V. V. Karasev

Evolution of structure and charge of soot aggregates during and after formation in a propane/air diffusion flame

Abstract Evolution of soot aggregate morphology, size and concentration is investigated during and after formation of soot in propane/air diffusion flame. Monitoring of gaseous intermediates in the flame is done by gas chromatography. Soot aggregate size and morphology are analyzed by a transmission electron microscope; soot number concentration is determined by an automated diffusion battery. Aggregate–aggregate collisions and aggregate structural transformations are observed in real time using a video system. It is determined that soot aggregates formed in flame are charged. The electric charge per aggregate is determined by video observation of aggregate movement in electric field. Both positively and negatively charged aggregates are formed. Typical net charge per aggregate is a few elementary units. An effect of soot aggregate restructuring from chain-like to compact structures is observed. It is determined that the driving force for this restructuring is Coulomb interactions between different parts of the aggregate. It is demonstrated that Coulomb interactions between aggregates can affect considerably coagulation process and the final aggregate shape.

Anti-inflammatory Effect from Indomethacin Nanoparticles Inhaled by Male Mice

The respiratory system provides entry for drug nanoparticles to cure systemic diseases. The modern devices that are available on the market of therapeutic aerosol delivery systems have a number of disadvantages. There remains a need for an alternative means that is low cost, convenient, and capable of producing small-sized particles. On the other hand, one-third of the modern drugs are poorly water soluble. Many currently available injectable formulations of such drugs can cause side effects that originate from detergents and other agents used for their solubilization. The aerosol lung administration may by a good way for delivery of the water-insoluble drugs. We present here a new way for the generation of drug nanoparticles suitable for many water insoluble substances based on the evaporation-condensation route. In this paper the indomethacin nanoaerosol formation was studied and its anti-inflammatory effect to the outbred male mice was examined. The evaporation-condensation aerosol generator consisted of a horizontal cylindrical quartz tube with an outer heater. Argon flow was supplied to the inlet and the aerosol was formed at the outlet. The particle mean diameter and number concentration were varied in the ranges 3 to 200 nm and 10(3) to 10(7) cm(-3), respectively. The liquid chromatography and X-ray diffraction methods have shown the nanoparticles consist of the amorphous phase indomethacin. The aerosol lung administration experiments were carried out in the whole-body exposure chamber. Both the lung deposited dose and the particle deposition efficiency were determined as a function of the mean particle diameter for mice being housed into the nose-only exposure chambers. The anti-inflammatory action and side pulmonary effects caused by the inhalation of indomethacin nanoparticles were investigated. It was found that the aerosol administration was much more effective than the peroral treatment. The aerosol route required a therapeutic dose six orders of magnitude less than that for peroral administration.

Analgesic Effect from Ibuprofen Nanoparticles Inhaled by Male Mice

BACKGROUND Aerosol lung administration is a convenient way to deliver water-insoluble or poorly soluble drugs, provided that small-sized particles are generated. Here, for the outbred male mice, we show that the pulmonary administration of ibuprofen nanoparticles requires a dose that is three to five orders of magnitude less than that for the orally delivered particles at the same analgesic effect. METHOD The aerosol evaporation-condensation generator consisted of a horizontal cylindrical quartz tube with an outer heater. Argon flow was supplied to the inlet and aerosol was formed at the outlet. The particle mean diameter and number concentration varied from 10 to 100 nm and 10(3)-10(7) cm(-)3, respectively. The analgesic action and side pulmonary effects caused by the inhalation of ibuprofen nanoparticles were investigated. RESULTS The chemical composition of aerosol particles was shown to be identical with the maternal drug. Using the nose-only exposure chambers, the mice lung deposition efficiency was evaluated as a function of the particle diameter. CONCLUSIONS The dose-dependent analgesic effect of aerosolized ibuprofen was studied in comparison with the oral treatment. It was found that the dose for aerosol treatment is three to five orders of magnitude less than that required for oral treatment at the same analgesic effect. Accompanying effects were moderate venous hyperemia and some emphysematous signs.

