API X52管线钢与Corus RQT 701超高强钢的焊接工艺

针对超高强钢在机械行业的广泛使用,焊接接头易出现淬硬脆化、裂纹等缺陷的情况,采用焊条电弧焊(SMAW)和药芯气体保护焊(FCAW-GS)组合的焊接方法,对API X52管线钢与Corus RQT 701超高强钢的焊接进行了工艺试验,并进行常规力学性能试验。结果表明,通过合理匹配焊接工艺参数,严格控制低热输入量及层间温度,实现了小熔合比的异种钢焊接,且焊接接头具有良好的力学性能,达到了标准和规格书的要求;异种高强钢焊接,采用SMAW打底焊接和FCAWGS填充并盖面的方法,焊接效率较单纯采用焊条电弧焊工艺提高2倍以上。     

TC18钛合金在热变形过程中的组织不均匀现象

揭示了Ti-5Al-5Mo-5V-1Fe-1Cr合金在等温压缩过程中出现的组织不均匀现象。首先使用真空自耗炉制备出合金铸锭,而后进行热加工和热处理,使用热处理后的材料车削成圆柱形试样进行等温压缩试验,试样端面没有进行打磨、抛光处理,结果出现了严重的组织不均匀,在试样内部发现了轴对称分布的局部大变形区,这将增加材料受力时起裂的几率。并就该组织现象展开了研究。     

MULTICOMPONENT ADSORPTION EQUILIBRIUM OF GASES IN ZEOLITE: EFFECT OF PORE SIZE DISTRIBUTION

The effect of pore size distribution of zeolite on the multicomponent adsorption equilibrium is studied. All species compete locally for a given pore and this can be described by the extended multicomponent Langmuir isotherm. The size exclusion effect is taken into account in the competition of different species for a given pore so large molecules have less degree of accessing available pores. The pore size is related to the adsorbate-adsorbent interaction energy by the Lennard-Jones potential. The isotherm parameters extracted from single-component data fitting are used to predict multicomponent adsorption equilibrium. When validated with binary experimental data of CO₂, H₂S and propane in H-mordenite, collected by Talu and Zwiebel (1986), this model provides better results than a previously proposed heterogeneous model based on a uniform energy distribution and a local IAST (Hu and Do, 1995).     

Boson peak and structural heterogeneity in ternary SiO2-Al2O3-B2O3 glasses

We use low-temperature heat capacity, low-frequency Raman scattering, and THz time domain spectroscopy in order to scale the vibrational density of states and the Boson peak in SiO₂-Al₂O₃-B₂O₃ Yb-laser host glasses. When substituting B₂O₃ for SiO₂ at constant Al₂O₃ dopant level, we find an optimal value for the ratio of B/Al in terms of mixture stability, at which the excess in the electron donor capability of Al₂O₃ (relative to the SiO₂ backbone) is compensated by the more acidic B₂O₃. At this composition, Al₂O₃ plays a mediating role in the structure of aluminoborosilicate glasses, facilitating dissolution of Yb₂O₃ and admixture of B₂O₃ into the SiO₂ network.     

Inhibiting effect of heterogeneous cations aggregation enhanced by oxygen deficiency on glass formation of BaTi2O5 melts

Although remarkable development of titanate-based glasses has been achieved, challenge remains to elucidate the correlation between structure and glass-forming properties in these systems due to their complex structure that is inconsistent with the classic Zachariasen's model. In this work, we aim to correlate the structural evolution of titanate melts to their glass-forming ability (GFA). The prototypical material barium dititanate (BaTi₂O₅, BT2) melts with different GFA were rendered by controlled melting atmospheres, and the corresponding structural changes were determined using in situ high-energy synchrotron X-ray diffraction combined with empirical potential structure refinement and ab initio molecular dynamics. The results show that BT2 melt in reducing atmosphere shows poor GFA but that in oxidizing atmosphere presents good GFA. Structural analysis demonstrates the mean coordination number of [TiO_m] polyhedra is analogous in the melt under two different atmospheres but an enhanced heterogeneous cations aggregation takes place in the melt under reducing atmosphere, which is closely related to oxygen-deficiencies. Furthermore, we reveal that the enhanced heterogeneous cations aggregation promotes crystallization (and therefore hinders glass formation) through disordering the distribution of [TiO_m] and [BaO_n] polyhedra, changing the connectivity between these polyhedra, creating more crystal-like Ti-Ti clusters, and decreasing topological disorder of BT2 melt. Our work provides a new viewpoint to understand the GFA of titanates melt from structural heterogeneity beyond the previous perspectives that only focus on [TiO_m] polyhedra.     

Study of filtered interphase heat transfer using highly resolved CFD–DEM simulations

Accurately predicting the complex inhomogeneous heat transfer behavior in gas–solid fluidized beds is of fundamental importance. In this work, we constitute an enhanced filtered interphase heat transfer coefficient (IHTC) closure by systematically filtering the dataset from highly resolved three-dimensional (3D) computational fluid dynamics–discrete element model simulations. Particularly, effects of several potential filtered variable markers on filtered IHTC predictions are examined by statistical analysis. We reveal the formulated filtered IHTC correction closure manifests a systematic dependence on filtered interphase temperature difference as an additional marker. The proposed closure shows good agreement with the filtered fine-grid simulation data in an a priori analysis. Moreover, the difference of filtered IHTC corrections deduced from 3D Euler–Euler and Euler–Lagrange simulations is quantified. Finally, the comparative analysis between our proposed filtered IHTC formulation and those in literature is implemented. This work holds a potential to facilitate the development of thermal gas–solid flow modeling.     

