Adhesive Hard-Sphere Colloidal Dispersions. A Small-Angle Neutron-Scattering Study of Stickiness and the Structure Factor

Small-angle neutron-scattering structure factor measurements were made on sterically stabilized silica spheres dispersed in benzene up to volume fractions of 0.30. Benzene is only a marginal solvent for the stabilizing layer on the surface of the particles. The particles are made attractive by lowering temperature. This attraction is modeled by a square well potential, the depth of which varies with temperature. At the highest temperature studied, our experimental system behaved effectively as an assembly of hard spheres, whereas at the lowest temperature the system approaches a spinodal. Using Baxter's theory we were able to evaluate the interaction parameters and to calculate the structure factor. Experimental structure factors were satisfactorily reproduced over the entire temperature range studied

Charge inversion and colloidal stability of carbon black in battery electrolyte solutions

Colloids and Surfaces A: Physicochemical and Engineering Aspects is an international journal devoted to the science of the fundamentals, engineering fundamentals, and applications of colloidal and interfacial phenomena and processes. The journal aims at publishing research papers of high quality and lasting value. In addition, the journal contains critical review papers by acclaimed experts, brief notes, letters, book reviews, and announcements. Basic areas of interest include the following: theory and experiments on fluid interfaces; adsorption; surface aspects of catalysis; dispersion preparation, characterization and stability; aerosols, foams and emulsions; surfaces forces; micelles and microemulsions; light scattering and spectroscopy; detergency and wetting; thin films, liquid membranes and bilayers; surfactant science; polymer colloids; rheology of colloidal and disperse systems; electrical phenomena in interfacial and disperse systems. These and related areas are rich and broadly applicable to many industrial, biological and agricultural systems. Of interest are applications of colloidal and interfacial phenomena in the following areas: separation processes; materials processing; biological systems (see also companion publication Colloids and Surfaces B: Biointerfaces); environmental and aquatic systems; minerals extraction and metallurgy; paper and pulp production; coal cleaning and processing; oil recovery; household products and cosmetics; pharmaceutical preparations; agricultural, soil and food engineering; chemical and mechanical engineering

Nano-oxidation of silicon surfaces: Comparison of noncontact and contact atomic-force microscopy methods

3 pages, 4 figures.Local oxidation lithography by atomic-force microscopy is emerging as a powerful method for nanometer-scale patterning of surfaces. Here, we perform a comparative study of contact and noncontact atomic-force microscopy (AFM) oxidation experiments. The comparison of height and width dependencies on voltage and pulse duration allows establishing noncontact AFM as the optimum local oxidation method. For the same electrical conditions, noncontact AFM oxides exhibit higher aspect ratios (0.04 vs 0.02). The smallness of the liquid meniscus in noncontact AFM oxidation produces smaller oxide widths. We also report a slower oxidation rate in contact AFM oxidation. We explain this result by introducing an effective energy barrier (~0.14 eV) that includes the mechanical work done by the growing oxide against the cantilever (~0.01 eV).This work was financially supported by the Dirección General de Enseñanza Superior e Investigación (PB98-0471) and the European Commission (GR5D-CT- 2000-00349).Peer reviewe

Linear viscoelastic behavior of aggregated colloidal dispersions

The viscoelastic behavior of a depletion-flocculated dispersion of colloidal spheres is investigated at different volume fractions of the spheres, using a controlled stress and a dynamic rheometer. Combining the results, we obtain the storage G′ and loss G′′ moduli over a frequency range of 0.02<ω<200rad/s. The measured G′ gradually increases with increasing frequency, while G′′ almost remains constant, indicating a broad spectrum of relaxation times. To describe and explain the observed behavior of the moduli as a function of frequency and volume fraction in terms of microscopic parameters, a microrheological model based on the fractal concept is proposed. Comparing experimental results with model calculations, we find a good agreement between the two, with physically plausible parameter values

Математична модель контактного з’єднання метало-пластмасових циліндричних оболонок

We consider alpha scale spaces, a parameterized class (alpha is an element of (0, 1]) of scale space representations beyond the well-established Gaussian scale space, which are generated by the alpha-th power of the minus Laplace operator on a bounded domain using the Neumann boundary condition. The Neumann boundary condition ensures that there is no grey-value flux through the boundary. Thereby no artificial grey-values from outside the image affect the evolution proces, which is the case for the alpha scale spaces on an unbounded domain. Moreover, the connection between the a scale spaces which is not trivial in the unbounded domain case, becomes straightforward: The generator of the Gaussian semigroup extends to a compact, self-adjoint operator on the Hilbert space L-2(Omega) and therefore it has a complete countable set of eigen functions. Taking the alpha-th power of the Gaussian generator simply boils down to taking the alpha-th power of the corresponding eigenvalues. Consequently, all alpha scale spaces have exactly the same eigen-modes and can be implemented simultaneously as scale dependent Fourier series. The only difference between them is the (relative) contribution of each eigen-mode to the evolution proces. By introducing the notion of (non-dimensional) relative scale in each a scale space, we are able to compare the various alpha scale spaces. The case alpha = 0.5, where the generator equals the square root of the minus Laplace operator leads to Poisson scale space, which is at least as interesting as Gaussian scale space and can be extended to a (Clifford) analytic scale space

Description, Host-specificity, and Strain Selectivity of the Dinoflagellate Parasite Parvilucifera sinerae sp.nov. (Perkinsozoa)

17 pages, 7 figures, 2 tablesA new species of parasite, Parvilucifera sinerae sp. nov., isolated froma bloomof the toxic Dinoflagellate Alexandrium minutum in the harbor of Arenys de Mar (Mediterranean Sea, Spain), is described. This species is morphologically, behaviourally, and genetically (18S rDNA sequence) different from Parvilucifera infectans, until now the only species of the genus Parvilucifera to be genetically analyzed. Sequence análisis of the 18S ribosomal DNA supported P. Sinerae as a new species placed within the Perkinsozoa and close to P. infectans. Data on the seasonal occurrence of P. sinerae, its infective rates in natural and laboratory cultures, and intra-species strain-specific Resistance are presented. Life-cycle studies in field simples showed that the dinoflagellate resting zygote (restingcyst) was resistant to infection, but the mobile zygote (planozygote) orpelli clestage (temporary cyst) became infected. The effects of Light and salinity level son the growth of P. sinerae were examined, and the results showed that low salinity levels promote both sporangial germination and higher rates of infection. Our findings on this newly described parasite point to a complex host—parasite interaction and provide valuable information that leads to a reconsideration of the biological strategy to control dinoflagellate blooms by jeans of intentional parasitic infectionsThis research was funded by the EU Project SEED (GOCE-CT-2005-003875). R.I. Figueroa work is supported by a I3P contract and E. Garcés’ work is supported by a Ramon y Cajal grant, both from the Spanish Ministry of Education and SciencePeer reviewe

The economic and accounting content of fixed assets

This book presents a mathematical methodology for image analysis tasks at the edge of current research, including anisotropic diffusion filtering of tensor fields. Instead of specific applications, it explores methodological structures on which they are built.DIPLECS, GARNICS, NACI