新型含香豆素骨架水杨醛类Schiff碱衍生物的合成

在无溶剂条件下,以草酸为催化剂,间苯二酚与乙酰乙酸乙酯经Pechmann反应制得7-羟基-4-甲基香豆素(1);1经硝化、还原制得3-氨基7-羟基4-甲基香豆素(2);2与取代水杨醛经缩合反应合成了四个新的含香豆素骨架水杨醛类Schiff碱衍生物,其结构经1H NMR,IR和元素分析表征.     

Region dependent fracture resistance behavior of human dentin based on numerical simulation简

Dentin has a hierarchical structure and is composed of numerous tubules whose diameters and densities vary with the distances to the dentin-enamel junction. The unique structure determines the mechanical performance of dentin. In this study, a multiscale model, which is based on the combination of the virtual multidimensional internal bond (VMIB) theory and the Monte Carlo method, is used to simulate the fracture behavior of human dentin. Numerical simulations reveal that human dentin exhibits a graded resistance curve (R-curve). Among the three regions of dentin, superficial dentin shows the strongest resistance to crack propagation, and deep dentin has the weakest resistance. In addition, the predictions of fracture toughness of middle dentin agree well with the experimentally reported values, suggesting that the proposed model can be used to characterize the fracture behavior of human dentin comprehensively and properly.     

A corresponding-state approach to quark-cluster matter~

The state of super-dense matter is essential for us to understand the nature of pulsars; however, non-perturbative quantum chromodynamics makes it very difficult to make direct calculations of the state of cold matter at realistic baryon number densities inside compact stars. Nevertheless, from an observational point of view, it is conjectured that pulsars could be made up of quark clusters since the strong coupling between quarks might render the quarks to be grouped in clusters. In this paper, we attempt to find an equation of state of condensed quark-cluster matter in a phenomenological way. Supposing that the quark-clusters could be analogized to inert gases, we apply here the corresponding-state approach to derive the equation of state of quark-cluster matter, as was similarly demonstrated for nuclear and neutron-star matter in the 1970s. According to the calculations that we have presented, the quark-cluster stars, which are composed of quark-cluster matter, could have a high maximum mass that is consistent with observations and, in turn, further observations of pulsar mass could also place a constraint on the properties of quark-cluster matter. We will also briefly discuss the melting heat during the solid-liquid phase conversion and its related astrophysical consequences.     

Multi-stability involved mixed bursting within the coupled pre-Btzinger complex neurons

Neurons in the pre-Btzinger complex within the mammalian brain stem play important roles in the generation of respiratory rhythms. Experimental observations show that some neurons can exhibit novel mixed bursting activities. In this paper, based on a mathematical model proposed by Butera, we show how the mixed bursting activities depend on the potassium current in the coupled pre-Botzinger complex. Using fast-slow decomposition and bifurcation analysis,we investigate the dynamics of mixed bursting, as well as the mechanisms of transition between different mixed bursting patterns. We find that mixed bursting involves different bistability, and it is the transition state of two types of regular burstings.     

基于快速压缩机的2-戊酮点火过程研究

酮类燃料可作为燃料添加剂和示踪剂在内燃机中使用,然而其化学反应动力学机理仍缺乏研究。本项工作利用快速压缩机实验平台测量了2-戊酮当量比为0.5和1.0,温度890~1130 K的条件下的点火延迟时间,并结合快速采样系统利用气相色谱对2-戊酮点火延迟过程中的7种中间组分进行了定性及定量测量。类比丁酮和1-戊烯的相关反应,构建了2-戊酮的详细化学反应动力学模型,与实验数据相对比,指出了模型优化的方向,为2-戊酮的进一步研究提供了基础.     

