Boundary-layer analysis of subsonic inlet diffuser geometries for engines nacelles

Theoretical Mach number distributions and boundary-layer parameters are presented for subsonic nacelle inlet diffuser geometries with length to exit diameter ratios ranging from 0.4 to 1.6 and diffuser exit area to throat area ratios ranging from 1.1 to 2.0. The major portion of the study was done with a cubic diffuser contour with the inflection point at the midpoint of the diffuser, a diffuser throat Mach number of 0.6, and a free-stream Mach number of 0.12. Calculations were performed at both model (diffuser exit diameter, 30.5 cm) and full-scale (diffuser exit diameter, 183 cm) sizes. Separation limits were defined by establishing a separation boundary on plots of diffuser area ratio as a function of diffuser length to diameter ratio. The effects of diffuser contour, inlet lip geometry, and throat Mach number on the boundary-layer characteristics are illustrated. The major results of the study indicate that the separation boundary is shifted to greater area ratios by (1) increasing the diffuser length, (2) increasing the scale of the diffuser and, (3) moving the inflection point of the diffuser contour to or ahead of the midpoint of the diffuser

Comparison of experimental and theoretical boundary-layer separation for inlets at incidence angle at low-speed conditions

Comparisons between experimental and theoretical Mach number distributions and separation locations are presented for the internal surfaces of four different subsonic inlet geometries with exit diameters of 13.97 centimeters. The free stream Mach number was held constant at 0.127, the one-dimensional throat Mach number ranged from 0.49 to 0.71, and the incidence angle ranged from 0 deg to 50 deg. Generally good agreement was found between the theoretical and experimental surface Mach number distributions as long as no flow separation existed. At high incidence angles, where separation was obvious in the experimental data, the theory predicted separation on the lip. At lower incidence angles, the theoretical results indicated diffuser separation which was not obvious from the experimental surface Mach number distributions. As incidence angle was varied from 0 deg to 50 deg, the predicted separation location shifted from the diffuser region to the inlet highlight. Relatively small total pressure losses were obtained when the predicted separation location was greater than 0.6 of the distance between the highlight and the diffuser exit

The Effects of Theophylline and 8-Cyclopentyltheophylline on the Respiratory Response to Carbon Dioxide in Neonatal Rats

Premature infants are often plagued with respiration problems ranging from periodic breathing to apnea. These respiratory complications can be a result of underdeveloped respiratory organs, immaturity of the brainstem respiratory control center, genetic irregularities, or a combination of all three. This study sought to increase respiration with the administration of methylxanthines, which are respiratory stimulants, coupled with carbon dioxide (CO2), also a respiratory stimulant. Neonatal rats aged 4 to 7 days old were used to mimic premature infants\u27 response to the interaction of methylxanthines and CO2. Before beginning the respiratory studies, sections of a 4- and 7-day-old rat brainstem were examined to compare the differences in development. The 4-day-old rat brain had large folds (folia), while the 7-day-old rat brain lost those folds and was much denser in neuroglial and nerve cells. These differences show that as the rat matures, the brain also matures because the folds disappear, meaning that the brain is growing and new cells are synthesized as a part of this growth. After establishing this difference in brain development between the youngest and oldest rats, various doses of two different methylxanthines, theophylline (THEO) and 8-cyclopentyltheophylline (CPT), were injected into neonatal rats and paired with CO2 percentages ranging from 1 to 6%. The interaction of the drug and CO2 was observed over a 45-minute period. Each rat was placed into a body plethysmograph that was connected by plastic tubing to a pneumotachograph to measure the rat\u27s respiration. A control period of normal breathing for 5 minutes followed in order to establish a baseline respiration, which was followed by a CO2 -response test involving exposure to increasing percentages of CO2 from 1 to 6%, delivered at 2-minute intervals. This same procedure was repeated in 15-minute intervals until the 45-minute period concluded. CO2 exposure produced a consistent increase in minute ventilation, tidal volume, and mean inspiratory flow, but not in respiratory rate, all of which were independent of the drug response. Although there was not an overall significant difference between doses of THEO, the highest dose, 40mg/kg, showed significant increases in minute ventilation, tidal volume, and mean inspiratory flow when paired with 5-6% CO2. The dose of 10 mg/kg of THEO also showed increases in minute ventilation and tidal volume at higher CO2 percentages. In contrast, CPT showed no significant increases in respiration at any dose. Interestingly, THEO doses were significant though CPT is the more potent form of the drug and has a higher affinity for adenosine A1 receptors. In summary, CO2 alone produced increases in minute ventilation, tidal volume, and mean inspiratory flow, and when paired with a dose of 40 mg/kg of THEO, these parameters increased further, showing that the highest doses of THEO paired with the highest doses of CO2 produce a significant increase in respiration

Microcephaly

Microcephaly is a noncommunicable condition causing the head of an infant to be smaller than what is typical. Microcephaly can cause delays in developmental milestones and/or can cause other conditions such as epilepsy, cerebral palsy, learning disabilities, hearing loss and vision problems. Microcephaly is found more frequently in certain populations of the world than others, specifically those with an increased number of cases with Zika virus. Women need to take preventative measures to ensure their unborn child is safe from the Zika virus. The Zika virus is not the only way microcephaly can occur. Many other causes like exposure to alcohol and drugs during pregnancy and genetic defects are also variables

