Low Deposition Efficiency Research Articles

A new methodology for targeting drug-aerosols in the human respiratory system

Inhalation of medicine for the treatment of lung and other diseases is becoming more and more a preferred option when compared to injection or oral intake. Unfortunately, existing devices such as the popular pressurized metered dose inhalers and dry powder inhalers have rather low deposition efficiencies and their drug-aerosol deliveries are non-directional. This is acceptable when the medicine is inexpensive and does not cause systemic side effects, as it may be the case for patients with mild asthma. However, the delivery of aggressive chemicals, or expensive insulin, vaccines and genetic material embedded in porous particles or droplets requires optimal targeting of such inhaled drug-aerosols to predetermined lung areas. The new methodology introduces the idea of a controlled air-particle stream which provides maximum, patient-specific drug-aerosol deposition based on optimal particle diameter and density, inhalation waveform, and particle-release position. The efficacy of the new methodology is demonstrated with experimentally validated computer simulations of two-phase flow in a human oral airway model with two different sets of tracheobronchial airways. Physical insight to the dynamics of the controlled air-particle stream is provided as well.

Deposition of Aerosolized Particles in the Maxillary Sinuses before and after Endoscopic Sinus Surgery

Recent studies suggest that topical therapy is beneficial in many conditions underlying chronic sinusitis. Current literature has documented low aerosolized particle deposition efficiency into the paranasal sinuses. Mathematical modeling suggests that three factors influence the deposition efficiency: particle size, pressure gradient, and size of the sinus ostium. Ostium size is the most dominant factor. Therefore, we sought to determine if maxillary antrostomy and ethmoidectomy would increase the deposition efficiency. Five cadavers underwent pre- and postoperative scintigraphy after administration of aerosolized Tc-99M. Images were obtained with a gamma-camera and regions of interest (ROIs) were drawn around the maxillary sinuses. Counts per minute in the pre- and postoperative ROIs were then compared using the paired t-test. Results indicated a significant increase in deposition of radioactivity in the maxillary sinuses in the postoperative state (p < 0.01). Topical therapy for chronic sinusitis may be more feasible in the postoperative population.

Driving forces for ammonia fluxes over mixed forest subjected to high deposition loads

Ammonia exchange was measured over a mixed suburban forest near a rural area. An average net ammonia flux of −90 ng m −2 s −1 was measured with corresponding concentration ([NH 3 ]) and deposition velocity of 4.1±6.5 μg m −3 and 3.0±4.6 cm s −1 , respectively. Subdivision into categories of day/nighttime, wind sector and canopy wetness helped explain fluxes and concentrations. Net fluxes were approximately double for the wind sector exposed to high ammonia levels and during the day. To a certain extent, fluxes ( F ) followed the maximum flux permitted by turbulent transfer ( F max ), which was the highest for a dry canopy. When expressed as relative deposition flux ( F / F max x ), a wetted canopy seemed to be a more efficient sink than a dry one, especially at nighttime (20–80% increase compared to dry canopy). Of the net fluxes, 14% represented emission. Emission fluxes occurred mainly during daytime and were important in magnitude for the high [NH 3 ] wind sector. Emission episodes generally occurred at low ammonia concentrations although high concentrations during dry, warm episodes were also associated with emission events. The lower deposition efficiency and higher canopy resistance ( R c ) at high ammonia levels and at night were indicative of the reduced capacity for leaf surface to retain ammonia, especially when the canopy was dry. It was found that relative humidity (RH) and temperature ( T ) strongly codetermined the sink strength of the canopy. A warm and humid atmosphere favoured ammonia uptake while conditions with low RH and T impeded rapid canopy uptake, especially at high ammonia levels. Strong interactions between RH and T with the (NH 3 /SO 2 ) molar ratio occurred for certain categories of canopy wetness and day/nighttime. Canopy uptake was further optimized when this ratio was maintained within a certain range.

Numerical Heat and Fluid-Flow Modeling of the Panorama Volcanic-Hosted Massive Sulfide District, Western Australia

