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Partial Pressure (partial + pressure)
Kinds of Partial Pressure Selected AbstractsEffect of Oxygen Partial Pressure During Firing on the High AC Field Response of BaTiO3 DielectricsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2010Ichiro Fujii The effect of oxygen partial pressure during firing on the high field dielectric response of formulated and undoped BaTiO3 ceramics was investigated. For formulated ceramics, the dielectric constant of both oxygen- and air-fired samples increased almost linearly with the amplitude of the ac-driving field. Formulated BaTiO3 samples sintered in a reducing atmosphere produced a sublinear increase in the permittivity with the ac field amplitude. For undoped BaTiO3 ceramics, the dielectric constant increased sublinearly over a wide range of oxygen partial pressures during firing. It is proposed for the formulated ceramics that the dopant-oxygen vacancy defect dipoles in the shell region accounted for the curvature in the field dependence of the permittivity. These defects appear to add a concentration of weak pinning centers to the potential energy profile through which domain walls move. [source] Effect of Oxygen Partial Pressure on the Formation of Metastable Phases from an Undercooled YbFeO3 Melt Using an Aerodynamic LevitatorJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2009Malahalli S. Vijaya Kumar The Yb2O3,Fe2O3 system was studied to investigate the effect of oxygen partial pressure on the formation of metastable phases over a wide range of oxygen partial pressures from 105 to 10,1 Pa. Two kinds of metastable phases, with space groups of P63cm and P63/mmc, were found through rapid solidification of an undercooled YbFeO3 melt in an atmosphere with reduced Po2. The crystal structure of the as-solidified samples changed from orthorhombic Pbnm to hexagonal P63cm and P63/mmc with decreasing Po2. X-ray diffractometric and scanning electron microscopic results confirmed the existence of various phases in the as-solidified samples. The stabilities of each phase were studied by annealing the bulk sample in the thermogravimetric,differential thermal analysis (TG-DTA) furnace up to 1673 K, and the equilibrium phase diagram was constructed for the Yb,Fe,O system at 1473 K. TG analysis showed an increase of the sample mass during annealing and revealed that the existence of Fe2+, which has an ionic radius larger than that of Fe3+, decreases the tolerance factor and therefore destabilizes the perovskite structure. [source] ChemInform Abstract: Impact of Oxygen Partial Pressure on the Ruddlesden,Popper Series Nd2-2xSr1+2xMn2O7: Oxygen Vacancy Formation and Ordering.CHEMINFORM, Issue 41 2001Julie E. Millburn Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] High-Temperature Stability of Lanthanum Orthophosphate (Monazite) on Silicon Carbide at Low Oxygen Partial PressuresJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2008Michael K. Cinibulk The stability of lanthanum orthophosphate (LaPO4) on SiC was investigated using a LaPO4 -coated SiC fiber at 1200°,1400°C at low oxygen partial pressures. A critical oxygen partial pressure exists below which LaPO4 is reduced in the presence of SiC and reacts to form La2O3 or La2Si2O7 and SiO2 as the solid reaction products. The critical oxygen partial pressure increases from ,0.5 Pa at 1200°C to ,50 Pa at 1400°C. Above the critical oxygen partial pressure, a thin SiO2 film, which acts as a reaction barrier, exists between the SiC fiber and the LaPO4 coating. Continuous LaPO4 coatings and high strengths were obtained for coated fibers that were heated at or below 1300°C and just above the critical oxygen partial pressure for each temperature. At temperatures above 1300°C, the thin LaPO4 coating becomes morphologically unstable due to free-energy minimization as the grain size reaches the coating thickness, which allows the SiO2 oxidation product to penetrate the coating. [source] Gravity is an important determinant of oxygenation during one-lung ventilationACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 6 2010L. L. SZEGEDI Background: The role of gravity in the redistribution of pulmonary blood flow during one-lung ventilation (OLV) has been questioned recently. To address this controversial but clinically important issue, we used an experimental approach that allowed us to differentiate the effects of gravity from the effects of hypoxic pulmonary vasoconstriction (HPV) on arterial oxygenation during OLV in patients scheduled for thoracic surgery. Methods: Forty patients with chronic obstructive pulmonary disease scheduled for right lung tumour resection were randomized to undergo dependent (left) one-lung ventilation (D-OLV; n=20) or non-dependent (right) one-lung ventilation (ND-OLV; n=20) in the supine and left lateral positions. Partial pressure of arterial oxygen (PaO2) was measured as a surrogate for ventilation/perfusion matching. Patients were studied before surgery under closed chest conditions. Results: When compared with bilateral lung ventilation, both D-OLV and ND-OLV caused a significant and equal decrease in PaO2 in the supine position. However, D-OLV in the lateral position was associated with a higher PaO2 as compared with the supine position [274.2 (77.6) vs. 181.9 (68.3) mmHg, P<0.01, analysis of variance (ANOVA)]. In contrast, in patients undergoing