The Effects of Theophylline and 8-Cyclopentyltheophylline on the Respiratory Response to Carbon Dioxide in Neonatal Rats

Premature infants are often plagued with respiration problems ranging from periodic breathing to apnea. These respiratory complications can be a result of underdeveloped respiratory organs, immaturity of the brainstem respiratory control center, genetic irregularities, or a combination of all three. This study sought to increase respiration with the administration of methylxanthines, which are respiratory stimulants, coupled with carbon dioxide (CO2), also a respiratory stimulant. Neonatal rats aged 4 to 7 days old were used to mimic premature infants\u27 response to the interaction of methylxanthines and CO2. Before beginning the respiratory studies, sections of a 4- and 7-day-old rat brainstem were examined to compare the differences in development. The 4-day-old rat brain had large folds (folia), while the 7-day-old rat brain lost those folds and was much denser in neuroglial and nerve cells. These differences show that as the rat matures, the brain also matures because the folds disappear, meaning that the brain is growing and new cells are synthesized as a part of this growth. After establishing this difference in brain development between the youngest and oldest rats, various doses of two different methylxanthines, theophylline (THEO) and 8-cyclopentyltheophylline (CPT), were injected into neonatal rats and paired with CO2 percentages ranging from 1 to 6%. The interaction of the drug and CO2 was observed over a 45-minute period. Each rat was placed into a body plethysmograph that was connected by plastic tubing to a pneumotachograph to measure the rat\u27s respiration. A control period of normal breathing for 5 minutes followed in order to establish a baseline respiration, which was followed by a CO2 -response test involving exposure to increasing percentages of CO2 from 1 to 6%, delivered at 2-minute intervals. This same procedure was repeated in 15-minute intervals until the 45-minute period concluded. CO2 exposure produced a consistent increase in minute ventilation, tidal volume, and mean inspiratory flow, but not in respiratory rate, all of which were independent of the drug response. Although there was not an overall significant difference between doses of THEO, the highest dose, 40mg/kg, showed significant increases in minute ventilation, tidal volume, and mean inspiratory flow when paired with 5-6% CO2. The dose of 10 mg/kg of THEO also showed increases in minute ventilation and tidal volume at higher CO2 percentages. In contrast, CPT showed no significant increases in respiration at any dose. Interestingly, THEO doses were significant though CPT is the more potent form of the drug and has a higher affinity for adenosine A1 receptors. In summary, CO2 alone produced increases in minute ventilation, tidal volume, and mean inspiratory flow, and when paired with a dose of 40 mg/kg of THEO, these parameters increased further, showing that the highest doses of THEO paired with the highest doses of CO2 produce a significant increase in respiration

The Effects of Theophylline and 8-Cyclopentyltheophylline on the Respiratory Response to Carbon Dioxide in Neonatal Rats

Premature infants are often plagued with respiration problems ranging from periodic breathing to apnea. These respiratory complications can be a result of underdeveloped respiratory organs, immaturity of the brainstem respiratory control center, genetic irregularities, or a combination of all three. This study sought to increase respiration with the administration of methylxanthines, which are respiratory stimulants, coupled with carbon dioxide (CO2), also a respiratory stimulant. Neonatal rats aged 4 to 7 days old were used to mimic premature infants\u27 response to the interaction of methylxanthines and CO2. Before beginning the respiratory studies, sections of a 4- and 7-day-old rat brainstem were examined to compare the differences in development. The 4-day-old rat brain had large folds (folia), while the 7-day-old rat brain lost those folds and was much denser in neuroglial and nerve cells. These differences show that as the rat matures, the brain also matures because the folds disappear, meaning that the brain is growing and new cells are synthesized as a part of this growth. After establishing this difference in brain development between the youngest and oldest rats, various doses of two different methylxanthines, theophylline (THEO) and 8-cyclopentyltheophylline (CPT), were injected into neonatal rats and paired with CO2 percentages ranging from 1 to 6%. The interaction of the drug and CO2 was observed over a 45-minute period. Each rat was placed into a body plethysmograph that was connected by plastic tubing to a pneumotachograph to measure the rat\u27s respiration. A control period of normal breathing for 5 minutes followed in order to establish a baseline respiration, which was followed by a CO2 -response test involving exposure to increasing percentages of CO2 from 1 to 6%, delivered at 2-minute intervals. This same procedure was repeated in 15-minute intervals until the 45-minute period concluded. CO2 exposure produced a consistent increase in minute ventilation, tidal volume, and mean inspiratory flow, but not in respiratory rate, all of which were independent of the drug response. Although there was not an overall significant difference between doses of THEO, the highest dose, 40mg/kg, showed significant increases in minute ventilation, tidal volume, and mean inspiratory flow when paired with 5-6% CO2. The dose of 10 mg/kg of THEO also showed increases in minute ventilation and tidal volume at higher CO2 percentages. In contrast, CPT showed no significant increases in respiration at any dose. Interestingly, THEO doses were significant though CPT is the more potent form of the drug and has a higher affinity for adenosine A1 receptors. In summary, CO2 alone produced increases in minute ventilation, tidal volume, and mean inspiratory flow, and when paired with a dose of 40 mg/kg of THEO, these parameters increased further, showing that the highest doses of THEO paired with the highest doses of CO2 produce a significant increase in respiration