He-O2 Mixtures Research Articles

Green-Dyeing Processes of Plant and Animal Fibers Using Folium, an Ancient Natural Dye

In recent decades, fabric-dyeing processes involved greener processes because, since ancient times, dyers used mordants based on metals to make the color better adhere to the textile fibers, but this is the reason for their increased pollution. To develop new strategies, attention was focused on finding the best condition for a dyeing method for natural fibers of vegetable and animal origin (cotton and wool) using an ancient natural dye known as folium. Folium was used mostly in miniature painting in an attempt to avoid the use of classical mordants and solvents. To this purpose, plasma treatment and chitosan coating were employed. Firstly, the textile fibers were analyzed through infrared spectroscopies to verify surface modifications; subsequently, the post-treatment morphological variations were observed via scanning electron microscopy. Both techniques highlighted a significant variation of the surface functional groups due to plasma treatments with He-O2 mixtures, which allowed a greater adhesion of chitosan on the fiber’s surface. Finally, the color strength of samples dyed with folium was tested through fiber optic reflectance spectroscopy, and the folium absorbance peaks were still detected after fabric washing. It is thus shown how an ancient, traditional raw matter has become relevant for developing new modern technologies.

Property value estimation for inhaled therapeutic binary gas mixtures: He, Xe, N2O, and N2 with O2

BackgroundThe property values of therapeutic gas mixtures are important in designing devices, defining delivery parameters, and in understanding the therapeutic effects. In the medical related literature the vast majority of articles related to gas mixtures report property values only for the pure substances or estimates based on concentration weighted averages. However, if the molecular size or structures of the component gases are very different a more accurate estimate should be considered.FindingsIn this paper estimates based on kinetic theory are provided of density, viscosity, mean free path, thermal conductivity, specific heat at constant pressure, and diffusivity over a range of concentrations of He-O2, Xe-O2, N2O-O2 and N2-O2 mixtures at room (or normal) and body temperature, 20 and 37°C, respectively and at atmospheric pressure.ConclusionsProperty value estimations have been provided for therapeutic gas mixtures and compared to experimental values obtained from the literature where possible.

Response of respiration and nitrogenase activity in Datisca glomerata (Presl.) Baill. to changes in pO2

Respiration and nitrogenase activity by root systems of Datisca glomerata (Presl.) Baill. decline rapidly after exposure to C2H2. We measured C2H2 reduction and CO2 evolution to determine whether this decline is due to a variable barrier to O2 diffusion and to examine the nature of O2 regulation in these nodules. Changes in pO2 between 16 and 30 kPa during the decline had only small effects on respiration and nitrogenase activity. Thus the decline is not due to an increase in resistance to O2 diffusion. In contrast, in peas (Pisum sativum L.) nitrogenase activity was strongly reduced when the pO2 was lowered from 20 to 16 kPa during the decline. In Datisca there was little difference in nitrogenase activity when measurements in He-O2 mixtures were compared with Ar-O2 mixtures, showing that there is no gas phase limitation on diffusion. Therefore the major diffusion resistance in Datisca nodules is in the infected cells. We propose that this resistance is in the vesicles of Frankia and that the vesicles represent a series of compartments that vary in the degree to which nitrogenase is protected from O2. As pO2 increases or decreases, various compartments turn on and off keeping the overall rate of nitrogenase activity and respiration nearly constant.Key words: actinorhizal plants, Datisca glomerata, Frankia, nitrogenase, oxygen protection, Pisum sativum.

Variations in flows and pressures during jet ventilation in the infant: A model study

Ventilatory flow rates with either He-O2 (heliox) or N2-O2 (nitrox) mixtures during high frequency jet ventilation (HFJV) were calculated using a mathematical model, and were measured in a physical monoalveolar model of the infant lung. A constant flow was delivered to the model (Vd) drawing with it an entrained flow (Ve). When the inspiratory time (Tl) was long, a back flow (Vr) was generated that increased progressively as the alveolar pressure increased. In order to reduce Vr, the reflux time (Tr), i.e., the time needed for the injected gas to reflux, was measured (Trm) and calculated (Trc) with the model. The Tr depends on both chest-lung compliance and resistance to reflux as well as on the Ve/Vd ratio. For a given setting of the ventilator, values of Trm and Trc were significantly lower with heliox than nitrox (P < 0.01), and the correlation between Trm and Trc were fair with both gases. Tidal volume (VT) was calculated when the Tl was interrupted at Tr. The values of VT were significantly higher with helix than nitrox (P < 0.05). It is concluded that the evaluation of Tr during HFJV may provide useful information for setting the ventilator.

Effects of temperature and composition on the viscosity of respiratory gases

The steady-state sensitivity of resistance pneumotachographs is proportional to viscosity. Dynamic characteristics of pneumotachographs, pressure transducers, and mass spectrometers are also viscosity dependent. We derive linear equations to approximate the viscosities of O2, N2, CO2, H2O, He, N2O, and Ar for temperatures between 20 and 40 degrees C by using published viscosity data and a nonlinear extrapolation equation. We verify the accuracy of the extrapolation equation by comparison with published data. Our linear equations for pure gas viscosities yield standard errors less than 0.35 microP. We also compare a nonlinear equation for calculating the viscosities of mixtures of gases with published measured viscosities of dry air, humid air, and He-O2 and N2-CO2 mixtures. The maximum difference between published and calculated values is 1.3% for 10% CO2 in N2. All other differences are less than 0.38%. For saturated humid air at 35 degrees C, a linear concentration-weighted combination of viscosities differs from our nonlinear equation by 4.9, 2.1, and 1.7% at barometric pressures of 32, 83, and 100 kPa, respectively. By use of our method, the viscosity of normal respiratory gases can be calculated to within 1% of measured values.

