Finite-dimensional approximations for the equation of nonlinear filtering derived in mild form

The Zakai equation for the unnormalized conditional density is derived as a mild stochastic bilinear differential equation on a suitableL ² space. It is assumed that the Markov semigroup corresponding to the state process isC ₀ on such space. This allows the establishment of the existence and uniqueness of the solution by means of general theorems on stochastic differential equations in Hilbert space. Moreover, an easy treatment of convergence conditions can be given for a general class of finite-dimensional approximations, including Galerkin schemes. This is done by using a general continuity result for the solution of a mild stochastic bilinear differential equation on a Hilbert space with respect to the semigroup, the forcing operator, and the initial state, within a suitable topology.     

Mercury extraction by ionic liquids: temperature and alkyl chain length effect

The preliminary results described here show the complete transfer of Hg(II) ions, in the absence of a chelating agent in 1-alkyl-3-methylimidazolium hexafluorophosphate ionic liquids; the lag time required to gain the quantitative metal ion partition turned out to be strongly dependent both on alkyl chain length on the imidazolium ring and on the working temperature.     

Effects of Adsorbed Polyaniline on Redox Process on MoO3 Surface

The effects exhibited by adsorbed conducting polyaniline on the redox process on a molybdenum oxide surface were studied. Thermogravimetric results indicate a 4% polyaniline deposition. Cyclic voltammograms of the adsorbed polymer on MoO3 show that polyaniline exerts remarkable effects on the molybdenum blue oxidation-reduction process, with oxidation and reduction potentials of 0.33 and 0.18 V, respectively. This effect strongly enhances the electrode response, and can be used as an important tool in qualitative and/or quantitative determinations of molybdenum in solution as well as in any substrate. Copyright 1999 Academic Press.     

奥尔堡PBL模式对提升有机波谱分析教学效果的启示

概述了有机波谱分析课程教学中存在的主要问题，介绍了奥尔堡PBL模式的主要特点和优势，分析了将奥尔堡PBL模式用于有机波谱分析课程教学的必要性和可行性，并从课时分配、教学内容、教学方式和考核方式等4方面提出了教学改革方案，旨在提高教学效果。     

Surfactant Hydrogels for the Dispersion of Carbon‐Nanotube‐Based Catalysts

Novel hydrogel phases based on positively charged and zwitterionic surfactants, namely, N‐[p‐(n‐dodecyloxybenzyl)]‐N,N,N‐trimethylammonium bromide (pDOTABr) and p‐dodecyloxybenzyldimethylamine oxide (pDOAO), which combine pristine carbon nanotubes (CNTs), were obtained, thus leading to stable dispersions and enhanced cross‐linked networks. The composite hydrogel featuring a well‐defined nanostructured morphology and an overall positively charged surface was shown to efficiently immobilise a polyanionic and redox‐active tetraruthenium‐substituted polyoxometalate (Ru₄POM) by complementary charge interactions. The resulting hybrid gel has been characterised by electron microscopy techniques, whereas the electrostatic‐directed assembly has been monitored by means of fluorescence spectroscopy and ζ‐potential tests. This protocol offers a straightforward supramolecular strategy for the design of novel aqueous‐based electrocatalytic soft materials, thereby improving the processability of CNTs while tuning their interfacial decoration with multiple catalytic domains. Electrochemical evidence confirms that the activity of the catalyst is preserved within the gel media.     