ND-OLV, PaO2 was always lower in the lateral as compared with the supine position [105.3 (63.2) vs. 187 (63.1) mmHg, P<0.01, ANOVA]. Conclusion: The relative position of the ventilated vs. the non-ventilated lung markedly affects arterial oxygenation during OLV. These data suggest that gravity affects ventilation,perfusion matching independent of HPV. [source] 2224: Oxygenation of the human retinaACTA OPHTHALMOLOGICA, Issue 2010E STEFANSSON Purpose Partial pressure of oxygen in the optic nerve and retina is regulated by the intraocular pressure and systemic blood pressure, the resistance in the blood vessels and oxygen consumption of the tissue. The PO2 is autoregulated and moderate changes in intraocular pressure, blood pressure or tissue oxygen consumption do not affect the retinal and optic nerve oxygen tension. Methods If the intraocular pressure is increased above 40 mmHg or the ocular perfusion pressure decreased below 50 mmHg the autoregulation is overwhelmed and the optic nerve becomes hypoxic. The levels of perfusion pressure that lead to optic nerve hypoxia in the laboratory correspond remarkably well to the levels that increase the risk of glaucomatous optic nerve atrophy in human glaucoma patients. Medical intervention can affect optic nerve PO2. Lowering the intraocular pressure tends to increase the optic nerve PO2, even though this effect may be masked by the autoregulation when the optic nerve PO2 and perfusion pressure is in the normal range. Results Carbonic anhydrase inhibitors increase retinal PO2 through a mechanism of vasodilatation and lowering of the intraocular pressure. Carbonic anhydrase inhibition reduces the removal of CO2 from the tissue and the CO2 accumulation induces vasodilatation resulting in increased blood flow and improved oxygen supply. This effect is inhibited by indomethacin but not other cyclo-oxygenase inhibitors. Conclusion Carbonic anhydrase inhibitors increase retinal blood flow and increase oxygen delivery. Glaucoma drugs and glaucoma surgery lower intraocular pressure, increase ocular perfusion pressure and blood flow. Demand of oxygen by retinal cells may be reduced through apoptosis and tissue atrophy, as well as active destruction of tissue by laser photocoagulation. [source] Randomized trial comparing natural and synthetic surfactant: increased infection rate after natural surfactant?ACTA PAEDIATRICA, Issue 5 2000AK Kukkonen The efficacy of a natural porcine surfactant and a synthetic surfactant were compared in a randomized trial. In three neonatal intensive care units, 228 neonates with respiratory distress and a ratio of arterial to alveolar partial pressure of oxygen <0.22 were randomly assigned to receive either Curosurf 100mgkg,1 or Exosurf Neonatal 5 ml kg,1. After Curosurf, the fraction of inspired oxygen was lower from 15min (0.45 ± 0.22 vs 0.70 ± 0.22, p = 0.0001) to 6 h (0.48 ± 0.26 vs 0.64 ± 0.23,p= 0.0001) and the mean airway pressure was lower at 1 h (8.3 3.2 mmH2O vs 9.4 ± 3.1 mmH2O ,= 0.01). Thereafter the respiratory parameters were similar. The duration of mechanical ventilation (median 6 vs 5 d) and the duration of oxygen supplementation (median 5 vs 4 d) were similar for Curosurf and Exosurf After Curosurf, C-reactive protein value over 40 mg r1 occurred in 45% (vs 12%; RR 3.62, 95%CI 2.12-6.17, p = 0.001), leukopenia in 52% (vs 28%; RR 1.85, 95%CI 1.31-2.61, ,= 0.001) and bacteraemia in 11% (vs 4%; RR3.17, 95%CI 1.05-9.52, p < 0.05). We conclude that when given as rescue therapy Curosurf had no advantage compared with Exosurf in addition to the more effective initial response. Curosurf may increase the risk of infection. [source] Heat treatment induced structural and optical properties of rf magnetron sputtered tantalum oxide filmsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 3 2007S. V. Jagadeesh Chandra Abstract Rf magnetron sputtering technique was employed for preparation of tantalum oxide films on quartz and crystalline silicon (111) substrates held at room temperature by sputtering of tantalum in an oxygen partial pressure of 1x10 -4 mbar. The films were annealed in air for an hour in the temperature range 573 , 993 K. The effect of annealing on the chemical binding configuration, structure and optical absorption of tantalum oxide films was systematically studied. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Floating zone growth of CuO under elevated oxygen pressure and its relevance for the crystal growth of cupratesCRYSTAL RESEARCH AND TECHNOLOGY, Issue 1-2 2005G. Behr Abstract CuO single crystals have been grown from the melt by a floating zone method with optical heating at elevated oxygen pressures 3.5 to 5.5 MPa and growth rates as high as 10 mm/h. Melting experiments and recalculated Cu-O phase diagram data show that CuO melts incongruently. The melting temperature increases and the concentration difference between the melt and the CuO phase decreases for rising oxygen partial pressure. Accordingly, increasing the oxygen partial pressure improves the growth process by reducing both the significant oxygen loss during melting as well as the composition difference at the growth interface. The results on CuO provide important information for the crystal growth of more complex cuprates. