Perfluorocarbon Vapor Research Articles

Factors Affecting Ultrasonic Release from eLiposomes

Liposomes containing emulsion droplets (eLiposomes) were studied as ultrasound-responsive liposomal drug carriers. This paper presents the effects of temperature, eLiposome size, and ultrasound parameters on the ultrasonically actuated release of calcein, to test hypotheses concerning the physics of acoustic droplet vaporization with regard to vapor pressure and Laplace pressure. Small (200 nm) eLiposomes containing 100-nm emulsion droplets were formed and compared with large (800 nm) eLiposomes containing 100- or 450-nm droplets. Calcein release was quantified by spectroscopic methods. Various experiments examined the influence of perfluorocarbon (PFC) droplet size, vesicle size, temperature, PFC composition and vapor pressure, insonation time, and insonation frequency. Results showed that eLiposome samples released significantly more calcein than their conventional liposome counterparts. Surprisingly, temperature (which directly controls vapor pressure) did not have a strong effect on ultrasound-induced calcein release. In general, calcein release decreased with decreasing droplet size, as hypothesized based on Laplace pressure. Release decreased with increased ultrasound frequency if the pressure amplitude and exposure time were maintained constant, indicating that the gas-phase nucleation rate may have an important role in rupture of eLiposomes. Interestingly, when ultrasound of the same mechanical index was applied at two frequencies, the amount of release correlated strongly with the mechanical index.

Surface tension of water in the presence of perfluorocarbon vapors

Fluorocarbons are highly hydrophobic, biocompatible compounds with a variety of medical applications. Despite significant interest, the study of interfacial properties of fluorocarbons in aqueous systems has received limited attention. In this study, we investigate the influence of perfluoropentane and perfluorohexane vapors on the surface tension of water at room temperature. The results show a substantial decrease in the surface tension of water in the presence of perfluorocarbon vapors. In the investigated range of partial pressures up to the saturation value, a linear correlation between the surface tension and the partial pressure was found. This suggests that an adsorbed perfluorocarbon layer is formed on the surface of water. For comparison, the effect of the perfluorocarbon vapor on the surface tension of methanol was also investigated and a similar dependence was observed. Our results indicate that the stability and dynamic transitions of fluorocarbon colloids, which may be dispersed under physiological conditions as microdroplets, bubbles, or their combination, are likely affected by the composition of liquid and gas phases.

Photoacoustic Detection of Perfluorocarbon Tracers in Air for Application to Leak Detection in Oil-Filled Cables

The underground oil-filled cable consists of a hollow copper conductor surrounded by oiled paper which acts as electrical insulation. The oil flows along the conductor and diffuses through it to the insulating paper. A lead sheath is used as the outer retaining wall. As the deterioration of this cover may cause a loss of insulation fluid, its detection is very important since this high voltage and power cable is used in cities even under sidewalks. The method of perfluorocarbon vapor tracers, based on the injection and subsequent detection of these volatile chemical substances in the vicinity of the cable, is one of the most promising methods, so far used in combination with gas chromatography and mass spectrometry. In this study, the possibility of detecting two different tracers, \(\mathrm{C}_{6}\mathrm{F}_{12}\) and \(\mathrm{C}_{7}\mathrm{F}_{14}\), by means of resonant photoacoustic spectroscopy is studied. The beam from a tunable amplitude-modulated \(\mathrm{CO}_{2}\) laser goes through an aluminum cell with quarter wave filters at both ends of an open resonator and an electret microphone in its center, attached to the walls. The calibration of the system for either substance diluted in chromatographic air showed a higher sensitivity for \(\mathrm{C}_{7}\mathrm{F}_{14}\), so the experiment was completed checking the behavior of this substance in samples prepared with ambient air in order to analyze the application of the system to field studies.

