Excess Enthalpies of 2,2-Dimethylbutane + Cyclohexane + (Octane or Dodecane) at 25°C

Measurements of excess molar enthalpies at 25°C in a flow microcalorimeter,are reported for the two ternary mixtures 2,2-dimethylbutane + cyclohexane +n-octane and 2,2-dimethylbutane + cyclohexane + n-dodecane. Smoothrepresentations of the results are described and used to construct constant enthalpy contourson Roozeboom diagrams. It is shown that useful estimates of the ternary enthalpiescan be obtained from the Flory theory using only the physical properties of thecomponents and their binary mixtures.     

A variational approach for the deformation of a saturated porous solid. A second-gradient theory extending Terzaghi's effective stress principle

Summary The principle of virtual power is used to derive the equilibrium field equations of a porous solid saturated with a fluid, including second density-gradient effects; the intention is the elucidation and extension of the effective stress principle of Terzaghi and Fillunger. In the context of a first density-gradient theory for a saturated solid we interpret the porewater pressure as a Lagrange multiplier in the expression for the deformation energy, assuring that the saturation constraint is verified. We prove that this saturation pressure is distributed among the constituents according to their respective volume fraction (Delesse law) only if they are both true density-preserving. We generalize the Delesse law to the case of compressible constituents. If a material-dependent effective stress contribution is to arise, it is, in general, nonvanishing simultaneously in both the solid and fluid constituents. Moreover, saturation pressure, effective stresses and compressibility constitutive equations determine the exchange volume forces. In a theoretical formulation without non-isotropic strain measures, second density-gradient effects must be incorporated, not only to accommodate for the equilibrium-solid-shear stress and the interaction among neighboring solid-matrix pores, but also to describe internal capillarity effects. The earlier are accounted for by a dependence of the thermodynamic energy upon the density-gradient of the solid, while the latter derives from a mixed density-gradient dependence. Examples illustrate the necessity of these higher gradient effects for properly posed boundary value problems describing the mechanical behaviour of the disturbed rock zone surrounding salt caverns. In particular, we show that solid second-gradient strains allow for the definition of the concept of static permeability, which is distinct from the dynamic Darcy permeability. Received 1 February 1999; accepted for publication 9 March 1999     

Local likelihood ratio tests in the normal mixture model

The test for homogeneity in the mixture normal model is difficult to study due to the breakdown of the regularity conditions under standard theory. The asymptotic optimality of the likelihood ratio test is questionable and its distributional properties are also difficult to evaluate. In this paper, we consider and compare several tests based on the local likelihood ratio which are shown to be quite competitive compared with the generalized likelihood ratio test.     

采用盲信号分离算法处理GC-FTIR信号

针对气相色谱-红外(GC-FTIR)联用的多维数据处理,提出基于盲信号分离的色谱重叠峰分离和红外吸收谱图纯化的定性定量分析方法。优点在于充分利用联用仪器提供的大量信息,解决红外和色谱分析中有机混合物无法完全分离的难题。该方法对二甲苯的同分异构体系进行了研究,验证了理论和算法的合理性,对独立分量分析的数据进行了完整的解释,讨论了针对定量分析产生误差的原因。     

毛竹屑与玉米淀粉共液化产物制备聚氨酯泡沫研究

采用单因素试验设计,研究了液化剂组成、液比以及毛竹屑与淀粉的比例对液化产物理化性质、及所制备的聚氨酯泡沫材料的物理力学指标影响.结果显示当以50%乙二醇+50%碳酸亚乙酯混合物作为液化剂、添加相当于液化剂质量3%的浓硫酸为催化剂、在(150±5)℃(油浴)和常压条件下,液化150min,搅拌速度30r/min,取得本试验条件下最好的竹屑液化效果,液化产物中竹屑含量25%,残渣率3.96%,但该液化产物中天然聚合物碎片含量少,所制备的聚氨酯泡沫材料塌陷;竹屑与玉米淀粉共液化有效提高了液化产物中生物质的含量,但占液化剂质量25%竹屑+占液化剂质量125%玉米淀粉共液化产物粘度太高(8.85Pa.s);而20%竹屑+130%玉米淀粉的共液化产物与4,4′-二苯基甲烷二异氰酸酯以及各种助剂按异氰酸酯基/羟基摩尔比为1.1配合时,所制备的聚氨酯泡沫材料表观密度为33.6kg/m3、压缩强度118kPa、弹性模量6.91MPa,在周年生物降解试验中,该生物质基聚氨酯硬质泡沫失重率为12.63%.     

混合溶剂作淋洗剂的体积排除色谱谱图中溶剂化高分子峰和溶剂峰之间内在关系的理论分析

根据体积排除色谱(SEC)研究高分子溶质优先溶剂化的基本原理,证明在SEC色谱图中被束缚溶剂产生的面积与自由溶剂产生的面积大小相等方向相反,在研究优先溶剂化时从高分子峰入手和从自由溶剂峰入手在理论上具有等价性.分析表明,通过对溶剂化高分子峰的研究,还可以得到另一个重要物理参数——恒化学位时高分子溶液的折光指数增量.     

