木质素磺酸氧化与络合产物分子结构研究

介绍了研究木质素磺酸(LS)分子结构特性值的常用方法。系统地研究了络合、氧化反应对 LS分子结构的影响。分析了络合、氧化反应的作用机理。     

On the measurement of the real values of individual ionic activities: A chemical engineering perspective

This work demonstrates the perfect analogy between the standard method for determining activities in non-electrolyte mixtures and the method used for the determination of ionic activities in electrolyte solutions. For the case of electrolyte solutions, the general procedure of solving three equations with three unknowns is discussed and the reasons why this procedure failed to work for the case of KCl solutions are recapitulated. A modified iteration procedure implemented in this work gives convergence of the solution after three iterations. The crucial difference between eliminating the junction potential, by combination of independent equations, and the use of a proper estimate of its value is emphasized. A new model-free calibration procedure is proposed and sample calculations of K⁺ and Cl⁻ activities in KCl aqueous solutions are presented. Values of K⁺ and Cl⁻ activities in KCl aqueous solutions obtained by this new procedure and by a variety of other methods and researchers are compared.     

Migration of divalent ions in nylon 6 films

The migration of ions through a nylon-6 film is studied by MRI. For this study the paramagnetic ions Mn²⁺ and Cu²⁺ are used as they act as a contrast agent and are detectable by MRI.     

Continuous biosorption of heavy metal ions by Ca-loadedlaminaria japonica in fixed bed column

Continuous biosorption process for removal of lead and copper by laboratory scale fixed-bed reactor was carried out using Ca-loadedLaminaria japonica. All biosorption processes were observed as cation exchange such as Pb²⁺ vs. Ca²⁺, Cu²⁺ vs. Ca²⁺, and Pb²⁺ vs. Cu²⁺. The affinity of lead ions towardsL. japonica was stronger than that of copper ions because the initial amount of desorbed Cu²⁺ in Cu-Pb system was higher than that of eluted Pb²⁺ in Pb-Cu system.     

Optimization of reaction parameters to prepare HPMA- g -Na-PCMS using can as an initiator

Sodium salts of partially carboxymethylated starch-g-poly(hydroxypropyl methacrylate)(Na-PCMS-g-PHPMA) copolymer containing 35-45% PHPMA were prepared using ceric ammonium nitrate (CAN) as an initiator. All the experiments were run with Na-PCMS (DS-1.10). Graft copolymers were characterized with respect to % PHPMA, % total conversion, % grafting, % grafting efficiency and confirmation of grafting was done by infrared spectral analysis. Variables investigated in the graft copolymerization reaction were nitric acid concentration, reaction time, reaction temperature and ceric ion concentration. The results are discussed with illustration.     

Ar ion induced copper germanide phase formation at room temperature

The copper germanide phase Cu₃Ge which is emerging as an alternative material for making contacts and interconnects for semiconductor industry has been produced across the interface of Cu/Ge bilayers by ion beam mixing at room temperature using 1 MeV Ar ions. The dose dependence of the thickness of the mixed region shows a diffusion controlled mixing process. The experimental mixing rate and efficiency for this phase are 5·35 nm⁴ and 10·85 nm⁵/keV respectively. At doses above 8 × 10¹⁵ Ar/cm² the formation and growth of another copper rich phase Cu₅Ge has been observed. The present theoretical models are inadequate to explain the observed experimental mixing rate.     

Impact of Divalent Metal Ions on Regulation of Trans-Cleavage Activity of CRISPR-Cas13a: A Combined Experimental and Computational Study

CRISPR-LbuCas13a has emerged as a revolutionary tool for in vitro diagnosis. Similar to other Cas effectors, LbuCas13a requires Mg²⁺ to maintain its nuclease activity. However, the effect of other divalent metal ions on its trans-cleavage activity remains less explored. Herein, we addressed this issue by combining experimental and molecular dynamics simulation analysis. In vitro studies showed that both Mn²⁺ and Ca²⁺ could replace Mg²⁺ as cofactors of LbuCas13a. In contrast, Ni²⁺, Zn²⁺, Cu²⁺, or Fe²⁺ inhibits the cis- and trans-cleavage activity, while Pb²⁺ does not affect it. Importantly, molecular dynamics simulations confirmed that calcium, magnesium, and manganese hydrated ions have a strong affinity to nucleotide bases, thus stabilizing the conformation of crRNA repeat region and enhancing the trans-cleavage activity. Finally, we showed that combination of Mg²⁺ and Mn²⁺ can further enhance the trans-cleavage activity to allow amplified RNA detection, revealing its potential advantage for in vitro diagnosis.     

锶在包气带迁移的“双峰”分布机理探讨

本文通过砂柱实验 ,重现了淋溶条件下锶在黄土包气带迁移的“双峰”分布现象 ,并用离子竞争反应理论解释了这一现象     

Adsorbing colloidal flotation removing metals ions in a modified jet cell

The removal of Cu²⁺, Zn²⁺ and Ni²⁺ ions from synthetic wastewater with a modified Jameson cell (MJC) was studied using adsorption colloidal flotation (ACF). A colloidal dispersion of Fe (OH)₃ (formed in situ from FeCl₃) at pH 11 was used as an adsorbent colloid to ensure full adsorption and precipitation. The precipitates were flocculated with polyacrylamide and hydrophobised with sodium oleate and pine oil as a frother during the flotation stage. In the modified jet cell, the downcomer was sealed at the bottom with a diffuser, and the re-flotation of detached flocs and the probability of bubbles/particles capture was enhanced, which improved the recovery rate. As a result, the modified Jameson cell was more efficient (higher loaded carrier recoveries) than the conventional jet cell (CJC) in removing heavy metals ions. The physico-chemical characteristics, cell design and operating parameters were studied, and the removal efficiency was evaluated by monitoring the final concentration of ions in the treated effluent. The results indicated that the removal efficiencies of the MJC were approximately 95% and 98% for dilute (Cu²⁺, Zn²⁺ and Ni²⁺ concentration of 2 mg/L) and concentrated wastewater (25 mg/L of each ion), respectively. The optimal parameters included a Fe⁺³/ion ratio of 0.5 and a minimum air flow-rate/feed flow-rate ratio of 0.18. The results are discussed in terms of the physical and physico-chemical parameters, and the findings suggested that the proposed flotation technique has great potential for the treatment of wastewater.     

Ozone And Biological Treatments – Effects on the Elimination of Cyanides

Since publications concerning theeffect ofozone on biological treatments are contradictory, increasing biodegradation on the onehand, effect of “stress” on bacteria ontheother, we have selected two compounds which are eliminated only by biodegradation: cyanides andammonium ions. Thestudyhas shown that ozone retards their biodegradation significantly.

Concerning the elimination of organic materials, we have noticed two competitive actions: an increase in the possibility of biodegradation and the effect of “stress” on bacteria. The result of these twoactions is in favor of ozone.