Recovery of perfluoroethane from chemical vapor deposition operations in the semiconductor industry

Abstract Perfluorocarbons, particularly perfluoroethane (C 2 F 6 ), are widely used in the semiconductor industry for plasma cleaning of chemical vapor deposition (CVD) chambers. Although the quantity of C 2 F 6 released into the atmosphere by these operations is relatively small, C 2 F 6 is a very powerful greenhouse gas, and methods of reducing atmospheric emissions are being sought. One method is to use a selective membrane to concentrate the C 2 F 6 so that the gas can be condensed on cooling and recovered as a liquid. In the past, similar membrane vapor separation processes used rubbery polymer membranes that permeate the vapor. However, perfluorocarbon vapors have unusually low permeabilities even in rubbery polymers, because of their large size and low solubility. Therefore, glassy polymeric composite membranes were developed to separate and recover C 2 F 6 from CVD chamber exhaust gas. These membranes permeate oxygen and nitrogen, and retain the perfluorocarbon vapor. Membranes with nitrogen/C 2 F 6 selectivities of up to several hundred were made from a number of polymers. A process using these membranes to recover 99% C 2 F 6 from CVD exhaust gas was designed.

Changes in pulmonary function and oxygenation during application of perfluorocarbon vapor in healthy and oleic acid-injured animals.

To investigate the changes in pulmonary function and gas exchange during application of 18% perfluorohexane vapor in healthy and in oleic acid-injured animals and compare it with an injured control group. Prospective randomized controlled study. Experimental research laboratory at a university medical center. Nineteen sheep weighing 31.4 +/- 4.1 kg. Lung injury was induced in 14 sheep by the intravenous injection of 0.1 mL/kg oleic acid. After establishment of lung injury (PaO(2)/F(IO(2)) ratio, <200; pulmonary artery occlusion pressure, <19 torr), seven animals were treated with 18% perfluorohexane vapor for 30 mins whereas seven animals served as controls. After the start of perfluorohexane treatment, blood gases and respiratory and hemodynamic data were collected in 10-min intervals throughout the study period of 1 hr. In addition, five healthy animals received perfluorohexane vapor for 30 mins and were followed up for 2 hrs to exclude delayed negative effects. Treatment of healthy animals with 18% perfluorohexane vapor was not accompanied by any significant adverse effects. It was associated with a significant decrease of alveolar-arterial oxygen difference during perfluorohexane application (p <.05). In injured animals, 18% perfluorohexane led to a sustained improvement of peak inspiratory pressures within 10 mins of treatment (p <.001). The concomitant increase in compliance was equally significant (p <.001). Significant improvements in PaO(2) occurred despite a decrease in F(IO(2)) to 0.81 at the end of vaporization. Healthy animals tolerated perfluorohexane vapor well without significant changes in oxygenation and mechanical lung function for 2 hrs. In injured animals, application of perfluorohexane vapor primarily improved peak inspiratory pressure and compliance. The increase of oxygenation therefore could be secondary to an improvement in compliance.

Effect of perfluorocarbon (perfluorooctyl bromide) vapor on tidal volume measurement during partial liquid ventilation.

To compare measured tidal volumes with and without perfluorocarbon (perfluorooctyl bromide) vapor, by using tidal volumes in the range suitable for neonates ventilated with partial liquid ventilation. We also aimed to determine the correction factor needed to calculate tidal volumes measured in the presence of perfluorooctyl bromide vapor. Prospective, experimental study. Neonatal research laboratory. Reproducible tidal volumes from 5 to 30 mL were produced with a rodent ventilator and drawn from humidifier chambers immersed in a water bath at 37 degrees C. Control tidal volumes were drawn from a chamber containing oxygen and water vapor, and the perfluorocarbon tidal volumes were drawn from a chamber containing oxygen, water vapor, and perfluorooctyl bromide vapor. Tidal volumes were measured by a VenTrak respiratory mechanics monitor with a neonatal flow sensor and a Dräger pneumotachometer attached to a Dräger neonatal ventilator. All tidal volumes measured with perfluorooctyl bromide vapor were increased compared with control. The VenTrak-measured tidal volumes increased by 1.8% to 3.5% (an overall increase of 2.2%). The increase was greater with the Dräger hot-wire anemometer: from 2.4% to 6.1% (an overall increase of 5.9%). Regression equations for mean control tidal volumes (response, Y) vs. mean perfluorooctyl bromide tidal volumes (predictor, X) are as follows: for the VenTrak, Y = -0.026 + (0.978 x X), r =.9999, p <.0001; and for the Dräger, Y = 0.251 + (0.944 x X), r =.9996, p <.0001. The presence of perfluorooctyl bromide vapor in the gas flowing through pneumotachometers gives falsely high tidal volume measurements. An estimate of the true tidal volume allowing for the presence of perfluorooctyl bromide vapor can be made from regression equations. Any calculation of lung mechanics must take into account the effect of perfluorooctyl bromide vapor on the measurement of tidal volume.