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Subsurface addition emission modelENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 1 2005Allen Hatfield PhD Subsurface addition is commonly used in the chemical industry as a means of ensuring that the incoming reagent is distributed uniformly within a batch as the addition proceeds. The difference between subsurface addition and the typical above-surface addition is in how the inlet liquid stream enters the vessel. When calculating the process vent emissions for an above-surface addition one considers the partial pressure of the inlet stream components along with the batch components. This is because both mixtures have direct exposure to the vessel headspace during the addition process. For subsurface addition, volatile compounds that are contained in the inlet stream are exposed to the headspace only as they appear in the batch during the addition process. The purpose of this paper is to present a model for estimating the vent emissions for subsurface addition processes based on the integrated average liquid-phase composition. © 2004 American Institute of Chemical Engineers Environ Prog, 2004 [source] Relationship between Condition of Deposition and Properties of W-Ti-N Thin Films Prepared by Reactive Magnetron Sputtering,ADVANCED ENGINEERING MATERIALS, Issue 3 2006V. Kuchuk A correlation between the film properties of nitrides, oxides etc., and their structure, is of fundamental importance , not only for thin solid films physics but also for practical applications. The structure of the films depends on deposition methods and their parameters. The relationship between properties (chemical and phase compositions, surface morphology, and electrical resistivity) and nitrogen partial pressure of reactive magnetron sputtered W-Ti-N thin films has been discussed here in detail. [source] Quantification of myoglobin deoxygenation and intracellular partial pressure of O2 during muscle contraction during haemoglobin-free medium perfusionEXPERIMENTAL PHYSIOLOGY, Issue 5 2010Hisashi Takakura Although the O2 gradient regulates O2 flux from the capillary into the myocyte to meet the energy demands of contracting muscle, intracellular O2 dynamics during muscle contraction remain unclear. Our hindlimb perfusion model allows the determination of intracellular myoglobin (Mb) saturation () and intracellular oxygen tension of myoglobin () in contracting muscle using near infrared spectroscopy (NIRS). The hindlimb of male Wistar rats was perfused from the abdominal aorta with a well-oxygenated haemoglobin-free Krebs,Henseleit buffer. The deoxygenated Mb (,[deoxy-Mb]) signal was monitored by NIRS. Based on the value of ,[deoxy-Mb],,,and,,were calculated, and the time course was evaluated by an exponential function model. Both,,and,,started to decrease immediately after the onset of contraction. The steady-state values of,,and,,progressively decreased with relative work intensity or muscle oxygen consumption. At the maximal twitch rate,,,and,,were 49% and 2.4 mmHg, respectively. Moreover, the rate of release of O2 from Mb at the onset of contraction increased with muscle oxygen consumption. These results suggest that at the onset of muscle contraction, Mb supplies O2 during the steep decline in,, which expands the O2 gradient to increase the O2 flux to meet the increased energy demands. [source] Ventilatory control in humans: constraints and limitationsEXPERIMENTAL PHYSIOLOGY, Issue 2 2007Susan A. Ward Below the lactate threshold (,L), ventilation responds in close proportion to CO2 output to regulate arterial partial pressure of CO2. While ventilatory control models have traditionally included proportional feedback (central and carotid chemosensory) and feedforward (central and peripheral neurogenic) elements, the mechanisms involved remain unclear. Regardless, putative control schemes have to accommodate the close dynamic ,coupling' between and . Above ,L, is driven down to constrain the fall of arterial pH by a compensatory hyperventilation, probably of carotid body origin. When requirements are high (as in highly fit endurance athletes), can attain limiting proportions. Not only does this impair gas exchange at these work rates, but there may be an associated high metabolic cost for generation of respiratory muscle power, which may be sufficient to divert a fraction of the cardiac output away from the muscles of locomotion to the respiratory muscles, further compromising exercise tolerance. [source] Tolerance to low O2: lessons from invertebrate genetic modelsEXPERIMENTAL PHYSIOLOGY, Issue 2 2006Gabriel G. Haddad There have been extensive studies and experiments on cells, tissues and animals that are susceptible to low O2, and many pathways have been discovered that can lead to injury in mammalian tissues. But other pathways that can help in the survival of low O2 have also been discovered in these same tissues. It should be noted, however, that the mechanisms that can lead to better survival in susceptible mammalian tissues have quantitatively a ,narrow range' for recovery, since these tissues are inherently at risk. Another strategy for understanding the susceptibility of organisms is to learn about pathways used by anoxia-resistant animals. Approximately a decade ago, I and my co-workers discovered that one such animal, Drosophila melanogaster, is very tolerant of low O2. Here, I detail some of the studies that we performed and the strategies that we developed to understand the mechanisms that underlie the fascinating