Direct Measurement of Ammonia in Ambient Air

Abstract

A model is proposed which addresses the factors involved in the axial light attenuation of a coated waveguide (collector/sensor) whose polymer coating has been sensitized to ammonia. The experimental results appear to corroborate the model predictions of high sensitivity (ppb) and independence of sample flow on the collector/sensor. Concentration and relative humidity both determine the slopes of the transmission curves, the latter factor of which can be reduced to a second order effect by controlling the relative humidity in the sample holder.     

Surface reduction of freely floating smectic bubbles

Elongated freely floating smectic bubbles are observed during their relaxation to equilibrium sphere shape. Unlike soap bubbles that perform weakly damped oscillations into equilibrium, this relaxation is overdamped in smectics by internal structure reorganisation processes. The bubble area reduction of centimetre-sized freely floating bubbles with few nanometres film thickness is recorded with high-speed optical imaging in microgravity and analysed quantitatively. We find a nearly linear reduction of the film area with time, driven by capillary forces and inhibited by smectic layer reorganisations. Characteristic times are in the milliseconds range, with little correlation to the film thickness and bubble size. Instead, the homogeneity of the films and the number and sizes of islands of excess layers that spontaneously form on the films appear to have crucial influence on the dynamics. The efficiency of this process sets the time scale of the film area shrinkage. We discuss the limitations of a minimalistic model that captures smectic layer reorganisation processes.     

空气稳定的氮杂蔻电子传输材料分子设计及三氮杂蔻衍生物迁移率计算

采用密度泛函理论研究氮功能化对蒄类化合物几何构型、电子结构及载流子传输性质的影响. 结果表明, 引入杂N原子可以线性降低前线轨道能级, 增强电子注入能力与空气稳定性, 且邻位掺杂较迫位和均匀掺杂调节效果更为显著. 其中, 十二氮杂蒄（12ac）具有新颖的“碗状”构型和高的电子亲和势（3.45 eV）, 是潜在的空气稳定电子传输材料构筑单元. 理论预测室温下2,6,10-三对甲氧基苯基-3,4,7,8,11,12-六甲氧基三氮杂蒄（3b）晶体的电子迁移率为0.242 cm2/V s, 预计是良好的电子传输材料, 值得进一步器件化研究.     

重度原油注空气低温氧化过程研究(英文)

低温氧化反应对现场燃烧(ISC)技术点火的成功有十分重要的影响.采用高压氧化管,研究了不同温度压力下,新疆克拉玛依重度原油的低温氧化过程.结果表明,温度和压力的变化对低温氧化反应的放热程度、持续时间以及气体产物有明显影响.适合油样低温氧化反应的温度和压力分别为150℃和10MPa.此外,采用纯组分替代原油族组分进行低温氧化实验,研究低温氧化反应对原油族组分(饱和烃、芳香烃、胶质、沥青质)含量的影响.结果表明,原油所含族组分中,芳香烃组分最易被氧化,其含量由氧化前的19.17%减少到12.38%(150℃)和9.51%(250℃).随着低温氧化过程的进行,结构复杂的族组分(胶质、沥青质)的含量明显增加.实验数据对油藏实施注空气技术,以及该技术现场实施条件的确定有十分重要的指导意义.     

Nitration of Simple Aromatics with NO2 under Air Atmosphere in the Presence of Novel Brønsted Acidic Ionic Liquids

Abstract

Aromatics nitrate with NO₂/air catalyzed by novel Brønsted acidic ionic liquids (ILs) without any volatile chlorinated organic solvent under mild conditions. The ILs employed were caprolactam based, [Caprolactam]X (X^?=pTSO^?, BSO^?, BF₄ ^?, NO₃ ^?), which are of relatively lower cost and lower toxicity than traditional imidazolium‐based ILs. The nitration reactions were carried out at ?15 to ?0°C first, then at room temperature for a longer time with a little excessive NO₂ (ca. 1.4 eqv.) for moderate yield (for toluene). The IL could be reused four times.     

Characterization of Colloidal Gas Aphron-Fluids Produced from a New Plant-Based Surfactant

Colloidal gas aphrons (CGAs) are gas bubbles with diameters ranging from 10 to 100 microns, generated by intense stirring of a surfactant solution at high speed. The surface activity and aggregation behavior of the surfactant affects the size/size distribution, stability, and other physicochemical properties of generated aphrons. Therefore, selection of a suitable surfactant is important for the generation of microbubbles with the desired properties. The goal of this articleis to investigate the potential use of a new plant-derived surfactant as an aphronizer surfactant in preparation of CGA-based drilling fluids for accomplishing desirable rheological and filtration properties. For this purpose, natural surfactant obtained from leaves of special tree, namely, Zizyphusspina Christi and used for preparation of aphron-based fluids. To achieve the research objectives, laboratory tests of suspension generation, microscopic visualization, initial yield, filtration loss, and rheological characterization with varying concentrations of surfactant and polymer were performed. Experimental results demonstrate that newly proposed biosurfactant has a great potential for application in preparation of CGA-based drilling fluids for implementation in petroleum drilling industry.      

Dynamic Behavior of Surfactants in Solution

Adsorption of various surfactants at the gas liquid interface is studied with equilibrium and dynamic surface tension measurements. The Wilhelmey plate method and maximum bubble pressure method are used for this study. Dynamic surface tension of solutions of different surfactants, sodium lauryl sulfate (SLS), polyoxyethylene glycol 4‐tert‐octyl phenyl ether (Triton X 100), poly‐oxyethylene(20) cetyl ether (Brij 58), and tetraethylene glycol mono‐n‐dodecyl ether (Brij 30), is measured at different concentrations. Adsorption of different surfactants is compared on the basis of equilibrium and dynamic behavior. Effectiveness and efficiency of different surfactants is found from equilibrium surface tension measurement. A new parameter is defined to quantify the dynamic behavior of adsorption, which gives the concentration of surfactant needed to reduce surface tension to half of its maximum reduction within a defined time available for adsorption. The dynamics of surfactant solution is quantified by using this parameter.     

Photo-induced control of bubble domains in chiral–nematic liquid crystal by a violet laser beam

The stable bubble domains generated by mixing 10% of chiral molecules into an azobenzene liquid crystal (LC)-doped nematic host can be optically controlled by a violet laser beam (415 nm). The photon-induced reversible trans–cis photo-isomerisation of azobenzene changes the helical twisting power (HTP) of LC mixtures in which the HTP of cis-azobenzene LC is lower than trans-azobenzene LC. Under the irradiation of an optical field (>20 mW cm^???2), the helical pitch distance, which is inverted proportional to the HTP, increases and the bubble domains disappear. Immediate obstruction of laser light irradiation initiates cholesteric nucleation, merging of domains and the subsequent generation of stably dispersed bubble domains.