微波消解-电感耦合等离子质谱法同时测定烟用香精中24种微量元素

采用微波消解处理样品,电感耦合等离子体质谱检测的方法同时测定了8种烟用香精样品中的24种微量元素。方法以锗和钍作为内标消除基体效应,采用灌木枝叶标准物质(GBW07602)对方法进行验证。结果表明:24种微量元素的检测限在0.004～1.078ng/mL之间;相对标准偏差均小于10%;回收率在84.46%～108.85%之间。该法操作简单、分析快速、灵敏度高、准确度好,适合批量香精样品中微量元素的检测。     

重金属污泥高温处理磨细粉对改性硫氧镁水泥基材料性能的影响

为探究重金属污泥高值资源化利用途径, 研究了含重金属污泥高温处理渣料磨细粉(简称磨细粉)对改性硫氧镁(MMOS)水泥基材料的工作性能、力学性能、早期自由收缩变形及其重金属浸出行为的影响. 结果表明: 随着磨细粉掺量的增加, MMOS水泥基材料的净浆流动度呈现逐渐增大趋势; 早期(3d)力学性能则呈现明显的降低趋势, 90d后磨细粉掺量对MMOS水泥基材料的力学性能的影响程度降低; 磨细粉可以显著降低MMOS水泥基材料早期的自由收缩变形值, 其中含10%磨细粉的MMOS水泥基材料早期的自由收缩变形比未掺加磨细粉MMOS水泥基材料的自由收缩变形值降低了57.1%. 微观分析结果表明: 掺加30%磨细粉后MMOS水泥基材料中水化产物5Mg(OH)2?MgSO4?7H2O(517相)的相对含量降低, MMOS水泥基材料硬化体的平均孔径提高了31.0%, 表明磨细粉降低了MMOS水泥基材料的力学性能. 当磨细粉掺量增加至40%时MMOS水泥基材料硬化体中重金属Ni、Cr、Zn和Cu的浸出浓度指标均能满足GB 30760-2014的浸出要求.     

On structural decompositions of finite frames

A frame in an n-dimensional Hilbert space H _n is a possibly redundant collection of vectors {f _i } _i∈I that span the space. A tight frame is a generalization of an orthonormal basis. A frame {f _i } _i∈I is said to be scalable if there exist nonnegative scalars {c _i } _i∈I such that {c _i f _i } _i∈I is a tight frame. In this paper we study the combinatorial structure of frames and their decomposition into tight or scalable subsets by using partially-ordered sets (posets). We define the factor poset of a frame {f _i } _i∈I to be a collection of subsets of I ordered by inclusion so that nonempty J?I is in the factor poset iff {f _j } _j∈J is a tight frame for H _n . We study various properties of factor posets and address the inverse factor poset problem, which inquires when there exists a frame whose factor poset is some given poset P. We then turn our attention to scalable frames and present partial results regarding when a frame can be scaled to have a given factor poset; in doing so we present a bridge between erasure resilience (as studied via prime tight frames) and scalability.     

Spectral force analysis using atomic force microscopy reveals the importance of surface heterogeneity in bacterial and colloid adhesion to engineered surfaces

Coatings developed to reduce biofouling of engineered surfaces do not always perform as expected based on their native properties. One reason is that a relatively small number of highly adhesive sites, or the heterogeneity of the coated surface, may control the overall response of the system to initial bacterial deposition. It is shown here using an approach we call spectral force analysis (SFA), based on force volume imaging of the surface with atomic force microscopy, that the behavior of surfaces and coatings can be better understood relative to bacterial adhesion. The application of vapor deposited TiO₂ metal oxide increased bacterial and colloid adhesion, but coating the surface with silica oxide reduced adhesion in a manner consistent with SFA based on analysis of the “stickiest” sites. Application of a TiO₂-based paint to a surface produced a relatively non-fouling surface. Addition of a hydrophilic layer coating to this surface should have decreased fouling. However, it was observed that this coating actually increased fouling. Using SFA it was shown that the reason for the increased adhesion of bacteria and particles to the hydrophilic layer was that the surface produced by this coating was highly heterogeneous, resulting in a small number of sites that created a stickier surface. These results show that while it is important to manufacture surfaces with coatings that are relatively non-adhesive to bacteria, it is also essential that these coatings have a highly uniform surface chemistry.     

