Heat pipes for wing leading edges of hypersonic vehicles

Wing leading edge heat pipes were conceptually designed for three types of vehicle: an entry research vehicle, aero-space plane, and advanced shuttle. A full scale, internally instrumented sodium/Hastelloy X heat pipe was successfully designed and fabricated for the advanced shuttle application. The 69.4 inch long heat pipe reduces peak leading edge temperatures from 3500 F to 1800 F. It is internally instrumented with thermocouples and pressure transducers to measure sodium vapor qualities. Large thermal gradients and consequently large thermal stresses, which have the potential of limiting heat pipe life, were predicted to occur during startup. A test stand and test plan were developed for subsequent testing of this heat pipe. Heat pipe manufacturing technology was advanced during this program, including the development of an innovative technique for wick installation

Electron-lattice relaxation, and soliton structures and their interactions in polyenes

Density matrix renormalisation group calculations of a suitably parametrised model of long polyenes (polyacetylene oligomers), which incorporates both long range Coulomb interactions and adiabatic lattice relaxation, are presented. The triplet and 2Ag states are found to have a 2-soliton and 4-soliton form, respectively, both with large relaxation energies. The 1Bu state forms an exciton-polaron and has a very small relaxation energy. The relaxed energy of the 2Ag state lies below that of the 1Bu state. The soliton/anti-soliton pairs are bound.Comment: RevTeX, 5 pages, 4 eps figures included using epsf. To appear in Physical Review Letters. Fig. 1 fixed u

Particulate PAH Emissions from Residential Biomass Combustion: Time-Resolved Analysis with Aerosol Mass Spectrometry

Time-resolved emissions of particulate polycyclic aromatic hydrocarbons (PAHs) and total organic particulate matter (OA) from a wood log stove and an adjusted pellet stove were investigated with high-resolution time-of-flight aerosol mass spectrometry (ANIS). The highest OA emissions were found during the addition of log wood on glowing embers, that is, slow burning pyrolysis conditions. These emissions contained about 1% PAHs (of OA). The highest PAH emissions were found during fast burning under hot air starved combustion conditions, in both stoves. In the latter case, PAHs contributed up to 40% of OA, likely due to thermal degradation of other condensable species. The distribution of PAHs was also shifted toward larger molecules in these emissions. ANIS signals attributed to PAHs were found at molecular weights up to 600 Da. The vacuum aerodynamic size distribution was found to be bimodal with a smaller mode (D-va similar to 200 nm) dominating under hot air starved combustion and a larger sized mode dominating under slow burning pyrolysis (D-va similar to 600 nm). Simultaneous reduction of PAHs, OA and total particulate matter from residential biomass combustion may prove to be a challenge for environmental legislation efforts as these classes of emissions are elevated at different combustion conditions

Direction of Arrival and the Rank-Revealing URV Decomposition

In many practical direction-of-arrival (DOA) problems the number of sources and their directions from an antenna array do not remain stationary. Hence a practical DOA algorithm must be able to track changes with a minimal number of snapshots. In this paper we describe DOA algorithms, based on a new decomposition, that are not expensive to compute or difficult to update. The algorithms are compared with algorithms based on the singular value decomposition (SVD). (Also cross-referenced as UMIACS-TR-91-166

Increased prevalence of sleep disturbances and daytime sleepiness in subjects with bronchial asthma: a population study of young adults in three European countries

