Modeling of fixed-bed adsorption of Cs+ and Sr2+ onto clay–iron oxide composite using artificial neural network and constant–pattern wave approach

A low-cost, non-toxic and effective adsorbent constituted by a montmorillonite coated by iron oxides (montmorillonite–iron oxide composite) was prepared to assess its effectiveness in the removal of Cs⁺ and Sr²⁺ from aqueous solution. Dynamic adsorption experiments were carried out at room temperature under the effect of various operating parameters such as bed depth Z (5–15 cm), initial cation concentration C ₀ (2–50 mg L^?1) and volumetric flow rate Q (0.5–8 mL min^?1). Column performance has been modeled with constant-pattern wave approach combined to the Freundlich isotherm model and artificial neural network (ANN) models. The time, initial cation concentration, bed depth and volumetric flow rate were chosen as the input variables whereas, the outlet concentration C _t was considered as the output variable. The developed network was found to be useful in predicting the breakthrough curves. Experimental data for the used system were well fitted with ANN than the combined constant–pattern wave approach.     

Unsteady Separated Two-Throat Nozzle Flows

A numerical study of a supersonic planar two-throat nozzle flow, using the Reynolds averaged Navier–Stokes equations, is presented. This nozzle flow can induce asymmetrical separation between the throats. The start-up processes are examined. Initial pressure ratio and increasing pressure time influence are investigated. The objective is to gain a better understanding of the mechanisms causing the asymmetry.     

Dative P→Sn interactions in ortho-phenylene phosphine-stannanes

Monophosphine and diphosphine-stannane compounds 1 and 2 are shown spectroscopically, structurally and theoretically to present rare intramolecular P→Sn interactions.     

Electronic structure and optical properties of isolated and TiO2-grafted free base porphyrins for water oxidation: A challenging test case for DFT and TD-DFT

Seven free base porphyrins employed in dye-sensitized photoelectrosynthetic cells are investigated with the aim of benchmarking the ability of different density functional theory (DFT) and time-dependent DFT approaches in reproducing their structure, vertical, and E_0-0 excitation energies and the energy levels alignment (red-ox properties) at the interface with the TiO₂. We find that both vertical and E_0-0 excitation energies are accurately reproduced by range-separated functionals, among which the ω B97X-D delivers the lowest absolute deviations from experiments. When the dye/TiO₂ interface is modeled, the physical interfacial energetics is only obtained when the B3LYP functional is employed; on the other hand, M06-2X (54% of exchange) and the two long-range corrected approaches tested (CAM-B3LYP and ω B97X-D) excessively destabilize the semiconductor conduction band levels with respect to the dye's lowest unoccupied molecular orbitals (LUMOs), predicting no pathway for electron injection. © 2019 Wiley Periodicals, Inc.     

Self-assembled cationic heterochiral honeycomb-layered metal complexes with the in situ generated pyrimidine-2-carboxylato bisdidentate ligand. Hydrothermal synthesis, crystal structures, magnetic properties, and theoretical study of [M2(micro-pymca)3]OH.H2O (M = FeII, CoII)

The hydrothermal reaction of 2-cyanopyrimidine and either CoCl2.6H2O or FeCl2.4H2O affords 2D isostructural coordination polymers [M2(micro-pymca)3]OH.H2O ((M = CoII (1) and FeII (2) pymca = pyrimidine-2-carboxylato). The bisdidentate ligand (pymca) that can be considered an intermediate between bipyrimidine and oxalato is generated in situ from the hydrolysis of 2-cyanopyrimidine. The structure of 1 and 2 consists of heterochiral (6,3) honeycomb layers, crystal water molecules, and OH- anions, the latter playing a template and balancing charge role in the structure. Both compounds exhibit antiferromagnetic interactions between metal ions through the pyrimidine-2-carboxylate bridging ligand. Compound 1 is a spin-canted antiferromagnet leading to weak ferromagnetism at Tc < 10 K with a coercitive field of 580 Oe, whereas compound 2 is an antiferromagnet with TN = 21 K. Fit of the variable-temperature magnetic susceptibility data of 2 to the empirical equation for a regular honeycomb with S = 1 derived from Monte Carlo simulations leads to the following parameters: J = -4.57(2) cm-1 and g = 2.300(4). Density functional calculations have been used to explain the magnetic coupling in 2.     

一种具高活性的酪氨酸酶基因启动子片段的分离

利用大肠杆菌启动子探测质粒ｐＫＫ２３２－８为载体,经ＨｉｎｄⅢ－ＢａｍＨⅠ完全消化后与ＨｉｎｄⅢ－ＢａｍＨⅠ部分消化的嗜麦芽假单胞菌染色休ＤＮＡ进行体外连接,转化Ｅ．ｃｏｌｉＨＢ１０１感受态细胞,在含氨苄青霉素（Ａｐ）和氯霉素（Ｃｍ）的选择平板上筛选转化子．从随机挑选的５４株转化子中,获得一株抗氯霉素水平达１０００ｍｇ／Ｌ的转化子Ｅ．ｃｏｌｉＰＡＳＩ,所含重组质粒被命名为ｐＡＳＩ．经限制性酶切分析和杂交分析表明,ｐＡＳＩ质粒上插入了一段来源于嗜麦芽假单胞菌染色体的ＤＮＡ片段,其大小为１．４ｋｂ．ＳＤＳ－ＰＡＧＥ分析表明转化子Ｅ．ｃｏｌｉＰＡＳＩ在含Ｃｍ的培养基上,额外表达了一条２２×１０３的ＣＡＴ蛋白质带．将重组质粒ｐＷＳＹ上的嗜麦芽假单胞菌ｍｅｌ基因亚克隆到ｐＡＳＩ上１．４ｋｂ启动子功能片段下游,构建成Ｅ．ｃｏｌｉＡＷＳ工程菌株,使黑色素产率提高了７０．６％．     

Thermal design of a spherical electronic device naturally cooled by means of water–copper nanofluid saturated porous media

Journal of Thermal Analysis and Calorimetry - The present work deals with thermal regulation of a spherical electronic device used in naval navigation techniques. Cooling is achieved by means of...