The δ-Al2O3 (Saffil) fibre degradation during infiltration with MgLi alloy

The chemical and phase transformations of -Al₂O₃ (Saffil) fibres during their infiltration with Mg-8 wt% Li were studied by scanning and transmission electron microscopy, Auger electron spectroscopy, secondary ion mass spectrometry and X-ray diffraction methods. The infiltration experiments were carried out in autoclave under argon pressure at temperatures of 883–908 K and contact times of 4–30 s as well as at 918 K/420 s. During the course of infiltration, lithium penetrates the Saffil fibres and this process is accompanied by the gradual transformation of the tetragonal -Al₂O₃ lattice towards the cubic spinel LiAl₅O₈ compound, where part of the Li⁺ ions is probably substituted by Mg²⁺ No remarkable interfacial zone at the fibre/matrix interface was observed; however, the Saffil fibres became brittle which had been manifested by the occurrence of fragmentation on the metallographically treated fibre cross-sections. The tensile strength (maximum 220 MPa) of the corresponding metal matrix composite clearly decreased with increased infiltration time.     

Conducting Psychological Research in Medical Settings: Challenges, Limitations, and Recommendations for Effectiveness Research.

Efficacy research is insufficient and ineffective in changing practice, despite a large supporting psychotherapy efficacy literature. Concurrently, demand for supporting data and the burden on everyday practice for generating these data is increasing. The disconnect between efficacy and effectiveness is due to a lack of conceptual and methodological tools for testing efficacious procedures in real-world settings, particularly medical contexts. This article articulates the position that effectiveness studies pose more complex questions that require an alteration of conceptual and methodological frames of reference in order to make behavioral services available to the broadest patient base. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Estimates of N2O and CH4 fluxes from agricultural lands in various regions in Europe

According to the revised 1996 IPCC guidelines, several emission factors are needed to calculate national inventories of N₂O emissions from agriculture. To estimate the direct N₂O emissions from mineral soils, an emission factor of 0.0125 kg N₂O-N per kg N applied is currently being used. From recent literature data it was clearly shown that real N₂O emissions could differ substantially from this value. Based on the IPCC methodology an inventory of N₂O emission from agriculture in Europe (EU-15) has been made. In 1996, the N₂O emission was estimated at 672 Gg N₂O-N. The N₂O emission per country varied between 10 and 177 Gg N₂O-N. The N₂O emission per ha agricultural land in the various countries varied between 1.7 and 14.2 kg N₂O-N ha⁻¹. Highest N₂O emissions per ha were found in countries with a high agricultural intensity, such as the Netherlands, Belgium-Luxembourg, Denmark and Germany. Agricultural soils are a sink for atmospheric methane. An oxidation capacity of 2.5 and 1.5 kg CH₄ ha⁻¹ yr⁻¹ was put forward for grasslands and arable land, respectively. Based on land use data of 1993, the CH₄ sink of agricultural lands in EU-15 was estimated at 303.5 Gg CH₄. In general, it could be concluded that N₂O emissions from soils (327 Tg CO₂ equivalents) are far more important than its sink function for CH₄ (6.3 Tg CO₂ equivalents). This revised version was published online in August 2006 with corrections to the Cover Date.     

Er+ medium energy ion implantation into lithium niobate

Erbium-doped lithium niobate (Er:LiNbO₃) is a prospective photonics component, operating at 1.5 μm, which could find its use chiefly as an optical amplifier or waveguide laser. In this study, we have focused on the properties of the optically active Er:LiNbO₃ layers, which are fabricated by medium energy ion implantation under various experimental conditions. Erbium ions were implanted at energies of 330 and 500 keV with fluences of 1.0 × 10¹⁵, 2.5 × 10¹⁵ and 1.0 × 10¹⁶ cm^?2 into LiNbO₃ single-crystalline cuts of various orientations. The as-implanted samples were annealed in air at 350 °C for 5 h. The depth distribution and diffusion profiles of the implanted Er were measured by Rutherford Backscattering Spectroscopy (RBS) using 2 MeV He⁺ ions. The projected range R_P and projected range straggling ΔR_P were calculated employing the SRIM code. The damage distribution and structural changes were described using the RBS/channelling method. Changes of the lithium concentration depth distribution were studied by Neutron Depth Profiling (NDP). The photoluminescence spectra of the samples were measured to determine whether the emission was in the desired region of 1.5 μm. The obtained data made it possible to reveal the relations between the structural changes of erbium-implanted lithium niobate and its luminescence properties important for photonics applications.     

Effectiveness of daylighting design and occupant visual satisfaction in a LEED Gold laboratory building

Using daylight as primary light source has been widely recognized as an important strategy to reduce building energy demand and enhance indoor environment quality. However, to design and operate a building to make full use of daylight, which is a dynamic light source, to meet diverse occupant needs remains a challenge. This paper reports a post-occupancy study of the visual environment in a laboratory building on a university campus, and puts a spotlight on the building occupants as it examines the effectiveness of the daylighting design and systems integration in creating a visual environment to support occupant comfort and satisfaction while reducing artificial lighting demand. Results show generally high satisfaction with daylit work environment and positive effect of the horizontal shading strategy. Issues about the integration between daylighting and electric lighting systems and level of occupant control are identified and discussed for improving the effectiveness of daylighting and enhancing the quality of the visual environment in the building of study. A multiple-tool methodology is developed and tested, which included occupant surveys, interviews, illuminance measurements, continuous data loggers, fisheye-lens camera and glare-identifying software, and documentation of spatial settings, systems features, and user behavior.     

