Transport Properties Of CO2 Research Articles

Gas transport properties of linear and crosslinked side‐chain liquid crystalline polymers with variable spacer lengths

AbstractA series of side‐chain liquid crystalline polymers (side‐chain LCPs) with different flexible spacer lengths and various degrees of crosslinking were synthesized and characterized. The transport properties of O2, N2, CO2 and CH4 in these polymers were measured by using permeation and sorption methods. The values of diffusion and solubility coefficients were found to be significantly affected by the crosslinking reaction. In contrast to conventional crosslinked polymers, the values greatly increase as the degree of crosslinking increases. The reason might be the use of the flexible oligodimethylsiloxane crosslinking agent and the low solubility of gases in the liquid crystalline regions. The transport properties were also demonstrated to depend strongly on the flexible spacer length. This was ascribed to the fact that different liquid crystalline phases are formea. For the smectic phase, the diffusion and solubility coefficients are lower than those found in the nematic one.

Sorption and permeation properties of poly(p‐phenylene sulfide) crystallized in the presence of sorbed gas molecules

AbstractThe sorption behaviour of CO2 and N2 in poly(p‐phenylene sulfide), PPS, crystallized in the presence of CO2 and N2O molecules was studied at 298 K in the pressure range of 1–30 bar. The CO2 transport properties of these samples were investigated at the same temperature in the pressure range of 1–20 bar. The temperature dependence of the CO2 transport parameters was examined between 293 and 343 K at a pressure of 5 bar, for the virgin material, thermal and CO2 crystallized specimen only. All measured properties are compared with those of PPS crystallized by annealing at vacuum conditions to a similar degree of crystallinity, and with the virgin, nearly amorphous material. For the samples crystallized in the presence of sorbed gases an increased CO2‐solubility was observed. A part of unrelaxed free volume is proposed to remain in the samples after crystallization in presence of sorbed gas molecules. These voids formed under sorbed gas conditions seem to be stable even after removal of the sorbed molecules. The measured diffusion coefficients for CO2 were lower in the samples crystallized in the presence of gas molecules, compared to the virgin sample. This is expected to be due to an increased diffusive resistance by passing the interfaces of the formed voids. Permeability, which is governed by both, diffusion and sorption, undergoes non‐uniform changes. An attempt is made to explain this behaviour based on the dual‐mode‐sorption and dual‐mobility model.

In vitro evidence for sodium-dependent pH regulation in sea lamprey (Petromyzon marinus) red blood cells

Factors influencing the pH of sea lamprey (Petromyzon marinus) erythrocytes were examined in vitro. The absence of extracellular Na+ caused a significant reduction in the erythrocyte pH. In addition, the protonophore 2,4-dinitrophenol was capable of reducing the erythrocyte pH when it was dissolved in dimethyl sulfoxide. In the presence of ouabain, a step increase in the carbon dioxide tension caused a large increase in the intracellular Na+ concentration, but the rate of increase was considerably reduced after the 1st hour. Even in the absence of ouabain, however, the intracellular Na+ concentration in erythrocytes equilibrated with 3% CO2 is much greater than that in erythrocytes equilibrated with 0.2% CO2. Together, these results suggest that Na+-dependent H+ movements, possibly Na+–H+ exchange, may have an important role in erythrocyte pH regulation in P. marinus. Moreover, the mechanism appears to be stimulated by the decrease in extracellular or erythrocyte pH associated with the increase in [Formula: see text]. Extracellular Na+ also has a significant impact on the CO2-transport properties of P. marinus blood. In the absence of extracellular Na+, the intracellular total CO2 concentration was significantly reduced, whereas extracellular total CO2 concentration, [Formula: see text], was significantly increased. Furthermore, in the no-Na+ saline, [Formula: see text] became dependent on the hematocrit; an increase in the number of erythrocytes resulted in an increase in [Formula: see text]. This result suggests that the erythrocyte membrane of P. marinus may be permeable to [Formula: see text].

Effects of oxygen saturation on the CO2 transport properties of Lampetra red cells.

