环氧树脂灌封料的固化动力学及固化工艺

采用流变学手段、非等温差示扫描量热法和原位升温傅里叶变换红外光谱法研究了2种环氧树脂灌封料的固化动力学,并对其固化工艺进行设计与验证。采用Kissinger和Flynn-Wall-Ozawa方程计算得到2种灌封料的平均表观活化能分别为70.76 kJ/mol和61.61 kJ/mol。根据DSC非等温曲线外推法获得体系的理论固化温度及时间,并依此得到的固化物与原始条件制备的固化物进行力学性能对比,发现影响固化工艺设计的关键因素是温度和时间。研究结果可为环氧树脂灌封料的固化工艺条件设计及实际应用提供理论参考。

ESBR/SiO2胶乳的破乳动力学及复合材料性能

系统探究了NaCl和CaCl2溶液絮凝乳聚丁苯橡胶/白炭黑(ESBR/SiO2)胶乳的行为及破乳动力学,考察了硅烷偶联剂TESPT和NXT对复合材料力学性能、动态黏弹性能和流变性能的影响。研究发现,NaCl溶液破乳呈现匀速破乳、加速破乳的过程,而CaCl2溶液破乳则呈现匀速破乳、加速破乳和减速破乳3个阶段。白炭黑粒子对体系破乳效应的影响存在差异,这主要是因为二价Ca^2+对电荷中和能力比一价Na^+高,导致白炭黑的成核中心作用不同。此外,发现硅烷偶联剂NXT使白炭黑在橡胶基体中的分散性显著提高,使其复合材料的硫化性能得到优化,力学性能明显提高,在保持抗湿滑性能时滚动阻力明显降低。

纤维素性纵隔炎的影像诊断

纤维素性纵隔炎是一种纵隔良性疾病, 是由纵隔中纤维组织增生引起。根据受累范围, 分为肉芽肿性和非肉芽肿性两种亚型。肉芽肿性通常与感染引起的异常免疫反应有关;非肉芽肿性可能是特发性的, 或与自身免疫有关。这两种亚型均会出现与重要纵隔结构梗阻或压迫相关的体征和症状。CT增强是诊断和鉴别诊断纤维素性纵隔炎的首选检查方法。影像学特征包括纵隔软组织浸润(伴或不伴钙化), 伴有纵隔血管结构和/或呼吸消化道的压迫或阻塞。当在适当的临床背景下发现这些特征时, 放射科医师就可以提出纤维素性纵隔炎的诊断。在初始和后续的影像学检查中, 仔细评估对于排除潜在恶性肿瘤、评估疾病进展、识别并发症和评估治疗反应至关重要。

Dual single-atom Ce-Ti/MnO_(2)catalyst enhances low-temperature NH_(3)-SCR performance with high H_(2)O and SO_(2)resistance

Mn-based catalysts have exhibited promising performance in low-temperature selective catalytic reduction of NOx with NH_(3)(NH_(3)-SCR).However,challenges such as H_(2)O-or SO_(2)-induced poisoning to these catalysts still remain.Herein,we report an efficient strategy to prepare the dual single-atom Ce-Ti/MnO_(2)catalyst via ball-milling and calcination processes to address these issues.Ce-Ti/MnO_(2)showed better catalytic performance with a higher NO conversion and enhanced H_(2)O-and SO_(2)-resistance at a lowtemperature window(100−150°C)than the MnO_(2),single-atom Ce/MnO_(2),and Ti/MnO_(2)catalysts.The in situ infrared Fourier transform spectroscopy analysis confirmed there is no competitive adsorption between NOx and H_(2)O over the Ce-Ti/MnO_(2)catalyst.The calculation results showed that the synergistic interaction of the neighboring Ce-Ti dual atoms as sacrificial sites weakens the ability of the active Mn sites for binding SO_(2)and H_(2)O but enhances their binding to NH_(3).The insight obtained in this work deepens the understanding of catalysis for NH_(3)-SCR.The synthesis strategy developed in this work is easily scaled up to commercialization and applicable to preparing other MnO_(2)-based single-atom catalysts.

含内构件的循环流化床的动态压力特性

针对含内构件的循环流化床,以石英砂为物料,使用动态压力传感器测量了含内构件的流化床中气固两相流的动态压力,分析了床内的瞬时压力特性.结果表明,在进出口总压降中,文丘里压降最大,占主床压降的60%以上.表观气速和固体颗粒循环流率共同影响循环流化床内的压力特性.压力瞬时波动功率谱分析表明,压力波动对应一个主频,表观气速越小、颗粒循环流率越大时,压力波动越大,且循环流化床底部压力波动比上部大.加入内构件能有效引导气流,使流动更均匀.