层层自组装结合后处理制备耐磨超亲水增透纳米粒子涂层

通过层层自组装方法制备的二氧化硅纳米粒子涂层由于具有增透、超亲水的良好性质, 引起了广泛关注. 然而, 这种涂层的耐磨性往往达不到实际应用的要求. 本工作尝试通过后处理来增强涂层耐磨性. 首先采用自制二氧化硅纳米颗粒, 聚二烯丙基二甲基氯化铵(PDDA)和聚苯乙烯磺酸钠(PSS), 通过层层自组装制备了PDDA/SiO₂纳米粒子涂层, 其中(PDDA/SiO₂)₆涂层透过率最高. 随后将(PDDA/SiO₂)₆涂层依次经过124 ℃水热处理1 h和700 ℃快速淬火200 s处理, 得到同时具有超亲水性和增透性的涂层, 其中(PDDA/SiO₂)₆涂层在可见光范围内最大透过率高达99.0%. 实验表明, 这种后处理也极大地提高了涂层的耐磨性.     

冲击条件下泡沫铝的细观变形特征分析

利用SHPB-高速摄影机系统,拍摄到了泡沫铝细观结构在SHPB冲击过程中的变形,分析了试件 的应变分布及破坏模式。研究表明,泡沫铝试件在SHPB冲击过程中应变分布是不均匀的,试件两端的应变 和应变率远大于中间部分的应变和应变率,即在SHPB实验过程中泡沫铝试件不能严格满足均匀性变形假 定。因此,需要考虑对用SHPB方法测量泡沫金属动态力学性能方法进行必要的修正。     

离子交换膜对采用生物膜电极法降解五氯酚的影响

以五氯酚（PCP）为目标污染物,在隔膜式电解槽中研究了不同离子交换膜对采用生物膜电极法处理五氯酚的影响. 结果表明,阴离子交换膜有利于五氯酚在生物膜电极上的转化和中间产物的去除;与生物法和电化学法降解五氯酚相比,采用以钛基二氧化铅为阳极（Ti/PbO₂）、生物膜电极为阴极、阴离子交换膜为隔膜的电解槽处理时,五氯酚的降解效果明显优于生物法和电化学方法,经24 h处理后五氯酚的去除率和化学需氧量（COD）去除率均可达到96%（质量分数）.     

活性炭复合改善聚丙烯酸凝胶耐盐性及其溶胀机理

在活性炭(Ac)存在的情况下通过自由基溶液聚合,以过硫酸铵为引发剂,N,N′-亚甲基双丙烯酰胺为交联剂,制备了活性炭复合聚丙烯酸凝胶(PAA/AC)。 考察了凝胶在蒸馏水、生理盐水和不同pH值缓冲溶液中的平衡溶胀比以及溶胀动力学,结果表明,活性炭能有效提高凝胶的平衡溶胀比,在实验设计的pH值范围内复合凝胶具有比PAA凝胶更高的平衡溶胀比,蒸馏水和生理盐水中PAA/AC凝胶的平衡溶胀比分别可达到303和60 g/g,约为PAA凝胶的2.4倍。 讨论了凝胶的溶胀机理,结果表明,活性炭成分的介入破坏了聚合物链段之间的聚集态结构,减弱了聚合物链段之间的相互作用,提高了凝胶的溶胀能力。 示差扫描量热仪测定复合前后凝胶的玻璃化转变温度,扫描电子显微镜观察了复合前后凝胶的断面网络结构,结果进一步表明活性炭复合后聚合物链段之间的作用力减弱。     

对三氟甲基苯甲酸和2，2’-联吡啶双核铽配合物的合成、晶体结构及发光性质

羧酸可以采取螯合双齿,桥式双齿,μ3-桥式和单齿等多种形式与稀土离子配位,相应的配合物往往具有层状、无限链状和网层状聚合等特殊结构。羧酸稀土配合物在发光材料、催化和磁性材料等方面均有应用因而受到广泛关注[1-5]。其中芳香羧酸与稀土离子的配合物由于具有优异的发光性能和热稳定性一直是人们研究的热点[6-10]。文献[6-9]对稀土．