resistance of Drosophila to measured partial pressure of O2 of zero. We employed three ideas to try to address our questions: (1) mutagenesis screens to identify loss-of-function mutants; (2) microarrays on adapted versus naïve flies; and (3) studying cell biology and physiology of genes that seem important in flies and mammals. The hope is to learn from these studies about the fundamental basis of tolerance to the lack of O2, and with this knowledge be able to develop better therapies for the future. [source] The Contribution of Chemoreflex Drives to Resting Breathing in ManEXPERIMENTAL PHYSIOLOGY, Issue 1 2001Safraaz Mahamed The contribution of automatic drives to breathing at rest, relative to behavioural drives such as ,wakefulness', has been a subject of debate. We measured the combined central and peripheral chemoreflex contribution to resting ventilation using a modified rebreathing method that included a prior hyperventilation and addition of oxygen to maintain isoxia at a PET,O2 (end-tidal partial pressure of oxygen) of 100 mmHg. During rebreathing, ventilation was unrelated to PET,CO2 (end-tidal partial pressure of carbon dioxide) in the hypocapnic range, but after a threshold PET,CO2 was exceeded, ventilation increased linearly with PET,CO2. We considered the sub-threshold ventilation to be an estimate of the behavioural drives to breathe (mean ± S.E.M. = 3.1 ± 0.5 l min,1), and compared it to ventilation at rest (mean ± S.E.M. = 9.1 ± 0.7 l min,1). The difference was significant (Student's paired t test, P < 0.001). We also considered the threshold PCO2 observed during rebreathing to be an estimate of the chemoreflex threshold at rest (mean ± S.E.M. = 42.0 ± 0.5 mmHg). However, PET,CO2 during rebreathing estimates mixed venous or tissue PCO2, whereas the resting PET,CO2 during resting breathing estimates Pa,CO2 (arterial partial pressure of carbon dioxide). The chemoreflex threshold measured during rebreathing was therefore reduced by the difference in PET,CO2 at rest and at the start of rebreathing (the plateau estimates the mixed venous PCO2 at rest) in order to make comparisons. The corrected chemoreflex thresholds (mean ± S.E.M. = 26.0 ± 0.9 mmHg) were significantly less (paired Student's t test, P < 0.001) than the resting PET,CO2 values (mean ± S.E.M. = 34.3 ± 0.5 mmHg). We conclude that both the behavioural and chemoreflex drives contribute to resting ventilation. [source] Testing a Vapour-fed PBI-based Direct Ethanol Fuel CellFUEL CELLS, Issue 5 2009J. Lobato Abstract This work is focused on the application and performance of a high temperature PBI-based direct ethanol fuel cell, studying the influence of some operating variables such as the temperature, ethanol concentration and oxygen partial pressure. An increase in the temperature resulted in an improvement of the cell performance due to the enhanced electrodic kinetic and electrolyte conductivity. An ethanol/water weight ratio between 0.25 and 0.5 was found to be suitable for providing both enough water and fuel availability to make the ethanol oxidation possible. Measurements of the ethanol crossover at different temperatures and concentrations were carried out. An intermittent lifetime test showed that the cell, after several hours, was able to reach stability. Moreover, its performance was completely reversible with no perceptible losses for 7,days. Finally, tests using bio-ethanol as fuel were performed, with no significant power losses. This final feature is of special interest from a practical ,green' point of view. [source] Leaf dark respiration as a function of canopy position in Nothofagus fusca trees grown at ambient and elevated CO2 partial pressures for 5 yearsFUNCTIONAL ECOLOGY, Issue 4 2001K. L. Griffin Summary 1,Mass-based and area-based rates of respiration, leaf nitrogen content, leaf total protein content, non-structural carbohydrates and leaf mass per unit area (LMA) all decreased with depth in the canopy of Nothofagus fusca (Hook. F.) Oerst. (Red beech) trees grown for 5 years at ambient (36 Pa) or elevated (66 Pa) CO2 partial pressures. 2Elevated CO2 partial pressure had a strong effect on dark respiration, decreasing both mass-based and area-based rates at all canopy positions, but had little or no effect on leaf physical and biochemical properties. 3Leaf sugars, starch, protein, N and LMA were all correlated with respiration rate, and are therefore strong predictors of area-based dark respiration rates. The y axis intercept of regressions of respiration rate on mean leaf N, protein, starch and LMA was lower for plants grown at elevated compared to ambient CO2 partial pressures because of the differential effect of growth at elevated CO2 partial pressure on leaf gas-exchange, chemical and physical characteristics. 