Laboratory and field tests of a novel three-stage personal dust sampler for sampling three dust fractions simultaneously

This study designed and calibrated a novel three-stage personal dust sampler for sampling inhalable, thoracic, and respirable dust fractions simultaneously. The sampler has an annular inlet as the first stage for inhalable dust sampling, two impactors in the second and third stages to classify thoracic and respirable dusts, respectively, and a final filter. Laboratory calibration tests using monodisperse liquid and solid particles showed that with 100 ppi (pores per inch) PUF (porous polyurethane foam) substrates and at the flow rate of 3.2 L/min, the sampling efficiency curves of both impactor stages matched with the ISO/CEN/ACGIH thoracic and respirable sampling criteria, respectively. The sampler also agreed with the inhalable criterion for particles smaller than 17 μ m while the deviation increases with increasing particle diameter with a maximum of 28% for 27 μ m particles. It was also found that collection efficiency curve for solid particles was similar to that of liquid particles, indicating that there was no solid particle bounce from the PUF substrates for both impactors. This study also compared inhalable, thoracic, and respirable dust concentrations measured by the present three-stage personal dust samplers with those of the Respicon samplers at three different workplaces. Without using a correction factor of 1.5 for the extrathoracic dusts of the Respicon, field results showed that the present three-stage sampler measured three dust fractions comparable to those of the Respicon samplers. The inhalable dust concentrations of the two samplers differed within 5% while the thoracic and respirable concentration differed by less than 22%.

Formation of electrical dipoles during agglomeration of uncharged particles of hydrogenated silicon

Abstract A new phenomenon of the formation of agglomerates having electric dipoles by agglomeration of originally uncharged aerosol particles is reported. The aerosol particles of hydrogenated silicon are formed via silane pyrolysis in a flow reactor. The size and morphology of agglomerates were analyzed by a transmission electron microscope. The agglomerate radius increased from 0.3 to 6 μm with the coagulation time increasing from 0.1 to 200 s (for T=873 K ). The mass M of these agglomerates is connected with the radius R via the equation M ( g )=8.5×10 −14 ×[ R (μm)] 1.65 . An imaging system coupled with a TV setup was used for direct observation of agglomerate coagulation and investigation of agglomerate movement in the electric field. The experimental results testify that the agglomerates are electric dipoles. It is suggested that this dipole moment arises due to the difference in Fermi energy of primary particles. The dipole moment is ∼3.5×10 −12 (units of CGSE) for the agglomerates with the radius R∼0.5 μm (T=873 K ) . This dipole moment corresponds to the Fermi energy difference for coagulating particles ∼0.08 V .

A study of sulfur homogeneous nucleation from supersaturated vapor. Determination of surface tension of sulfur nanoparticles

Homogeneous nucleation in sulfur vapor is studied in a laminar-flow chamber. Concentration and size distribution of resulting aerosol particles are measured with a diffusion spectrometer of aerosols and a PK.GTA-0,3-002 photoelectric particle counter. The crystal structure of the formed particles is studied by X-ray diffraction analysis. The rate of sulfur evaporation from a boat and the profile of a deposit on the chamber wall along the axial coordinate are determined by gravimetry. Axial and radial temperature profiles are measured using a chromel-alumel thermocouple. The vapor concentration distribution in the chamber is found and the supersaturation is calculated from the solution of the mass-transfer problem. An experimental low-laborious method is developed for the supersaturation cutoff. This method enables one to rapidly deter-mine the position of the zone in which the nucleation proceeds at the highest rate. The position of the zone of nucleation found by this method is in good agreement with the results of calculations based on experimental data and theoretical calculation of the rate of nucleation by an exact formula that has been recently derived based on the works by Kusaka and Reiss, as well as the Frenkel liquid kinetics theory. The surface tension of critical sulfur nuclei resulting from the nucleation is calculated based on this formula and experimental data on the nucleation. It is established that, in a temperature range of 312–319 K, the critical nuclei have tension surface radius Rs ∼ 10.6 Å and surface tension σ = 72.5 ± 1.1 dyn/cm. The surface tension of critical sulfur nuclei in this temperature range is constant and approximately 5% higher than that of a planar surface.