Exceptional exposure of the Archean Pilbara block in Western Australia reveals a cross section through an Archean massive sulfide-hosting volcanic succession with underlying subvolcanic intrusion in the Panorama district. A numerical model based on available detailed geologic information has been constructed to simulate heat and fluid flow in the Panorama district. The modeling provides insight into the evolution of the hydrothermal system and evaluates key geologic parameters and their influence on fluid-flow, hydrothermal circulation, and the genesis of massive sulfide orebodies. The model simulates important aspects of the Panorama massive sulfide district, such as temperature distribution, relative alteration zonation, and the size and distribution of orebodies. Predicted temperatures ranging from 150oC at the top of the volcanic pile to ~400oC at the andesite-diorite interface are comparable to temperature estimates based on previously published oxygen isotope mapping. Modeled fluid discharge temperatures are highest for the Sulphur Springs deposit (300o–400oC) and lower for the Kangaroo Caves and other deposits (250o–350oC). The most favorable conditions to reproduce the orebodies and their related alteration zonation occur at anisotropic rock permeabilities comparable to the upper oceanic crust (10–15–10–14 m2) and higher fault permeabilities (10–14–10–13 m2) with a specific fault arrangement similar to that mapped in the field. The 4.6 million metric tons (Mt) Sulphur Springs orebody is predicted to form in less than 5,000 yr, assuming a hydrothermal fluid with seawater salinity, 10 ppm base metal concentration, and a low deposition efficiency (≤10%); other deposits form above the faults under similar conditions. A large range of base metal concentrations in the fluids can account for the known orebodies, but high temperatures (≥250oC) and high-flow velocities (>10–7 m/s) are necessary to produce the observed alteration patterns and distribution of ore deposits. Results indicate that the establishment of a significant hydrothermal system capable of forming economic massive sulfide deposits is favored in fresh volcanic rock packages that have not been affected by earlier compaction or alteration. Under these conditions, economic massive sulfide orebodies (>5 Mt of 10% Zn + Cu) may form in a few thousand years, although the overall lifespan of the hydrothermal system may be between 30,000 and ~200,000 yr, depending on the variations in rock and fault permeability with time.

Plasma deposition of boron films with high growth rate and efficiency using carborane

The injection of carborane (C 2B 10H 12) on the PISCES-B linear plasma device has been used to produce boron containing films on various target species. Film growth rates achieved are extremely high (up to 30 nm/s) compared to those typically found for glow discharges (∼0.01 nm/s). For low- Z target materials (C and Al) the film production is highly efficient, with the boron film growth rate comparable to the incident ion flux and the injection rate of boron atoms. The boron to carbon ratio is 3.0–3.6 for these films. Similarly high growth rates (∼10 nm/s) are obtained with high- Z target (W), but with lower deposition efficiency and higher B/C film ratio. The high film growth rate/efficiency are apparently linked to the high degree of carborane ionization and dissociation caused by the ∼40 eV PISCES-B plasma, compared with T<1 eV plasmas of glow discharges. This technique opens the possibility of continuously producing protective B films in thermonuclear devices where net erosion rates approach 10 nm/s.

Sorption nonequilibrium effects on colloid-enhanced transport of hydrophobic organic compounds in porous media

This paper presents the results of modelling and experimental investigations of factors affecting enhanced transport of hydrophobic organic compounds (HOCs) on colloids in porous media, especially effects of nonequilibrium sorption/desorption. Simulations were performed with a model that considers equilibrium and rate-limited exchange of contaminant between the true dissolved phase, the suspended and attached colloids, and the fixed solid phase as well as the advection, dispersion, deposition, and release of colloidal particles from the porous medium. The model was also applied to laboratory column data for colloid-facilitated transport of a common HOC, phenanthrene. Simulations of colloid-enhanced transport and fitting of experimental data indicated that colloid-enhancement of hydrophobic organic contaminant transport can be significant for sufficiently high colloid concentrations, a high partition coefficient of contaminant on colloids with respect to the fixed porous medium, a low deposition efficiency of the colloids on the fixed porous medium surfaces, and a slow desorption rate of contaminant from the colloids. The last of these conditions was identified as probably the most important in enhancing transport distances of contaminants in natural systems with mobile colloids which usually occur at concentrations not exceeding a few mg/l.

Studies on plasma edge transport and layer deposition by local injection of reactive gases during TEXTOR-94 discharges

To study local particle transport, silane was injected through a hole in a test limiter surface during discharges in TEXTOR-94. The gas injection lead to the deposition of a thin layer around the injection hole which was close to the area of the highest heat load. The layer was eroded in discharges without silane injection. The layer was not only formed by the injected silicon but also by a large amount of carbon which must originate from other plasma facing components. The preferential direction (symmetry line) of the deposition pattern is tilted by ∼ 25° relative to the magnetic field lines Calculations with the ERO-TEXTOR code recover the general shape of the Si-deposition pattern. To get accordance between the calculations and the experimental results a strong electric field parallel to B and a sticking coefficient much smaller than 1 has to be considered to reproduce the low silicon deposition efficiency, whereas the tilting of the symmetry line can be explained by the existence of a radial electric field.

Electrochemical copolymerization of aniline and aniline-2,5-disulfonic acid

Electrochemical copolymerization of aniline and aniline-2,5-disulfonic acid (ADSA) was carried out in HCl solutions. The presence of ADSA inhibited significantly the growth of polyaniline (PAn), although the voltammetry of the copolymer was still similar to that of conventional PAn. As the ADSA concentration increased, the deposition rate of the copolymer decreased rapidly and finally no solid film was deposited on the electrode surface. When the ADSA concentration was lower than ~ 5 mM, the depression effect of ADSA on the growth rate of the copolymer is mainly due to its stronger adsorption at the electrode surface. For higher ADSA concentrations, the inhibiting effect of ADSA was dominated by its termination effects, which led to more soluble oligomers and in turn resulted in lower deposition efficiency. Electrolysis of ADSA solution might result in a water-soluble fully sulfonated PAn.