Mercury removal from coal combustion flue gas by modified fly ash

Fly ash is a potential alternative to activated carbon for mercury adsorption. The effects of physicochemical properties on the mercury adsorption performance of three fly ash samples were investigated. X-ray fluorescence spectroscopy, X-ray photoelectron spectroscopy, and other methods were used to characterize the samples. Results indicate that mercury adsorption on fly ash is primarily physisorption and chemisorption. High specific surface areas and small pore diameters are beneficial to efficient mercury removal. Incompletely burned carbon is also an important factor for the improvement of mercury removal efficiency, in particular. The C-M bond, which is formed by the reaction of C and Ti, Si and other elements, may improve mercury oxidation. The samples modified with CuBr2 , CuCl 2 and FeCl3 showed excellent performance for Hg removal, because the chlorine in metal chlorides acts as an oxidant that promotes the conversion of elemental mercury (Hg0) into its oxidized form (Hg2+). Cu2+ and Fe3+ can also promote Hg 0 oxidation as catalysts. HCl and O2 promote the adsorption of Hg by modified fly ash, whereas SO2 inhibits the Hg adsorption because of competitive adsorption for active sites. Fly ash samples modified with CuBr2 , CuCl2 and FeCl3 are therefore promising materials for controlling mercury emissions.

Mechanism of Hg^0 oxidation in the presence of HCl over a commercial V_2O_5–WO_3/TiO_2 SCR catalyst

Experiments were conducted in a fixed-bed reactor containing a commercial V2O5/WO3/TiO2 catalyst to investigate mercury oxidation in the presence of HCl and O2. Mercury oxidation was improved significantly in the presence of HCl and O2, and the Hg0 oxidation efficiencies decreased slowly as the temperature increased from 200 to 400°C. Upon pretreatment with HCl and O2 at 350°C, the catalyst demonstrated higher catalytic activity for Hg0 oxidation. Notably,the effect of pretreatment with HCl alone was not obvious. For the catalyst treated with HCl and O2, better performance was observed with lower reaction temperatures. The results showed that both HCl and Hg0 were first adsorbed onto the catalyst and then reacted with O2 following its adsorption, which indicates that the oxidation of Hg0 over the commercial catalyst followed the Langmuir–Hinshelwood mechanism. Several characterization techniques, including Hg0temperature-programmed desorption(Hg-TPD) and X-ray photoelectron spectroscopy(XPS), were employed in this work. Hg-TPD profiles showed that weakly adsorbed mercury species were converted to strongly bound species in the presence of HCl and O2. XPS patterns indicated that new chemisorbed oxygen species were formed by the adsorption of HCl, which consequently facilitated the oxidation of mercury.

Role of NO in Hg^0 oxidation over a commercial selective catalytic reduction catalyst V_2O_5–WO_3/TiO_2

Experiments were conducted in a fixed-bed reactor that contained a commercial catalyst,V_2O_5–WO_3/TiO_2,to investigate mercury oxidation in the presence of NO and O_2.Mercury oxidation was improved by NO,and the efficiency was increased by simultaneously adding NO and O_2.With NO and O_2 pretreatment at 350°C,the catalyst exhibited higher catalytic activity for Hg^0 oxidation,whereas NO pretreatment did not exert a noticeable effect.Decreasing the reaction temperature boosted the performance of the catalyst treated with NO and O_2.Although NO promoted Hg^0 oxidation at the very beginning,excessive NO counteracted this effect.The results show that NO plays different roles in Hg^0oxidation; NO in the gaseous phase may directly react with the adsorbed Hg^0,but excessive NO hinders Hg^0 adsorption.The adsorbed NO was converted into active nitrogen species(e.g.,NO_2) with oxygen,which facilitated the adsorption and oxidation of Hg^0.Hg^0 was oxidized by NO mainly by the Eley–Rideal mechanism.The Hg^0 temperature-programmed desorption experiment showed that weakly adsorbed mercury species were converted to strongly bound ones in the presence of NO and O_2.

