An in vitro study of the relative importance of bile and carbon dioxide in the activation of Fasciola gigantica metacercariae

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

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.

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

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

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.

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

1. Crayfishes sense the increase in carbon dioxide and acetic and hydrochloric acids in a gradient.2. Both propinquus and virilis are intoxicated by carbon dioxide; virilis is also intoxicated by acetic acid but to a lesser degree.3. The four species are susceptible to high concentrations of carbon dioxide and when subjected to high concentrations die in the following order, virilis, propinquus, diogenes and immunis.4. Propinquus reacts negatively to the higher concentrations of carbon dioxide in a gradient, but when the total amount of acid present is large, the negative reaction may be interfered with by the direct detrimental effect of the acid.5. Virilis reacts less definitely to the higher concentrations of carbon dioxide in a gradient than does propinquus. This is true whether the total concentration of the acid is large or small.6. Both diogenes and immunis react more or less irregular to carbon dioxide due possibly to the lesser sensitiveness of these two species to this acid.7. Both propinquus and virilis react negatively to the higher concentrations of acetic acid in gradients of this acid; propinquus reacts definitely in the presence of both high and low total concentrations; virilis reacts definitely to low total concentrations, but not so definitely to high total concentrations; diogenes reacts irregular and less intense than the first two species while immunis reacts more definitely but with low intensity.8. All four species react more strongly to hydrochloric acid than acetic acid and more strongly to acetic acid than carbon dioxide.9. The intensity of avoiding reactions of all species to all acids tested as is shown by turnings only are in the following order; propinquus, virilis, immunis and diogenes.10. The intensity of avoiding reactions of all four species varies directly as the total concentrations of the acids, and probably directly as the hydrogen ion concentration.11. Rapid modification of behavior is shown by all four species. This modification may be due to the increased sensitiveness on the part of the animals, the increased sensitiveness being the result of higher ion concentration in the animal's blood.12. The specific reactions of the crayfishes in gradients of carbon dioxide may be correlated with their habitats.

Impacts of elevated water carbon dioxide partial pressure at two temperatures on Atlantic salmon ( Salmo salar L.) parr growth and haematology

Distribution of methane and carbon dioxide concentrations in the near-surface zone and their genetic characterization at the abandoned “Nowa Ruda” coal mine (Lower Silesian Coal Basin, SW Poland)

STUDIES IN THE PHYSIOLOGY OF SPERMATOZOA

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

Comparative analysis of separation technologies for processing carbon dioxide rich natural gas in ultra-deepwater oil fields

Carbon dioxide is widely used for a variety of purposes. As it is a normal constituent of air, the public generally regards it as safe. Although low concentrations of carbon dioxide are not harmful to human beings, high concentrations are toxic, and can cause serious harm, including cardiac arrest. Only a limited number of cases of carbon dioxide intoxication have been reported in Korea, and they have all been mild, with no cases of cardiac arrest following acute exposure to high concentrations of carbon dioxide, reported previously. We describe a case of carbon dioxide poisoning following an explosion of a carbon dioxide tank, which led to cardiac arrest in a 66-year-old patient. This cardiac arrest could have been avoided if the patient was fully aware of the hazardous effects and serious consequences of exposure to high concentrations of carbon dioxide.

Excystment of the metacercaria ofFasciola hepaticais an active process and occurs in two stages—activation and emergence. Activation is initiated by high concentrations of carbon dioxide, reducing conditions and a temperature about 39 °C. The reducing conditions increase the rate of action of the other two stimuli. The carbon dioxide stimulus need only be applied for 5 min, but the exposure time to the reducing conditions has to be of the order of 30 min. Changes in the order of application of the stimuli carbon dioxide and redox potential have no effect.The second phase, emergence, is triggered by bile. Metacercariae were held in an activated condition for 24 h, and when bile was added emergence took place normally.During excystment the metacercariae exhibit a complex behaviour pattern. After activation there is an initial period of rotatory activity, but after about 20 min a quiescent phase ensues when the metacercariae contract away from the cyst wall at an imperceptible rate. This behaviour occurs in response to stimulus from a high concentration of carbon dioxide and a temperature about 39 °C. When the metacercariae are exposed to bile the second phase of activity is initiated, consisting of antero-posterior thrusting movements directed against the ventral side of the cyst wall. Within about 15 min the juvenile flukes escape through a small circular hole in the ventral surface of the cyst wall which corresponds to the ventral plug region.