The control of paracetamol particle size and surface morphology through crystallisation in a spray dryer

The parameters governing the crystallisation of paracetamol using various conventional techniques has been extensively studied, however the factors influencing the drug crystallisation using spray drying is not as well understood. The aim of this work was to investigate the crystallisation of an active pharmaceutical ingredient through evaporative crystallisation using a spray dryer to study the physicochemical properties of the drug and to use semi-empirical equations to gain insight into the morphology and particle size of the dried powder. Paracetamol solutions were spray dried at various inlet temperatures ranging from 60 °C to 120 °C and also from a series of inlet feed solvent compositions ranging from 50/50% v/v ethanol/water to 100% ethanol and solid-state characterisation was done. The size and morphology of the dried materials were altered with a change in spray drying parameters, with an increase in inlet temperature leading to an increase in particle Sauter mean diameter (from 3.0 to 4.4 µm) and a decrease in the particle size with an increase in ethanol concentration in the feed (from 4.6 to 4.4 µm) as a result of changes in particle density and atomised droplet size. The morphology of the dried particles consisted of agglomerates of individual crystallites bound together into larger semi-spherical agglomerates with a higher tendency for particles having crystalline ridges to form at higher ethanol concentrations of the feed.     

Lewis acid-oxygen vacancy interfacial synergistic catalysis over SO42−/Ce0.84Zr0.16O2–WO3–ZrO2 for N,N-diethylation of aniline with ethanol

Herein, a new mechanism involving Lewis acid-oxygen vacancy interfacial synergistic catalysis for aniline N,N-diethylation with ethanol was proposed, and the SO₄²⁻/Ce_0.84Zr_0.16O₂–WO₃–ZrO₂ catalyst (SCWZ) with both Lewis acid sites and oxygen vacancies was synthesized by the hydrothermal method, which shows better catalytic activity than the reported solid acidic catalysts. Besides, the SO₄²⁻/ZrO₂ (SZ) and SO₄²⁻/WO₃–ZrO₂ (SWZ) catalysts were also prepared and compared with SCWZ to investigate the synergistic effect of each component. The SO₄²⁻ and WO₃ mainly generate Lewis acid by bonding with ZrO₂, which is beneficial for the fracture of the N–H bond in aniline. The Ce_0.84Zr_0.16O₂ solid solution mainly plays a vital role in generating the oxygen vacancies as the interface active species, which can participate in stripping –OH from ethanol, then the carbocation will also be released, which only needs 1.3805 kcal/mol energy, calculated by density functional theory (DFT), to be input. In comparison, the traditional reaction mechanism needs the Brønsted acidic sites to promote the protonation of ethanol, then dehydration and subsequent formation of carbocation followed, and 108.6846 kcal/mol energy needs to be input, which is far higher than that of the new mechanism. The apparent activation energy (E_a) over SCWZ was measured by experiment to be 34.09 kJ/mol, which is much lower than that of SWZ (47.10 kJ/mol) and SZ (54.37 kJ/mol), illustrating comparatively preferable kinetics for SCWZ than that of SWZ and SZ. Besides, the conversion of aniline and selectivity to N,N-diethylaniline over SCWZ reach almost 100% and 73%, respectively. The SCWZ can be renewed for 4 times without rapid deactivation, and the longevity of SCWZ is longer than that of SWZ and SZ, as the loaded SO₄²⁻ and tetragonal ZrO₂ are stabilized by Ce_0.84Zr_0.16O₂ and WO₃, respectively.     

紫金山东南矿段成矿期次、阶段浅析

通过对紫金山东南矿段铜钼(金)矿床地质矿化特征分析,指出铜钼矿化带主要赋存于花岗闪长斑岩的内外接触带,处于似斑状花岗闪长斑岩的上部,金矿化带赋存在表生氧化带的英安玢岩、隐爆角砾岩中。经过对矿石的组构特征、矿物生成顺序等特征分析,将矿床的成矿演化过程分为斑岩热液期、高硫化浅成低温热液期、表生氧化期三个主要矿化期次,进一步将斑岩热液期分为黑云母-钾长石化阶段、石英-绢云母化阶段、碳酸盐化阶段三个阶段;高硫化浅成低温热液期分为地开石化阶段、明矾石化阶段、硅化阶段三个阶段。研究结果为进一步研究矿床成因提供了依据。     

