Carbon Dioxide Effects on Fruit Respiration. I. Measurement of Oxygen Uptake in Continuous Gas Flow

Characteristics of the large-scale circulation during episodes with high and low concentrations of carbon dioxide and air pollutants at an arctic monitoring site in winter

ASSIMILATION AND RESPIRATION OF EXCISED LEAVES AT HIGH CONCENTRATIONS OF CARBON DIOXIDE

The physiologic action of oxygen and carbon dioxide on the coronary circulation, as shown by blood gas and electrocardiographic studies

Color phenomena in thorium oxide

Permeation properties were analyzed for a mixture of CO2, O2, and N2 in a medium-size polysulfone hollow fiber permeator with a net permeation area of 4.22 m2. Measurements were conducted as a function of feed composition, reject flow rate, and feed pressure. Results included variations in species permeability, separation factor, permeate enrichment, reject depletion, and stage cut as a function of system parameters. Variations in permeation properties show strong dependence on feed composition, reject flow rate, and feed pressure. Permeability of carbon dioxide was higher at larger feed pressures and higher carbon dioxide content in the feed stream. Effect of increasing the reject flow rates on the permeability of carbon dioxide was affected by the system pressure and the carbon dioxide content in the feed stream. At low pressures, increase of the reject flow rate resulted in a decrease of carbon dioxide permeability. The opposite behavior was obtained at higher feed pressures. Increase of the reject flow rate reduced the gas residence time within the permeator. Increase of reject flow rate reduced species residence within the permeator and in turn increased resistance to species transport within the permeator. However, higher system pressures and carbon dioxide content in the feed stream resulted in larger levels of membrane plasticization, which increased the permeation rates of all species. The combined efféct of reducing the species residence time within the permeator and the level of membrane plasticization favored the permeation of carbon dioxide versus the other two species. Variations in other permeation properties, which include oxygen and nitrogen permeabilities, stage cut, permeate enrichment in carbon dioxide, and reject depletion in carbon dioxide, were also explained in terms of resistances encountered within the permeator and the membrane.

Although the concentration of carbon dioxide or of oxygen in the storage atmosphere have a considerable effect upon the sprouting of potatoes, it has been shown that changes in the carbon dioxide and oxygen tension in the internal atmosphere of the tuber, prior to the natural break of dormancy, are negligible (Burton, I950, I95i). Further, where sprout inhibition has resulted from storage in high concentrations of carbon dioxide these high concentrations have usually been achieved by means which allowed also the accumulation in the storage atmosphere of volatile respiratory products other than carbon dioxide. Thus Kidd (I9I9) inhibited the sprouting of non-dormant potatoes by storing them in three artificial gas mixtures containing zo % of carbon dioxide, and 5, io and 20 % of oxygen respectively. He did not pass these mixtures continuously through the desiccators in which the tubers were contained, but adjusted their composition every two days (see Kidd, I914). The accumulation, to some extent, of volatiles other than carbon dioxide was thus possible. In experiments in which a concentration of io% carbon dioxide was used, the reduction of sprouting which normally resulted was due more to a reduction in the number than in the size of sprouts, and there were instances in which the sprouting in I0 % carbon dioxide and in the absence of carbon dioxide did not markedly differ. Braun (I93I) used three methods of adjusting the composition of the atmospheres in which he stored potato tubers. The first, which he dismissed as unsatisfactory, was to allow the respiratory carbon dioxide to accumulate for from i to 3 days, the highest concentration reached being zo2z 0. The atmosphere was then replaced by air-it is in this complete replacement that the method differs from that of Kidd-and the process repeated. In the second method, which was that adopted by Braun for most of his work, carbon dioxide was allowed to accumulate as above, and it was then attempted to keep it at the desired level by continuous ventilation. The technique was not altogether satisfactory. Thus a concentration of carbon dioxide described as 9g I3 % was in reality the mean, weighted for time, of concentrations ranging from 3.5 to I2z6 %. The third, and most satisfactory, method was continuously to ventilate, with artificial gas mixtures, the desiccators in which the tubers were contained. It will be seen that, in the first of the methods described above, volatiles other than carbon dioxide would accumulate for a few days and would then be removed; in the

Welfare implications of gas stunning pigs: 3. the time toloss of somatosensory evoked potential and spontaneous electrocorticogram of pigs during exposure to gases

