively correlated with CAC(r=0.313,P=0.021)and serum parathyroid hormone in MHD patients(r=0.359,P<0.01).Linear regression suggested that after adjusting for age,fasting blood glucose(Glu)and glycosylated hemoglobin(HbAlc),CAC score was an independent predictor in the final model for COMP level(β=0.424,t=3.130,P<0.01).The receiver operating characteristic(ROC)curve showed that COMP≥994 mg/mL had 68.0%sensitivity and 72.4%specificity for the prediction of severe CAC[area under the curve(AUC):0.674,P=0.030,95%CI:0.526-0.882].After a median follow-up of 16 months(8-24 months),there was no difference in the incidence rate of MACEs between the upper,middle and lower serum COMP groups.Conclusions Our study found that MHD patients have higher levels of circulating COMP than controls.The serum COMP level is positively correlated with CAC score and could be used as a biomarker of severe CAC in MHD patients.However,there is no obvious correlation between serum COMP levels and the incidence of cardiovascular events.

极低、超低体重早产儿医院感染变化及其危险因素分析

目的探讨5年间极低、超低体重早产儿医院感染变化趋势及危险因素。方法选取2014年1月—2018年12月江门市中心医院新生儿重症监护室的极低、超低体重早产儿303例患儿资料进行回顾性分析,比较5年间早产儿医院感染例数率、例次率及感染疾病发病率、感染组与非感染组临床特征、病原菌和耐药菌的变化并分析其危险因素。结果5年间早产儿医院感染例数率、例次率及感染疾病发病率比较,差异无统计学意义(P>0.05)。发生医院感染的早产儿5年间临床特征比较,肠外营养(PN)时间和外周中心静脉导管(PICC)置管时间,2017年组、2018年组均比2014年组、2015年组、2016年组延长(P<0.05);生后3代头孢菌素应用率,2017年组比2014年组增多(P<0.05),2018年组比2014年组、2015年组和2016年组增多(P<0.05)。未发生医院感染的早产儿5年间临床特征比较,胎龄,2016年组比2015年组、2017年组减小(P<0.05),2018年组比2017年组减小(P<0.05);气管插管时间,2016年组比其他4年组延长(P<0.05);有创呼吸机应用率,2016年组高于2014年组、2015年组、2018年组(P<0.05);生后3代头孢菌素应用率,2016年组、2017年组、2018年组比2014年组、2015年组增多(P<0.05);脐静脉置管(UVC)率,2016年组比2014年组、2017年组、2018年组增多(P<0.05)。5年间早产儿医院感染部分病原菌仍以肺炎克雷伯杆菌及大肠埃希氏菌居多,病原菌构成比差异有统计学意义的是人葡萄球菌,2018年比前4年增多(P<0.05)。感染组与非感染组早产儿比较,性别、出生体重、胎龄、气管插管(有创呼吸机)、UVC、PICC、生后3代头孢菌素应用差异均有统计学意义(P<0.05)。感染组气管插管时间、PICC时间、PN时间和住院时间均高于非感染组(P<0.05),白蛋白水平低于非感染组(P<0.05)。logistic回归分析结果,出生体重<1000 g[O^R=2.539(95%CI:1.101,5.856)]、气管插管[O^R=1.952(95%CI:1.056,3.610)]、气管插管时间[O^R=1.089(95%CI:1.019,1.164)]和PICC时间[O^R=1.034(95%CI:1.011,1.057)]均是极低、超低体重早产儿发生医院感染的独立危险因素。结论近年早产儿医院感染率并无减少;胎龄更小、有创通气支持减少、插管时间减少是近两年未发生医院感染早产儿的特征;但3代头孢菌素应用率上升。提高出生体重、减少气管插管、缩短气管插管时间和PICC时间可降低早产儿医院感染发生率。

Yellow nail syndrome accompanied by minimal-change nephrotic syndrome:A case report

BACKGROUND In most cases of yellow nail syndrome(YNS),the classic triad of yellow nails,lymphedema and respiratory manifestations rarely manifest simultaneously.Therefore,diagnosis is delayed or frequently missed.CASE SUMMARY We report a 62-year-old YNS patient presenting with bilateral pleural,pericardial and peritoneal effusions who,2 mo later,developed minimal-change nephrotic syndrome.After treatment with vitamin E,clarithromycin and prednisone for 3 mo,effusions in the chest,pericardium and abdominal cavity decreased while urine protein levels returned to within normal ranges.CONCLUSION Clinicians should consider the possibility of YNS for patients presenting with multiple serous effusions and nephrotic syndromes.