Effects of the Anti-Tumorigenic Agent AT101 on Human Glioblastoma Cells in the Microenvironmental Glioma Stem Cell Niche

Glioblastoma (GBM) is a barely treatable disease due to its profound chemoresistance. A distinct inter- and intratumoral heterogeneity reflected by specialized microenvironmental niches and different tumor cell subpopulations allows GBMs to evade therapy regimens. Thus, there is an urgent need to develop alternative treatment strategies. A promising candidate for the treatment of GBMs is AT101, the R(-) enantiomer of gossypol. The present study evaluates the effects of AT101, alone or in combination with temozolomide (TMZ), in a microenvironmental glioma stem cell niche model of two GBM cell lines (U251MG and U87MG). AT101 was found to induce strong cytotoxic effects on U251MG and U87MG stem-like cells in comparison to the respective native cells. Moreover, a higher sensitivity against treatment with AT101 was observed upon incubation of native cells with a stem-like cell-conditioned medium. This higher sensitivity was reflected by a specific inhibitory influence on the p-p42/44 signaling pathway. Further, the expression of CXCR7 and the interleukin-6 receptor was significantly regulated upon these stimulatory conditions. Since tumor stem-like cells are known to mediate the development of tumor recurrences and were observed to strongly respond to the AT101 treatment, this might represent a promising approach to prevent the development of GBM recurrences.     

Dynamic “Molecular Portraits” of Biomembranes Drawn by Their Lateral Nanoscale Inhomogeneities

To date, it has been reliably shown that the lipid bilayer/water interface can be thoroughly characterized by a sophisticated so-called “dynamic molecular portrait”. The latter reflects a combination of time-dependent surface distributions of various physicochemical properties, inherent in both model lipid bilayers and natural multi-component cell membranes. One of the most important features of biomembranes is their mosaicity, which is expressed in the constant presence of lateral inhomogeneities, the sizes and lifetimes of which vary in a wide range—from 1 to 10³ nm and from 0.1 ns to milliseconds. In addition to the relatively well-studied macroscopic domains (so-called “rafts”), the analysis of micro- and nanoclusters (or domains) that form an instantaneous picture of the distribution of structural, dynamic, hydrophobic, electrical, etc., properties at the membrane-water interface is attracting increasing interest. This is because such nanodomains (NDs) have been proven to be crucial for the proper membrane functioning in cells. Therefore, an understanding with atomistic details the phenomena associated with NDs is required. The present mini-review describes the recent results of experimental and in silico studies of spontaneously formed NDs in lipid membranes. The main attention is paid to the methods of ND detection, characterization of their spatiotemporal parameters, the elucidation of the molecular mechanisms of their formation. Biological role of NDs in cell membranes is briefly discussed. Understanding such effects creates the basis for rational design of new prospective drugs, therapeutic approaches, and artificial membrane materials with specified properties.     

Drivers of Plant Invasion at Broad and Fine Scale in Short Temperate Streams

Riparian ecosystems have been described as highly prone to alien plant invasions; thus, disentangling the contributing factors of the invasion process is of utmost importance to conserving and managing these valuable ecosystems. In this study we examined the drivers of riparian plant invasion in 16 Cantabrian river basins (northern Spain) ranging from 100 to ca. 1050 km². A complete flora was determined for five randomly selected sites within those basins. One hundred and thirty alien plant species were found across the 80 sampling sites, representing 21% of the recorded total flora. At site scale, the level of plant invasion, measured as alien richness (AR) and relative alien richness (RAR), was assessed in relation to a set of explanatory variables by means of Generalised Linear Mixed Models. This level of invasion was influenced by environmental variables such as the thermicity index, the average riverbed width and the number of plant communities and by human‐related variables such as the distance to the nearest town and the proportion of surrounding urban land. At basin scale, industrialised river basins were more heavily invaded than non‐industrialised basins, and they both differed in their alien plant composition. Given that some of the alien species occurring in Cantabrian streams are specially abundant (Crocosmia x crocosmiiflora) and/or form very dense stands (Fallopia japonica, Paspalum distichum), future research should focus on the drivers that influence the presence and distribution of these species of special concern. Copyright © 2016 John Wiley & Sons, Ltd.     

地下水流速及介质非均质性对重非水相流体运移的影响

重非水相流体(DNAPL)在地下介质中的运移分布受多种因素影响,包括DNAPL的物化性质、泄漏速率、地下水流速和介质非均质性等。本文采用地质统计方法生成渗透率随机场刻画非均质性,运用T2VOC模拟不同流速情形下DNAPL在均质/非均质介质中的运移分布,以评估地下水流速和非均质性对DNAPL运移的影响。研究结果表明,地下水流速的增大显著促进了DNAPL的水平和垂向运移。相同流速情形下,非均质性的增强使得DNAPL污染羽分布形态及运移路径的空间变异性增强,出现明显的蓄积和绕流。当DNAPL运移的优势通道方向与流速方向相反时,水流对DNAPL水平运移的促进作用将减弱,反之,其促进作用增强。随着流速与非均质性的同时增强,水平方向上污染羽的扩散范围增大,另外水平和垂直方向上质心位置(一阶矩)及展布范围(二阶矩),污染池起始位置及其长度的空间变异离散程度增大。