Prediction of the Conductance of Strong Electrolytes and the Calculation of the Ionization Constant of Weak Electrolytes in a Dilute Solution by a New Equation

In order to predict the conductance for dilute 1-1 valent electrolyte solutions,a new conductance equation was proposed based on the Onsager and Onsagar-Fuoss-Chen conductance equation.It has only one parameter A,which can be obtained directly from the data of ionic limiting molar conductivity Λ∞m,and its expression is very simple.The new equation has been verified by the experimental molar conductivities of some single strong electrolyte and mixed electrolyte solutions at 298.15 K reported in literatures.The results are in good agreement with the experimental data.Meanwhile the ionization constants of some weak electrolyte solutions were calculated by a modified equation of this new equation,and it was also found that the calculation results are in good agreement with the data in the literature.     

ADSORPTION FROM SOLUTIONS——ADSORPTION FROM MIXED SOLUTIONS OF TRITON X-100 AND SODIUM n-ALKYL SULFATES ON SILICA GEL

The adsorption of Triton X-100 and pure sodium n-alkyl sulfates (C_8, C_(10) and C_(12)) from single and mixed aqueous solutions on silica gel at 25°C has been determined. The adsorption of Triton X-100 shows unusual S-type isotherm. At higher concentrations, the adsorption isotherm reaches a plateau. This plateau coverage corresponds approximately to 1.00 nm~2 per adsorbed molecule. It seems that the packing of adsorbed Triton X-100 on silica/water interface is much less dense than that on the air/water interface. No significant effects of pH and of the presence of sodium chloride (0.1 M) have been observed. Moreover, no significant adsorption for sodium n-alkyl sulfates has been observed, either from single or from the mixed solutions. Thus the competitive adsorption between Triton X-100 and sodium n-alkyl sulfates may not be important.When dealing with the adsorption of Triton X-100 from the mixed solutions, there are two different effects and two different concentration regions can be discerned; (     

Effect of Na＋, K＋ and Ca2＋ Ions on Physico-chemical Properties of Thymine, Cytosine, Thymidine and Cytidine in Aqueous Urea Solution

Experimental determination of density, ultrasonic velocity and viscosity of two pyrimidine bases thymine and cytosine along with their respective nucleosides, thymidine and cytidine has been carried out in aqueous urea solutions in the presence of different concentrations of three salts, viz. NaCl, KCl and CaCl₂. The experimental data have been used for the computation of various thermodynamic parameters, viz. apparent molar volume, apparent molar compressibility, coefficients A and B of the Jones-Dole equation, internal pressure, acoustic impedance, etc. Structural studies of solutions under investigation have also been carried out by ultraviolet spectroscopy, and an attempt has been made to collaborate the findings of ultraviolet spectroscopy with results obtained thermodynamically.     

INTERMOLECULAR EXCIMER INTERACTION IN POLYMERS

A butadiene-styrene copolymer of low styrene eontent (5% Wt.) has been characterizedby ~1H NMR to have only isolated styrene units on the chain. The fluorescence spectra of thesample in dilute solutions of a good solvent (dichlorethane) at 25--26℃ show monomerfluorescence only. Changes of the fluorescence spectra from a good solvent to poor solvents(dichloroethanemethanol mixture), and form dilute to concentrated solutions up to the solidfilm confirm that excimer formation exists between nonadjacent chromophores in the ehainand between interchain chromophores. Comparison of the spectra obtained from a diluteθ-solution and solid film gives us an estimation of the relative importance of the intrachainexcimer interaction and interchain excimer interaction in the solid sample studied. Theseresults may help us visualize the interpenetration and entanglement of polymer coils duringtransition from a dilute solution to a concentrated one and to a solid polymer.     

