Evaluation of substrates for zinc negative electrode in acid PbO_2–Zn single flow batteries

An investigation was performed on the suitability of carbon materials, metallic lead and its alloys as substrates for zinc negative electrode in acid PbO2-Zn single flow batteries. The zinc deposition process was carried out in the mediumofl mol.L 1H2SO4 at room temperature. No maximum current appears on the potentiostatic current transients for the zinc deposition on lead and its alloys. With increasing overpotential, the progressive nucleation turns to be a 3D-instantaneous nucleation process for the resin-graphite composite. Hydrogen evolution on the graphite composite is effectively suppressed with the doping of a polymer resin. The hydrogen evolution reaction on the lead is relatively weak, while on the lead alloys, it becomes serious to a certain degree. Although the ex- change current density of zinc deposition and dissolution process on the graphite composite is relatively low, the zinc corrosion is weakened to a great extent. With the increase of deposition time, zinc deposits are more compact. The cyclings of zinc galvanostatic charge-discharge on the graphite composite provide more than 90% of coulombic and 80% of energy efficiencies, and exhibit superior cycling stability during the first 10 cycles.

On-line Preconcentration and Determination of Trace Metals in Water Samples by Flow Injection Combined with Flame Atomic Absorption Spectrometry via Calix[4]arene Carboxylic Acid Packed Micro-column

An adsorbent calix[4]arene carboxylic acid was employed as the adsorption material for on-line flow in jection（FI） micro-column preconcentration coupled with flame atomic absorption spectrometry（FAAS） determination of trace heavy metals（Cu, Pb, Co, Ni and Cd）. Parameters such as the pH, loading time and flow rate of sample, and the concentration, volume and flow rate of eluent were optimized. The enrichment factors are 50.0, 56.5, 11.6, 12.1 and 19.1 for Cu, Pb, Co, Ni, and Cd, respectively, and a sample throughput of 20 h–1 was obtained. The limits of de tection for Cu, Pb, Co, Ni, and Cd were in a range of 1.56―3.91 μg/L, and the relative standard deviations（RSDs） were less than 2.76%（n=7）. Furthermore, the proposed method was successfully applied to the determination of Cu, Pb, Co, Ni, and Cd in certified reference materials and various water samples.

Poly-Acrylic Acid Derivatives as Diesel Flow Improver for Paraffin-Based Daqing Diesel

Since the diesel products from paraffin-based Daqing crude oil showed low sensitivity to certain commercial diesel pour point depressant （PPDs） that resulted from the high content of paraffin, certain poly-acrylic acid derivatives （PADE） with-COOR, -COOH,-CONHR, and -COO-NH3^＋R groups by molecular design on the mechanics of diesel; PPDs were synthesized and evaluated as cold flow improver for Daqing 0^# diesel in this paper. The pure PADE was superior to the commercial PPDs and displayed a substantial ability of wax crystals dispersion. There was a synergistic effect among the PADE and T1804 and secondary amine. The synergism clearly improved the low temperature performance of Daqing diesel products and could reduce the cold filter plugging point of 0^# diesel by 6-7 ℃.

Determination of chlorogenic acid by flow injection irreversible biamperometry

A flow injection irreversible biamperometric method for the determination of chlorogenic acid is described. The proposed method is based on the electrochemical oxidation of chlorogenic acid at pretreated platinum electrode and the reduction of permanganate at another electrode to form an irreversible biamperometric detection system. Under the external potential difference （z^v） of 0 V, in the 0.05 mol/L sulfuric acid, chlorogenic acid can be determined over the range 0.8-120 mg/L with a sample measurement frequency of 80 samples/h. The detection limit is 0.18 mg/L. The proposed method exhibits the satisfactory reproducibility with a relative standard derivation （R.S.D.） of 2.21% for 19 successive determinations of 40 mg/L.

THE CLINICAL SIGNIFICANCE OF FLOW CYTOMETRIC DEOXYRIBONUCLEIC ACID MEASUREMENT OF DEPARA-FFINIZED SPECIMEN IN BLADDER TUMOR

A retrospective study of flow cytometric measurements on paraffin-embedded tumor specimens from 188 patients with bladder tumor was conducted. The results were analyzed in combination with the morphological variation of bladder tumors. It was found that the DNA ploid pottern, degree of infiltration and the multiplicity of bladder tumor were closely related with tumor recurrence, among which the DNA ploid pattern was most significant. In aneuploid bladder tumors the recurrent rate and mean annual recurrence frequency were 76.7% and 1.46, and those in the diploid bladder tumors were 18.7% and 0.33 respectively. Aneuploid was the most indicative parameter of the recurrence in bladder tumors. In addition, according to the DNA ploid pattern and DNA index (DI), the aneuploid tumors in our group were divided into 4 types, namely, tetraploid tumors, npn-euploid with DI(?)1.5, non-euploid tumors with DI>1.5 and two-aneuploid tumors. The results showed that the recurrent rate of tetraploid tumors was relatively lower and it became higher and higher in the following order: non-euploid tumors with DI(?)1.5, non-euploid tumors with DI>1.5, and two-aneuploid tumors. This indicates that there are different biological behaviors in tumors with different ploid pattern. Finally, the correlation between DNA ploid pattern and tumor metastasis was also discussed.

