2001 Vol. 14, No. 6

Letter
The reaction of formyl radical HCO with NO was investigated by Time-Resovled Fourier Transform Infrared(TR-FTIR) spectroscopy. Vibrationally excited products CO and HNO were observed. The HNO(ν1) spectrum consists of (200-100) and (100-000) bands. Spectral simulation of provides vibrational population of the CO product at 41μs. The vibrational excited CO (v≤4) was found. The results indicate that the major product channel of HCO+NO is HNO+CO.
Article
A linearized stability analysis of the nonzero pressure gradient Couette flow of ER fluid has been performed. The constructive equation used here was established by Wineman and Rajagopal. After numerical evaluation, it comes that any motions of the boundary wall are shown to have a stabilizing effect. With the applied extra electric field, the effect of ERF can also enhance the stability.
We preformed a self-consistent full-potential LMTO LDA calculation for heavy fermion compoundsLiV2O4. The present results show that the conduction bands in this compound are formed from V 3dstateswith abandwidthof 2.5 eV. Thesymmetric charactersof conduction bandsareof t2gin principle. The energy gap between conduction bands and fully occupied O2p bands is 1.9 eV. The band dispersions near Fermi energy display complicated structures. Furthermore, theN(EF) andγare 11.1states/eVf.u. and 26.7 mJ/molK2determined numerically by LDA calculation, respectively. It is insufficient to clarify the origin of local moment in LiV2O4from plain LDA calculations. In addition to the above LDA calculation, we also find a LSDAsolution of LiV2O4that is lower in total energy than that of LDA calculation. Similarly, LSDA+GGA calculation yields almost the same results as that in LSDA. It is concluded that the mechanism responsible for heavy fermion properties in LiV2O4might be some what different from the plain Kondo mechanism in conventional 4f and 5f heavy fermion compounds and perhaps the quantum transition plays an adequate role to heavy fermion behavior in LiV2O4.
By means of molecular dynamics simulation technique, the solidification processes of Au3Cu under different cooling velocity has been studied. It hs been concluded that the cooling velocity is critical to the structure of Au3Cu. With pair distribution function and pairs analysis method, the local symmetry of molecular-cluster has been analyzed. The variations of potential energy with the temperature and the relationship between the energy and the structure of molecular-cluster have also been studied. From the viewpoint of the variation of energy, the conclusion has been discussed.
The Ono-Kondo isotherm equation for the hydrogen molecules adsorbed within the slit-pores of the carbon micro-pore adsorbents is deduced by the mean-field approximations to the adsorption boundary. Then the maximum adsorption capacities at two typical kinds of stacking of the hydrogen molecules upon the graphite surface are valued by using the characteristics of the lattice gas model and the theory of Microphysics. The values of other parameters for the Ono-Kondo equation at two typical stacking states of hydrogen molecules are obtained by using the ascertained maximum adsorption capacities, the langmuir calibration and the linear regression on the experimental data. The predicted precision of the two equations is evaluated by the mean relative error between the predicted results and the experimental data, and the equation ascertained by the close-packing of hydrogen molecules with the higher accuracy is applied to predict the adsorption isotherm under the same condition described in literatures. The predicted results are compare with the experimental data and those from the GCMC molecular simulation under the same adsorption condition on the same kinds of adsorbents. Finally, the effective range of the ascertained equation is analyzed and the suggestions are given to the application of the equation.
On the basis of successfully designing the schemes for calculation of the enthalpies of formation of alkane isomers and polychlorocarbon isomers applying the idea of polarity interference, we now design a new scheme for calculating the enthalpies of formation of polyhydric alcohol isomers. In this scheme, we reasonably suppose the enthalpy of atomization of any isomer to be equal to the sum of three bond enthalpy terms (i.e., C-C, C-H and C-O-H bond enthalpy terms) and a polarity interference enthalpy term and a hydrogen bond enthalpy term. Fitting such a model to 24 data of enthalpies of atomization of 24 compounds, an estimation formula for their enthalpies of formation has been obtained. In order to test the prediction accuracy, we have designed a predication method in which using the parameters obtained under exclusion of the compound to be predicted at each time, we predict the enthalpy of formation of the compound. According to such a method, the enthalpies of formation for the 24 isomers have been predicted. The average absolute errors from corresponding experimental values, root mean square deviation, and the max absolute errors predicted by this scheme with 5 parameters are not only much less than those predicted by the group scheme with 7 parameters, but also less than the corresponding deviations of experimental data. Compared with other bond additivity schemes for calculation of the enthalpies of formation of compounds, a very important advantage of this new scheme is that its model contains the polarity interference enthalpy and hydrogen bond enthalpy terms well reflecting main non-bonded interaction energies and expressing the structural disparities among different isomers, and greatly reducing parameters.
