Experiments on the Magnetism of Sc Implanted into Metals

The study of dilute Sc impurities in either heavier d-transition metals or in alkali metal hosts is difficult due to their limited solubility; however, the large host-impurity mismatch in these systems makes them particularly interesting in terms of local electronic structure. One way to overcome the solubility problem is implantation into the desired host; in particular, using recoil implantation following heavy-ion nuclear reactions, deep implantation into practically any host can be achieved. Here, we compare the implantation of ⁴³Sc into Cs, studied in situ by the in-beam TDPAD method [1], with the implantation of ^44m Sc into Fe, studied by low-temperature nuclear orientation (LTNO) and related techniques (NMRON, thermal cycling) [2].     

Synthesis of polyquinanes via bicyclo [2.1.0] pentane intermediates. An easy access to optically pure diquinane alcohols of known absolute configuration.

The resolution of the cyclobutenic ester 1 using chiral lactols is described. After a stereospecific reaction sequence (cyclopropanation followed by an acidic solvolysis), the enantiomerically pure diquinanes 10 are obtained.     

A shallow buried-layer formation technique utilizing diffusion fromimplanted polysilicon layer

A shallow buried-layer (0.25~0.50 μm) formation technique utilizing diffusion from an arsenic-implanted polysilicon layer is discussed. The polysilicon layer is removed by converting it into an oxide layer and wet etching the oxide layer. Vertical n-p-n bipolar transistors are fabricated on epitaxial layers deposited on buried layers formed utilizing this technique. The transistor characteristics indicate that high-quality epitaxial layers can be grown on these buried layers. Using this technique, a buried layer with a sheet resistance of 28 Ω/□ and a junction depth of ~0.4 μm was obtained (prior to the epitaxial growth)     

Analysis of noise properties of a class of exact methods of inverting the 2-D exponential radon transform [SPECT application

A general approach that the authors proposed elsewhere reveals the intrinsic relationship among methods for inversion of the 2-D exponential Radon transform described by Bellini et al. (1979), by Tretiak and Metz (1980), by Hawkins et al. (1988), and by Inouye et al. (1989). Moreover, the authors' approach provides an infinite class of linear methods for inverting the 2-D exponential Radon transform. In the work reported here, the authors systematically investigated the noise characteristics of the methods in this class, obtaining analytical forms for the autocovariance and the variance of the images reconstructed by use of various methods. The noise properties of a new "quasi-optimal" method were then compared theoretically to those of other methods of the class. The authors' analysis demonstrates that the quasi-optimal method achieves smaller global variance in the reconstructed images than do the other methods of the class. Extensive numerical simulation studies confirm this prediction.     

Polyimide-based microfluidic devices

This paper describes the development of polyimide-based microfluidic devices. A layer transfer and lamination technique is used to fabricate flexible microfluidic channels in various shapes and with a wide range of dimensions. High bond strengths can be achieved by cure cycle adaptation and surface treatment of the polyimide layers prior to bonding. The polyimide microchannels can be combined with metallization layers to fabricate electrodes inside and outside channels. The resulting devices can be used for flexible fluidic and electrical connectors, implantable fluid delivery devices, microelectrodes with embedded fluidic channels, chip-based flow cytometry and for a great variety of other applications in medical, chemical or biological research.     

Investigation of argon ion bombarded RexSi1-x thin film composites by XPS, SEM and AES

The electronic structure of argon ion bombarded Re_xSi_1-x films (～ 100 nm) were investigated by X-ray photoelectron spectroscopy. Argon ion bombardment leads to preferential sputtering of the silicon atoms and produces an subsurface rhenium enrichment. Changes in the core level binding energies and in the valence band structure have been studied as the rhenium concentration in the composites varies between 0 ≤ x ≤ 1 through the metal-semiconductor transition at x ≈ 0.32. The data of the multiplex spectra were subjected to factor analysis in order to determine the relevant components of the ion bombarded metal-silicon system. Four principal components are extracted and are proposed as the pure elements, a rhenium-rich phase and a component near the ReSi₂ stoichiometry. Complementary investigations by SEM and AES provide further proof of the phase assignment in the rhenium-rich component. The silicon-rich component being in composition close to the metal-semiconductor transition can be correlated to the ReSi₂ compound.     

Pulse radiolysis studies of styrene

We have applied the pulse radiolysis technique of studying short-lived, radiation-produced intermediates to a study of pure, dry liquid styrene. We have observed at least three distinct species. The most rapidly decaying species (τ1/2 = 4 μsec., λ_max ≈ 370 mμ) exhibits an apparent first-order decay which is slowed down in the presence of dry oxygen, occurs too rapidly to be measured in the presence of water, and has a temperature coefficient of approximately 1 kcal./mole between 25 and 45°C. We have tentatively identified the species as the styryl anion with a G value for formation of approximately 0.15. A second species (τ1/2 = 220 μsec. λ_max ≈ 320–330 mμ) exhibits a first-order decay which appears to be independent of oxygen and water. From its spectrum, we have tentatively identified it as the styryl radical. The third species (λ_max ≈ 310 and 320 mμ) is relatively stable in the dark, but is radily photolyzed by the analyzing light of the usual experimental set-up for pulse radiolysis studies. The formation of this species appears to be independent of the water and oxygen content of the styrene.