Thermal resistivity of quaternary solid solutions InGaSbAs and GaAlSbAs lattice-matched to GaSb

Measurement of the thermal resistivity of the materials InGaSbAs and GaAlSbAs is reported. These materials have thermal resistivities of three to four times that of the GaSb substrate to which they were lattice matched. This makes them particularly suitable for use as the active medium in semiconductor light sources.<>     

Spirituosen und Essig

Ohne Zusammenfassung     

Fabrication of LIGA-Acceleration Sensors by Aligned Molding

 A technology for the fabrication of movable LIGA-Microstructures by molding was developed, which enables the cheaper production of e.g. LIGA-Acceleration Sensors [1]. For this purpose an aligned molding process had to be developed. The realized experimental setup consists of two subsystems, the molding machine and the alignment arrangement [2]. After aligning a substrate it is transported into the molding machine. An effective and extremely precise dimension translation system is required. Although during molding temperature changes appear and high forces are applied, the dimension stability during the molding process has to be guaranteed. The presented system and setup deals successfully with these conditions. An alignment quality of ±10 μm is realized. Using the aligned molding technology temperature compensated LIGA-acceleration sensors [1] were fabricated. The proper function of the sensors was demonstrated. Received: 30 October 1995/Accepted: 11 December 1995     

Relative efficiency of tumor cell killing in vitro by two enzyme-prodrug systems delivered by identical adenovirus vectors

Enzyme-prodrug therapy for the treatment of cancer is an experimental procedure that is under intensive investigation. However, the relative merits of the various systems for use under specific conditions are still being determined. We have compared the efficacy of cell killing by the herpesvirus thymidine kinase (HSVTK)/ganciclovir and the purine nucleoside phosphorylase (PNP)/9-(beta-M-2-deoxy-erythropentofuranosyl)6-methylpurine enzyme/prodrug systems. These were chosen because of their differential dependence on DNA replication for their mechanism of action. The HSVTK and PNP genes, expressed from the identical prostate-specific antigen promoter, were transduced into human prostate and breast cancers cells using the same human adenovirus vector. The kinetics of cell killing in the presence of the respective prodrugs was monitored using a nondestructive assay that measured total cell bioactivity. The PNP/9-(beta-D-2-deoxy-erythropentofuranosyl)6-methylpurine system was clearly superior in its ability to cause cell death in vitro. Cells were killed in about half the time and at a 5-10-fold lower input of virus relative to the HSVTK/ganciclovir system. The PNP system may offer advantages for the treatment of slow-growing tumors in which the daily proliferative rate is low or in situations in which gene delivery or expression is inefficient.     

Mössbauer effect on the spinel oxide FeCoVO4

The valence states in the spinel FeCoVO₄ are studied. After recalling the crystalline structure and the magnetic properties, the different possibilities for valence states of iron and vanadium are discussed. Mossbauer measurements at 342 K give for iron an isomer shift relative to metallic iron I_Fe = (0.34 ± 0.02)mm/sec and a quadrupole splitting $\text{1}\text{4}\text{e}{}^2\text{qQ}\text{= (0.17 ± 0.02)}\text{mm}\text{/}\text{sec}$. Mössbauer spectra at low temperatures are investigated. The formula (Co^II) {Fe^IIIV^III}O₄ is the most probable.     

Spatiotemporal aspects of real-time PM(2.5): low- and middle-income neighborhoods in Bangalore, India

We measured outdoor fine particulate matter (PM(2.5)) concentrations in a low- and a nearby middle-income neighborhood in Bangalore, India. Each neighborhood included sampling locations near and not near a major road. One-minute average concentrations were recorded for 168 days during September 2008 to May 2009 using a gravimetric-corrected nephelometer. We also measured wind speed and direction, and PM(2.5) concentration as a function of distance from road. Average concentrations are 21-46% higher in the low- than in the middle-income neighborhood, and exhibit differing spatiotemporal patterns. For example, in the middle-income neighborhood, median concentrations are higher near-road than not near-road (56 versus 50 μg m(-3)); in the low-income neighborhood, the reverse holds (68 μg m(-3) near-road, 74 μg m(-3) not near-road), likely because of within-neighborhood residential emissions (e.g., cooking; trash combustion). A moving-average subtraction method used to infer local- versus urban-scale emissions confirms that local emissions are greater in the low-income neighborhood than in the middle-income neighborhood; however, relative contributions from local sources vary by time-of-day. Real-time relative humidity correction factors are important for accurately interpreting real-time nephelometer data.     

Anderson accelerated fixed-stress splitting schemes for consolidation of unsaturated porous media

In this paper, we study the robust linearization of nonlinear poromechanics of unsaturated materials. The model of interest couples the Richards equation with linear elasticity equations, generalizing the classical Biot equations. In practice a monolithic solver is not always available, defining the requirement for a linearization scheme to allow the use of separate simulators. It is not met by the classical Newton method. We propose three different linearization schemes incorporating the fixed-stress splitting scheme, coupled with an L-scheme, Modified Picard and Newton linearization of the flow equations. All schemes allow the efficient and robust decoupling of mechanics and flow equations. In particular, the simplest scheme, the Fixed-Stress-L-scheme, employs solely constant diagonal stabilization, has low cost per iteration, and is very robust. Under mild, physical assumptions, it is theoretically shown to be a contraction. Due to possible break-down or slow convergence of all considered splitting schemes, Anderson acceleration is applied as post-processing. Based on a special case, we justify theoretically the general ability of the Anderson acceleration to effectively accelerate convergence and stabilize the underlying scheme, allowing even non-contractive fixed-point iterations to converge. To our knowledge, this is the first theoretical indication of this kind. Theoretical findings are confirmed by numerical results. In particular, Anderson acceleration has been demonstrated to be very effective for the considered Picard-type methods. Finally, the Fixed-Stress-Newton scheme combined with Anderson acceleration shows the best performance among the splitting schemes.