4,The lower respiration rates for leaves from trees grown at elevated CO2 partial pressure resulted in a significant increase in the ratio of light-saturated net photosynthesis to respiration, increasing the potential carbon-use efficiency of these leaves. [source] Fabrication and Electrochemical Properties of Epitaxial Samarium-Doped Ceria Films on SrTiO3 -Buffered MgO SubstratesADVANCED FUNCTIONAL MATERIALS, Issue 11 2009Simone Sanna Abstract Thin films of samarium-oxide-doped (20,mol%) ceria (SDC) are grown by pulsed-laser deposition (PLD) on (001) MgO single-crystal substrates. SrTiO3 (STO) prepared by PLD is used as a buffer layer on the MgO substrates to enable epitaxial growth of the fluorite-structured SDC film; the STO layer provides a proper crystalline match between SDC and MgO, resulting in highly crystalline, epitaxial SDC films grown in the (001) orientation. Film conductivity is evaluated by electrochemical impedance spectroscopy measurements, which are performed at various temperatures (400,775,°C) in a wide range of oxygen partial pressure (pO2) values (10,25,1,atm) in order to separate ionic and electronic conductivity contributions. At 700,°C, SDC/STO films on (100) MgO exhibit a dominant ionic conductivity of about 7,×,10,2,S cm,1, down to pO2 values of about 10,15,atm. The absence of grain boundaries make the SDC/STO/MgO heterostructures stable to oxidation-reduction cycles at high temperatures, in contrast to that observed for the more disordered SDC/STO films, which degraded after hydrogen exposure. [source] The effect of ocean acidification and temperature on the fertilization and embryonic development of the Sydney rock oyster Saccostrea glomerata (Gould 1850)GLOBAL CHANGE BIOLOGY, Issue 9 2009LAURA M. PARKER Abstract This study investigated the synergistic effects of ocean acidification (caused by elevations in the partial pressure of carbon dioxide pCO2) and temperature on the fertilization and embryonic development of the economically and ecologically important Sydney rock oyster, Saccostrea glomerata (Gould 1850). As pCO2 increased, fertilization significantly decreased. The temperature of 26 °C was the optimum temperature for fertilization, as temperature increased and decreased from this optimum, fertilization decreased. There was also an effect of pCO2 and temperature on embryonic development. Generally as pCO2 increased, the percentage and size of D-veligers decreased and the percentage of D-veligers that were abnormal increased. The optimum temperature was 26 °C and embryonic development decreased at temperatures that were above and below this temperature. Abnormality of D-veligers was greatest at 1000 ppm and 18 and 30 °C (,90%) and least at 375 ppm and 26 °C (,4%). Finally prolonged exposure of elevated pCO2 and temperature across early developmental stages led to fewer D-veligers, more abnormality and smaller sizes in elevated CO2 environments and may lead to lethal effects at suboptimal temperatures. Embryos that were exposed to the pCO2 and temperature treatments for fertilization and embryonic development had fewer D-veligers, greater percentage of abnormality and reduced size than embryos that were exposed to the treatments for embryonic development only. Further at the elevated temperature of 30 °C and 750,1000 ppm, there was no embryonic development. The results of this study suggest that predicted changes in ocean acidification and temperature over the next century may have severe implications for the distribution and abundance of S. glomerata as well as possible implications for the reproduction and development of other marine invertebrates. [source] Interacting effects of CO2 partial pressure and temperature on photosynthesis and calcification in a scleractinian coralGLOBAL CHANGE BIOLOGY, Issue 11 2003Stéphanie Reynaud Abstract We show here that CO2 partial pressure (pCO2) and temperature significantly interact on coral physiology. The effects of increased pCO2 and temperature on photosynthesis, respiration and calcification rates were investigated in the scleractinian coral Stylophora pistillata. Cuttings were exposed to temperatures of 25°C or 28°C and to pCO2 values of ca. 460 or 760 ,atm for 5 weeks. The contents of chlorophyll c2 and protein remained constant throughout the experiment, while the chlorophyll a content was significantly affected by temperature, and was higher under the ,high-temperature,high- pCO2' condition. The cell-specific density was higher at ,high pCO2' than at ,normal pCO2' (1.7 vs. 1.4). The net photosynthesis normalized per unit protein was affected by both temperature and pCO2, whereas respiration was not affected by the treatments. Calcification decreased by 50% when temperature and pCO2 were both elevated. Calcification under normal temperature did not change in response to an increased pCO2. This is not in agreement with numerous published papers that describe a negative relationship between marine calcification and CO2. The confounding effect of temperature has the potential to explain a large portion of the variability of the relationship between calcification and pCO2 reported in the literature, and warrants a re-evaluation of the projected decrease of marine calcification by the year 2100. [source] A study of the effect of a resistive heat moisture exchanger (trachinaze) on pulmonary function and blood gas tensions in patients who have undergone a laryngectomy: A randomized control trial of 50 patients studied over a 6-month periodHEAD & NECK: JOURNAL FOR THE SCIENCES & SPECIALTIES OF THE HEAD AND NECK, Issue 5 2003Andrew Simpson Jones MD Abstract Background. Previous work from this department has shown that resistive tracheostomy filters increase the partial pressure of oxygen in capillary blood and also provide a significant amount of heat/moisture exchange. Until now it has not been shown whether there is any long-term beneficial effect and in particular whether raised tissue oxygenation is maintained using a practical filter device. Methods. We