高度有序的二氧化钛纳米管阵列的制备及其光催化活性的研究

采用电化学阳极氧化法在钛表面构筑了一种结构有序、微米级的TiO₂纳米管阵列膜层. 考察了制备电压、氧化时间、溶液搅拌等实验参数对TiO₂纳米管阵列形貌和尺寸的影响. 应用SEM和XRD对膜层的形貌和晶型进行了分析和表征, 并通过TiO₂纳米管阵列膜对甲基橙的光催化降解, 研究了TiO₂纳米管阵列膜层结构与光催化活性的关系. 结果表明: 阳极电压和溶液搅拌对制备TiO₂纳米管阵列的结构起到关键的作用. 控制20 V电压制备的TiO₂纳米管阵列膜, 管长达2.6～3.3 μm, 经500 ℃热处理后具有最高的光催化活性, 其光催化性能明显优于一般的TiO₂纳米颗粒膜.     

Catalytic defects at molybdenum disulfide “edge” planes

Chemical and physical studies of molybdenum disulfide show that the extreme anisotropy which dominates the bulk properties of this layered compound is also very important in the understanding of surface properties. We observe that the basal surfaces in single crystals are chemically and optically inert. The edge surfaces are highly reactive to both oxygen and metallic impurities. Photoemission spectroscopy and optical absorption show that the edge surfaces have electronic states within the forbidden gap. The density of these surface defects is correlated with the hydrodesulfurization catalytic activity.     

Parallel nested dissection for path algebra computations

This paper extends the authors' parallel nested dissection algorithm of [13] originally devised for solving sparse linear systems. We present a class of new applications of the nested dissection method, this time to path algebra computations (in both cases of single source and all pair paths), where the path algebra problem is defined by a symmetric matrix A whose associated graph G with n vertices is planar. We substantially improve the known algorithms for path algebra problems of that general class; this has further applications to maximum flow and minimum cut problems in an undirected planar network and to the feasibility testing of a multicommodity flow in a planar network.     

Efficient Synthesis of p-Hydroxyphenyl Ethanol from Hydrogenation of Methyl p-Hydroxyphenylacetate with CNTs-promoted Cu-Zr Catalyst

Hydrogenation of methyl p-hydroxyphenylacetate has been used for the synthesis of p-hydroxyphenyl ethanol. The reaction was catalyzed by Cu_iZr_j-x%(mass fraction) carbon nanotubes(CNTs) catalysts. Incorporation of a minor amount of CNTs into Cu_iZr_j oxide can visibly increase the catalytic activity for the synthesis of p-hydroxyphenyl ethanol. The yield of p-hydroxyphenyl ethanol reaches 94.2% over a co-precipitated catalyst of Cu₃Zr₁ oxide with 11.0%CNTs. Its catalytic activity shows no obvious decrease after three cycles. This is much better than the CNT-free co-precipitated catalyst with a good yield of 81.1%, Cu₃Zr₁-0%CNTs.     

Catalytic behavior of some copper(II) complexes with mixed ligands in the decomposition of hydrogen peroxide

A comparative study of the catalyzed decomposition of hydrogen peroxide using the following copper(II) complex salts, Cu(bipy)(S-threo)Cl · 3H₂O, Cu(phen)(S-threo)Cl · 2H₂O, Cu(bipy)(S-prol)Cl · 2H₂O and Cu(phen)(S-prol)Cl · 2H₂O has been made. Kinetic parameters were experimentally determined by the polarographic method at 25°C, pH 7.7 and constant ionic strength (μ = 0.1 M NaNO₃). The catalytic behavior of the chelate with 2,2′-bipyridine and S-prolinate was also studied at pH 6.5 and 8.5. The reactivity follows the sequence: [Cu(bipy)S-prol] > [Cu(phen)S-prol] > [Cu(bipy)S-threo] > [Cu(phen)S-threo]. Activation energies are very similar to each other. The pH-dependent exchange of the amino acid ligand with hydrogen peroxide seems to be a critical factor in the reaction pathway. Several reaction mechanisms are proposed.     

