预测典型变形高温合金均匀化动力学的新模型

提出一种基于扩散距离概念的变形高温合金均匀化动力学新预测模型。通过定量电子探针(EPMA)分析,系统研究典型镍基变形高温合金(GH4141)的微观偏析和均匀化动力学。研究发现,基于残余偏析指数模型预测的均匀化动力学与实际测量结果之间存在一定差异。实验和理论分析均表明,考虑了过去通常被忽略的扩散方向因子的一维扩散距离模型可以合理地预测均化动力学。新模型在只需知道原始枝晶臂间距和扩散系数前提下即可完成预测计算,这为变形高温合金均匀化动力学预测提供了一种新的选择。

低层错能镍基单晶高温合金压缩行为和变形组织的温度相关性

在室温至1000℃的范围内,研究温度对一种低层错能镍基单晶高温合金压缩行为和变形组织的影响。研究结果表明,压缩行为和变形组织均表现出温度相关性。室温下该合金具有较高屈服强度,600℃时屈服强度有所下降;随后,随着温度的升高,屈服强度持续增加,并在800℃时达到最大值;在800℃以上时,屈服强度迅速降低。通过透射电子显微镜观察揭示合金变形机制。位错缠结和位错对塞积是室温下屈服强度较高的主要原因。在600℃时,变形机制从反相畴界切割向堆垛层错切割转变,这导致屈服强度略有下降。在800℃时,变形机制以堆垛层错切割为主,而Lomer-Cottrell锁和不同方向堆垛层错之间的反应导致最大的屈服强度。在900℃及以上时,虽然仍存在一些层错,但主要变形机制为位错绕过机制。最后,讨论变形机制和压缩行为的温度依赖性。

Sn-20Bi-xCu-yIn焊料在3.5%NaCl溶液中的腐蚀特性

研究室温条件下Sn-20Bi-xCu-yIn(x=0.3%,0.5%,质量分数;y=1%,2%,3%,质量分数)合金在3.5%(质量分数)NaCl溶液中的腐蚀行为。采用电化学阻抗谱图(EIS)、动电位极化曲线和表面腐蚀产物表征研究焊料的耐腐蚀性能。EIS和极化曲线结果表明,随着In和Cu含量的增加,焊料的耐腐蚀性能降低。采用扫描电镜、能量色散光谱、X射线衍射和X射线光电子能谱对腐蚀产物进行表征。腐蚀产物Sn_(3)O(OH)_(2)Cl_(2)结构松散,不能起到保护作用。Sn-20Bi-0.3Cu-1In的耐腐蚀性能最好。

4D label-free proteomic analysis of vitreous from patients with rhegmatogenous retinal detachment

AIM:To identify metabolites,proteins,and related pathways involved in the etiology of rhegmatogenous retinal detachment(RRD)for use as biomarkers in diagnosing and treating RRD.METHODS:Vitreous specimens were collected and liquid chromatography-tandem mass spectrometry analysis was per formed using the four-dimensional label-free technique.Statistically significant differentially expressed proteins,gene ontology(GO)terms,Kyoto Encyclopedia of Genes and Genomes(KEGG)pathway representations,and protein interactions were analyzed.RESULTS:Nine specimens were subjected to proteomic analysis.In total,161 proteins were identified as differentially expressed proteins(DEPs),including 53 upregulated proteins and 108 downregulated proteins.GO functional analysis revealed that some DEPs were enriched in neuron-related terms and membrane protein terms.Moreover,KEGG analysis indicated that the cell adhesion molecule metabolic pathway was associated with the greatest number of DEPs.Finally,the evaluation of protein-protein interaction network revealed that DEPs were clustered in neuronal adhesion,apoptosis,inflammation and immune responses,correct protein folding,and glycolysis.CONCLUSION:Proteomic profiling is useful for the exploration of molecular mechanisms that underlie RRD.This study reveals increased expression levels of proteins related to heat shock protein content,glycolysis,and inflammatory responses in RRD.Knowledge regarding biomarkers of RRD pathogenesis may help to prevent the occurrence of RRD in the future.