Structural insights into the unusual core photocomplex from a triply extremophilic purple bacterium,Halorhodospira halochloris

Halorhodospira(Hlr.)halochloris is a triply extremophilic phototrophic purple sulfur bacterium,as it is thermophilic,alkaliphilic,and extremely halophilic.The light-harvesting-reaction center(LH1–RC)core complex of this bacterium displays an LH1-Q_(y)transition at 1,016 nm,which is the lowest-energy wavelength absorption among all known phototrophs.Here we report the cryo-EM structure of the LH1–RC at 2.42?resolution.The LH1 complex forms a tricyclic ring structure composed of 16αβγ-polypeptides and oneαβ-heterodimer around the RC.From the cryo-EM density map,two previously unrecognized integral membrane proteins,referred to as protein G and protein Q,were identified.Both of these proteins are single transmembrane-spanning helices located between the LH1 ring and the RC Lsubunit and are absent from the LH1–RC complexes of all other purple bacteria of which the structures have been determined so far.Besides bacteriochlorophyll b molecules(B1020)located on the periplasmic side of the Hlr.halochloris membrane,there are also two arrays of bacteriochlorophyll b molecules(B800 and B820)located on the cytoplasmic side.Only a single copy of a carotenoid(lycopene)was resolved in the Hlr.halochloris LH1–α3β3 and this was positioned within the complex.The potential quinone channel should be the space between the LH1–α3β3 that accommodates the single lycopene but does not contain aγ-polypeptide,B800 and B820.Our results provide a structural explanation for the unusual Q_(y)red shift and carotenoid absorption in the Hlr.halochloris spectrum and reveal new insights into photosynthetic mechanisms employed by a species that thrives under the harshest conditions of any phototrophic microorganism known.

青藤碱通过调控肠道菌群与色氨酸代谢激活芳香烃受体改善类风湿性关节炎

肠道菌群失调与类风湿关节炎(RA)的发生发展密切相关.青藤碱(sinomenine,SIN)是临床上有效用于治疗RA的中药制剂,但SIN如何调节肠道菌群缓解RA仍有待研究.为了确定与SIN改善类风湿关节炎作用相关的关键肠道微生物和差异代谢物,本研究通过16S rRNA基因测序、抗生素干预和粪菌移植实验,评估SIN抗RA作用是否依赖于肠道菌群.然后,通过代谢组学分析、转录组学分析和单菌/差异代谢物体内给药验证,寻找SIN调控肠道菌群以降低RA严重程度的关键菌群、代谢物和作用靶点.实验结果表明:SIN主要通过升高Lactobacillus属丰度改善肠道菌群失调,进而显著缓解胶原诱导的类风湿性关节炎(CIA)症状.同时,SIN可显著提高肠道微生物来源的色氨酸代谢产物吲哚-3-丙烯酸、吲哚-3-丙酸和吲哚-3-乙酸水平.体内、外色氨酸代谢产物给药实验得出,色氨酸代谢产物可通过激活芳香烃受体(AhR),改善Th17/Treg平衡缓解CIA大鼠的关节炎症和免疫反应.最后,L.paracasei和L.case单菌体内定植实验证实,SIN可通过富集L.paracasei和L.case缓解RA症状.综上,SIN通过调控肠道菌群特别是乳酸杆菌属L.paracasei和L.case丰度影响微生物源的色氨酸代谢产物水平来激活AhR协同治疗RA.