We investigated the effects of haemoglobin oxygenation on the carbon dioxide transport properties of lamprey (Lampetra fluviatilis) erythrocytes. The non-bicarbonate buffering capacity of deoxygenated lamprey erythrocytes was -43 mmol.L-1.pH unit-1. The carbon dioxide content of oxygenated erythrocytes was 7-8 mM lower than that of deoxygenated erythrocytes over a range of carbon dioxide tensions. This was the result of a pronounced Haldane effect (proton uptake by haemoglobin upon deoxygenation): at extracellular pH 7.5, the intracellular pH of oxygenated erythrocytes was 7.67, and increased to 7.91 when the haemoglobin-oxygen saturation decreased to 7%. No specific oxylabile binding of bicarbonate or carbon dioxide to haemoglobin occurred under the conditions of the present study. Owing to the high red cell pH and its large increase upon deoxygenation, carbon dioxide can be effectively transported in lamprey blood, although plasma bicarbonate is not available for carbon dioxide excretion because of the lack of rapid anion exchange across the red cell membrane.

Respiratory properties of blood of the gray seal,Halichoerus grypus

1. This study examined the O2 and CO2 transport and acid-base properties of blood of the gray seal. Phocid seals use theblood as an oxygen store for aerobic metabolism during diving. Particular objectives were to determine whether CO2 exerts a specific effect on blood oxygen affinity, and whether the Bohr coefficient varies between different levels of oxygen saturation. 2. Hematocrit (0.50), blood hemoglobin concentration (12.8 mM heme) and cell hemoglobin concentration (25.4 mM) were, high compared to terrestrial mammals but similar to other seals (Table 2). Isoelectric focusing resolved the same four hemoglobin components in six individuals, with the most important components constituting 60% and 20% of the total. Oxygen affinity (P50=27.1 Torr at pH 7.4, 37.5°C) and equilibrium curve shape (nH=2.59) were similar to other phocid seals and terrestrial mammals (Tables 1,4). The Bohr coefficient for CO2 induced pH change (−0.51) was only slightly higher than that for fixed acid incuded pH change (−0.47), implying little oxygen-linked carbamino formation (Table 1). The bohr coefficients were at the upper end of the range found in terrestrial mammals, and did not vary with oxygen saturation (Table 1). 3. Blood buffer value was high (31.5 mM/pH), in accord with the high hemoglobin concentration (Table 3). The Haldane effect (−0.32 mol CO2 per mol O2, Fig. 2) was similar to those in blood of other seals and dog, but higher than that in human blood. Hydrogen ion uptake by hemoglobin upon deoxygenation (0.40 mol/mol O2) was greater than in human blood, in proportion to the larger fixed acid Bohr coefficient in the seal. 4. Blood of the gray seal, like that of other phocid seals, is distinguished from that of terrestrial mammals primarily by high hemoglobin concentration and oxygen capacity, which increase blood oxygen stores available for use during diving. Other properties are similar to those of terrestrial mammals or differ only as a consequence of the high hemoglobin concentration.

ALVEOLAR CARBON DIOXIDE EQUILIBRIA IN BREATH-HOLDING EXPERIMENTS.

An investigation was made of the equilibria approached by alveolar CO2 tension in normal human subjects during breath holding. A major objective of this work was to test the hypothesis that the approached equilibrium was with deoxygenated venous rather than with oxygenated venous blood. The study included determination of CO2 tension of expired air by continuous recording before and after breath holding for various time periods, with simultaneous airflow recordings. Pulmonary blood flows were calculated from these data, and were compared with those obtained by an independent rebreathing technique. The findings indicate that the equilibrium approached in the alveolar spaces during breath holding is between the alveolar air and the blood as it enters the pulmonary capillary. This would indicate that CO2 dumping by passive transfer must precede the uptake of oxygen. Effective pulmonary flows calculated from these data were reproducible and in agreement with those obtained by the rebreathing technique. human pulmonary blood flows; alveolar CO2 transport properties; CO2 rebreathing in humans Submitted on July 22, 1963