A one‐step strategy for aliphatic poly(carbonate‐ester)s with high performance derived from CO2, propylene oxide and l‐lactide

To improve the performance of PPC, aliphatic poly(carbonate‐ester)s were prepared in one‐step strategy from the terpolymerization of CO₂, propylene oxide (PO), and l ‐lactide (L ‐LA) catalyzed by zinc glutarate. Consequently giving high‐molecular weight terpolymers (PPCLAs) in a very high yield (8450.8–9435.8 g mol^?1 of Zn). The resulting terpolymers PPCLAs were characterized by ¹H NMR, showing that PPCLAs had an almost alternating structure for the components of CO₂, PO, and L‐LA. The influence of molecular weight and L‐LA content on the properties of PPCLAs was also investigated. Differential scanning calorimetry and thermogravimetric analysis (measurements revealed that the glass transition temperature (T _g) and thermal decomposition temperature (T _d) of PPCLAs are all much higher than those of PPC and increased with increasing molecular weight and L‐LA content. Tensile tests showed that the high mechanical properties of PPCLAs are due to the introduction of L‐LA into the copolymerization of CO₂ and PO. Furthermore, PPCLA4 exhibits high degradability, and after 10 weeks, the weight loss increases up to 6.58%, which is significantly higher than that of PPC of 4.58%. Copyright © 2016 John Wiley & Sons, Ltd.     

Injectable poly(ethylene glycol) hydrogels for sustained doxorubicin release

Water‐soluble poly(ethylene glycol) derivatives with multiple “clickable” mercapto groups or double bonds were facilely synthesized in a large scale by direct polycondensation of oligo(ethylene glycol) diol with mercaptosuccinic acid or maleic acid catalyzed by scandium trifluoromethanesulfonate under mild conditions. Injectable hydrogels containing doxorubicin hydrochloride (DOX · HCl) could be rapidly formed using these poly(ethylene glycol) derivatives as precursors via in situ thiol‐ene “click” reaction under physiological conditions without light, initiator, or metal catalyst. DOX · HCl could be sustained released from the hydrogels as a result of the hindrance of the three dimensional hydrogel network on the drug molecules, which makes this kind of DOX‐loaded hydrogels a promising candidate for localized tumor chemotherapy. Copyright © 2016 John Wiley & Sons, Ltd.     

固相萃取/液相色谱-串联质谱法测定食品中二甲基黄

建立了液相色谱-串联质谱(LC-MS/MS)测定食品中二甲基黄(DMY)的分析方法。样品经乙酸乙酯提取,二甲基黄专用固相萃取小柱(ProElut DMY SPE)净化,XDB-C18色谱柱(50 mm×4.6 mm,1.8μm)分离,并以5mmol/L乙酸铵水溶液(含0.1%(v/v)甲酸)-乙腈(含0.1%(v/v)甲酸)为流动相,梯度洗脱,电喷雾正离子模式(ESI~+)电离,多反应监测模式(MRM)检测,内标法定量。结果表明,DMY在0~50μg/L范围内线性关系良好,相关系数(r~2)均大于0.999。方法的检出限(LOD,S/N3)和定量限(LOQ,S/N10)分别为2μg/kg和10μg/kg。不同食品基质中,DMY在10、20和100μg/kg的添加水平下的平均加标回收率为93.3%~98.9%,相对标准偏差为1.6%~3.9%(n=6)。该方法有效补偿了液相色谱-串联质谱检测过程中的离子化抑制效应,灵敏度和准确度高,适用于腐乳、辣椒酱、禽蛋、豆干、糖果和火腿中DMY的测定。     

超高效液相色谱-四极杆/静电场轨道阱高分辨质谱检测食品中的牛奶过敏原酪蛋白

基于超高效液相色谱-四极杆/静电场轨道阱高分辨质谱系统,建立了食品中牛奶过敏原酪蛋白的快速筛查和定量检测方法。样品经缓冲液提取后,采用5 kD超滤膜去除小分子杂质,得到蛋白质提取液。以数据依赖采集(data-dependent acquisition,DDA)方式获得全扫描质谱图,进行蛋白质定性确证,以平行反应监测(parallel reaction monitoring,PRM)技术对目标特征肽段进行定量分析。针对特征肽段,设计并合成了内标肽和内标物质,以降低基质效应和抵消处理过程中的损失。该方法应用于食品中的α-酪蛋白、β-酪蛋白和κ-酪蛋白的快速筛查和定量检测。结果表明,该方法在5~250μg/L范围内线性关系良好,定量限为0.2~5.5μg/kg,平均回收率在68.8%~104.4%之间,RSD6%。该方法可用于果汁饮料、果酱、面包、早餐谷物中牛奶过敏原酪蛋白的快速筛查和定量分析。     

