Results 1 - 10 of 18008
Results 1 - 10 of 18008. Search took: 0.041 seconds
|Sort by: date | relevance|
[en] We have developed the self-consistent mean rate approach that makes it possible to analytically solve the coagulation–fragmentation balance equations subject to the mass conservation constraint. The developed approach is not restricted to a specific form of the coagulation and fragmentation rates, thus being applicable to a variety of different coagulation–fragmentation processes. As an example of the practical applicability of the developed method we have calculated the aggregate size distribution and average aggregate diameter for the case of shear induced coagulation–fragmentation
[en] We have used a variety of different applied fields to control the density, growth, and structure of colloidal crystals. Gravity exerts a body force proportional to the buoyant mass and in equilibrium produces a height-dependent concentration profile. A similar body force can be obtained with electric fields on charged particles (electrophoresis), a temperature gradient on all particles, or an electric field gradient on uncharged particles (dielectrophoresis). The last is particularly interesting since its magnitude and sign can be changed by tuning the applied frequency. We study these effects in bulk (making 'dielectrophoretic bottles' or traps), to control concentration profiles during nucleation and growth and near surfaces. We also study control of non-spherical and optically anisotropic particles with the light field from laser tweezers
[en] A complex mathematical model of processes of plant nutrition from a special regulated gas medium containing nanoparticles of basic macro- and microelements is formulated. The variation of the number of nanoparticles and the variation of the total nanoparticle volume with time, which form during the cooling process of the initial gas mixture, were investigated. The calculations of the structures, compositions and shapes of nanoparticles and the movement of nanoparticles were carried out
[en] In this paper, we report a new method for size-based capturing of suspended particles by a specially designed micro fluidic structure named 'vernier walls'. A number of particles in suspension can be captured based on their sizes by a series of gaps between the closest walls, one standing on the ceiling and the other on the bottom of a wide microfluidic channel. The dimensions of the gaps narrow stepwise along the flow direction with a fixed step size per gap, which can be determined according to the required capturing resolution. Particles are captured based on their sizes in a line along each of the gaps with their corresponding dimensions. A part of the wide channel works as a bypass area, where the gap is constant to avoid clogging, letting the excess number of particles go through the channel. To realize the proposed structure, a new device assembly method has also been developed adopting planar gear-shaped structures surrounding the microfluidic channel solely for the fine and easy alignment of the narrowing gaps. The performance of the present method was evaluated using a device designed and fabricated for size-based capturing with a 5 µm resolution, and it was demonstrated that three kinds of particles with diameters from 10 to 26 µm were successfully captured by size. Additionally, we confirmed that the capturing rate was no less than 20% under the experimental condition. The present method can be used as a basic tool for handling particles with certain ranges of sizes.
[en] The magnetically induced yield stress in a sample of suspension of magnetic particles is associated with formation of a field-oriented structure, the strength of which depends on the degree of particles magnetization. This factor is largely defined by the actual magnetic field strength in the sample. At the same time it is common practice to present and analyze magnetorheological characteristics as a function of the applied magnetic field. Uncertainty of an influence function in magnetorheology hampers interpretation of data obtained with different measurement configurations. It was shown in this paper that rheological response of magnetorheological fluid to the applied magnetic field is defined by the sample's actual (internal) magnetic field intensity, which, in turn, depends on sample geometry and field orientation all other factors being equal. Utilization of the sample's actual field as an influence function in magnetorheology allows proper interpretation of data obtained with different measuring system configurations. Optimization of the actual internal field is a promising approach in designing of energy efficient magnetorheological devices.
[en] Mathematical structural invariants and quantum theoretical descriptors have been used extensively in quantitative structure-activity relationships (QSARs) for the estimation of pharmaceutical activities, biological properties, physicochemical properties, and the toxicities of chemicals. Recently our research team has explored the relative importance of various levels of chemodescriptors, i.e., topostructural, topochemical, geometrical, and quantum theoretical descriptors, in property estimation. This study examines the contribution of chemodescriptors ranging from topostructural to quantum theoretic calculations up to the Gaussian STO-3G level in the prediction of the toxicity of a set of twenty halocarbons. We also report the results of experimental cell-level toxicity studies on these twenty halocarbons to validate our models
[en] Brief descriptions are given for three research areas: transport properties of multicomponent fluid mixtures, fluctuations in a Rayleigh-Benard cell, and light and neutron scattering of simple fluids
[en] We discuss fast frictionless cooling techniques in the framework of sympathetic cooling of cold atomic mixtures. It is argued that optimal cooling of an atomic species--in which the deepest quantum degeneracy regime is achieved--may be obtained by means of sympathetic cooling with another species whose trapping frequency is dynamically changed to maintain constancy of the Lewis-Riesenfeld adiabatic invariant. Advantages and limitations of this cooling strategy are discussed, with particular regard to the possibility of cooling Fermi gases to a deeper degenerate regime.
[en] We consider a dilute atomic gas of two species of fermions with unequal concentrations under a Feshbach resonance. We find that the system can have distinct properties due to the unbound fermions. The uniform state is stable only when either (a) beyond a critical coupling strength, where it is a gapless superfluid, or (b) when the coupling strength is sufficiently weak, where it is a normal Fermi gas mixture. Phase transition(s) must therefore occur when the resonance is crossed, in contrast to the equal population case where a smooth crossover takes place