Electron beam induced purification of dilute off gases from industrial processes and automobile tunnels

The electron beam process has proved to be an efficient method for the removal of inorganic pollutants from flue gas. Since it simulates natural processes which occur in the atmospheric photochemistry, it appeared attractive to investigate the potential of the e-beam process to clean off-gases which contain hydrocarbon and inorganic trace components. Such emissions arise from industrial processes and from automobile tunnels. Commercial solvents were vaporized in air and irradiated with energetic electrons (300 keV). CO, CO₂ and aerosol particles were found as products and were determined quantitatively. The aerosol particles can be collected by a gravel bed filter and can be removed by combustion or biological degradation. From experiments and model calculations it was found that the e-beam process is a very economic tool to remove hydrocarbons from large off-gas volumes at initial concentrations of 50–100 mg C/m³, and that NO_x can be removed very efficiently from tunnel off-gas.     

A proton NMR study on aggregation of cationic surfactants in water: effects of the structure of the headgroup

 ¹H NMR chemical shifts of solutions of the following cationic surfactants in D₂O were determined as a function of their concentrations: cetyltrimethylammonium chloride, CTACl, a 1 : 1 molar mixture of CTACl and toluene, cetylpyridinium chloride, CPyCl, cetyldimethylphenylam-monium chloride, CDPhACl, cetyldimethylbenzylammonium chloride, CDBzACl, cetyldimethyl-2-phenylethylammonium chloride, CDPhEtACl, and cetyldimethyl-3-phenylpropylammonium chloride, CDPhPrACl. Plots of observed chemical shifts versus [surfactant] are sigmoidal, and were fitted to a model based on the mass-action law. Satisfactory fitting was obtained for the discrete protons of all surfactants. From these fits, we calculated the equilibrium constant for micelle formation, K, the critical micelle concentration, CMC and the chemical shifts of the monomer, δ_mon and the micelle δ_mic. ¹H NMR-based CMC values are in excellent agreement with those which we determined by surface tension measurements of surfactant solutions in H₂O, allowing for the difference in structure between D₂O and H₂O. Values of K increase as a function of increasing the size of the hydrophilic group, but the free energy of transfer per CH₂ group of the phenylalkyl moiety from bulk water to the micellar interface is approximately constant, 1.9±0.1 kJ mol^-1. Values of (δ_mic–δ_mon) for the surfactant groups at the interface, e.g., CH₃–(CH₂)₁₅–N+(CH₃)₂ and within the micellar core, e.g., CH₃–(CH₂)₁₅–N⁺ were used to probe the (average) conformation of the phenyl group in the interfacial region. The picture that emerges is that the aromatic ring is perpendicular to the interface in CDPhACl and is more or less parallel to it in CDBzACl, CDPhEtACl, and CDPhPrACl. Received: 23 February 1996 Accepted: 29 August 1996     

Cation-crown ether complex formation in water. II. Alkali and alkaline earth cations and 12-crown-4, 15-crown-5, and 18-crown-6

The stability constants and the partial molal volume and isentropic partial molal compressibility changes of complex formation between cations and crown ethers in water at 25°C are presented. The cations involved are Na⁺, K⁺, Rb⁺, Cs⁺, Ca²⁺, and Ba²⁺, and the crown ethers are 12-crown-4, 15-crown-5, and 18-crown-6. Values of V of complex formation have been discussed in terms of two simple models, one based on the scaled particle theory, and the others on the Drude-Nernst continuum model. The results indicate that the charge of the potassium cation in 18-crown-6 is especially well screened from the water. On this basis hydration numbers of complexed cations have been calculated. This shows that the size of the cation compared to the crown ether hole is important for the contacts between complexed cations and water.     

四苯硼酸盐的热化学研究——Ⅱ.一价四苯硼酸盐的标准生成焓

本文用自行建立的精密溶解层热装(?)测定了298.15K时,NH_4BPh_4、KBPH_4、RbBPh_4、CsBPh_4、TlBPh_4、AgBPh_4和HgPh_2七种沉淀反应的反应焓,由此计算了一价四苯硼酸盐的标准生成焓、熵及吉布斯自由能.     