High-throughput screening identifies established drugs as SARS-CoV-2 PLpro inhibitors

A new coronavirus(SARS-CoV-2)has been identified as the etiologic agent for the COVID-19 outbreak.Currently,effective treatment options remain very limited for this disease;therefore,there is an urgent need to identify new anti-COVID-19 agents.In this study,we screened over 6,000 compounds that included approved drugs,drug candidates in clinical trials,and pharmacologically active compounds to identify leads that target the SARS-CoV-2 papain-like protease(PLpro).Together with main protease(Mpro),PLpro is responsible for processing the viral replicase polyprotein into functional units.There-fore,it is an attractive target for antiviral drug develop-ment.Here we discovered four compounds,YM155,cryptotanshinone,tanshinone I and GRL0617 that inhibit SARS-CoV-2 PLpro with IC50 values ranging from 1.39 to 5.63 pmol/L.These compounds also exhibit strong antiviral activities in cell-based assays.YM155,an anti-cancer drug candidate in clinical trials,has the most potent antiviral activity with an EC50 value of 170 nmol/L.In addition,we have determined the crystal structures of this enzyme and its complex with YM155,revealing a unique binding mode.YM155 simultaneously targets three"hot"spots on PLpro,including the substrate-binding pocket,the interferon stimulating gene product 15(ISG15)binding site and zinc finger motif.Our results demonstrate the efficacy of this screening and repur-posing strategy,which has led to the discovery of new drug leads with clinical potential for COVID-19 treatments.

Hg^0 removal from flue gas over different zeolites modified by Fe Cl_3

The elemental mercury removal abilities of three different zeolites(Na A, Na X, HZSM-5)impregnated with iron(Ⅲ) chloride were studied on a lab-scale fixed-bed reactor. X-ray diffraction, nitrogen adsorption porosimetry, Fourier transform infrared spectroscopy,X-ray photoelectron spectroscopy, and temperature programmed desorption(TPD) analyses were used to investigate the physicochemical properties. Results indicated that the pore structure and active chloride species on the surface of the samples are the key factors for physisorption and oxidation of Hg0, respectively. Relatively high surface area and micropore volume are beneficial to efficient mercury adsorption. The active Cl species generated on the surface of the samples were effective oxidants able to convert elemental mercury(Hg0)into oxidized mercury(Hg2+). The crystallization of Na Cl due to the ion exchange effect during the impregnation of Na A and Na X reduced the number of active Cl species on the surface, and restricted the physisorption of Hg0. Therefore, the Hg0 removal efficiencies of the samples were inhibited. The TPD analysis revealed that the species of mercury on the surface of Fe Cl3–HZSM-5 was mainly in the form of mercuric chloride(Hg Cl2), while on Fe Cl3–Na X and Fe Cl3–Na A it was mainly mercuric oxide(Hg O).

Role of NO and SO_(2)in mercury oxidation over a La_(2)O_(3)/Fe_(2)O_(3)catalyst with high thermal stability

In this study,the thermal stability of a ferric oxide catalyst for mercury oxidation was found to be considerably promoted by doping with La_(2)O_(3).The catalysts doped with La_(2)O_(3)maintained a higher surface area when subjected to high-temperature calcination,with lower average pore size and a narrower pore size distribution.X-ray diffraction(XRD)results revealed that La_(2)O_(3)doping hinders the growth of catalyst particles and crystallization of the material at high temperatures.Both NO and SO_(2)inhibited Hg^(0)oxidation over the La_(2)O_(3)/Fe_(2)O_(3)catalyst.Fourier transform infrared(FTIR)spectra revealed that SO_(2)reacts with O_(2)over the catalysts to form several species that are inert for mercury oxidation,such as S042^(-),HS04^(-),or other related species;these inert species cover the catalyst surface and consequently decrease Hg^(0)oxidation capacity.In addition,NO or SO_(2)competed with Hg^(0)for active sites on the La_(2)O_(3)/Fe_(2)O_(3)catalyst and hindered the adsorption of mercury,thereby inhibiting subsequent Hg^(0)oxidation.Hg^(0)oxidation on the La_(2)O_(3)/Fe_(2)O_(3)catalyst mainly followed the Eley-Rideal mechanism.Moreover,the inhibition effects of NO and SO_(2)were at least partially reversible,and the catalytic activity was temporarily restored after eliminating NO or S0_(2).