Effects of vaporized perfluorocarbon on pulmonary blood flow and ventilation/perfusion distribution in a model of acute respiratory distress syndrome.

Perfluorocarbon (PFC) liquids are known to improve gas exchange and pulmonary function in various models of acute respiratory failure. Vaporization has been recently reported as a new method of delivering PFC to the lung. Our aim was to study the effect of PFC vapor on the ventilation/perfusion (VA/Q) matching and relative pulmonary blood flow (Qrel) distribution. In nine sheep, lung injury was induced using oleic acid. Four sheep were treated with vaporized perfluorohexane (PFX) for 30 min, whereas the remaining sheep served as control animals. Vaporization was achieved using a modified isoflurane vaporizer. The animals were studied for 90 min after vaporization. VA/Q distributions were estimated using the multiple inert gas elimination technique. Change in Qrel distribution was assessed using fluorescent-labeled microspheres. Treatment with PFX vapor improved oxygenation significantly and led to significantly lower shunt values (P < 0.05, repeated-measures analysis of covariance). Analysis of the multiple inert gas elimination technique data showed that animals treated with PFX vapor demonstrated a higher VA/Q heterogeneity than the control animals (P < 0.05, repeated-measures analysis of covariance). Microsphere data showed a redistribution of Qrel attributable to oleic acid injury. Qrel shifted from areas that were initially high-flow to areas that were initially low-flow, with no difference in redistribution between the groups. After established injury, Qrel was redistributed to the nondependent lung areas in control animals, whereas Qrel distribution did not change in treatment animals. In oleic acid lung injury, treatment with PFX vapor improves gas exchange by increasing VA/Q heterogeneity in the whole lung without a significant change in gravitational gradient.

Breakdown strength of perfluorocarbon liquid/vapor and mixtures of the liquid with SF6

In the insulation design for power apparatus which use perfluorocarbon (PFC) liquid, it is necessary to study the breakdown strength of the liquid/vapor under a uniform field. Particularly for devices with SF6, the breakdown strength is an important factor in insulation engineering. This paper presents an investigation on the insulation characteristics of PFC liquid/vapor with and without SF6, when the temperature is varied from 20 °C to 80 °C. Experiments are performed using plane–plane electrode geometry in a closed system under ac and lightning impulse voltages. Results are as follows: (1) in the case of PFC vapor pressure above the liquid without SF6, the breakdown strength in the liquid phase is little affected by the temperature rise, whereas it increases greatly in the vapor phase under the same condition; (2) in the other case of a mixture pressure above the liquid with SF6 under ac voltage, the breakdown strength of the mixture vapor phase is given by adding the contribution of the two components (PFC vapor and SF6). © 2000 Scripta Technica, Electr Eng Jpn 134(1): 1–9, 2001

Hydrocarbon and Perfluorocarbon Gas Sorption in Poly(dimethylsiloxane), Poly(1-trimethylsilyl-1-propyne), and Copolymers of Tetrafluoroethylene and 2,2-Bis(trifluoromethyl)-4,5- difluoro-1,3-dioxole

Sorption of a series of gases, perfluorocarbon vapors (CF4, C2F6, and C3F8) and their hydrocarbon analogues in poly(dimethylsiloxane) [PDMS], poly(1-trimethylsilyl-1-propyne) [PTMSP], and two random copolymers of tetrafluoroethylene [TFE] and 2,2-bis(trifluoromethyl)-4,5-difluoro-1,3-dioxole [BDD] are reported as a function of penetrant pressure at 35 °C. Sorption isotherms for all penetrants in rubbery PDMS are linear or slightly convex to the pressure axis, while those in the glassy polymers are concave and are well described by the dual mode model. Fluorocarbon sorption levels are lower than sorption levels of their hydrocarbon analogues in the hydrocarbon-based PDMS and PTMSP matrixes, while the reverse is true in the fluorinated TFE/BDD copolymers. Exceptionally low fluorocarbon solubilities in PDMS are ascribed to poor penetrant/polymer energetic interactions.

Proposed mechanism of pulmonary gas trapping (PGT) following intravenous perfluorocarbon emulsion administration.