To access publisher full text version of this article. Please click on the hyperlink in Additional Links fieldThe aim of this study was to investigate whether asthma is associated with decreased quality of sleep and increased daytime sleepiness. The study involved a random population of 2,202 subjects supplemented by 459 subjects with suspected asthma, aged 20-45 yrs. The subjects were from Reykjavik (Iceland), Uppsala and Göteborg (Sweden) and Antwerp (Belgium), and participated in the European Community Respiratory Health Survey. The investigation included a structured interview, methacholine challenge, skinprick tests and a questionnaire on sleep disturbances. Participants in Iceland and Sweden also estimated their sleep times and made peak expiratory flow (PEF) recordings during a period of 1 week. Asthma was defined as self-reported physician-diagnosed asthma with current asthma-related symptoms (n = 267). Difficulties inducing sleep (DIS) and early morning awakenings (EMA) were about twice as common, and daytime sleepiness 50% more common, in asthmatics compared with subjects without asthma. After adjusting for possible confounders, a positive association was found between asthma and: DIS (odds ratio (OR) = 1.8); EMA (OR = 2.0); daytime sleepiness (OR = 1.6); snoring (OR = 1.7); and self reported apnoeas (OR = 3.7). Allergic rhinitis, which was reported by 71% of subjects with asthma, was independently related to DIS (OR = 2.0) and daytime sleepiness (OR = 1.3). A significant correlation was found between the number of asthma-related symptoms and sleep disturbances (p < 0.001). Asthma is associated with decreased subjective quality of sleep and increased daytime sleepiness. Concurrent allergic rhinitis may be an important underlying cause of sleep impairment in asthmatic patients

The size of electron-hole pairs in pi conjugated systems

We have performed momentum dependent electron energy-loss studies of the electronic excitations in sexithiophene and compared the results to those from parent oligomers. Our experiment probes the dynamic structure factor S(q,omega)and we show that the momentum dependent intensity variation of the excitations observed can be used to extract the size of the electron-hole pair created in the excitation process. The extension of the electron-hole pairs along the molecules is comparable to the length of the molecules and thus maybe only limited by structural constraints. Consequently, the primary intramolecular electron-hole pairs are relatively weakly bound. We find no evidence for the formation of excitations localized on single thiophene units.Comment: RevTex, 3 figures, to appear in Physical Review Letter

Developing and Selecting Auditory Warnings for a Real-Time Behavioral Intervention

Real-time sensing and computing technologies are increasingly used in the delivery of real-time health behavior interventions. Auditory signals play a critical role in many of these interventions, impacting not only behavioral response but also treatment adherence and participant retention. Yet, few behavioral interventions that employ auditory feedback report the characteristics of sounds used and even fewer design signals specifically for their intervention. This paper describes a four-step process used in developing and selecting auditory warnings for a behavioral trial designed to reduce indoor secondhand smoke exposure. In step one, relevant information was gathered from ergonomic and behavioral science literature to assist a panel of research assistants in developing criteria for intervention-specific auditory feedback. In step two, multiple sounds were identified through internet searches and modified in accordance with the developed criteria, and two sounds were selected that best met those criteria. In step three, a survey was conducted among 64 persons from the primary sampling frame of the larger behavioral trial to compare the relative aversiveness of sounds, determine respondents\u27 reported behavioral reactions to those signals, and assess participant’s preference between sounds. In the final step, survey results were used to select the appropriate sound for auditory warnings. Ultimately, a single-tone pulse, 500 milliseconds (ms) in length that repeats every 270 ms for three cycles was chosen for the behavioral trial. The methods described herein represent one example of steps that can be followed to develop and select auditory feedback tailored for a given behavioral intervention

The threat of Peters’s Rock Agama (Agama picticauda) to reptile diversity across the Lesser Antilles

Lette

Service evaluation of a nurse-led dental anxiety management service for adult patients

Objective: Evaluate patients’ and professionals’ experiences of a Nurse-led Dental Anxiety Management Service (NDAMS). Design: Service evaluation. Setting: The NDAMS operates as part of Sheffield Salaried Primary Dental Care Service. Subjects and methods: Questionnaire survey of anxious patients and qualitative interviews with patients and professionals Interventions: Dental nurses delivered low-level psychological interventions as part of an Integrated Care Pathway (ICP) for dental anxiety. Main outcome Measures: Dental anxiety and oral health-related quality of life (OHRQoL) questionnaires were completed by patients prior to and following NDAM. Results: A total of 187 patients were assessed as suitable for NDAM (mean age= 33.7, 77% female) and 33 had completed it at the time of the service evaluation. Of those patients who had completed the intervention significant improvements in dental anxiety and OHRQoL were reported. Professionals highlighted the importance of integrated working, adequate support and training and assessing the suitability of patients for NDAM. Conclusion: ICPs that combine pharmacological and psychological management approaches can help meet the needs of dentally anxious patients, however, early identification of patients most likely to benefit from psychological intervention should be a priority