Effect of short-chain alcohols on surfactant-mediated reversed-phase liquid chromatographic systems

The behaviour of β-blockers in a reversed-phase liquid chromatographic (RPLC) column with mobile phases containing a short-chain alcohol (methanol, ethanol or 1-propanol), with and without the surfactant sodium dodecyl sulphate (SDS), was explored. Two surfactant-mediated RPLC modes were studied, where the mobile phases contained either micelles or only surfactant monomers at high concentration. Acetonitrile was also considered for comparison purposes. A correlation was found between the effects of the organic solvent on micelle formation (monitored by the drop weight procedure) and on the nature of the chromatographic system (as revealed by the retention, elution strength and peak shape of β-blockers). When SDS is added to the mobile phase, the free surfactant monomers bind the C18 bonded chains on the stationary phase, forming an anionic layer, which attracts strongly the cationic β-blockers. The retention is modified as a consequence of the solving power of the organic solvent, micelles and surfactant monomers. The molecules of organic solvent bind the micelles, modify their shape, and may avoid their formation. They also bind the monomers of surfactant, desorbing them from the stationary phase, which affects the retention. The remaining surfactant covers the free silanols on the siliceous support, avoiding the interaction with the cationic solutes. The retention of β-blockers results from a combination of electrostatic and hydrophobic interactions, the latter being weaker compared to the hydro-organic system. The peak efficiencies and asymmetries are excellent tools to probe the surfactant layer on the stationary phase in an SDS/organic solvent system. The peaks will be nearly symmetrical wherever enough surfactant coats the stationary phase (up to 60% methanol, 40% ethanol, 35% 1-propanol, and 50% acetonitrile).     

正丁醇在N,N-二甲基甲酰胺+水溶液中的体积性质

测定了２９８。１５Ｋ时正丁醇＋Ｎ，Ｎ－二甲诺甲酰胺（ＤＭＦ）＋水三元系的密度求出正丁醇在ＤＭＦ＋水混合溶剂中的表观摩尔体积。观察２到：⑴Φ＾０．Ｅ～ｆｍ与ＶＤＭＦ＾Ｅ～ｆｍ之间存在相似变化关系，其中Φ２＾０．Ｅ为正丁醇的过量无限稀释表观摩尔体积，ＶＥＭＦ＾Ｅ为ＤＭＦ＋水二元系中ＤＭＦ的过量偏摩尔体积，ｆｍ为混合溶剂中ＤＭＦ的摩尔分数。⑵Ｂ１～ｆｍ与０６２１２＾０．Ｅ～ｆｍ之间存的反向变化关系。Ｂ１     

密度泛函理论研究Gd（H2O）n^3＋（n=8，9）化合物的结构及相对稳定性

用密度泛函理论方法研究了气相和水溶液中Gd（H2O）n^3＋（n=8，9）化合物的结构和相对稳定性，其中水溶剂效应利用极化连续介质方法结合多种溶质空腔模型进行模拟．气相计算得到的化合物结构与实验观察结果一致．计算结果表明，在气相中9配位Gd（H2O）9^3＋比8配位Gd（H2O）8^3＋稳定，而在水溶液中稳定顺序刚好相反，这一结果不依赖于计算中采用的空腔模型种类，而且也与实验结果吻合．最后，通过采用各种空腔模型计算Gd^3＋的水合自由能，并与实验值比较，发现当化合物只包含第一层配位水分子时，UA0、UAHF及UAKS空腔模型最适合研究Gd^3＋在水溶液中的性质．     

A method for predicting the deflection of reinforced concrete beams strengthened with carbon plates

For strengthening bent beams, plates of reinforced plastics are glued to their tensioned surface. As s result, the beam becomes layered, and it is possible to control its rigidity and deflection. Based on the methods of structural mechanics of layered media, a method is elaborated for determining the deflection of such beams on the entire range of loading up to their ultimate failure. A comparison between the theoretical and experimental results is carried out. __________ Translated from Mekhanika Kompozitnykh Materialov, Vol. 42, No. 1, pp. 45–60, January–February, 2006.     

