Internal plasticization of poly(vinyl) chloride using glutamic acid as a branched linker to incorporate four plasticizers per anchor point

Internal plasticization of polyvinyl chloride (PVC) using thermal azide‐alkyne Huisgen dipolar cycloaddition between azidized PVC and electron‐poor acetylenediamides incorporating a branched glutamic acid linker resulted in incorporation of four plasticizing moieties per attachment point on the polymer chain. A systematic study incorporating either alkyl or polyethylene glycol esters provided materials with varying degrees of plasticization, with depressed T_g values ranging from ?1 °C to 62 °C. Three interesting trends were observed. First, T_g values of PVC bearing various internal plasticizers were shown to decrease with increasing chain length of the plasticizing ester. Second, branched internal plasticizers bearing triethylene glycol chains had lower T_g values compared to those with similar length long‐chain alkyl groups. Finally, thermogravimetric analysis of these internally plasticized PVC samples revealed that these branched internal plasticizers bearing alkyl chains are more thermally stable than similarity branched plasticizers bearing triethylene glycol units. These internal tetra‐plasticizers were synthesized and attached to PVC‐azide in three simple synthetic steps. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 1821–1835     

岩体结构非平衡演化的有效应力原理及长期稳定性分析

开挖卸荷后的天然岩体往往处于非平衡演化状态, 将直接影响岩体工程结构的正常运行、长期稳定和安全. 时效变形和损伤演化是岩体结构非平衡演化的核心. 在赖斯(Rice) 内变量热力学理论框架下, 提出了岩体结构非平衡演化的有效应力原理, 指出有效应力是总应力中能有效驱动结构演化的部分. 将内变量率形式的非弹性应变率方程和能量耗散率函数表示为有效应力形式, 并提出非弹性余能概念. 给定具体的余能密度函数和内变量演化方程, 得到了考虑损伤的内变量黏塑性应变率方程. 通过相似材料加卸载蠕变试验结果进行参数辨识, 并分别计算了内变量率形式和有效应力形式的黏塑性应变率、能量耗散率和非弹性余能, 并对其进行比较分析. 结果表明:在过渡蠕变和稳态蠕变阶段两种形式的方程计算的黏塑性应变率几乎相等, 但在加速蠕变阶段两者相差较大;非弹性余能和能量耗散率全域积分分别从驱动结构非平衡演化的内在潜力和实际效果的角度表征了结构的非平衡演化状态和演化趋势, 能量耗散率积分更合适用于评价岩体工程结构的长期稳定性. 最后以深埋地下洞室作为工程算例, 并对其长期稳定性进行分析.     

附加压力与分散系统的稳定性

较详细地讨论了附加压力与分散系统稳定性间的关系,指出分散相附加压力的降低是分散系统趋向稳定的根本原因。以乳状液为例,附加压力降低不仅减少了液滴间相互碰撞的概率,而且更重要的是,它与液滴表面形成牢固的保护膜密切相关。只有当液滴的附加压力趋近0时,分散系统才达到热力学上稳定的状态,此时乳状液已变成了微乳状液。上述讨论也基本适用于固/液分散系统。     

Establishment and validation of an SIL-IS LC–MS/MS method for the determination of ibuprofen in human plasma and its pharmacokinetic study

In this work, we developed and validated a highly sensitive, rapid and stable LC–MS/MS method for the determination of ibuprofen in human plasma with ibuprofen-d3 as a stable isotopically labeled internal standard (SIL-IS). Human plasma samples were prepared by one-step protein precipitation. The chromatographic separation was achieved on a Poroshell 120 EC-C₁₈ (2.1 × 50 mm, 2.7 μm). Aqueous solution (containing 0.05% acetic acid and 5 mm NH₄Ac) and methanol were selected as the mobile phase with gradient elution. An electrospray ionization source was applied and operated in negative ion mode. Multiple reaction monitoring mode was used for quantification using target fragment ions m/z 205.0 → 161.1 for ibuprofen and m/z 208.0 → 164.0 for SIL-IS, respectively. This method exhibited a linear range of 0.05–36 μg/ml for ibuprofen with correlation coefficient >0.99. Mean recoveries of ibuprofen in human plasma ranged from 78.4 to 80.9%. The RSD of intra- and inter-day precision were both < 5%. The accuracy was between 88.2 and 103.67%. The matrix effect was negligible in human plasma, including lipidemia and hemolytic plasma. A simple, efficient and accurate LC–MS/MS method was successfully established and applied to a pharmacokinetic study in healthy Chinese volunteers after a single oral administration of ibuprofen granules.     

