Friction force measurements relevant to de-inking by means of atomic force microscope

In the pulping step of the de-inking process, the ink detaches from the fibers due to shear and physical chemical interaction. In order to get a better understanding of the forces involved between cellulose and ink, the atomic force microscope and the colloidal probe technique have been used in the presence of a model chemical dispersant (hexa-ethyleneglycol mono n-dodecyl ether, C12E6). A cellulose bead was used as the colloidal probe and three different lower surfaces have been used, an alkyd resin, mica and a cellulose sphere. The normal and lateral forces have been measured at a range of nonionic concentrations. It was found that the lateral sliding friction forces deceased with increasing surfactant concentration for both the alkyd resin and mica while no differences were observed for the cellulose surface. In addition, only a very small change in normal force could be detected for the alkyd surface as the concentration changed.     

The C-N rotation barrier of the lithium enolate of acetamide: an ab initio and density functional theory investigation

Semiempirical (PM3), ab initio (HF/6-31+G(d) and MP2/6-31+G(d)), and density functional (pBP/DN) calculations are used to investigate the rotation barrier of the carbon-nitrogen bond in a simple enolate anion: lithium acetamide, 1. For comparison, the amidate anion 2, vinylamine 3, and a simulated dimer 4 were also calculated. In all systems, the barrier to rotation was found to be less than 10 kcal x mol(-1) in agreement with experiment. The correlated calculations show the barrier to be lowest for the anion 2. The results show conjugation effects in 1 and 2 comparable to that in vinylamine 3 and imply that polarization effects are more important than charge transfer in amine conjugation.     

A simple model illustrative of some features of polymer dynamics

A quasi-one-dimensional model for the dynamics of a polymer in dilute solution is described. The diffusion equation in the presence of energy barriers to conformational change is solved approximately for the case of high barriers, by a method closely analogous to the method of configuration interaction in molecular quantum mechanics. The dynamic shear viscosity is calculated in terms of the model and the ultrasonic absorption is discussed.     

The generalized analytic signal

This paper is an explication of the analytic signal in the generalized case, i.e., the analytic signal of a generalized function and of a generalized stochastic process. The contributions of the author are: (1) an L²-theory of distributions which, in the study of the analytic signal, has an advantage over the usual Schwartz-Itô-Gel'fand theory because the Cauchy representation is defined; (2) a proof (Theorem 2.5) that the Schwartz distributions δ, δ⁺, δ^? and ? may be extended to the L₂-case, expressions (Theorems 2.6 and 2.7) for their Hilbert and Fourier transforms in the L₂-case, and expressions (Section 2.1) for their analytic signals; (3) a proof (Theorem 3.3) that an orthogonal L₂-process, and therefore the Fourier transform of a second-order stationary stochastic process (Theorem 3.4), is strictly generalized; (4) a representation theorem (Theorem 3.5) which extends the Itô spectral representation theorem for stationary random distributions to the nonspectral, nonstationary, L₂-case; (5) expressions for the Cauchy representation (Theorem 3.6) and the analytic signal (Theorem 3.7) of an L₂-process; (6) an expression for and the covariance kernel of the analytic signal of white noise (Section 3.4). The word application in the text refers to the application of previously developed concepts.     

Frother/collector interactions in thin froth films and flotation

Aqueous thin film studies and surface tension measurements on a mixed surfactant system consisting of poly(ethylene oxide) (PEO), which was chosen as a model flotation frother, and potassium ethyl xanthate, which was chosen as a model flotation collector, enable the interaction between the two surfactants at the air/solution interface to be elucidated.

For the film containing the non-ionic frother, the interface was charged and addition of low concentrations of xanthate acted as a common electrolyte and reduced the thickness of the film, inducing rupture. However, at high xanthate collector concentrations, the negatively charged xanthate was found to interact with the non-ionic PEO causing an accumulation of negative charge at the air/solution interface. Higher frother concentrations were necessary to produce non-rupturing thin films upon increasing the xanthate concentration.     

On the theory of intermolecular forces between inert gas atoms

The method described by Gordon and Kim and modified by Rae has been further modified to restrict the self-exchange correction to an electron gas composed of the outer shell electrons. Revised results are presented for the interaction potentials between various pairs of inert gas atoms.