The Experts below are selected from a list of 291 Experts worldwide ranked by ideXlab platform
M Herman - One of the best experts on this subject based on the ideXlab platform.
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Relationship between the Gas Composition of the middle ear and the venous blood at steady state.
The Laryngoscope, 1995Co-Authors: M Luntz, D Levi, J Sadé, M HermanAbstract:Concomitant continuous measurements of the steady-state Gas Composition of the middle ear and of the venous blood were recorded by mass spectrometry in four guinea pigs. The following mean values were obtained for the partial pressures of middle ear Gases; nitrogen + argon, 606.4 mm Hg; oxygen, 46.2 mm Hg; and carbon dioxide, 60.2 mm Hg. The corresponding values for the venous blood were as follows: Nitrogen + argon, 563.4 mm Hg; oxygen, 38.0 mm Hg; and carbon dioxide, 61.4 mm Hg. The similarity of the steady-state Gas Composition of the middle ear to that of the venous blood suggests that the partial pressures of the Gases in the middle ear are controlled by interchange with Gases present in the blood.
M Luntz - One of the best experts on this subject based on the ideXlab platform.
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Relationship between the Gas Composition of the middle ear and the venous blood at steady state.
The Laryngoscope, 1995Co-Authors: M Luntz, D Levi, J Sadé, M HermanAbstract:Concomitant continuous measurements of the steady-state Gas Composition of the middle ear and of the venous blood were recorded by mass spectrometry in four guinea pigs. The following mean values were obtained for the partial pressures of middle ear Gases; nitrogen + argon, 606.4 mm Hg; oxygen, 46.2 mm Hg; and carbon dioxide, 60.2 mm Hg. The corresponding values for the venous blood were as follows: Nitrogen + argon, 563.4 mm Hg; oxygen, 38.0 mm Hg; and carbon dioxide, 61.4 mm Hg. The similarity of the steady-state Gas Composition of the middle ear to that of the venous blood suggests that the partial pressures of the Gases in the middle ear are controlled by interchange with Gases present in the blood.
Jacob Sadé - One of the best experts on this subject based on the ideXlab platform.
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Dependence of Middle Ear Gas Composition on Pulmonary Ventilation
The Annals of otology rhinology and laryngology, 1997Co-Authors: Haya Mover-lev, Moshe Harell, Dalia Levy, Michal Luntz, Jacob SadéAbstract:The middle ear (ME) steady state Gas Composition resembles that of mixed venous blood. We changed arterial and venous blood Gases by artificially ventilating anesthetized guinea pigs and measured simultaneous ME Gas changes during spontaneous breathing, hyperventilation, and hypoventilation. During hyperventilation, PaCO2 and PvCO2 (a = arterial, v = venous) decreased from 46.0 and 53.0 mm Hg to 17.9 and 37.5 mmHg, respectively, while PaO2 and PvO2 (85.6 and 38.2 mm Hg) did not change. This was accompanied by an ME PCO2 decrease from 70.4 to 58.8 mm Hg and a PO2 decrease from 36.8 to 25.4 mm Hg. During hypoventilation, PaCO2 and PvCO2 increased to 56.8 and 66.4 mm Hg, while PvO2 decreased to 21.8 mm Hg. The ME PCO2 increased simultaneously to 88.8 mm Hg and the ME PO2 decreased to 25.4 mm Hg. The ME PO2 decrease during hyperventilation may be explained by a 33% decrease in ME mucosa perfusion, calculated from the ME ventilation-perfusion ratio. This study shows that ME Gas Composition follows fluctuations of blood Gas levels and thus mav affect total ME pressure.
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Gas Composition of the Human Nose and Nasopharyngeal Space
Acta oto-laryngologica, 1996Co-Authors: Moshe Harell, Haya Mover-lev, Dalia Levy, Jacob SadéAbstract:Since it was established that middle ear (ME) Gas Composition is closer to venous Gas Composition than to air, the question arose regarding the Composition of Gas which enters the ME from the nasopharynx. Using a mass spectrometer, Gaseous partial pressure was measured at three locations in the nose and nasopharynx of 6 volunteers. All three locations showed similar Gas Composition (O2 = 15.7%, CO2 = 4.5%, N2 + Ar = 79.8%) which is similar to expired air. The Gas that enters the ME via the Eustachian tube is a mixture closer to the final ME Gas equilibrium than is air. This minimizes the changes in steady state ME Gas Composition incurred by Gas influx into the ME.