carried out a 6-month randomized control trial including 50 laryngectomees. Twenty-five patients were treated with the Liverpool Heat Moisture Exchange device incorporating an airway resistor (Trachinaze). Another 25 patients were treated with a placebo device. Relevant subjective and objective data were collected before and at the end of the study. The objective measurements were capillary oxygen tension (which parallels blood arterial tension), carbon dioxide tension, FEV1, FVC, and PIF. Patients were reviewed at intervals throughout the study. Data were analyzed using the Mann,Whitney U test and the paired t test to test the difference between the active device and placebo at 6 months. Results. Subjective lower airway parameters, including cough, number of chest infections, mucus production, and shortness of breath at rest, were significantly improved in the active group compared with the placebo group. The objective parameters FEV1, FVC, and PIF were not significantly different. Capillary oxygen tension, however, was highly significantly raised in the active group at 6 months. Conclusions. Trachinaze is highly superior to placebo at improving subjective pulmonary parameters, including shortness of breath. It is also superior in its ability to maintain an increased peripheral tissue oxygen tension over a 6-month period. © 2003 Wiley Periodicals, Inc. Head Neck 25: 000,000, 2003 [source] Electronic Manifestation of Cation-Vacancy-Induced Magnetic Moments in a Transparent Oxide Semiconductor: Anatase Nb:TiO2ADVANCED MATERIALS, Issue 22 2009Shixiong Zhang Nb-doped anatase TiO2 thin films grown by pulsed-laser deposition show Kondo scattering in elctronic-transport measurements, providing evidence for the formation of magnetic moments. The origin of magnetism is attributed to cation (Ti) vacancies, confirmed by X-ray absorption spectroscopy and first-principle calculations. The Ti vacancies are controlled by oxygen partial pressure during growth. [source] Larger tidal volume increases sevoflurane uptake in blood: a randomized clinical studyACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 9 2010B. ENEKVIST Background: The rate of uptake of volatile anesthetics is dependent on alveolar concentration and ventilation, blood solubility and cardiac output. We wanted to determine whether increased tidal volume (VT), with unchanged end-tidal carbon dioxide partial pressure (PETCO2), could affect the arterial concentration of sevoflurane. Methods: Prospective, randomized, clinical study. ASA physical status 2 and II patients scheduled for elective surgery of the lower abdomen were randomly assigned to one of the two groups with 10 patients in each: one group with normal VT (NVT) and one group with increased VT (IVT) achieved by increasing the inspired plateau pressure 0.04 cmH2O/kg above the initial plateau pressure. A corrugated tube added extra apparatus dead space to maintain PETCO2 at 4.5 kPa. The respiratory rate was set at 15 min,1, and sevoflurane was delivered to the fresh gas by a vaporizer set at 3%. Arterial sevoflurane tensions (Pasevo), Fisevo, PETsevo, PETCO2, PaCO2, VT and airway pressure were measured. Results: The two groups of patients were similar with regard to gender, age, weight, height and body mass index. The mean PETsevo did not differ between the groups. Throughout the observation time, arterial sevoflurane tension (mean±SE) was significantly higher in the IVT group compared with the NVT group, e.g. 1.9±0.23 vs. 1.6±0.25 kPa after 60 min of anesthesia (P<0.05). Conclusion: Ventilation with larger tidal volumes with isocapnia maintained with added dead-space volume increases the tension of sevoflurane in arterial blood. [source] Tribology,Structure Relationships in Silicon Oxycarbide Thin FilmsINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 5 2010Joseph V. Ryan Silicon oxycarbide is a versatile material system that is attractive for many applications because of its ability to tune properties such as chemical compatibility, refractive index, electrical conductivity, and optical band gap through changes in composition. One particularly intriguing application lies in the production of biocompatible coatings with good mechanical properties. In this paper, we report on the wide range of mechanical and tribological property values exhibited by silicon oxycarbide thin films deposited by reactive radio frequency magnetron sputtering. Through a change in oxygen partial pressure in the sputtering plasma, the composition of the films was controlled to produce relatively pure SiO2, carbon-doped SiC, and compositions between these limits. Hardness values were 8,20 GPa over this range and the elastic modulus was measured to be between 60 and 220 GPa. We call attention to the fit of the mechanical data to a simple additive bond-mixture model for property prediction. Tribological parameters were measured using a ball-on-disk apparatus and the samples exhibited the same general trends for friction coefficient and wear rate. One film is shown to produce variable low friction behavior and low wear rate, which suggests a solid-state self-lubrication process because of heterogeneity on the nanometer scale. [source] Novel Structural Modulation in Ceramic Sensors Via Redox Processing in Gas BuffersINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 3 2006Abdul-Majeed Azad High selectivity, enhanced