The flipped longitudinal polarization sequence

By flipping the longitudinal magnetization with a chain of 180° pulses it is possible to effectively restore the effects of relaxation so that the same longitudinal magnetization is periodically recovered. The pulse sequence for achieving this, called Flipped LOngitudinal Polarization (FLOP), can be incorporated into any pulse sequence whenever it is desired to stop the attenuation in longitudinal magnetization caused by relaxation. We illustrate its use for fast, single-shot measurements of the longitudinal relaxation time and for three-dimensional T₁ mapping.     

基于多项式混沌的全局敏感度分析

回顾基于多项式混沌和方差分解的全局敏感度分析方法,针对高维数随机空间和高阶多项式混沌展开面临的“维数灾难”问题,采用回归法、稀疏网格积分及基于l₁优化的稀疏重构技术（即压缩感知技术）来减少非嵌入式多项式混沌方法所需的样本配置点数目.针对几个典型响应面模型（包括Ishigami函数、Sobol函数、Corner peak函数和Morris函数）进行Sobol全局敏感度指标计算,展示多项式混沌方法在基于方差分解的全局敏感度分析中的有效性.     

A modified LC-MS/MS method for determination of tetramethylpyrazine in microdialysis samples and calibration of home-made linear probes

Tetramethylpyrazine (TMP) is one of the most important active ingredients of a Chinese herb Ligusticum wallichii Franchat, which is widely used for the treatment of cardiovascular diseases. Several factors may affect TMP exposure after topical administration, resulting in large variability and demanding further elucidation of drug distribution. This paper describes a new efficient reliable LC‐MS/MS assay for the determination of TMP in dermal microdialysate, where TMP was separated on an Agilent C₁₈ column (3.5 µm, 100 mm × 2.1 mm i.d.) using a mixture of methanol, water and acetic acid (50:50:0.6, v/v/v) at a flow‐rate of 0.3 mL/min. The retention time was 1.89 min for TMP and 1.17 min for the internal standard (caffeine). Histological analysis confirmed an inflammatory response to the microdialysis probes and the presence of a collagen capsule. The membrane extraction efficiency (percentage delivered to the tissue space) for TMP was not altered through the implant lifetime. The validation and sample analysis results showed that the method is precise, accurate and well suited to support dermal microdialysis experiments. Copyright © 2012 John Wiley & Sons, Ltd.     

Thermo-kinetic Investigation of Optimum Growth Temperature of Petroleum Bacteria

The power-time curves of the growth of three strains of petroleum bacteria at different temperatures have been determined. A novel equation of a power-time curve has been proposed in this paper. The general formula to calculate the rate constant of the bacterial growth has been derived. The rate constants of the bacterial growth at different temperatures, the heat production per newly formed bacterium, the bacterial number at the end of the bacterial growth and the deceleration rate constant of the bacterial growth at 50.00°C, have been calculated. The optimum growth temperatures of the three strains have been obtained.This revised version was published online in November 2005 with corrections to the Cover Date.     

Measuring nitrate concentration in wastewaters with high chloride content

The presence of chloride ions in wastewaters in concentrations above 50 mg/L poses interference in several methods used for the measurement of nitrate-nitrogen. The aim of this study was to characterise the reliability and costs of some commonly available methods for the analysis of nitrate concentration in landfill leachate which contains high chloride levels. To investigate the effect of chloride interference, several widely used methods [ion chromatography (IC), continuous flow analysis (CFA), the German standard method (DIN), cuvette test (CUV), standard addition method (SAM) and reflectometric test (REF)] were used to measure the nitrate concentration in synthetic solutions containing varying concentrations of chloride and nitrate-nitrogen. Nitrate recoveries of the various methods were found to decrease in the following rank order: CUV (>95%) > IC (>90%) > CFA (89%) > DIN (88%) > REF (70%) > SAM (<80%). In the second part of the study, the same methods were used to measure nitrate concentrations in samples of biologically nitrified landfill leachate with and without chloride elimination. For leachate samples without chloride elimination, CUV results were well correlated (linear regression) with IC results (slope = 1.02/R² = 0.99) but to lesser extents with results obtained by CFA (0.91/0.86), DIN (0.89/0.97) and REF (0.86/0.77), and not correlated with SAM (0.74/–1.3). The incurred measurement costs per sample (in Euros) for the methods were as follows: CFA (<0.1) < DIN (0.6) < REF (0.7) < SAM (3) < CUV (3.8) < IC (15). Cuvette tests are recommended as the method of choice due to their accuracy and lower cost than IC.     

