Some block- and trellis-coded modulations for the Rayleigh fadingchannel

The error performance of a modulation code over a channel depends on several distance parameters and the path multiplicity of the code. For the AWGN channel, the error performance of a modulation code depends mainly on its minimum squared Euclidean distance and path multiplicity. For the Rayleigh fading channel, however, the error performance of a modulation code depends strongly on its minimum symbol distance, minimum product distance, and path multiplicity. It depends on the minimum squared Euclidean distance in a lesser degree. This paper is concerned with the construction of block and trellis MPSK modulation codes for the Rayleigh fading channel. In each construction, the distance parameters are chosen to achieve good error performance with reduced decoding complexity     

Phosphoinositide 3-kinase regulates phospholipase Cgamma-mediated calcium signaling

It has been demonstrated that the lipid products of the phosphoinositide 3-kinase (PI3K) can associate with the Src homology 2 (SH2) domains of specific signaling molecules and modify their actions. In the current experiments, phosphatidylinositol 3,4, 5-trisphosphate (PtdIns-3,4,5-P3) was found to bind to the C-terminal SH2 domain of phospholipase Cgamma (PLCgamma) with an apparent Kd of 2.4 microM and to displace the C-terminal SH2 domain from the activated platelet-derived growth factor receptor (PDGFR). To investigate the in vivo relevance of this observation, intracellular inositol trisphosphate (IP3) generation and calcium release were examined in HepG2 cells expressing a series of PDGFR mutants that activate PLCgamma with or without receptor association with PI3K. Coactivation of PLCgamma and PI3K resulted in an approximately 40% increase in both intracellular IP3 generation and intracellular calcium release as compared with selective activation of PLCgamma. Similarly, the addition of wortmannin or LY294002 to cells expressing the wild-type PDGFR inhibited the release of intracellular calcium. Thus, generation of PtdIns-3,4,5-P3 by receptor-associated PI3K causes an increase in IP3 production and intracellular calcium release, potentially via enhanced PtdIns-4, 5-P2 substrate availability due to PtdIns-3,4,5-P3-mediated recruitment of PLCgamma to the lipid bilayer.     

Detection of microfracture processes in composite laminates by thermo-acoustic emission

The damage process in composite laminates subjected to cryogenic cooling was monitored employing a thermo-acoustic emission (AE) technique. The thermo-AE signals processed with a short-time Fourier transform could be classified into three different types which were correlated with individual microfracture processes. In the initial stage of cryogenic cooling, very strong AE signals with low and high frequency bands were dominantly detected showing that large cracks accompanying fiber breakages were developed mainly. With an increase in the cooling time, weak emissions with low frequency bands became prevalent indicating the propagation of microfractures in the matrix and/or fiber-matrix interface. Similar types of AE signals, however, having weak amplitudes, were also observed for the cryogenically-treated specimens during thermal heating and cooling load cycles. Thus, analysis of thermo-AE behavior through the thermal load cycle led to the nondestructive evaluation for the cryogenic damage of composites.     

A partially insulated field-effect transistor (PiFET) as a candidate for scaled transistors

Highly manufacturable partially insulated field-effect transistors (PiFETs) were fabricated by using Si-SiGe epitaxial growth and selective SiGe etch process. Owing to these technologies, pseudo-silicon-on-insulator (SOI) structures, partially insulating oxide (PiOX) under source/drain (PUSD) and PiOX under channel (PUC), could be easily realized with excellent structural and process advantages. We are demonstrating their preliminary characteristics and properties. Especially, in the PUSD PiFET, junction capacitance, leakage current, and DIBL in bulk devices could be reduced and the floating body problem in SOI devices was also cleared without any area penalty. Thus, this PiFET structure can be a promising candidate for the future DRAM cell transistor.     

Reaction of TiO2-Al-C in the Combustion Synthesis of TiC-Al2O3 Composite

Reaction mechanisms and the thermal structure in the reaction zone during the combustion of TiO₂, Al, and C to form TiC-Al₂O₃ composite were studied. The reaction between each component was studied and the combustion wave structure and real-time temperature profile were analyzed. Titanium aluminide species, present in the aluminothermic reduction of TiO₂, did not occur in the presence of C, because of the high thermodynamic stability of TiC. The activation energies of the exothermic reaction in the 3TiO₂-4Al-3C system were determined by DSC analysis. This suggests that the combustion reaction is mainly controlled by carbon diffusion through solid TiC. The combustion wave was observed to propagate in an unstable mode. The temperature profiles in the reaction zone were of the sawtooth type and the products were of layered structure.     

Excitation mechanisms of multiple Er3+ sites in Er-implanted GaN

Site-selective photoluminescence (PL) and photoluminescence excitation (PLE) spectroscopies carried out at 6K on the ∼1540 nm ⁴I_13/2→⁴I_15/2 emissions of Er³⁺ in Er-implanted GaN have revealed the existence of four different Er³⁺ sites and associated PL spectra in this semiconductor. Three of these four sites are excited by below-gap, impurity- or defect-related absorption bands, with subsequent nonradiative energy transfer to the Er³⁺ 4f electrons; a fourth site is excited by direct Er³⁺ 4f shell absorption. PLE spectra obtained by selectively detecting Er³⁺ PL from each of the three sites pumped by broad below-gap absorption bands are compared with the PLE spectra of broad PL bands attributed to implantation damage-induced defects in the Er-implanted GaN. This comparison enables us to distinguish broad-band, below-gap optical excitation processes for Er³⁺ emission that are attributable to (1) absorption due to implantation damage-induced defects; (2) absorption due to defects or impurities characteristic of the as-grown GaN film; and (3) an Er-specific absorption band just below the band gap which may involve the formation of an Er-related isoelectronic trap. The two sites excited by impurity-or defect-related absorption bands are also strongly pumped by above-gap excitation, while the sites pumped by the Er-related trap and direct 4f shell absorption are not. This observation indicates that excitation of Er³⁺ luminescence in crystalline semiconductor hosts by either optical or electrical injection of electron-hole pairs is dominated by trap-mediated carrier capture and energy transfer processes. These trap-mediated processes may also control the thermal quenching of Er³⁺ emission in semiconductors.     

Testing Hypotheses Regarding the Causes of Comorbidity: Examining the Underlying Deficits of Comorbid Disorders.

The authors examined the validity of a method commonly used to test alternative hypotheses regarding the causes of comorbidity: the examination of underlying deficits of comorbid disorders. The authors simulated data in which the true causes of comorbidity were known, then compared the patterns of underlying deficits of the comorbid disorders found in the simulated data with the predicted results. The method of examining the underlying deficits of comorbid disorders could distinguish between several comorbidity models, including those that could not be distinguished well using other methods. The ability to distinguish the correct model decreased as the sample size and the correlation between the underlying deficits and the symptom scores decreased, suggesting that the issue of power should be considered carefully. (PsycINFO Database Record (c) 2010 APA, all rights reserved)