sensitivity, short response time, and long shelf-life are some of the key features sought in the solid-state ceramic-based chemical sensors. As the sensing mechanism and catalytic activity are predominantly surface-dominated, benign surface features in terms of small grain size, large surface area, high aspect ratio and, open and connected porosity, are required to realize a successful material. In order to incorporate these morphological features, a technique based on rigorous thermodynamic consideration of the metal/metal oxide coexistence is described. By modulating the oxygen partial pressure across the equilibrium M/MO proximity line, formation and growth of new oxide surface on an atomic/submolecular level under conditions of "oxygen deprivation," with exotic morphological features, has been achieved in potential sensor materials. This paper describes the methodology and discusses the results obtained in the case of potential semiconducting ceramic oxide-based carbon monoxide and hydrogen sensors with enhanced characteristics. [source] The atmospheric oxidation of ethyl formate and ethyl acetate over a range of temperatures and oxygen partial pressuresINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 7 2010John J. Orlando The Cl-atom-initiated oxidation of two esters, ethyl formate [HC(O)OCH2CH3] and ethyl acetate [CH3C(O)OCH2CH3], has been studied at pressures close to 1 atm as a function of temperature (249,325 K) and O2 partial pressure (50,700 Torr), using an environmental chamber technique. In both cases, Cl-atom attack at the CH2 group is most important, leading in part to the formation of radicals of the type RC(O)OCH(O,)CH3 [R = H, CH3]. The atmospheric fate of these radicals involves competition between reaction with O2 to produce an anhydride compound, RC(O)OC(O)CH3, and the so-called ,-ester rearrangement that produces an organic acid, RC(O)OH, and an acetyl radical, CH3C(O). For both species studied, the ,-ester rearrangement is found to dominate in air at 1 atm and 298 K. Barriers to the rearrangement of 7.7 ± 1.5 and 8.4 ± 1.5 kcal/mole are estimated for CH3C(O)OCH(O,)CH3 and HC(O)OCH(O,)CH3, respectively, leading to increased occurrence of the O2 reaction at reduced temperature. The data are combined with those obtained from similar studies of other simple esters to provide a correlation between the rate of occurrence of the ,-ester rearrangement and the structure of the reacting radical. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 397,413, 2010 [source] Thermodynamic analysis of two-step solar water splitting with mixed iron oxidesINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 10 2009Martin Roeb Abstract A two-step thermochemical cycle for solar production of hydrogen from water has been developed and investigated. It is based on metal oxide redox pair systems, which can split water molecules by abstracting oxygen atoms and reversibly incorporating them into their lattice. After successful experimental demonstration of several cycles of alternating hydrogen and oxygen production, the present work describes a thermodynamic study aiming at the improvement of process conditions and at the evaluation of the theoretical potential of the process. In order to evaluate the maximum hydrogen production potential of a coating material, theoretical considerations based on thermodynamic laws and properties are useful and faster than actual tests. Through thermodynamic calculations it is possible to predict the theoretical maximum output of H2 from a specific redox-material under certain conditions. Calculations were focussed on the two mixed iron oxides nickel,iron-oxide and zinc,iron-oxide. In the simulation the amount of oxygen in the redox-material is calculated before and after the water-splitting step on the basis of laws of thermodynamics and available material properties for the chosen mixed iron oxides. For the simulation the commercial Software FactSage and available databases for the required material properties were used. The analysis showed that a maximum hydrogen yield is achieved if the reduction temperature is raised to the limits of the operation range, if the temperature for the water splitting is lowered below 800°C and if the partial pressure of oxygen during reduction is decreased to the lower limits of the operational range. The predicted effects of reduction temperature and partial pressure of oxygen could be confirmed in experimental studies. The increased hydrogen yield at lower splitting temperatures of about 800°C could not be confirmed in experimental results, where a higher splitting temperature led to a higher hydrogen yield. As a consequence it can be stated that kinetics must play an important role especially in the splitting step. Copyright © 2009 John Wiley & Sons, Ltd. [source] Oxidative degradation of 4-nitrophenol in UV-illuminated titania suspensionJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 8 2001Jimmy Lea Abstract An internally-irradiated annular photoreactor has been used to investigate the oxidative degradation of aqueous 4-nitrophenol with titania as the photocatalyst. Reaction runs were performed over a 3-h period and in practically all cases, complete degradation was possible within about 2,h. The kinetics was determined as a function of nitrophenol concentration, oxygen partial pressure, catalyst loading, pH, temperature and light