基于光纤光栅传感的低功耗小型化电网智能感知系统

文章针对监测装置现场取电难的问题,为智能电网盲区和多事态区监测提供解决方案。本研究设计并实现了一种可用于电网智能感知的光纤光栅传感系统,由多参量的光纤光栅传感器和解调仪组成,该解调仪采用可调谐激光器作激发光源,以20×70×90 mm的微型体积,实现2 W的低功耗。系统解调仪最多可容纳4通道光纤光栅传感器,重量小于500 g,分辨率为0.5 pm,精度±2 pm,测量频率可达100 Hz,光信息可通过电力通讯光缆传输,满足多数电网设备监测需求。该传感系统功耗低、体积小,可实现多参量监测,完全满足智能电网现场供电和通讯难、事态多发的监测需求。     

融合环境因素的有限空间毒气扩散危害程度分析

为探究环境因素对毒气扩散危害程度的影响,通过对比有限空间内外环境差异,了解气体在有限空间内受力情况,并以传统高斯烟羽模型为基础,考虑扩散气体与有限空间边界碰撞产生的反射作用,建立了适用于有限空间气体扩散的改进高斯烟羽模型。深度剖析有限空间气体扩散环境,挖掘气体扩散主要关联因子,构建风速、地表粗糙度对有限空间气体扩散的影响函数;参照有限空间环境特征,分别设置3种不同风速与2种不同地表粗糙度,推求6种不同环境条件下气体扩散面积,阐明风速与地表粗糙度对有限空间气体扩散的影响程度。结果表明:在单一风速条件下,风速越高,地表粗糙度越低,洞室内H2S气体滞留时间越短,洞室内气体的扩散面积越小;风速越低,地表粗糙度越高,洞室内气体的扩散面积越大。     

水平衡法与高温转化法在矿泉水氢氧稳定同位素测定中的应用

为了鉴别不同品牌矿泉水标注水源地信息真伪,对11种不同品牌饮用水的氢氧稳定同位素(δD和δ18 O)进行测定。结果表明,水平衡法(GasBench-IRMS)和高温转化法(TC/EA-IRMS)的测定结果一致性较好,两种方法测定6种不同饮用水的δD和δ18 O的平均差异分别为(0.6±1.59)‰和(0.02±0.13)‰。水平衡法需要较长的制备和测定时间,但δD和δ18 O的测定精度明显优于高温转化法。11种饮用水δD和δ18 O变化范围较大,其δD和δ18 O受不同品牌饮用水的水源地降水影响形成明显的地域性。虽然无法区分矿泉水是否由其他类别饮用水伪造,但δD和δ18 O可以为特定区域(如高海拔与沿海地区)以及产地相近的矿泉水水源地鉴别提供依据。     

Wave scattering through an orthotropic thermoelastic slab sandwiched between two isotropic elastic half-spaces

Abstract

Present study deals with the scattering of a plane wave through an orthotropic thermoelastic slab sandwiched between two elastic half-spaces. Unlike the classical theory of thermoelasticity, we have employed non-classical thermoelastic theories (LS-theory and GL-theory) to analyze the scattering of plane waves. The amplitude ratios for different waves have been computed numerically for the considered generalized theories of thermoelasticity. The effect of the slab thickness on the amplitude ratios has been shown graphically. Moreover, the amplitude ratios of different waves (i.e., reflected, transmitted, forward and backward waves) are compared for different values of slab thickness under both the LS-theory and GL-theory.     

砂土内微生物诱导碳酸钙结晶的检测方法研究

为了寻找砂土中微生物诱导碳酸钙结晶(MICP)过程的无损检测方法,采用3种粒径的砂子和两种浓度的胶结溶液进行了砂土的胶结试验,检测了砂土流出液的流量、p H值、尿素浓度和Ca2+浓度等化学指标变化情况,并对碳酸钙晶体的生成数量和分布进行了分析。试验结果显示:砂土流出液的流量和Ca2+浓度能够预测MICP过程中碳酸钙晶体的生成数量,p H值和尿素浓度能够预测MICP过程中尿素的水解程度;砂土中碳酸钙晶体的生成数量与注入的Ca2+总量呈现线性增长的关系,其线性系数可以通过砂土的粒径和胶结溶液的浓度表示,胶结后砂柱的碳酸钙分布并不均匀,小粒径的砂柱上部碳酸钙含量较高,而大粒径的砂柱下部碳酸钙含量较高。