Phytochrome B Is Involved in Mediating Red Light-Induced Stomatal Opening in Arabidopsis thaliana

The stomatal pores of higher plants enable gaseous exchange into and out of leaves for photosynthesis and evaporation. Stomatal opening is induced by both blue and red lights. It is shown that blue light-induced stomatal opening is mediated by the blue light receptor phototropins （PHOT1 and PHOT2） and cryptochromes （CRY1 and CRY2）. However, whether phytochrome B （phyB） is involved in red light regulation of stomatal opening remains largely unclear. Here, we report a positive role for Arabidopsis （Arabidopsis thaliana） phyB in the regulation of red light-induced stomatal opening. The phyB mutant stomata displayed a reduced red light response, whereas stomata of the phyB-overexpressing plants displayed a hypersensitive response to red light. In addition, stomata of the cry1 cry2 phyB, photl phot2 phyB, and cry1 phyA phyB triple mutant plants showed more reduced light response than those of the single or double mutant plants under white light, implying that phyB acts in concert with phyA, CRY, and PHOT in light regulation of stomatal opening. Stomata of phyB cop1 mutant opened less wide than those of the cop1 mutant, and stomata of the pif3 pif4 mutant opened wider than those of the wild-type, indicating that COP1, together with the PIFs （phytochrome interacting factors）, may act downstream of PHYB in regulating stomatal opening. Furthermore, quantitative RT-PCR analysis showed that the expression of MYB60 was reduced in the cry1 cry2 and phyA phyB mutants under blue and red lights, respectively, but induced in the CRY1- and phyB-overexpressing plants. These results demonstrate that phyB and CRY might regulate stomatal opening, at least in part, by regulating MYB60 expression.

American, European, and Chinese practice guidelines or consensuses of polycystic ovary syndrome: a comparative analysis

Polycystic ovary syndrome （PCOS） is the most common metabolic and endocrine disorder in women. However, there is no agreement concerning how to diagnose and treat PCOS worldwide. Three practice guidelines or consensuses, including consensus from the European Society of Human Reproduction and Embryology （ESHRE）/the American Society for Reproductive Medicine （ASRM） in Rotterdam, diagnosis criteria and consensus in China, and clinical practice guideline from the Endocrine Society （ES） in the United States are widely recognized. The present paper may provide some guidance for clinical practice based on a comparative analysis of the above three practice guidelines or consensuses.

Evolution of carbides on surface of carburized MSONiL bearing steel

The dissolution and precipitation behaviors of the carbides in carburized M50NiL steel were derived from different solution and tempering treatments.Totally four kinds of carbides of (V,Cr)-rich MC,(Mo,Fe)-rich M2C,Fe-rich M3C and (Fe,Cr)-rich M7C3 were obtained from the carburized M50NiL steel after different heat treatments.The key carbides of carbufized M50NiL steel were proved to be tough V-rich MC and Cr-rich M7C3.The highest hardness (634 HV)and the optimal surface structure with 1.0% volume fraction of uniformly distributed MC carbides were obtained after the carbufized M50NiL steel was solution-treated at 1150 ℃ and tempered at 500 ℃.The quantitative statistics show that 63%of the MC carbides were less than 200 nm under that heat treatment.The variety of carbides changed with solution and tempering conditions.When the solution temperature increased from 1050 to 1150 ℃,the undissolved carbides were proved to be Fe-rich M7C3,Mo-fich MC and (Mo,Fe)-fich M2C.Besides,the equivalent content of V-rich MC was found increased when the tempering temperature changed from 500 to 550 ℃.The combination of high-temperature solution and low-temperature tempering is recommendable heat treatment for the high hardness as well as the tiny and uniformly distributed carbides.