Minimum length of a single-mode fiber spatial filter

Using the concept of leaky modes, we derive the minimum length of a single-mode fiber required to act as a spatial-mode filter of given quality. The degree of filter action is defined by the ratio of power carried by the fundamental mode to that carried by the leaky modes.     

Optical properties and quantum efficiency of thin-film alkali halides in the far ultraviolet

The optical constants of thin films of CsI, KI, and KBr and the quantum efficiency (QE) of planar photocathodes made with these alkali halides in the 53.6-174.4-nm spectral range are presented. The optical constants were obtained from measurements of the reflectance as a function of incidence angle. The effect of film heating and exposure to UV irradiation on the optical properties and on the QE of the three alkali halides was investigated. KBr was found to be the most stable material for both heating and UV irradiation. KI appeared to be close to temperature stable, whereas UV exposure affected its optical constants. CsI optical constants changed after 420 K heating and after UV exposure. The changes in the optical constants were related to the QE changes, and a certain correlation between both variations was determined. However, it was also demonstrated that the QE changes cannot be explained solely by the changes in optical constants.     

Measurements on a 215-GHz subharmonically pumped waveguide mixerusing planar back-to-back air-bridge Schottky diodes

This paper presents design and performance data for a 215-GHz subharmonically pumped waveguide mixer using an antiparallel-pair of planar air-bridge-type GaAs Schottky-barrier diodes. The waveguide design is a prototype for a 640-GHz system and uses split-block rectangular waveguide with a 2:1 width-to-height ratio throughout. The measured mixer noise and conversion loss are below that of the best reported whisker contacted or planar-diode mixers using the subharmonic-pump configuration at this frequency. In addition, the required local oscillator power is as low as 3 mW for the unbiased diode pair, and greater than 34 dB of LO noise suppression is observed. Separate sideband calibration, using a Fabry-Perot filter, indicates that the mixer can be tuned for true double sideband response at an intermediate frequency of 1.5 GHz. Microwave scale model measurements of the waveguide mount impedances are combined with a mixer nonlinear analysis computer program to predict the mixer performance as a function of anode diameter, anode finger inductance, and pad-to-pad fringing capacitance. The computed results are in qualitative agreement with measurements, and indicate that careful optimization of all three diode parameters is necessary to significantly improve the mixer performance     

Zum Einfluß der Gefügeausbildung auf das Korrosionsverhalten von Aluminiumbronzen in Kochsalzlösung

Influence of the structure on the corrosion behaviour of aluminium bronzes in sodium chloride solution The influecne of various structural components and their distribution on the corrosion behaviour of binary and complex aluminium bronzes (cast INOXYDA alloys) in a 3% solution of sodium chloride has been investigated qualitatively and quantitatively. Corrosion tests were carried out over a period of 850 h and are interpreted on the basis of single phase properties. The corrosion resistacne of binary and INOXYDA 3 type alloys is markedly decreased if even small amounts of y₂ phase are precipitated in a continuous manner. The occurance of this constituent causes an intense and dangereous dealuminisation reaction. The eutectoid mixture (α + y₂) is always less corrosion resistant than corresponding martensitic structures. While the corrosion behaviour of these alloys is strongly influenced by heat treatment a far less pronounced effect is observed with alloys containing Fe and Ni (type INOXYDA 53 or 90). This is directly related to the fact that precipitation of y₂ is prevented by the addition of Fe and especially of Ni. Such alloys are mainly composed of Ni. Such alloys are mainly composed of α and passive Fe- and Ni-rich K phase. If retained martensite or y₂ are present in addition to the mentioned phases (e.g. in the as cast condition) corrosion resistance is decreased. Appropriate heat treatment results in plain (α + K) structures while simultaneously segregations at α/K grain boundaries disappear and corrosion resistance is improved.     

Modeling kinetic processes controlling hydrogen and acetate concentrations in an aquifer-derived microcosm

Groundwater contaminants may degrade via fermentation to intermediate species, which are subsequently consumed by terminal electron-accepting processes (TEAPs). A numerical model of an aquifer-derived laboratory microcosm is developed to simulate the dynamic behavior of fermentation and respiration in groundwater by coupling microbial growth and substrate utilization kinetics with a formulation that also includes aqueous speciation and other geochemical reactions including surface complexation, mineral dissolution, and precipitation. The model is used to test approaches that currently make use of H2(aq) to diagnose prevalent TEAPs in groundwater. Competition between TEAPs is integral to the conceptual model of the simulation, and the results indicate that competitive exclusion is significant but with some overlap found in the temporal sequence of TEAPs. Steady-state H2(aq) concentrations observed during different TEAPs do not differ significantly. The results are not consistent with previous applications of the partial equilibrium approach since most TEAP redox pairs exhibit free energies that suggest a particular process is able to proceed, yet observations here show that this process does not proceed.