Flow-injection Spectrophotometric Determination of Uric Acid in Urine via Prussian Blue Reaction

A simple and sensitive flow injection（FI） spectrophotometric method was reported for the determination of uric acid based on the reduction of Fe（III）/ferricyanide in the presence of uric acid. The in situ reduced ions reacted with unreduced portion of ferricyanide/Fe（III） to form soluble Prussian blue, which was monitored at an absorption wavelength of 735 nm. The optimized conditions allow a linear calibration graph in a concentration range of 1―100 μmol/L. The relative standard deviation was in a range of 0.5%―2.5%, with a detection limit（3σ blank） of 0.3 μmol/L and a sampling frequency of 60 injection/h was obtained. The effect of common substances present in human physiological fluids on the determination of uric acid was examined. The method was applied to determining uric acid in human urine samples with the recoveries in a range of 96%―105%. The results agree well with those by spectrophotometric reference method at a confidence level of 95%. Spectrophotometric procedures for uric acid determination in clinical samples were reviewed briefly.

Cu^(2+)-Catalyzed Oscillatory Oxidation of Ascorbic Acid by O_2 Flow

A novel heterogeneous oscillator, the Cu2+-catalyzed oscillatory oxidation of ascorbic acid (Vitamin C) in aqueous solution by O-2 flow was reported. Both the potential oscillations on Pt-electrode corresponding to [Cu2+] and the absorbance oscillations at lambda =260 nm corresponding to [ascorbic acid] were observed. Oscillations in the completely homogeneous system were also observed. Effects of several factors on the oscillations were investigated.

A phosphotungstic acid coupled silica-Nafion composite membrane with significantly enhanced ion selectivity for vanadium redox flow battery

An ultra-high ion-selective Nafion composite membrane modified by phosphotungstic acid(PWA)coupled silica for vanadium redox flow battery(VRB)was constructed and prepared through solution casting.The composite membrane exhibits excellent proton conductivity and vanadium ions blocking property by incorporating the nanohybrid composed of silica and PWA into the Nafion ionomer.Simple tuning for the filling amount of the nanohybrid endows the obtained membranes preeminent vanadium barrier property including a minimum vanadium permeability of 3.13×10-7cm2min-1and a maximum proton conductivity of 0.081 S cm-1at 25°C.These indicate an ion selectivity of 2.59×105S min cm-3,which is 6.8times higher than that of recast Nafion(0.33×105S min cm-3).As a result,the VRB with the composite membrane shows superior battery performance containing a lower self-discharge rate,higher capacity retention and more robust cyclic stability compared with recast Nafion over a range of current densities from 40 to 100 m A cm-2.

Gastric Mucosal Blood Flow and Acid Secretion in Rats

The relationship between gastric mucosal blood flow (GMBF) and gastric acid secretionwere studied in rats by using secretory stimulant (pentagastrin)and inhibitor(cimetidine). GMBFwas measured by Laser Doppler flowmetry (LDF) and gastric mucosal pH determined by microglasspH electrode. GMBF increased and gastric mucosal pH decreased significantly after intravenous injec-tion of 6μg/kg of pentagastrin; nevertheless GMBF decreased and gastric mucosal pH increasedmarkedly after intravenous administration of 100mg/kg of cimetidine. This indicates that pentagastrincan increase GMBF and gastric acid secretion, and cimetidine can decrease GMBF and gastric acidsecretion in rats, proving the close relationship between GMBF and gastric acid secretion in rats.

Microwave-Assisted Facile and Rapid Esterification of Amino Acids I: Esterification of L-Leucine from Batch to Flow Processes and Scale-Up

We herein report our studies into the effects of microwave irradiation on the solvent-free esterification of L-leucine with alcohols. In the absence of solvent, microwave irradiation accelerated the reaction compared to conventional oil bath heating. Measurement of the dielectric properties under the reaction conditions revealed that the high dielectric loss factor of the reaction mixture containing L-leucine, n-butanol, and a p-toluene sulfonic acid catalyst could be attributed to the acceleration of the reaction. The depth of microwave penetration into the reaction mixture as derived from the in-situ measurement of the dielectric properties was ~13 mm, which suggested that a thinner reaction vessel was favorable for the esterification of L-leucine. In addition to the batch reaction using a desktop microwave reactor, two types of flow reaction were also performed using a desktop tubular reactor and a semi-bench-scale tubular reactor. These flow reactions also exhibited high performances, thus allowing the scale-up of this reaction system for industrial use.