Spindle LiFePO_4 particles as cathode of lithium-ion batteries synthesized by solvothermal method with glucose as auxiliary reductant

The well-distribution spindle Li Fe PO4(LFP)nanoparticles as cathode of lithium secondary batteries were synthesized by a solvothermal reaction route at low temperature(180 °C) in which the ascorbic acid was used as reducing agent. In order to guarantee that the p H values of thermal systems were not affected too much and the reducibility of the system was enhanced at the same time,glucose was chosen as an auxiliary reductant in this reaction. The obtained powders were characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM),and laser particle analyzer. The results show that the carbon-coated uniform spindle olivine Li Fe PO4/C-glucose particles(glucose as auxiliary reductant, LFP/C-G) are prepared with the size 500–600 nm and without any impurity phases. Their electrochemical properties were evaluated by electrochemical impedance spectroscopy,cyclic voltammetry, and galvanostatic charge/discharge tests. LFP/C-G has a higher conductivity and better reversible capability than carbon-coated LFP(LFP/C). The highest discharge capacity of LFP/C-G is 161.3 mAh·g-1at0.1C and 108.6 mAh·g-1at 5.0C, respectively. The results imply that the neat crystal nanostructure of LFP/C-G has excellent capacity retention and cycling stability.The adding of glucose is the key factor for the welldistribution and neat crystal structure of nanoparticles,thus the electrochemical performances of materials are improved.

Cerebral palsy in children born after assisted reproductive technology: a meta-analysis

Background Several studies have assessed the association between cerebral palsy(CP)and assisted reproductive technology(ART),but the results remain controversial.We conducted a meta-analysis to evaluate the risk of CP after ART compared with natural conceptions and to examine CP risk separately in ART singletons,multiples and preterm births.Methods Web-based databases(PubMed,Embase,the Cochrane Library,and Web of Science)were searched until November 22,2020.Studies which compare CP rates after ART with natural conceptions were included.The Newcastle–Ottawa Scale was used to assess the quality of the included studies.Effect estimates were extracted and combined using the fixed-effects or random-effects model depending on the heterogeneity test.Results There were nine studies included in the meta-analysis.The included studies were of moderate or high quality.A significantly higher risk of CP[odds ratio(OR)=2.17,95%confidence interval(CI)1.72–2.74]was found in ART children(n=89,214)compared with naturally conceived children(n=4,160,745).The significantly higher risk decreased when data were restricted to singletons(OR=1.36,95%CI 1.16–1.59)and disappeared when data were restricted to multiples(OR=1.05,95%CI 0.86–1.29)or preterm births(OR=1.53,95%CI 0.66–3.56).Subgroup and sensitivity analyses indicated that the overall results were robust.Conclusions The risk of CP is increased more than two-fold after ART.This increased risk is largely due to increased rates of multiple birth and preterm delivery in ART children.

Acupuncture for treating polycystic ovary syndrome:guidance for future randomized controlled trials

Objective： To provide guidance for future randomized controlled trials （RCTs） based on a review con- cerning acupuncture for treating polycystic ovary syndrome （PCOS）. Methods： A comprehensive literature search was conducted in October 2015 using MEDLINE, EMBASE, SCISEARCH, Cumulative Index to Nursing and Allied Health Literature, the Cochrane Menstrual Disorders and Subfertility Group trials register, Allied and Complementary Medi- cine （AMED）, China National Knowledge Infrastructure （CNKI）, and the Wanfang databases. RCTs comparing either acupuncture with no/sham/pharmacological intervention or a combination of acupuncture and conventional therapy with conventional therapy in the treatment of PCOS were included in this review. A quality evaluation was performed for each of the included studies. Results： Thirty-one RCTs were included in the review and were divided into four categories according to the type of intervention used in the comparator or control group. Menstrual frequency, hor- mones, anthropometrics, insulin sensitivity, blood lipids, and fertility were used as the main measurements to assess the effects of acupuncture on the patients with PCOS. Thirty trials, except for one, showed an improvement in at least one of the indicators of PCOS after acupuncture treatment. However, normalizing the methodological and reporting format remains an issue. Conclusions： Based upon this review of current clinical trials concerning acupuncture for treating PCOS, we provide guidelines for better clinical trial design in the future.

