Analysis of the altitude tracking performance of aircraft-autopilot systems in the presence of atmospheric disturbances

Cover titleJanuary 1988Also issued as an M.S. thesis, Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1988Includes bibliographical references (p. 99)The dynamic response of aircraft-autopilot systems to atmospheric disturbances was investigated by analyzing linearized models of aircraft dynamics and altitude hold autopilots. Four jet aircraft (Boeing 737-100, McDonald Douglas DC9-30, Lockheed L-10ll, and Cessna Citation III) were studied at three flight levels (FL290, FL330, and FL370). The models were analyzed to determine the extent to which pressure surface fluctuations, vertical gusts, and horizontal gusts cause assigned altitude deviations by coupling with the aircraft-autopilot dynamics. The results of this analysis were examined in light of meteorological data on disturbance magnitudes and wavelengths collected from observations of mountain wave activity. This examination revealed that atmospheric conditions do exist which can cause aircraft to exhibit assigned altitude deviations in excess of 1,000 ft. Pressure surface fluctuations were observed to be the dominant source of altitude errors in flights through extreme mountain wave activity. Based on the linear analysis the maximum tolerable pressure surface fluctuation amplitude was determined as a function of wavelength for an allowable altitude error margin of 300 ft. The results of this analysis provide guidance for the determination of vertical separation standards in the presence of atmospheric disturbances

Storage Time and Temperature on the Sensory Properties Broccoli

Typically, broccoli arrives at the store within 7–14 days of harvest and is kept refrigerated until purchased or considered waste. To date, information has been limited on how this time on the shelf or storage temperature affects the sensory attributes that contribute to broccoli purchase or repurchase. In this study, 100 consumers performed acceptance tests and a check-all-that-apply (CATA) section to characterize sensory changes in two cultivars of broccoli (‘Diplomat’ and ‘Emerald Crown’) stored at two temperatures (0 °C and 4 °C) over five time points: 0, 14, 21, 28, and 42 days. Due to quality degradation during storage, the overall liking of broccoli decreased regardless of holding temperature and variety. This was in accordance with a decrease in sweetness and an increase in bitterness intensity. However, there were differences between varieties in which Diplomat had more sensory changes at higher temperatures and only Emerald showed negative changes to its appearance in color. Lastly, the CATA data revealed the attributes responsible for modulating the consumer acceptance of broccoli such as tastes, colors and flavors (e.g., grassy, musty, dirt-like). This information can be used to better inform shelf-life determinations of broccoli. Additionally, these changes in taste, odor, texture, and color can inform those interested in investigating the biochemical processes related to broccoli storage

Effect of Enzymatic Treatments on the Physiochemical Properties of Different Corn Starches

Amylose readily reassociates to form films and crystalline structures that are resistant to digestion by amylolytic enzymes and known as resistant starch type III (RS3). This study investigated the RS3 formation and cereal coating properties from enzyme-modified corn starches with varying amylose contents, including Hylon VII (70% amylose), Hylon V (50% amylose), and common corn (25% amylose). For RS3 formation, corn starches were first gelatinized and then hydrolyzed using β-amylase to varying degrees. The resultant hydrolyzed starch was debranched with isoamylase and then exposed to 3 times of temperature cycling at 135/133/133°C for 30 min and 95°C for 24 hr to promote RS3 formation. For cereal coating applications, corn starches were gelatinized and debranched, and then sprayed onto ready-to-eat breakfast cereal flakes. The proportions of amylose and amylopectin long and short chains were affected by the β-amylase treatment and varied with starch type. All three corn starches had increased RS contents after moderate β-amylolysis with Hylon V having the highest RS content at 70.7% after 4 hr of β-amylolysis. The RS content was positively correlated with amylose and amylopectin long chains, but negatively correlated with amylopectin short chains. A starch film of 50-130 μm was observed with scanning electron microscopy on the surface of the cereals coated with Hylon VII. After soaking in milk for 3 min, the peak force of the cereals coated with corn starches were higher than those of the controls. The cereals coated with Hylon VII were found to have an increase in dietary fiber content. The results suggest that RS3 formation is affected by starch composition as well as starch structure and can be increased by moderate β-amylolysis. Debranched amylose-containing corn starches could be used as cereal coatings to extend the bowl-life of ready-to-eat cereals

The Influences of Texture and Mastication Pattern on Flavor Perception Across the Lifespan