To investigate various hypotheses and identify the most likely mechanism preventing the complete collapse of test animal lungs at sacrifice subsequent to intravenous injection of certain perfluorocarbon emulsions. Literature data were reviewed, experimental data were extracted from completed studies and new data were generated in an attempt to delineate reasons why, in certain animals, lungs fail to collapse normally at necropsy if previously injected with certain perfluorocarbon emulsions. The proposed hypothesis involved gas osmosis through endogenous pulmonary surfactant-liquid bridges (micro-bubbles). The observed effect of incomplete lung collapse upon necropsy was found to correlate with perfluorocarbon vapor pressure. Results indicated that failure to collapse could be attributed to the formation of intra-alveolar micro-bubbles induced by the normal pulmonary elimination of perfluorocarbon vapor. These micro-bubbles result in a phenomenon which could be characterized by the term, pulmonary gas trapping. Reduction of the perfluorocarbon concentration gradient across the bubble films by exposure to a perfluorocarbon vapor-containing atmosphere was found to reduce the effect in-vivo and prevent gas osmosis bubble growth in-vitro. Experimental observations are consistent with the proposed theory of perfluorocarbon-related gas osmosis through micro-bubbles that prevent complete lung collapse as observed upon opening the thoracic cavity of test animals.

Biochemical aspects of perfluorocarbon interaction with hepatic and renal tissues

We tested the metabolic consequences of i.v. administration of an emulsion of a perfluorocarbon (PFC) mixture (82.1% perfluorobutylfurane, 7.5% perfluoropropylpyrane, 7.4% isomers) RM 101, kindly supplied by Enichem Synthesis. The emulsions were prepared using either RM 507, a fluorinated compound produced by Enichem, or soybean phospholipids as tensioactive agents. Mitochondria isolated from liver and kidneys of rats injected with the RM 507-emulsion and killed after 3,7 or 30 days showed limited alterations of mitochondrial energy-converting processes, which however were fully compatible with animal life. In liver mitochondria the steady-state transmembrane potential appeared slightly decreased regardless of the interval from the injection. ADP-stimulated respiration decreased by about 20% in the 7 and 30 day experiments and the rate of ATP synthesis was also inhibited. In kidney mitochondria the steady-state transmembrane potential appeared unaffected while both ADP-stimulated respiration and ATP synthesis were significantly decreased. Histological examination of specimens obtained from excised organs showed very limited structural alterations. Six months after PFC i.v. administration both liver and kidney specimens showed neither significant histological alterations nor the presence of intracytoplasmic perfluorocompound particles. Although the magnitude of the transmembrane potential was unaltered, both in liver and kidney mitochondria a substantial depression of the rate of ATP synthesis was observed, which appeared unrelated to the visible presence of PFC micelles within the cells. Mitochondria isolated from liver and kidneys of rats injected with the phospholipid emulsion did not show severe mitochondrial alterations. It should be noted that two kinds of emulsion-cell components interactions are conceivable. In fact the micelles taken up exert a mechanical effect (particularly evident in perfused organs) on subcellular organisation, although the release of effective amounts of tensioactive compound from particles cannot be excluded. In addition, PFC vapors slowly leave the micelles and might interact with hydrophobic sites of functional structures. This phenomenon, which allows PFC elimination from cells, might account for the persistance of some metabolic alterations even when emulsion micelles are no longer evident in histologic specimens.

Breakdown Strengths of a Perfluorocarbon Vapor (FC-75) and Mixtures of the Vapor with SF6

Breakdown Strengths of a Perfluorocarbon Vapor (FC-75) and Mixtures of the Vapor with SF6

Electric breakdown of perfluorocarbon vapors and their mixtures with nitrogen

This investigation was concerned with a study of the breakdown behavior of the higher molecular weight perfluorocarbon vapors and mixtures of these with nitrogen. Impulse and 60-cycle data were obtained under both uniform and nonuniform field conditions. The results are compared with those for sulfur hexafluoride, nitrogen, and oil. It was found that these perfluorocarbon vapors have surprisingly high dielectric strength not only in the pure form but also when mixed with nitrogen. Values of dielectric strength higher than for sulfur hexafluoride are easily obtainable at the same pressure. Values equal to those for oil can be obtained at relatively low pressures under certain conditions. The results are briefly discussed in terms of modern gas breakdown theory. The unusually high dielectric breakdown combined with complete non-flammability, inertness, and excellent thermal stability of the perfluorocarbons suggest that they should find applications in the insulation field.