Search results for "dioxide"
showing 10 items of 1250 documents
CO2 flux measurements in volcanic areas using the dynamic concentration method: the influence of the soil permeability.
2006
In order to evaluate the influence of soil permeability on soil CO2 flux measurements performed with the dynamic concentration method, several tests were carried out using soils characterized by different permeability values and flow rates. A special device was assembled in the laboratory to create a one-dimensional gas flow through a soil of known permeability. Using the advective-diffusion theory, a physical model to predict soil concentration gradients was also developed. The calculated values of CO2 concentrations at different depths were compared with those measured during the tests and a good agreement was found. Four soils with different gas permeability (3.6 x 10(-2) to 1.23 x 10(2)…
Impact of resection margin status and revision transoral laser microsurgery in early glottic cancer: analysis of organ preservation and local disease…
2022
Abstract Introduction Transoral laser microsurgery represents the treatment of choice for early glottic cancer. Its use and effectiveness are mainly related to laryngeal exposure and deep extension of tumor. Histopathologic assessment of surgical margin presents a main issue about transoral laser microsurgery and complete oncological excision. Objective The aim was to analyze the impact of revision surgery on organ preservation and local disease control in patients with early glottic cancer treated by transoral laser microsurgery. Methods We carried out a retrospective study on a cohort of 153 patients with early glottic cancer (Tis, T1, T2) treated by transoral laser microsurgery. Resectio…
CO(2)-laser treatment of laryngeal amyloidosis.
2003
Four consecutive female patients (age: 14–47 years) with laryngeal amyloidosis, treated with endoscopic CO2-laser surgery, entered the study. All patients underwent periodic microlaryngoscopies following surgery to confirm the adequacy of the surgical resection. Recurrences or suspected lesions were resected and fibrin deposits were removed to prevent the formation of synechiae or healing adhesions. After two negative microlaryngoscopies, performed two months apart, the patients were followed-up approximately every six months over a period from six months to 18 years, with no evidence of recurrences. The endoscopic CO2-laser technique is highly effective in the treatment of localized laryng…
CO Oxidation on Cationic Gold Clusters: A Theoretical Study
2008
Aiming at understanding the elementary steps governing the oxidation of CO catalyzed by dispersed or supported gold nanoclusters, the reactivity of molecular species, such as O2 and CO, on neutral and positively charged Au13 clusters have been studied using a DFT approach. Two CO oxidation mechanisms have been simulated, involving respectively the adsorption of CO and O2 on adjacent catalytic sites (two-sites mechanism) and the competitive interaction of the reactants on the same site (single-site mechanism). It is demonstrated that in the former scheme a definite interaction of CO and O2 with both the charged and neutral cluster is effective, but that a chemical reaction between the adsorb…
(Table 1) Geochemistry of ODP Site 160-963 sediments
2010
The Mediterranean Sea acts as a miniature ocean with the development of its own conveyor belt. It constitutes an ideal location to study and forecast how the marine environment responds to rapid climatic change. Here we present a palaeoenvironmental study carried out on the sediments of ODP Site 963, recovered in the Sicily Channel, the sill which divides the western from the eastern Mediterranean basin. We focused on the transition between the penultimate glacial (MIS 6) and the last interglacial (MIS 5), between approximately 130 and 115 kyr BP. A novel approach is proposed, taking into account centennial-scale geochemical data on major elements, selected trace elements, and yttrium and R…
Exocrine Pancreatic Function in Girls with Anorexia Nervosa
2021
Objectives: To assess pancreatic exocrine function in patients with anorexia nervosa using a breath test with 13C-labeled mixed triglycerides (MTG-BT) and to determine the relationship between the test results and selected biochemical and hormonal parameters. Material and methods: Anthropometric measurements, biochemical and hormonal parameters (serum leptin, soluble leptin receptor (sLR), acylated and desacylated ghrelin, free leptin index (FLI)), and MTG-BT were performed in a group of 31 girls with the restrictive type of AN, as well as 38 healthy girls (C). Results: The average cumulative dose of 13C-triglycerides recovered with exhaled air (%CD) was similar in both study groups, while …
The minimal model of Hahn for the Calvin cycle.
2018
There are many models of the Calvin cycle of photosynthesis in the literature. When investigating the dynamics of these models one strategy is to look at the simplest possible models in order to get the most detailed insights. We investigate a minimal model of the Calvin cycle introduced by Hahn while he was pursuing this strategy. In a variant of the model not including photorespiration it is shown that there exists exactly one positive steady state and that this steady state is unstable. For generic initial data either all concentrations tend to infinity at lates times or all concentrations tend to zero at late times. In a variant including photorespiration it is shown that for suitable v…
Modeling of an annular photocatalytic reactor for water purification: oxidation of pesticides.
2004
Photocatalytic oxidation (PCO) over titanium dioxide (TiO2) is a “green” sustainable process for the treatment and purification of water and wastewater. However, the application of PCO for wastewater treatment on an industrial scale is currently hindered by a lack of simple mathematical models that can be readily applied to reactor design. Current models are either too simplistic or too rigorous to be useful in photocatalytic reactor design, scale-up, and optimization. In this paper a simple mathematical model is presented for slurry, annular, photocatalytic reactors that still retains the essential elements of a rigorous approach while providing simple solutions. The model extends the appl…
Supercritical CO2 extraction of essential oil from orange peel. Effect of operation conditions on the extract composition
1999
Abstract The supercritical fluid extraction (SFE) of orange essential oil was studied using dehydrated orange peel (0.0538 kg H2O/kg dm) from naveline cultivars as raw material and CO2 as solvent. The effect of operation conditions was analyzed in a series of experiments at temperatures between 293 and 323 K and pressures between 8 and 28 MPa. The collected extracts were analyzed and the relative composition of the essential oil was determined. Limonene was the principal component extracted, the optimum conditions for limonene extraction were 12.5 MPa and 308 K, in these conditions limonene represents more than 99.5% of the essential oil. Within the operating range conditions, the optimum f…
Solubilities of Essential Oil Components of Orange in Supercritical Carbon Dioxide
2000
The solubilities of pure limonene and linalool in compressed carbon dioxide have been measured using a flow apparatus at 318.2 K and 328.2 K and pressures ranging from 69 bar to 111 bar. The solubilities were successfully modeled using equations of state (Peng−Robinson, Soave−Redlich−Kwong, 3P1T, Dohrn and Prausnitz nopolar) and a semiempirical equation (Chrastill model). The generalized parameters for the Peng−Robinson EOS were obtained for each system. These parameters were independent of temperature, and they reproduce successfully all data available in the literature. The results show that the solubility of limonene in supercritical carbon dioxide was bigger than the solubility of linal…