一种新型空气源高温热泵的热力学分析

本文提出了一种供热温度为80~100℃的新型空气源高温热泵循环(EIHP),该循环采用非共沸混合工质R290/R600a,利用内部自复叠技术和喷射器提升循环性能。针对EIHP循环建立了相应的热力学计算模型,并与传统热泵循环(CHP)进行了对比研究。根据计算结果,当冷凝器出口温度为100℃,蒸发器出口温度从25℃下降到-10℃时,相较于CHP循环,EIHP循环的COP提高了15%~27%,压缩机压比降低了20%~46%,容积制热量提高了22%~51%。此外,本文还研究了冷凝器出口温度,工质配比等参数对循环性能的影响情况。     

双曲冷却塔塔筒水平地震响应分析

为明确冷却塔在水平地震下的内力环向分布特征及内在原因,同时探究不同地震波时程与规范反应谱所得内力差异的原因,以某大型双曲冷却塔为例,在动力特性分析的基础上,通过反应谱方法和时程方法的水平地震响应计算及对比分析,对上述两个问题进行了研究。研究表明:由于仅侧弯振型对水平地震有贡献,而塔筒的侧弯振型和实际响应均表现为整体侧倾并伴随微弱的截面“流动”变形,这也使塔筒各内力的环向分布分别呈现正弦、余弦分布特征;其整体侧倾可类比于悬臂杆结构,塔筒子午向轴力FY、子午向弯矩MY、剪力FXY和扭矩MXY的环向分布可借助悬臂杆侧倾时截面正应力和剪应力分布来解释;而截面“流动”变形则决定了环向轴力FX和环向弯矩MX的环向分布;整体侧移显著而截面变形极小也使FY和FXY的幅值在塔筒中下部明显大于FX;由于冷却塔第1阶侧弯振型在水平地震响应中往往起绝对主导作用,因此可先对所选地震波计算得到其反应谱,对比第1阶侧弯振型周期对应的水平地震影响系数α值,即可初步推断不同时程及规范反应谱方法所得结果的大小关系。     

内埋武器高速风洞弹射投放模型试验关键技术研究

针对新一代战斗机超声速内埋武器弹射投放分离安全性问题,采用高速风洞投放实验技术研究内埋武器从开式武器舱弹射投放分离动态运动过程,风洞投放模型试验过程中采用除垂直加速度不足外,其余全部运动严格相似的轻模型相似设计方法,并针对轻模型法垂直加速度不足所导致的投放垂直位移偏离实物位移问题,采用一种简单易行的公式修正法进行补偿,试验给出了不同初始弹射投放分离条件下,内埋武器从载机投放分离后运动轨迹与姿态角随分离时间的变化规律,试验马赫数$Ma = 1.5$.研究结果表明:初始投放分离角速度对内埋武器投放分离后的运动轨迹及姿态角有较大的影响,当初始投放分离角速度$\omega _{z0}^s = 0^\circ/{\rm s}$时,内埋导弹出舱后先向下运动远离载机的流场干扰区,之后逐渐向载机方向抬升靠近并最终碰撞载机,高速风洞投放试验结果是不安全的,但经过公式修正后投放试验结果比较乐观,垂直方向运动仍然一直下降远离载机,这说明采用高速风洞投放试验得出的导弹不安全投放分离对真实载机来说不一定会出现,高速风洞投放试验结果比较保守. 当初始投放分离角速度$\omega _{z0}^s= 15^\circ/{\rm s}$和$\omega _{z0}^s = 30^\circ/{\rm s}$时,内埋导弹投放分离后运动趋势几乎一致, 均没出现向载机靠近的现象,内埋导弹具有一定的初始投放分离角速度有利于内埋武器的安全分离.      