Electrical waterbath stunning is the most common method used to stun poultry under commercial conditions. The voltage supplied to a multiple bird waterbath stunner must be adequate to deliver the required minimum current to each bird. High frequency (> 300 Hz) electrical waterbath stunning needs further investigation to determine its efficiency. It should always be followed by a prompt neck cutting procedure where all the major blood vessels in the neck are severed. Irrespective of the waveform or frequency of the currents employed, constant current stunners should be installed under commercial conditions to ensure that the minimum currents are delivered to individual birds in waterbath stunners. Head only electrical stunning of poultry is being investigated in detail and there is scope for commercial development. Important features include (a) a constant current capable of delivering a preset current, (b) a bird restraining conveyor and head presentation devices enabling the stunning tongs to be accurately placed, (c) more effective electrical stunning tongs in terms of delivering necessary currents while using low voltages, and (d) induction of cardiac arrest immediately after stunning to eliminate wing flapping. Stunning/killing of poultry still in their transport containers using gas mixtures would appear to be the best future option as far as bird welfare is concerned. However, birds can also be stunned/killed on a conveyor using gas mixtures, thereby eliminating the stress associated with the shackling of live birds before electrical stunning. Under the conveyor system birds should be presented to the gas mixtures in a single layer. Within gas mixtures a minimum of 90% argon in air would appear to be the first choice. A mixture of 30% carbon dioxide and 60% argon in air is better than using a high concentration of carbon dioxide in air, and is therefore considered to be the second choice. A two stage system that involves firstly stunning broilers with a low concentration of carbon dioxide and then killing them with a high concentration of carbon dioxide can be used by those who wish to use this gas for economic reasons. The two stages should be distinctly separated so that the birds are stunned well before exposure to a high concentration of carbon dioxide in air. In comparison with carbon dioxide alone, a mixture of 30% oxygen and 40% carbon dioxide in air prolongs the induction of anaesthesia and the exposure time required to kill the birds. The addition of oxygen to carbon dioxide may therefore not have any benefit to bird welfare or the processors. Mechanical stunning of poultry using penetrating captive bolts or non-penetrating mushroom headed bolts has been developed. However, stunning with these devices results in very severe wing flapping and further research is necessary to find ways of alleviating this problem.

New study on the correlation between carbon dioxide concentration in the environment and radon monitor devices

1. The whole peel of Valencia oranges and the albedo of navel oranges were separated into alcohol-soluble and alcohol-insoluble fractions by extraction of the fresh material with hot 80% ethyl alcohol. The principal constituents of the two fractions were determined, and some of their chemical properties studied. 2. The alcohol-soluble fraction of the whole peel of Valencia orange and of the albedo of navel orange averaged 57.31% and 55.19%, respectively, of the total dry weights. Soluble sugars accounted for 55.4% of the total extractable material in Valencia peel and for 72.69% in navel albedo. This fraction also contained substances which produced a small amount of carbon dioxide on hydrolysis with 19% hydrochloric acid. This carbon dioxide was probably produced by low polymer galacturonides soluble in hot 80% alcohol. 3. The alcohol-insoluble fraction of Valencia orange whole peel and of navel albedo averaged 42.69% and 44.81%, respectively, of the total dry weights. The sum of the water-soluble and acid-soluble pectic substances (as calcium pectate) of the alcohol-insoluble fraction averaged 39.76% in Valencia peel and 34.87% in navel albedo; the insoluble residues averaged 30.53% and 30.41%, respectively. The undetermined portion consisted of hemicelluloses which contained small amounts of polyuronides and which were rendered soluble by the extraction treatment. 4. The purity of the extracted pectic material (as calcium pectate) was ascertained on each sample by determining contents of carbon dioxide, calcium, and furfural. 5. As the polyuronides yield carbon dioxide quantitatively on hydrolysis with hydrochloric acid, the carbon dioxide values determined are a fair measure of the total pectic substances in the alcohol-insoluble solids. When the carbon dioxide values were accompanied by corresponding values for methoxyl, the degree of methylation of the pectic substances was subsequently calculated by dividing the determined methoxyl by that equivalent to the total carbon dioxide. Methylation in Valencia peel averaged 83.38%, and in navel albedo, 82.39%. 6. The sum of the carbon dioxide in the aqueous extract, acid extract, and residue amounted to 95.20% and 97.47% (mean values) of the total carbon dioxide of the alcohol-insoluble solids in the Valencia orange peel and navel orange albedo, respectively. The total calcium pectate precipitated from the aqueous and acid extracts of Valencia peel yielded 94.12% of the carbon dioxide dissolved by the extractants. The corresponding value for navel albedo was 88.00%. 7. Since the alcohol-insoluble fraction contained the pectic substances, most of the carbon dioxide which could be liberated by hydrolysis with 19% hydrochloric acid, and all the methoxyl groups, occurred in this fraction. The ratio of methoxyl to carbon dioxide was approximately the same in Valencia orange peel and in navel orange albedo. 8. The carbon dioxide equivalent to the sum of the esterified and nonesterified carboxyl groups was equal to the total carbon dioxide of the alcohol-in-soluble fraction obtained on hydrolysis with 19% hydrochloric acid.