粘贴碳纤维布加固混凝土管道试验研究

首次通过对14个素混凝土和14个钢筋混凝土环状试件外粘碳纤维布加固性能进行试验，研究了碳纤维布加固混凝土内压圆管的破坏特征、受力性能和破坏机理。对不同加固方法及一次或二次受力的混凝土管在内压力作用下的极限承载力、荷载一应变关系等方面进行了研究。试验结果表明，用碳纤维布加固混凝土内压管可以显著地提高极限承载力，明显的改善了构件的延性，能够获得良好的力学性能。加固后试件的开裂承载力与未加固试件相比，提高幅度不大，加固试件二次受力与一次受力相比，开裂荷载有所降低，但极限承载力基本相同。用碳纤维布加固内压管是一个新课题，具有很好的应用前景，用本文提出的加固方法具有优良的加固性能，可为工程应用提供参考。     

Approximate analytical solutions for solute transport in two-layer porous media

Mathematical models for transport in layered media are important for investigating how restricting layers affect rates of solute migration in soil profiles; they may also improve the analysis of solute displacement experiments. This study reports an (approximate) analytical solution for solute transport during steady-state flow in a two-layer medium requiring continuity of solute fluxes and resident concentrations at the interface. The solutions were derived with Laplace transformations making use of the binomial theorem. Results based on this solution were found to be in relatively good agreement with those obtained using numerical inversion of the Laplace transform. An expression for the flux-averaged concentration in the second layer was also obtained. Zero- and first-order approximations for the solute distribution in the second layer were derived for a thin first layer representing a water film or crust on top of the medium. These thin-layer approximations did not perform as well as the binomial solution, except for the first-order approximation when the Peclet number,P, of the first layer, was low (P<5). Results of this study indicate that the ordering of two layers will affect the predicted breakthrough curves at the outlet of the medium. The two-layer solution was used to illustrate the effects of dispersion in the inlet or outlet reservoirs using previously published data on apparatus-induced dispersion.The U.S. Government right to retain a non-exclusive, royalty free licence in and to any copyright is acknowledged.     

碳纤维布加固高温作用后的连续梁试验研究和可靠度分析

在实际加固工程中无法对钢筋混凝土连续梁梁顶进行加固,因此在试验中采用CFRP来加固梁的跨中,增强其正截面的抗弯承载力,并利用梁支座处出现塑性铰,引起弯矩重分布的特性,来达到加固的目的。为使试验更加接近加固工程实际情况,试验中加固都是在持载情况下进行的。试验结果表明:粘贴CFRP可以有效地提高连续梁的抗弯承载力;在不同的加固量下,加固后的梁有不同的破坏模式;本文对加固后的连续梁的可靠度进行了分析。数据表明,在加固量适当的情况下,加固后的可靠度基本能与现行规范保持一致。其试验及分析结果对相应的规范编制及工程应用具有较高的应用价值。     

碳纤维布与钢板复合加固梁剥离破坏研究

通过12根碳纤维布与钢板复合加固钢筋混凝土梁的抗弯性能研究,结果表明复合加固方式能有效地改善被加固构件的受力性能,但常由于复合加固层的剥离可能导致加固效果的降低。复合加固层与被加固构件之间的剥离是由于薄弱截面在剪应力及正应力的集中作用下而产生的,文中对复合加固层与混凝土之间的粘结剪应力及剥离正应力的计算公式分别进行推导,并进一步对碳纤维布与钢板复合加固的剥离机理进行分析,为工程应用提供依据。     

Experimental investigation of solute transport in large,homogeneous and heterogeneous,saturated soil columns

Laboratory tracer experiments were conducted to investigate solute transport in 12.5-m long, horizontally placed soil columns during steady saturated water flow. Two columns having cross-sectional areas of 10×10cm² were used: a uniformly packed homogeneous sandy column and a heterogeneous column containing layered, mixed, and lenticular formations of various shapes and sizes. The heterogeneous soil column gradually changed, on average, from coarse-textured at one end to fine-textured at the other end. NaCl breakthrough curves (BTC's) in the columns were measured with electrical conductivity probes inserted at 50- or 100-cm intervals. Observed BTC's in the homogeneous sandy column were relatively smooth and sigmoidal (S-shaped), while those in the heterogeneous column were very irregular, nonsigmoidal, and exhibited extensive tailing. Effective average pore-water velocities (v _eff) and dispersion coefficients (D _eff) were estimated simultaneously by fitting an analytical solution of the convection-dispersion equation to the observed BTC's. Velocity variations in the heterogeneous medium were found to be much larger than those in the homogeneous sand. Values of the dispersivity,=D _eff/v _eff, for the homogeneous sandy column ranged from 0.1 to 5.0 cm, while those for the heterogeneous column were as high as 200cm. The dispersivity for transport in both columns increased with travel distance or travel time, thus exhibiting scale-dependency. The heterogeneous soil column also showed the effects of preferential flow, i.e., some locations in the column showed earlier solute breakthrough than several locations closer to the inlet boundary. Spatial fluctuations in the dispersivity could be explained qualitatively by the particular makeup of the heterogeneities in the column.