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Materials commonly involve microstructure. Clay is a microinhomogeneous material with nanoscale microstructure. Key issues to understand the behavior of such a finely microinhomogeneous material are as follows: the microstructure is characterized in detail, the local distribution of material properties is identified by experiment or simulation, and the microscale characteristics are related to the macroscale behavior by a seamless manner. For characterizing a microstructure of bentonite, we introduce a conforcal laser scanning microscope (CLSM) together with SEM. By CLSM we can specify a 3D configuration under atmospheric condition. Properties of water-saturated bentonite are mainly controlled by hydrated montmorillonite, which is the major clay mineral of bentonite. Smectite minerals including montmorillonite are extremely fine and poorly crystallized, so it is difficult to determine the properties by experiment. We inquire into the physicochemical properties by a molecular dynamics simulation method. Then, we develop a multiscale homogenization method to extend the microscopic characteristics to the macroscopic behavior. We show numerical examples of a diffusion problem. [ABSTRACT FROM AUTHOR]

Optical single-sideband (SSB) modulation is theoretically realised by applying two modulation signals with a 90° phase difference to the dual-electrode type electro-optic (EO) modulator. A branch-line coupler (BC) as the microwave 90° hybrid was directly prepared on the EO modulator substrate, LiNbO3, to create two modulation signals from a single input signal. Output ports of the BC were connected to the modulation electrodes on the substrate. Thereby, an EO optical SSB modulator was realised with a single-tip and a small-sized configuration. The SSB modulator was designed and fabricated for around 10 GHz modulation frequency and 1550 nm light wavelength. The optical SSB modulation operation with a sideband suppression ratio of more than 20 dB was confirmed by the experiment. [ABSTRACT FROM AUTHOR]

Crack-free GaN epilayers were grown with the mask less epitaxial lateral overgrowth (ELO) on Si substrates with various thicknesses of 3C-SiC intermediate layers. The defects in 3C-SiC and GaN layers were studied to reveal the impact of 3C-SiC intermediate layer on GaN epitaxy. In the 3C-SiC layer, a gradient density of stacking faults (SFs) was observed along the growth direction. Most of the SFs locate in the first 500-nm-thick 3C-SiC layer. Thanks to the maskless ELO method, the defects in under layer could not extend into GaN layer, even grown on a 100-nm-thick 3C-SiC layer with high density. The threading dislocation density in GaN varies in the range of ~(1±0.3)x109 cm-2. Investigation of GaN nucleation indicated a correlation between GaN quality and surface roughness of 3C-SiC layers. Meanwhile, the surface morphology of 3C-SiC is affected by double positioning domains, which revealed as a result of strain relaxation process during growth on Si substrate. [ABSTRACT FROM AUTHOR]

PET-imaging of the sigma receptors is very helpful to understand processes, e.g., several central nervous system (CNS)-diseases in which the sigma receptors are involved. The [18F]fluoroethylated analogs of SA4503 and SA5845 ([18F]FE-SA4503 and [18F]FE-SA5845) were evaluated in conscious monkeys to estimate its suitability for human application for PET. Conscious monkeys (Macaca Mulatta) were either scanned with [18F]FE-SA4503 or [18F]FE-SA5845 (n = 3 for both groups, 220–802 MBq). After a dynamic study of 120 min, radioactivity was displaced by intravenous (i.v.) injection of haloperidol (1 mg/kg). One month later the same set of three monkeys were scanned with [18F]FE-SA4503 for 120 min and “cold” SA4503 (1 mg/kg) was infused to displace the radioactivity, and the other three monkeys were pretreated with haloperidol (1 mg/kg) before the 120-min PET-scan with [18F]FE-SA5845. Cortical areas (cingulate, frontal, occipital, parietal, temporal), striatum, and thalamus showed high radioactivity uptake. Infusion of haloperidol displaced the radioactivity levels of the two radioligands. The same effect was found for [18F]FE-SA4503 after SA4503 displacement. Pretreatment with haloperidol blocked the [18F]FE-SA5845 binding to give PET-images with low and uniform uptake in the brain. The findings demonstrated the reversible binding of the two radioligands. Metabolite analysis showed that 14% and 23% parent compound of [18F]FE-SA5845 and [18F]FE-SA4503, respectively, at 120 min postinjection was present in plasma. Kinetic analysis showed that the binding potential of [18F]FE-SA5845 was higher in all brain regions than that of [18F]FE-SA4503 (4.75–8.79 vs. 1.65–4.04). The highest binding potential was found in the hippocampus, followed by the cortical regions, thalamus, cerebellar hemisphere, striatum and vermis. Both [18F]FE-SA compounds bound specifically to cerebral sigma receptors of the monkey and have potential for mapping sigma receptors in the human brain. Synapse 52:29–37, 2004. © 2004 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]