53 research outputs found
El Tlacuache Núm. 357 (2009). 357 Año 9 (2009) marzo. El Tlacuache
No full textDe santuarios, globalización y crisis en Morelos por Luis Miguel Morayta Mendoza. - “Supersticiones”, conjuros y seres sobrenaturales por Isabel Garza Gómez. - La modernidad desde la perspectiva de los vecinos de Tetelcingo por Alfredo Paulo Mayya. - Las redes de reciprocidad en la cultura nahua de Santa Catarina por Inés Ayala E., Feliciano García Lara
A simplified approach for solving coagulation–diffusion equation to estimate atmospheric background particle number loading factors contributed by emissions from localized sources
No full textTwo dimensional diffusion theory of trace gas emission into soil chambers for flux measurements
No full textIon densities and particle charges for alpha ionization in an aerosol atmosphere
No full textS.628-640Ionization by alpha sources in an environment containing small aerosol particles is of interest in aerosol neutralizers, particle chargers and atmospheric electricity. It is known that the conventional ion-balance equation is inadequate in describing the bulk ion densities for alpha sources in view of the columnar recombination process. An earlier self-consistent formulation to include this effect is extended to the case of unequal ionic mobilities and the consequent asymmetric charging of particles. Calculations for medium (Radon-222) and low (Thorium-232) energy sources commonly encountered indicate that the columnar recombination corrections lower the ion densities and the particle mean charges by a factor of about 2 for weak sources (strength < 10(3) ions cm (-3) s(-1)) and by a factor of 1.2 for strong sources (Abstract truncated)23Nr.
Variation of the aerosol charge neutralization coefficient in the entire particle size range
No full textStatistical mechanics of equilibrium charging of metallic aerosol particles with free-electrons at elevated temperatures
No full text
Engineering of layered, lipid-encapsulated drug nanoparticles through spray-drying
No full textDrug-containing nanoparticles have been synthesized through the spray-drying of submicron droplet aerosols by using matrix materials such as lipids and biopolymers. Understanding layer formation in composite nanoparticles is essential for the appropriate engineering of particle substructures. The present study developed a droplet-shrinkage model for predicting the solid-phase formation of two non-volatile solutes-stearic acid lipid and a set of drugs, by considering molecular volume and solubility. Nanoparticle formation was simulated to define the parameter space of material properties and process conditions for the formation of a layered structure with the preferential accumulation of the lipid in the outer layer. Moreover, lipid-drug demarcation diagrams representing a set of critical values of ratios of solute properties at which the two solutes precipitate simultaneously were developed. The model was validated through the preparation of stearic acid-isoniazid nanoparticles under controlled processing conditions. The developed model can guide the selection of solvents, lipids, and processing conditions such that drug loading and lipid encapsulation in composite nanoparticles are optimized. (C) 2017 Elsevier B.V. All rights reserved
Air-jet atomization for preparation of lipid nanoparticles: Dependence of size on solute concentration
No full textEngineering nanoparticles for applications such as drug delivery, needs understanding of dependence of particle size on process and precursor parameters. The size of nanoparticles prepared through the aerosol route using solution droplet drying technique is traditionally governed by a 1/3rd scaling law between dry particle diameter and precursor solute concentration. Here, we experimentally investigate this relationship, for precursor solutions of lipids in organic solvents. Nanoparticles were prepared using air-jet atomization of precursor solutions of stearic acid in organic solvents (acetone, chloroform, methanol and ethanol), in a pulse heat aerosol reactor, at a process temperature of 50 °C. The relationship between median mobility diameter of prepared nanoparticles (40–155 nm) and solute concentration was governed by a scaling law exponent (SLE) in the range 0.104–0.182. The observed exponents showed significant deviations from the classical 1/3rd law. The experimental investigation indicated an unexpected increase in particle number concentration with increasing solute concentration for all solvents studied. Simulations with a critical super saturation based solute diffusion model and theoretical calculations of size dependent external factors such as coagulation and wall losses during transit, could not explain the deviation in SLE, nor the increased number concentrations. These considerations point to possible effects of solute concentration on the mechanism of droplet formation during the atomization process. A preliminary model based on an area conservation law has been proposed to explain the twin effects of deviation in SLE and increased droplet number concentration with increasing solute concentration. The present study provides empirical data on the relationship between dry particle diameter and solute concentration in the selected lipid-organic solvent systems. Also, it opens avenues for further understanding nanoparticle formation by air-jet atomization
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