Monovalent cation localization in DNA A-tracts with different sequences

The free solution mobilities of 26-base pair (bp) DNA oligomers containing A-tracts with and without internal ApT steps have been measured by capillary electrophoresis, using the mobility of a 26-bp random-sequence oligomer as a reference. The background electrolytes (BGEs) contained mixtures of Li⁺ and tetrapropylammonium (TPA⁺) ions, keeping the total cation concentration constant at 0.3 M. The mobility ratios equaled 1.00 in 0.3 M TPA⁺, indicating that the A-tract and reference oligomers had the same B-form conformation in this BGE. With increasing [Li⁺], the mobility ratio decreased as Li⁺ ions became localized in the A-tract minor groove, suggesting that the A-tract was now in the B* conformation. If the A-tract contained an internal ApT step and the oligomer contained less than ∼50% A + T, the mobility ratio reached a reduced plateau value that remained constant as the [Li⁺] increased to 0.3 M. However, for A-tracts without an internal ApT step and for A-tracts embedded in oligomers containing more than 50% A + T, the mobility ratios increased again at high [Li⁺], eventually reaching a plateau value of 1.00. Hence, DNA A-tracts in solution appear to exist as mixtures of the B and B* conformations, with the fractional concentration of each conformer depending on the [Li⁺], the A-tract sequence, and the total A + T content of the oligomer.     

电感耦合等离子体质谱（ICP-MS）法测定黄精中15种稀土元素及其指纹图谱绘制

为了准确测定黄精中稀土元素的含量,采用电感耦合等离子体质谱（ICP-MS）法同时测定黄精中15种稀土元素（La、Ce、Pr、Nd、Pm、Sm、Eu、Gd、Tb、Dy、Ho、Er、Tm、Yb、Lu）的含量,进而绘制稀土元素指纹图谱,以稀土元素含量的平均值构建黄精稀土元素标准指纹图谱,作为鉴定黄精中药材的参考依据。黄精样品采用微波消解法处理后,通过在线引入内标溶液,采用ICP-MS法测定15种稀土元素的含量,采用OriginPro 2021绘制稀土元素指纹图谱和进行主成分分析,采用SPSS 26.0进行聚类分析。15种稀土元素的线性关系、重复性、精密度良好,平均加标回收率在97.0%~103.3%,相对标准偏差小于等于1.74%。黄精中Ce、La、Nd含量相对较高,Ce含量为53.02～2004.58 μg/kg,位居第一。聚类分析和主成分分析结果表明,样品聚为2类,同一产地的样品能够较好地聚在一起。黄精药材中15种稀土元素的指纹图谱具有相似的分布形态,具有较强的特征性和一致性,相似度均大于0.950。该方法操作简单,准确可靠,能满足实验分析要求,可为黄精的质量控制和药理研究提供参考;建立的指纹图谱可用于黄精的鉴别。     

Si内标-X射线衍射法定量测定铁矿中Fe3O4、Fe2O3和SiO2

铁矿物相的准确定量对矿物价值评价及选冶工艺研究有重要作用,现有化学法流程复杂效率低,X射线衍射全谱拟合法可溯源性差,结果准确性难以评价和验证。本研究建立了以Si为内标,以Cu靶X射线为辐射光源,步进扫描方式获得衍射谱图,以待测相含量为横坐标,待测相与内标相峰面积比值为纵坐标建立校准曲线,以曲线对铁矿中Fe3O4、Fe2O3和SiO2物相进行定量的方法。试验对制样条件、扫描参数、内标物选择、积分方式、重叠峰校正等进行了优化选择,结果表明,试样全部通过45 μm标准筛,Si内标比例为10%,步进长度0.01°,步进时间30S,选择对Fe3O4（311）、Fe2O3（104）、SiO2（011）和Si（111）的衍射峰进行积分强度计算,可获得最优结果。在选定工作条件下,Fe3O4在1.07～100%范围内线性相关系数(R2)为0.9953,相对标准偏差(RSD)1.1%～13.2% (n=6),加标回收率99.7 %~114.8 %,检出限(LOD)4.29%;Fe2O3在1.51～100%范围内线性相关系数(R2)为0.9991,相对标准偏差(RSD)2.8%～10.6% (n=6),加标回收率87.1%~112.2%,检出限(LOD)2.56%;SiO2在0.79～29.72 %范围内线性相关系数(R2)为0.9957,相对标准偏差(RSD)3.2%～10.3% (n=6),加标回收率86.6%~98.9%,检出限(LOD)0.68%。方法易溯源、准确性易评价和验证,适合开展标准化检测和应用。