Novel Hyperbranched Polymers as Host Materials for Green Thermally Activated Delayed Fluorescence OLEDs

A series of novel hyperbranched polymers （HBPs） consisting ofa 2,7-subsituted 9-（heptadecan-9-yl）-9H-carbazole unit （A2＋A2＇） and a tetra-substituted green thermally activated delayed fluorescence （TADF） dye of 2,3,5,6-tetra（9H- carbazol-9-yl）-4-pyridinecarbonitrile （4CzCNPy, B4） have been synthesized via Suzuki cross-coupling reaction following an ＂Az＋A2＇＋B4＂ method. The polymers are named according to the polymerization ratio of 4CzCNPy monomer （5 mol%, 10 mol% and 15 mol% for HBPs of P2-P4 respectively, and 0 mol% for the control linear polymer P1）. Their thermal, optoelectronic and electrochemical properties have been characterized by a combination of techniques. All the polymers exhibit high thermal stability with the decomposition temperatures （Ta） above 400 ℃ and glass transition temperatures （Tg） up to 98℃. Unfortunately, the incorporation of TADF moiety into these HBP materials induced non-TADF characteristics. However, when the HBPs functionalized as the host for our previously developed 4CzCNPy TADF dopant in solution processed devices, maximum external quantum efficiency of 5.7% and current efficiency of 17.9 cd/A have been achieved in P3-based device, which is significantly higher than those of 1.5% and 4.2 cd/A for the linear polymer P1.

Nanofabrication of the gold scanning probe for the STM-SECM coupling system with nanoscale spatial resolution

Scanning probe is the key issue for the electrochemical scanning probe techniques(EC-SPM) such as EC-scanning tunnel microscopy(STM), EC-atomic force microscopy(AFM) and scanning electrochemical microscopy(SECM), especially the insulative encapsulation of the nanoelectrode probe for both positioning and electrochemical feedbacks. To solve this problem,we develop a novel fabrication method of the gold nanoelectrodes: firstly, a micropipette with nanomter-sized orifice was prepared as the template by a laser puller; secondly, the inside wall of micropipette apex was blocked by compact and conic Au nano-piece through electroless plating; thirdly, the Au nano-piece was grown by bipolar electroplating and connected with a silver wire as a current collector. The fabricated Au nanoelectrode has very good voltammetric responses for the electrodic processes of both mass transfer and adsorption. The advantage lies in that it is well encapsulated by a thin glass sealing layer with a RG value lowered to 1.3, which makes it qualified in the SECM-STM coupling mode. On one hand, it can serve as STM tip for positioning which ensures the high spatial resolution; on the other hand, it is a high-quality nanoelectrode to explore the local chemical activity of the substrate. The nanofabrication method may promote the SPM techniques to obtain simultaneously the physical and chemical images with nanoscale spatial resolution, which opens a new approach to tip chemistry in electrochemical nanocatalysis and tip-enhanced spectroscopy.

Flow structure and unsteady fluctuation with separation over a two-dimensional backward-facing step

The flow over a backward-facing step(BFS)is a typical separation and reattachment flow.Its flow structures and unsteady mechanisms are still not well explored.In this paper,the global velocity fields of a BFS are obtained by a synchronous particle image velocimetry(PIV)system with Reh=5345(Reynolds number)and Er=2(expansion ratio).Flow structures are distinguished and defined by the fraction of the negative velocity(upn).The reattachment zone(Lr)is quantitatively defined as(u0.9,u/0.1)on the bottom wall.Spatial distribution of the large-scale vortices couples well with the divided flow structures and their temporal evolution presenting four stages(forming,developing,shedding and redeveloping)when travel downstream.The unsteady motions with various low frequencies are well explained by the coherent vortices and flow structures.Among the unsteady low frequency motions,the Kelvin Helmholtz(KH)vortices and the oscillation of Xr(OX)come likely from the free shear layer.The KH vortices contribute to the unsteadiness of the temporal flow,and the OX is the primary response to the vortical fluctuations.