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Dynamic measurement of Gas Composition in the middle ear. II: Steady state values.
Acta oto-laryngologica, 1993Co-Authors: Jacob Sadé, Michal LuntzAbstract:On-line measurement of ME Gas Composition in normal middle ears of 5 anesthetized guinea pigs at an established steady state was performed by mass spectrometry. The mean values for the Gas Composition of the middle ear were found to be: PN2: 82.4%, PO2: 7.6% and PCO2: 10.0%. This Composition is very different from that of atmospheric air, and very similar to the Gas Composition of mixed venous blood. Our conclusions are that the Gas Composition is basically controlled by interchange with Gases present in the blood and not by introduction of air through the eustachian tube. It is therefore proposed that middle ear Gas deficiency is secondary not to eustachian tube input failure but to excess loss of middle ear Gas due to enhanced diffusion into the blood. This situation exists especially under inflammatory conditions when there is an enlarged number of blood vessels promoting increased Gas diffusion into them. Under ordinary conditions this middle ear Gas deficiency will probably cause no significant underpressure because the mastoid pneumatization will act as a pressure buffer. When mastoid pneumatization is lacking, as happens in the otitis media syndrome, a pathological negative pressure will ensue.
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Dynamic Measurement of Gas Composition in the Middle Ear I: Technique
Acta oto-laryngologica, 1993Co-Authors: Michal Luntz, Jacob SadéAbstract:The middle ear is a balanced Gas pocket which loses and gains Gas constantly. This balance depends on the continuous interchange of Gases from the atmosphere, through the eustachian tube and the circulating blood by diffusion. The relative contribution of each of these two sources can be determined by measuring the Gas Composition of the middle ear (ME). Because of the small quantity of Gas in the ME, adequate sampling and accurate measurement of its Composition are extremely difficult. An on-line system for middle ear Gas Composition measurements is described. The measuring instrument is mass spectrometer. ME Gas samples are withdrawn by diffusion, and therefore are very small. Sampling and measurements are performed in a continuous mode.
Mohsen Sheikhi - One of the best experts on this subject based on the ideXlab platform.
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Study of the effect of shielding Gas Composition on the mechanical weld properties of steel ST 37-2 in Gas metal arc welding
Materials & Design, 2009Co-Authors: Mohamad Ebrahimnia, M. Goodarzi, Meisam Nouri, Mohsen SheikhiAbstract:In this study, the influence of variation in the shielding Gas Composition on the weld properties of the steel ST 37-2 was investigated. The influence of four different shielding Gas Compositions was studied in this work. After accomplishing some mechanical and metallographic tests, it was found that the absorbed energy in the Charpy impact test first increases then remains constant with increase of the amount of carbon dioxide in the shielding Gas Composition. The amount of inclusions decreases and the Widmanstatten ferrite volume fraction increases with increase of the carbon dioxide percent in shielding Gas. On the other hand, the depth of the fusion zone in GMAW increases with increase of the carbon dioxide in shielding Gas.
Joseph P. Kerry - One of the best experts on this subject based on the ideXlab platform.
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Mathematical modeling of the influence of temperature and Gas Composition on the respiration rate of shredded carrots
Journal of Food Engineering, 2009Co-Authors: Tariq Iqbal, Fernanda A.s. Rodrigues, Pramod V. Mahajan, Joseph P. KerryAbstract:Abstract Measurement of the respiration rate of fresh produce under different Gas Composition and temperature, and respective mathematical modeling, are essential for the design of modified atmosphere packaging (MAP). In this work respiration rate of shredded carrots was measured at storage temperatures of 0, 4, 8, 12, 16 and 20 °C under different Gas Composition of O2 and CO2. As expected, temperature was the most influential factor on respiration rate, for all atmospheres tested; as it increased from 0 to 20 °C the values varied from 5.2 ± 0.5 to 51 ± 1 ml/(kg hr) for ambient air. The extreme Gas mix (2% O2 + 16% CO2) reduced O2 consumption and CO2 production rates by 30–45%, when compared to the values observed for the samples stored in ambient air. Primary modelling showed that the effect of temperature followed an Arrhenius-type relationship and that the influence Gas Composition was best described by a Michaelis–Menten uncompetitive model. It was further observed that activation energy for both O2 and CO2, was not statistically different in the range of Gas Composition tested, thus RQ was considered to be constant (1.2). Monte Carlo simulations using respiration rate model parameters showed that the levels of O2 and CO2 in MAP containing shredded carrots were within the tolerance limits.