便携式锂钾分析仪现场测定热泉水中的锂

锂是绿色能源和轻质合金的理想原料,作为一种重要的战略性资源而备受各国重视。热泉水中富含锂,储量可观,然而热泉水主要分布在西藏、云南等偏远地区,样品运输与实验室测试成本高、效率低,锂资源勘查急需现场分析技术的支持。热泉水一般含有较高浓度的钠、钾等元素,基体效应显著。本文利用自主研发的便携式锂钾分析仪,搭配负性滤光片,选择锂的分析谱线波长670.78nm,通过优化测量条件,建立了标准曲线法与标准加入法现场测定热泉水中锂元素的分析方法。实验结果表明,当电解质是体积分数为1.5%的盐酸,工作电流为70mA,进样流速为3.0mL/min时,锂检出限为4.07μg/L,相对标准偏差(RSD)为1.03%。对热泉水样品进行加标测试,加标回收率为81.6%~115.9%。当热泉水样品基体组成较简单时,直接采用标准曲线法即可获得较准确的分析结果;当样品基体组成较复杂或者基体浓度高时,采用标准加入法可有效地减小基体效应,获得的分析结果相对更准确。本方法适用于不同类型基体的热泉水中锂含量的分析测试。

基于裂缝闭合理论和3D打印的导流能力预测方法

酸蚀裂缝导流能力对于酸压方案的优化和产能评估具有十分重要的意义,但是在酸蚀导流能力测试过程中存在高闭合压力下岩心柱破裂情况,影响实验数据的准确性。基于以上问题,综合采用3D扫描和3D打印技术以及受压情况下裂缝闭合理论对酸蚀裂缝导流能力进行研究。首先对岩样进行酸蚀实验,通过逆向建模技术获取到酸蚀后岩心三维模型,采用SLA3D打印技术制备含粗糙壁面的三维岩心模型,对酸蚀岩心和3D打印岩心开展不同围压下渗流实验。运用离散化数据处理方法,结合赫兹接触模型和N-K模型编写导流能力预测界面,使用数值模拟方法反映闭合应力下裂缝形变情况。研究结果表明,结合真实岩体三维数字模型及SLA3D打印技术制备真实岩样,为制作复杂裂缝岩心模型提供了有效途径;酸蚀岩心和3D打印岩心导流能力实验结果、3D打印岩心实验结果和数值模拟结果误差均小于7.7%,数值模拟与碳酸盐岩心实验值的误差小于9.6%;以低闭合压力下实验和模拟结果为基础可以预测高闭合压力下裂缝导流能力,提出的研究方法为定量化表征酸蚀裂缝导流能力提供了可靠途径。

连续流动-钼酸铵分光光度法测定土壤全磷

利用硫酸-高氯酸湿法消解土壤,采用连续流动分析仪直接测定消解液磷酸根含量,建立了高通量测定土壤全磷的实验方法。方法检测限6.0 mg·kg^(-1),土壤样品的加标回收率为85%~100%。将该方法用于土壤标准物质(GBW07405、GBW07406a)全磷含量测定,结果准确,相对标准偏差(RSD)分别为3.5%、4.5%(n=3)。方法具备无需调节待测液pH值、分析速度快、消耗试剂少、结果准确可靠等优点,适用于大批量土壤全磷的测定分析。

流动注射法检测枸杞中二氧化硫残留量的方法比较及风险评估

近年来自动化检测设备以及对应方法相继涌现,本研究使用在线蒸馏-流动注射法与国标中酸碱滴定法、离子色谱法对枸杞中二氧化硫残留量进行检测比较。结果表明,三种方法的测定结果并无显著性差异。在线蒸馏-流动注射法RSD在1.5%~2.4%之间,加标回收率在86.1%~92.7%之间,因其具有自动化程度高、检测周期短的优势,更适合大批量样品的快速准确检测。用在线蒸馏-流动注射法对106批次红枸杞中的二氧化硫残留量进行检测分析,并对枸杞中的二氧化硫残留量进行暴露风险评估。结果显示,二氧化硫超标率达21.7%,枸杞中二氧化硫残留尚未对健康构成威胁。