Design of a low-alloy high-strength and high-toughness martensitic steel

To develop a high strength low alloy(HSLA) steel with high strength and high toughness,a series of martensitic steels were studied through alloying with various elements and thermodynamic simulation.The microstructure and mechanical properties of the designed steel were investigated by optical microscopy,scanning electron microscopy,tensile testing and Charpy impact test.The results show that cementite exists between 500℃ and 700℃,M 7 C 3 exits below 720℃,and they are much lower than the austenitizing temperature of the designed steel.Furthermore,the Ti(C,N) precipitate exists until 1280℃,which refines the microstructure and increases the strength and toughness.The optimal alloying components are 0.19% C,1.19% Si,2.83% Mn,1.24% Ni,and 0.049% Ti;the tensile strength and the V notch impact toughness of the designed steel are more than 1500 MPa and 100 J,respectively.

Chronic photodamage in the chicken retina using 650-nm semiconductor laser

AIM: To investigate the occurrence of chronic photodamage in the cone-based retina, following long-term exposure to a 650-nm semiconductor laser(power: 2 mW). METHODS: Chickens fed for 1 mo under natural light after hatching were irradiated with 650-nm laser light at different times each day. Fifteen animals were included in each group. Group A was a control group, irradiated with natural light during the entire study. Group B was irradiated with laser for 3 min/d. Group C was irradiated with laser for 6 min/d. Group D was irradiated with laser for 30 min/d. The duration of the light experiment was 6 mo. We obtained data at 1, 3, and 6 mo, including measuring the retinal thickness in vivo using optical coherence tomography, hematoxylin and eosin staining, TUNEL assay, apoptosis staining, malondialdehyde(MDA) content, superoxide dismutase(SOD) activity, and Western blotting to detect changes in L/M opsins and rhodopsin. RESULTS: At 1 mo, the MDA content in Group D was higher than that observed in Group A(P=0.019). At 3 mo the MDA content in Groups C and D was higher than that reported in Group A(P=0.026, 0.003). At 6 mo, the MDA content in Groups B, C, and D was higher than that observed in Group A(P=0.038, 0.032, 0.000, respectively). There was no difference in SOD activity, and L/M opsin and rhodopsin content between the groups at 1 and 3 mo. The SOD activity in group D was significantly decreased at 6 mo(P=0.000), as was the content of rhodopsin. There was no significant reduction observed in retinal thickness, abnormal cell arrangement, and positive staining of TUNEL in the groups during the 6-month study period.CONCLUSION: Irradiation using a 650 nm semiconductor laser(power: 2 mW) for 6 min per day over 6 mo do not cause photodamage. Similarly, a 3-month exposure of 30 min per day do not cause damage. However, irradiation for 6 mo resulted in a significant increase in the content of free radicals and a decrease in the content of rhodopsin in the retina, suggesting the presence of photodamage.

多聚氮杂环的脱氮自由基转化:C−N键的构建研究进展

多聚氮杂环化合物在有机合成、药物化学以及材料化学等领域具有重要的作用.人们已经在多聚氮杂环的修饰和可控转换领域取得了诸多突破性的研究成果.在多种多聚氮杂环转换反应中,脱氮是一类重要反应,可以快速地构建其他氮杂环或者C−N键.通常而言,多聚氮杂环化合物更易于脱氮形成金属卡宾中间体,继而发生后续串联或环化反应,但涉及自由基中间体的多聚氮杂环脱氮反应尚未得到充分关注和研究.在过去几年中,得益于现代合成手段如有机光化学合成、有机电化学合成和有机光电合成等的革新,自由基化学得到快速发展,建立了很多多聚杂环脱氮自由基串联反应,为高度复杂的杂环骨架或具有复杂杂环体系的天然产物提供了一条通用且便捷的合成路径.光催化剂在有效地将可见光中的能量转移至非吸收化合物方面的应用越来越受到关注,该方法可温和而有效地生成自由基,以新的方式形成化学键.此外,啉钴与卟啉铁催化剂在多聚杂环的脱氮反应中亦展现出较好的催化性能.本文综述了多聚氮杂环的脱氮自由基转化(C‒N键的构建)领域的最新进展,重点讨论了脱氮生成自由基的方法与串联模式和反应机理,分析了存在的挑战.本文还根据反应底物的类别从四个模块展开讨论:(1)苯并三嗪和苯并噻三嗪的自由基脱氮串联反应;(2)苯并三氮唑的自由基脱氮串联反应;(3)吡啶三氮唑与四氮唑的脱氮反应;(4)3-氨基吲唑的自由基脱氮反应.综上,研究者们通过多聚氮杂环的脱氮自由基转化(C‒N键的构建)的方法合成了一些重要的药物分子及其前体,并证明了该方法具有潜在的应用价值.未来,将多聚氮杂环脱氮反应应用于活性天然产物合成与修饰是非常可行的.