Crystal structure of a PP2A B56-BubR1 complex and its implications for PP2A substrate recruitment and localization

蛋白质磷酸酶 2A (PP2A ) 在大多数房间类型说明全部的 Ser/Thr 磷酸酶活动的多数并且调整许多生物进程。PP2A holoenzymes 包含一个支架 A 子单元，一个催化 C 子单元，并且 regulatory/targeting B 子单元之一。B 子单元控制 PP2A 本地化和底层特性，是 PP2A 规定的一个关键方面，糟糕仍然保持怎么样，理解。kinetochore 是为 PP2A 工作的一个批评地点，在 PP2A 通过它和 BubR1 的相互作用安排染色体分离的地方。PP2A-BubR1 相互作用在两锭子检查点 silencing 和稳定的 microtubule-kinetochore 附件起重要作用。这里我们在场 PP2A B56-BubR1 建筑群的水晶结构，它证明一个保存 BubR1 LxxIxE 主题绑在 B56 伪热的凹面方面重复。BubR1 主题绑在在 B56 热之间形成的一条沟重复 3 和 4，它离为 PP2A 催化 C 子单元的 B56 有约束力的表面相当远并且因此是不大可能的影响 PP2A 活动。另外， B56 上的 BubR1 有约束力的地点远离 shugoshin 的 B56 有约束力的地点，另一 kinetochore PP2A 有约束力的蛋白质，并且因此， BubR1 和 shugoshin 罐头潜在地同时与 PP2A-B56 交往。我们的结构、生物化学的分析显示有 LxxIxE 主题的另外的蛋白质可以也绑在一样的 PP2A B56 表面。因此，我们 PP2A B56-BubR1 建筑群的结构提供 B56 子单元怎么指导 PP2A 的招募到特定的目标的重要卓见。

Cryo-EM snapshots of mycobacterial arabinosyltransferase complex EmbB2-AcpM2

Inhibition of Mycobacterium tuberculosis(Mtb)cell wall assembly is an established strategy for anti-TB chemotherapy.Arabinosyltransferase EmbB,which catalyzes the transfer of arabinose from the donor decaprenyl-phosphate-arabinose(DPA)to its arabinosyl acceptor is an essential enzyme for Mtb cell wall synthesis.Analysis of drug resistance mutations suggests that EmbB is the main target of the front-line anti-TB drug,ethambutol.Herein,we report the cryo-EM structures of Mycobacterium smegmatis EmbB in its"resting state"and DPA-bound"active state".EmbB is a fifteen-transmembrane-spanning protein,assembled as a dimer.Each protomer has an associated acyl-carrier-protein(AcpM)on their cytoplasmic surface.Confor-mational changes upon DPA binding indicate an asym-metric movement within the EmbB dimer during catalysis.Functional studies have identified critical residues in substrate recognition and catalysis,and demonstrated that ethambutol inhibits transferase activity of EmbB by competing with DPA.The structures represent the first step directed towards a rational approach for anti-TB drug discovery.

Reactivity of Pyrogenic Carbonaceous Matter (PCM) in mediating environmental reactions: Current knowledge and future trends

Pyrogenic Carbonaceous Matter(PCM;e.g.,black carbon,biochar,and activated carbon)are solid residues from incomplete combustion of fussil fuel or biomass.They are traditionally viewed as inert adsorbents for sequestering contaminants from the aqueous phase or providing surfaces for microbes to grow.In this account,we reviewed the recently discovered reactivity of PCM in promoting both chemical and microbial synergies that are important in pollutant transformation,biogeochemical processes of redox-active elements,and climate change mitigation with respect to the interaction between biochar and nitrous oxide(N2O).Moreover,we focused on our group's work in the PCM-enhanced abiotic transformation of nitrogenous and halogenated pollutants and conducted in-depth analysis of the reaction pathways.To understand what properties of PCM confer its reactivity,our group pioneered the use of PCM-like polymers,namely conjugated microporous polymers(CMPs),to mimic the performance of PCM.This approach allows for the controlled incorporation of specific surface properties(e.g.,quinones)into the polymer network during the polymer synthesis.As a result,the relationship between specific characteristics of PCM and its reactivity in facilitating the decay of a model pollutant was systematically studied in our group's work.The findings summarized in this account help us to better understand an overlooked environmental process where PCM synergistically interacts with various environmental reagents such as hydrogen sulfide and water.Moreover,the knowledge gained in these studies could inform the design of a new generation of reactive carbonaceous materials with tailored properties that are highly efficient in contaminant removal.

