Combustion of HAN-based liquid monopropellants near the thermodynamic critical point

The high-pressure combustion properties of liquid monopropellants involving mixtures of hydroxyl ammonium nitrate (HAN), triethanol ammonium nitrate (TEAN), and water are considered theoretically. Liquid surface properties and the critical combustion pressure (the pressure required for the propellant surface to exceed its thermodynamic critical point) were found allowing for real-gas phenomena and the presence of dissolved combustion product gases in the liquid. Critical combustion pressures for the HAN-based monopropellants were found to be unusually high, ca. 2500 atm, with an estimated uncertainty of 50%. Predictions were unusually sensitive to the critical temperature of TEAN and the binary interaction parameter between TEAN and water; both must be known more accurately for definitive estimates of the liquid-surface properties of HAN-based monopropellants at high pressures.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27077/1/0000068.pd

Stochastic aspects of turbulent combustion processes

Methods of using stochastic simulations to treat nonlinear interactions in turbulent combustion processes are described -- emphasizing the use of statistical time-series techniques to analyze the turbulence--radiation interactions of nonpremixed flames. Three aspects of the problem are considered, as follows: the statistics of scalar properties in turbulent flames, the formulation of algorithms to stimulate flame radiation based on flame statistics, and evaluation of the methodology using recent measurements for nonluminous flames. It is shown that the process becomes tractable through the laminar flamelet approximation whereby all scalar properties are taken to be solely functions of a conserved scalar like the mixture fraction. Thus, the simulations are designed to generate realizations of mixtures fractions along radiations path with the radiation properties of each realization found using a narrow-bond radiation model. An autoregressive process that reproduces probability density functions and spatial and temporal correlations of mixture fraction was found to yield reasonably good predictions of the statistical properties of spectral radiation intensities measured for turbulent carbon monoxide and hydrogen jet flames burning in still air. Although the approach appears to be promising, additional development is needed in order to treat some of the unique statistical features of turbulence that are not encountered during conventional use of statistical time-series techniques.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29477/1/0000563.pd

Ballistic transport and boundary resistances in inhomogeneous quantum spin chains

Transport phenomena are central to physics, and transport in the many-body and fully-quantum regime is attracting an increasing amount of attention. It has been recently revealed that some quantum spin chains support ballistic transport of excitations at all energies. However, when joining two semi-infinite ballistic parts, such as the XX and XXZ spin-1/2 models, our understanding suddenly becomes less established. Employing a matrix-product-state ansatz of the wavefunction, we study the relaxation dynamics in this latter case. Here we show that it takes place inside a light cone, within which two qualitatively different regions coexist: an inner one with a strong tendency towards thermalization, and an outer one supporting ballistic transport. We comment on the possibility that even at infinite time the system supports stationary currents and displays a non-zero Kapitza boundary resistance. Our study paves the way to the analysis of the interplay between transport, integrability, and local defects

Measuring the burden of herpes zoster and post herpetic neuralgia within primary care in rural Crete, Greece

<p>Abstract</p> <p>Background</p> <p>Research has indicated that general practitioners (GPs) have good clinical judgment in regards to diagnosing and managing herpes zoster (HZ) within clinical practice in a country with limited resources for primary care and general practice. The objective of the current study was to assess the burden of HZ and post herpetic neuralgia (PHN) within rural general practices in Crete, Greece.</p> <p>Methods</p> <p>The current study took place within a rural setting in Crete, Greece during the period of November 2007 to November 2009 within the catchment area in which the Cretan Rural Practice-based Research Network is operating. In total 19 GP's from 14 health care units in rural Crete were invited to participate, covering a total turnover patient population of approximately 25, 000 subjects. For the purpose of this study an electronic record database was constructed and used as the main tool for monitoring HZ and PHN incidence. Stress related data was also collected with the use of the Short Anxiety Screening Test (SAST).</p> <p>Results</p> <p>The crude incidence rate of HZ was 1.4/1000 patients/year throughout the entire network of health centers and satellite practices, while among satellite practices alone it was calculated at 1.3/1000 patients/year. Additionally, the standardised incidence density within satellite practices was calculated at 1.6/1000 patients/year. In regards to the stress associated with HZ and PHN, the latter were found to have lower levels of anxiety, as assessed through the SAST score (17.4 ± 3.9 vs. 21.1 ± 5.7; <it>p </it>= 0.029).</p> <p>Conclusions</p> <p>The implementation of an electronic surveillance system was feasible so as to measure the burden of HZ and PHN within the rural general practice setting in Crete.</p

Endurance performance is influenced by perceptions of pain and temperature: Theory, applications and safety considerations.

Models of endurance performance now recognise input from the brain, including an athlete’s ability to cope with various non-pleasurable perceptions during exercise, such as pain and temperature. Exercise training can reduce perceptions of both pain and temperature over time, partly explaining why athletes generally have a higher pain tolerance, despite a similar pain threshold, compared with active controls. Several strategies with varying efficacy may ameliorate the perceptions of pain (e.g. acetaminophen, transcranial direct current stimulation and transcutaneous electrical stimulation) and temperature (e.g. menthol beverages, topical menthol products and other cooling strategies, especially those targeting the head) during exercise to improve athletic performance. This review describes both the theory and practical applications of these interventions in the endurance sport setting, as well as the potentially harmful health consequences of their use

Heat production and heat loss responses to cold water immersion after 35 days horizontal bed rest

Introduction: Bed rest is a terrestrial experimental analogue of unloading experienced during exposure to microgravity. Such unloading causes atrophy predominantly of the postural muscles, especially those of the lower limbs. Methods: We tested the hypothesis that 35 d horizontal bed rest alters thermoregulatory responses of subjects (N = 10) immersed in 15oC water, particularly the heat produced by the shivering tremor of the skeletal muscles. Before and after bed rest we measured the thickness of the gastrocnemius medialis (GM), vastus lateralis (VL), tibialis anterior (TA), and biceps brachii (BB) muscles by ultrasonography. During the immersions, we monitored rectal and skin temperatures, heat fl ux, heart rate, and oxygen uptake. Results: After bed rest, muscle thickness decreased signifi cantly by 12.2 \ub1 8.8% and 8.0 \ub1 9.1% in the GM and VL, respectively. No changes were observed in the TA and BB muscles. The 35-d bed rest caused a signifi cant reduction in aerobic power, as refl ected in maximal oxygen uptake. There were no signifi cant differences in any of the observed thermoregulatory responses between the pre- and post-bed rest immersions. Conclusions: Cardiovascular and muscular deconditioning had no effect on the heat production and heat loss responses. Due to the signifi cant reduction in the mass of the muscles in the lower limbs, concomitant with no change in heat production, we conclude that leg muscles do not play a signifi cant role in shivering thermogenesis