Interesting fluorescence properties of C60-centered dendritic adduct with twelve symmetrically attached pyrenes

A C60-centered dendritic adduct with 12 symmetrically attached pyrene species was synthesized and found to have relatively simple fluorescence emission kinetics, in particular, the mono-exponential decay of the significant pyrene excimer emission.     

Thermal degradation kinetics and heat properties of cellulosic cigarette paper: influence of potassium carboxylate as combustion improver

Accurate determination of the thermal properties of cellulose is of particular significance in studying the mechanism of cellulosic cigarette paper combustion. This paper probes into the influence of four kinds of potassium carboxylates on the thermal degradation kinetics and the heat properties of cigarette paper through simultaneous thermogravimetric analysis (TGA) coupled with differential scanning calorimetry (DSC) measurement under air atmosphere. Reduced mass loss and mass loss rate, and increased solid residue for samples containing four potassium salts implied that potassium carboxylates may retard the formation of levoglucosan and volatiles by inhibiting the depolymerization reaction and simultaneously accelerate char formation by catalyzing the dehydration reaction. Kinetic parameters were analyzed based on three non-isothermal models available in literature. The results indicated that three modeling methods exhibit good consistency. A global activation energy range of 106–155 kJ mol^?1 was proposed for cigarette paper with potassium carboxylates. The four potassium salts studied considerably reduced the activation energy in the following descending order: potassium 1,2,3,4-butane tetracarboxylate (PBTCA) > citrate > gluconate > ascorbate. The heat properties of cigarette paper were also determined by integrating the DSC curves. The results demonstrated that both cellulose degradation and char oxidation have strong exothermic peaks. Cigarette paper samples with potassium salts have lower exothermic cellulose degradation process and higher exothermic char oxidation process, which were further confirmed by greater differences as the amounts of salt citrate or PBTCA increased.     

Synthesis and optical properties of metal-centered dimeric fullerene macromolecules

Dimeric fullerene macromolecules were prepared via the complexation of two fullerenylated 2,2′:6′,2″-terpyridine ligands with Fe(II) and Co(II) ions. The solubility of these macromolecules in some organic solvents allowed both their structural characterization and a study of their optical properties. The electronic absorption and emission of the macromolecules in solution were evaluated; and the results indicated no meaningful ground-state and excited singlet state intramolecular charge transfer interactions. However, the laser flash photolysis results could be explained in terms of the electron transfer quenching of the excited triplet methanofullerene moiety by the center metal–ligand complex in the macromolecules. The optical limiting properties of the macromolecules in solution were also investigated in comparison with those of the ligands for an evaluation of the complexation effects.     

On the boundary value problem of elastostatics in terms of stresses

The boundary value problem of elastostatics in terms of six components of the stress consists of nine equations and three boundary conditions. In this paper, we distinguished between the possible cases and impossible cases, i.e., the problem is or is not equivalent to a boundary value problem of six equations and six boundary conditions.     

Cellulosic fiber: mechanical fibrillation-morphology-rheology relationships

Cellulose - This study aims to investigate the relationship between mechanical fibrillation, morphological properties, and rheological behavior of cellulosic fiber. Three types of cellulosic fibers...     

Physical properties and thermal behavior of reconstituted tobacco sheet with precipitated calcium carbonate added in the coating process

Addition of precipitated calcium carbonate (PCC) to cellulosic products can reduce production costs and modify their physical properties. This study investigated the effects of adding PCC on the properties of reconstituted tobacco sheet (RTS), a cellulosic product. Scanning electron microscopy (SEM) analysis showed that adding PCC to the coating could modify the surface microstructure of RTS. With increasing PCC addition, the strength and tar release per cigarette of RTS decreased. However, the filling capacity, bulk, and CO release content in the mainstream smoke reached optimal values when the proportion of PCC in the coating was 8%. Thermogravimetry (TG) and differential thermogravimetry (DTG) analysis indicated that the main thermal pyrolysis stage occurred in the range of 200–400 °C, similar to cellulosic components. The Coats–Redfern equation was used to analyze the thermal pyrolysis mechanism. The fitting results showed that, in the range of 200–280 °C, the best fit model for RTS with 4 or 8% PCC was diffusion-controlled reaction (D1) with fitting correlation coefficient (r ²) of 0.9630 and 0.9576, respectively. Meanwhile, in the range of 280–400 °C, the most reliable fitting model for RTS with 4% PCC was chemical reaction (F2) with r ² = 0.9681. One reaction model could not describe the thermal pyrolysis of RTS with 12% PCC in the main decomposition stage. The thermal kinetic parameters suggested that addition of PCC to RTS coatings could modify the thermal pyrolysis mechanism, but did not change the peak temperatures in the main thermal decomposition stage. This study demonstrates that addition of PCC to RTS coating is a promising method to improve its quality.     

Poisson比为1/2材料中球形空穴突变和球形空穴萌生的分岔问题研究

研究Ｐｏｉｓｓｏｎ比为１／２的Ｈｏｏｋｅ材料中,空穴的突变和萌生现象·求解一个球对称几何非线性弹性力学的移动边界（ｍｏｖｉｎｇｂｏｕｎｄａｒｙ）问题,空穴为球形,远离空穴处为三向均匀拉伸应力状态,在当前构形上列控制方程;在当前构形边界上列边界条件·找到了这个自由边界问题的封闭解并得到空穴半径趋于零时的叉型分岔解·计算结果显示,在位移＿载荷曲线上存在一个切分岔型分岔点（或鞍结点型分岔点、极值型分岔点）,这个分岔点说明在外力作用下空穴会发生突变,即突然“长大”;当球腔半径趋于零时,这个切分岔转化为叉型分岔（或分枝型分岔）,这个叉型分岔可以解释实心球中的空穴萌生现象     

On catastrophe and cavitation for spherical cavity

This work deals with catastrophe of a spherical cavity and cavitation of a spherical cavity for Hooke material with 1/2 Poisson's ratio. A nonlinear problem, which is the Cauchy traction problem, is solved analytically. The governing equations are written on the deformed region or on the present configuration. And the conditions are described on moving boundary. A closed form solution is found. Furthermore, a bifurcation solution in closed form is given from the trivial homogeneous solution of a solid sphere. The results indicate that there is a tangent bifurcation on the displacement-load curve for a sphere with a cavity. On the tangent bifurcation point, the cavity grows up suddenly, which is a kind of catastrophe. And there is a pitchfork bifurcation on the displacement-load curve for a solid sphere. On the pitchfork bifurcation point, there is a cavitation in the solid sphere.     

Group Invariant Solutions of the Plastic Torsion of Rod with Variable Cross Section

Based on the theory of Lie group analysis, the full plastic torsion of rod with arbitrary shaped cross sections that consists in the equilibrium equation and the non-linear Saint Venant-Mises yield criterion is studied. Full symmetry group admitted by the equilibrium equation and the yield criterion is a finitely generated Lie group with ten parameters. Several subgroups of the full symmetry group are used to generate invariants and group invariant solutions. Moreover, physical explanations of each group invariant solution are discussed by all appropriate transformations. The methodology and solution techniques used belong to the analytical realm.     

Comparative study on properties of nanocellulose derived from sustainable biomass resources

Cellulose - Nanocellulose, a unique and promising nanosized cellulose fibers extracted from renewable biomass, has gained much attention from both the scientific and industrial communities due to...