In-Situ and Ex-Situ Monitoring of Electrochemical Deposition of Silver Using Quartz Crystal Resonators

Abstract Electrochemical deposition of silver from a 1 mM AgNO3 aqueous acidic solution at 20 μA cm−2 was monitored by means of in-situ quartz crystal impedance (QCI) technique, in-situ quartz crystal microbalance (QCM) technique, ex-situ QCI technique and atomic absorption spectroscopy. However, the mass evaluated from the data obtained in the in-situ QCI and QCM measurements on the basis of Sauerbrey equation deviated from intrinsic mass of the deposited silver because of a low deposition efficiency, liquid viscously or rigidly coupled with the resonator and/or stress generated in the deposited layer. Thus one must pay attention to these factors when one calibrates a quartz crystal microbalance on the basis of electrochemical deposition of a metal. In-situ QCI method utilizing a network analyzer is shown to be a powerful technique for simultaneous and qualitative monitoring of mass and surface structure changes. For the quantitative mass measurements, the mass sensitivity must be calibrated using another direct method such as atomic absorption spectroscopy.

Particle Deposition on a Truncated Cylinder in a Supersonic Flow at Low Pressure

Deposition of particles, suspended in supersonic gas flows, onto the impaction plane of a truncated cylinder in low pressure has been studied numerically. The analysis of axisymmetric compressible Navier-Stokes equations was carried out, for a gas phase, by using the lower-upper symmetric Gauss-Seidel (LU-SGS) scheme. In addition, the Lagrangian trajectory model was used for a particle phase. The dilute gas-particle flow was assumed to be coupled in one direction. The effect of freestream pressure on the process of particle deposition was investigated. The local characteristics of deposition were also demonstrated in terms of particle size and freestream pressure. It is found that the particles with low total deposition efficiencies can be deposited rather uniformly on the impaction plane when the effect of thermophoresis is considered.

Deposition efficiency of thin “sprayed” films

The main problem concerning the growth of thin films through solution spraying is the low deposition efficiency. Even though this problem proves to be sound, the authors seldom determine explicitly the efficiency obtained during their deposition. The generally measured parameters are, instead, the thickness of the films and the growth rate. This study develops a method in order to compare, through the values of the above-mentioned parameters, the deposition efficiencies obtained by the various authors.

Corona spray pyrolysis: A new coating technique with an extremely enhanced deposition efficiency

The coating of large areas by means of spray pyrolysis has the great disadvantage of a low deposition efficiency (ratio of atoms deposited to those supplied) of only a few per cent, which causes a very poor economy of this deposition technique. When the aerosol droplets are loaded in a corona discharge and transported in an electric field towards the substrate, the transport to the reaction zone can be easily controlled. With an electrode arrangement which meets electrical and inflow technique requirements, it is possible to achieve a deposition efficiency of more than 80% and to obtain films with good electrical and optical properties. A theoretical description of the transport processes allows the optimization of the coating parameters according to the boundary conditions.

ChemInform Abstract: CHEMICAL VAPOR DEPOSITION OF AMORPHOUS BORON ON MASSIVE SUBSTRATES

AbstractDurch Reduktion von BCl3 mit H2 im Strömungsreaktor werden kompakte Beschichtungen von amorphem Bor auf glatten Oberflächen von Graphit‐, Übergangsmetall(Ti, Ta, Mo, W)‐, Eisen‐ und rostfreien Stahlsubstraten abgeschieden.

Chemical Vapor Deposition of Amorphous Boron on Massive Substrates

Compact coatings of amorphous boron were deposited on the smooth surface of substrates such as graphite, refractory metals, iron, and stainless steel using the reduction of boron trichloride by hydrogen. With a constant surface temperature and a low deposition efficiency, a constant thickness is obtained if transport limitations are avoided at all points of the surface. Extension of the results is proposed for a deposition on larger surfaces and substrates of complex shape. The rate of deposition was studied at temperatures ranging from 950° to 1200°C. The apparent activation energy was found equal to 31.4 kcal/mole. Adherence and absence of cracks are a function of the specific nature of the substrate. The most satisfactory coatings were obtained on graphite, refractory metals of Group Vb, iron, and stainless steel. On iron and stainless steel, a diffusion barrier was first deposited by pack cementation, which avoids the transport of the metals and slows down the boron diffusion. Boron morphology regularity is shown to be a function of nucleation.