Effect of calcium malonate on the formation of β crystalline form in isotactic poly(propylene)

Calcium malonate (Camt) is used to induce the β crystalline form in isotactic polypropylene (iPP) for the first time. The relative content of the β crystalline form (K value) increases markedly with the addition of Camt and attains the maximum value of 73.48% at 0.40% Camt. The amounts of bright and colorful β spherulites increase and the spherulitic sizes decrease with the increase in Camt contents. The tensile strength and the Izod notched impact strength of the nucleated iPP samples increase with the addition of Camt; in particular, the latter almost doubles at 0.40% Camt compared to that of the blank iPP sample. The β nucleation mechanism of Camt is analyzed by the dimensional lattice match criterion. Copyright © 2008 John Wiley & Sons, Ltd.     

Optical limiting and nonlinear absorption of excited states inmetalloporphyrin-doped sol gels

Optical limiting and upconverted luminescence have been studied in different chromophore-doped aluminosilicate gel materials and the effects of the dynamic processes from different central ions are discussed. Chromophores are metalloporphyrins of tetra-4-sulfonatophenylporphyrinato-copper(II) and tetra-4-sulfonatopfienylporphgrinato-zinc(II) (CuTPPS and ZnTPPS, respectively) which are embedded in aluminosilicate gel hosts. Photo-upconverted luminescence was observed and believed to result from the radiative recombination of the second excited singlet state. Saturated behavior of upconverted emission was found as a function of incident excitation intensity. An optical limiting phenomenon associated with reverse saturated absorption was studied. These effects are attributed to higher excited state, absorption. The observation of upconverted luminescence indicates that the upper excited state absorption occurs while nonlinear absorption is being observed. Dynamic analysis of excited state processes indicates that intersystem crossing and triplet-triplet (quartet-quartet) absorption dominates nonlinear processes and suggests that saturation absorption or reverse saturation absorption is dependent on the ratio of the effective absorption cross section for the excited states to that for the ground state. Absorption cross sections for the excited states are estimated by the data fitting to upconverted emission intensity and nonlinear absorption     

Effect of β-Nucleating Agent on the Crystallization,Mechanical Properties,and Heat Resistance of Injection-Molded Isotactic Polypropylene

Injection-molded β-isotactic polypropylene (β-iPP) was prepared with a commercial β-nucleating agent (NT-A). The effect of NT-A on the crystallization, mechanical properties, and heat resistance of β-iPP was investigated by differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), polarized light microscopy (PLM), and mechanical and heat deflection tests. DSC and WAXD analysis showed that the content of β-crystals in the nucleated iPP was higher than that of pure iPP, and the content of β-crystals of the core was higher than that of the skin. PLM observations showed that injection-molded iPP had an obvious skin-core structure. NT-A induced abundant β-crystals and resulted in small spherulites which improved the Izod notched impact strength. When the content of NT-A was 0.075wt%, the Izod notched impact strength reached a maximum, 2.6 times more than that of pure iPP. The heat distortion temperature was also improved by NT-A.     

Erasure and Error-Correction Decoding Algorithm for Spread-Spectrum Systems with Partial-Time Interference

An erasure-control decoding algorithm is discussed for frequency-hopped spread-spectrum systems operating in the presence of pulsed or partial-time interference, and some properties of the resulting error probability which are useful in designing effective decoding algorithms are derived. Based on numerical results, specific decoding algorithms which correct both erasures and errors are then presented for use with block codes employing hard decisions.     

Multiple modulator-induced syntheses,crystal structures,and luminescent properties on hippuric acid and bovine serum albumin of Ln(III) complexes with 2,2′-oxybis(benzoic acid)

Six new coordination complexes, Ln₂(2,2′-oba)₂(phen)₂(ox)(H₂O)₂ (Ln = Eu 1, Tb 2), Ln₄(2,2′-oba)₆(phen)₂ (Ln = Eu 3, Tb 4), Eu₄(2,2′-oba)₆(phen)₂(H₂O) (5), and K[Eu(2,2′-oba)₂(phen)₂] (6) [2,2′-H₂oba = 2,2′-oxybis(benzoic acid), phen = 1,10-phenanthroline, H₂ox = oxalic acid] were synthesized by hydrothermal reactions with the same compound molar ratios but different modulatory reagents (MRs). Complexes 1–5 have different 1-D chain structures and 6 shows a mononuclear structure. These complexes form diverse 3-D supramolecular networks through hydrogen bonds. The interaction between these complexes and hippuric acid (HA) or bovine serum albumin (BSA) was investigated by fluorescence spectral analysis. Interestingly, the hippuric acid could quench the luminescence of these complexes while the fluorescence of BSA could be quenched by these complexes. Results suggested that the complexes may be potential luminescent testing reagents for HA or BSA by significant fluorescence quenching of Ln³⁺ or BSA, respectively, through a static and dynamic quenching process.     

An Alternating Polymer of Two Building Blocks Based on B←N Unit:Non-fullerene Acceptor for Organic Photovoltaics

B←N coordination bond can be used to develop polymer electron acceptors for efficient all-polymer solar cells(all-PSCs). Here, we report a new alternating conjugated polymer containing two building blocks based on B←N unit. The polymer exhibits strong light absorption in the visible range, low-lying LUMO/HOMO energy levels and moderate electron mobility. The resulting all-PSC devices exhibit power conversion efficiencies of 1.50%–2.47%.     

用有限元自适网格控制结构应力分析的精度

本文涉及有限元结构应务分析精度控制的三个基本方面：１）自适应的有限元网格自动生成技术；２）有限元应力分析的误差估计：３）用单元尺寸场将误差分布用于形成新网格。