Theoretical prediction on heats of formation for polyisocyanocubanes——Looking for typical high energetic density material(HEDM)

The heats of formation (HOP) for all the 21 polyisocyanocubanes are calculated systematically with density functional theory (DFT) B3LYP and semiempirical MO(MINDO/3, MNDO, AM1 and PM3) methods. First, the accurate HOFs for the 8 title compounds are obtained by means of designed isodesmic reactions at DFT-B3LYP/6-31G* level, and the cubane cage skeleton has not been broken (i.e. choosing cubane as a reference compound) to produce more accurate and reliable results. It is found that there are good linear relationships between the HOFs calculated using the B3LYP/6-31G* and four semiempirical MO methods, respectively, and all of the linear correlation coefficients are more than 0.9971. The HOFs obtained from PM3 calculation are the best among the four semiempirical MO methods. Then, the accurate HOFs at B3LYP/6-31G* level of other 13 polyisocyanocubanes are obtained by systematically correcting their PM3-calculated HOFs. Polyisocyanocubanes have very high HOFs, and the HOFs increase linearly with the increa     

Synthesis of a Polymer—bound Sensitizer and its Application in the Photoisomeriz

A polymer-bound photosensitizer was synthesized by the reaetion of Merritield resin with 9-anthraeenemethanol in the presence of potassium hydride.The photoisomerization of trans-vitamin D3 to cis-vitamin D3 was earried out with this polymer-bound photosensitizer in ethanol and toluene solutions.The experiment results demonstrate that this solid photosensitizer is efficient for the photoismerization and easy for separation from the reaetion mixtures.     

Effect of Zr and C Co-doping on the Optical Properties and Electronic Structure of TiO_2

The systematic trends and effect introduced by Zr and C co-doping to TiO2 of electronic structure and optical properties of anatase TiO2 have been calculated by the plane-wave ultra-soft pseudopotential density functional theory (DFT) method within the generalized gradient approximation (GGA) for the exchange-correlation potential. Through the current calculations, the density of states (DOS), energy band structure and optical absorption coefficients have been obtained for TiO2 and compared with the doped TiO2, and the influence of electronic structure and optical properties caused by Zr and C co-doping has been presented qualitatively together. The results revealed that the energy band gap has been decreased owing to the doped Zr and C, whereas the optical absorption coefficients have been increased in the region of 400～800 nm and a red shift of absorption band can be found. Accordingly, photo catalytic activity of TiO2 has been enhanced. The current calculations are in good agreement with the experimental data.     

Microdialysis-liquid chromatographic study on competitive binding of drugs to protein

A new method to determine the interaction between drug and protein has been developed by utilizing the technique of microdialysis sampling with the ketoprofen and the human serum albumin (HSA) as the model of drug and protein.Two kinds of binding sites of HSA to ketoprofen have been observed.The binding constants and number of binding sites obtained by the Scatchard equation are 0.799,3.18×106 mol-1 L and 2.15,2.01×105 mol-1 L,respectively The displacement binding of drugs to HSA has also been studied.The strong displacement of competitive binding of ibuprofen with ketoprofen to HSA was observed,which means that the primary binding site of HSA to ketoprofen and that to ibuprofen are the same.However,only a weaker displacement of warfarin for the association of ketoprofen with HSA was observed,which may suggest that the primary binding site of HSA to ketoprofen is different from that to warfarin.Such a displacement effect for competitive binding of drugs to HSA was explained by the displacement model i     

Vapor Pressure Osmometry and Its Applications in the Osmotic Coefficients Determination of the Aqueous Monomer Glycol and Polymer Polyethylene Glycol Solutions at Various Temperature

Based on the principle and calibration of vapor pressure osmometer and its application in the thermodynamics of the aqueous solutions, the results on aqueous solution of monomer glycol,PEG200,PEG400,PEG1500 and PEG2000 over the different concentration range at various temperatures were reported.Using a linear least-square fitting routing,the osmotic coefficients were fitted by a simple polynomial equation.It was found that the relationship between the molar osmotic coefficients (Φ） and the molar concentration(c) of the solutions are in a quite good agreement with the fitted polynomial equation at various temperatures over the different concentration range.The experimental results also show that over the studied concentration range and at various temperatures,the concentration dependence of the molar osmotic coefficients of the aqueous solution systems with the solutes of PEG200,PEG400,PEG1500 and PEG2000 are totally presented in a rising tend,and their temperature dependence of the osmotic coefficients of the aqueous solution systems of the molar concentration exhibits their own regularities,respectively.The aqueous glycol solution system exhibits the properties of the dilute solution.     