Electrostatic charging due to separation of ions at interfaces: contact electrification of ionic electrets

This Review discusses ionic electrets: their preparation, their mechanisms of formation, tools for their characterization, and their applications. An electret is a material that has a permanent, macroscopic electric field at its surface; this field can arise from a net orientation of polar groups in the material, or from a net, macroscopic electrostatic charge on the material. An ionic electret is a material that has a net electrostatic charge due to a difference in the number of cationic and anionic charges in the material. Any material that has ions at its surface, or accessible in its interior, has the potential to become an ionic electret. When such a material is brought into contact with some other material, ions can transfer between them. If the anions and cations have different propensities to transfer, the unequal transfer of these ions can result in a net transfer of charge between the two materials. This Review focuses on the experimental evidence and theoretical models for the formation of ionic electrets through this ion-transfer mechanism, and proposes--as a still-unproved hypothesis--that this ion-transfer mechanism may also explain the ubiquitous contact electrification ("static electricity") of materials, such as organic polymers, that do not explicitly have ions at their surface.     

碳纳米管宏观条带的原位制备

采用化学气相沉积法(CVD),以二甲苯为碳源,二茂铁为催化剂,在涂有SiO₂薄膜的不锈钢基底上,原位制备出了碳纳米管宏观条带。使用扫描电子显微镜(SEM)、透射电子显微镜(TEM)和拉曼光谱(Raman)对样品形貌和结构进行了表征。结果显示：合成的碳纳米管条带宽度为20～100 μm,厚度10～30 μm,长度可达6 mm;条带由大量多壁碳纳米管沿轴向密实排列组成。对其形成机制进行了初步探讨。     

Ti/Ni过渡层对WS2薄膜摩擦学性能影响

采用射频溅射法,通过预先制备Ti和Ni 2种过渡层的工艺在3Cr13马氏体不锈钢基片上制备了硫化钨薄膜,通过与无过渡层的射频溅射WS2薄膜对比,研究了2种过渡层对薄膜性能的影响.3种样品的物相分析,表面形貌观察,微区化学成分测定,膜基结合力和薄膜摩擦系数测试等结果表明,Ti过渡层对硫化钨薄膜结构和S/W原子比没有明显的影响,对膜层的摩擦系数影响也不大,但薄膜耐磨性有所提高.而Ni过渡层虽对S/W原子比无明显影响,但却明显地提高薄膜Ⅱ型织构(基面取向)的强度,从而降低了薄膜的摩擦系数,提高了薄膜耐磨性.     

Density Functional Theory Guided Investigation of Ligand-Induced Neptunyl-Neptunyl Interactions

Actinyl-actinyl interactions are particularly prevalent for the pentavalent neptunyl cation (Np(V)O₂)⁺ where these interactions appear either as a T - or D -shape (diamond-shape). T -shaped interactions have been previously identified in high concentration Np(V) solutions containing simple anions (NO₃⁻, ClO₄⁻, Cl⁻) whereas D -shaped have only been isolated in the solid-state in the presence of carboxylate ligands. In this study, Density Functional Theory (DFT) calculations were paired with Raman spectroscopy to evaluate the formation of D -shaped interactions in the presence of aliphatic (R=H (formate), CH₃ (acetate), CH₂CH₃ (propionate)) and aromatic (R=C₆H₅ (benzoate), C₆H₄OH (4-hydroxybenzoate), C₅H₄N (isonicotinate)) carboxylate ligands. DFT studies indicate that the ΔG to form hydrated T - and D -shaped forms are not spontaneous but become so with the addition of the carboxylate ligands. Raman spectra of the Np(V) carboxylate solutions contained vibrational modes associated with the D -shaped interactions, but spectral changes observed over time indicate a dynamic system. Crystallization experiments from the Np(V) carboxylate systems confirmed the presence of D- shaped dimers for the aromatic carboxylates, suggesting that the choice of the anion in solution favors actinyl-actinyl interactions even at low concentrations (≤20 mM) of Np(V).