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High CO2 Concentrations (high + co2_concentration)
Selected AbstractsEffect of CaO on NH3 + NO + O2 reaction system in the absence and presence of high concentration CO2ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2010Tianjin Li Abstract The effect of CaO on the NH3 + NO + O2 reaction system at 650,850 °C was investigated. High CO2 concentration was added to investigate the effect of CaCO3 on this reaction system also. Experimental results showed that CaO had a strong catalytic effect on NH3 decomposition, NH3 oxidation by O2 to NO, and NO reduction by NH3 in the absence of O2. The overall effect of CaO on the NO + NH3 + O2 reaction was to enhance NH3 oxidation by O2 to produce more NO. A small amount of NO2 and no N2O was detected in the outlet gas stream over CaO in the NH3 + NO + O2 reaction. NO2 formation decreased with temperature increase. NO2 formation in the NH3 + NO + O2 reaction over CaO was attributed to the oxidization of NH3 and NO by O2. The performance of CaCO3 was different from CaO. NH3 decomposition was promoted, but NH3 oxidation to NO was inhibited after CaO was converted to CaCO3. No catalytic activity for NO reduction was detected in NO + NH3 reaction over CaCO3, but strong activity for NH3 decomposition was observed. NO and NH3 outlet concentration over CaCO3 in the NH3 + NO + O2 reaction was lower and higher, respectively, than that of CaO, which was mainly due to the difference of CaO and CaCO3 for NH3 oxidation. NO2 formation was inhibited, but N2O was observed over CaCO3. N2O formation increased with temperature increase at 650,750 °C, and then decreased at 750,850 °C. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Evaluation of plastic packages for guava refrigerated preservationPACKAGING TECHNOLOGY AND SCIENCE, Issue 1 2001Angelo Pedro Jacomino Abstract Guavas cv. ,Kumagai' were packed in several plastic materials and stored at 10°C and 85,90% relative humidity (RH) for 7, 14, 21 and 28 days (+3 days at 25°C). The plastic materials studied were: multilayer co-extruded polyolephine film with selective permeability (PSP), low-density polyethylene film (LDPE), LDPE film with mineral incorporation (LDPEm) and heat-shrinkable polyolephine film (SHR). Guavas not packed were taken as control samples. The physicochemical characteristics of the fruits, O2 and CO2 transmission rates of the packaging materials and gas composition at the package headspace were evaluated. The LDPE film, 69,µm in thickness, with the lowest permeability to both O2 and CO2, led to anaerobiosis and high CO2 concentration inside the packages and promoted physiological disturbances and changes in fruit flavour. The SHR film, 15,µm in thickness, was the most permeable to CO2 and had quite high O2 transmission, which modified the inner atmosphere of the packages slightly. The fruits packed in this film showed a poorer quality than the controls, possibly due to the heat produced during the shrinking of the film. The LDPEm film, 24,µm in thickness, was almost as permeable to CO2 but had reduced O2 transmission, promoting an atmosphere of equilibrium of 3% O2 and 4.5% CO2. Fruits packed in this film kept their skin colour and pulp firmness, suitable for consumption up to 14 days. The PSP film, 35,µm in thickness, had the greatest O2 transmission but just over half of the CO2 transmission of LDPEm, promoting an atmosphere of equilibrium of 0.5% O2 and 4.5% CO2 inside the packages. Fruits packed in such packages kept their physicochemical characteristics up to 21 days. Copyright © 2001 John Wiley & Sons, Ltd. [source] Photosynthetic Responses of a Temperate Liana to Xylella fastidiosa Infection and Water StressJOURNAL OF PHYTOPATHOLOGY, Issue 1 2004A. J. McElrone Abstract Xylella fastidiosa is a xylem-limited bacterial plant pathogen that causes bacterial leaf scorch in its hosts. Our previous work showed that water stress enhances leaf scorch symptom severity and progression along the stem of a liana, Parthenocissus quinquefolia, infected by X. fastidiosa. This paper explores the photosynthetic gas exchange responses of P. quinquefolia, with the aim to elucidate mechanisms behind disease expression and its interaction with water stress. We used a 2 × 2-complete factorial design, repeated over two growing seasons, with high and low soil moisture levels and infected and non-infected plants. In both years, low soil moisture levels reduced leaf water potentials, net photosynthesis and stomatal conductance at all leaf positions, while X. fastidiosa -infection reduced these parameters at basally located leaves only. Intercellular CO2 concentrations were reduced in apical leaves, but increased at the most basal leaf location, implicating a non-stomatal reduction of photosynthesis in leaves showing the greatest disease development. This result was supported by measured reductions in photosynthetic rates of basal leaves at high CO2 concentrations, where stomatal limitation was eliminated. Repeated measurements over the summer of 2000 showed that the effects of water stress and infection were progressive over time, reaching their greatest extent in September. By reducing stomatal conductances at moderate levels of water stress, P. quinquefolia maintained relatively high leaf water potentials and delayed the onset of photosynthetic damage due to pathogen and drought-induced water stress. In addition, chlorophyll fluorescence measurements showed that P. quinquefolia has an efficient means of dissipating excess light energy that protects the photosynthetic machinery of leaves from irreversible photoinhibitory damage that may occur during stress-induced stomatal limitation of photosynthesis. However, severe stress induced by disease and drought eventually led to non-stomatal decreases in photosynthesis associated with leaf senescence. [source] The Glycine Decarboxylase Complex is not Essential for the Cyanobacterium Synechocystis sp.PLANT BIOLOGY, Issue 1 2005Strain PCC 680 Abstract: In order to investigate the metabolic importance of glycine decarboxylase (GDC) in cyanobacteria, mutants were generated defective in the genes encoding GDC subunits and the serine hydroxymethyl-transferase (SHMT). It was possible to mutate the genes for GDC subunits P, T, or H protein in the cyanobacterial model strain Synechocystis sp. PCC 6803, indicating that GDC is not necessary for cell viability under standard conditions. In contrast, the SHMT coding gene was found to be essential. Almost no changes in growth, pigmentation, or photosynthesis were detected in the GDC subunit mutants, regardless of whether or not they were cultivated at ambient or high CO2 concentrations. The mutation of GDC led to an increased glycine/serine ratio in the mutant cells. Furthermore, supplementation of the medium with low glycine concentrations was toxic for the mutants but not for wild type cells. Conditions stimulating photorespiration in plants, such as low CO2 concentrations, did not induce but decrease the expression of the GDC and SHMT genes in Synechocystis. It appears that, in contrast to heterotrophic bacteria and plants, GDC is dispensable for Synechocystis and possibly other cyanobacteria. [source] | ||||||||||