The atomic ordinal numbergiand its colouring numbergi′based on the systematic nomenclature of organic compound have excellent selectivity for non-hydrogen atom in organic molecules, and mirror its chemical surroundings. The first order autocorrelation topological index 1Gand its colouring index1G′of atomic ordinal number are defined as:1G=∑(gigj)-1,1G′=∑(gi′gj′)-1.1Gand1G′are very easy to be calculated and have good discrimination (better than the famous Kier′s index1Xv) between isomeric alkanes and haloalkanes. It can be expressed as following equation for the change rule of the first ionizating potentialIpfor 27 haloalkanes: Ip=7.4545-0.79341G′-0.70671G+1.5514Xp, R =0.9982 WhereXpis the electronegativity of halogen atom. This correlativity is surpass than that of the literature. The estimated results by above equation are satisfactory.
Concept of energy transfer from over-critical value elements and related parameterαin the OFC model of self-organized criticality (SOC) are introduced into the model of extreme value dynamics. The result of dielectric relaxation function shows a correlation both with KWW function and power law function. Time domain dielectric spectroscopy is used to measure the decay process of slow polarized charges of PP between -15℃to 90℃. The results show that relaxation is power law in lower temperature and relaxation changes from power law to KWW function in upper temperature. Theoretic analysis and experimental results are consistent which imply the βof KWW function reflecting the influence of temperature on relaxation element of material and parameterareflecting the amount of energy transfer and temperature. Whenβis lower orais larger, power law relaxation is more distinct.
The effects of substituting small amounts of Si for Co on the structure and magnetic properties of Ho2Co17 compounds were studied by means of X-ray diffraction and magnetization measurements. All samples are of single phase with the Th2Ni17-type structure. The substitution of Si for Co leads to an approximately linear decreasing in the unit cell volume. The analysis indicates that the saturation magnetization of Ho2Co17-xSix is found to decrease as x increasing from 0 to 3. From thermomagnetization curves measurements, it is assumed that Ho2Co17-xSix compounds display the plane anisotropy at x=0.5. A spin reorientation occurs turning from base-plane into c-axis for 0.5
The preparation, structure and electrochemical properties of titanium oxide film formed by direct thermally oxidation of titanium were investigated by atomic force microscopy, X-ray diffraction, electrochemical impedance spectroscopy and etc. The results showed that the film is rutile TiO2and the crystallization increases with increasing the oxidation temperature and time, the flat band potential shift to negative with increasing the temperature. The TiO2become compact gradually and the electric conductivity decrease when the temperature was higher than600℃.
Silica-supported sodium-modified chromium catalyst Na-7.5%Cr/SiO2is found to be active for simultaneous activation of methane and carbon dioxide to aromatics(SAMCA). The best result shows the methane conversion of 4.0% and the selectivity of 48.7% to aromatics (benzene+toluene). X-ray absorption Cr K-edge fine structure analyses (XANES and EXAFS) and XPS are employed to study the surface structure of the catalyst. Both Cr6+and Cr3+are present on the surface, while the prosperous of Cr6+on the surface is observed. The results demonstrate that the dual-center(mixed oxidation state)/mixed site-symmetric structure—Td-Cr(VI)/Oh-Cr(III) is the catalytic active sites of Na-7.5%Cr/SiO2in SAMCA. A possible catalyst model of double-sites activation mechanism in SAMCA has been tentatively proposed.