Resonance Rayleigh scattering study of the interaction of bleomycinA_5 with nucleic acids and its analytical application

The interaction of bleomycinA5 with nucleic acids has been investigated by using resonance Rayleigh scattering (RRS), molecular absorption and fluorescence spectra. The result shows that in near pH 2.2 buffer medium and absence of any metal ions, nucleic acids are capable of binding with bleomycinA5 (BLMA5) to form complexes which can remarkably enhance the RRS intensity and result in batho- chromic and hyperchromic molecular absorption of nucleic acids and fluorescence quenching of bleomycinA5. The RRS spectral characteristics for the binding products of bleomycinA5 with various DNA and RNA are similar, and the maximum RRS peaks are at 301 nm for ctDNA and sDNA, 370 nm for hsDNA, 310 nm for RNAtypeVI and RNAtypeIII, respectively. The increments of RRS intensity are greatly different in which DNA enhances greatly and RNA enhances lightly. In this work, the optimum condi- tions of the interaction and some influencing factors have been investigated. The reaction mechanism and a binding model for the interaction of BLMA5 with the nucleic acids are discussed. In addition, a highly sensitive, simple and rapid new method for the determination of DNA has been developed. The detection limits (3σ) are 5.7 ng/mL for ctDNA, 7.4 ng/mL for sDNA and 9.2 ng/mL for hsDNA, respectively. The method can be applied to determination of trace amounts of DNA.     

Prediction of affinities of peptides for calmodulin

A simple method has been developed to predict the calmodulin-binding domains of peptides and the affinities of the peptides for calmodulin based on a model for the calmodulin-binding domains of peptides proposed in a previous paper and the literature data of calmodulin-binding peptides. The effects of hydrophobitities, α-helix-forming tendencies, and basicities of peptides on their affinities for calmodulin were studied. Model peptides were designed to examine the calmodulin-binding domain model and the prediction method. The determined dissociation constants of the complexes formed from the model peptides and calmodulin are in good agreement with the predicted results.     

Photocatalytic Characterization of TiO_2 Supported on Active Carbon

Photocatalysis on TiO2, with a promising application to the elimination of organic contaminants from air and water, has been a particularly active area1. For such application, it is important to improve the efficiency of TiO_2 photocatalysts. In the most cases, the concentration of organic contaminants in water is extremely dilute (ppm level or below) and TiO_2 itself has low adsorbabilities for them, it usually takes a long time to complete their decomposition. One of the effective ways to …     

Theoretical Study on Co^3＋ in Aqueous Solution in Terms of ABEEM/MM Model

A detailed theoretical investigation on Co^3＋ hydration in aqueous solution has been carded out by means of molecular dynamics （MD） simulations based on the atom-bond electronegativity equalization method fused into molecular mechanics （ABEEM/MM）. The effective Co^3＋ ion-water potential has been constructed by fitting to ab initio structures and binding energies for ionic clusters. And then the ion-water interaction potential was applied in combination with the ABEEM-7P water model to molecular dynamics simulations of single Co^3＋（aq.） solution, managing to reproduce many experimental structural and dynamical properties of the solution. Here, not only the common properties （radial distribution function, angular distribution function and solvation energy） obtained for Co^3＋ in ABEEM-7P water solution were in good agreement with those from the experimental methods and other molecular dynamics simulations but also very interesting properties of charge distributions, geometries of water molecules, hydrogen bond, diffusion coefficients, vibrational spectra are investigated by ABEEM/MM model.     