Photochemical Behavior and Photolysis of Protonated Forms of Levofloxacin

The effect of intermolecular proton transfer on the spectral properties of levofloxacin in the ground and excited electronic states was studied. The preferred direction of possible protolytic reactions induced by UV irradiation in this compound was studied. It was found that the proton transfer processes have a considerable effect on the capability of the compound to emit light and occur on the nanosecond timescale. The photochemical reactions of the tree forms of levofloxacin (pH: 4.0, 7.0, 10.0) were studied by laser flash photolysis and product studies. Irradiation at pH 4 yielded a pulse and transient (λmax = 395, 515, 575 nm) assigned to the protonated triplet. Irradiation at pH 7 yielded a transient species (λmax = 525, 610 nm) assigned to the neutral form. Protonation of the anionic singlet excited state was also observed (λmax = 440, 570, 680 nm).

Homogeneous Nucleation from a Supersaturated Sulfur Vapor in a Laminar Flow Diffusion Chamber

ISSN 00125016, Doklady Physical Chemis try, 2011, Vol. 437, Part 1, pp. 31–34.

Study of Sulfur Heterogeneous Nucleation from Supersaturated Vapor on Tungsten Oxide and Sodium Chloride Seed Particles. Determination of Contact Angle of Critical Sulfur Nuclei

A procedure has been developed for determining the contact angle of a critical nucleus formed on seed particles during the heterogeneous nucleation of a vapor in a flow chamber. The procedure comprises the determination of the fraction of enlarged particles, as well as the selective separation of nanoparticles over sizes to locate the zone of intense nucleation. The concentration and size distribution of aerosol particles have been measured with a diffusion spectrometer of aerosols. Vapor concentration distributions and supersaturation fields have been determined by solving the mass-transfer problem. The calculated supersaturation fields are in good agreement with the location of the intense nucleation zone experimentally found with the help of selective separation. The fractions of enlarged particles have been determined as functions of supersaturation in the chamber. A formula has been derived for calculating the fraction and size distribution function of enlarged particles at known supersaturation and temperature fields and a preset contact angle. The contact angles are selected in a manner such that the calculated fraction of enlarged particles coincides with that measured experimentally. It has been revealed that the contact angle of critical sulfur nuclei formed on tungsten oxide seed particles with average radii 〈Rp〉 ≈ 5.8−4.4 nm is in a range of 21.2−20.5°, while, in the case of sodium chloride seed particles with 〈Rp〉 ≈ 6.0−4.4 nm, the contact angle is 20.4−17.4°. The size of a critical nucleus has been found to be proportional to calculated average radius of a seed particle 〈Rp〉 in both cases.

A study of homogeneous nucleation of ibuprofen in a flow chamber. Determination of the surface tension of critical nuclei

Homogeneous nucleation of ibuprofen vapor is studied in a nucleation flow chamber, a horizontal quartz tube equipped with an external heater. The area of the chamber where the nucleation proceeds most efficiently is determined, and the volume of this area is estimated. The temperature and supersaturation are determined and the homogeneous nucleation rate is calculated for this area. Saturation vapor pressure over liquid ibuprofen is measured in a temperature range of 353–383 K. Using an exact formula that has recently been derived for the nucleation rate based on the works by Kusaka, Reiss, as well as the Frenkel liquid-kinetics theory, surface tension and the radius of surface of tension of a critical nucleus σ= 25.9 mN/m and Rs = 1.6 nm, respectively, are calculated at 318 K. The measurement of the surface tension of an ibuprofen planar surface shows that, at 318 K, σ∞ = 24.38 mN/m; i.e., σ is higher than σ∞ by 6%. A critical nucleus is established as containing nearly 36 ibuprofen molecules.