Effect of intravitreal ranibizumab on fibrovascular membranes in patients with proliferative diabetic retinopathy

AIM: To assess the effects of intravitreal ranibizumab(IVR) on angiogenesis and glial activity of the fibrovascular membrane(FVM) in patients with proliferative diabetic retinopathy(PDR). METHODS: Forty-two eyes from 42 patients with PDR requiring vitrectomy were included and divided into two groups: control group(n=16) did not receive IVR, while IVR group(n=26) underwent IVR 5 d before vitrectomy. FVM specimens were collected by the same surgeon during the interventions. Histopathological morphology was examined by hematoxylin-eosin(H-E) staining and cell densities in the FVM was assessed. Microvessels were outlined by immunohistochemical staining of CD31 and microvessel density(MVD) assessed as an index of FVM angiogenesis. Dual-color immunofluorescence staining, and confocal microscopy was used to detect co-localization and relative expression levels of glial fibrillary acidic protein(GFAP) and α-smooth muscle actin(α-SMA) as markers of glialmesenchymal transition(GMT). The GMT index(GI;ratio of relative GFAP/α-SMA expression) was used to semi-quantify the degree of GMT or glial activity of FVMs. RESULTS: H-E staining showed similar vascularization in both groups, with microvessels and scattered stromal cells in the matrix. Infiltrated cell densities did not differ significantly between the two groups(P>0.05). The MVD of the IVR group(130.62±15.46/mm~2) was significantly lower than that of the controls(142.25±19.16/mm~2, P<0.05). In both groups, all sections were strongly immunostained for GFAP and α-SMA. The Pearson’s correlation coefficients(PCC) of intensity of automated pixel count of two markers indicated GFAP and α-SMA co-stained well and GMT participated in the remolding of FVMs in PDR. The mean relative GFAP expression in the IVR group was significantly lower, whereas that of α-SMA was significantly higher than in controls(P<0.05). GI in the IVR group(1.10±0.10) was significantly lower than in the controls(1.21±0.12, P<0.05). CONCLUSION: IVR can reduce angiogenesis, glial activity of FVM and promote glial-fibrotic transformation by reducing MVD and promoting GMT but does not decrease the cell density in patients with PDR.

Oxidation and internal nitridation behaviors of a Ni-based superalloy Rene 65 during high-temperature homogenization

Homogenization heat treatment is a key process to remove the micro-segregation and re-dissolve the undesired phases for wrought superalloy.The oxidation behavior of the wrought superalloy during the high-temperature homogenization process,however,was rarely studied.The oxidation film evolution and growth kinetics of an as-cast superalloy Rene 65 during the homogenization were systematically studied.The oxide film consists of Cr_(2)O_(3) external oxidation layer and dendritic TiO_(2) and Al_(2)O_(3) internal oxidation layer.And the growth kinetics of the oxide film followed a parabolic law.Internal nitridation occurs during the oxidation process,and TiN is apparently formed at the tip of internal oxidation layer.The originally formed TiN can be transformed into TiO_(2) or retained with the progress of oxidation.Meanwhile,the TiN is newly formed in the deeper matrix at the new oxidation-layer tip.Thermodynamic analyses revealed that there is a competition between the oxidation and nitridation.Nitridation can occur when the partial pressure of nitrogen exceeds the threshold of nitridation and the critical partial pressure ratio of nitrogen and oxygen.