Butanol–acetone mixture blended with cottonseed biodiesel: Spray characteristics evolution,combustion characteristics,engine performance and emission

Increasing energy demands and more stringent legislation relating to pollutants such as nitrogen oxide (NO_x) and carbon monoxide (CO) from fossil fuels have accelerated the use of biofuels such as biodiesel. However, current limitations of using biodiesel as an alternative fuel for CI engines include a higher viscosity and higher NO_x emissions. This is a major issue that could be improved by blending biodiesel with alcohols. This paper investigates the effect of a butanol–acetone mixture (BA) as an additive blended with biodiesel to improve the latter's properties. Macroscopic spray characteristics (spray penetration, spray cone angle and spray volume) were measured in constant volume vessel (CVV) at two injection pressures. A high-speed camera was used to record spray images. The spray's edge was determined using an automatic threshold calculation algorithm to locate the spray outline (edge) from the binary images. In addition, an engine test was carried out experimentally on a single-cylinder diesel engine. The engine's performance was measured using in-cylinder pressure, brake power (BP) and specific fuel consumption (SFC). Emission characteristics NO_x, CO and UHC were also measured. Neat biodiesel and three blends of biodiesel with up to 30% added BA were tested. The experimental data were analyzed via ANOVA to evaluate whether variations in parameters due to the different fuels were significant. The results showed that BA can enhance the spray characteristics of biodiesel by increasing both the spray penetration length and the contact surface area, thereby improving air–fuel mixing. The peak in-cylinder pressure for 30% BA was comparable to neat diesel and higher than that of neat biodiesel. Brake power (BP) was slightly improved for 10% BA at an engine speed of 2000 rpm while SFC was not significantly higher for any of the BA-biodiesel blends because of the smaller heating value of BA. Comparing the effect on emissions of adding BA to biodiesel, increasing the amount of BA reduced NO_x and CO (7%) and (40%) respectively compared to neat biodiesel, but increased UHC.     

The Binary Mixtures of Lambda-Cyhalothrin,Chlorfenapyr, and Abamectin,against the House Fly Larvae,Musca domestica L.

The house fly Musca domestica L. is one of the medical and veterinary pests that can develop resistance to different insecticides. Mixing insecticides is a new strategy for accelerating pest control; furthermore, it can overcome insect resistance to insecticides. This study aims to evaluate three insecticides, chlorfenapyr, abamectin, and lambda-cyhalothrin, individually and their binary mixtures against 2nd instar larvae of M. domestica laboratory strain. Chlorfenapyr exhibited the most toxic effect on larvae, followed by abamectin then the lambda-cyhalothrin. The half-lethal concentrations (LC₅₀) values were 3.65, 30.6, and 94.89 ppm, respectively. These results revealed that the high potentiation effect was the mixture of abamectin/chlorfenapyr in all the mixing ratios. In contrast, the tested combination of lambda-cyhalothrin/abamectin showed an antagonism effect at all mixing ratios against house fly larvae. The total protein, esterases, glutathione-S-transferase (GST), and cytochrome P-450 activity were also measured in the current investigation in the larvae treated with chlorfenapyr. Our results indicate that GST may play a role in detoxifying chlorfenapyr in M. domestica larvae. The highest activity of glutathione-S-transferase was achieved in treated larvae with chlorfenapyr, and an increase in cytochrome P-450 activity in the larvae was observed post-treatment with Abamectin/chlorfenapyr.     

近红外光谱用于低温水结构的分析

采用近红外光谱分析并结合拉曼光谱和分子动力学模拟研究了二甲基亚砜(DMSO)-水混合物中水在低温时的结构,对DMSO降低水冰点的机理进行了讨论.通过对不同DMSO含量混合物的近红外和拉曼光谱分析,发现了DMSO与水相互作用的光谱信息,表明DMSO与水在混合物中主要以摩尔比1∶2和2∶1的氢键结构(DW2和D2W)的形式存在,结构形式主要取决于DMSO和水在混合物中的比例.通过对水和30%(摩尔分数)DMSO-水混合物的温控近红外光谱分析,发现DW2结构抑制四面体水结构的形成是混合物冰点降低的主要原因.采用分子动力学模拟对DMSO-水混合物体系进行的模拟进一步证明了结论的可靠性.     

The first validated HPLC method for separation and quantification of imiprothrin and deltamethrin in insecticide spray formulation

This work is concerned with novel, accurate and precise determination of two common insecticides, imiprothrin and deltamethrin, using HPLC. The chromatographic conditions were optimised for the best separation. The column was Intersil ODS (4.6 x 250 mm with 5 µm particle size). The mobile phase consists of a mixture of acetonitrile and water (90:10, v/v) at a flow rate of 1.2 mL/min. UV detection was accomplished at 230 nm using chlorpyriphos as an internal standard. The method was validated according to International Conference on Harmonization (ICH) guidelines and was found to be linear over the range 7.5–45 µg/mL for imiprothrin and 5–30 µg/mL for deltamethrin. The method was applied to the assay of both insecticides in the combined spray formulation from the Egyptian market. Statistical comparison between the proposed and the reported methods showed no significant difference. The method can be applied for simultaneous determination of both compounds in different market products with high specificity and in quality control laboratories for insecticide residue monitoring.