乳状液法制备憎液溶胶 I.BaCO3均匀粒子的制备

Uniform colloidal particles of BaCO3 are produced in the system of n-octanol, BaCl2 and Na2CO3 aqueous solutions under the action of hexadecyltrimethyammonium bromide(CTAB) by the methods of single-emulsion, double-emulsion, solution and gas-blasting. The key factors, which determine the size, shape and uniformity of the particles, as well as the suitable methods to prepare uniform colloidal particles are figured out by comparing different (water-oil) phase ratios, kinetics of particles' growth and different methods of preparing hydrophobic sols.     

Measurement of collision broadening of the P1(5) line of (0,0) band of OH AΣ←XΠ transition at high temperatures

Even for the well-studied and ubiquitous species, OH, the current state of theoretical development of broadening theory does not allow extrapolation from low-temperature laboratory measurements to the range of practical combustion devices. We performed a series of experiments at typical combustion conditions to determine the collision broadening of the P₁(5) line of the (0,0) band of OH A²Σ⁺←X²Π transition by Ar in shock-heated H₂-O₂-Ar mixtures and by air in H₂-air flames over a wide range of stoichiometry (φ=0.01-10.0), temperature (T=780-2440 K), and pressure (p=0.7-10.0 atm). The values of the collision width, Δν_C, were acquired by fitting Voigt profiles to the measured spectral line shapes in flames and to the peak absorption coefficients (k_ν0) in shock tube experiments. Collision broadening parameters (2γ_Ar, 2γ_N2, and 2γ_H2O) were then calculated assuming the linear dependence of Δν_C with pressure—the 2γ_N2 and 2γ_H2O values were inferred from 2γ_Air and the equilibrium concentration of N₂ and H₂O of a given flame. The temperature dependences of 2γ_i in our temperature range are, respectively, 1.0, 0.75, and 0.87 for Ar, N₂, and H₂O. The collision broadening cross sections (σ) deduced from 2γ_i values are expressed with an assumed form, σ_i(T)=σ_i,₀(T₀/T)^k, T₀=1000 K: for Ar, σ_Ar,0=63.3 (Ų), k=0.50; for N₂, σ_N2,0=68.0 (Ų), k=0.25; for H₂O, σ_H2O,0=188.8 (Ų), k=0.37.     

Optimal Cooperative Collision Avoidance Strategy for Coplanar Encounter: Merz’s Solution Revisited

Analytic solutions for optimal collision avoidance strategies are of great importance when setting and validating air traffic rules and as a benchmark when validating automated proximity management and collision avoidance systems. Such a solution for optimal air collision avoidance strategies for a coplanar cooperative encounter between two identical aircraft (or ships) was first presented by Merz (Proc. Joint Automatic Control Conf., Pap. 15-3:449–454, 1973; Navigation 20(2):144–152, 1973). Unfortunately, Merz provided only a very brief indicative justification for his solution. This paper presents a rigorous analysis of the problem. New results include a characterization of a complete set of extremals, justification for optimal strategies and an analysis of the properties of the regions of different optimal strategies. A simple, practical and sufficiently accurate closed form approximation for dispersal curves that partition the plane of initial positions into the regions of different optimal strategies is also presented. We thank the anonymous referees and our colleagues Drs. R.S. Anderssen and R. Jarrett for helpful comments and suggestions.     

Collision operator including large-angle scattering for moderately coupled plasma

A new approach has been developed to treat the large-angle as well as the small-angle binary collisions in high temperature and high density plasmas when the test particle distribution function f_α is even function about the test velocity and the relations of the mass and the velocity between the test particles and the field particles are satisfied with m_αm_β (such as electron–ion collision or Lorentz-gas model) and . With the approach, the Boltzmann collision operator is derived to be suitable for the plasma considered as weakly coupled (Coulomb logarithm ) and moderately coupled , i.e., for the electron–ion coupling constant Γ_ei<0.1. The modified collision operator has a direct and practical connection to the Rosenbluth potentials, the new reduced electron–ion collision operator differs from the original Fokker–Planck operator for Coulomb collisions by terms of order . Moreover, some calculations of relaxation rate and transport properties are given for new reduced electron–ion collision operator that shows corrections.     

Use of SEC–ICP–MS with a collision cell for determining the interaction of chromium with DNA extracted from metal-contaminated soils

The potential of chromium to bind to DNA isolated directly from soil microbial communities was investigated in this study. An analytical scheme was developed to distinguish between chromium bound to DNA and its fragments or chromium contained elsewhere in an environmental DNA extract. DNA was extracted from chromium-contaminated soils and purified using DNA clean-up resins. Size-exclusion chromatography was employed due to its advantages in the separation and molecular weight approximation of large biomolecules. It was coupled with two on-line detection systems (spectrophotometric and inductively coupled plasma mass spectrometric) to study the binding of chromium to DNA or other components in a DNA extract. A collision cell was pressurized with helium to remove diatomic and polyatomic interferents resulting from the chosen mobile phase. Chromium peaks were observed in both the large and small molecular weight regions of the chromatogram; to further confirm that the environmentally extracted DNA contained Cr, the subsequently purified DNA was examined for total Cr using flow injection ICP–MS to accommodate small sample volumes. DNA samples isolated from the two soils examined contained 0.5–0.7 ppb Cr, indicating that DNA isolated directly from a chromium-contaminated soil has chromium bound to the nucleic acids.     