Microstructural Characteristics and Mechanical Behavior of Spark Plasma-Sintered Cu–Cr–rGO Copper Matrix Composites

Copper matrix composites were prepared through spark plasma sintering(SPS) process, mixing fixed amount of reduced graphene oxide(rGO) with the different amounts of Cr. In the sintered bulk composites, the layered rGO network and uniform Cr particles distributed in the Cu matrix. Both of mechanical blending and freeze-drying stages of the wet-mixing process obtained the Cu/Cr/rGO mixture powders, and then SPS solid-phase sintering realized the faster densification of these mixture powders. The hardness and compressive yield strength of the Cu–Cr–rGO composites depicted the higher values than those of pure Cu and single rGO-added composite, and they were gradually increased with increasing Cr. The rGO/Cr hybrid second-phases are believed to be beneficial to strengthening Cu matrix. The relevant formation and strengthening mechanisms involved in Cu–Cr–rGO composites were discussed.

Crystal Structure of 4-Hydroxyphenylpyruvate Dioxygenase in Complex with Substrate Reveals a New Starting Point for Herbicide Discovery

4-Hydroxyphenylpyruvate dioxygenase(HPPD)is a promising target for drug and pesticide discovery.Te unknown binding mode of substrate is still a big challenge for the understanding of enzymatic reaction mechanism and novel HPPD inhibitor design.Herein,we determined the frst crystal structure of Arabidopsis thaliana HPPD(AtHPPD)in complex with its natural substrate(HPPA)at a resolution of 2.80˚A.Ten,combination of hybrid quantum mechanics/molecular mechanics(QM/MM)calculations confrmed that HPPA takes keto rather than enol form inside the HPPD active pocket.Subsequent site-directed mutagenesis and kinetic analysis further showed that residues(Phe424,Asn423,Glu394,Gln307,Asn282,and Ser267)played important roles in substrate binding and catalytic cycle.Structural comparison between HPPA-AtHPPD and holo-AtHPPD revealed that Gln293 underwent a remarkable rotation upon the HPPA binding and formed H-bond network of Ser267-Asn282-Gln307-Gln293,resulting in the transformation of HPPD from an inactive state to active state.Finally,taking the conformation change of Gln293 as a target,we proposed a new strategy of blocking the transformation of HPPD from inactive state to active state to design a novel inhibitor with K_(i) value of 24.10 nM towards AtHPPD.Te inhibitor has entered into industry development as the frst selective herbicide used for the weed control in sorghum feld.Te crystal structure of AtHPPD in complex with the inhibitor(2.40˚A)confrmed the rationality of the design strategy.We believe that the present work provides a new starting point for the understanding of enzymatic reaction mechanism and the design of next generation HPPD inhibitors.

Transcriptional identification of differentially expressed genes associated with division of labor in Apis cerana cerana

Workers of Apis cerana cerana undergo an in-hive nursing to outdoor foraging transition,but the genes underlying this age-related transition remain largely unknown.Here,we sequenced the head transcriptomes of its 7-day-old normal nurses,18-and 22-day-old normal foragers,7-day-old precocious foragers and 22-day-old over-aged nurses to unravel the genes associated with this transition.Mapping of the sequence reads to Apis mellifera genome showed that the three types of foragers had a greater percentage of reads from annotated exons and intergenic regions,whereas the two types of nurses had a greater percentage of reads from introns.Pair-and group-wise comparisons of the five transcriptomes revealed 59 uniquely expressed genes(18 in nurses and 41 in foragers)and 14 nurse-and 15 forager-upregulated genes.The uniquely expressed genes are usually low-abundance long noncoding RNAs,transcription factors,transcription coactivators,RNA-binding proteins,kinases or phosphatases that are involved in signaling and/or regulation,whereas the nurse-or forager-upregulated genes are often high-abundance downstream genes that directly perform the tasks of nurses or foragers.Taken together,these results suggest that the nurse-forager transition is coordinated by a social signal-triggered epigenetic shift from introns to exons/intergenic regions and the resulting transcriptional shift between the nurse-and forager-associated genes.

