Supercritical fluid processing of drug nanoparticles in stable suspension

Significant effort has been directed toward the development of drug formulation and delivery techniques, especially for the drug of no or poor aqueous solubility. Among various strategies to address the solubility issue, the reduction of drug particle sizes to the nanoscale has been identified as a potentially effective and broadly applicable approach. Complementary to traditional methods, supercritical fluid techniques have found unique applications in the production and processing of drug particles. Here we report the application of a newly developed supercritical fluid processing technique, Rapid Expansion of a Supercritical Solution into a Liquid Solvent, to the nanosizing of potent antiparasitic drug Amphotericin B particles. A supercritical carbon dioxide-cosolvent system was used for the solubilization and processing of the drug. The process produced well-dispersed nanoscale Amphotericin B particles suspended in an aqueous solution, and the suspension was intrinsically stable or could be further stabilized in the presence of water-soluble polymers. The properties of the drug nanoparticles were found to be dependent on the type of cosolvent used. The results on the use of dimethyl sulfoxide and methanol as cosolvents and their effects on the properties of nanosized Amphotericin B particles are presented and discussed.     

A new algorithm for zero-modified models applied to citation counts

Scientometrics - In this era of interdisciplinary science, many scientific achievements, such as artificial intelligence (AI), have brought dramatic revolutions to human society. The increasing...     

A generalized continuum theory for multiphase suspension flows

A continuum theory for multiphase particulate suspensions in a fluid media is formulated. The generalized fundamental balance laws for the particulate phases as well as for the continuous suspending fluid phase are presented. The thermodynamics of a multiphase system is studied and the method of Lagrangian multipliers is employed to include the constraints of incompressibility of materials of the constituents and the criterion for fully saturated media. Constitutive equations are developed which include microrotational and microdilatational effects. The basic equations of motion of different phases are derived and discussed. Special considerations are given to the case of incompressible constituents. Examples of applications of the present theory to dilute suspension flows and multiphase sedimentations are also discussed.     

A nanoscale standard for the Seebeck coefficient

The Seebeck coefficient, a key parameter describing a material's thermoelectric performance, is generally difficult to measure, and no intrinsic calibration standard exists. Quantum dots and single electron tunneling devices with sharp transmission resonances spaced by many kT have a material-independent Seebeck coefficient that depends only on the electronic charge and the average device temperature T. Here we propose the use of a quantum dot to create an intrinsic, nanoscale standard for the Seebeck coefficient and discuss its implementation.     

A new power standard for audio-frequency measurements

A thermal power comparator for audio-frequency measurements is presented. It is essentially a double-bridge-type multiplier that consists of two multijunction thermal converters that contain two heaters. Together with a precision inductive voltage divider and current transformer for extending the voltage and current range, the comparator ensured a high-precision power standard with an AC/DC transfer error of less than 15 p.p.m. in the audio-frequency range     

A stable vorticity-velocity formulation for viscous flow analysis

A new least-squares weak form for the Stokes problem is presented. In the proposed formulation, the pressure is separated on the analytical level. It is shown that stability of the separated systems obtained is independent of the Reynolds number, in contrast to the common sensitive coupled or penalty primitive variable formulations. This is achieved for the price of admitting a larger number of variables. The new formulation is particularly suitable when application of operator splitting methods (Bristeau et al. 1985) is considered. It is applicable both to two and to three dimensional situations. Complementary information required for direct implementation to the nonlinear Navier-Stokes problem is given in the appendix.     

A numerical verification for an unconditionally stable FEM for elastodynamics

Numerical results for a time-discontinuous Galerkin space–time finite element formulation for second-order hyperbolic partial differential equations are presented. Discontinuities are allowed at finite, but not fixed, time increments. A method for h-adaptive refinement of the space–time mesh is proposed and demonstrated. Numerical results are presented for linear elastic problems in one space dimension. Numerical verification of unconditional stability, as proven in [7], is rendered. Comparison is made with analytic solutions when available. It is shown that the accuracy of the numerical solution can be increased without a major penalty on computational cost by using an adaptively refined mesh. Results are presented for a type of solid–solid dynamic phase transition problem where the trajectory of a moving surface of discontinuity is tracked.     

A standard rangefinder system

Translated from Izmeritel'naya Tekhnika, No. 5, pp. 15–17, May, 1990.