The longitudinal stability of a tethered rotary-winged aircraft

A linearised mathematical representation of a tethered rctorcraft is developed in order to study the influence of various parameters on the machine’s longitudinal stability. The investigation is concerned principally with a vehicle having two side-by-side contrarotating rotors and a large tailplane. The first part of the thesis consists of a detailed development of the trim equations, and of linearised equations of longitudinal motion which are written in Earth-fixed axes. Aerodynamic derivatives are used to account for the perturbations to rotor and tailplane aerodynamic forces. Dcwnwash lag derivatives are developed using a hcrseshcevortex- plus-wake representation of the flew field of a rotor in forward flight. Because the analysis concentrates on the vehicle's dynamics, a simple quasi-static representation of the single tethering cable is adopted. This approach is adequate provided that the cable mass is a small fraction of the vehicle's mass. When the tether is straight and may be considered inelastic, the Routh-Hurwitz criteria predict that the machine can be made inherently stable in hcver by increasing the thrust tc weight ratio, provided that the cable length dees not exceed a certain small value. The tether must also be attached above the machine's centre of mass tc prevent an aperiodic "pendular" divergence. The same stability criteria show that the machine will be unstable in hcver when the tethering cable is long. When the tether is curved or elastic, simple analytic stability criteria cannot be obtained. Instead, in the second part of the thesis, the influence of various parameters on the vehicle's behaviour is examined by numerically solving particular characteristic equations. The numerical studies show that many vehicle ccnfigurations can be stable in wind, but most are unstable in hcver. The cable attachment point height remains a dominant parameter for hover flight, and in wind. Instability in hover often takes the form of a coupled pitch-translation oscillation similar to that observed in a conventional helicopter. Attaching the tether below the centre of mass can stabilise this oscillation, but results in an aperiodic divergent "pendular" mode. In wind, a tailplane of suitable size will impart asymptotic stability to the system. In strong winds a long tethering cable will be highly curved. The vehicle’s dynamic behaviour is then substantially unrelated to the cable profile. The natural modes shew little dependence on the machine’s geometry, and are strongly influenced by the horizontal tail surface

An Evening of Baroque Chamber Music

Centennial Lecture Hall April 14, 1969 8:15p.m

Nocturnal sleep, daytime sleepiness, and quality of life in stable patients on hemodialysis

BACKGROUND: Although considerable progress has been made in the treatment of chronic kidney disease, compromised quality of life continues to be a significant problem for patients receiving hemodialysis (HD). However, in spite of the high prevalence of sleep complaints and disorders in this population, the relationship between these problems and quality of life remains to be well characterized. Thus, we studied a sample of stable HD patients to explore relationships between quality of life and both subjective and objective measures of nocturnal sleep and daytime sleepiness METHODS: The sample included forty-six HD patients, 24 men and 22 women, with a mean age of 51.6 (10.8) years. Subjects underwent one night of polysomnography followed the next morning by a Multiple Sleep Latency Test (MSLT), an objective measure of daytime sleepiness. Subjects also completed: 1) a brief nocturnal sleep questionnaire; 2) the Epworth Sleepiness Scale; and, 3) the Quality of Life Index (QLI, Dialysis Version) which provides an overall QLI score and four subscale scores for Health & Functioning (H&F), Social & Economic (S&E), Psychological & Spiritual (P&S), and Family (F). (The range of scores is 0 to 30 with higher scores indicating better quality of life.) RESULTS: The mean (standard deviation; SD) of the overall QLI was 22.8 (4.0). The mean (SD) of the four subscales were as follows: H&F – 21.1 (4.7); S&E – 22.0 (4.8); P&S – 24.5 (4.4); and, F – 26.8 (3.5). H&F (r(s )= -0.326, p = 0.013) and F (r(s )= -0.248, p = 0.048) subscale scores were negatively correlated with periodic limb movement index but not other polysomnographic measures. The H&F subscale score were positively correlated with nocturnal sleep latency (r(s )= 0.248, p = 0.048) while the H&F (r(s )= 0.278, p = 0.030) and total QLI (r(s )= 0.263, p = 0.038) scores were positively associated with MSLT scores. Both of these latter findings indicate that higher life quality is associated with lower sleepiness levels. ESS scores were unrelated to overall QLI scores or the subscale scores. Subjective reports of difficulty falling asleep and waking up too early were significantly correlated with all four subscale scores and overall QLI. Feeling rested in the morning was positively associated with S&E, P&S, and Total QLI scores. CONCLUSION: Selected measures of both poor nocturnal sleep and increased daytime sleepiness are associated with decreased quality of life in HD patients, underscoring the importance of recognizing and treating these patients' sleep problems

Alginate Oligosaccharides modify hyphal infiltration of Candida albicans in an in vitro model of invasive Human Candidosis

AIMS: A novel alginate oligomer (OligoG CF-5/20) has been shown to potentiate antifungal therapy against a range of fungal pathogens. The current study assessed the effect of this oligomer on in vitro virulence factor expression and epithelial invasion by Candida species. METHODS AND RESULTS: Plate substrate assays and epithelial models were used to assess Candida albicans (CCUG 39343 and ATCC 90028) invasion, in conjunction with confocal laser scanning microscopy and histochemistry. Expression of candidal virulence factors was determined biochemically and by quantitative PCR (qPCR). Changes in surface charge of C. albicans following OligoG treatment were analysed using electrophoretic light scattering. OligoG induced marked alterations in hyphal formation in the substrate assays and reduced invasion in the epithelial model (P 0·05), qPCR demonstrated a reduction in phospholipase B (PLB2) and SAPs (SAP4 and SAP6) expression. CONCLUSION: OligoG CF-5/20 reduced in vitro virulence factor expression and invasion by C. albicans. SIGNIFICANCE AND IMPACT OF THE STUDY: These results, and the previously described potentiation of antifungal activity, define a potential therapeutic opportunity in the treatment of invasive candidal infections

Recital: David Sheaffer, Oboe; Nancy Sheaffer, Piano; Won Mo Kim, Violin; Robert Oppelt, Viola; Howard Rye, Cello; March 22, 1971

Recital Hall (CE 121)March 22, 19718:15 p.m

Faculty Artist Series: Won-Mo Kim, Violin; Harold Gray, Piano; Charles Bolen, Flute; Howard Rye, Cello; David Poultney, Harpsichord; June 21, 1972

Centennial East Recital HallWednesday EveningJune 21, 19728:15 p.m

Paradoxical Sleep Suppresses Immediate Early Gene Expression in the Rodent Suprachiasmatic Nuclei

Light stimulates neuronal activity with subsequent expression of the protein product of the immediate early gene, c-fos, in the Suprachiasmatic Nuclei (SCN). Non-photic stimuli is also thought to modulate activity within the SCN. Here, we sought to determine the effects intrinsic stimuli, specifically, the states of sleep upon c-fos protein expression in the SCN. In 16 rats, c-fos protein expression was evaluated at a fixed time of 1600 h (subjective night), following 1 h of electroencephalographically defined sleep. During sleep, as the state of paradoxical sleep (PS) increased, c-fos protein expression decreased (r = −0.41, p < 0.033). The PS-associated reduction of c-fos positive cells occurred equally between animals asleep in the light and those asleep in the dark. We propose a model whereby PS duration might function as a homeostatic-entraining mechanism to reduce neuronal activity within the SCN, and thereby modulate circadian rhythms during sleep

Montado com esteva: qual o efeito da disponibilidade de água para as árvores?

N/