The effect of alkaline metal, alkaline-earth metal or rare-earth oxides doping to Pd/γ-Al2O3on the properties of palladium supported catalysts was investigated. It is confirmed that CeO2 and Li2O promoterscan improvesignificantly the activitiesof palladiumsupported catalystsfortheselective reduction of NO with propene in oxidizing atmosphere, and increase the maximum conversions of NO by afactor of 2~4.5. From XRD analysis, Pd/CeO2-Al2O3and Pd/Li2O-Al2O3have the higher Pd dispersion than theothersamples. TPDforNOand O2simultaneousadsorptionon the catalystswere detected by a mass spectrometer, and the results indicate that there are the stronger dissociation adsorption of NO on Pd/CeO2-Al2O3and Pd/Li2O-Al2O3. It is also discussed that the formation of surface adsorption species such as NO, N2O, NO2-and NO3and their desorption properties influence the activities of catalysts for NO selective reduction.
The complexation ofβ-CD with a nonionic surfactant Triton N-101 (TN) has been studied by surface tension measurement and UV-visible spectroscopy. The surface tension curves and apparent critical micelle concentrationsof TN in the presenceofβ-CDare higher than that in the absenceofβ-CD, which indicates that surface activity of TN decrease and formation of micelle is delayed because of the complexation ofβ-CD with TN. To clearly explicate the influences ofβ-CD-TN complexation on changes of surface tension and formation of micelle, the surface tension of fixed concentrations of TN mixed withβ-CD is measured and the influences ofβ-CD on fixed concentrations of TN are discussed. When the concentration of TN is below its CMC, itssurface tension increases withβ-CD concentrations, and then remainsat amaximum. But when the concentrationof TN isabove itsCMC, itssurface tension remains the same asγCMC(surface tensionswhen TN concentrations are above its CMC) firstly, and then it increases withβ-CD concentration, finally remains at a maximum. The association constantsKaofβ-CD-TN system at 298 K are determined by the numerical method based on surface tension measurements that we developed. By measuring surface tensionsofβ-CD-TN systems, the plotsof calculatedS0-[S] value as a function ofS0/[S]orS0/[S]-1 give good straight line, which verified that, as assumed above, the supramolecularsystemstoichiometry is 1∶1 for the inclusion complexation.Kaofβ-CD-TN system at 298 K is calculated from the slope of the straight line and Gibbs free energy change -ΔG0values ofβ-CD-TN systems have also been obtained. The resultsshow thatKadependsonβ-CD concentration, the higher ofβ-CD concentration, the larger ofKavalues. Spectrophotometric titrations have been performed to show the interaction of this supramolecular system. As can be seen from the experiment results, whenβ-CD concentration is lower, the UV absorbance strength at 200, 222, 275 nm decreases with increasingβ-CDconcentration. But when the concentrationofβ-CDreachesat 8.0mmol/L,the absorbance at 275 nm shift to shorter wavelength. On the basis of this observation, we deduce that the hydrophobic chain of TN enterβ-CD cavity mainly whenβ-CD concentration is lower; But whenβ-CD concentration is increased, the phenyl moietyof TN islocated in amore hydrophobic environment, i.e., within the cyclodextrin cavity, rather than in the bulk aqueous solution. The models of the inclusion complexes are also designed based on experimental results.
Both negatively and positively charged colloids (for short, PCS and NCS) with nano-silver particles were prepared. TheNCSwaspreparedbyusing tannic acid asthe reducing agent forAgNO3 and the PCS was prepared by using trisodium citrate as the reducing agent forAgNO3. The surface charge of these two kinds colloidal silver particles was validated by electrophoresis experiment. Surface enhanced Raman scattering (SERS) from fuchsine basic molecules on the two colloids of nano-silver particles were recorded respectively and compared with each other. The resultsshow that there are some obvious differences on the SERSspectrawhen the molecule was adsorbed on the NCS and PCS. On PCS, the in-plane vibrational modes ring skeletal vibration 968cm-1, ring C-H bend 1178 cm-1, N-phenyl stretching 1370 cm-1, Ring C=Cstretching 1588 cm-1were enhanced.On theother hand, on NCS, both the inplane 348, 914, 968, 1178, 1291, 1370, 1520, 1588 cm-1and out-of-plane 1520, 832, 759, 736,423 cm-1were enhanced. It indicates that the fuchsine basic molecule adsorbs on the two kinds of silver surface in different configuration. The molecule adsorbs on the PCS surface vertically, however tilted on the NCS surface.
