利用改进型衍射理论对直边衍射效应的解释

利用改进型衍射理论MTPO（Modified Theory of Physics Optics）对直边衍射现象做出了解释．用数值模拟方法得出了直边衍射场强随衍射角度的变化曲线，并与广泛采用的菲涅耳近似衍射方法结果进行比较，发现在很大的角度空间上，二者所得出的衍射场强与精确解吻合较好．但在入射波的几何传播方向上，即边缘上的衍射场强分布，MTPO方法则具有更高的准确度．     

悬浮液进样-原子吸收光谱法测定核桃粉中的钙、铁和锌

采用悬浮液进样技术应用于原子吸收光谱法,测定了核桃粉中的钙、铁和锌的含量.将核桃粉悬浮于琼脂胶体中制成悬浮液,直接喷入空气-乙炔火焰,用标准加入法测定,将实验结果与灰化法结果进行了比较,经t检验,在显著性水平a=0.05时两种方法无显著性差异,相对标准偏差≤6.1%,结果吻合较好.该方法简便,快速,灵敏度高,准确性好.     

Thieno[3,4‐b]pyrazine‐based low bandgap photovoltaic copolymers: Turning the properties by different aza‐heteroaromatic donors

A new series of low‐bandgap copolymers based on electron‐accepting thieno[3,4‐b]pyrazine (TPZ) and different electron‐donating aza‐heteroaromatic units, such as carbazole (CZ), dithieno[3,2‐b:2′,3′‐d]pyrrole (TPR) and dithieno[3,2‐b:2′,3′‐e]pyridine (TPY), have been synthesized by Suzuki or Stille coupling polymerization. The resulting copolymers were characterized by NMR, elemental analysis, gel permeation chromatography, thermogravimetric analysis, and differential scanning calorimetry. UV–vis absorption and cyclic voltammetry measurements show that TPZ‐based copolymer with TPR has the best absorption due to the strongest intramolecular charge transfer effect and smallest bandgap. The basic electronic structure of D‐A model compounds of these copolymers were also studied by density functional theory (DFT) calculations. The conclusion of calculation agreed also well with the experimental results. The polymer solar cells (PSCs) based on these copolymers were fabricated with a typical structure of ITO/PEDOT:PSS/copolymer:PC₇₁BM/Ca/Al under the illumination of AM 1.5G, 100 mW cm^?2. The performance results showed that TPZ‐based copolymer with TPR donor segments showed highest efficiency of 1.55% due to enhanced short‐circuit current density. The present results indicate that good electronic, optical, and photovoltaic properties of TPZ‐based copolymers can be achieved by just fine‐tuning the structures of aza‐heteroaromatic donor segments for their application in PSCs. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Oleanane‐Type Triterpenoids from the Endophytic Fungus Pestalotiopsis clavispora Isolated from the Chinese Mangrove Plant Bruguiera sexangula

Three new triterpenoid derivatives, named (15α)‐15‐hydroxysoyasapogenol B ( 1 ), (7β,15α)‐7,15‐dihydroxysoyasapogenol B ( 2 ), and (7β)‐7,29‐dihydroxysoyasapogenol B ( 3 ), were isolated from cultures of the plant endophytic fungus Pestalotiopsis clavispora. Their structures and relative configurations were elucidated by extensive spectroscopic analysis and X‐ray crystallography.     

Large enhancements in gelation behavior of wheat gliadins by incorporation of low concentrations of methylcellulose

Influence of non-gelling methylcellulose(MC)on gelation behavior of wheat gliadins in 13 wt%alkaline propanol/water(50:50, v/v)solution was investigated using dynamic rheological time sweep test.Increasing MC concentration(C_(MC))up to C_(MC)=1wt% caused a significant reduction in gelation time(t_(gel))of the solution and an increase in loss tangent(tanδ)value of the resultant gel at T<30℃.     

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.