Effect of ethanol on micellization and on decarboxylation of 6-nitrobenzisoxazole-3-carboxylate in aqueous cationic micelles

The effects of ethanol on the critical micellar concentration (cmc) and the rates of decarboxylation of 6-nitrobenzisoxazole-3-carboxylate (6-NBIC) have been investigated in aqueous cationic surfactants of the cetyltrialkylammonium family with bromide [CT(R)ABr], chloride [CT(R)ACl], and nitrate [CT(R)ANO3] counterions, and methyl (CTAX), n-propyl (CTPAX), and n-butyl (CTBAX) as the head group alkyl moieties. Effects upon cmc and reactivity are similar, featuring a break at the ethanol mole fraction, x(EtOH), of ca. 0.055; these effects have been related to changes in solvent structure, with formation of a clathrate at x(EtOH) = 0.055. Rate data in CTBABr were further investigated and fitting of raw kinetic data to the pseudophase model is possible up to x(EtOH) = 0.1, showing an unexpected decrease of rate constant values in the micellar pseudophase, kM', as ethanol content increases: a significant variation of micellar ionization degree could account for this kinetic effect.     

Effects of Amine Oxide Surfactants on Reactions of Bromide and Hydroxide Ions with Methylnaphthalene-2-Sulfonate

The SN2 reaction of Br- with methylnaphthalene-2-sulfonate (MeONs) in water is accelerated by micelles of tetradecyldialkyl amine oxide (alkyl = methyl, n-propyl) and rates increase sharply in HBr due to increased binding of Br- to the protonated amine oxide. Second-order rate constants at the micellar surface are similar to those at surfaces of trialkylammonium and sulfobetaine micelles. The reaction of OH- with MeONs is weakly inhibited by amine oxide micelles, showing that dispersive, as well as coulombic and charge-dipole, forces play a major role in the association of ions with surfaces of micellar aggregates. Copyright 1999 Academic Press.     

Synthesis of heterocyclic thiosulfonates

[formula: see text] A simple synthesis of heterocyclic thiosulfonates containing indole, indoline, benzoimidazole, and quinoxaline rings is described. The synthesis of these thiosulfonates involves the preparation of the appropriately substituted thiols followed by sulfonylation to give thiosulfonates. The corresponding thiols were prepared in a simple and efficient manner by using a thiocyanation reaction either prior to heterocycle ring formation or after heterocycle ring formation. These thiosulfonates were coupled successfully to the 5,6-dihydropyran-2-one ring to give products that showed excellent HIV protease activity.     

Enantioselective epoxidations of alkenes catalyzed by (salen)Mn(III) in aqueous surfactant systems

An aqueous reaction medium, based on a surfactant solution of diethyltetradecylamine N-oxide (AOE-14), was developed for the enantioselective epoxidation of 1,2-dihydronaphthalene and of various cis-β-alkyl styrenes with increasing hydrophobicity, using bleach as oxidant and the Jacobsen chiral (salen)Mn(III) as catalyst. AOE-14 is able to both solubilize all reactants in water and bind the metal of the salen complex acting as coligand. Its use leads to good yields (>75%) and to ee values ranging from 75% up to 91% even in the case of cis-β-alkyl styrenes where lower cis/trans epoxide ratios are observed. The ratio of surfactant/substrate used is 1:1 or 4:1, much lower than those generally used in the literature.     

Effect of head group size, temperature and counterion specificity on cationic micelles

The critical micelle concentration (cmc) and ionisation degree (α), of micelles of cetyltrimethylammonium bromide (CTABr), cetyltrimethylammonium chloride (CTACl), cetyltripropylammonium bromide (CTPABr) and cetyltripropylammonium chloride (CTPACl) have been measured over a narrow temperature range at 2 degree intervals using electrical conductivity. CTPACl and CTPABr are very soluble in water and were measured in the temperature range 275.15-323.15K. The Krafft temperatures for CTABr and for CTACl are 293.15K and 284.15K, respectively and established a lower temperature limit for our studies on these two surfactants. The cmc vs temperature curves have a smooth minimum near room temperature and α linearly increases with temperature. The changes of cmc and α with temperature are smaller than those associated with the modification of head group size or counterion nature. Using these results, basic thermodynamic quantities associated with the phenomena of micellization have been evaluated. Thermodynamic properties of the surfactant solutions were discussed in terms of temperature dependence of the free energy, enthalpy and entropy of micellization. A close similarity between the effects of change in temperature on protein folding and micellization process appears from the data.