质疑``复杂应力条件下脆性材料的受拉破坏准则''

对``复杂应力条件下脆性材料的受拉破坏准则'一文中所应用公式的2个例子提出讨论.     

醇存在下R,S-1,1′-2-联萘酚对映体的环糊精手性识别研究

以R,S-1,1′-2-联萘酚对映体为手性客体分子, 采用荧光探针法详细研究了各种醇对β-环糊精/(R或S)-1,1′-2-联萘酚对映体的手性包络和手性荧光猝灭等性质的影响, 结果表明, 醇的存在可显著影响R,S-1,1′-2-联萘酚对映体与β-环糊精形成包络物的包络形式和包络常数. 通过与该对映体的β-环糊精手性固定相高效液相色谱拆分法比较研究结果表明, 醇等第三客体分子可显著影响环糊精对对映体化合物的手性选择性和分离度.     

Variational Cumulant Expansion for Spin Systems on a Triangular Lattice

The variational cumulant expansion is extended to two-dimensional Potts spin models with two-body interactions defined on a triangular lattice. As a test, the Z(3),Z(4) and Z(5) Potts models are treated. The phase transition points given by this approach are in good agreement with the exact values.     

5-(4-羟基苄基)-2,4-咪唑啉二酮酯类化合物合成及生物活性

为了发现高效、低毒、低残留的农药先导化合物,模拟AdSS酶天然抑制剂的活性结构,以L-酪氨酸为起始原料,经过关环和酯化等反应合成了24个新的5-(4-羟基苄基)-2,4-咪唑啉二酮酯系列化合物6a～6x,它们的结构通过IR,1H NMR和元素分析进行了确证。化合物6m经X射线衍射测定: C18H16N2O5,Mr＝340.33,单斜晶系,空间群 P2(1)/c,a＝0.86071(17) nm,b＝1.1167(2) nm,c＝0.93826(2) nm,β＝115.10(3)°,V＝0.8166(3) nm3,Dc＝1.384 g/cm3,Z＝2,F(000)＝356,m(Mo Kα)＝0.103 mm－1,final R＝0.0359,wR＝0.0998。初步生物活性实验结果表明,在200 mg/mL浓度下,部分化合物对小麦和拟南芥的生长有一定的抑制作用,而部分化合物对玉米的生长有促进作用。     

Synthesis and herbicidal activity of 5-(4-hydroxybenzyl)-2-thioxoimidazolidin-4-one esters

A series of novel 5-(4-hydroxybenzyl)-2-thioxoimidazolidin-4-one esters were synthesized under mild conditions by the reaction of 5-(4-hydroxybenzyl)-2-thioxoimidazolidin-4-one and carboxylic acids with DCC and DMAP as the promoters. Their structures were confirmed by 1H-NMR, IR, ESI-MS and elemental analysis. The preliminary bioassy results indicated that some of compounds exhibit good herbicidal activity against Zea mays, Triticum aestivum and Arabidopsis thaliana. The further greenhouse test showed that compounds 6-16 and 6-28 have 60%, 50% and 50% efficacy against Stellaria media, Echinochloa crus-galli and Setaria viridis at 1,000 g/ha, respectively.     

Direct sulfation of bacterial cellulose with a ClSO3H/DMF complex and structure characterization of the sulfates

Bacterial cellulose (BC) is a form of cellulose synthesized by microorganisms, which has unique structure properties and differs from plant cellulose. Up to now, chemical modification of BC has not been studied widely. This paper aims to prepare sodium bacterial cellulose sulfate (SBS) in N,N‐dimethylformamide (DMF) with a ClSO₃H/DMF complex as the sulfating agent. SBSs with diverse degree of sulfation (DS, 0.04–0.86) were synthesized. The system could change from heterogeneous to homogeneous during the sulfation. Regarding to the DS, the optimal ClSO₃H amount and reaction time were 6 mol/mol anhydroglucose unit and 4 h, respectively. DS increased a little when increasing the temperature, while the yield decreased significantly. SBSs with DS > 0.24 were soluble in deionized water. Carbon nuclear magnetic resonance spectroscopy revealed that the sulfation prefers to take place in the order of C‐6 > C‐2 > C‐3. The X‐ray diffraction profiles indicated that the crystalline structure of BC was destroyed during sulfation. BC has better reactivity than microcrystalline cellulose in both sulfation and depolymerization processes. SBS is a potential biomaterial. However, BC depolymerized obviously in present sulfation, which forbids application of SBS in material. Moisture of the reaction mixture should be removed as completely as possible to guarantee efficient sulfation and decrease depolymerization. Copyright © 2013 John Wiley & Sons, Ltd.     

一代Techniwlor模型对稀有衰变t→cV的贡献

计算了一代人工色(Technicolor)模型中的赝标哥尔斯通粒子对稀有衰变t→cV(V=Z、γ、g)的贡献.与标准模型的贡献相比,这种新的贡献提高了3—4个数量级.对适当的输入参数,一代Technicolor模型对t→cV分支比的贡献最大可达:B(t→cg)～10^－6,B(t→cZ)～10^－7,B(t→cγ)～10^－5.     

Performance enhancement of blue light-emitting diodes by adjusting the p-type doped last barrier

Blue light-emitting diodes (LEDs) with different p-doping concentrations in the last barrier have been studied numerically. The energy band diagrams, carrier concentrations, internal quantum efficiency and light output power are investigated using APSYS software. The simulation results show that the LED structure with p-doping in the last barrier has a better hole-injection efficiency and confinement of electron leakage over the structure with the last undoped GaN barrier due to enhancement of the holes’ injection and the electrons’ confinement. As a result, the efficiency droop is markedly improved, and the light output power is greatly enhanced when a larger p-doping amount is centralised in the last barrier.     

Temperature‐dependent emission shift and carrier dynamics in deep ultraviolet AlGaN/AlGaN quantum wells

Radiative and nonradiative processes in deep ultraviolet (DUV) AlGaN/AlGaN multiple quantum wells (MQWs) grown by LP‐MOCVD have been studied by means of deep ultraviolet time‐integrated photoluminescence (PL) and time‐resolved photoluminescence (TRPL) spectroscopy. As the temperature is increased, the peak energy of DUV‐AlGaN/AlGaN MQWs PL emission (E_p) exhibits a similarly anti‐S‐shaped behavior (blueshift – accelerated redshift – decelerated redshift): E_p increases in the temperature range of 5.9–20 K and decreases for 20–300 K, involving an accelerated redshift for 20–150 K and an opposite decelerated redshift for 150–300 K with temperature increase. Especially at high temperature as 300 K, the slope of the E_p redshift tends towards zero. This temperature‐induced PL shift is strongly affected by the change in carrier dynamics with increasing temperature. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

水稻耐铁毒基因型筛选及边缘细胞对铁毒的反应特性

以相对耐铁的水稻品种"中优9288"和敏感品种"汕优10号"作为实验材料,研究了铁毒对水稻离体边缘细胞的影响。结果表明,随铁浓度的升高(除400μmol/LFe2 外),处理时间的延长,边缘细胞存活率下降:400μmol/L浓度铁处理时,边缘细胞存活率增加;低浓度铁能促进PME活性增长,高浓度铁则抑制PME活性。