金乌贼脑和视神经节蛋白质组比较分析

采用双向凝胶电泳(2D-PAGE)技术优化分离金乌贼的脑及视神经节全蛋白质, 并选用肽质量指纹谱(Peptide mass fingerprinting, PMF)技术和数据库检索方法对2D-PAGE图谱上的部分蛋白质斑点进行鉴定, 初步构建了金乌贼视神经节(Optic ganglion of Sepia esculenta, SEOG)和脑神经节(Cerebral ganglion of Sepia esculenta, SECG)部分分子解剖图谱. 用Melanie 4 Trial软件分析脑神经节和视神经节蛋白质斑点总数量分别为682和594个, 其中SECG蛋白质斑点数量明显多于SEOG. 在脑神经节和视神经节中均发现了线粒体苹果酸脱氢酶前体(Mitochondrial malate dehydrogenase precursor, pre-MDH)及可溶性NSF连接蛋白(SNAP-type proteins). 此外, 延长因子(Elongation factor G)、微管蛋白(Tubulin)和肌动蛋白(Actin)等蛋白质也具有高匹配率. 已鉴定的蛋白质, 多数归属于假定蛋白和结构蛋白类.     

Biosurfactants: Opportunities for the development of a sustainable future

Changes in the environment in recent years have led to the examination of the role and influence human activities on it. Attempts to quantify the impact of these activities by developing standardized modeling frameworks through life cycle sustainability assessment is one such approach in the context of sustainability seeking to measure the impact of human interventions from a holistic perspective that includes economic, social, and environmental dimensions. Sustainable alternatives to synthetic products are always keenly sought after. Biosurfactants are emerging as suitable alternatives to the predominant less sustainable petroleum-derived counterparts. Several factors surrounding their production, distribution, and end-use, however, still needs to be considered before conclusively confirming their sustainability. Though data are still limited in that subject matter, research showing their impact on some sustainability indicators is highlighted. This review discusses the potential of biosurfactants as sustainable products in the context of social, economic, and environmental aspects.     

Dynamic Variation of Excitonic Coupling in Excited Bilayer Graphene Quantum Dots?

The intermolecular interaction determines the photophysical properties of the organic aggregates, which are critical to the performance of organic photovoltaics. Here, excitonic coupling, an important intermolecular interaction in organic aggregates, between the π-stacking graphene quantum dots is studied by using transient absorption spectroscopy. We find that the spectral evolution of the ground state bleach arises from the dynamic variation of the excitonic coupling in the excited π-stacks. According to the spectral simulations, we demonstrate that the kinetics of the vibronic peak can be exploited as a probe to measure the dynamics of excitonic coupling in the excited π-stacks.     

Planar Tetracoordinate Silicon in Organic Molecules As Carbenoid-Type Amphoteric Centers: A Computational Study

Designing and synthesizing a stable compound with a planar tetracoordinate silicon (ptSi) center is a challenging goal for chemists. Here, a series of potential aromatic ptSi compounds composed of four conjugated rings shared by a centrally embedded Si atom are theoretically designed and computationally verified. Both Born–Oppenheimer molecular dynamics (BOMD) simulations and potential energy surface scannings verify the high stability and likely existence of these compounds, particularly Si-16-5555 (SiN₄C₈H₈) with 16 π electrons, under standard ambient temperature and pressure. Notably, the Hückel aromaticity rule, which works well for single rings, is inconsistent with the high stability of Si-16-5555 where the 16 p electrons are spread over four five-membered rings fused together. Bonding analyses show that the strong electron donation from the peripheral 12-membered conjugated ring with 16 π electrons to the vacant central atomic orbital Si 3p_z leads to the stabilization for both the ptSi coordination and planar aromaticity. The partial occupation of Si 3p_z results in the peculiar carbenoid-type behaviors for the amphoteric center. By modulating the electron density on the ring with substituent groups, we can regulate the nucleophilic and electrophilic properties of the central Si.     

On the regularization of feature fusion and mapping for fast MR multi-contrast imaging via iterative networks

Multi-contrast (MC) Magnetic Resonance Imaging (MRI) of the same patient usually requires long scanning times, despite the images sharing redundant information. In this work, we propose a new iterative network that utilizes the sharable information among MC images for MRI acceleration. The proposed network has reinforced data fidelity control and anatomy guidance through an iterative optimization procedure of Gradient Descent, leading to reduced uncertainties and improved reconstruction results. Through a convolutional network, the new method incorporates a learnable regularization unit that is capable of extracting, fusing, and mapping shareable information among different contrasts. Specifically, a dilated inception block is proposed to promote multi-scale feature extractions and increase the receptive field diversity for contextual information incorporation. Lastly, an optimal MC information feeding protocol is built through the design of a complementary feature extractor block. Comprehensive experiments demonstrated the superiority of the proposed network, both qualitatively and quantitatively.