紫外分光光度法测定氯氟吡氧乙酸十二酯的研究

以甲醇作为溶剂,用紫外分光光度法测定氯氟吡氧乙酸十二酯的含量,测得氯氟吡氧乙酸十二酯对照品溶液浓度在12.0～20.0μg/mL范围之内线性关系良好,其线性方程为A=0.0815C+0.0318(R2=0.9832).平均回收率为90.86%,RSD为5.3%(n=6),结果说明方法简便、灵敏、准确,重现性好.     

气驱油油气混相过程的界面传质特性及其分子机制

油气混相过程的界面传质特性对气驱提高原油采收率技术非常重要。本文针对吉林某油田的实际油组分,采用分子动力学模拟研究了气驱油过程,分析了不同气体和驱替压力下油气两相的状态变化以及界面特性,获得不同驱替气体的最小混相压力(MMP)。结果表明,随着驱替气体压力的升高,气相的密度逐渐增大,油相膨胀密度降低,气相与油相的混合程度增强,油气两相界面厚度增加,界面张力随之减小。同时发现,驱替相中二氧化碳浓度越高,在同等气体压力下,油气界面更厚,油气混合程度更高。纯CO₂驱油得到的MMP远远小于纯N₂驱油,当这两种气体摩尔比为1 : 1混合时MMP介于两种纯气体之间,说明要达到同样的驱油效果二氧化碳需要的压力更小。最后,本文从分子微观作用力角度解释了驱替气体不同时影响油气混相程度的机制,通过分子平均作用势曲线发现油相分子对CO₂的吸引力要大于N₂分子,因此CO₂分子更容易与油相混合,驱替效果更明显。     

新型暂堵酸化用自降解暂堵剂的制备及现场应用

针对传统暂堵酸化用暂堵剂颗粒耐酸性差、降解性差和除堵工艺复杂等问题,本研究通过水溶液自由基聚合法制备了一种新型的自降解暂堵剂CQZDJ。考察了单体加量、交联剂加量、引发剂加量对CQZDJ凝胶强度和降解性的影响;通过FT-IR、TGA、SEM对其结构进行表征;并对其降解机理进行了探讨;最后在长8区块的环平81-8实验井进行了现场实践。结果表明：CQZDJ凝胶强度及降解时间与单体加量、交联剂加量、引发剂加量成正比关系,且降解时间可控;降解性实验表明CQZDJ在(1%~10%)HCl溶液、水、（2%~10%）NaCl溶液中均可在4 d内完全降解,具备良好的降解性能,对地层伤害小;SEM照片显示CQZDJ的降解过程是从初始三维网状结构逐渐崩解为层状结构,最终降解为无规则线性小分子链的过程;暂堵后现场流压上升6.3 MPa,日产油由3.87 t/d增产至5.22 t/d,实现了储层的有效改造,增产效果显著。     

从废水到新能源:光催化燃料电池的优化与应用

随着经济的飞速发展,社会对能源的需求日益扩大,对工业废水的无害化处理也提出了更高的要求。光催化燃料电池 (photocatalytic fuel cell, PFC) 在燃料电池中引入半导体光催化材料作为电极,实现了有机污染物高效降解和同步对外产电的双重功能,在废水无害化与资源化利用方面具有潜在的应用价值。半导体光催化电极是PFC系统高效运行的核心组件,增强其可见光响应和光生载流子分离是提高PFC性能的关键策略。反应器结构设计和运行参数优化也有利于改善PFC性能。本文从PFC基本原理和应用入手,综述了PFC在环境污染物资源化处理中的研究进展,并详细阐述了提高PFC的污染控制性能和产电效率的优化手段,为进一步设计高效稳定的PFC系统并实现其在水污染控制和清洁能源生产中的应用提供理论指导。     

The circular chemistry conceptual framework: A way forward to sustainability in industry 4.0

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