The study on the interaction of a stain with nucleic acids makes to understand the function of the genetic macromolecules and analyze the transmission of the genetic information. The combination of both the Langmuir adsorptionand the spectral correction techniquewill provide a very helpful experimental strategy for study of chromophore or its metallic complex’s adsorption in surfactant solution. This method is named Micro Phase Adsorption- Spectral Correction (MPASC) was described. It provides a very helpful experimental strategy for study of aggregation of a stain on biomacromolecules. Commonly, nucleic acid molecule contains complex spatial structure. The helix, winding and folds lead of manyholes, gulliesand grooves.Many polar bonds are nearto each other to form many microelectrostatic fields. They will selectively attract charged organic compounds in only monolayer till kinetic equilibrium. So the property constants of the aggregate may be determined such as equilibrium constant, binding ratio, etc. The adsorption of NB on DNA has been investigated at pH=10.38 and it obeyedthe langmuir monolayer adsorption. Results show that the adsorption ratio of NB to DNA(-P) is 3∶1, adsorption constant 3.33×105and real absorptivity 4.81×103L/molcm at 660 nm. By varying the operation condition, we observed that the adsorption ratio of NB to DNA decreased with increase of ionic strength and temperature and addition of ionic surfactant e.g. CTAB and SDBS. This indicates the interaction is an adsorption reaction not a complexation. This interaction has been applied to the quantitative determination of DNA in samples. In the presence of EDTA, many ions or compounds such as C2O42-, protein, acetone, alkali earths, Mn(II), Cu(II), Fe(II), Zn(II), Pb(II), Ni(II), Co(II), Cd(II) and Hg(II) did not interfered the direct determination of DNA. For analysis of samples, the recovery of DNA is between 95.6% and 108% and relative standard deviation 2.8%.
Doping rare earth ion into TiO2has been found to enhance its electrorheological (ER) effect. The typical yield stress is about 5 kPa at 3 kV/mm DC electric field. The thermal character of xerogel and the crystal structure of produced particles are characterized by DSC, TG, FTIR and XRD techniques. The results show that the xerogels of pure and doped TiO2are calcined to form anatase crystalline. Rare earth ions substitute for Ti and cause striking lattice distortion in the suitable range of rare earth content. We contribute the enhancement of ER effect to the influence of rare earth substitution on dielectric properties of TiO2.
Three organic thin film electroluminescence devices (OELD) with different thickness of carriers transport layer: 30nm, 60nm, 120nm and the same thickness of luminescent layer: 300nm, were prepared. The OELDs were the double layer structure of ITO/PVK/Alq/Al. On the basis of a model for generation transport and recombination of carriers and for carrier arbitrary hopping model in organic light emitting devices, a complete analytic function for exciton fission and recombination and for densities distribution of electron and hole are proposed, comparing and analyzing their EL spectra andJ-Vproperties, it is found that the thickness of carrier transport layer influences the brightness, current density and onset volt of EL devices. The theoretical results are in agreement with the experimental values satisfactorily.
A simple long-range-order parameterPis defined for describing the process of formation of chains in the electric field direction. The free energy of the system is taken to be the sum of the internal energy, the electrostatic interaction and configuration entropy as a function o P. Calculated results indicate that the critical parameter is a function of electric field, temperature, misfit dielectric coefficients and concentration of particles.
Perturbation facilitated optical-optical double resonance spectra of Na2from 23Σ+g(ν=15,N=27), 23Πg(ν=11,J=11) and 43Πg(ν=12,J=23) states toa3Σ+uare analyzed using inverse perturbation approach, WKB nodes method and Franck-Condon factor phase method. Electronic potential energy curves for these states and the corresponding electronic transition dipole moments are determined. Spectra thus evaluated are compared with experimental results.