Texture is an often-overlooked food attribute and is known to influence other food characteristics. More specifically, texture has been repeatedly to influence how we perceive flavor. Several studies have linked this change in flavor perception to the altered mastication patterns that accompany texture changes. This dissertation is composed of four studies that were designed to address how American food consumers view texture and other food attributes as well as characterize how texture and mastication can influence temporal flavor dynamics. The first study was a survey that outlined consumer attitudes towards a variety of different foods. This study solidified that texture is indeed one of, if not the most important food attribute. Also, it was found that texture importance changes as consumers age. The second study started the exploration of how texture can influence flavor perception. Potato chips of different textures were given to participants and they were asked to rate their flavor perception over time. During the consumption of these chips the mastication of the participants was also recorded using electromyography. It was found that the temporal flavor dynamics were indeed different based upon the texture. Older adults don’t show the same influence of texture as displayed by younger adults. The number of chews was instrumental in helping to understand how texture influences flavor. Moving forward, the third and fourth experiments were fashioned to confirm that mastication was indeed a factor in flavor perception. The chewing rate and chewing duration was found to directly influence temporal flavor perception, as measured by Time-intensity methodology. Additionally, it was found that the effect of mastication on Temporal Dominance of Sensations was minimal, when compared to Time-intensity. This study characterizes how texture is viewed by the American food consumer and gives valuable information on the mechanisms behind texture’s influence of flavor perception. Additionally, specific mastication parameters were identified as being integral in changes in temporal flavor dynamics

Storage Time and Temperature on the Sensory Properties Broccoli

Typically, broccoli arrives at the store within 7–14 days of harvest and is kept refrigerated until purchased or considered waste. To date, information has been limited on how this time on the shelf or storage temperature affects the sensory attributes that contribute to broccoli purchase or repurchase. In this study, 100 consumers performed acceptance tests and a check-all-that-apply (CATA) section to characterize sensory changes in two cultivars of broccoli (‘Diplomat’ and ‘Emerald Crown’) stored at two temperatures (0 °C and 4 °C) over five time points: 0, 14, 21, 28, and 42 days. Due to quality degradation during storage, the overall liking of broccoli decreased regardless of holding temperature and variety. This was in accordance with a decrease in sweetness and an increase in bitterness intensity. However, there were differences between varieties in which Diplomat had more sensory changes at higher temperatures and only Emerald showed negative changes to its appearance in color. Lastly, the CATA data revealed the attributes responsible for modulating the consumer acceptance of broccoli such as tastes, colors and flavors (e.g., grassy, musty, dirt-like). This information can be used to better inform shelf-life determinations of broccoli. Additionally, these changes in taste, odor, texture, and color can inform those interested in investigating the biochemical processes related to broccoli storage

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Translational pharmacology of an inhaled small molecule αvβ6 integrin inhibitor for idiopathic pulmonary fibrosis

The αvβ6 integrin plays a key role in the activation of transforming growth factor-β (TGFβ), a pro-fibrotic mediator that is pivotal to the development of idiopathic pulmonary fibrosis (IPF). We identified a selective small molecule αvβ6 RGD-mimetic, GSK3008348, and profiled it in a range of disease relevant pre-clinical systems. To understand the relationship between target engagement and inhibition of fibrosis, we measured pharmacodynamic and diseaserelated end points. Here we report, GSK3008348 binds to αvβ6 with high affinity in human IPF lung and reduces downstream pro-fibrotic TGFβ signaling to normal levels. In human lung epithelial cells, GSK3008348 induces rapid internalization and lysosomal degradation of the αvβ6 integrin. In the murine bleomycin-induced lung fibrosis model, GSK3008348 engages αvβ6, induces prolonged inhibition of TGFβ signaling and reduces lung collagen deposition and serum C3M, a marker of IPF disease progression. These studies highlight the potential of inhaled GSK3008348 as an anti-fibrotic therapy

Combinatorial discovery of polymers resistant to bacterial attachment

Bacterial attachment and subsequent biofilm formation are key challenges to the long term performance of many medical devices. Here, a high throughput approach coupled with the analysis of surface structure-property relationships using a chemometics approach has been developed to simultaneously investigate the interaction of bacteria with hundreds of polymeric materials on a microarray format. Using this system, a new group of materials comprising ester and hydrophobic moieties are identified that dramatically reduce the attachment of clinically relevant, pathogenic bacteria (Pseudomonas aeruginosa, Staphylococcus aureus and uropathogenic Escherichia coli). Hit materials coated on silicone catheters resulted in up to a 30 fold reduction in coverage compared to a commercial silver embedded catheter, which has been proven to half the incidence of clinically acquired infection. These polymers represent a new class of materials resistant to bacterial attachment that could not have been predicted from the current understanding of bacteria-surface interactions