A New Molecularly Imprinted Polymer for Solid-phase Extraction of Cotinine from Human Urine

A molecularly imprinted polymer （MIP）, prepared around a cotinine template, has been synthesized. The feasibility of using the polymer for solid-phase extraction （SPE） of cotinine from biological samples has been investigated. The results show that cotinine can be quantitatively retained and eluted from the polymer. Experiments with human urine samples indicate that clean target analyte is obtained for HPLC with UV detection using the protocol.     

A MARKOV-TYPE ANALOG MODEL FOR PREDICTION OF TYPHOON MOTION IN NORTHWESTERN PACIFIC

In this paper, a Markov-type analog model for the prediction of the tropical cyclone motion is developed for the Northwestern Pacific. The probabilities are studied by using the United States National Hurricane Center HURRAN model as a guide. In order to approach and suit to the new circumstance continuously, a Markov process has been used to describe the probability forecast for typhoon movement. The model is different from the traditional analog method both in searching probability solutions and in renewing initial data.A transplantation model (Model 1) has also been developed by using the traditional analog methods. Both Model 1 and Markov-type analog model (Model 2) have been tested for 95 simultaneous cases, which are independent data for the years 1981 and 1982. It has been shown from this examination that the Markov-type model appears to give smaller forecast errors.     

Investigation on the Extraction Mechanism of Au（I） from Cyanide Solution with Quaternary Ammonium System

During the past decades, there has been a renewed interest in the application of solvent extraction to the recovery of Au (I) from cyanide solutions1,2. Among those various extractants, the amine extractants with the addition of organic phosphorus oxide as cosolvent have been widely investigated3,4. Various diluents and modifiers have been selected to optimize the extraction system so as to increase the loading capacity, improve the selectivity and/or reduce emulsification5. Quaternary amm…     

Synthesis and Crystal Structure of a Puckered Rhombus Grid-like Coordination Polymer with Bridging Ligand Containing Sulfanyl Linker

Introduction The design and construction of metal-organic frameworks (MOFs), obtained by metal-directed self-assembly from labile metal centers and multidentate bridging ligands, is a rapidly developing area of su-pramolecular chemistry.1-3 Besides the aesthetic struc-tural and fascinating functional motifs, they are of in-terest both for understanding the mechanisms of the assembly process and for the host-guest chemistry asso-ciated with their large central cavities.4-13 It has been documen…     

Synthesis and Application of Novel Chiral Poly-nuclear-Mn(III) Catalysts on Asymmetric Epoxidation of Alkenes.

The interest of the coordination chemistry of manganese has been driver by the important roles of metalloenzymes and highly valuable catalysts in olefin expoxidation.1 Jacobsen Salen-Mn complexes with a simple structure have been commercially utilized to catalyze asymmetric epoxidation of unfunctionalized cis-alkenes2, but the catalytic enantioselectivity for trans-alkenes, unfortunately, are lower and this kinds of complexes are unstable and difficult to be recovered for reuse.3 In order to i…     

Carbon Dioxide/Methane Separation by Adsorption on Sepiolite

In this work,the use of sepiolite for the removal of carbon dioxide from a carbon diox- ide/methane mixture by a pressure swing adsorption(PSA)process has been researched.Adsorption equilibrium and kinetics have been measured in a fixed-bed,and the adsorption equilibrium parameters of carbon dioxide and methane on sepiolite have been obtained.A model based on the LDF approxima- tion has been employed to simulate the fixed-bed kinetics,using the Langmuir equation to describe the adsorption equilibrium isotherm.The functioning of a PSA cycle for separating carbon dioxide/methane mixtures using sepiolite as adsorbent has also been studied.The experimental results were compared with the ones predicted by the model adapted to a PSA system.Methane with purity higher than 97% can be obtained from feeds containing carbon dioxide with concentrations ranging from 34% to 56% with the proposed PSA cycle.These results suggest that sepiolite is an adsorbent with good properties for its employment in a PSA cycle for carbon dioxide removal from landfill gases.