Surface physicochemical properties of Pseudomonas fluorescens and impact on adhesion and transport through porous media

The physiological state of an examined Pseudomonas fluorescens strain had a significant impact on its adhesion to glass surfaces and transport through glass-bead columns. In both batch and column studies collision efficiencies, , for exponential phase cells were much larger (≈2–3) than for stationary or decay phase cells (≈0.5–0.7). Centrifugation of exponential phase cells substantially reduced collision efficiencies (≈0.8). Over the examined range (0.02–0.2 M), ionic strength had no impact on cell attachment. The Lewis acid/base (A/B) character of the cell surface varied with physiological states: exponential phase cells exhibited larger values of the electron–donor parameter of the polar surface tension component, γ_S⁻, than stationary or decay phase cells, resulting in larger calculated cell hydrophilicities. A reduction in exponential phase cell ζ-potential was observed upon centrifugation. Traditional Derjaguin–Landau–Verwey–Overbeek (DLVO) interaction energy profiles (between cells and glass surfaces) indicated energy maxima of the order of 90–130kT, and secondary energy minima of less than 10kT. Extended DLVO modeling predicted infinite energy barriers attributable to repulsive A/B interactions, and similar magnitude secondary energy minima. A pseudo-chemical kinetic approach was used to calculate activation energies of adhesion from experimental collision efficiencies. Collision efficiencies were also predicted from a diffusion-governed mass transport model incorporating interacting force fields. Predicted energy barriers underestimated cell collision efficiencies, suggesting that secondary energy minimum interactions governed initial attachment of cells. The partial reversibility of adhesion upon ionic strength reduction supported the secondary minimum interaction hypothesis.     

N(4S)+ NO(X2Π)→N2(X3Σg-)+O(3P) 反应的立体动力学研究

采用准经典轨线方法研究了在不同碰撞能下，碰撞反应N(4S)+NO(X2Π)→ N2(X3Σg- )+O(3P)在两个最低势能面3A 和 3A'上产物与反应物之间的矢量相关. 结果表明，对于不同的碰撞能，在两个势能面上反应产物的转动取向展示了不同的特征和趋势. 随着碰撞能的增加，发生在3A 势能面上的反应主要受外平面机理支配，而发生在 3A' 势能面上的反应倾向于受内平面机理支配. 这些差异来自于两个势能面的不同构型.     

Elimination of chloride interference on arsenic speciation in ion chromatography inductively coupled mass spectrometry using an octopole collision/reaction system

Anion-exchange chromatography with inductively coupled plasma mass spectrometry (ICP-MS) is often used for the speciation of arsenic (As). In this work, either He or H₂ was introduced to the octopole collision/reaction cell to eliminate chloride (Cl⁻) interferences during As speciation by ICP-MS. Polyatomic species, ⁴⁰Ar³⁵Cl and ³⁸Ar³⁷Cl, which are formed in high chloride matrices interfere with the ICP-MS detection of ⁷⁵As. These interferences were reduced or eliminated by introducing He or H₂ to the collision/reaction cell, with some loss in sensitivity when compared to the standard mode (no gas). For example, the sensitivity of As(V) was 30.4 and 17.7% of that observed in standard mode when introducing He and H₂, respectively. Chloride interference was completely eliminated using a flow rate of 3.0 mL min^− 1 with H₂ as a reaction gas with detection limits in the range of 0.3-0.6 μg L^− 1. The developed method was applied to determination of arsenic species in waters containing high concentrations of chloride by following a simple procedure and without modification of the ICP-MS instrument.     

Analysis of the selenium species distribution in cow blood by size exclusion liquid chromatography–inductively coupled plasma collision cell mass spectrometry (SEC–ICPccMS)

A method for performing rapid semiquantitative screening of the distribution of Se species in the blood of cows fed with a diet enriched in selenized yeast was optimized. The method was based on direct injection of a blood sample onto a high resolution size exclusion chromatographic column and fractionation of the selenium species. Selenium was detected on-line by ICP-MS with a collision cell. The concentrations of selenized haemoglobin and free selenomethionine were estimated using the chromatogram. The method was applied to a study involving 15 control and 15 treated dairy cows at four different supplementation time points. The increase in the selenomethionine and selenized haemoglobin was a linear function of the total selenium concentration. A threshold value of 600 ng ml(-1) of total Se was established beyond which selenomethionine could not be incorporated into the protein. No inorganic selenium was found to be present. The total selenium in cow blood correlated well with that in milk. The selenium supplementation did not change the protein distribution profiles for other essential elements (Cu, Fe, Mn, Zn).