Advanced core technology: Key to subsonic propulsion benefits

A study was conducted to identify the potential performance benefits and key technology drivers associated with advanced cores for subsonic high bypass turbofan engines. Investigated first were the individual sensitivities of varying compressor efficiency, pressure ratio and bleed (turbine cooling); combustor pressure recovery; and turbine efficiency and inlet temperature on thermal efficiency and core specific power output. Then, engine cycle and mission performance benefits were determined for systems incorporating all potentially achievable technology advancements. The individual thermodynamic sensitivities are shown over a range of turbine temperatures (at cruise) from 2900 to 3500 R and for both constant (current technology) and optimum (maximum thermal efficiency) overall pressure ratios. It is seen that no single parameter alone will provide a large increase in core thermal efficiency, which is the thermodynamic parameter of most concern for transport propulsion. However, when all potentially achievable advancements are considered, there occurs a synergism that produces significant cycle and mission performance benefits. The nature of these benefits are presented along with the technology challenges

Brain edema : a valid endpoint for measuring hepatic encephalopathy?

Hepatic encephalopathy (HE) is a major complication of liver failure/disease which frequently develops during the progression of end-stage liver disease. This metabolic neuropsychiatric syndrome involves a spectrum of symptoms, including cognition impairment, attention deficits and motor dysfunction which eventually can progress to coma and death. Pathologically, HE is characterized by swelling of the astrocytes which consequently leads to brain edema, a common feature found in patients with acute liver failure (ALF) as well as in cirrhotic patients suffering from HE. The pathogenic factors involved in the onset of astrocyte swelling and brain edema in HE are unresolved. However, the role of astrocyte swelling/brain edema in the development of HE remains ambiguous and therefore measuring brain edema as an endpoint to evaluate HE is questioned. The following review will determine the effect of astrocyte swelling and brain edema on neurological function, discuss the various possible techniques to measure brain edema and lastly to propose a number of neurobehavioral tests to evaluate HE

Design and characterization of optical-THz phase-matched traveling-wave photomixers

Design and characterization of optical-THz phase-matched traveling-wave photomixers for difference-frequency generation of THz waves are presented. A de-biased coplanar stripline fabricated on low-temperature-grown GaAs is illuminated by two non-collinear laser beams which generate moving interference fringes that are accompanied by THz waves. By tuning the offset angle between the two laser beams, the velocity of the interference fringe can be matched to the phase velocity of the THz wave in the coplanar stripline. The generated THz waves are radiated into free space by the antenna at the termination of the stripline. Enhancement of the output power was clearly observed when the phase-matching condition was satisfied. The output power spectrum has a 3-dB bandwidth of 2 THz and rolls off as ~9 dB/Oct which is determined by the frequency dependent attenuation in the stripline, while the bandwidth of conventional photomixer design has the limitation by the RC time constant due to the electrode capacitance. The device can handle the laser power of over 380 mW, which is 5 times higher than the maximum power handring capability of conventional small area devices. The results show that the traveling-wave photomixers have the potential to surpass small area designs, especially at higher frequencies over I THz, owing to their great thermal dissipation capability and capacitance-free wide bandwidth

A traveling-wave THz photomixer based on angle-tuned phase matching

A traveling-wave THz photomixer based on a free-space optical-THz phase-matching scheme is proposed. A dc-biased coplanar strip line fabricated on low-temperature-grown GaAs serves as the active area of the device, and is illuminated by two noncollinear laser beams which generate interference fringes that are accompanied by THz waves. The device with the laser-power-handling capability over 300 mW and a 3-dB bandwidth of 1.8 THz was experimentally demonstrated. The results show that traveling-wave photomixers have the potential to surpass small-area designs

Land management for increased flood resilience

Natural Flood Management (NFM) (e.g. restoring watercourses, riparian tree planting, washland and wetland creation) is a core component of flood risk management strategies in Scotland. However little is known of its potential impact on the farming and land management communities, individual farm businesses, or the socioeconomic impacts and perceptions of its potential wide-spread introduction. To support policy implementation, information is required on land managers’ willingness to implement NFM, and to be able to relate willingness to generic farm characteristics (farming systems, land use types, geographical location), different types and locations of NFM measures, and to farm economics.The main objectives of the project are to undertake:1. A large scale survey of farmers’ attitudes to NFM and to the use of potential policy instruments to promote its uptake and delivery; and2. Farm-scale economic analyses of the impact of NFM measures under different scenarios

The Ucsd/Keck Damped Lya Abundance Database: A Decade of High Resolution Spectroscopy

We publish the Keck/HIRES and Keck/ESI spectra that we have obtained during the first 10 years of Keck observatory operations. Our full sample includes 42 HIRES spectra and 39 ESI spectra along 65 unique sightlines providing abundance measurements on ~85 damped Lya systems. The normalized data can be downloaded from the journal or from our supporting website: http://www.ucolick.org/~xavier/DLA/. The database includes all of the sightlines that have been included in our papers on the chemical abundances, kinematics, and metallicities of the damped Lya systems. This data has also been used to argue for variations in the fine-structure constant. We present new chemical abundance measurements for 10 damped Lya systems and a summary table of high-resolution metallicity measurements (including values from the literature) for 153 damped Lya systems at z>1.6. We caution, however, that this metallicity sample (and all previous ones) is biased to higher N(HI) values than a random sample.Comment: 55 pages, 11 figures. Accepted to ApJS. See http://www.ucolick.org/~xavier/DLA/ for the dat