The effect of high partial pressures of oxygen on photosynthesis in Chlorella—I. : The effect on end products of photosynthesis

The extension of commercial life and the reduction of postharvest losses of perishable fruits is mainly based on storage at low temperatures alone or in combination with modified atmospheres (MAs) and controlled atmospheres (CAs), directed primarily at reducing their overall metabolism thus delaying ripening and senescence. Fruits react to postharvest conditions with desirable changes if appropriate protocols are applied, but otherwise can develop negative and unacceptable traits due to the onset of physiological disorders. Extended cold storage periods and/or inappropriate temperatures can result in development of chilling injuries (CIs). The etiology, incidence, and severity of such symptoms vary even within cultivars of the same species, indicating the genotype significance. Carbohydrates and amino acids have protective/regulating roles in CI development. MA/CA storage protocols involve storage under hypoxic conditions and high carbon dioxide concentrations that can maximize quality over extended storage periods but are also affected by the cultivar, exposure time, and storage temperatures. Pyruvate metabolism is highly reactive to changes in oxygen concentration and is greatly affected by the shift from aerobic to anaerobic metabolism. Ethylene-induced changes in fruits can also have deleterious effects under cold storage and MA/CA conditions, affecting susceptibility to chilling and carbon dioxide injuries. The availability of the inhibitor of ethylene perception 1-methylcyclopropene (1-MCP) has not only resulted in development of a new technology but has also been used to increase understanding of the role of ethylene in ripening of both non-climacteric and climacteric fruits. Temperature, MA/CA, and 1-MCP alter fruit physiology and biochemistry, resulting in compositional changes in carbon- and nitrogen-related metabolisms and compounds. Successful application of these storage technologies to fruits must consider their effects on the metabolism of carbohydrates, organic acids, amino acids and lipids.

Survival and behaviour studies were made on ammocoetes subjected to water of various tensions of oxygen and carbon dioxide. Ammocoetes can tolerate, for at least 4 days, oxygen tensions as low as 7–10 mmHg at 5°C, 12-16 mmHg at 15·5°C and between 13–16 and 19–21 mmHg at 22·5°C. A limited ability to acclimate to low oxygen tensions was found in some animals. A characteristic emergence behaviour is evoked by low partial pressures of oxygen that approach the lethal level and by high concentrations of carbon dioxide. Ammocoetes respond to low oxygen and high carbon dioxide by an increase in the rate and amplitude of beating of the branchial basket. This increase is maintained in animals able to survive at low oxygen tensions. A high affinity of the blood for oxygen is evident from oxygen equilibrium curves determined on erythrocytes suspension. There was an insignificant Bohr effect at 15·5°C in the pH range 7·68–6·70, although a change occurred in the n value. Haemoglobin concentration, haematocrit and oxygen equilibria suggest that the characteristics of the blood contribute significantly to the ability of ammocoetes to survive in low oxygen conditions.

Keeping inventory of carbon dioxide in liquid dominated geothermal reservoirs

Alfalfa (Medicago sativa L.) and orchard grass (Dactylis glomerata L.) plots were exposed to ambient or ambient plus 350 cm3 m-3 carbon dioxide concentrations at Beltsville, Maryland, U.S.A. Replicate plots were established in different years and fertilized annually. We report here data for the second and third years after establishment. There has been no increase in the yearly production of either species at the elevated carbon dioxide concentration after the first sea- son. In orchard grass, reduced growth at the high carbon dioxide concentration in the spring offset growth stimulation in the summer. Weed growth was consistently increased by carbon dioxide enrichment, but weed species composition was unaffected. Leaf photosynthetic capacity was reduced by the high carbon dioxide concentration in both crop species, as was leaf nitrogen content. Canopy carbon dioxide uptake was slightly higher in the elevated carbon dioxide treatments, consistent with the increased weed growth. In alfalfa, elevated carbon dioxide significantly reduced canopy carbon dioxide