气流场驱动喷射3D打印熔融聚乳酸微细纤维及表面浸润性调控

提出了一种高速气流场驱动喷射高效三维(3D)打印熔融聚乳酸微细纤维的方法,分析了高速气流致熔融材料剪切破碎原理,研究了打印工艺中供料气压、气流流速、打印高度等关键参数对微细纤维直径分布及结构孔隙率、截面尺寸的影响规律。并对所获得的聚乳酸微细纤维进行了表面浸润性测试。结果表明,该工艺相对于静电纺丝等微细纤维制造方法,加工效率提高10倍以上。通过控制不同的打印参数,可以有效实现纤维直径在6~18μm、孔隙率在55%~96%范围内的有效调控。通过3D打印工艺,可实现具有宏观路径可控、微观具有高孔隙率微纤维结构的制作。表面浸润性结果显示,打印微细纤维由于材料分子基团及高孔隙率综合作用,具有疏水性及粘附性特征,通过对微观局部进行亲水处理,实现了同一材料局部疏水和亲水共存结构的制作,证明了该方法表面浸润性调控的有效性。

碳酸盐岩储层酸蚀蚓孔物模实验研究进展

酸蚀蚓孔是碳酸盐岩储层基质酸化最典型、最基本的特征,其尺寸和形态对酸化效果有着重要影响,关于酸蚀蚓孔的物模研究对于碳酸盐岩储层基质酸化机理研究及现场施工设计具有重要指导意义。文章分别综述了线性流和径向流两种岩心流动实验研究的重要成果和最新进展,指出酸蚀蚓孔实时表征是线性流岩心流动实验研究的发展方向,针对渗透率、尺寸等岩心参数对酸蚀蚓孔发育的影响,应结合融合电测和示踪剂的蚓孔实时表征方法进行进一步研究。针对酸液突破岩心时孔隙体积倍数(PVBT)与岩心参数之间关系的认识,后续应进一步升级径向流岩心流动实验及表征设备,从而开展不同因素对酸蚀蚓孔发育影响的研究,重点解决酸蚀蚓孔从实验尺度升级到现场尺度问题。建议加强电测法室外模拟实验及现场应用研究,从而实现实验尺度和现场尺度酸蚀蚓孔的实时观测和表征。

可吸收阻流膜的制备及性能研究

本研究通过静电纺丝的方法制备了左旋聚乳酸(polylactic acid, PLLA)阻流膜。利用扫描电镜观察不同溶剂体系PLLA阻流膜的表面形貌;通过研究不同溶剂体系PLLA阻流膜的力学性能,并测试不同溶剂体系PLLA阻流膜的孔径大小及分布、孔隙率和静态接触角以探索可吸收阻流膜的性能。结果发现,不同溶剂体系PLLA膜的孔径均小于20μm,孔隙率均大于80%,静态接触角均大于100°;CF/AN溶剂体系PLLA膜的纤维丝表面具有多孔结构,拉伸强度和撕裂力最小;CF/DMF溶剂体系PLLA膜的纤维丝表面光滑,条干均匀,拉伸强度和撕裂力最大。CF/DMF 80/20溶剂体系PLLA膜的表面形貌和力学性能最优。该阻流膜性能有望应用于心脏封堵器阻流膜部件的研究。

基于核酸扩增-侧流层析试纸的食源性致病菌快速检测研究进展

食源性致病菌严重危害食品安全。传统的致病菌检测方法费时耗力,难以应对现代食品安全检测快速、简便的需求。分子生物学检测方法,如聚合酶链式反应法、等温核酸扩增法以及基于规律成簇间隔短回文重复序列的核酸检测技术等,已被广泛应用于食源性致病菌检测,为保障食品安全发挥了重要作用。近年来,联用核酸扩增检测技术和免疫层析技术成为食源性致病菌快速检测的研究热点。本文总结了核酸扩增和侧流层析试纸联用快速检测食源性致病菌的研究进展,重点讨论了其优缺点,并展望其未来发展方向,以期为食源性致病菌的检测和防控提供参考。

多室内环流反应器中液体循环量的试验验证与模拟

目的对液相氧化脱硫多室内环流反应器液体循环量的影响因素进行模拟和验证。方法采用CFD数值模拟,基于欧拉-欧拉多相流模型,对液相氧化脱硫多室内环流反应器进行气液两相流模拟,考查了酸气流量和空气流量对液体循环量的影响。结果利用数值模拟得到的液体循环量与利用靶式流量计测得的液体循环量误差小于10%。当酸气中H 2S体积分数不超过3%时,液体循环量(z)与酸气流量(x)、空气流量(y)之间的关系式为:z=-474.996+0.358 x+0.4873 y。结论欧拉-欧拉两相流模型能够准确地预测液相氧化脱硫反应器内液体循环量。