A model of constant-flow ventilation in a dog lung.

A semiempirical model of constant-flow ventilation (CFV) is developed to test the hypothesis that a three-zone serial model with the following characteristics can explain the adequate CO2 transport observed during CFV: 1) a zone of jet recirculation immediately downstream of the catheter in which convection dominates; 2) a zone influenced by turbulence but with little or no bulk flow; and 3) a peripheral zone, free of turbulence, in which transport is governed by molecular and augmented diffusion. Interactions between turbulent eddies and cardiogenic oscillations are included using a modification of Taylor dispersion theory according to the formulation of Kamm et al. Predicted values for arterial PCO2 are reasonably similar to experimental results for He-O2, air, and SF6-O2 mixtures for catheter flow rates from 0.2 to 1.6 l/s. Specific impedance to gas exchange was found to be largest immediately proximal to the end of turbulent mixing zone, where transport is governed by low-level eddy mixing and molecular diffusion. Simulations suggest that, during CFV, cardiogenic oscillations augment gas exchange primarily by promoting turbulent eddy dispersion in the distal airways and by extending the length of the turbulent mixing zone. Even small displacements of the catheter are shown to have a dramatic effect on gas exchange.

Effect of lung airway branching pattern and gas composition on particle deposition. II. Experimental studies in human and canine lungs.

The recovery of monodisperse inhaled particles from humans in vivo and from excised human and canine lungs was measured after a single breath for particles suspended in air and in mixtures of He or SF6 with O2. Comparisons were made using the unique particle sizes for which the intrinsic particle motions in air and each mixture were identical, so that differences in recovery could be associated with differences in convective flow. For the in vivo tests, only mixtures with 20% O2 were used, while for the excised lungs, mixtures with 10% O2 were also used. In humans in vivo and in excised human lungs, there was significantly greater deposition from He-O2 mixtures and less deposition from SF6-O2 mixtures, with no differences between the in vivo and the excised lung results for the 80-20 mixtures. For the canine lungs, there were no differences in deposition between air and any He or SF6 mixture. The interspecies differences are consistent with the hypothesis that particle exchange between tidal and residual lung gas is dependent on the distance into each airway that is needed to establish a stable flow profile. The more symmetrical branching of human lung airways causes the entry flow into daughter airways to be highly asymmetric, and flow profile rearrangement is greater than that in the monopodal canine lung.

Contribution of environmental factors in development of hyperbaric bradycardia.

Bradycardia has been observed in animals and humans upon exposure to various hyperbaric environments. However, the relative contribution of ambient pressure, gas density, inert gas species, and inspired O2 tension has not been defined. By means of cutaneous ECG leads, the heart rates of unanesthetized rats were recorded and compared in 11 separate thermo-neutral environments. Ambient pressures applied were 1, 3, and 10 ATA, O2 partial pressure PO2 ranged from 140 to 1,590 Torr, and gas densities were varied from 0.40 to 11.45 g/l, utilizing either N2-O2 or He-O2 mixtures. The exposure heart rates were averaged over a 30-min period and compared with a preceding control value obtained in 1 ATA normoxic He or N2. Significant bradycardia was associated with hyperoxia in environments containing either He or N2, with a magnitude proportional to log PO2. On the other hand, under normoxic conditions bradycardia was not observed despite the similar density, pressure, and inert gas components. It is concluded that hyperoxia is the most important variable of those considered in the development of hyperbaric bradycardia.

Gas mixing during inspiration.

Gas mixing during inspiration.

Development of the differential gas analysis apparatus

A modified gas effluent analysis apparatus is combined with a high-precision gas mixer to be extensively applied to the study of the gas-solid reaction involving not only evolution but absorption of gases and also to the measurement of physico-chemical change of solid. The sample is heated or cooled at the constant rate in a mixed flow of two or more different gases such as He-O2, He-CO2 Ar-H2, etc. The change in the composition of the gas passing through the reactor, due to the decomposition or the gas-solid reaction, are detected at a high sensitivity by a thermal conductivity detector. The sample weight required for the usual measurement is 550 mg. It is applicable to the range from room temperature to 1600°C and the gas flow of any mixing ratio. Although the limits of determination are affected by the operating conditions, an increase or decrease of 0.010.0001 ml of oxygen in the He-O2 mixtures can be detected.

Speech Intelligibility as a Function of Helium-Oxygen Breathing Mixture and Ambient Pressure

Speech intelligibility was obtained on Navy divers at sea level (in air) and at 200 and 450 ft (simulated) in helium-oxygen breathing mixtures. Subjects were personnel in training for Sealab 3 at the Experimental Diving Unit, Washington Navy Yard. A total of 26 subjects were evaluated (11 at 0 and 200 ft, 11 at 0 and 0,50 ft and four at 0, 200, and 450 ft). The speech material used was the PB-25 word lists equated by Campbell for difficulty; the lists were read prior to descending and immediately upon reaching depth. The helium-nitrogen-oxygen mixtures were 79/17/4 at 200 ft and 90/8/2 at 450 ft. A relatively nonreverberent recording environment was provided by an enclosure fabricated from mattresses available in the chamber's sleeping compartment. Listeners were 15 University of Florida students trained for tasks of this nature. The combined efforts of HeO2 mixtures and high ambient pressures were extremely detrimental to speech intelligibility (scores of less than 20% were common at 450 ft). [The project was supported by the Office of Naval Research.]