Surface modification of polyethylene terephthalate using PEO-polybutadiene-PEO triblock copolymers

The initial step of thrombus formation on blood-contacting biomaterials is known to be adsorption of blood proteins followed by platelet adhesion. It is generally accepted that surface modification of the biomaterials with poly(ethylene oxide) (PEO) substantially reduces protein adsorption and cell adhesion. Dacron® (polyethylene terephthalate) fabric, which is one of the biomaterials commonly used in blood-contacting devices, was grafted with PEO. A simple two-step procedure for covalent grafting of PEO onto the surface of Dacron® fabric was used. The surface was first treated with PEO-polybutadiene-PEO (PEO-PB-PEO) triblock copolymer, to introduce a layer of double bonds onto the surface. The Dacron® surface was then exposed to a solution of Pluronic® F108 (PF108), a commercially available PEO-poly(propylene oxide)-PEO (PEO-PPO-PEO) triblock copolymer. The surface with two adsorbed layers of PEO-PB-PEO and PF108 was γ-irradiated in the presence of PF108 in the bulk solution for a total radiation dose of 0.8 Mrad. The bulk concentrations of PEO-PB-PEO and PF108 were varied to maximize the efficiency of PEO grafting. Fibrinogen adsorption on PEO-grafted surfaces was reduced more than 90%, compared with that on control surfaces, irrespective of the bulk concentrations of polymers used for grafting. Platelet adhesion was also reduced substantially by PEO grafting. Only a few round platelets were able to adhere to the PEO-grafted surface, while the control surface was fully covered with aggregates of activated platelets. PEO grafting on polyethylene terephthalate using PEO-PB-PEO and PEO-PPO-PEO block copolymers is a simple approach that can be used for various other biomaterials.     

Ternary β-Cyclodextrin Complexes as Models of Allosteric Effects

Two guests reacting with cyclodextrins (CDs) may form ternary complexes, in addition to the common competition of 1:1 complexes. One of the guests can really be included into the cavity of the CD, while the second guest molecule is either inserted close to the first one or attached to the outer surface of the supramolecule by H-bonding. There is a further possibility when the included guest bears a substituent outside the cavity and the second guest can interact with it. The properties of the ternary species formed are highly influenced by the solely (or primarily) included guest. The changes are attributed to the altered properties of the hydrophilic domain of the CD. The phenomena can be proved by NMR data obtained for some binary systems of -CD inclusion complexes and acetic acid and by the stability constants of the ternary complexes formed. Allosteric effects as well as coenzyme/apoenzyme/substrate interactions could be well modelled by these types of CD complexes.     

纳米分辨率的三维形貌检测仪

从光干涉方式，瞳窗关系和光源带宽等基本关系出发，利用空间不变系统理论解析了相移显微干涉检测系统中衍射效应的影响。为了减小横向分辨率对纵向分辨率的影响，利用相关信息提取或数字滤波的方法，获得了纳米分辨率的三维形貌。     

连接基团链长度对季铵盐二聚表面活性剂C12-s-C12·2Br在水溶液中胶团化行为的影响

用电导法、稳态荧光法和粘度法研究了二聚表面活性剂C12-s-C12*2Br分子中的连接基团链长度(s=2, 3, 4, 6)对其在水溶液中聚集行为的影响. 实验发现, C12-s-C12*2Br的胶团生成能力远比其单体C12TABr强得多, 前者cmc值较后者降低一个数量级. 胶团聚集数N随表面活性剂浓度c的增大而增大, 其中当s=2时的N值在c=7.7 mmol/L后开始急剧增大. 计算结果表明, 此时胶团形状发生了明显变化, 形成了椭球形的胶团. 粘度测定结果也证实了这一点.     

CaClH2PO4·H2O的合成及其性质的研究

本文介绍了CaClH_2PO_4·H_2O的合成和纯化的方法。用精密量热计系统测定了CaClH_2PO_4·H_2O的标准生成焓在298.15K时为-2282.34kJ mol~(-1)。评述和讨论了热分解反应的化学动力学性质,测定了分解反应的级数和表现活化能。     

Asymmetric 1,4-addition of β-keto esters to cyclic enones catalyzed by Ru amido complexes

Well-defined Ru amido complexes effected asymmetric Michael addition of β-keto esters to 2-cyclopenten-1-one to give quantitatively the corresponding Michael adducts with excellent ee although with a 1:1 diastereomer ratio. The stereochemical outcome of the reaction was significantly influenced by the structures of the catalysts and the structures of the β-keto esters; the ee value reaching up to 97%.