全自动在线固相萃取-液相色谱-高分辨质谱法测定麦卢卡蜂蜜中的特征标志物

建立了全自动在线固相萃取-液相色谱-高分辨质谱(SPE-LC-HRMS)测定麦卢卡蜂蜜中特征标志物3,5-二甲氧基苯甲酸甲酯-4-双葡萄糖糖苷(leptosperin)的方法。以Dikma Diamonsil Plus C_(18)色谱柱(150 mm×4.6 mm,5μm)为分析柱,0.1%(v/v)甲酸水溶液-乙腈为流动相进行梯度洗脱,在电喷雾负离子、目标二级离子扫描模式下进行检测,外标法定量。结果表明,在0.5~100.0 mg/L范围内该分析物的线性关系良好,相关系数为0.999 3,方法的检出限(LOD,S/N≥3)和定量限(LOQ,S/N≥10)分别为3 mg/kg和10 mg/kg。在不同蜂蜜样品中分别添加50.0、100.0、200.0 mg/kg(洋槐蜜中添加10.0、20.0、50.0 mg/kg)特征化合物标准品进行加标回收率试验,平均回收率为82.0%~95.2%,相对标准偏差为2.7%~9.7%(n=6)。利用该方法对来自新西兰12种不同品种的95个蜂巢成熟原蜜和来自4个国家50个商品化蜂蜜进行了验证。该法快速、灵敏、准确,可为解决进口新西兰麦卢卡蜂蜜的判别难题提供技术支持。     

An improved NSGA-III algorithm based on elimination operator for many-objective optimization

Due to the low selection pressure of the Pareto-dominance relation and the ineffectivity of diversity maintenance schemes in the environmental selection, the classical Pareto-dominance based multi-objective evolutionary algorithms (MOEAs) fail to handle many-objective optimization problems. The recently presented non-dominated sorting genetic algorithm III (NSGA-III) employs the uniformly distributed reference points to significantly promote population diversity, but the convergence based on the Pareto-dominance relation could still be enhanced. For this purpose, an improved NSGA-III algorithm based on elimination operator (NSGA-III-EO) is proposed. In the proposed algorithm, the elimination operator first identifies the reference point with maximum niche count and then employs the penalty-based boundary intersection distance to rank the individuals associated with it. To this end, the selection scheme is used to remove the worse individuals rather than to select the superior individuals. The proposed NSGA-III-EO is tested on a number of well-known benchmark problems with up to fifteen objectives and shows the competitive performance compared with five state-of-the-art MOEAs. Additionally, it is also tested on constrained problems having a large number of objectives and shows good performance.     

Multifractal analysis of the divergence points of Birkhoff averages for $$\beta $$-transformations

This paper is aimed at a detailed study of the multifractal analysis of the so-called divergence points in the system of \(\beta \)-expansions. More precisely, let \(T_{\beta }\) be the \(\beta \)-transformation on [0, 1) for a general \(\beta >1\) and \(\psi :[0,1]\mapsto \mathbb {R}\) be a continuous function. Denote by \(\textsf {A}(\psi ,x)\) all the accumulation points of \(\{\frac{1}{n}\sum _{j=0}^{n-1}\psi (T^jx): n\ge 1\}\). The Hausdorff dimensions of the sets

$$\begin{aligned} \{x:\textsf {A}(\psi ,x)\supset [a,b]\},\quad \{x:\textsf {A}(\psi ,x)=[a,b]\},\quad \{x:\textsf {A}(\psi ,x)\subset [a,b]\} \end{aligned}$$

i.e., the points for which the Birkhoff averages of \(\psi \) do not exist but behave in a certain prescribed way, are determined completely for any continuous function \(\psi \).

     

橡胶基复合靶抗贯穿特性的近似分析方法

采用体积含量加权的方法确定了复合靶等效状态方程参数,采用纤维含量平方外推的方法确定了复合靶的等效强度。然后利用球腔膨胀和柱腔贯穿相结合的方法提出了一种分析计算钢球贯穿橡胶基复合靶的近似分析模型。计算方法简明、高效,而且对剩余速度和临界穿透速度等的计算结果与已有实验有良好的符合。     

B2型钽钨有序合金的声子色散关系的研究

应用改进分析型嵌入原子法模型和晶格动力学理论,计算了金属钽和钨以及B2型钽钨有序合金的原子力常数和动力学矩阵,模拟了金属钽和钨沿[ζ00]、[ζζ0]和[ζζζ]三个对称方向以及B2型钽钨有序合金沿[ζζ0]、[11ζ]、[ζζζ]和[ζ00]四个对称方向的声子色散曲线,并分析了B2型钽钨有序合金的振动特性.结果表明:金属钽和钨的声子色散曲线的模拟结果和实验值符合较好,特别在低频附近二者几乎一致;B2型钽钨有序合金中既有声频振动支又有光频振动支,光频支的振动频率均大于声频支的振动频率,且光频带和声频带之间由宽度约为0.82THz的空带隔开;在[ζζ0]对称方向上有六个独立振动模,在[11ζ]、[ζζζ]和[ζ00]对称方向上六个振动模均兼并为四个独立振动模,且各振动支的振动方向不尽相同.     

Colorimetric and visual determination of melamine by exploiting the conformational change of hemin G-quadruplex-DNAzyme

We report on the detection of trace quantities of melamine (MA) by a colorimetric method that exploits the conformational change of hemin G-quadruplex-DNAzyme. The addition of MA to hemin G-quadruplex-DNAzyme structure containing thymine bases causes the thymine in the DNAzyme to interact with MA via a stable triple H-bond and leads to a conformational change. This, in turn, affects the peroxidase-like activity of hemin which is determined colorimetrically at 450 nm by adding 3,3’,5,5’-tetramethylbenzidine and hydrogen peroxide. The method was applied to the colorimetric determination of MA over a wide range of concentrations (0.2 to 24 μM) with a detection limit of 80 nM. The effect also can be detected with bare eyes. The method was successfully applied to the determination of MA in spiked milk powder.