intensity. The reaction was characterised by a relatively low activation energy of 7.83,kJ,mol,1 although transport intrusions were negligible. Rate decreased almost exponentially with pH while a quadratic (maximum) behaviour with respect to both oxygen pressure and nitrophenol concentration is symptomatic of self-inhibition possibly due to the formation of intermediates which competitively adsorb on similar sites to the reactants. Increased catalyst dosage also improved the reaction rate although the possible effects of light scattering and solution opacity caused a drop at loadings higher than about 1.20,g,dm,3. Rate, however, has a linear dependency on light intensity, suggesting that hole,electron recombination processes were negligible at the conditions investigated. © 2001 Society of Chemical Industry [source] Catalytic wet air oxidation of phenol using active carbon: performance of discontinuous and continuous reactorsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 7 2001Frank Stüber Abstract Catalytic wet air oxidation (CWAO) of an aqueous phenol solution using active carbon (AC) as catalytic material was compared for a slurry and trickle bed reactor. Semi-batchwise experiments were carried out in a slurry reactor in the absence of external and internal mass transfer. Trickle-bed runs were conducted under the same conditions of temperature and pressure. Experimental results from the slurry reactor study showed that the phenol removal rate significantly increased with temperature and phenol concentration, whereas partial oxygen pressure had little effect. Thus, at conditions of 160,°C and 0.71,MPa of oxygen partial pressure, almost complete phenol elimination was achieved within 2,h for an initial phenol concentration of 2.5,g,dm,3. Under the same conditions of temperature and pressure, the slurry reactor performed at much higher initial rates with respect to phenol removal than the trickle bed reactor, both for a fresh active carbon and an aged active carbon, previously used for 50,h in the trickle bed reactor, but mineralisation was found to be much lower in the slurry reactor. Mass transfer limitations, ineffective catalyst wetting or preferential flow in the trickle bed alone cannot explain the drastic difference in the phenol removal rate. It is likely that the slurry system also greatly favours the formation of condensation polymers followed by their irreversible adsorption onto the AC surface, thereby progressively preventing the phenol molecules to be oxidised. Thus, the application of this type of reactor in CWAO has to be seriously questioned when aiming at complete mineralisation of phenol. Furthermore, any kinetic study of phenol oxidation conducted in a batch slurry reactor may not be useful for the design and scale-up of a continuous trickle bed reactor. © 2001 Society of Chemical Industry [source] The potential role of plant oxygen and sulphide dynamics in die-off events of the tropical seagrass, Thalassia testudinumJOURNAL OF ECOLOGY, Issue 1 2005J. BORUM Summary 1Oxygen and sulphide dynamics were examined, using microelectrode techniques, in meristems and rhizomes of the seagrass Thalassia testudinum at three different sites in Florida Bay, and in the laboratory, to evaluate the potential role of internal oxygen variability and sulphide invasion in episodes of sudden die-off. The sites differed with respect to shoot density and sediment composition, with an active die-off occurring at only one of the sites. 2Meristematic oxygen content followed similar diel patterns at all sites with high oxygen content during the day and hyposaturation relative to the water column during the night. Minimum meristematic oxygen content was recorded around sunrise and varied among sites, with values close to zero at the die-off site. 3Gaseous sulphide was detected within the sediment at all sites but at different concentrations among sites and within the die-off site. Spontaneous invasion of sulphide into Thalassia rhizomes was recorded at low internal oxygen partial pressure during darkness at the die-off site. 4A laboratory experiment showed that the internal oxygen dynamics depended on light availability, and hence plant photosynthesis, and on the oxygen content of the water column controlling passive oxygen diffusion from water column to leaves and below-ground tissues in the dark. 5Sulphide invasion only occurred at low internal oxygen content, and the rate of invasion was highly dependent on the oxygen supply to roots and rhizomes. Sulphide was slowly depleted from the tissues when high oxygen partial pressures were re-established through leaf photosynthesis. Coexistence of sulphide and oxygen in the tissues and the slow rate of sulphide depletion suggest that sulphide reoxidation is not biologically mediated within the tissues of Thalassia. 6Our results support the hypothesis that internal oxygen stress, caused by low water column oxygen content or poor plant performance governed by other environmental factors, allows invasion of sulphide and that the internal plant oxygen and sulphide dynamics potentially are key factors in the episodes of sudden die-off in beds of Thalassia testudinum. Root anoxia followed by sulphide invasion may be a more general mechanism determining the growth and survival of other rooted plants in sulphate-rich aquatic environments. [source] | ||||||||||||||||||||||||||||||||||||||||