Rational Design and Application of an Indolium-Derived Heptamethine Cyanine with Record-Long Second Near-Infrared Emission

Heptamethine cyanine dyes,typified by indocyanine green,have been extensively employed as bioimaging indicators and theranostic agents.Significant efforts have been made to develop functional heptamethine cyanine dyes with outstanding bioimaging and theranostic utilities.In this work,we rationally designed and successfully developed a novel indolium-like heptamethine cyanine dye by installing indolium-derived polycyclic aromatic hydrocarbons on the terminal ends of a conjugated polyene backbone.This dye showed excellent photostability and showed bright fluorescent emission in the second near-infrared(NIR-Ⅱ)window with a peak at approximately 1120 nm.Such long wavelength emission prompted a superior bioimaging resolution in vivo.In particular,this NIR-Ⅱ dye had the remarkable capability of marking the blood vessels of the hindlimbs,abdomens,and brains of mice.More significantly,this dye involved a typical indolium-like heptamethine skeleton and exhibited two strong absorption bands in the 700–1300 nm NIR range,which endowed it with an intrinsic tumor-targeting capability and a high photothermal conversion efficiency(up to 68.2%),serving for the photothermal therapy of tumors under the guidance of NIR-Ⅱ fluorescence imaging.This work provides an efficient design strategy for achieving indolium-like heptamethine cyanine dyes with further NIR-Ⅱ emission.

Photochemical and electrochemical strategies in C-F bond activation and functionalization

The activation and functionalization of C-F bonds under mild conditions can serve as an important tool for organic syntheses including the modification of pharmaceuticals and agrochemicals and the synthesis of value-added chemicals.However,owing to their high energy and low activity,C-F bonds are difficult to activate.

Role of radiative and convective heat transfer during heating of an ingot product in a tubular furnace:experiment and simulation

Convective heat transfer and radiative heat transfer are two essential heat transfer modes in the heating process of steel;it is important to understand the role of them during the heating process clearly.The effects of the convective and radiative heat transfer during the heating process of a cast ingot in a tubular furnace have been studied by the designed natural and forced convection experiments and mathematical simulations.The heating time for the center of the ingot to reach the furnace temperature is decreased with the increase in furnace temperature.According to the experimental and simulation results,a model is proposed regarding the role of radiative and convective heat transfer in the heating process.At low temperature,the convective heat transfer plays a dominant role,while at high temperature,the influence of radiative heat transfer is larger.And a critical temperature exists between them.The forced convective heat transfer can enhance the influence of the convective heat transfer.The critical temperature can be shifted to higher temperatures.

Photoacoustic imaging-guided chemo-photothermal combinational therapy based on emissive Pt(Ⅱ)metallacycle-loaded biomimic melanin dots

Pt(Ⅱ)-based metallacycles,as an important family of supramolecular coordination complexes(SCCs),have exhibited excellent antitumor activity at the cell level.However,the biomedical applications of Pt(Ⅱ)-based metallacycles for animal studies are still hindered by their poor stability,non-targeted tumour,and lack of detectable feedback for evaluating therapeutic progress.Herein,we propose a strategy that introduces melanin dots as a biomedical platform to load bright-emission Pt(Ⅱ)-based metallacycles,thereby constructing a theranostic agent that enables photoacoustic imaging(PAI)-guided chemo-photothermal combinational therapy.Melanin dots act as a protective carrier to preserve the integrity of Pt(Ⅱ)-based metallacycles before uptake by tumour tissues.Meanwhile,the PAI signal from melanin dots furnishes more comprehensive information on the tumour.Moreover,the heat generated after NIR laser irradiation can not only trigger the apoptosis of tumour cells but also promote the deeper penetration of Pt(Ⅱ)-based SCCs into tumour tissue,thus enhancing the efficiency of chemotherapy.