Electrostatic interactions between diffuse soft multi-layered (bio)particles: beyond Debye-Hückel approximation and Deryagin formulation

We report a steady-state theory for the evaluation of electrostatic interactions between identical or dissimilar spherical soft multi-layered (bio)particles, e.g. microgels or microorganisms. These generally consist of a rigid core surrounded by concentric ion-permeable layers that may differ in thickness, soft material density, chemical composition and degree of dissociation for the ionogenic groups. The formalism allows the account of diffuse interphases where distributions of ionogenic groups from one layer to the other are position-dependent. The model is valid for any number of ion-permeable layers around the core of the interacting soft particles and covers all limiting situations in terms of nature of interacting particles, i.e. homo- and hetero-interactions between hard, soft or entirely porous colloids. The theory is based on a rigorous numerical solution of the non-linearized Poisson-Boltzmann equation including radial and angular distortions of the electric field distribution within and outside the interacting soft particles in approach. The Gibbs energy of electrostatic interaction is obtained from a general expression derived following the method by Verwey and Overbeek based on appropriate electric double layer charging mechanisms. Original analytical solutions are provided here for cases where interaction takes place between soft multi-layered particles whose size and charge density are in line with Deryagin treatment and Debye-Hückel approximation. These situations include interactions between hard and soft particles, hard plate and soft particle or soft plate and soft particle. The flexibility of the formalism is highlighted by the discussion of few situations which clearly illustrate that electrostatic interaction between multi-layered particles may be partly or predominantly governed by potential distribution within the most internal layers. A major consequence is that both amplitude and sign of Gibbs electrostatic interaction energy may dramatically change depending on the interplay between characteristic Debye length, thickness of ion-permeable layers and their respective protolytic features (e.g. location, magnitude and sign of charge density). This formalism extends a recent model by Ohshima which is strictly limited to interaction between soft mono-shell particles within Deryagin and Debye-Hückel approximations under conditions where ionizable sites are completely dissociated.     

Quantitation of p-aminohippuric acid in biological fluids by high-performance liquid chromatography and dual-wavelength ultraviolet detection

A modification of the method of Verbeke [J. Chromatogr., 177 (1979) 69] is presented. The fatty tissue is dissolved in hexane, partitioned against methanol-sodium acetate buffer (pH 5.2) and extracted with dichloromethane. The crude extract is then purified on a disposable C18 column. The final extract together with a set of reference compounds is spotted on two opposite sides of a high-performance thin-layer chromatographic plate (10 X 10 cm), which is developed with two different eluents in two opposite directions. This mode of operation has the advantage that more reference compounds can be spotted and that the identification is based on two independent chromatographic runs. Also the total analysis time is decreased.     

The determination of the D-state asymptotic normalization of the deuteron and triton wavefunctions by the continuation of the 2H(b, p)3H tensor polarizations

By continuation of 14 tensor polarizations to the stripping and pick-up poles of the ²H($\text{d}$,p)³H reaction we have determined ?_D values for the deuteron and triton wavefunctions. The new precision value for the deuteron 0.0272 ± 0.004 suggests an increase of the applied strength of the OPE potentials. For the triton a value of 0.051±0.005 was found.     

Ortho-lithiation of triphenylphosphonio-methylid and,also, triphenylphosphine oxide

While upon treatment with methyl- or butyllithium triphenylphosphonio-methylid ( 1 ) undergoes extensive ligand exchange (leading to 4) it reacts with sec- or tert-butyllithium mainly at the ortho-position exchanging one hydrogen against a lithium atom (to give 3).     

A Case Study on the Development of the Home Defence Training Game HOT SEAT

Home defence is concerned with enhancing the prospects for survival and recovery of this country in the eventuality of nuclear war. Contingency plans exist for the creation of a system of wartime regional government which includes elements from peacetime local and central governments. Senior officers in local government with designated wartime roles receive training at the Home Defence College. The Home Office decided that a crisis management game should form part of their overall programme of indoctrination. The resulting game, which is known as HOT SEAT, has been successfully implemented and is now in regular use at the College. This paper describes how the need for the game arose, the structure of the resulting game, the problems that arose during its development, and should be of interest to those concerned with the development of management and crisis games.     

Hydrogen bonding incis-2,3-epoxycyclooctanol

Hydrogen bonding and the electron-withdrawing or electron-donating characteristics of substituent groups that are neighboring to epoxide groups can affect the reactivity of the epoxide ring. The crystal structure ofcis-2,3-epoxycyclooctanol has been determined as a saturated eight-membered ring compound in which a hydroxyl group is attached to the C(1) atom that is adjacent to a 2,3-fused epoxy ring. The findings are that the longer epoxide C-O bond (and hence the one expected to be more readily broken) is the one farther from the hydroxyl group [1.462(1) å versus 1.447(1) å] and that the optimal hydrogen bonding is to an adjacent molecule radier than within the molecule. The shortest C-C bond is that of the epoxide group; the bond adjacent to it (on the side farther from the hydroxyl group) is the next shortest.