Effect of Al2O3 doping on the structure and performance of an Al2O3/Fe2O3 catalyst for mercury oxidation

In this study,the thermal stability of a Fe2 O3 catalyst for mercury oxidation was significantly improved by doping with Al2 O3.After 1 hr,the catalyst doped with 10 wt.%Al2 O3 still exhibited a mercury conversion efficiency of 70.9%,while the undoped sample even lost its catalytic activity.Doping with Al2 O3 retarded the collapse of the catalyst mesoporous structure during high-temperature calcination,and the doped samples maintained a higher specific surface area,smaller pore size,and narrower pore size distribution.Transmission electron microscope images revealed that after calcination at 350℃,the average size of the catalyst grains in Fe2 O3 was 23.4 nm;however,the corresponding values for 1%Al2 O3/Fe2 O3,3%Al2 O3/Fe2 O3,and 10%Al2 O3/Fe2 O3 were only 13.3,7.1,and 4.7 nm,respectively.Results obtained from X-ray diffraction and thermogravimetry coupled with differential scanning calorimetry confirmed that doping with Al2 O3 also retards the crystallization of the catalysts at high temperature,constraining catalyst grains to a smaller size.

A machine learning model for diagnosing acute pulmonary embolism and comparison with Wells score,revised Geneva score,and Years algorithm

Background:Acute pulmonary embolism(APE)is a fatal cardiovascular disease,yet missed diagnosis and misdiagnosis often occur due to non-specific symptoms and signs.A simple,objective technique will help clinicians make a quick and precise diagnosis.In population studies,machine learning(ML)plays a critical role in characterizing cardiovascular risks,predicting outcomes,and identifying biomarkers.This work sought to develop an ML model for helping APE diagnosis and compare it against current clinical probability assessment models.Methods:This is a single-center retrospective study.Patients with suspected APE were continuously enrolled and randomly divided into two groups including training and testing sets.A total of 8 ML models,including random forest(RF),Naïve Bayes,decision tree,K-nearest neighbors,logistic regression,multi-layer perceptron,support vector machine,and gradient boosting decision tree were developed based on the training set to diagnose APE.Thereafter,the model with the best diagnostic performance was selected and evaluated against the current clinical assessment strategies,including the Wells score,revised Geneva score,and Years algorithm.Eventually,the ML model was internally validated to assess the diagnostic performance using receiver operating characteristic(ROC)analysis.Results:The ML models were constructed using eight clinical features,including D-dimer,cardiac troponin T(cTNT),arterial oxygen saturation,heart rate,chest pain,lower limb pain,hemoptysis,and chronic heart failure.Among eight ML models,the RF model achieved the best performance with the highest area under the curve(AUC)(AUC=0.774).Compared to the current clinical assessment strategies,the RF model outperformed the Wells score(P=0.030)and was not inferior to any other clinical probability assessment strategy.The AUC of the RF model for diagnosing APE onset in internal validation set was 0.726.Conclusions:Based on RF algorithm,a novel prediction model was finally constructed for APE diagnosis.When compared to the current clinical assessment strategies,the RF model achieved better diagnostic efficacy and accuracy.Therefore,the ML algorithm can be a useful tool in assisting with the diagnosis of APE.

NiO@Ni nanoparticles embedded in N-doped carbon for efficient photothermal CO_(2) methanation coupled with H_(2)O splitting

Photothermal carbon dioxide(CO_(2))methanation has attracted increasing interest in solar fuel synthesis,which employs the advantages of photocatalytic H_(2)O splitting as a hydrogen source and photothermal catalytic CO_(2) reduction.This work prepared three-dimensional(3D)honeycomb N-doped carbon(NC)loaded with core–shell NiO@Ni nanoparticles generated in situ at 500℃(NiO@Ni/NC-500).Under the photothermal catalysis(200℃,1.5 W/cm^(2)),the CH_(4) evolution rate of NiO@Ni/NC-500 reached 5.5 mmol/(g·h),which is much higher than that of the photocatalysis(0.8 mmol/(g·h))and the thermal catalysis(3.7 mmol/(g·h)).It is found that the generated localized surface plasmon resonance enhances the injection of hot electrons from Ni to NiO,while thermal heating accelerates the thermal motion of radicals,thus generating a strong photo-thermal synergistic effect on the reaction.The CO_(2) reduction to CH_(4) follows the*OCH pathway.This work demonstrates the synergistic effect of NiO@Ni and NC can enhance the catalytic performance of photothermal CO_(2) reduction reaction coupled with water splitting reaction.